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Accepted papers to appear in an upcoming issue

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Polarization-Dependent Laser Autofluorescence of the Protein Networks of Blood Plasma Films in the Task of Liver Pathology Differentiation

Vitaliy Prysyazhnyuk, Yuriy Ushenko, Olexander Dubolazov, Alexander Ushenko, and Vova Ushenko

Doc ID: 253120 Received 02 Nov 2015; Accepted 05 Feb 2016; Posted 05 Feb 2016  View: PDF

Abstract: Current research presents the results of investigation of diagnostic efficiency of laser polarization autofluorescence of the set ofendogenous fluorophores of blood plasma polycrystalline films in two spectral regions ( 0.5 − 0.53μm and 0.63− 0.67μm) under theexcitation of laser radiation with the wavelength of 0.405μm. A model of generalized optical anisotropy of protein networks of bloodplasma polycrystalline films is proposed for the purpose of definition of laser autofluorescence processes. It have been considered bothphase (linear birefringence and optical activity) and amplitude (linear and circular dichroisms) anisotropies. The interconnectionsbetween the optimal condition of probing beam polarization state and the efficiency of induction laser autofluorescence have been found.The statistic analysis of coordinate distributions of laser polarization autofluorescence intensities is suggested by means ofdetermination of the quantitative criteria (statistic moments of the 1st to the 4th order). The efficiency of laser polarizationautofluorescence of polycrystalline networks in the task of differentiation of nonalcoholic fatty liver disease and chronic hepatitis ofhuman liver has been analyzed.

Investigation of Plasmonic Properties of Graphene Multilayer Nano-Ribbon Waveguides

Yaser Hajati and Morteza Hajati

Doc ID: 254008 Received 16 Nov 2015; Accepted 05 Feb 2016; Posted 05 Feb 2016  View: PDF

Abstract: In this paper, we investigate the plasmonic properties of Graphene-Silica-Silicon (G-SiO2-Si) multilayer nano-ribbon waveguide in the mid-IR spectral range using the finite element method. Numerical results show that single-mode operation and modal cut-off properties of the G-SiO2-Si are highly sensitive to the width and chemical potential. In particular, we demonstrate that by properly tuning the geometric and material parameters of the spacer layer or by decreasing the operation frequency, the graphene-based waveguide exhibits a propagation length higher than that of its metal-based counterpart. We believe that this study will provide a valuable reference for designing ultra-compact and low-loss graphene-based novel plasmonic devices.

Vibration-immune high-sensitivity profilometer with the technique of composite interferometer

I-Jen Hsu, Yu-Kai Lin, Chun-Wei Chang, and Max Hou

Doc ID: 254600 Received 26 Nov 2015; Accepted 05 Feb 2016; Posted 05 Feb 2016  View: PDF

Abstract: A prototype of profilometer was built with the technique of composite interferometer for measurement of the distribution of both the amplitude and phase information of the surface of a material simultaneously. The composite interferometer was composed of a Michelson interferometer for measuring the surface profile of the sample, and a Mach-Zehnder interferometer for measuring the phase deviation caused by the scanning component and environmental perturbations. High-sensitivity surface profile can be obtained by use of the phase compensation mechanism through subtraction of the phases of the interferograms detected in the two interferometers. With the new design and improvement of robustness of the optical system, the measurement speed and accuracy were significantly improved. Furthermore, additional optical delay component results in a higher sensitivity of the interference signal. This prototype of vibration-immune profilometer was examined to have a displacement sensitivity of 0.64 nm.

Single-mode deep-UV light source at 191.7 nm by seventh harmonic generation of a high-power, Q-switched, injection-locked 1342 nm Nd:YVO₄ laser

Peter Koch, Jürgen Bartschke, and Johannes Lhuillier

Doc ID: 254542 Received 24 Nov 2015; Accepted 04 Feb 2016; Posted 04 Feb 2016  View: PDF

Abstract: A single-mode deep-UV laser at 191.7 nm is demonstrated by seventh harmonic generation of a single-mode 1342 nm Nd:YVO₄ laser. The fundamental laser is an injection-locked, Q-switched ring laser at 10 kHz pulse repetition frequency. By cascaded second harmonic and sum frequency generation, an average power of 0 mW at 191.7 nm is achieved. At 185 mW, the setup features a Gaussian beam with a beam quality factor of M² < 1.5. A pulse duration of 9 ns with pulse energy fluctuations of σ < 3 % is obtained. The long-term spectral width is approximately 240 MHz full width at half maximum, measured with a homemade scanning confocal Fabry-Perot interferometer. This work opens possibilities in fiber Bragg grating production, allowing the inscription of long gratings.

Angle-of-Incidence performance of random anti-reflection structures on curved surfaces

Courtney Taylor, Lynda Busse, Jesse Frantz, Jasbinder Sanghera, Ishwar Aggarwal, and Menelaos Poutous

Doc ID: 255050 Received 22 Dec 2015; Accepted 04 Feb 2016; Posted 04 Feb 2016  View: PDF

Abstract: Random anti-reflection structured surfaces (rARSS) have been reported to improve transmittance of optical-grade fused silica planar substrates, to values greater than 99%. These textures are fabricated directly on the substrates using reactive-ion etching techniques, and often result in transmitted spectra with no measurable interference effects (fringes) for a wide range of wavelengths. The inductively-coupled reactive ion plasma (ICP-RIE) used in the fabrication process to etch the rARSS is anisotropic, and thus well-suited for planar components. The improvement in spectral transmission has been found to be independent of optical incidence angles, for values from 0° to ±30°. Qualifying and quantifying the rARSS performance on curved substrates, such as convex lenses, is required to optimize the fabrication of the desired AR effect on optical-power elements. In this work, rARSS was fabricated on fused silica plano-convex lenses using a planar-substrate optimized ICP-RIE process, to maximize optical transmission in the range from 500 nm to 1100 nm. Results are presented from optical transmission tests of rARSS lenses, for both TE and TM incident polarizations, at a wavelength of 633nm, over a 70° full-field of view. These results suggest optimization of the fabrication process, to account for anisotropy, is not required, mainly due to the wide angle-of-incidence AR tolerance performance of the rARSS lenses.

High-performance visible blind ultraviolet photodetectors based on KTaO3 single crystal

Chen Ge, Jingting Yang, Kui-Juan Jin, HB Lu, and Guo-Zhen Yang

Doc ID: 255751 Received 14 Dec 2015; Accepted 04 Feb 2016; Posted 04 Feb 2016  View: PDF

Abstract: We report a visible-blind ultraviolet photoconductive detector with interdigitated electrodes based on KTaO3 (KTO) single crystals. Both the steady spectral responses and the transient photovoltaic measurements clearly exhibit a cutoff wavelength at 344 nm (~3.6 eV), in accordance with the bandgap of KTO. The KTO photodetectors show a low dark current ~1.5 pA at 20 V, and a high UV-to-visible rejection ratio with three orders of magnitude at room temperature. The quantum efficiency is 37.49% under 20 V bias, and the Detectivity D* of 3.85×1012 cm·Hz0.5/W, which is comparable to that of silicon photodetectors in the UV region. The present work offers appealing prospects for the application of KTO materials in high sensitive and low noise ultraviolet photodetectors. © 2015 Optical Society of America

Simultaneous second- and third- order spectral phase control of Ti:sapphire laser pulses using achromatic doublet prisms

Alex Fuerbach and Alexander Mueller

Doc ID: 256174 Received 21 Dec 2015; Accepted 04 Feb 2016; Posted 09 Feb 2016  View: PDF

Abstract: The standard technique commonly utilized to introduce large amounts of negative group delay dispersion (GDD) into the beam path of ultrashort laser pulses with low insertion losses is the use of a pair of prisms in a double pass configuration. However, one disadvantage of this approach is the unavoidable introduction of additional high-order spectral phase errors, most notably third-order dispersion (TOD) due to the characteristics of the refractive index of available optical materials. In this paper we provide an overview of the dispersive properties of over one hundred common types of optical glasses, either used as a bulk stretcher or in a prism compressor configuration. In addition, we present a novel method that enables independent control of GDD and TOD in a prism-only setup. The performance of different prism combinations is analyzed numerically and design guidelines are given.

Single-negative metamaterial periodic multilayer doped by magnetized cold plasma

Alireza Aghajamali and Chien-Jang Wu

Doc ID: 251034 Received 29 Sep 2015; Accepted 03 Feb 2016; Posted 03 Feb 2016  View: PDF

Abstract: This study theoretically investigates the properties of the defect mode in a one-dimensional defective single-negative photonic crystal containing magnetized cold plasma defect layer. The considered photonic crystal structure is made of epsilon-negative and mu-negative metamaterials. We investigate the defect mode as a function of the thickness and the electron density of the defect layer and the magnetic field. The results show that the thickness, the electron density, and the variations of the magnetic field affect the frequency of the defect mode. In addition, the shift trend in the defect mode is shown to rely on the polarization due to the presence of polarization-dependent magnetized cold plasma. The results lead to some new information concerning the designing of new types of tunable narrowband filters at microwave frequency.

Optical modeling of sunlight by using partially coherent sources in organic solar cells

Hamzeh Alaibakhsh and ghafar darvish

Doc ID: 255182 Received 04 Dec 2015; Accepted 03 Feb 2016; Posted 04 Feb 2016  View: PDF

Abstract: We investigate the effects of coherent and partially coherent sources in optical modeling of organic solar cells. Two different organic solar cells are investigated, one without substrate and the other with a millimeter-sized glass substrate. The coherent light absorption is calculated with rigorous coupled wave analysis. The result of this method is convolved with a distribution function to calculate the partially coherent light absorption. We propose a new formalism to accurately model sunlight as a set of partially coherent sources. Using partially coherent sources instead of coherent sources for simulations with sunlight results in smoother absorption spectrum but the change in the absorption efficiency is negligible.

Autofocusing system for SLM based maskless lithography

Sebastian Schlangen, Maximilian Ihme, Maik Rahlves, and Bernhard Roth

Doc ID: 255312 Received 07 Dec 2015; Accepted 03 Feb 2016; Posted 04 Feb 2016  View: PDF

Abstract: To produce diffractive or holographic structures in a photolithographic process, an optical projection system enabling structure resolution in the sub micrometer range is mandatory. To ensure that the optical focus of such a system lies on the substrate surface during the whole lithographic fabrication process, an autofocus system able to focus on a depth of field of a few hundred nanometers is usually required. In this work we developed an autofocus system for spatial light modulator (SLM) based maskless photolithographic applications. The system is capable of high-precision focusing without affecting the photoresist performance. It is based on contrast measurement combined with focus-pattern-illumination to ensure high contrast at the substrate surface. In addition, we evaluated various autofocus algorithms with respect to time efficiency and accuracy to determine suitable focus-pattern and focus-algorithm combinations.

Parameter optimization analysis to minimize the polarizationerror in localized thermal tuneable fiber ring resonator gyro

prasadarao bobbili, DV Rama Koti Reddy, Jagannath Nayak, and Prerana Pinnoji

Doc ID: 251921 Received 15 Oct 2015; Accepted 03 Feb 2016; Posted 04 Feb 2016  View: PDF

Abstract: The accuracy of the resonant frequency servo loop is a major concern for the high-performance operation of theresonant fiber optic gyro. For instance, a bias error as large as tens or even hundreds of degrees/hour has been observed at thedemodulated output of the resonant frequency servo loop. The traditional frequency servo mechanism is not an efficient tool toaddress this problem. In our previous transitions, we proposed a novel method to minimize the laser frequency noise to thelevel of shot noise by refractive index modulation by thermally tuneable resonator. In this paper, we performed the parametersoptimization in resonator coil, MIOC and couplers by transition matrix using Jones matrix methodology to minimize thepolarization error. With optimized parameters values we achieved the bias value of R-FOG to 1.9240/hr.

Multi-focus image fusion using difference image-based guided filter

Xiang Yan, Hanlin Qin, Jia Li, Huixin Zhou, and Tingwu Yang

Doc ID: 255763 Received 15 Dec 2015; Accepted 02 Feb 2016; Posted 02 Feb 2016  View: PDF

Abstract: The aim of multi-focus image fusion technology is to integrate different partially focused images into an all focused image. To realize this goal, a new multi-focus image fusion method based on guided filter is proposed in this paper. In our work, an efficient salient feature extraction method is presented. Based on the salient feature extraction idea, the guided filter is first used to acquire the smoothing image containing the most sharpness regions. Subsequently, to obtain the initial fusion map, we pose a mixed focus measure by combining the variance of image intensities and the energy of image gradient together. Then, the initial fusion map needs to be further processed by morphological filter to obtain good reprocessed fusion map. Finally, the final fusion map is determined via the reprocessed fusion map is optimized by guided filter to gain the desired fusion map. Experimental results demonstrate that the proposed method does markedly improve the fusion performance compared to the previous fusion methods and even can be competitive with or even outperform the state-of-the-art fusion methods in terms of both subjective visual effect and the objective quality metrics.

Absolute Flatness testing of Skip-flat Interferometry by Matrix Analysis in Polar Coordinate

Zhigang Han, Lei Chen, and lu Yin

Doc ID: 255393 Received 10 Dec 2015; Accepted 02 Feb 2016; Posted 04 Feb 2016  View: PDF

Abstract: A new method utilizing matrix analysis in polar coordinate has been presented for absolute testing of skip flat interferometry. The retrieval of the absolute profile mainly includes three steps: (1) transform the wavefront maps of the two cavity measurements into data in polar coordinate; (2) retrieve the profile of the reflective flat in polar coordinate by matrix analysis; (3) transform the profile of the reflective flat back into data in Cartesian coordinate and retrieve the profile of the sample. Simulation of synthetic surface data has been provided, showing the capability of the approach to achieve an accuracy of the order of 0.01 nanometer rms. The absolute profile can be retrieved by a set of closed mathematical formulas without polynomial fitting of wavefront maps and the iterative evaluation of an error function, making the new method more efficient for absolute testing.

Design of All-Reflective Dual-Channel FoveatedImaging Systems based on Freeform Optics

Dewen Cheng, Chen Xu, Yongtian Wang, and JinJin Chen

Doc ID: 253717 Received 10 Nov 2015; Accepted 01 Feb 2016; Posted 03 Feb 2016  View: PDF

Abstract: This paper presents a practical method to design all-reflective dual-channel foveated imaging systems. Such asystem statically has two optical channels, one with a wider field-of-view for searching and another with a longfocal length for fine reconnaissance. The two channels have a common center field angle. These systems may beuseful for remote sensing where coarse searching and fine observation are simultaneously needed. Todemonstrate the method, two corresponding systems are designed. The results reveal an angular resolution offiner than 4” for fine observation and a zoom ratio of 2.9× or 2.5× between the two channels. The modulationtransfer function curves of both channels are above 0.3 at 100 lp/mm. Freeform surfaces are adopted to improveimaging quality and obtain a proper structure for fabrication.

Dual-wavelength Nd:YAG laser operation at 1319nmand 1338nm by direct pumping at 885 nm

Bin Lin, Kun Xiao, Qiulin Zhang, Dongxiang Zhang, Baohua Feng, Qinan Li, and Jingliang He

Doc ID: 251744 Received 12 Oct 2015; Accepted 01 Feb 2016; Posted 08 Feb 2016  View: PDF

Abstract: This paper presents a continuous wave (CW) and a Q-switched Nd:YAG laser pumped by diode laser at 885nm. Themaximum output power of the CW laser is 8.28W with an absorbed slope efficiency of 35.01%. The Q-switching isachieved using a V3+:YAG crystal as the saturable absorber. The maximum output power of the passively Qswitchedlaser is 3.55W with an absorbed pumping power of 28.65W operated with dual-wavelength at 1319nmand 1338nm, respectively. The shortest pulse widths of the Q-switched laser are 20.20ns and 20.86ns, respectively,with a maximum repetition rate of 64.10 kHz.

Optimal design of multilayer diffractive optical elements with effective area method

yang hongfang, Changxi Xue, Wang Ju, and Chuang Li

Doc ID: 256153 Received 22 Dec 2015; Accepted 01 Feb 2016; Posted 02 Feb 2016  View: PDF

Abstract: A method to design high efficiency multiplayer diffractive optical elements(MLDOEs) with finite feature sizes for wide waveband is described and called the effective area method. This method is based on scalar diffraction theory (SDT) and modified SDT with consideration of the shield effect between two elements of MLDOEs. Optimal surface relief heights of MLDOEs are presented with the effective area method. Then the comparisons of diffraction efficiency and polychromatic integral diffraction efficiency for MLDOEs with different periods widths are described and simulated with effective area method and SDT. Finally, the design results of SDT and effective area method are compared by a rigorous electromagnetic analysis technique, specifically, the finite difference time-domain method. These results show that the limits of SDT for MLDOEs, ascertain and quantify the greatest sources of the diffraction efficiency loss due to shield effect. The effective area method’s design results can obtain the higher polychromatic integral diffraction efficiency than the SDT when the period widths of MLDOEs is taken into account.

Optical eye simulator for laser dazzle events

João Coelho, José Freitas, and Craig Williamson

Doc ID: 253803 Received 11 Nov 2015; Accepted 01 Feb 2016; Posted 02 Feb 2016  View: PDF

Abstract: An optical simulator of the human eye and its application to laser dazzle events is presented. The simulator combines optical design software (ZEMAX©) with a scientific programing language (MatLab©), and allows the user to implement and analyze a dazzle scenario using practical, real world, parameters. Contrary to conventional analytical glare analysis, this work uses ray tracing and the scattering model and parameters for each optical element of the eye. The theoretical background to each such element is presented in relation to the model. The overall simulator’s calibration, validation and performance analysis is achieved by comparison to a simpler model based upon CIE disability glare data. Results demonstrate that this kind of advanced optical eye simulation can be used to represent laser dazzle and has the potential to extend the range of applicability of analytical models.

Comparison of ablation mechanisms at low fluence for ultra-short and short pulse laser exposure of very thin molybdenum films on glass

Pinaki Das Gupta and Gerard O'Connor

Doc ID: 254155 Received 18 Nov 2015; Accepted 01 Feb 2016; Posted 02 Feb 2016  View: PDF

Abstract: Complete removal of a loosely adhered very thin molybdenum film from a glass substrate is investigated for both femtosecond and nanosecond lasers at different wavelengths. AFM and SEM confirm that ablation of the molybdenum film by femtosecond pulses occurs close to the damage threshold fluence, creating minimal damage to the substrate. This is in contrast to nanosecond laser processing where significant substrate damage at the equivalent damage threshold fluence is observed. Simulations predict a two stage mechanical buckling mechanism in the femtosecond case. Out of plane thermal expansion first results in a tensile expansion of molybdenum film from the glass substrate; this locally delaminated film is then buckled by a subsequent compressive stress, leading to thin film spallation. Ablation by nanosecond laser pulses behaves differently. The appreciable heat diffusion length (~700nm) in molybdenum, observed for the nanosecond case, results in an increased thermal expansion of the glass. The thermally induced stress generated by the molten glass creates a delaminated area which “pushes” the compressed film away from the substrate. These findings are relevant to future selective laser patterning of very thin molybdenum layers.

EXAFS measurements on RF magnetron sputtered HfO2 thin films deposited with different oxygen partial pressures

DIBYENDU BHATTACHARYYA, Sk Haque, C Nayak, S Jha, and Naba Sahoo

Doc ID: 254239 Received 18 Nov 2015; Accepted 01 Feb 2016; Posted 02 Feb 2016  View: PDF

Abstract: Two sets of HfO2 thin film have been deposited by RF magnetron sputteringtechnique at various oxygen partial pressures; one set without any substrate bias andanother set with a 50 Watt pulsed DC substrate bias. The films have beencharacterised by Extended X-ray absorption fine structure (EXAFS) measurements atHf L3 edge and the structural information obtained from analysis of the EXAFS datahave been used to explain the macroscopic behaviour of refractive index obtainedfrom spectroscopic ellipsometry measurements. It has been observed that the variationof refractive index with oxygen partial pressure depends on the Hf-Hf bond length forthe set of films deposited without substrate bias, while for the other set of filmsdeposited with pulsed DC substrate bias, it depends on the oxygen coordination of thenearest neighbour shell surrounding Hf sites.

