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Accepted papers to appear in an upcoming issue

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Studies on multiplexing recording in nickel ion dopedphotopolymer material for holographic data storageapplications

aswathy g, C. Sudha Kartha, and Rajesh C S

Doc ID: 280821 Received 15 Nov 2016; Accepted 18 Jan 2017; Posted 18 Jan 2017  View: PDF

Abstract: In the present study, a series of holographic gratings were recorded in a single location of nickel ion doped photopolymer film usingdifferent methods of multiplexing. The uniformity of their diffraction efficiency was shown to improve by using an exposure timescheduling method for holographic recording. 35 gratings were recorded in the 130μm thick photopolymer material with M# = 6.18and average diffraction efficiency of 3.24% using peristrophic multiplexing. In the next step, a combination of peristrophic andangular multiplexing was used for storing 50 gratings in the material with dynamic range of 7 and mean diffraction efficiency of2.15%.

Comparison of Chirped-Probe-Pulse and Hybrid fs/ps CARS for Combustion Thermometry

Daniel Richardson, Hans Stauffer, Sukesh Roy, and James Gord

Doc ID: 280998 Received 16 Nov 2016; Accepted 17 Jan 2017; Posted 18 Jan 2017  View: PDF

Abstract: A comparison is made between two ultrashort-pulse coherent anti-Stokes Raman scattering (CARS) thermometry techniques—hybrid femtosecond/picosecond (fs/ps) CARS and chirped-probe-pulse (CPP) fs-CARS—that have become standards for high-repetition-rate thermometry in the combustion diagnostics community. These two variants of fs-CARS differ only in the characteristics of the ps-duration probe pulse; in hybrid fs/ps CARS spectrally narrow, time-asymmetric probe pulse is used, whereas a highly chirped, spectrally broad probe pulse is used in CPP fs-CARS. Temperature measurements were performed using both techniques in near-adiabatic flames in the temperature range 1600–2400 K and for probe time delays 0–30 ps. Under these conditions, both techniques are shown to exhibit similar temperature measurement accuracies and precisions to previously reported values and to each other. However, it is observed that initial calibration fits to the spectrally broad CPP results require more fitting parameters and a more robust optimization algorithm and therefore significantly increased computational cost and complexity compared to the fitting of hybrid fs/ps CARS data. The optimized model parameters varied more for the CPP measurements than for the hybrid fs/ps measurements for different experimental conditions.

Polarization and phase shifting interferometry for arbitrary, locally varying polarization states

Sergej Rothau, Christine Kellermann, Simon Mayer, Klaus Mantel, and Norbert Lindlein

Doc ID: 281052 Received 18 Nov 2016; Accepted 17 Jan 2017; Posted 18 Jan 2017  View: PDF

Abstract: This publication presents a novel interferometric method for the simultaneous measurement of the phase and state of polarization of a light wave with arbitrary polarization, in particular it can be varying elliptical. The measurement strategy is based on variations of the reference wave, concerning phase and polarization and processing the interference patterns so obtained. With this method, that is very similar to the classical phase shifting interferometry, the general analysis of spatially variant states of polarization and their phase fronts can be done in one measurement cycle. Furthermore, the analysis of different optical elements regarding the impact on the polarization and phase of the incoming light can be realized. After the theoretical description of the method and the mathematical discussion of different algorithms, the realized measurement setup is presented. Afterwards, the accuracy of the method is discussed.

Automatic low-order aberration correction based on geometry optics for slab lasers

xin yu, Lizhi Dong, boheng lai, ping yang, Yong Liu, Qingfeng Kong, Kangjian Yang, Guomao Tang, and Bing Xu

Doc ID: 281269 Received 22 Nov 2016; Accepted 17 Jan 2017; Posted 18 Jan 2017  View: PDF

Abstract: In this paper, we present a method based on geometry optics to simultaneously correct low-order aberrations and reshape the beams of slab lasers. A coaxial optical system with three lenses is adapted. The positions of the three lenses are directly calculated based on the beam parameters detected by wave-front sensors. The initial sizes of the input beams are 1.8mm by 11mm, and peak to valley(PV) values of the wave-front range up to several tens of microns. After automatic correction, the dimensions may retain to nearly 22mm by 22mm as expected and PV values of the wave-front are less than two microns. The effectiveness and precision of this method are verified with experiments.