Research on laser induced damage resistance of fused silica optics by fluid jet polishing method

Liang LV, Ping Ma, Jingyong Huang, xiang he, Chao Cai, and Heng Zhu

Doc ID: 252666 Received 26 Oct 2015; Accepted 01 Feb 2016; Posted 04 Feb 2016  View: PDF

Abstract: Laser induced damage threshold (LIDT) is one important evaluation index for optical glasses applied in large laserinstruments which are exposed to high light irradiation flux. As a new kind of precise finishing technology, fluid jetpolishing (FJP) has been widely used in generating high accuracy surface shape of planner, spherical andaspherical optics. Laser damage resistances of fused silica optics by FJP process were studied in this paper. Fusedsilica samples with various FJP parameters are prepared, and laser damage experiment is performed with 351 nmwavelength and 5.5 ns time width laser pulses. Experimental results demonstrate that compared to their originalstate, the LIDT of the samples treated with FJP processes did not increase. The surface quality of the samples is onereason for the decrease of LIDT. For ceria solution polished samples, cerium element remaining is another reasonof the lower LIDT.

A resonantly-pumped actively mode-locked Ho:YAG ceramic laser at 2122.1 nm

Xiaoming Duan, Jinhe Yuan, Zheng Cui, baoquan yao, Tongyu Dai, Li Jiang, and Yubai Pan

Doc ID: 253778 Received 11 Nov 2015; Accepted 01 Feb 2016; Posted 04 Feb 2016  View: PDF

Abstract: We report a continuous-wave mode-locked Ho:YAG ceramic laser for the first time to our knowledge. Mode-lockedpulse was produced by using an acousto-optic modulator. A 1.91 μm Tm-fiber laser was used as the pump source.At the incident pump power of 11.4 W, the maximum output power of 1.84 W at 2122.1 nm was achieved incontinuous-wave mode-locked regime. A short-duration pulse of 241.5 ps was obtained at a repetition frequency of82.15 MHz, and the beam quality factor M2 of 1.2 was achieved. In addition, the maximum single pulse energy was22.4 nJ.

Orbital-angular-momentum-multiplexed free-space optical communication link using transmitter lenses

Long Li, Guodong Xie, Yongxiong Ren, Nisar Ahmed, Hao Huang, Zhe Zhao, Peicheng Liao, Martin Lavery, Yan Yan, Changjing Bao, Zhe Wang, Asher Willner, Nima Ashrafi, Solyman Ashrafi, Moshe Tur, and Alan Willner

Doc ID: 253974 Received 18 Nov 2015; Accepted 01 Feb 2016; Posted 04 Feb 2016  View: PDF

Abstract: In this letter, we explore the potential benefits and limitations of using transmitter lenses in an orbital-angular-momentum (OAM)-multiplexed free-space optical (FSO) communication link. Both simulation and experimental results indicate that within certain transmission distances, using lenses at the transmitter to focus OAM beams could reduce power loss in OAM-based FSO links, and that this improvement might be more significant for higher-order OAM beams. Moreover, the use of transmitter lenses could enhance system tolerance to angular error between transmitter and receiver, but might degrade tolerance to lateral displacement.

Multi-Scale Optical Simulation Settings – Challenging Applications Handled with an Iterative Ray-Tracing-FDTD Interface Method

Claude Leiner, Wolfgang Nemitz, Susanne Schweitzer, Ladislav Kuna, Franz Wenzl, Paul Hartmann, Valentin Satzinger, and Christian Sommer

Doc ID: 251194 Received 07 Oct 2015; Accepted 01 Feb 2016; Posted 02 Feb 2016  View: PDF

Abstract: We show that with an appropriate combination of two optical simulation techniques – classical ray-tracing and the finite difference time domain method – optical devices containing multiple diffractive and refractive optical elements can be simulated accurately in an iterative simulation approach. We compare the simulation results with experimental measurements of the device to discuss the applicability and accuracy of our iterative simulation procedure.

Light Trapping at Dirac Point in 2D triangular Archimedean-like Lattice Photonic Crystal

Qiuping Mao, Kang Xie, Lei Hu, Qian Li, Wei Zhang, Erlei Wang, Hai Ming Jiang, and Hu Zhijia

Doc ID: 252119 Received 19 Oct 2015; Accepted 31 Jan 2016; Posted 02 Feb 2016  View: PDF

Abstract: Among modern optical devices, optical cavities and waveguides count for much. Traditionally, optical cavities and waveguides rely on photonic bandgaps, or total internal reflection, to achieve light trapping. Here, we report a novel discovery of light trapping that is attributed to the so-called Dirac point. Our analysis reveals that, 2D triangular Archimedean-like lattice photonic crystals can support the Dirac mode. This is a new type of localized mode with a different algebraic profile at a Dirac frequency that is beyond any complete photonic bandgap. The new wave localization has different features and can be applied to the design of new optical devices.

Application of white light Fresnel diffractometry to film thickness measurement

Khosrow Hassani, Mehdi Ashrafganjoie, and Mohammad Tavassoly

Doc ID: 255107 Received 03 Dec 2015; Accepted 30 Jan 2016; Posted 01 Feb 2016  View: PDF

Abstract: In this work we present the theoretical background and experimental procedure to measure the thickness of thin films by analyzing the Fresnel diffraction patterns obtained from polychromatic illumination of phase-step samples. As examples of this technique, we measured the thicknesses of thin aluminum layers on glass substrates, using three different broad-spectrum light sources. The results are in excellent agreement with independent interferometric measurements within less than 5 percent relative uncertainties.

Dual-wavelength interferometry based on the spatial carrier-frequency phase-shifting method

Liyun Zhong, Linbo Huang, Xiaoxu Lu, Yunfei Zhou, and Jindong Tian

Doc ID: 254810 Received 30 Nov 2015; Accepted 30 Jan 2016; Posted 01 Feb 2016  View: PDF

Abstract: From single-frame dual-wavelength spatial carrier-frequency interferogram (SCFI), we propose a novel phase retrieval method of dual-wavelength interferometry (DWI). First, by continuously moving the intercepted area pixel-by-pixel in single-frame SCFI along the horizontal and vertical directions, we construct a sequence of phase-shifting sub-interferograms. Second, the wrapped phases of each single-wavelength can be retrieved from those phase-shifting sub-interferograms through using the least-square iteration algorithm. Third, the phase of synthetic wavelength can be obtained by a subtraction between the wrapped phases of single-wavelength. Both the numerical simulation and the experimental result demonstrate that the proposed method reveals the higher accuracy and convenient performance. What’s more, because only single-frame SCFI is enough to perform the phase retrieval of DWI, the proposed method possesses the better ability of resisting the external vibration and disturbance, and this will greatly facilitate the application of DWI in the dynamic phase measurement.

Dual-wavelength Nd:LGGG laser intracavity pumped simultaneous OPO and SRS processes in single KTP

Hongwei Chu, Jia Zhao, Yufei Li, Shengzhi Zhao, Kejian Yang, Tao Li, Dechun Li, Guiqiu Li, and qiaowen chao

Doc ID: 256479 Received 29 Dec 2015; Accepted 29 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: Simultaneous optical parametric oscillation (OPO) and stimulated Raman scattering (SRS) in a single KTiOPO4 (KTP) intracavity pumped by a dual-wavelength Nd:LGGG laser were demonstrated for the first time. A maximum output power for the signal beam was 448 mW, while for the Stokes radiations it was 40 mW, corresponding to an overall conversion efficiency of about 4.65%. The shortest pulse durations for OPO and SRS waves were directly measured to be 850 ps and 1.526 ns, respectively. The highest peak power of 30.6 kW and the pulse energy of 26 μJ for the signal beam were also obtained. A set of coupled rate equations for the dual-wavelength pumped OPO and SRS was also established. The numerical solutions fitted with the experimental results.

Experimental Verification of LTE Radio Transmissions over Dual-polarization Combined Fibre and FSO Optical Infrastructures

Jan Bohata, Stanislav Zvanovec, Zabih Ghassemlooy, Tomas Korinek, Mojtaba Abadi, and Petr Pesek

Doc ID: 254703 Received 30 Nov 2015; Accepted 29 Jan 2016; Posted 01 Feb 2016  View: PDF

Abstract: This paper describes the experimental verification of the utilization of long-term evolution (LTE) radio over fibre(RoF) and radio over free space optics (RoFSO) systems using dual-polarization signals for cloud radio accessnetwork (C-RAN) applications determining the specific utilization limits. A number of FSO configurations isproposed and investigated under different atmospheric turbulence regimes in order to recommend the best setupconfiguration. We show that the performance of the proposed link based on the combination of RoF and RoFSO for64-QAM at 2.6 GHz is more affected by the turbulence based on the measured difference error vector magnitudevalue of 5.5 %. It is further demonstrated the proposed systems can offer higher noise immunity under particularscenarios with the signal-to-noise ratio reliability limit of 5 dB in the radio frequency domain for RoF and 19.3 dBin the optical domain for combination of RoF and RoFSO links.

Scalability of components for kW level average power few-cycle lasers

Steffen Hädrich, Jan Rothhardt, Stefan Demmler, Maxim Tschernajew, Armin Hoffmann, Manuel Krebs, Andreas Liem, Oliver de Vries, Marco Plötner, Simone Fabian, Thomas Schreiber, Jens Limpert, and Andreas Tünnermann

Doc ID: 254471 Received 23 Nov 2015; Accepted 29 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: In this paper the average power scalability of components that can be used for intense few-cycle lasers based on nonlinear compression of modern femtosecond solid-state lasers is investigated. The key components of such a setup, namely the gas-filled waveguides, laser windows, chirped mirrors for pulse compression and low dispersion mirrors for beam collimation, focusing and beam steering are tested under high average power operation using a kilowatt cw laser. We demonstrate long-term-stable transmission of kW-level average power through a hollow capillary and a Kagome-type photonic crystal fiber. In addition, we demonstrate that sapphire substrates significantly improve the average power capability of metal-coated mirrors. Ultimately, ultra-broadband dielectric mirrors show negligible heating up to 1 kW of average power. In summary, a technology for scaling of few-cycle lasers up to 1 kW of average power and beyond is presented.

3D robust digital image correlation for vibration measurement

Zhong Chen, Xianmin Zhang, and Sergej Fatikow

Doc ID: 254560 Received 24 Nov 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: The discrepancies of the speckle images under a dynamic measurement due to the different viewingangles will deteriorate the correspondence in 3D Digital Image Correlation (3D-DIC) for vibration measurement.Facing this kind of bottlenecks, this paper presents two kinds of robust 3D-DIC methods forvibration measurement including the SSD-Robust and SWD-Robust methods which use a SSD (Sumof Square Difference) estimator plus a Geman-McClure regulating term and a Welch estimator plus aGeman-McClure regulating term, respectively. Because the regulating term with an adaptive rejectingbound can lessen the influence of the abnormal pixels data in the dynamical measuring process, the robustnessof the algorithm is enhanced. The robustness and precision evaluation experiments using a dualfrequency laser interferometer are implemented. The experimental results indicate that the two presentedrobust estimators can suppress the effects of the abnormality in the speckle images and meanwhile keephigher precision in vibration measurement in contrast to the traditional SSD method, the SWD-Robustmethod and SSD-Robust methods are suitable for little image noise and strong image noise respectively.

Compact InGaAsP/InP 3×3 multimode interference coupler based electro-optic switch

Ke Liu, Sixuan Mu, Shuang Wang, Chenglong Zhang, B.L. Guan, and Deshu Zou

Doc ID: 254637 Received 30 Nov 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: Optical switches are key components in data links for optical communication networks, requiring low crosstalk and insertion loss, and high switching speed and power efficiency. Multimode interference (MMI) coupler based switch with multiple input and output serving as a switching unit is desired towards forming a large-scale switch matrix. Here we demonstrate a compact 3×3 MMI coupler electro-optic switch based on carrier injection effect on InGaAsP/InP substrates. This switch device is 2780-μm long by 18-μm wide. The switching states can be controlled by two index modulation regions through bias voltages applied. Our simulation results show that the device exhibits low crosstalk of less than ~-22 dB, low insertion loss of ~0.12 dB, and low switching energy of ~10 fJ/bit. Experimentally we validated one switching state from B3 to B2 ports when A1 acts as light input on a fabricated device. Such monolithic integration schemes enable them an ideal candidate for future on-chip photonic integrated circuits.

A new Time-Space-Time optical packet switching node based on nonlinear polarization rotation of semiconductor optical amplifier

Yongjun Wang, Tian Qinhua, Zhi Wang, xiaoqing zhu, chen wu, Chao Shang, and xin xiangjun

Doc ID: 254894 Received 07 Dec 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: In this paper, we establish a simple model to analyze the SOA’s NPR, and acquire the variable curves of phase difference between TE and TM mode with bias current, pump power, probe power and LEF. The results indicate that the optical switch based on SOA’s NPR can be realized by changing pump optical power and the main operating parameters, such as bias current, hold beam power, pump power can be determined. On this basis, a T-S-T optical packet switching node is proposed, in which SOA’s NPR switch is as the basic element. Then the T-S and S-T experimental systems are set up and the experimental results demonstrate that the proposed switch scheme can implement the optical switching function in accordance with the routing requirement and SNR exceeds 20dB and ER is more than 10dB after being delayed and switched in the node.

Restraint of rang walk error in a Gm-APD lidar to acquire high-precision depth and intensity information

Lu Xu, Yu Zhang, Zhang Yong, Chenghua Yang, Xu Yang, and Yuan Zhao

Doc ID: 255474 Received 10 Dec 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: There exists a range walk error in a Gm-APD lidar because of the fluctuation in number of signal photoelectrons. To restrain this range walk error, we proposed a new returning-wave signal processing technique based on the Poisson probability response model and the Gaussian functions fitting method. A high-precision depth and intensity information of the target at the distance of 5 m is obtained by a Gm-APD lidar using a 6 ns wide pulsed laser. The experiment results show that the range and intensity precisions are 1.2 cm and 0.015 photoelectrons, respectively.

The waveform model of a laser altimeter under elliptical Gaussian beam

Yue Ma, Guoyuan LI, Fanlin Yang, Mingwei Wang, and Xiushan Lu

Doc ID: 254940 Received 03 Dec 2015; Accepted 28 Jan 2016; Posted 28 Jan 2016  View: PDF

Abstract: The current waveform model of laser altimeters is based on the Gaussian laser beam of the fundamental mode, whose cross section is a circular spot, whereas some of the cross sections of GLAS lasers are closer to elliptical spots. Based on the expression of the elliptical Gaussian beam and the waveform theory of laser altimeters, the primary parameters of echo waveform were derived, and in order to examine the deduced expressions, the laser altimetry waveform simulator and waveform processing software were programmed and improved under the circumstance of elliptical Gaussian beam. The result shows that all the biases between theoretical and simulated waveforms were less than 0.5%, and the derived model of an elliptical spot is more universal, which could also be used for the conventional circular spot. The shape of waveforms is influenced by the ellipticity of a laser spot, the target slope, and the ‘azimuth angle’ between the major axis and the slope direction. This article provides the waveform theoretical basis under elliptical Gaussian beam using in a laser altimeter.

Control of the Goos-Hänchen shifts of a probe light beam using phase tunability of the intracavity medium.

Arash Radmehr, Mostafa Sahrai, and Hamed Sattari

Doc ID: 254003 Received 16 Nov 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: We present a model to manipulate the Goos-Hänchen (GH) shifts of a probe light beam in a fixed cavity configuration containing the three level V-type atomic medium. We find that in the presence of decay-induced interference the lateral shifts of the both reflected and transmitted probe light beam can easily be controlled just by the relative phase of applied fields. The intensity of the applied field on GH shifts of the reflected and transmitted probe light beam is also discussed.

Modeling of Carrier Dynamics in InGaAs/GaAs Self-Assembled Modeling of Carrier Dynamics in InGaAs/GaAs Self-Assembled Quantum Dot Lasers

meysam kashiri and asghar asgari

Doc ID: 254181 Received 18 Nov 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: In this study, a theoretical model is used to model the lasing characteristics of InGaAs/GaAs self-assembled quantum dot lasers (SAQDLs). The rate equation for InGaAs/GaAs is numerically solved using the fourth-order Runge-Kutta method. We consider the homogeneous and inhomogeneous broadening of optical gain, both with and without considering the nonlinear gain. The results indicate that for a certain injected current, there is a specific homogeneous broadening (HB) with the best lasing performance when HB is near, comparable or equal to inhomogeneous broadening (IHB) for every lasing injected currents. We show that if replacing linear optical gain by total gain, the output power will reduce a little and the peaks will be more broadened and the maximum of gain spectrum decreases. The time evolution of photon number for different currents and different HB is shown. The results indicate that with increasing in HB, the number of photon in steady state and delay in starting oscillation will increase. In addition, we show that there is threshold coverage for quantum dot to begin lasing and an optimum quantum dot coverage in which the self assemble quantum dot lasers operate with lowest possible threshold current and maximum output power.

Spectrophotometric determination of turbid optical parameters without integrating sphere

Xin-Hua Hu, Xiaohui Liang, Meihua Li, Jun Lu, Chuanwei Huang, Yuanming Feng, Yu Sa, and Junhua Ding

Doc ID: 254270 Received 19 Nov 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: Spectrophotometric quantification of turbidity by multiple optical parameters has wide-ranged applications in material analysis and life sciences. A robust system design needs to combine hardware for precise measurement of light signals with software to accurately model measurement configuration and rapidly solve a sequence of challenging inverse problems. We have developed and validated a design approach and performed system validation based on radiative transfer theory for determination of absorption coefficient, scattering coefficient and anisotropy factor without integrating sphere. Accurate and rapid determination of parameters and spectra is achieved by combining photodiode based measurement of 4 signals with the Monte Carlo simulation and perturbation based inverse calculations implemented on graphic processing units. The three parameters of microsphere suspension samples have been determined from the measured signals as functions of wavelength from 400 to 800nm which agree with the Mie theory results. It has been shown that the inverse problems in the cases of highly turbid samples of microsphere suspension are well-posed with convex cost functions to yield unique solutions, which takes about 1 minute to obtain the three parameters per wavelength.

Plasmon enhanced performance of ultrathin silicon solar cell by using metal-semiconductor core-shell hemispherical nanoparticles and metallic back grating

Mahboubeh Dolatyari, ghassem Rostami, Ali Rostami, and hamid heidarzadeh

Doc ID: 246506 Received 22 Jul 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: We present a concept for significant improvement the photocurrent of ultrathin crystalline silicon solar cellsusing plasmonic hemispherical dielectric-metal (core-shell) nanoparticles and backside gratings. The design of threedimensionalspherical and hemispherical arrays of nanoparticles on top the surface of 0.8μm crystalline silicon solar cellsis simulated using finite difference time-domain (FDTD) method. FDTD results are used to investigate photocurrent bysolving the Poisson and drift diffusion equations. The results indicate 80% and 93% enhancement in photocurrent forcells with hemispherical Ag and Ag-SiO2 core-shell nanoparticles, respectively, respect to a cell with sphericalnanoparticles. In addition, for obtaining higher photocurrent, triangular gratings are applied on the back side of absorberand photocurrent of 22mA/cm2 is obtained. The simulated results indicate that proposed structures increase the spectralresponse of thin-film crystalline silicon solar cells over solar spectrum in the range of 400nm-1200nm. Finally,photocurrent as a function of incidence light angle has been investigated. This approach is applicable to variousthicknesses and shapes of nanoparticles.

Goniospectrometric space: Identifiable presentation of spectral goniometric data for complex diffractive samples

Nina Rogelj, Marta Gunde, Niko Penttinen, and Miha Čekada

Doc ID: 250499 Received 21 Sep 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: Optical security takes advantage of complex gonioapparent effects of diffractive samples having strong angular and spectral dependence of reflected light. However, resolving the full angular and spectral properties of these kind of targets might be a tremendous task. Preferably one would like to measure more limited number of illumination-viewing directions, using multiangle goniometer, and still reveal the complex and unique properties of the target. In this study, we use a method for converting the full angular reflection data into reduced goniospectrometric space, and further on into an xDNA graph, which we find to show a good potential as a fingerprint for gonioapparent surfaces when limited measurement geometries are available. For the evaluation of the xDNA graph, we use two goniometric devices with 45° incident angle illumination; a high resolution bidirectional spectrometer and a portable multiangle goniometer. This study tests the xDNA graph by evaluating the effects of both geometry count and spectral resolution in goniometric measurements, and further finds, that the xDNA graph indeed works best with reduced count of geometries and is not sensitive to lowered spectral resolution.

Phase-derivative-based estimation of digital reference wave from single off-axis digital hologram

davood khodadad

Doc ID: 252618 Received 23 Oct 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: This paper describes a method to obtain an estimated digital reference wave from a single off-axis digital hologram thatmatches the actual experimental reference wave as closely as possible. The proposed method is independent of areference flat plate and speckles. The digital reference wave parameters are estimated directly from the recorded phaseinformation. The parameters include both the off-axis tilt angle and the curvature of the reference wave. Phasederivatives are used to extract the digital reference wave parameters without the need for a phase unwrapping process.Thus, problems associated with phase wrapping are avoided. Experimental results for the proposed method areprovided. The simulated effect of the digital reference wave parameters on the reconstructed image phase distribution isshown. Pseudo phase gradient originated from incorrect estimation of the digital reference wave parameters and its effect on objectreconstruction are discussed.

Studies on Design of 351nm Focal Plane Diagnostic System Prototype and Focusing Characteristic of SGII-Upgraded Facility at Half Energy Performance

liu chong, Lailin Ji, Lin Yang, Dongfeng Zhao, zhang yanfeng, liu dong, Bao-Qiang Zhu, and Zunqi Lin

Doc ID: 252694 Received 26 Oct 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: In order to obtain the intensity distribution of 351nm focal spot and SSD (smoothing by spectral dispersion)focal plane profile of SGII Upgraded Facility ,a type of off-axis imaging system with three spherical mirrors which is suitable for finite distance source point to be imaged near diffraction limited had been designed. The quality factor of the image system is 1.6 times of diffraction limit tested by 1053nm point source. Because of the absence of 351nm point source, by means of Collins diffraction imageing integral with respect to λ=351nm,corresponding quality factor is 3.8 times of diffraction limit at 351nm. The calibration results show that at least the range of ±10mrad of view field angle and ±50mm along axial direction around the optimum object distance can be satisfied with near diffraction limited image that is consistent of design value. Using this image system, NO.2 beam of SGII Upgraded Facility has been tested. The test result of focal spot of Final Optical Assemble(FOA) at 351nm indicate that about 80 percent of energy be encompassed in 14.1 times of diffraction limit while the output energy of NO.2 beam is 809J at 1053nm.According to convolution theorem, true value of 351nm focal spot of FOA is about 12 times of diffraction limit because of the effect of quality factor. Further experimental studies indicate that the RMS value along the smoothing direction be less than 15.98% in SSD spot test experiment. Computer simulation studies show that quality factor of image system used in experiment have almost no effect on SSD focal spot test. Image system remarkably distort the SSD focal spot distribution under the circumstance of the quality factor worse than 15 times diffraction limit. The distorted image shows a steep slop in the contour of SSD focal spot along smoothing direction which have otherwise a relatively flat top region around focal spot centre.

Shaping of cylindrical and 3D ellipsoidal beams for electron photoinjector laser drivers

Sergey Mironov, Anatoly Poteomkin, Ekaterina Gacheva, Alexey Andrianov, Victor Zelenogorsky, Mikhail Krasilnikov, Frank Stephan, and Efim Khazanov

Doc ID: 253273 Received 03 Nov 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: With the use of spatial light modulators it became possible to implement in experiment the method of controllingthe space-time intensity distribution of femtosecond laser pulses stretched to picosecond duration. Cylindrical andquasi-ellipsoidal intensity distributions were obtained and characterized by means of a 2D spectrograph and across-correlator.

All-fiber high average power nanosecond pulsed MOPA at 2 μm with mJ-level pulse energy

Xiong Wang, Xiaoxi Jin, Pu Zhou, Xiaolin Wang, Hu Xiao, and Zejin Liu

Doc ID: 253341 Received 04 Nov 2015; Accepted 28 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: We present a high power nanosecond pulsed Tm-doped fiber amplifier at 1.971 μm based on master oscillator power amplifier (MOPA) configuration. When the repetition rate is 500 kHz and the pulse width is 63.3 ns, the average power reaches 8 W, the peak power reaches 7.06 kW, and the pulse energy is 0.477 mJ. When the pulse train’s repetition rate is 300 kHz with a pulse width of 63.7 ns, the average power reaches 197 W, the peak power reaches 9.73 kW, and the pulse energy is 0.66 mJ. When the pulse train’s repetition rate is 200 kHz with a pulse width of 58.2 ns, the average power reaches 150 W, the peak power reaches 12.1 kW, and the pulse energy is 0.749 mJ. The spectral linewidth of the pulse trains are 0.15 nm, 0.14 nm and 0.10 nm for 500 kHz repetition rate, 300 kHz repetition rate and 200 kHz repetition rate, respectively. To the best of our knowledge, this is the first demonstration on high power nanosecond pulsed MOPA at 2 μm with the maximum average power reaching 8 W, the maximum peak power reaching 12.1 kW, and the maximum pulse energy reaching 0.749 mJ.

Dual band sensitivity enhancements of VOx microbolometer array using patterned gold black absorber

Evan Smith, Deep Panjwani, James Ginn, Andrew Warren, Christopher Long, Pedro Figuieredo, Christian Smith, Janardan Nath, Joshua Perlstein, Nick Walter, Carol Hirschmugl, Robert Peale, and David Shelton

Doc ID: 251710 Received 12 Oct 2015; Accepted 28 Jan 2016; Posted 01 Feb 2016  View: PDF

Abstract: Infrared-absorbing gold black has been selectively patterned onto the active surfaces of a vanadium-oxide based infrared bolometer array. Patterning by metal lift-off relies on protection of the fragile gold black with an evaporated oxide, which preserves much of gold black’s high absorptance. This patterned gold black also survives the dry-etch removal of the sacrificial polyimide used to fabricate the air-bridge bolometers. For our fabricated devices, infrared responsivity is improved 22% in the LWIR and 70% in the MWIR by the gold black coating, with no significant change in detector noise, using a 300 C blackbody and 80 Hz chopping rate. The increase in the time constant caused by the additional mass of gold black is ~15%.

Formation and Emission Characteristics of CN Moleculesin Laser Induced Low Pressure He Plasma and ItsApllications to N Analysis in Coal and Fossilization Study

Koo Hendrik Kurniawan, Kurnia Lahna, Rinaldi Idroes, Nasrullah Idris, Syahrun Abdulmadjid, May-On Tjia, Marincan Pardede, and Kiichiro Kagawa

Doc ID: 254994 Received 02 Dec 2015; Accepted 28 Jan 2016; Posted 01 Feb 2016  View: PDF

Abstract: Presented in this report are the results of an experimental study on the laser induced plasmaemission of a number of CN free samples (urea, sucrose) with 40 mJ pulse energy using Heand N2 ambient gases. It is shown that the CN emission has its exclusive sources in themolecules produced as the results of chemical bonding either between the ablated C and Nions in the He plasma or between the ablated C and dissociated N from the N2 ambient gas.The emission intensities in both cases are found to have the highest values at the low gaspressure of 2 kPa. The emission in He gas is shown to exhibit the typical characteristicsrelated to shock wave generated excitation mechanism. The experiments using He ambientgas further demonstrate the feasible LIBS application to quantitative and sensitive N analysisof coal and promising application for practical in-situ carbon dating of fossils.

High Speed Ultrashort Pulse Fiber Ring Laser Using Charcoal Nano-particles

Wenbo Li, Hongyu Hu, Xiang Zhang, Shuai Zhao, Kan Fu, and Niloy Dutta

Doc ID: 254323 Received 20 Nov 2015; Accepted 28 Jan 2016; Posted 03 Feb 2016  View: PDF

Abstract: A mode-locked erbium-doped fiber ring laser which is easy to set up is proposed and experimentally demonstrated to generate a high-repetition-rate optical pulse train with ultrashort pulse width. The laser combines rational harmonic mode-locking technique and charcoal nano-particles as saturable absorbers. Compared to solely active mode-locking scheme, the scheme with charcoal nano-particles can remove the supermodes and narrow the pulse width by a factor of 0.57 at repetition rate of 20 GHz. Numerical simulation of the laser performance is also provided, which shows good agreement with the experimental results.

Polarization-dependent loss characterization method based on optical frequency beat

Thiago Ferreira da Silva, Camila Nobre, and Guilherme Temporao

Doc ID: 256299 Received 23 Dec 2015; Accepted 27 Jan 2016; Posted 05 Feb 2016  View: PDF

Abstract: Characterization of the polarization-dependent loss (PDL) of optical components is fundamental for the reliable operation of fiber-optic communication systems. Here we present a method for determining the PDL of optical devices based on optical frequency beating and spectral analysis. Depending on the beat note between components of two orthogonally-polarized probe signals modulated at different frequencies, the PDL value and its axis can be determined from a single sweep of an optical spectrum analyzer. Our proposal represents an alternative high-speed option for PDL characterization.

D-shape fiber grating refractive index sensor induced by ultrashort pulse laser

Changrui Liao, Qiao Wang, Lei Xu, Shen Liu, Jun He, Jing Zhao, Zhengyong Li, and Yiping Wang

Doc ID: 254771 Received 30 Nov 2015; Accepted 27 Jan 2016; Posted 28 Jan 2016  View: PDF

Abstract: The fabrication of fiber Bragg gratings was here demonstrated using ultrashort pulse laser point-by-point inscription. This is a very convenient means of creating fiber Bragg gratings with different grating periods and works by changing the translation speed of the fiber. The laser energy was first optimized in order to improve the spectral properties of the fiber gratings. Then, fiber Bragg gratings were formed into D-shape fibers for use as refractive index sensors. A nonlinear relationship was observed between the Bragg wavelength and liquid refractive index, and a sensitivity of ~30 nm/RIU was observed at 1.450. This shows that D-shape FBGs might be used to develop promising biochemical sensors.

Self-Triggered Method for Characterization of Single-Photon Detectors

Thiago Ferreira da Silva

Doc ID: 255416 Received 10 Dec 2015; Accepted 27 Jan 2016; Posted 28 Jan 2016  View: PDF

Abstract: Single-photon avalanche photodiodes (SPADs) are instruments capable of measuring light at the single-photon level. Some important features of these devices must be correctly characterized for reliable application. In this paper I present a high-resolution self-triggered method for characterization of SPADs based on the analysis of the time intervals between consecutive detection events with the detector under continuous-wave illumination. The self-triggered method is employed for characterization of the detection deadtime – a limiting feature for the maximum counting rate achievable under free-running or gated modes – and of the temporal gate width – an important parameter when the detector is operated under gated mode. The measurement results are presented and the method is experimentally validated.

Automated Interferometric Synthetic Aperture Microscopy and Computational Adaptive Optics for Improved Optical Coherence Tomography

Yang XU, Yuan-Zhi Liu, Stephen Boppart, and P. Scott Carney

Doc ID: 255844 Received 15 Dec 2015; Accepted 27 Jan 2016; Posted 28 Jan 2016  View: PDF

Abstract: In this paper, we introduce an algorithm framework for the automation of interferometric synthetic aperture microscopy (ISAM). Under this framework, common processing steps such as dispersion correction, Fourier domain resampling and computational adaptive optics (CAO) aberration correction are carried out as metrics-assisted parameter search problems. We further present the results of this algorithm applied to phantom and biological tissue samples and compare with manually adjusted results. With the automated algorithm, near-optimal ISAM reconstruction can be achieved without manual adjustment. At the same time, the technical barrier for the nonexpert using ISAM imaging is also significantly lowered.

Calculation of the radiation forces on a microsphere in the evanescent field of an optical nanofiber by ray tracing

Bo Zhang, Jingxiang Luo, Zhilong Liu, and Feipeng Wu

Doc ID: 254344 Received 23 Nov 2015; Accepted 26 Jan 2016; Posted 28 Jan 2016  View: PDF

Abstract: We use ray optics to calculate the radiation forces on a dielectric microsphere in the evanescent field of an optical nanofiber. We theoretically demonstrate that the gradient force may attact the microsphere onto the fiber surface; the scattering force may transport the microsphere along the fiber and in the light propagating direction. The impacts of the sphere-fiber distance, sphere radius and fiber radius on the scattering and gradient forces are investigated. The radius of nanofiber can be optimized for particle transportation.

Freeform Three-Dimensional Embedded Polymer Waveguides Enabled by External-Diffusion Assisted Two-Photon Lithography

Ho Hoai Duc Nguyen, uwe hollenbach, stefan hengsbach, Ute Ostrzinski, Karl Pfeiffer, and Jürgen Mohr

Doc ID: 252280 Received 26 Nov 2015; Accepted 26 Jan 2016; Posted 26 Jan 2016  View: PDF

Abstract: This paper introduces a novel technique for three-dimensional single-mode waveguide fabrication into a newly-developed photopolymer using two-photon lithography in combination with external diffusion of a gaseous monomer. A high index contrast between the core and the cladding of 0.013 has been achieved. By adjusting the writing speed and laser intensity for the laser writing, it is possible to produce symmetrical square-shaped waveguides with adjustable core dimensions in the range from 5 µm to 20 µm. Fabricated waveguides exhibit high reliability and a transmission loss of 0.37 dB/cm at 850 nm wavelength. The fabrication process requires only one layer of a single material. Multi layers of waveguides could be produced without any stacking or alignment effort. Transmission losses might be further reduced by reducing the waveguide’s roughness by improving the optical sensitivity of the photoresist. Therefore, this technique could pave the way for three-dimensional optical interconnects at board level with high complexity and bandwidth density.

Advanced materials for multilayer mirrors for extreme ultraviolet solar astronomy

Vladimir Polkovnikov, Sergei Bogachev, Nikolay Chkhalo, Sergey Kuzin, Dmitri Pariev, Nikolay Salashchenko, Sergey Shestov, and Sergey Zuev

Doc ID: 252871 Received 28 Oct 2015; Accepted 26 Jan 2016; Posted 26 Jan 2016  View: PDF

Abstract: We provide an analysis of contemporary multilayer optics for extreme ultraviolet (EUV) solar astronomy in the wavelength ranges: λ=12.9–13.3 nm, λ=17–21 nm, λ=28–33 nm and in the range λ=58.4 nm. We found new material pairs, which will make new spaceborne experiments possible due to the high reflection efficiencies, spectral resolution and long-term stabilities of the proposed multilayer coatings. In the spectral range λ=13 nm Mo/Be multilayer mirrors were shown to demonstrate a better ratio of reflection efficiency and spectral resolution compared to the commonly used Mo/Si. In the spectral range λ=17–21 nm a new multilayer structure Al/Si was proposed, which had higher spectral resolution along with comparable reflection efficiency compared to the commonly used Al/Zr multilayer structures. In the spectral range λ=30 nm the Si/B4C/Mg/Cr multilayer structure turned out to best obey reflection efficiency and long-term stability. The B4C and Cr layers prevented mutual diffusion of the Si and Mg layers. For the spectral range λ=58 nm a new multilayer Mo/Mg-based structure was developed, its reflection efficiency and long-term stability have been analyzed. We also investigated intrinsic stresses inherent for most of the multilayer structures and proposed possibilities for the stress elimination.

Direct and inverse problems in X-ray three-crystal LLL-interferometry

Sergii Novikov, Igor Fodchuk, and Ivanna Yaremchyk

Doc ID: 253059 Received 02 Nov 2015; Accepted 26 Jan 2016; Posted 26 Jan 2016  View: PDF

Abstract: We study the mechanisms of forming X-ray moiré images arising under the action of one-dimensional rows of local concentrated forces at output surface of a surface of triple-crystalline LLL-interferometer for the cases of orientation of them parallel and perpendicular to the vector of diffraction. Presence of constant phase shift of one of the interfering waves in the interferometer’s analyzer results in diminishing of period, contrast and area of deforma-tion moiré fringes. It is shown that the area of efficient interaction of phase and deformation moirés depends on both the magnitude of the constant phase shift and on the magnitude and character of arrangement of local concentrated forces in rows.

Spatio-temporal characterization of pulses obtained from a high energy sub-nanosecond laser system

Jean-Claude Diels, Chengyong Feng, and Xiaozhen Xu

Doc ID: 254001 Received 16 Nov 2015; Accepted 25 Jan 2016; Posted 26 Jan 2016  View: PDF

Abstract: Spatio-temporal profiles of laser pulses, obtained from each stage of a high energy sub-nanosecond laser system, are investigated. The laser system is composed of a Q-switched Nd:YAG unstable oscillator, a chain of Nd:YAG amplifiers, a second-harmonic generator and a high energy pulse compressor based on stimulated Brillouin scattering (SBS). A curved energy front, i.e., the pulses emerging away from the beam center being gradually delayed from the center pulse, is shown to originate from the unstable oscillator. Our comparative study shows that injection-seeding will enlarge the energy front curvature, via reduction of the effective gain. After the laser amplifiers, the energy front curvature is more than doubled due to the gain saturation effect. The latter also modifies the spatial pulse width distribution. While there is a negligible pulse duration spread across the oscillator beam, the amplified pulses are found to have gradually reduced pulse duration away from the beam center. More interestingly, after the SBS pulse compression, not only the pulse width but also the delay arencompressed down. This is to our knowledge the first study of the spatio-temporal profile of SBS compressed pulse. To compare with the experiments, two numerical models are developed to simulate the evolution of spatio-temporal profiles within the Nd:YAG laser system and during the SBS pulse compression, respectively. The first model is demonstrated to reproduce the experimental results very well, while the second one predicts part of the features of the SBS compressed pulse. The limitation on the latter is discussed.

Reducing the influence of direct reflection on returnsignal detection in 3D imaging lidar system by rotatingthe Polarizing Beamsplitter

Lee Xiaobao, Wang Chunhui, yang Qu, Yunxi Li, Hailong Li, and Qi Wang

Doc ID: 254833 Received 01 Dec 2015; Accepted 25 Jan 2016; Posted 26 Jan 2016  View: PDF

Abstract: The direction rule of the laser beam travelling through a deflected polarizing beamsplitter(PBS) cube isderived. It reveals that, due to the influence of the end face reflection of the PBS, at the detector side,the emergent beam coming from the incident beam parallels to the direction of the original case withoutrotation, only a very small translation interval between them; the formula of the translation interval isalso given. Meanwhile, the emergent beam from the return signal at the detector side deflects at an angleas twice as the PBS rotation angle. The correctness has been verified by an experiment. The intensitytransmittance of the emergent beam when propagating in the PBS is hardly changed if the rotation angleless than 35 degree. In 3D imaging lidar system, by rotating the PBS cube by an angle, the direction ofreturn signal optical axis is separated from that of origin, which can decrease or eliminate the influenceof direct reflection caused by the prism end face on the target return signal detection, and it has beenchecked in experiment.

Intensity-modulating Graphene Metamaterial for Multiband Terahertz Absorption

Gao Runmei, Zongcheng Xu, Chunfeng Ding, and Jian-Quan Yao

Doc ID: 255308 Received 14 Dec 2015; Accepted 25 Jan 2016; Posted 26 Jan 2016  View: PDF

Abstract: In this paper, we design a tunable strength multiband absorber consisting of a graphene metamaterial structure and a thick dielectric interlayer deposited on a metal ground plane. We investigate the tunable conductivity properties of the graphene metamaterial and demonstrate multiband absorbers with three absorption bands using a polyimide interlayer in the 0-2.25 THz range by numerical simulation. The results show that the mix-absorptivity reached 99.8% at 1.99 THz and the absorptive strength can be tuned with the modulation depth up to 84.2%. We present a theoretical interpretation based on standing wave field, which shows that the field energy is localized inside the thicker spacer and then dissipated, effectively trapping the light in the metamaterial absorbers with negligible near-field interactions. The standing wave field theory developed here explains all the features of the multiband metamaterial absorbers and provides a profound understanding of the underlying physics.