Least squares method for LCD characterization

Alberto Lencina, Daniel Actis, Dafne Amaya, and Gonzalo Rumi

Doc ID: 266918 Received 24 May 2016; Accepted 17 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: This paper presents a method for liquid crystal display characterization. It assumes the LCD can be considered as a polarization-changing device described by a Jones matrix plus a global phase. The Jones matrix parameters are found by a least squares minimization based on global optimization techniques. The present method avoids the need of assigning experimental values to theoretical expressions, it is robust against intensity fluctuations, does not require to fix arbitrary any sign of the parameters estimated and only one quarter wave-plate is employed. A comparative analysis of the results obtained with this method and previous ones is performed. Having completely characterized an LCD, a phase-mostly configuration is obtained and experimentally verified.

Suppressing image smear of vibration modulation transfer function for remote sensing optical camera

Jin Li and si liu

Doc ID: 279222 Received 21 Oct 2016; Accepted 17 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: In on-board photographing process of satellite cameras, the platform vibration can generate images motion,distortion and smear, which seriously affect image quality and image positioning. In this paper, we build themathematical modeling of a vibrating modulate transfer function (VMTF) for a remote sensing camera. The totalMTF of a camera is reduced by the VMTF, which means the image quality is degraded. In order for avoiding thedegeneration of the total MTF caused by vibration, we use Mn-20Cu-5Ni-2Fe (M2052) manganesecopper alloy material to fabricate a vibration isolation mechanism (VIM). The VIM can transform platformvibration energy into irreversible thermal energy by internal twin crystals structure. Experiment shows M2052manganese copper alloy material is good enough to suppress image motion below 125Hz, which is vibrationfrequency of satellite platform. Camera optical system has higher MTF after suppressing vibration of M2052material than before that.

Wavefront sensing for a Shack-Hartmann sensor using a phase retrieval based on a sequence of intensity patterns

Roghayeh Yazdani and Hamid Fallah

Doc ID: 279637 Received 27 Oct 2016; Accepted 16 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: An iterative phase retrieval method is applied to a sequence of intensity patterns obtained from a Shack-Hartmann sensor to reconstruct an unknown wavefront. The simulation results validate the proposed technique even under noisy conditions. The effects of different parameters on the reconstruction accuracy are also investigated by simulation. In addition, it is shown that this technique has a good capability for detecting the presence and location of optical vortices in the wavefront. The orientation and topological charge of the vortex are also reconstructed correctly.

Study on picosecond collinear eight Stokes Raman laser generation

Xiaoqiang Gao, meng chen, and Mingliang Long

Doc ID: 273173 Received 04 Aug 2016; Accepted 16 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: An improved approach which realised high efficiency Raman conversion for eight Stokes generation was demonstrated experimentally in this paper. A lab-built pulse-train green laser synchronously pumped a 120mm(optical distance) b-cut KGd(WO₄)₂ crystal Raman cavity which produced up to 602mW multicolor Stokes laser.The output spectra which covered 532nm-900nm spectra region was splitted by nine sperated laser lines. The output power, the Raman conversion efficiency has been improved comparing with our previously work,and the output spectra has also been extended from visible light to near infrared light.It is the first report about 862nm collinear picosecond pulse-train laser to our knowledge

Hyperfine structure studies of neutral europium transitions at 601.815 and 580.027 nm by saturation absorption spectroscopy