Time dependent linearity in diffuse imaging: How effective is it to evaluate the spatial resolution by measuring the ERF?

Eduardo Ortiz-Rascón, Neil Bruce, Antonio A. Rodriguez-Rosales, and Jesus Garduno

Doc ID: 255508 Received 11 Dec 2015; Accepted 25 Jan 2016; Posted 25 Jan 2016  View: PDF

Abstract: We describe the behavior of linearity in diffuse imaging by evaluating the differences between time-resolved images produced by photons arriving at the detector at different times, two approaches are considered: Monte Carlo simulations and experimental results. The images of two complete opaque bars embedded in a transparent or in a turbid medium with a slab geometry are analyzed; the optical properties of the turbid medium sample are close to that of breast tissue. A simple linearity test was designed involving a direct comparison between the intensity profile produced by two bars scanned at the same time, and the intensity profile obtained by adding two profiles of each bar scanned one at a time. It is shown that the linearity improves substantially when short time of flight photons are used in the imaging process, but even then the non-linear behavior prevails. As the edge response function (ERF) has been used widely for testing the spatial resolution in imaging systems, the main implication of a time dependent linearity is the weakness of the linearity assumption when evaluating the spatial resolution through the ERF in diffuse imaging systems, and the need to evaluate the spatial resolution by other methods.

Superluminal, Luminal and Subluminal Non-diffracting Pulses Applied to FSO Systems: Theoretical Description

Roger Leonardo Garay Avendaño and Michel Zamboni-Rached

Doc ID: 253846 Received 12 Nov 2015; Accepted 25 Jan 2016; Posted 29 Jan 2016  View: PDF

Abstract: In this paper we show theoretically non-diffracting pulses with arbitrary peak velocities that can be suitable for data signal transmission without distortion over long distances using different techniques of signal modulation. Our results provide closed-form analytical solutions to the wave equation describing superluminal, luminal and subluminal ideal non-diffracting pulses with frequency spectra commonly used in the field of optical communications.

Optimizing Yb concentration of fiber amplifiers in the presence of transverse modal instabilities and photodarkening

Jesper Laegsgaard

Doc ID: 255807 Received 15 Dec 2015; Accepted 24 Jan 2016; Posted 26 Jan 2016  View: PDF

Abstract: The Yb concentration of double-clad optical fiber amplifiers is numerically optimized with respect to maximizing the transverse modal instability threshold in the presence of absorption arising from photodarkening. The pump cladding area is scaled with the Yb concentration to approximately maintain the pump absorption in operation. It is found that approximate analytical expressions can predict the optimized concentration levels found in numerical simulations with sufficient accuracy to be useful in fiber design.

Hysteresis compensation of photoluminescence in ZnS:Cu for non-contact shaft torque sensing

Gi-Woo Kim, Min Young Cho, and Ji Sik Kim

Doc ID: 253261 Received 03 Nov 2015; Accepted 24 Jan 2016; Posted 26 Jan 2016  View: PDF

Abstract: This paper presents a preliminary investigation of loading rate-dependent hysteresis of photoluminescence (PL) by phosphorescence quenching of copper-doped zinc sulfide (ZnS:Cu) microparticles in response to dynamic torsional loading. Precision sinusoidal torque waveforms in the frequency range of 0.5–3 Hz are used to identify the loading rate-dependent (i.e., frequency-dependent) nonlinear hysteresis phenomenon. The potential of the application of PL is demonstrated by successfully measuring the sinusoidal torque applied to a rotational shaft by evaluating the loading rate-dependent PL intensity signature using a photomultiplier tube (PMT). In addition, the potential of noncontact shaft torque sensing is demonstrated successfully by the simple compensation derived from ad hoc heuristic characterization.

Some possibilities of chemical adjustment of physical properties of azobenzene polycomplexes with metal

Irina Davidenko

Doc ID: 252675 Received 26 Oct 2015; Accepted 24 Jan 2016; Posted 25 Jan 2016  View: PDF

Abstract: The possibilities of changes of the physical properties of polymeric composites based on azobenzene by means of chemical modifications of the polycomplexes structure and composition are investigated. The main emphasis was made on the possibilities of adjustment of characteristics of electrooptical effect observed in these composites. Among the methods of chemical modification change of the type of coordination of metallic ion, change of dipole moment of the azobenzene fragment, change of length of the “spacer” connecting azobenzene fragment to main polymeric chain, introduction of the organic dyes in the azobenzene polymeric composites are considered. Demonstrated flexibility of the properties of the investigated media is important for their practical applications as information or optically active media.

Laser-driven Phosphor-converted White Light Source for Solid-state Illumination

Faiz Rahman, ANTHONY GEORGE, SARA AL-WAISAWY, Jason Wright, and Wojciech Jadwisienczak

Doc ID: 254494 Received 25 Nov 2015; Accepted 24 Jan 2016; Posted 25 Jan 2016  View: PDF

Abstract: Energy efficiency and lighting quality considerations are driving research into laser-pumped white light sources. Laser diodes as pump sources for down-conversion phosphors, promise freedom from ‘droop’ that adversely affects the efficiency of light-emitting diodes. High intensity laser diode-pumped light sources for applications such as search lights and automobile headlights have been demonstrated recently. Our paper describes the design and construction of a domestic/office type solid-state luminaire driven by light from an integrated violet laser diode module. A trichromatic phosphor made from a blend of separate europium-containing rare-earth phosphors was used as the down-conversion medium. Mechanical and optical design of the reflector as well as the phosphor plate are described. Characteristics of both the pump light and the down-converted light are also described. Our studies also looked at the variation of chromaticity coordinates with variation in pump power and the effect of laser speckle on the lamp’s light output. Finally, there is a brief discussion of energy conversion efficiency and longevity considerations, comparing pumping with light-emitting diodes versus pumping with laser diodes.

Ambient temperature-independent dual-band mid-infrared radiation thermometry

You Lv, Xin He, Zhong-Hui Wei, Zhiyuan Sun, and Songtao Chang

Doc ID: 254603 Received 26 Nov 2015; Accepted 24 Jan 2016; Posted 25 Jan 2016  View: PDF

Abstract: For temperature measurement of targets at low temperature, dual-band radiation thermometry using mid-infrared detectors has been investigated extensively. However, the accuracy is greatly affected by the reflected ambient radiation and stray radiation which depend on the ambient temperature. To ensure the measurement accuracy, an improved dual-band measurement model is established by considering the reflected ambient radiation and the stray radiation. Afterwards the effect of ambient temperature fluctuation on temperature measurement is further analyzed in detail. Experimental results of measuring a grey-body confirm that the proposed method yields high accuracy at varying ambient temperatures. This method provides a practical approach to remove the effect of ambient temperature fluctuation on temperature measurement.

Methods of Phase Reconstruction for Time-Averaging Electronic Speckle Pattern Interferometry (ESPI)

Tatiana Statsenko, Wilfried Kausel, Thomas Moore, and Vasileios Chatziioannou

Doc ID: 246944 Received 06 Aug 2015; Accepted 22 Jan 2016; Posted 22 Jan 2016  View: PDF

Abstract: Electronic speckle pattern interferometry is useful for the qualitative depiction of the deformation profile of harmonically vibrating objects. However, extending the process to achieve quantitative results requires unwrapping the phase in the interferogram, which contains significant noise due to the speckle. Two methods to achieve accurate phase information from time-averaged speckle pattern interferograms are presented. The first is based on a direct inverse of the regions within corresponding phase intervals and the second is based on optimization of four independent parameters. The optimization method requires less time than more commonly used algorithms and shows higher precision of the resulting surface displacement.

Better 3D inspection with structured illumination: speed

Zheng Yang, Alexander Bielke, and gerd haeusler

Doc ID: 252005 Received 14 Oct 2015; Accepted 22 Jan 2016; Posted 22 Jan 2016  View: PDF

Abstract: 3D inspection in the factory requires precision and speed. While customers can select from a wide spectrum of high-precision sensors, the real challenge today is “speed”. We discuss the speed of 3D-sensors in a general context to provide an understanding of why high resolution 3D sensors deliver significantly fewer 3D-points per second than the available camera pixel-rates suggest. The major cause of the low speed is the large number E of required exposures, due to the unavoidable depth scanning. Through the example of structured-illumination microscopy (SIM), we demonstrate how E can be minimized without reducing precision. We further demonstrate a lateral scanning strategy that operates at significantly higher speed for macroscopic measurement by avoiding explicit depth scanning. This paper is a follow up of an earlier paper about the precision limits of SIM and exploits earlier results.

Ultracompact polarization rotator in an asymmetric single dielectric loaded rib waveguide

Chih-Wei Hsu, Yung-ChenYung-Chen Cheng, HUNG-YUAN LIN, and JHEN-YU Chen

Doc ID: 252106 Received 16 Oct 2015; Accepted 21 Jan 2016; Posted 22 Jan 2016  View: PDF

Abstract: A compact polarization rotator (PR) with an asymmetric single dielectric loaded rib waveguide is proposed. The core of the waveguide is designed to have a specific rectangular configuration. The waveguide requires only a single asymmetrical dielectric loading on the core to complete the polarization conversion. The optical field is confined to the vicinity of the core center, which matches the optical field of the input/output waveguides. The transition loss of the PR is as low as 0.03–0.21 dB/facet without the taper or offset schemes. Such results can facilitate the fabrication of a PR with an operating length of 10 μm. In a comprehensively designed PR with a length of 7.92 μm, a –1 dB bandwidth for polarization conversion efficiency (PCE) is greater than 100 nm at the communicating wavelength of 1550 nm. The loading width and thickness with ±20 nm tolerance exhibit −0.87 and −0.49 dB changes in PCE, respectively.

On the modeling of hyperspectral remote-sensing reflectance of high-sediment-load waters in the Vis-SWIR domain

Zhongping Lee, Shaoling Shang, Gong Lin, Chen Jun, and David Doxaran

Doc ID: 248519 Received 13 Nov 2015; Accepted 21 Jan 2016; Posted 22 Jan 2016  View: PDF

Abstract: We evaluated three key components in modeling hyperspectral remote sensing reflectance in the visible to shortwave-infrared (Vis-SWIR) domain of high-sediment-load (HSL) waters, which are: the relationship between remote-sensing reflectance (Rrs) and inherent optical properties (IOPs), absorption coefficient spectrum of pure water (aw) in the IR-SWIR region, and the spectral variation of sediment absorption coefficient (ased). Results from this study indicate that it is necessary to use a more generalized Rrs-IOP model to describe the spectral variation of Rrs of HSL waters from Vis to SWIR, otherwise it may result in spectrally distorted Rrs spectrum if a constant model parameter is used. For hyperspectral aw in the IR-SWIR domain, the values reported in Kou et al (1993) provided a much better match with the spectral variation of Rrs in this spectral range compared to that of Segelstein (1981). For ased spectrum, an empirical ased spectral shape derived from sample measurements is found working much better than the traditional exponential-decay function of wavelength in modeling the spectral variation of Rrs in the visible domain. These results would improve our understandings of the spectral signatures of Rrs of HSL waters in the Vis-SWIR domain and subsequently improve the retrieval of IOPs from ocean color remote sensing, which could subsequently help the estimation of sediment loading of such waters. Limitations in estimating chlorophyll concentration in such waters are also discussed.

Spoof surface plasmon polaritons based on ultrathin corrugated metallic grooves at terahertz frequency

genquan han, jing yan, Yan Liu, Yao Shao, Jie Pan, Chunfu Zhang, and Yue Hao

Doc ID: 253319 Received 04 Nov 2015; Accepted 21 Jan 2016; Posted 22 Jan 2016  View: PDF

Abstract: We investigate the dispersion properties of the ultrathin spoof plasmonic waveguide based on metal strip grooves using the finite element method. The confinement ability of the surface plasmon polaritons (SPPs) waves are influenced by the dispersion curves, which can be modulated by the structure parameters. The propagation characteristics of the subwavelength planar plasmonic waveguide ring resonator have also been studied. Furthermore, gain medium is introduced to compensate for the propagation loss of the SPPs wave in the device at terahertz frequency. It is demonstrated that gain medium provides an enhancement for the control of on/off states of the signal with the presence of pumping, which paves a way for the gain-assisted switching and lasing applications in the terahertz regime.

Atmospheric Propagation and Combining of High-Power Lasers

William Nelson, Phillip Sprangle, and Christopher Davis

Doc ID: 253759 Received 10 Nov 2015; Accepted 21 Jan 2016; Posted 22 Jan 2016  View: PDF

Abstract: In this paper we analyze the beam combining and atmospheric propagation of high-power lasers for directed-energy (DE) applications. The large linewidths inherent in high-power fiber and slab lasers cause random phase and intensity fluctuations occurring on sub-nanosecond time scales. To coherently combine these high-power lasers would involve instruments capable of precise phase control and operating at rates greater than ~10 GHz. To the best of our knowledge, this technology does not currently exist. This presents a challenging problem when attempting to phase-lock high-power lasers, which is not encountered when phase-locking low-power lasers, for example at mW power levels. Regardless, we demonstrate that even if instruments are developed that can precisely control the phase of high-power lasers; coherent combining is problematic for DE applications. The dephasing effects of atmospheric turbulence typically encountered in DE applications will degrade the coherent properties of the beam before it reaches the target. Through simulations, we find that coherent beam combining in moderate turbulence and multi-km propagation distances has little advantage over incoherent combining. Additionally, in strong turbulence and multi-km propagation ranges, we find nearly indistinguishable intensity profiles and virtually no difference in the energy on the target between coherently and incoherently combined laser beams. Consequently, we find that coherent beam combining at the transmitter plane is ineffective under typical atmospheric conditions.

Measuring vibrational motion in the presence of speckle using off-axis holography

Brandon Redding, Allen Davis, Clay Kirkendall, and Anthony Dandridge

Doc ID: 254963 Received 02 Dec 2015; Accepted 21 Jan 2016; Posted 22 Jan 2016  View: PDF

Abstract: We present a holographic laser vibrometer designed to mitigate the effects of speckle noise when measuring the vibrational motion of a rough object. We show that multiplexing the interferometric measurement across 10⁵ pixels provides a 50 dB reduction in the incoherent noise. Using a high-speed camera, this enables a displacement sensitivity of 50 fm/√Hz with a bandwidth of 12.5 kHz when measuring rough objects, representing a 20 dB improvement compared with a commercially available, single detector based laser vibrometer. Finally, we show that the holographic vibrometer system is capable of stand-off acoustic sensing by measuring the acoustic-induced vibrations of a piece of paper with sensitivity as low as 10 dB (re 20 µPa). The ability to sensitively and non-invasively measure the vibrations of arbitrary rough surfaces could enable new applications in laser vibrometry.

A Format-Independent Polarization Demultiplexing Technique for Dual Polarization Intensity Modulated Signals

Sean O Duill and Liam Barry

Doc ID: 256052 Received 18 Dec 2015; Accepted 20 Jan 2016; Posted 22 Jan 2016  View: PDF

Abstract: We show through simulations how polarization demultiplexing of dual-polarization, intensity modulated signals of arbitrary format can be performed by only using the information in Stokes space. The technique would be applicable for short range communications within data centers.

Characterization of the noise spectrum of optoelectronic oscillators in the presence of the laser frequency noise

Sajad Jahanbakht

Doc ID: 253959 Received 16 Nov 2015; Accepted 20 Jan 2016; Posted 22 Jan 2016  View: PDF

Abstract: Frequency domain formulation for computing the noise spectrum of a single loop optoelectronic oscillator (OEO) under the effect of the Laser frequency noise (LFN) based on the conversion matrix approach (CMA) is presented. The validity of this approach is verified by comparing its results regarding the phase noise of the OEO with the measurement results of a reference in the literature. By performing various simulations it is observed that the LFN-induced phase noise is approximately independent of the length of the fiber delay line at offset frequencies less than the free spectral range, i.e. the inverse of the time delay of the fiber, and at larger offset frequencies it even grows with increasing the fiber length. Furthermore it is observed that this phase noise is approximately independent of the distance between the oscillation frequency and the center frequency of the RF filter as well as the value of the small signal loop gain of the OEO. However the LFN-induced amplitude noise is affected by the distance between the oscillation frequency and the center frequency of the RF filter.

Lidar reflectance from snow at 2.05 μm wavelength asmeasured by the JPL Airborne Laser AbsorptionSpectrometer

Robert Menzies, Gary Spiers, and Joseph Jacob

Doc ID: 252978 Received 30 Oct 2015; Accepted 20 Jan 2016; Posted 22 Jan 2016  View: PDF

Abstract: We report airborne measurements of lidar directional reflectance (backscatter) from land surfaces at awavelength in the 2.05 μm CO2 absorption band, with emphasis on snow-covered surfaces in various naturalenvironments. Lidar backscatter measurements using this instrument provide insight into the capabilities oflidar for both airborne and future global-scale CO2 measurements from low Earth orbit pertinent to the NASAActive Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. Lidar measurementcapability is particularly useful when the use of solar scattering spectroscopy is not feasible for high accuracyatmospheric CO2 measurements. Consequently performance in high-latitude and winter season environments isan emphasis. Snow-covered surfaces are known to be dark in the CO2 band spectral regions. The quantitativebackscatter data from these field measurements help to elucidate the range of backscatter values that can beexpected in natural environments.

Multiple Input Multiple Output Synthetic ApertureLadar System for Wide Range Swath with HighAzimuth Resolution

Yu Tang, Bao Qin, Yun Yan, and Xing Mengdao

Doc ID: 253192 Received 10 Dec 2015; Accepted 20 Jan 2016; Posted 20 Jan 2016  View: PDF

Abstract: For the trade-off between the high azimuth resolution and the wide range swath in the single input single outputsynthetic aperture ladar(SAL) system, the range swath of the SAL system is restricted to a narrow range, this paperproposes a multiple input multiple output (MIMO) synthetic aperture ladar system. The MIMO system adopts a lowpulse repetition frequency(PRF) to avoid range ambiguity for the wide range swath, and in azimuth, adopts themulti-channel method to achieve azimuth high-resolution from the unambiguous azimuth wide-spectrum signal,processed through adaptive digital beam-forming technology. Simulation and analytical results are presented.

Performance improvement of Power-over-Fibersystem using noise-modulated laser diode

Mingjiang Zhang, Yongning Zhang, Jianzhong Zhang, Yi Liu, Ruixia Liu, Yunting Li, and Yun-cai Wang

Doc ID: 254383 Received 23 Nov 2015; Accepted 20 Jan 2016; Posted 20 Jan 2016  View: PDF

Abstract: In power over fiber system, the key limiting factor of transmission light power is stimulated Brillouin scatteringeffect, which leads to the decrease of transmission light power at the end of optical fiber. Therefore we propose andexperimentally demonstrate a broadband laser generated by noise-modulated distributed-feedback laser diode tosuppress the stimulated Brillouin scattering effect in optical fiber. Experimental results show that the linewidth ofnoise-modulated distributed-feedback laser diode broadens from 2.43MHz to 379.89MHz by increasing the noisemodulation amplitude from 0mV to 400mV. Due to the broadening of laser linewidth, the stimulated Brillouinscattering threshold raises 7.19dB and the peak power of Brillouin Stokes light reduces 40.90dB. At the same time,the output electrical power at the end of optical fiber increases 13.55dB.

Application of quantum weak measurement for glucose concentration detection

Yonghong He, Dongmei Li, Zhiyuan Shen, Yilong Zhang, Zhenling Chen, and Hui Ma

Doc ID: 255628 Received 11 Dec 2015; Accepted 20 Jan 2016; Posted 20 Jan 2016  View: PDF

Abstract: A quantum weak measurement scheme based on Mach-Zehnder interferometer was proposed to detect theconcentration of glucose, bringing this mechanism in the field of biomedical sensing for the first time. With Mach-Zehnder interferometer system we can analyze tiny phase difference between the two paths by measuringspectrum shift. We measured the concentration of glucose with weak measurement to achieve a concentrationresolution of 8.98×10-5g/L corresponding to a volume refractive index of 1.39×10-8RIU, which was more than 5times higher than the resolution achieved by conventional interference, 4.99×10-4g/L. In the detection of glucoseconcentration in blood serum of mice, a resolution of 1.0136×10-7 g/L for weak measurement was obtained.

Ho3+/Yb3+ co-doped silicate glasses for 2 μm emission performances

Junjie Zhang, Ruijie Cao, Muzhi Cai, Yu Lu, Ying Tian, Feifei Huang, and Shiqing Xu

Doc ID: 255715 Received 14 Dec 2015; Accepted 20 Jan 2016; Posted 20 Jan 2016  View: PDF

Abstract: This paper discusses a series of Ho3+/Yb3+ co-doped silicate glasses prepared by melting method. 2 μm emissions of the samples are observed under the pump of 980 nm LD. The Judd-Ofelt parameters (Ωλ) and radiative properties are calculated and analyzed; the spontaneous transition probability can reach 78.71s-1. From the fluorescence spectra, the full width at half maximum (FWHM) is approximately 165 nm, the peak absorption and emission cross-section of Ho3+ are 5.91 × 10-21 cm2 and 6.76 × 10-21 cm2, respectively. In addition, the energy transfers process of Yb3+: 2F5/2 level to Ho3+: 5I6 level is analyzed. Considering the emission properties and good thermal property, we indicate that Ho3+/Yb3+ co-doped silicate glass is a potential laser glass for efficient 2 μm laser.

A large-aperture telescope to map the CMB 10X faster

Michael Niemack

Doc ID: 254245 Received 20 Nov 2015; Accepted 19 Jan 2016; Posted 20 Jan 2016  View: PDF

Abstract: Current large-aperture cosmic microwave background (CMB) telescopes have nearly maximized the number of detectors that can be illuminated while maintaining diffraction-limited image quality. The polarization-sensitive detector arrays being deployed in these telescopes in the next few years will have roughly 10⁴ detectors. Increasing the mapping speed of future instruments by at least an order of magnitude is important to enable precise probes of the inflationary paradigm in the first fraction of a second after the big bang and provide strong constraints on cosmological parameters. This paper introduces new crossed Dragone telescope and receiver optics designs that increase the usable diffraction-limited field-of-view, and therefore the mapping speed, by over an order of magnitude to enable high efficiency illumination of >10⁵ detectors in a next generation CMB telescope.

Fluorescence characteristics of the fuel tracerstriethylamine and trimethylamine for theinvestigation of fuel distribution in IC engines

Susanne Lind, Simon Assmann, Lars Zigan, and Stefan Will

Doc ID: 252943 Received 29 Oct 2015; Accepted 19 Jan 2016; Posted 20 Jan 2016  View: PDF

Abstract: Laser-induced fluorescence based on fuel tracers like amines is a suitable measurement technique formixing studies in IC engines. Triethylamine (TEA) has been often used in gasoline IC engines before.However, no detailed fluorescence characterization for excitation at 263 or 266 nm is available.Trimethylamine (TMA) exhibits high potential as gaseous fuel tracer but also only few informationabout TMA fluorescence is available yet.A picosecond laser source combined with a streak camera equipped with a spectrograph was used todetermine the spectral fluorescence emission and the fluorescence decay time of both tracers. Thetracers were investigated at various temperatures and pressures in a calibration cell with nitrogen asbath gas. The results provide an in-depth understanding of the fluorescence characteristics of bothtracers and allow assessing their application for the investigation of fuel distribution in IC engines.

High contrast pattern reconstructions using a phase-seeded point CGH method

Richard McWilliam, Alan Purvis, N Seed, Gavin Williams, and Joshua Cowling

Doc ID: 248764 Received 01 Sep 2015; Accepted 19 Jan 2016; Posted 19 Jan 2016  View: PDF

Abstract: A major challenge encountered in digital holography applications is the need to synthesize computer-generated holograms (CGH) that are realizable as phase-only elements while also delivering high quality reconstruction. This trade-off is particularly acute in high-precision applications such as photolithography where contrast typically must exceed 0.6. A seeded-phase point method is proposed to address this challenge, whereby patterns composed of fine lines that intersect and form closed shapes are reconstructed with high contrast whilst maintaining a phase-only CGH. The method achieves superior contrast to that obtained by uniform or random seeded-phase methods while maintaining computational efficiency for large area exposures. It is also shown that binary phase modulation achieves similar contrast performance with benefits for the fabrication of simpler diffractive optical elements.

Random sub-Nyquist polarimetric modulator

Andres Asensio Ramos

Doc ID: 251340 Received 02 Oct 2015; Accepted 19 Jan 2016; Posted 19 Jan 2016  View: PDF

Abstract: We show that it is possible to measure polarization with a polarimeter that gets rid of the seeing while still measuring at a frequency well below that of the seeing.We study a standard polarimeter made of two retarders and a beamsplitter. The retarders are modulated at thefrequency of the seeing. However, we assume that the camera is slow, so that our measurements are time integrations of these modulated signals. In order to recoverthe time variation of the seeing and obtain the Stokes parameters, we use the theory of compressed sensing to solve the demodulationby impose a sparsity constraint on the Fourier coefficients of the seeing.We demonstrate the feasibility of this sub-Nyquist polarimeter using numerical simulations, both in the case without noise and with noise. We show that a sensible modulation scheme is obtained by randomly changing the fast axis of themodulators or their retardances in specific ways. We finally demonstrate that the value of the Stokes parameters can be recovered withgreat precision at almost maximum efficiency, although it slightly degrades when the signal-to-noise ratio of the observations increase, a consequenceof the multiplexing under the presence of photon noise.

Photon-conversion evaluation of Eu3+ in borate glass system

Lin Hai, Y.M. Tian, L.F. Shen, and Edwin Yue Bun Pun

Doc ID: 252270 Received 19 Oct 2015; Accepted 18 Jan 2016; Posted 19 Jan 2016  View: PDF

Abstract: Photon conversion is exhibited in borate (LKZBSB) glass system containing Eu3+, and the enhanced characteristic emissions of Eu3+ with the codoping of Ce3+ have been verified. Large Judd-Ofelt intensity parameter Ω2 of Eu3+ indicates a high asymmetrical and strong covalent environment around rare earth (RE) ions in LKZBSB glasses and spontaneous emission probability and maximum emission cross section of the dominant 5D0¬7F2 transition were derived to be 370 s-1and 1.28×10−21 cm2, respectively, revealing the potential UV¬Visible photons-conversion capacity of Eu3+. Absolutely quantitative evaluation illustrates that Eu3+ is a favourable photon-conversion center to achieve high photon-conversion efficiency regardless of cost, and the addition of Ce3+ is beneficial to realizing effective red emission of Eu3+ which possesses commercial value by decreasing the dopant of expensive europium compounds . As an expectation, this photon-conversion LKZBSB glass system can promote the development of photon down-conversion layer for solar cells, which are particularly used in outer space with intense UV radiation.

Encoded Errors Calibration for Coded Apertures Spectrometer Based on Deconvolution

Yihui Wu, Mingbo Chi, Dandan Ge, Wenchao Zhou, Yongshun Liu, and peng hao

Doc ID: 254831 Received 30 Nov 2015; Accepted 18 Jan 2016; Posted 19 Jan 2016  View: PDF

Abstract: The principle of the 2-D coded apertures spectrometer is described in this paper. The crosstalk of adjacent rows which is caused by the optical system’s Point Spread Function (PSF) and the non-uniform illumination of the apertures are the main source of the system decoded errors. Through the analysis of the affection of the crosstalk and the non-uniform illumination on the decoded spectrum, the encoding matrix is modified. Based on the new encoding equation, an algorithm using the Gold’s deconvolution method is proposed to remove the crosstalk of the adjacent rows. In the end, we evaluated the effect of this method through a series of contrast experiments.

Generalized phase-shifting algorithms: Error analysis and minimization of noise propagation

Gastón Ayubi, Cesar Perciante, J. Matias Di Martino, Jorge Flores, and Jose Ferrari

Doc ID: 252976 Received 02 Nov 2015; Accepted 18 Jan 2016; Posted 19 Jan 2016  View: PDF

Abstract: Phase-shifting is a technique for phase retrieval that requires a series of intensity measurements with certain phase-steps. The purpose of the present work is threefold: Firstly we present a new method for generating general phase-shifting algorithms with arbitrarily spaced phase-steps. Secondly, we study the conditions for which the phase-retrieval error due to phase-shift miscalibration can be minimized. Thirdly, we study the phase extraction from interferograms with additive random noise, and deduce the conditions to be satisfied for minimizing the phase-retrieval error. Algorithms with unevenly spaced phase-steps are discussed under linear phase-shift errors and additive Gaussian noise, and simulations are presented.

Generalized design of a zero-geometric-loss,astigmatism-free, modified four objective multipassmatrix system

Yin Guo, Liqun Sun, Zheng Yang, and Zilong Liu

Doc ID: 253167 Received 02 Nov 2015; Accepted 18 Jan 2016; Posted 19 Jan 2016  View: PDF

Abstract: We describe the generalized parametric construction of the modified four-objective multipass matrix system(MMS) in this study. We utilize an optical system comprising four asymmetrical spherical mirrors to improve thealignment process. The use of a paraxial equation for the design of the front transfer optics yields the initialcondition for the modeling of our MMS. A ray tracing simulation is performed to calculate the significant aberrationof the system (astigmatism). Based on the calculated meridional and sagittal focus positions, the complementaryfocusing mirror is easily designed to provide an output beam free of astigmatism. An example of a 108-transitmultipass system (5 × 7 matrix arrangement) with a relatively larger numerical aperture source (xenon lightsource) is presented. The whole system exhibits zero theoretical geometrical loss when simulated with Zemaxsoftware. The MMS construction strategy described in this study provides an anastigmatic output beam and thegeneralized approach to design a controllable matrix spot pattern on the field mirrors. Asymmetrical reflectivemirrors aid in aligning the whole system with high efficiency. With the generalized design strategy in terms ofoptics configuration and asymmetrical fabrication method in this paper, other kinds of multipass matrix systemcoupled with different sources and detector systems can also be achieved.

A Robust Method to Improve the Quality ofShearographic Phase Maps Obtained in HarshEnvironments

Analucia Vieira Fantin, Daniel Willemann, Mauro Benedet, and Armando Albertazzi Gonçalves Júnior

Doc ID: 253550 Received 11 Nov 2015; Accepted 18 Jan 2016; Posted 19 Jan 2016  View: PDF

Abstract: This paper presents a new approach to improve the quality of shearographic phase maps acquired in a harshenvironment. During in field nondestructive inspections, the presence of higher disturbances, mainly vibrations,can introduce unknown phase deviations in the sequence of shearographic images. This paper presents a differentapproach that combines the N-dimensional Lissajous Algorithm [8] and the concept of Phase of Differences [9] toimprove the quality of phase maps. The concept is compared to another two methods. Results, advantages anddifficulties of each method are also presented and discussed by using real fringe maps.

Image Fusion via Non-Local Sparse K-SVD Dictionary Learning

Ying Li, Fangyi Li, Bendu Bai, and Qiang Shen

Doc ID: 253148 Received 02 Nov 2015; Accepted 18 Jan 2016; Posted 22 Jan 2016  View: PDF

Abstract: Image fusion aims to merge two or more images captured via various sensors of the same scene to construct a more informative image by integrating their details. Generally, such integration is achieved through the manipulation of the representations of the images concerned. Sparse representation plays an important role in the effective description of images, offering a great potential in a variety of image processing tasks, including image fusion. Supported by sparse representation, in this paper, an approach for image fusion by the use of a novel dictionary learning scheme is proposed. The non-local self-similarity property of the images is exploited not only in the stage of learning the underlying description dictionary but during the process of image fusion. In particular, the property of non-local self-similarity is combined with traditional sparse dictionary [1], resulting in an improved learned dictionary, that is hereafter referred to as the non-local sparse K-SVD (NL_SK_SVD) dictionary. The performance of the NL_SK_SVD dictionary is applied for image fusion using simultaneous orthogonal matching pursuit framework. The proposed approach is evaluated with image fusion involving different types of image, and compared with a number of alternative image fusion techniques. The resultant superior fused images using the present approach demonstrates the efficacy of the NL_SK_SVD dictionary in sparse image representation.

Photodiode based Cutting Tear Sensor for NIR Lasers

Benedikt Adelmann, Max Schleier, Benedikt Neumeier, and Ralf Hellmann

Doc ID: 253947 Received 16 Nov 2015; Accepted 18 Jan 2016; Posted 22 Jan 2016  View: PDF

Abstract: We report on a photodiode based sensor system to detect cutting tears during laser cutting with a fiber laser. An InGaAs diode records the thermal radiation from the process zone with a ring mirror and optical filter arrangement mounted between collimation unit and cutting head. The photodiode current is digitalized with a sample rate of 20 kHz and filtered with a Chebyshev Type I filter. From the measured signal during the piercing a threshold value is calculated. When the diode signal exceeds this threshold during cutting a cutting tear is indicated. This method is applied to sensor signals from cutting mild steel, stainless steel and aluminum as well as different materials thicknesses and also laser flame cutting and showing the possibility to detect cutting tears in a broad variety of applications. In a series of 83 incomplete cuts every cutting tear is successfully detected (alpha error of 0 %) while no cutting tear is reported in 266 complete cuts (beta error of 0 %). This remarkable high detection rate and low error rate, the possibility to work with different materials and thicknesses in combination with the easy mounting of the sensor unit also to existing cutting machines highlight the enormous potential for this sensor system in industrial applications.

Helical long-period grating formed in a thinned fiber and its application to refractometric sensor

Hongpu Li and Peng Wang

Doc ID: 253987 Received 17 Nov 2015; Accepted 17 Jan 2016; Posted 19 Jan 2016  View: PDF

Abstract: A new kind of helical long-period grating (HLPG) written by using CO2 laser is proposed and experimentally demonstrated, in which a sapphire tube (to be used as a miniature oven with a constant temperature inside) is specially designed and utilized in place of the commonly-used ZnSe focused-lens. The proposed method allows to fabricate a helical in a thinned fiber with a diameter smaller than several tens of micrometer. As an application of this kind of HLPG, a novel fiber sensor that allows for temperature-insensitive measurement of the refractive index is proposed and experimentally demonstrated, which is based on utilization of two cascaded HLPGs but with different transverse diameters.

Morphological processing of ultraviolet emissions of electrical corona discharge for analysis and diagnostic use

Andrew Moore and MATTHEW schubert

Doc ID: 250902 Received 28 Sep 2015; Accepted 17 Jan 2016; Posted 19 Jan 2016  View: PDF

Abstract: Electron cascades from electrical discharge produce secondary emissions from atmospheric plasma in the ultraviolet band. For a single point of discharge, these emissions exhibit a stereotypical discharge morphology, with latent information about the discharge location. Morphological processing can uncover the location and therefore can have diagnostic utility.

High birefringence photonic crystal fiber polarization filter based on Surface plasmon resonance

Guowen An, Shuguang Li, Xin Yan, Zhenyu Yuan, and Xuenan Zhang

Doc ID: 253591 Received 09 Nov 2015; Accepted 16 Jan 2016; Posted 19 Jan 2016  View: PDF

Abstract: In this paper, we designed a C2v symmetry structured photonic crystal fiber (PCF) with triangular lattice and Au filled air holes. FEM method is used to analysis the dispersion and loss characteristics of the core mode and the surface plasmon mode of the metal wire. In this work, we found that the positions of resonance peaks and the resonance strength of core mode and surface plasmon mode can be well adjusted by changing the pitch between the cladding air holes and the diameters of the air holes or metal wires around the core. By optimizing the parameters of the fiber structure, a polarization filter at the communication band is designed. At the wavelength of 1.31µm which locates in the communication band, the fundamental mode in X-pol can be filtered with the diameter of the metal wire d m = 1.2 µm. When d m = 1.4 µm, the fundamental mode in Y-pol can be filtered at the wavelength of 1.55 ¦Ìm which also locates in the communication band. Compared with the ordinary single-polarization and single-modephotonic crystal fiber, the fiber we proposed in this paper can selectively filter out the polarized light in one direction by adjusting the wire diameter. It is meaningful for the development of the polarization filter in the communication band.

Simultaneous imaging of fuel vapor mass fraction and gas-phase temperature inside gasoline sprays using two-line excitation tracer planar laser-induced fluorescence (TPLIF)

Lars Zigan, Johannes Trost, and Alfred Leipertz

Doc ID: 252902 Received 29 Oct 2015; Accepted 15 Jan 2016; Posted 19 Jan 2016  View: PDF

Abstract: This paper reports for the first time on the simultaneous imaging of the gas-phase temperature and fuel vapor mass fraction distribution in a direct-injection spark-ignition (DISI) spray under engine relevant conditions using tracer planar laser-induced fluorescence (TPLIF). For measurements in the spray, the fluorescence tracer 3-pentanone is added to the non-fluorescent surrogate fuel iso-octane, which is excited quasi-simultaneously by two different excimer lasers for 2-line excitation LIF. The gas-phase temperature of the mixture of fuel vapor and surrounding gas and the fuel vapor mass fraction can be calculated from the two LIF- signals. The measurements are conducted in a high temperature high-pressure injection chamber. The fluorescence calibration of the tracer was executed in a flow cell and extended significantly compared to the before known database. A detailed error analysis for both, calibration and measurement is provided. Simultaneous single-shot gas-phase temperature and fuel vapor mass fraction fields are processed for the assessment of cyclic spray fluctuations.

A Semi Analytical Approach to Study the LossCharacteristics of a Symmetrical MultilayeredPlasmonic Waveguide

Rajib Chakraborty and bapita roy

Doc ID: 253349 Received 06 Nov 2015; Accepted 15 Jan 2016; Posted 26 Jan 2016  View: PDF

Abstract: A metal waveguide of finite width and thickness surrounded by a dielectric provides increased propagationlength of the surface plasmon polarition and are therefore called Long Range Surface Plasmon Polariton (LRSPP).In this work, a new structure is proposed by modifying the refractive index of the dielectric surroundingthe metal waveguide, leading to further improvement of the propagation length. It is shown that when the singledielectric surrounding is replaced by a multilayered surrounding where each layer have different thicknessesand refractive index, the propagation loss gets reduced leading to increased propagation length of the LR-SPP.The propagation loss is calculated semi-analytically from the FWHM of the Lorentzian peak obtained in the plotof excitation efficiency of such waveguide for different values of propagation constant. Before doing thiscalculation, the 2D variation of refractive index is first converted into 1D effective refractive index. All the stepsof analysis are discussed in details and wherever necessary the calculated results are matched with similarresults of other researchers.

Tuning of a high magnification compact parabolic telescope for cm-scale laser beams

Matteo Tacca, Fiodor Sorrentino, Christelle Buy, Matthieu Laporte, Gabriel Pillant, Eric Genin, Paolo La Penna, and Matteo Barsuglia

Doc ID: 252603 Received 29 Oct 2015; Accepted 14 Jan 2016; Posted 19 Jan 2016  View: PDF

Abstract: Off-axis parabolic telescopes, widely used in astronomy and laser optics, do not introduce aberrations, but they are very sensitive to misalignments. We present a detailed method to align a high magnification off-axis afocal parabolic telescope. The method is composed of two steps: an initial pre-alignment using autocollimators, followed by a fine tuning with a collimated laser beam. Due to the large telescope magnification, the outcoming beam cannot be measured without being re-focalized. The beam is therefore reflected on a flat mirror and sent back through the telescope. This \textit{double-pass} configuration allows the measurement of the beam quality without the need for large additional optics. In the fine-tuning step, a numerical simulation is also used to identify the degrees of freedom to be adjusted. The experimental results presented are obtained with one of the mode-matching parabolic telescopes of the gravitational-wave interferometric detector Advanced Virgo.