Pankaj Kumar, V Saini, G Purbia, Om Prakash, Sudhir Dixit, and Shankar Nakhe

Doc ID: 274569 Received 26 Aug 2016; Accepted 16 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: We report Doppler free spectroscopy of neutral europium carried out using saturation absorption technique. In the presentexperiment, Eu/Ne hollow cathode discharge is used as an atomic vapour source of europium. The Eu transition 4f7 6s2 (8S7/2o) →4f7 6s6p (8P9/2) at 601.815 nm and 4f7 5d6s (a10D13/2o) → 4f7 5d6p (z8D11/2) at 580.027 nm are investigated. The frequencyseparation between the adjacent hyperfine transitions as well as hyperfine structure constants are calculated from the obtainedexperimental spectra. The hyperfine structure constant obtained for the state 4f7 6s6p (8P9/2) are A151 = 664.8; B151 = 293.5 MHzand for state 4f7 5d6p (z8D11/2), the values are A151 =7.6; B151 = -60. These obtained values are in good agreement with the resultsreported in literature using laser induced atomic beam fluorescence technique.

Human-vision-based evaluation method of a surveillance camera’s visual resolution: improvement from conventional slanted-edge spatial frequency response method

Zong Qin, Po-Jung Wong, Wei-Chung Chao, Fang-Cheng Lin, Yi-Pai Huang, and Han-Ping Shieh

Doc ID: 278518 Received 14 Oct 2016; Accepted 16 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: Visual resolution is an important specification of a surveillance camera and it is usually evaluated by line widths per picture height (LW/PH). The conventional evaluation method adopts slanted-edge spatial frequency response and uses a fixed decision contrast-ratio to figure out the LW/PH. However, this method brings about a considerable error with respect to humanly judged results since the perceptibility of human vision system varies from spatial frequency. Therefore, in this paper, contrast sensitivity function characterizing human vision system and slanted-edge spatial frequency response are combined to solve LW/PH, and a systematic calculation method is proposed. By adopting eight 720P camera modules working in day-mode and four 720P modules working in night-mode, mean absolute error between LW/PH calculated by proposed method and that judged by ten testees is as low as 26 (3.6% of 720P) while the error of the conventional method is 76 (10.6% of 720P).

Autonomous frequency stabilization of two extended cavity diode lasers at the potassium wavelength on a sounding rocket

Aline Dinkelaker, Max Schiemangk, Vladimir Schkolnik, Andrew Kenyon, Kai Lampmann, André Wenzlawski, Patrick Windpassinger, Ortwin Hellmig, Thijs Wendrich, E. Rasel, Michele Giunta, Christian Deutsch, Christian Kürbis, Robert Smol, Andreas Wicht, Markus Krutzik, and Achim Peters

Doc ID: 280140 Received 04 Nov 2016; Accepted 16 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: We have developed, assembled, and flight-proven a stable, compact, and autonomous extended cavity diode laser (ECDL) system designed for atomic physics experiments in space. To that end, two micro-integrated ECDLs at 766.7 nm were frequency stabilized during a sounding rocket flight by means of frequency modulation spectroscopy (FMS) of ³⁹K and offset locking techniques based on the beat note of the two ECDLs. The frequency stabilization as well as additional hard- and software to test hot redundancy mechanisms were implemented as part of a state-machine, which controlled the experiment completely autonomously throughout the entire flight mission.

Pixel-by-pixel absolute three-dimensional shape measurement with modified Fourier transform profilometry

Song Zhang, Huitaek Yun, and Beiwen Li

Doc ID: 280456 Received 08 Nov 2016; Accepted 15 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: Single-pattern Fourier transform profilometry (FTP) method and double-pattern modified FTP method have great value on high-speed three-dimensional (3D) shape measurement, yet it is difficult to retrieve absolute phase pixel by pixel. This paper presents a method that can recover absolute phase pixel by pixel for the modified FTP method. The proposed method uses two images with different frequencies, and the recovered low frequency phase is used to temporally unwrap the high-frequency phase pixel by pixel. This paper also presents the computational framework to reduce noise impact for robust phase unwrapping. Experiments demonstrate the success of the proposed absolute phase recovery method using only two fringe patterns.