High resolution Fourier hologram synthesis fromphotographic images through computing the light field

Ni Chen, Zhenbo Ren, and Edmund Lam

Doc ID: 254379 Received 23 Nov 2015; Accepted 14 Jan 2016; Posted 14 Jan 2016  View: PDF

Abstract: We present a technique for synthesizing the Fourier hologram of a three-dimensional scene from its lightfield. The light field captures the volumetric information of an object, and an important advantage is thatit does not require coherent illumination, as in conventional holography. In this work, we show howto obtain a hight-resolution digital hologram with the light field obtained from a series of photographicimages captured along the optical axis. The method is verified both by simulations and experimentallycaptured light field.

Jones-matrix mapping of complex degree of mutual anisotropy of birefringent protein networks during the differentiation of myocardium necrotic changes

Yuriy Ushenko, Victor Bachynskyi, Olexander Vanchulyak, Olexander Dubolazov, Maryna Garazdyuk, and Vova Ushenko

Doc ID: 253115 Received 02 Nov 2015; Accepted 14 Jan 2016; Posted 14 Jan 2016  View: PDF

Abstract: The theoretical background of azimuthally stable method of Jones-matrix mapping of histological sections of biopsy of myocardium tissue on the basis of spatial frequency selection of the mechanisms of linear and circular birefringence is presented. The diagnostic application of a new correlation parameter – complex degree of mutual anisotropy – is analytically substantiated. The method of measuring coordinate distributions of complex degree of mutual anisotropy with further spatial filtration of their high- and low-frequency components is developed. The interconnections of such distributions with parameters of linear and circular birefringence of myocardium tissue histological sections are found. The comparative results of measuring the coordinate distributions of complex degree of mutual anisotropy formed by fibrillar networks of myosin fibrils of myocardium tissue of different necrotic states – dead due to coronary heart disease and acute coronary insufficiency are shown. The values and ranges of change of the statistical (moments of the 1st – 4th order) parameters of complex degree of mutual anisotropy coordinate distributions are studied. The objective criteria of differentiation of cause of death are determined.

Magnetorheological finishing of chemical-vapor–deposited zinc sulfide via chemically and mechanically modified fluids

sivan salzman, Henry Romanofsky, Lucca Giannechini, Stephen Jacobs, and John Lambropoulos

Doc ID: 253287 Received 03 Nov 2015; Accepted 13 Jan 2016; Posted 14 Jan 2016  View: PDF

Abstract: We describe the anisotropy in the material-removal rate (MRR) of the polycrystalline, chemical-vapor–deposited (CVD) zinc sulfide (ZnS). We define the polycrystalline anisotropy via microhardness and chemical erosion tests for four crystallographic orientations of ZnS: (100), (110), (111), and (311). Anisotropy in the MRR was studied under magnetorheological finishing (MRF) conditions. Three chemically and mechanically modified magnetorheological (MR) fluids at pH values of 4, 5, and 6 were used to test the MRR variations among the four single-crystal planes. When polishing the single-crystal planes and the polycrystalline with pH 5 and pH 6 MR fluids, variations were found in the MRR among the four single-crystal planes and surface artifacts were observed on the polycrystalline material. When polishing the single-crystal planes and the polycrystalline with the modified MR fluid at pH 4, however, minimal variation was observed in the MRR among the four orientations and a reduction in surface artifacts was achieved on the polycrystalline material.

Generation of optical vortex dipole from superposition of two radially sheared Gaussian beams

Dinesh Naik, Pradeep Tagavula, and Nirmal Viswanathan

Doc ID: 253003 Received 30 Oct 2015; Accepted 13 Jan 2016; Posted 13 Jan 2016  View: PDF

Abstract: We propose a distinct concept on the generation of optical vortex through the coupling between the amplitude and phase gradients of the superposing beams. For the proof-of-concept demonstration, we propose a simple free-space optics recipe for the controlled synthesis of an optical beam with a vortex dipole by superposing two radially sheared Gaussian beams. The experimental demonstration using a Sagnac interferometer introduces the desired amount of radial shear and linear phase between the two out-of-phase Gaussian beams to create a vortex pair of opposite topological charge in the superposed beam. Flexibility to tune their location and separation using the choice of direction of the linear phase and the intensity ratio of the superposing beams has potential applications in optical tweezers and traps utilizing the local variation in angular momentum across the beam cross section.

Miniature anastigmatic spectrometer design with aconcave toroidal mirror

He Chen, Jianing Dong, Yinchao Zhang, Chen Siying, and Pan Guo

Doc ID: 250713 Received 23 Sep 2015; Accepted 13 Jan 2016; Posted 14 Jan 2016  View: PDF

Abstract: An advanced optical design for a low-cost and astigmatism-corrected spectrometer with a high resolution is presented. Thetheory and method of astigmatism correction are determined with the use of a concave toroidal mirror. The performancesof a modified spectrometer and a traditional spectrometer are compared, and the analysis is verified. Experimentally, thelimiting resolution of our spectrometer is 0.1 nm full-width at half-maximum (FWHM), as measured for 579.1 nm.

Radiative transfer simulations of the two-dimensional ocean glint reflectance and determination of the sea surface roughness

Zhenyi Lin, Wei Li, Charles Gatebe, Rajesh Poudyal, and Knut Stamnes

Doc ID: 251883 Received 13 Oct 2015; Accepted 12 Jan 2016; Posted 12 Jan 2016  View: PDF

Abstract: An optimized Discrete-Ordinate Radiative Transfer model (DISORT3) with a pseudo two-dimensional bidirectional reflectance distribution function (BRDF) is used to simulate and validate ocean glint reflectances at an infrared wavelength (1,036 nm) by matching model result with a complete set of BRDF measurements obtained from the NASA Cloud Absorption Radiometer (CAR) deployed on an aircraft. The surface roughness is then obtained through a retrieval algorithm and is used to extend the simulation into the visible spectral range where diffuse reflectance becomes important. In general, the simulated reflectances and surface roughness information are in good agreement with the measurements, and the diffuse reflectance in the visible, ignored in current glint algorithms, is shown to be important. The successful implementation of this new treatment of ocean glint reflectance and surface roughness in DISORT3 will help improve glint correction algorithms in current and future ocean color remote sensing applications.

Far-field head-media optical interaction in heat-assisted magnetic recording

Ruoxi Yang, Paul Jones, Timothy Klemmer, Heidi Olson, Deming Zhang, Tyler Perry, Huaqing Yin, Roger Hipwell, Jan-Ulrich Thiele, Huan Tang, and Mike Seigler

Doc ID: 252008 Received 14 Oct 2015; Accepted 12 Jan 2016; Posted 12 Jan 2016  View: PDF

Abstract: We have used a plane-wave expansion method to theoretically study the far-field head-media optical interaction in HAMR. For the ASTC media stack specifically, we notice the outstanding sensitivity related to interlayer's optical thickness for media reflection and magnetic layer's light absorption. With 10-nm interlayer thickness change, the recording layer absorption can be changed by more than 25%. The 2-D results are found to correlate well with full 3-D model and magnetic recording tests on flyable disc with different interlayer thickness.

Time-resolved subtraction method for measuring optical properties of homogeneous turbid media

Daniel Milej, Androu Abdalmalak, Dariusz Janusek, Mamadou DIOP, Adam Liebert, and Keith St. Lawrence

Doc ID: 253297 Received 09 Nov 2015; Accepted 12 Jan 2016; Posted 12 Jan 2016  View: PDF

Abstract: Near infrared spectroscopy is a non-invasive, optical method used primarily to monitor tissue oxygenation due to the absorption properties of hemoglobin. Accurate estimations of hemoglobin concentrations and other light absorbers requires techniques that can separate the effect of absorption from the much greater effect of light scattering. One of the most advanced methods is time-resolved near infrared spectroscopy (TR-NIRS), which measures the absorption and scattering coefficients of a turbid medium by modeling the recorded distribution times of flights of photons. A challenge with TR-NIRS is it requires accurate characterization of the dispersion caused by the system. In this study, we present a method for circumventing this problem by applying statistical moment analysis to two time-of-flight distributions measured at separated source-detector distances. Simulations based on analytical models and Monte Carlo code, and tissue-mimicking phantoms were used to demonstrate its accuracy for source-detector distances typically used in neuroimaging applications. The simplicity of the approach is well suited to real-time applications requiring accurate quantification of the optical properties of a turbid medium.

Field Tests for Round-Trip Imaging at 1.4km Distance with Change Detection and Ranging Using a Short-Wave Infrared Super-Continuum Laser

Mohammed Islam, Michael Freeman, Lauren Peterson, Kevin Ke, Agustin Ifarraguerri, Christopher Bailey, Frank Baxley, Michael Wager, Anthony Absi, James Leonard, Hyatt Baker, and Michael Rucci

Doc ID: 253683 Received 13 Nov 2015; Accepted 11 Jan 2016; Posted 12 Jan 2016  View: PDF

Abstract: Field tests have been conducted of a broadband illuminator for active hyper-spectral imaging (HSI) using a short-wave infrared super-continuum laser (SWIR-SCL). We demonstrated irradiance comparable to the sun for two-way measurements at 1.4km distance between laser and target, and we performed change detection and ranging. The SWIR-SCL outputs 64W between 1064nm and >1800nm in a nearly diffraction-limited beam with M2 < 1.3 over the wavelength range, a wall-plug efficiency of 15.7%, and power fluctuations of only ± 0.2%. For the field tests, the laser was placed in a 12-story tower, and the targets were placed on an 8’ x 8’ board 1.4km away on the ground. The beam quality was verified using a SWIR camera, and at the ground target the beam size was ~0.9m. At the 64W power level we showed adequate sensitivity to measure the returning light from a beam propagated 1.4km to the target, where the beam was diffusely reflected back to the tower.Beyond sun-equivalent illumination, the SWIR-SCL can enable new capabilities to HSI because the source can be controlled, modulated, and synchronized. For example, we demonstrate change detection and ranging in the field test environment. In change detection, the laser and camera are synchronized, and frames with the laser off are subtracted from frames with the laser on, thereby removing artifacts from background illumination, changing angles of the sun, and shadows. Change detection was performed at the 1.4km distance by placing a board or reflectors in front of the 8’ x 8’ target at different times (early morning dawn to nighttime), and we show that we can match direct solar irradiance and retrieve the reflected signal using difference imaging. Moreover, because the quasi-CW SWIR-SCL has ~0.45nsec pulses at 6.25MHz repetition rate, we could use the pulsed output for time-of-flight ranging to calculate the distance to the target. The experimental results suggest that the range resolution of our method is ~1.5cm even at the 1.4km distance.Hence, the possibility of performing HSI with active broadband illumination using the SWIR-SCL is demonstrated. To our knowledge, this is the first-ever experiment of two-way propagation of the active HSI illumination over a long distance. The 64W SWIR-SCL provides near sunlight-equivalent illumination over multiple square meters, and the laser could enable HSI 24 hours a day and even under cloud cover, as well as enhanced capabilities such as change detection and ranging.

1kHz 3.3μm Nd:YAG KaTiOAsO4 OPO system for laser ultrasound excitation of carbon fiber-reinforced plastics

Oliver Puncken, David Mendoza Gandara, Marcin Damjanic, Peter Mahnke, Michael Kalms, Ralf Bergmann, Peter Wessels, Joerg Neumann, Ulf Schnars, and Peter Peuser

Doc ID: 253750 Received 11 Nov 2015; Accepted 11 Jan 2016; Posted 13 Jan 2016  View: PDF

Abstract: We present a new laser prototype for laser ultrasonics excitation. The fundamental wavelength of a q-switched Nd:YAG laser with a repetition rate of 1kHz is converted to 3.3μm with a with a KaTiOAs4 optical parametric oscillator. The achieved pulse energy at 3.3μm is 1.7mJ and the pulse duration at the fundamental wavelength of 1.06μm had been measured to be 21ns. The ultrasonic excitation efficiency is about 3.5 times better than the efficiency of state-of-the-art CO2-lasers.

Two-dimensional trilayer grating with a metal/insulator/metal structure as a thermophotovoltaic emitter

Jinlin Song, Mengting Si, Qiang Cheng, and Zixue Luo

Doc ID: 250020 Received 28 Oct 2015; Accepted 11 Jan 2016; Posted 14 Jan 2016  View: PDF

Abstract: A thermophotovoltaic system that converts thermal energy into electricity has considerable potential forapplication in energy utilization fields, whereas intensive emission in a wide spectral and angular range remains achallenge in improving system efficiency. This study proposes the use of a 2D trilayer grating with atungsten/silica/tungsten (W/SiO2/W) structure on a tungsten substrate as a thermophotovoltaic emitter. The finitedifference time domain method is employed to simulate the radiative properties of the proposed structure. Abroadband high emittance with an average spectral emittance of 0.953 between 600 nm and 1800 nm can beobtained for both transverse magnetic and transverse electric polarized waves. In the inductance–capacitancecircuit model and dispersion relation analyses, this phenomenon is mainly considered as the combinedcontribution of surface plasmon polariton and magnetic polariton. A parametric study is also conducted on theemittance spectrum of the proposed structure, considering geometric parameters, polar angles, and azimuthalangles for both TM and TE waves. The study demonstrates that the emitter has good wavelength selectivity andpolarization insensitivity in a wide geometric and angular range.

Local RBF meshless scheme for vector radiative transfer in participating media with randomly oriented axisymmetric particles

Hong-Liang Yi, jie sun, and ping Tan

Doc ID: 255464 Received 10 Dec 2015; Accepted 11 Jan 2016; Posted 14 Jan 2016  View: PDF

Abstract: A local radial basis function meshless scheme (LRBFM) is developed to solve polarized radiative transfer in participating media containing randomly oriented axisymmetric particles, in which radial basis functions (RBFs) augmented with polynomial basis are employed to construct the trial functions, and the vector radiative transfer equation (VRTE) based on the discrete-ordinates approach is discretized directly by collocation method. The LRBFM belongs to a class of truly meshless methods which do not need any mesh or any numerical integration scheme. Performances of the LRBFM are verified with analytical solutions and other numerical results reported earlier in the literatures via five various test cases. The predicted angular distribution of brightness temperature and Stokes vector by the LRBFM agree very well with the benchmark. It is demonstrated that the LRBFM is accurate to solve vector radiative transfer in participating media with randomly oriented axisymmetric particles.

A fast optimization method based on the diffuser dot density for uniformity of the backlight module

bingle huang and Tailiang Guo

Doc ID: 251679 Received 03 Nov 2015; Accepted 11 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: We propose a fast optimization method based on the diffuser dot density (DDD) for uniformity of the backlight module (BLM). Firstly, we analyze the relationship between the emergency light efficiency and the DDD, then we construct a simulation model to acquire a serial of simulating data; Secondly, we adopt a mathematic method to profit the relationship, and a polynomial relationship is derived; Finally, we construct an algorithm to adjust the DDD and optimize the uniformity of the BLM based on the DDD. The simulation results prove that only by three times optimizing, the uniformity of the BLM can reach 85.6%, and the experimental result indicate that the algorithm proposed in the paper can improve the uniformity rapidly. The final experimental result is that the uniformity of the third optimization reach 77.4% which satisfies the target 75% in the phase of designing the BLM. Compared to the conventional optimizing method, the method can speed up the procedure and cost down the expense of developing the BLM in fabricating the liquid crystal display (LCD).

Boiling effect in liquid nitrogen directly cooled Yb3+:YAG laser

Toshimitsu Sakurai, Haik Chosrowjan, Hiroaki Furuse, Seiji Taniguchi, Toshiyuki Kitamura, Masayuki Fujita, Shinya Ishii, and Yasukazu Izawa

Doc ID: 251686 Received 21 Oct 2015; Accepted 11 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: Liquid nitrogen (LN2) behavior on the surface of excited Yb3+:YAG is investigated using fluorometry. From the time-resolved temperature variations and integrated fluorescence spectra intensity on this directly cooled Yb3+:YAG surface, we observe a phase transition of LN2 from nucleate-boiling to film-boiling. As a result of this pool boiling, good beam quality should occur when the temperature and the heat flux at an excited surface of Yb3+:YAG are below 95 K and 15.8 W/cm2, respectively. That is, the LN2 should remain in a steady state of nucleate boiling to produce good beam quality using pool boiling.

Polarization properties analysis of a periscopicscanner with three-dimensional polarization raytracingcalculus

Yufei Yang and Changxiang Yan

Doc ID: 252538 Received 09 Nov 2015; Accepted 11 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: The polarization properties of a two-axis periscopic optical scanner constituted by a pair of rotating planar mirrorshave been studied by using the three-dimensional polarization ray-tracing matrix method. The separate andcumulative matrices that define the transformation of the polarization state are obtained and expressed in terms ofthe rotation angles of two mirrors. The variations of diattenuation and retardance are investigated and graphicallyshown as functions of the rotation angles. On this basis, a further investigation about the cumulative polarizationaberrations of three different metal-coated periscopic scanners is accomplished. Finally, the output polarizationstates of the three metal-coated scanners are calculated with input beam of arbitrary polarization states, and theresults show that the aluminum film is more appropriate than gold film and silver film for the polarizationmaintainingperiscopic scanner.

Finite-difference time-domain methods to analyze ytterbium-doped Q-swithced fiber lasers

Haroldo Hattori and Abdul Khaleque

Doc ID: 254819 Received 30 Nov 2015; Accepted 11 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: Q-switched lasers are widely used in material processing, laser ranging, medicine and nonlinear optics – in particular, Q-switched lasers in optical fibers are important since they can not only generate high peak powers but can also concentrate high peak powers in small areas. In this article, we present new finite-difference time-domain methods that analyze the dynamics of Q-switched fiber lasers which are more flexible and robust than previous methods. We extend the method to analyze fiber ring lasers and compare the results with our experiments.

High sensitive surface plasmon resonance sensorutilizing long period grating with photosensitivecladding

Zhihong Li, Chen Tao, Zhaogang Zhang, Zhou Yanming, Dan Li, and Xie Zhong

Doc ID: 251657 Received 09 Oct 2015; Accepted 11 Jan 2016; Posted 12 Jan 2016  View: PDF

Abstract: In this study, we propose and investigate a novel grating-assisted surface plasmon resonance (SPR) platform basedon the silver coated long period fiber grating having photosensitive cladding (C-LPFG). We show that the SPR modeis transited from the higher EH mode with the effective refractive index (ERI) close to the surrounding refractiveindex (SRI) and is highly sensitive to the change of the SRI. Compared with the conventional SPR sensor, a muchhigher sensitivity is obtained for the novel C-LPFG based SPR sensor. The sensitivity can be further improved byreducing the fiber diameter. The numerical results show that the highest local sensitivity as high as ~4900nm/RIUand the corresponding resolution of ~2.04×10-6 RIU are achieved for the reduced silver coated C-LPFG sensor.Moreover, the Q-factor and the figure of merit (FOM) exhibit better characteristics than that of the conventionalLPFG based SPR sensor. Our findings provide insight into that the C-LPFG based SPR platform is a potentiallyimportant area to explore for biochemical sensing.

Expressing oceanic turbulence parameters by atmospheric turbulence structure constant

Yahya Baykal

Doc ID: 255862 Received 15 Dec 2015; Accepted 10 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: The parameters composing oceanic turbulence are the wavelength, link length, rate of dissipation of kinetic energy per unit mass of fluid,rate of dissipation of mean-squared temperature, Kolmogorov microscale and the ratio of temperature to salinity contributions to therefractive index spectrum. The required physical entities such as the average intensity and the scintillation index in the oceanic mediumare formulated by using the power spectrum of oceanic turbulence which is described by the oceanic turbulence parameters. On theother hand, there exists a very rich archive of formulations and results for the above mentioned physical entities in atmosphericturbulence where the parameters describing the turbulence are the wavelength, the link length and the structure constant. In this paper,by equating the spherical wave scintillation index solutions in the oceanic and atmospheric turbulences, we have expressed the oceanicturbulence parameters by an equivalent structure constant used in turbulent atmosphere. Such equivalent structure constant will ease toreach the solutions of similar entities in oceanic turbulent medium by employing the corresponding existing solutions valid inatmospheric turbulent medium.