A simple empirical master-slave dual-source configuration within the diffusion approximation enhances modeling of spatially resolved diffuse reflectance at short-path and with low-scattering from a semi-infinite homogeneous medium

Daqing (Daching) Piao and Sanjay Patel

Doc ID: 281482 Received 23 Nov 2016; Accepted 15 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: We present an empirical master-slave dual-source configuration within the diffusion approximation that enhances modeling of spatially resolved diffuse reflectance at short-path and with low-scattering from a semi-infinite homogeneous medium when irradiated by a pencil beam. An isotropic virtual source positioned near a depth of (1/reduced scattering coefficient) is used as the master source. A second isotropic virtual source whose depth and intensity depend upon those of the master source and tissue property according to a set of simple empirical formulae is added as the slave source. When tested for a semi-infinite homogeneous medium, this master-slave dual-source model consistently produces the aggressive peaking of the diffuse reflectance towards the point-of-entry that is significantly underestimated by the diffusion approximation involving only one source. Monte Carlo simulations have shown the effectiveness of this model at a short source-detector-separation of 1/100 of (1/reduced scattering coefficient) and an absorption to reduced scattering ratio as strong as 1, with an error within 20% in the near-field (1/10 of 1/reduced scattering coefficient).

High-precision Identification of Tip-tilt Control System for the Compensation of Time Delay

Yukun Wang, Zhaoliang Cao, shaoxin wang, Lifa Hu, Xuan Li, Quanquan Mu, dayu li, hy xu, and Xingyun Zhang

Doc ID: 279990 Received 23 Nov 2016; Accepted 15 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: The resolution of the ground-based large aperture telescopes are decreased severely due to the effect of the atmospheric turbulence. Adaptive optics systems (AOSs) have been widely used to overcome it and the low order aberrations (tip/tilt) are corrected by the TTM. In the tip/tilt (TT) correction loop, the time delay affects the correction performance significantly and a predicted signal compensation method (PSCM) has been used to reduce its effect. However, the performance of PSCM is reduced obviously due to the low identification accuracy of the TT AOS model. In this paper, a nonlinear least squares subspace identification (NLSSI) method is presented to obtain a high-precision model of the TT AOS. The system is identified with subspace method firstly, and then the identified parameters are modified in the frequency domain. By using this method, a TT correction system is identified. Compared with the subspace identification method, the identification accuracies of the time-domain and frequency response are increased 2 and 5 times respectively with NLSSI method. Furthermore, with the NLSSI method, the -3 dB error rejection bandwidth is increased from 69 hertz (HZ) to 76 Hz. At last, an adaptive correction experiment is performed on 1. Meter Telescope and the astronomical observation results show that the correction accuracy is increased to 1.5 times with NLSSI method. Moreover, the peak intensity of the image is improved by 11% with NLSSI method. This work is very helpful to improve the TT correction accuracy of AOS, especially for extreme adaptive optics and faint target observation.

A possible alternative acquisition scheme for GRACE Follow on type mission

Ziren Luo, Qinglan Wang, Christoph Mahrdt, Alexander Goerth, and Gerhard Heinzel

Doc ID: 282698 Received 12 Dec 2016; Accepted 15 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: An alternative acquisition scheme is introduced. The principle is to power modulate the laser at a frequency within the photodiode’s bandwidth. So the photodiode in each satellite can detect the laser signal from the other satellite incoherently. Therefore we can disentangle the degrees of freedom, two laser pointing directions per space craft and one frequency offset. Despite of the employment of downlink and uplink data transferring, the total scanning time could be reduced from several hours to 160 seconds.

Investigation on vibration excitation of debonded sandwich structures using time average digital holography (TADH)

Binu P. Thomas, Chittur Narayanamurthy, and Annamala S

Doc ID: 281831 Received 01 Dec 2016; Accepted 14 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: Sandwich structures, in the modern aerospace industry, are more sought after due to its high strength to stiffness ratio resulting in significant weight gains. Optical techniques like time average holography and shearography are preferred in industries for inspection of huge sandwich and composite panels because of whole-field (full coverage) inspection in a lesser time leading to large savings in cost. These techniques conventionally use sinusoidal frequency sweep to capture the local resonance of defective regions. This paper highlights the issues with the conventional approach of time average digital holography (TADH) and proposes a novel defect identification strategy through square wave excitation. The proposed method enhances the speed and accuracy of inspection; thereby it saves cost and increases confidence level. Extensive experiments have been carried out using honeycomb sandwich panels to demonstrate the methodology.

Coherent Anti-Stokes Raman Spectroscopy Measurement ofEthylene in Combustion

Andrew Cutler, Emanuela Gallo, and Luca Cantu

Doc ID: 280736 Received 14 Nov 2016; Accepted 14 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: WIDECARS has been developed for spatially and temporally resolved, simultaneousmeasurement of temperature and mole fraction of most major species in ethylene-air flames. Thispaper describes a method to infer CARS complex susceptibility distributions of the ν3 band ofethylene from WIDECARS spectra measured in heated mixtures of ethylene and air, and to usesuch distributions to fit experimental WIDECARS spectra in an ethylene-air flame. The methodis used to measure mole fraction ethylene in a dual-mode supersonic combustor burningpremixed ethylene and air with single-laser-shot precision (one standard deviation) of ±0.0025(absolute).

Near- and mid-IR ultrashort laser pulses filamentation in molecular atmosphere: Comparative analysis

Yuri Geints and Alexander Zemlyanov

Doc ID: 282063 Received 02 Dec 2016; Accepted 13 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: Self-focusing and filamentation of high-power pulsed laser radiation along spectrally-selective absorbing air path are numerically simulated in three spectral ranges centered at 0.8, 3.9, and 10.6 µm. Detailed comparative analysis of the main pulse parameters in the filamentation area is performed to examine the potential of various laser sources for the atmospheric optics. We found that the radiation of mid-IR lasers (3.9, and 10.6 µm) forms the longest filamentation region and the widest supercontinual spectrum in comparison with near-IR radiation. Filamentation of 3.9 µm laser pulse results in the best spatially continued plasma channel, while 10.6 µm pulse retains the widest spectral composition under the conditions of strong molecular absorption in the atmosphere.

Fast conical surfaces evaluation with null-screens and randomized algorithms

Daniel Aguirre, J. Rufino Diaz-Uribe, Manuel Campos-Garcia, Brenda Villalobos-Mendoza, Rafael Izazaga-Pérez, and Oliver Huerta-Carranza

Doc ID: 280055 Received 03 Nov 2016; Accepted 13 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: A method for the evaluation of the shape of fast conical surfaces based on the null-screen method is presented. The proposed method is based on randomized algorithms, where instead of integration as is usually performed, the shape of the surface is recovered in a direct and random way. This is done by proposing a new test surface; the surface parameters are randomly generated and the calculated null-screen is compared against the originally designed. The coefficients that generate the null-screen closest to the reference null-screen are taken as the final values that describe the surface under test. The algorithm validation was done in the theoretical and experimental way. For the theoretical way, a convex parabolic surface with 21.36 mm radius of curvature and f/0.178 was simulated and analyzed; in the experimental way, a convex spherical surface f/0.33 and a concave ellipsoidal mirror f/0. 81 were evaluated. The results obtained with our algorithm in the evaluation of the ellipsoidal surface were compared against the results obtained with traditional methods. We found that the radius of curvature, conic constant and the decentering coefficients that were used to generate each surface were retrieved in a good manner with our algorithm. The results show that these parameters can be recovered with a percent error smaller than 1% in the case of simulations, and smaller than 2% in the two experimental cases.