Using 5×5 integrating Dammann gratings to detect OAM states of beams with the range of -24 to +24

Shiyao FU, Tonglu Wang, Shikun ZHANG, and Chunqing GAO

Doc ID: 252892 Received 29 Oct 2015; Accepted 10 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: The 5×5 2D binary Dammann vortex grating can distribute energies among different diffraction orders equally and can realize the measurement of OAM states from -12 to +12. Here we combine 5×5 Dammann vortex grating and spiral phase plate with the order +12 or -12 together, which make the topological charge of beams in the array increase or decrease by 12. So the range of measuring OAM states can be extended from -24 to +24. We upload the holograms of such gratings on the liquid crystal spatial light modulator (LC-SLM) to do the experiment. The experimental results fit well with the simulation results. This method is also effective for multiplexing OAM beams and can be used in optical communications in the future.

Design, and Optimization of a Volume Phase Holographic Grating for Simultaneous use with RGB using Unpolarized light

Adoum Mahamat, Francesco Narducci, and Jim Schwiegerling

Doc ID: 251946 Received 15 Oct 2015; Accepted 10 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: Volume phase holographic (VPH) gratings have been designed for use in many areas of science and technology such as optical communication, optical imaging, and astronomy. In this paper, the design of a volume phase holographic grating, simultaneously optimized to operate in the red, green, and blue wavelengths, is presented along with a study of its fabrication tolerances. The grating is optimized to produce 98% efficiency at λ = 532nm and at least 75% efficiency in the region between 400nm and 700nm, when the incident light is unpolarized. The optimization is done for recording in dichromated gelatin (DCG) with a thickness of 12 μm, an average refractive index of 1.5, and a refractive index modulation of 0.022.

Unified matrix approach to the description of phase-space rotators

Andrey Gitin

Doc ID: 249615 Received 08 Sep 2015; Accepted 10 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: In optics the rotation of phase-space can be realized during light propagation through both an inhomogeneous medium with a radial gradient of refractive index and two special kinds of mirror-symmetrical optical systems suggested by Lohmann. However, the light propagation through Lohmann’s systems is being described in terms of matrix optics, but through the gradient-index medium is traditionally being described as a solution to the wave equation. The difference in these descriptions hinders understanding of the phase space rotators. Fortunately, there is a matrix description of the light propagation through the gradient-index medium too. A general description of the phase-space rotators is presented, which can be used to treat the light propagation through both Lohmann’s systems and the gradient-index medium in a unified matrix manner.

Capacity of electromagnetic communication modes in a noise-limited optical system

Myungjun Lee, Mark Allen Neifeld, and Amit Ashok

Doc ID: 250005 Received 14 Sep 2015; Accepted 10 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: We present capacity bounds of an optical system that communicates using electromagnetic waves between a transmitter and a receiver. The bounds are investigated in conjunction with a rigorous theory of degrees of freedom (DOF) in the presence of noise. By taking into account the different signal to noise ratio (SNR) levels, an optimal number of DOF, which provides the maximum capacity, is defined. In moderate SNR region, the maximum channel capacity is achieved by communicating information using exact communication modes obtained from the rigorous DOF theory. On the other hand, for very low or high SNR regions, the maximum capacity can be obtained using one less or more channels compare to the number of communicating modes given by the DOF theory. In general, the capacity is shown to increase with increasing sizes of the transmitting and receiving volumes, whereas it decreases with increasing the separation between volumes. Under the practical channel constraints of noise and available power, the capacity upper bound can be estimated by the iterative water-filling solution to determine the best power allocation into the sub-channels corresponding to the set of singular values when channel state information is known at the transmitter.

Birefringence images of polycrystalline films of human urine in early diagnostics of kidney pathology

Yuriy Ushenko, Olexander Dubolazov, Nataliya Pashkovskaya, Yyuliya Marchuk, Vova Ushenko, and Olga Novakovskaya

Doc ID: 253121 Received 02 Nov 2015; Accepted 09 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: It has been proposed the optical model of Mueller-matrix description of mechanisms of optical anisotropy of polycrystalline films ofurine, namely optical activity and birefringence. The algorithm of reconstruction of distributions of parameters - optical rotation anglesand phase shifts of the indicated anisotropy types has been elaborated. The objective criteria of differentiation of urine films taken fromhealthy donors and albuminuria patients by means of statistic analysis of such distributions have been determined. The operationalcharacteristics (sensitivity, specificity and accuracy) of Mueller-matrix reconstruction method of optical anisotropy parameters weredefined.

Time-lapse scanning surface plasmon microscopy of living adherent cells with a radially polarized beam

Françoise Argoul, Laura Streppa, Lotfi Berguiga, Boyer-Provera Elise, Cristina Martinez-Torres, Laurent Schaeffer, Juan Elezgaray, and Alain Arneodo

Doc ID: 253880 Received 13 Nov 2015; Accepted 08 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: We report on a fibered high resolution scanning surface plasmon microscope for long term imaging of living adherent cells. The coupling of a high numerical aperture objective lens and a fibered heterodyne interferometer enhances both the sensitivity and the long term stability of this microscope, allowing time-lapse recording over several days. The limit of diffraction is reached with a radially polarized illumination beam. Adherence and motility of living C2C12 myoblast cells are followed for 48 hours, revealing that the dynamics of these cells changes after 10 hours. This plasmon enhanced evanescent wave microscopy is particularly suited for investigating cell adhesion, since not only it can be performed without staining of the sample but it can also capture in real time the exchange of extracellular matrix elements between the substrate and the cells.

A Novel Transmission Line Model for Strained Quantum Well Lasers Including Carrier Transport and Carrier Heating Effects

Hooshang Ghafouri-Shiraz and Mingjun Xia

Doc ID: 254358 Received 23 Nov 2015; Accepted 08 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: The paper reports a new model for strained quantum well lasers which is based on quantum well transmission linemodelling method where effects of both carrier transport and carrier heating have been included. We have applied thisnew model and studied the effect of carrier transport on the output waveform of a strained quantum well laser both intime and frequency domains. It has been found that the carrier transport increases the turn-on, turn-off delay times anddamping of the quantum well laser transient response. Also, analysis in frequency domain indicates that the carriertransport causes the output spectrum of quantum well laser in steady state exhibits a red shift which has a narrowerbandwidth and lower magnitude. The simulation results of turning-on transients obtained by the proposed model arecompared with that obtained by the rate equation laser model. The new model has also been used to study the effects ofpump current spike on the laser output waveforms properties and it was found that the presence of current spike causes(i) wavelength red shift, (ii) larger bandwidth, (iii) reduces the magnitude and decreases the side-lobes suppression ratio(SLSR) of the laser output spectrum. Analysis in both frequency and time domains confirms that the new proposed modelcan accurately predict the temporal and spectral behaviors of strained quantum well lasers.

Investigation of field-widened Mach-Zehnder receiver to extend Fe Doppler lidar wind measurements from the thermosphere to the ground

Xinzhao Chu and John Smith

Doc ID: 250458 Received 21 Sep 2015; Accepted 08 Jan 2016; Posted 08 Jan 2016  View: PDF

Abstract: A receiver employing a field-widened Mach-Zehnder interferometer (MZI) is investigated for extending the wind measurement range of a narrowband Fe Doppler lidar operating at 372 nm from its existing measurement range in the mesosphere and lower thermosphere (MLT) down to the ground. This design uses the multiple transmitted frequencies available from the base Fe Doppler lidar in combination with a novel MZI receiver to make a measurement of the Doppler shift that rejects the influence of atmospheric parameters such as the aerosol backscatter ratio, temperature and pressure of the lidar volume and receiver parameters such as the geometric overlap, the chopper function and any other factor affecting the proportion of signal in both channels of the MZI equally. A ratio is constructed from the three frequencies and two channels of the interferometer that exhibits a measurement performance of 1.75 times the Cramer-Rao lower bound, which is comparable to the dual MZI (DMZ) while preserving the insensitivity to backscatter spectrum of the quad MZI (QMZ). In addition, we show how the use of multiple transmitted frequencies can yield a wind measurement wherein the accuracy is insensitive to optical imperfection and misalignment of the MZI or any other factor that affects the contrast. Simply adding a second surface mirror of particular thickness to the basic tilted MZI can allow the field of the MZI to be widened sufficiently for most resonance Doppler lidar receivers in operation today. Provided that the detection sensitivity in each channel is known, the original resonance-fluorescence and Rayleigh scattering signals can be recovered by simply scaling and adding the contributions from both channels. Consequently, wind and temperature from the MLT region and temperature from the Rayleigh region can be derived alongside Rayleigh Doppler wind measurement without compromise to the measurement precision. Using actual data obtained recently from a Major Research Instrumentation Fe Doppler lidar, we show the expected measurement performance and some potential scientific avenues for this embodiment of a “whole-atmosphere” lidar system.

An efficient Reconstruction Method for Ground Layer Adaptive Optics with mixed Natural and Laser Guide Stars

Roland Wagner, Ronny Ramlau, Tapio Helin, and Andreas Obereder

Doc ID: 247034 Received 30 Jul 2015; Accepted 08 Jan 2016; Posted 11 Jan 2016  View: PDF

Abstract: The imaging quality of modern ground based telescopes like the planned European Extremely LargeTelescope is affected by atmospheric turbulence. In consequence, they heavily depend on stable andhigh-performance Adaptive Optics (AO) systems. Using measurements of incoming light from guidestars, an AO system compensates for the effects of turbulence by adjusting so-called deformable mirror(s)(DM) in real-time.In this paper, we introduce a novel reconstruction method for the Ground Layer Adaptive Optics (GLAO).In the literature, a common approach to this problem is to use Bayesian inference in order to model thespecific noise structure appearing due to spot elongation. This approach leads to large coupled systemswith high computational effort. Recently, fast solvers of linear order, i.e., with computational complexityO(n), where n is the number of DM-actuators, have emerged. However, the quality of such methods typicallydegrades in low flux conditions. Our key contribution is to achieve the high quality of the standardBayesian approach while at the same time maintaining the linear order speed of the recent solvers. Ourmethod is based on performing a separate preprocessing step before applying the cumulative reconstructor(CuReD).The efficiency and performance of the new reconstructor are demonstrated using the OCTOPUS, the officialend-to-end simulation enviroment of the ESO for extremely large telescopes. For more specificsimulations we also use the MOST toolbox.

Ion-beam polishing of fused silica substrates for imaging SXR and EUV optics

Alexey Pestov, Nikolay Chkhalo, Sergey Churin, Mikhail Mikhaylenko, Vladimir Polkovnikov, Nikolay Salashchenko, and Mariya Zorina

Doc ID: 252355 Received 20 Oct 2015; Accepted 07 Jan 2016; Posted 07 Jan 2016  View: PDF

Abstract: We have studied the surface treatment of polished fused silica by neutralized Ar ions with energy 500–1500 eV and incidence angles of 0–90°. We found the next regularities: for samples that passed the standard procedure of deep polishing (initial effective roughness σeff~0.5 nm) the effective roughness decreases to the ultra-smooth level (i.e. σeff~0.25 nm in the range of spatial frequencies q=[4.9 x 10-2–63] μm-1). The effect begins to be noticeable at the material removal of 150 nm and reaches saturation at depths of removal greater than 1 μm. For supersmooth samples (σeff<0.3 nm) the effective roughness keeps the initial level at material removal down to 10s μm. The optimal ion energy range is 800–1300 eV (maximum smoothing effect), at higher energy some surface roughness degradation is observed. All the smoothing effects are observed at the incidence angle range θin=0–35°. Increasing the ion energy above 1300 eV increases the etching rate of up to 4 μm per hour (Jion= 0.8 mA/cm2), which allows for deep aspherization of sized substrates. The technique allows for manufacturing the optical elements for EUV and SXR wavelength ranges with a numerical aperture NA of up to 0.6.

Effects of Annealing Temperature on Optical, Morphological, and Electrical Characteristics of Polyfluorene-derivative Thin Films on ITO Glass Substrate

Quah Jin, Way Lim, and Zainuriah Hassan

Doc ID: 253627 Received 09 Nov 2015; Accepted 05 Jan 2016; Posted 06 Jan 2016  View: PDF

Abstract: Effects of post-deposition annealing temperature (125-200°C) towards optical, morphological, and electricalcharacteristics of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-phenylene)] end capped with dimethylphenyl groupdeposited on indium tin oxide glass substrates were investigated. Green and red-infrared photoluminescence (PL)emissions, originating from П-conjugation aggregates and keto-type defects did not attenuate intensity of blueemission peak. This suggested that the aggregates and defects might serve as local traps for radiativerecombination. In samples annealed at 125-175°C, a decreasing optical energy gap (Eg) that decreased barrierheight as well as an increasing amount of traps have increased current conduction via thermionic emission andtrap-assisted tunneling. Nonetheless, an acquisition of the largest Eg and amount of traps testified that thermionicemission was dominating current conduction, surpassing trap-assisted tunneling in sample annealed at 200°C.

Inverse problem of determining periodic surface profile oscillation defects of steel materials with an FGB sensor

Piotr Kisała and Sławomir Cięszczyk

Doc ID: 250806 Received 24 Sep 2015; Accepted 05 Jan 2016; Posted 06 Jan 2016  View: PDF

Abstract: We propose and experimentally demonstrate a method for the detection of steel material defects utilizing a fiber Bragg grating sensor. The considered defects are periodic grooves along the length of the tested steel profile. Direct measurement of the spectral reflectance characteristics of the fiber is performed, and the related inverse problem of indirect defect shape determination is solved. It has been demonstrated that the defect periodicity estimation is 2.5 mm, with an error less than 0.1. Furthermore, it has been shown that for periodic intervals on the order of 5 mm, the difference between the strain amplitude calculated using our method and the amplitude obtained via the finite element method was 1.4 mε.

Study on mechanism of CCD detector irradiated by millisecond pulse laser under functional loss

明欣 李, Guangyong JIN, Yong Tan, Ming Guo, and Pengbo Zhu

Doc ID: 252575 Received 30 Oct 2015; Accepted 04 Jan 2016; Posted 05 Jan 2016  View: PDF

Abstract: The damage mechanism on CCD detector was studied by building the experimental system of millisecond pulselaser irradiating CCD detector. The experimental results show that: the damage on CCD detector was mainly thethermal damage, along with the mechanical damage. The melting phenomenon was caused by the thermal damageso that a crater was observed on the surface of CCD detector. Caused by the melting of polysilicon electrodes andtemperature rise on silicon dioxide, the shift register impedance values were sharply reduced. Most of thesubstrate clock signals were broken and disappeared due to the melting of the channels in silicon substrate layerwhich causing function loss of CCD detector. The mechanical damage on the melting edge of CCD detectorperformed heave, the temperature gradient caused this damage. In this paper, the decrease of vertical shift registerimpedance values was consistent with the previous test results.

The Active Optics system of the VLT Survey Telescope

Pietro Schipani, Lothar Noethe, Demetrio Magrin, k kuijken, Carmelo Arcidiacono, Massimo Capaccioli, Massimo Dall'Ora, Sergio D'Orsi, Jacopo Farinato, Davide Fierro, Ronald Holzloehner, Laurent Marty, Cesare Molfese, Francesco Perrotta, Roberto Ragazzoni, Salvatore Savarese, Andrew Rakich, Gabriele Umbriaco, and Javier Argomedo

Doc ID: 252623 Received 17 Nov 2015; Accepted 04 Jan 2016; Posted 20 Jan 2016  View: PDF

Abstract: This paper describes the active optics system of the VST (VLT Survey Telescope), the 2.6-m survey telescope designed for visible wavelengths of the European Southern Observatory at Cerro Paranal, in the Atacama desert. The telescope is characterized by a wide field of view (1.42 degree diameter), leading to tighter active optics than in conventional telescopes, in particular for the alignment requirements. We discuss the effects of typical error sources on the image quality and present the specific solutions adopted for wavefront sensing and correction of the aberrations, which are based on the shaping of a monolithic primary mirror and the positioning of the secondary in 5 degrees of freedom.

Ghost Reflections of Gaussian Beams in Anamorphic Optical Systems

Rania Abd El-Maksoud

Doc ID: 252595 Received 23 Oct 2015; Accepted 03 Jan 2016; Posted 05 Jan 2016  View: PDF

Abstract: In this paper a methodology is developed to model and analyze the effect of undesired (ghost) reflections of Gaussian beams that are produced by anamorphic optical systems. The superposition of these beams with the nominal beam modulates the nominal power distribution at the recording plane. This modulation may cause contrast reduction, veiling parts of the nominal image, and/or the formation of spurious interference fringes. The developed methodology is based on synthesizing the beam optical paths into nominal and ghost optical beam paths. Similar to the nominal beam, we present the concept that each ghost beam is characterized by a beam size , wavefront radius of curvature and Gouy phase in the paraxial regime. The nominal and ghost beams are sequentially traced through the system and formulas for estimating the electric field magnitude and phase of each ghost beam at the recording plane are presented. The effective electric field is the addition of the individual nominal and ghost electric fields. Formulas for estimating Gouy phase, the shape of the interference fringes and the central interference order are introduced. As an application, analytical expressions for the formation of the interference pattern by Michelson interferometer that takes into consideration Gaussian beam ghost reflections as well as the tilt angles of the beam splitter and the compensator plates are derived. To illustrate the theory and to show its wide applicability, simulation examples that include: Mangin mirror, Michelson interferometer and black box optical system are provided.

Additional approaches to solving the phase problem in optics

Claudia Zenkova, p ryabyj, Mykhaylo Gorsky, and Alla Angelskaya

Doc ID: 252286 Received 21 Oct 2015; Accepted 03 Jan 2016; Posted 05 Jan 2016  View: PDF

Abstract: The paper presents principal approaches to diagnosing the structure forming skeleton of the complex optical field. An analysis of optical field singularity algorithms depending on intensity discretization and image resolution has been carried out. An optimal approach is chosen, which allows to bring much closer to the solution of the phase problem of localization speckle-field special points. The use of a “window” 2D Hilbert transform for reconstruction of the phase distribution of a speckle field is proposed. It is shown that the advantage of this approach consists in the invariance of a phase map to a change of the position of the kernel of transformation and in a possibility to reconstruct the structure-forming elements of the skeleton of an optical field, including singular points and saddle points. We demonstrate the possibility to reconstruct the equi-phase lines within a narrow confidence interval, and introduce an additional algorithm for solving the phase problem for random 2D intensity distributions.

Nonnormal operators in physics, a singular – vectors approach. Illustration in polarization optics

Tiberiu Tudor

Doc ID: 251359 Received 07 Oct 2015; Accepted 03 Jan 2016; Posted 06 Jan 2016  View: PDF

Abstract: The singular – vectors analysis of a general nonnormal operator defined on a finite dimensional complex vector space is given in the frame of a pure operatorial (“nonmatrix”, “coordinate-free”) approach, performed in a Dirac language. The general results are applied in the field of polarization optics, where the nonnormal operators are widespread as operators of various polarization devices. Two nonorthogonal polarization devices representative for the class of nonnormal and even pathological operators  the standard two-layer elliptical ideal polarizer (singular operator) and the three-layer ambidextrous ideal polarizer (singular and defective operator)  are analyzed in detail. It is pointed out that the unitary polar component of the operator exists and preserves, in such pathological cases too, its role of converting the input singular basis of the operator in its output singular basis. It is shown that for any nonorthogonal ideal polarizer a complementary one exists, so that the tandem of their operators uniquely determines their (common) unitary polar component.

Polarization-Phase Images of Liquor Polycrystalline Films in Diagnostics of Death Coming Prescription

Alexander Ushenko, Maryna Garazdyuk, Victor Bachynsky, Olexander Vanchulyak, Olexander Dubolazov, and Mykhaylo Gorsky

Doc ID: 253124 Received 02 Nov 2015; Accepted 02 Jan 2016; Posted 05 Jan 2016  View: PDF

Abstract: It has been suggested an optical model of generalized optical anisotropy of polycrystalline networks of albumin and globulin of liquor ofhuman brain. The polarization-phase method of spatial and frequency differentiation of linear and circular birefringence coordinatedistributions have been analytically substantiated. A set of criteria of the dynamics of changes of polarization-phase images of liquorpolycrystalline films for determination of death coming prescription has been determined.

High Output LED-based Light-engine for Profile Lighting Fixtures With High Color-uniformity Using Free-form Reflectors

Jesper Gadegaard, Thøger Jensen, Dennis Jørgensen, Peter Kristensen, Thomas Sondergaard, Thomas Pedersen, and Kjeld Pedersen

Doc ID: 250528 Received 25 Sep 2015; Accepted 01 Jan 2016; Posted 05 Jan 2016  View: PDF

Abstract: In the stage lighting and entertainment market, light engines (LEs) for lighting fixtures are often based on High Intensity Discharge (HID) bulbs. Switching to Light Emitting Diode (LED)-based light engines gives possibilities for fast switching, additive color mixing, longer lifetime and potentially better energy efficiency of systems. The lumen output of a single LED is still not sufficient to replace a HID source in high-output profile fixtures, but combining multiple LEDs can create a LE with similar output but with added complexity. This paper presents results of modeling and test of such a light engine. Custom ray-tracing software was used to design a high output RGB LED light engine with twelve Luminus CBT-90 LEDs using a dual reflector principle. The simulated optical system efficiency was 0.626 with a perfect (R = 1) reflector coating for light delivered on a target surface through the entire optical system. A profile lighting fixture prototype was created and provided an output of 6744 lumen and an efficiency of 0.412. The lower efficiency was mainly due to a non-optimal reflector coating and the optimized design is expected to reach a significantly higher efficiency.

Temporal coherence characterization of supercontinuum pulse trains using Michelson's interferometer

Rahul Dutta, Jari Turunen, Goëry Genty, and Ari Tapio Friberg

Doc ID: 253390 Received 05 Nov 2015; Accepted 30 Dec 2015; Posted 05 Jan 2016  View: PDF

Abstract: Temporal coherence properties of supercontinuum pulse trains generated in nonlinear fibers are analyzedwithin the framework of the second-order coherence theory of non-stationary light. Time-resolvedMichelson’s interference patterns are simulated, from which the full two-time mutual coherence functioncan (at least in principle) be determined experimentally. Standard time-integrated Michelson’s interferogramsare also simulated and shown to provide a rough estimate for the coherence time of the quasistationarycontribution. A simple but illustrative analytical model representing supercontinuum pulsetrains is presented and numerically simulated realizations of such pulse trains are considered.

Computational algorithms for simulations in atmospheric optics

Vladimir Lukin and Petr Konyaev

Doc ID: 253072 Received 02 Nov 2015; Accepted 30 Dec 2015; Posted 19 Jan 2016  View: PDF

Abstract: A computer simulation technique for atmospheric and adaptive optics based on parallel programming is discussed. A parallel propagation algorithm is designed and a modified spectral-phase method for computer generation of 2D time-variant random fields is developed. Temporal power spectra of Laguerre–Gaussian beam fluctuations are considered as an example illustrating the applications discussed. Implementation of the proposed algorithms using Intel® MKL and IPP libraries and NVIDIA® CUDA technology is shown to be very fast and accurate. The hardware system for the computer simulation is an off-the-shelf desktop with an Intel® Core™ i7-4790K CPU operating at a turbo-speed frequency up to 5 GHz and an NVIDIA® GeForce GTX-960 graphics accelerator with 1024 1.5 GHz processors.

Magnetic and structural changes in the near-surfaceepitaxial Y2.95La0.05Fe5O12 films after high-dose ionimplantation

Ivan Gutsuliak, Igor Fodchuk, Volodymyr Dovganyuk, Ullrich Pietsch, Oleksander Bonchyk, I. Syvorotka, Peter Lytvyn, A. KOTSYUBYNSKIY, and Nadja Pashniak

Doc ID: 253028 Received 02 Nov 2015; Accepted 30 Dec 2015; Posted 08 Feb 2016  View: PDF

Abstract: The method of magnetic force microscopy was used to study the domain structure of various-thickness epitaxialY2.95La0.05Fe5O12 iron-yttrium garnet films modified by high-dose implantation of nitrogen ions N+. The results ofmulti-crystal X-ray diffractometry were analyzed, and possible defect structure of garnets prior to and afterimplantation was identified. It was established that reduction of magnetic losses observed after high-dose ionimplantation is accompanied by essential ordering of magnetic domains on the surface of implanted films. There isa direct dependence of electromagnetic properties on the dose of implanted atoms followed by considerablesputtering and amorphization of near-surface film layer and formation of a well-defined electromagnetic structure.

Multi-class remote sensing objects recognition based on discriminative sparse representation

Xin Wang, Siqiu Shen, Chen Ning, Fengchen Huang, and Hongmin Gao

Doc ID: 252936 Received 29 Oct 2015; Accepted 29 Dec 2015; Posted 12 Jan 2016  View: PDF

Abstract: Automatic recognition of multi-class objects with various backgrounds is a big challenge in the field of remotesensing (RS) image analysis. In this paper, we propose a novel recognition framework for multi-class RS objectsbased on the discriminative sparse representation. In this framework, the recognition problem is implemented intwo stages. In the first, or discriminative dictionary learning stage, considering the characterization of remotesensing objects, the scale-invariant feature transform (SIFT) descriptor is first combined with an improvedbag-of-words (BOW) model for multi-class objects feature extraction and representation. Then, information abouteach class of training samples is fused into the dictionary learning process; by using the K-singular valuedecomposition (K-SVD) algorithm, a discriminative dictionary can be learned for sparse coding (SC). In the second,or recognition stage, to improve the computational efficiency, the phase spectrum of quaternion Fourier transform(PQFT) model is applied to the test image to predict a small set of object candidate locations at first. Then, amulti-scale sliding window mechanism is utilized to scan the image over those candidate locations to obtain theobject candidates (or objects of interest, OOI). Subsequently, the sparse coding coefficients of these candidatesunder the discriminative dictionary are mapped to the discriminative vectors that have a good ability todistinguish different classes of objects. Finally, multi-class objects recognition can be accomplished by analyzingthese vectors. Experimental results show that the proposed work outperforms a number of state-of-the-artmethods for multi-class remote sensing objects recognition.

Design and Performance Analysis of Ultra-precision Ion Beam Polishing Tool

YING LU, Xuhui Xie, and Lin Zhou

Doc ID: 252543 Received 30 Oct 2015; Accepted 28 Dec 2015; Posted 05 Jan 2016  View: PDF

Abstract: At beginning of this paper, the requirements for the ion beam polishing tool used in sub-nanometer precision process were introduced. Based on the ion beam figuring (IBF) principle, the definitive factor of the ion beam figuring capability was analyzed, and the deficiencies of the ion beam polishing tool on hand were pointed out. Based on the theoretic calculation and computer simulation, the effect of focused ion optics designing to the ion beam removal function was researched; a focused 3grids ion optics was developed and tested. Finally, a 150mm flat optics was figured. The figuring result showed that the contour error of this flat decreased from 15.58nm RMS to 0.77nmRMS. This result demonstrated that the ion beam polishing tool is very efficient to optical ion beam figuring.

Sensitivity in frequency dependent angular rotation of optical vortices

Yisa Rumala

Doc ID: 252681 Received 27 Oct 2015; Accepted 28 Dec 2015; Posted 05 Jan 2016  View: PDF

Abstract: Work is presented on robust strategies to enhance the sensitivity (and resolution) to rotation of a coherentsuperposition of optical vortices emerging from a single spiral phase plate (SPP) device when light’s opticalfrequency (or wavelength) going into the SPP device is varied. The generation of ultra-small rotationand the measurement of ultra-small rotation is discussed. Factors that affect the ability to perform precisionrotation measurements include the linewidth and stability of the input light source, number of photoncounts making position rotation measurements on the CCD detector, SPP reflectivity, length of SPPdevice, and the angular modulation frequency of the intensity pattern due to a coherent superposition ofoptical vortices in a single SPP device. The parameters to obtain high sensitivity single shot measurementand multiple measurements are discussed. Furthermore, a new scaling showing the enhancement in sensitivity(and resolution) in the standard quantum limit and Heisenberg limit is presented. It is shown thatwith experimentally realizable parameters, there is an enhancement of rotation sensitivity by at least oneorder of magnitude compared to previous rotation measurements with optical vortices. Understandingrobust strategies to enhance the rotation sensitivity in an SPP device is of importance in building compactSPP sensors such as gyroscopes, molecular sensors, thermal sensors, as well as in other areas of metrology.

Experimental dynamic deformation analysis of active stressed lap

Zhao Hongshen, Bin Fan, Zhige Zeng, and Xiaojin Li

Doc ID: 250330 Received 21 Sep 2015; Accepted 23 Dec 2015; Posted 23 Dec 2015  View: PDF

Abstract: We introduce a method to measure dynamic surface deformation of active stressed lap for the fabrication of 4m f/1.5 mirror. Lap surface accuracy working in some typical deformation velocities is put forward. Experimental results show that dynamic lap surface accuracy is worse than static surface, and dynamic surface accuracy gets worse if deformation velocity increases, while the difference is not obvious. An optimization of processing strategy is feasible through changing deformation velocity of active stressed lap depending on processing schedule. After optimizing in grinding and polishing strategy, efficiency could have an increase of 20%~30% expectantly.

Passive multi-spectral imaging polarimeter for remote atmospheric and surface studies: design based on optical coatings

Samuel Pellicori and Elliot Burke

Doc ID: 250842 Received 28 Sep 2015; Accepted 23 Dec 2015; Posted 23 Dec 2015  View: PDF

Abstract: The passive imaging polarimeter architecture is based on optical coatings and thereby avoids the complexities of currentsystems that use rotating polarizers, phase-modulating retarders, and birefringent elements. Coatings on stationary elementsseparate spectral regions and their polarized components to simultaneously produce images of the Stokes linear polarizationvector in FOVs ≥30°. Wavelength and FOV coverages are limited only by the telescope optics employed. The images arecollected in identical spectral passbands that can extend from UV to SWIR. An example relevant to remote sensing in the 360 to900 nm range is given. An on-board calibration and stability monitor is included.

Alignment error analysis of the Snapshot imaging polarimeter

Zhen Liu, Weifeng Yang, Jin Hong, Guanyuan Gong, Qing-Hao Ye, and Xiaobing Zheng

Doc ID: 250873 Received 12 Oct 2015; Accepted 23 Dec 2015; Posted 27 Jan 2016  View: PDF

Abstract: Snapshot imaging polarimeter (SIP) system is able to reconstruct Two-dimension spatial polarization information through a single interferogram. In the system, the alignment errors of the half wave plate (HWP) and the analyzer have a predominant impact on the accuracies of reconstructed complete Stokes parameters. A theoretical model for analyzing the alignment errors in the SIP system are presented in this paper. Based on this model, the accuracy of the reconstructed Stoke parameters has been evaluated by using different incident states of polarization (SOP). It is found that error Stokes components in this model cannot be neglected. A method to vary the thickness of the Savart plate for seeking the minimum condition number of the measurement matrix is demonstrated. The result shows that when the thickness of Savart plate is mm, the SIP system can effectively alleviate the perturbation introduced by the alignment error of the HWP.

Optimization of polarizer azimuth in improving signal to noise ratio in Kerr microscopy

Xiao Wang, Lian Jie, Xiao Li, Ping Li, Mengmeng Li, Ying Wang, Yuxiang liu, and X. J. Xu

Doc ID: 249075 Received 31 Aug 2015; Accepted 23 Dec 2015; Posted 25 Jan 2016  View: PDF

Abstract: The magneto optical Kerr effect (MOKE) is a widely used technique in magnetic domainimaging for its high surface sensitivity and external magnetic compatibility. Optimization ofKerr microscopy will improve the detecting sensitivity and provide high quality domain images.In this work, we provide a method to optimize the polarizer azimuth in improving the signal tonoise ratio (S/N) in longitudinal Kerr microscopy with the generalized magneto opticalellipsometry. Detailed analysis of the MOKE signal and the noise components are provided tostudy the optimum polarizer and analyzer azimuth combinations. Results show that, for a fixedpolarizer angle 1° , the laser intensity noise and the shot noise which vary with the input laserpower have the similar amplitude and decline with the analyzer azimuth increasing. When theanalyzer is set at the extinction place, the Johnson noise plays the dominate role in the totalnoise. Then the S/N are calculated to find the optimum polarizer and analyzer azimuth. Resultsshow that the optimum polarizer and analyzer azimuth combination for Permalloy is(18.35°,68.35°) under an incident angle of 45°. After that, the S/N of 200nm Permalloy atdifferent analyzer angles with the polarizer azimuth set at 18.35° is measured to verify thevalidity of the simulation results. At last, the S/N at different incident angles are calculated.Results show that the optimum incident angle of 200nm Permalloy film to improve the S/N is70.35° under the polarizer and analyzer angles set at the optimal combinations (18.35°, 68.35°).

Speckle Reduction in Laser Projection Displays through Angle and Wavelength Diversity

Trinh Tran, Xuyuan Chen, Muhammad Akram, Øyvind Svensen, and Nadeem Akram

Doc ID: 249283 Received 01 Sep 2015; Accepted 21 Dec 2015; Posted 22 Dec 2015  View: PDF

Abstract: Speckle is the main obstacle for the use of laser light sources in projection technology. This paper focuses on speckle suppression by the reduction of temporal coherence which is provided by the broad band laser light. The investigation of the effect of laser spectrum width and multiple lasers on speckle contrast is discussed. A broader spectrum width of the laser light is attained by the use of multiple semiconductor laser diodes of the broad-area. Measurements of speckle contrast with and without angle diversity are performed for two and four laser diodes. The measurement of speckle contrast for a single laser diode is also presented for comparison. The experimental results show that multiple laser diodes provide lower speckle contrast as compared to a single laser diode. Besides, it is also shown in this paper that the wavelength distribution of independent laser diodes has an effect on speckle contrast. Two different types of blue laser diodes Nichia NUB802T and Nichia NUB801E that have slightly different central wavelength were used for the measurements. Four laser diodes with a combination of two types of laser diodes offer better speckle contrast reduction than four laser diodes of the same type due to an effective broader spectrum. Additional speckle contrast reduction is achieved through the angle diversity by using the dynamic deformable mirror.

Thermal-induced transverse-mode evolution in the thermally guiding index-antiguided-core fiber

Lingchao Kong, Jianqiu Cao, Shaofeng Guo, Zongfu Jiang, and Q Lu

Doc ID: 251625 Received 12 Oct 2015; Accepted 21 Dec 2015; Posted 22 Dec 2015  View: PDF

Abstract: The transverse-mode evolution in thermally guiding (TG) index-antiguided-core (IAGc) fibers is numerically studied in this paper. With the finite-element method and thermal conduction equations, the evolution of fundamental mode with the thermal load is investigated, and four evolution stages (i.e., the cladding-confined, quasi-cladding-confined, quasi-core-confined and core-confined stages) are revealed. The thermal load thresholds corresponding to these stages are presented. Furthermore, the field evolutions of high-order modes are also investigated, and the filling factors of these modes are also discussed. The pertinent results can provide significant reference for designing TG IAGc fibers and understanding the thermal effect on the transverse mode of fibers involving index-antiguided core.

Investigation of Bend Loss in Single Mode Fibers with Ultra High Resolution Photon Counting OTDR

Gustavo do Amaral, Luis Ernesto Ynoquio Herrera, and Jean Pierre von der Weid

Doc ID: 252015 Received 28 Oct 2015; Accepted 17 Dec 2015; Posted 18 Dec 2015  View: PDF

Abstract: An intensity peak associated to fiber bending could be detected thanks to the use of an Ultra High Resolution Photon Counting OTDR setup. The peak intensity is shown to be dependent on the curvature radius and angular distance of the bend. To account for such peaks, we propose a model based on modal mismatching and coupling inside the bend region and show that the model is highly consistent with the acquired data. Combining the information of bend peak and bend loss, and taking advantage from the high dependence of the peak value with the local modal field parameter, the technique could be employed as an optical fiber local-parameter characterization method.

Far off-resonance laser frequency stabilization using multipass cells in Faraday rotation spectroscopy

Yang Li, wei quan, and Rujie Li

Doc ID: 250669 Received 24 Sep 2015; Accepted 02 Dec 2015; Posted 03 Dec 2015  View: PDF

Abstract: We proposed a far off-resonance laser frequency stabilization method by using the multipass cells in Rb Faraday rotation spectroscopy. Based on the detuning equation, if the multipass cells with several meters optical path length were used in the conventional Faraday spectroscopy, the detuning of the lock point could be extended much further from the alkali metal resonance. A plate beamsplitter was used to generate two different Faraday signals at the same time. The transmission optical path length was L=50mm and the reflected optical path length was 2L =100mm. When the optical path length doubled, the detuning of the lock points moved further away from the atomic resonance. The temperature dependence of the detuning of the lock point was also analyzed. A temperature-insensitive lock point was found near resonance when the cell temperature was between 110℃ ~130℃. We achieved an rms fluctuation of 0.9MHz/23h at the detuning of 0.5GHz. Frequency drift of 16MHz/h at the detuning of -5.6GHz and 4MHz/h at the detuning of -5.2GHz were also obtained for the transmission and reflected light Faraday signal.

Designing Spectrum-Splitting Dichroic Filters to Optimize Current Matched Photovoltaics

Alexander Miles, Byron Cocilovo, Brian Wheelwright, Robert Norwood, Wei Pan, and Douglas Tweet

Doc ID: 250604 Received 29 Sep 2015; Accepted 01 Dec 2015; Posted 22 Jan 2016  View: PDF

Abstract: We have developed an approach for designing a dichroic coating to optimize performance of current-matched multi-junction photovoltaic cells while diverting unused light. By matching the spectral responses of the photovoltaic cells and current matching them, substantial improvement to system efficiencies are shown to be possible. A design for use in a concentrating hybrid solar collector was produced by this approach, and is presented. Materials selection, design methodology, and tilt behavior on a curved substrate are discussed.

Carrier squeezing interferometry with π/4 phase shift: Phase extraction in the presence of multi-beam interference

Qun Yuan, Jinlong Cheng, Zhishan Gao, Kailiang Wang, and Liping Xu

Doc ID: 250875 Received 25 Sep 2015; Accepted 24 Nov 2015; Posted 24 Nov 2015  View: PDF

Abstract: Multi-beam interference exists when test the surfaces with high reflectivity using Fizeau interferometer. In this paper, multi-beam interference intensity was estimated as the sum of first six order harmonics using the Fourier series expansion. And then an algorithm adopting carrier squeezing interferometry with π/4 phase shift was proposed to extract the phase from multi-beam interferograms. Conditions of the necessary linear carrier in the proposed algorithm were derived to ensure the separation of the lobes of phase shift errors and the phase lobe in the frequency domain. Simulation results indicated that the phase retrieving precision is better than PV 0.008λ and RMS 0.001λ even when the reflection coefficient of the test surface is as high as 0.9 and the phase shift varies within π/4±π/20. The proposed algorithm for multi-beam interference was validated by its good performance in the experiments compared with the other algorithms, especially when the phase-shift error exists.

The reason of nonKolmogorov’s turbulence in atmosphere

Vladimir Lukin, Eugenii Nosov, Torgaev Andrey, and Nosov Victor

Doc ID: 252039 Received 16 Oct 2015; Accepted 24 Nov 2015; Posted 20 Jan 2016  View: PDF

Abstract: In present work are briefly stated results on problem of the description model of atmospheric turbulence energy on the base of experimental data obtaining in Siberia region. There are presented a row of the new unpublished studies, summarizing results of the multi-years experimental observations. The results of these investigations in the base of explanation of some effects in the problem of optical waves and atmospheric turbulence interaction. Our multi-years experimental results pointing on the possibilities of generation in the atmosphere so called coherent turbulence. At analysis of the problem authors, as a rule, came from own experimental data and understanding that that coherent turbulence there is result of the action of the self-organizing nonlinear processes, occurring in utter ambience, including in atmospheric air. There are considered experimental data, confirming effect of the decreasing of light fluctuations propagated through the coherent turbulence.

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