Open-Path Spectroscopic Methane Detection Using a Broadband Monolithic Distributed Feedback-Quantum Cascade Laser (DFB-QCL) Array

Anna Michel, Jason Kapit, Mark Witinski, and Romain Blanchard

Doc ID: 279687 Received 08 Nov 2016; Accepted 13 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: Methane is a powerful greenhouse gas that has both natural and anthropogenic sources. The ability to measuremethane using an integrated path length approach such as an open/long-path length sensor would be beneficial inseveral environments for examining anthropogenic and natural sources, including tundra landscapes, rivers, lakes,landfills, estuaries, fracking sites, pipelines, and agricultural sites. Here a broadband monolithic DistributedFeedback-Quantum Cascade Laser (DFB-QCL) array was utilized as the source for an open-path methane sensor.Two telescopes were utilized for the launch (laser source) and receiver (detector) in a bistatic configuration formethane sensing across a 50 m path length. Direct absorption spectroscopy was utilized with intrapulse tuning.Ambient methane levels were detectable and an instrument precision of 70 ppb with 100 second averaging and 90ppb with 10 second averaging was achieved. The sensor system was designed to work “off the grid” and utilizesbatteries that are rechargeable with solar panels and wind turbines.

Super resolved nanoscopy using Brownian motion of fluorescently labeled gold nanoparticles

Zeev Zalevsky, Tali Ilovitsh, Asaf Ilovitsh, and Omer Wagner

Doc ID: 279798 Received 31 Oct 2016; Accepted 12 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: The fundamental limit set by the wavelength of light can be overcome using methods of super-resolution localization microscopy. These methods require the labeling of the sample with fluorescent molecules and are time consuming as repeated cycles of activation and photobleaching of the sample are required. Alternatively, we propose a simplified approach that is free from direct labeling with fluorescence molecules, and does not require the repeated cycles of activation and photobleaching. The method uses fluorescently labeled gold nanoparticles in aqueous solution that are distributed on top of the sample. The nanoparticles move in random Brownian motion and obscure different areas of the sample, while the scene is being imaged sequentially. By conducting the proper post-processing, a super-resolution image can be generated. The method is validated both by numerical simulations as well as by experimental data.

Arrayed optical switches based on integrated liquid-crystal microlensarrays driven and adjusted electrically

di fan, Cheng Wang, Zhaowei Xin, Dong Wei, Zhang Xinyu, Changsheng Xie, BO ZHANG, qing tong, and yu lei

Doc ID: 276372 Received 26 Sep 2016; Accepted 12 Jan 2017; Posted 13 Jan 2017  View: PDF

Abstract: Based on our fundamental work of liquid-crystal microlens arrays (LCMAs) driven and adjusted electrically, a new kind of arrayed optical switch (AOS) constructed by a key LCMA with a special dual-mode function of converging and diverging incident beams according to electrical signals applied over the LCMA, is proposed. The LCMA leading to the AOS is constructed by a microcavity with a couple of paralleled electrodes shaped over SiO2 wafers and a layer of nematic liquid-crystal materials with a micrometer-scale thickness and closely packaged in the microcavity. The top electrodes of theLCMA are fabricated by depositing a layer of indium-tin-oxide (ITO) film and a layer of aluminum film with a thickness in micrometer-scale over both opposite surfaces of a SiO2 wafer, respectively. The aluminum film is continuously patterned into a circular microhole array with suitable diameter and spacing between microholes through conventional UV-photolithography, and the ITO film only acts as a planar conductor. Both functioned films are effectively separated by the SiO2 wafer with a typical thickness of about several tens of micrometers. Another SiO2 wafer with a similar thickness asthe top microstructure is also coated by an ITO film as a planar conductor. The AOS is driven and adjusted by applied electrical signals with different root mean square (rms) voltage amplitude. The measurements show that the developed AOS can effectively switch on or off beams propagating in arrayed fibers through applying proper voltage signals on them. Compared with other conventional AOSs, the developed AOS demonstrates several merits including greater integration level, lower cost, being suitable to high power propagating beams.

Mobile lidar system for environmental monitoring

Sune Svanberg, Guangyu Zhao, Ming Lian, Yiyun Li, zheng Duan, Shiming Zhu, and Liang Mei

Doc ID: 278054 Received 03 Oct 2016; Accepted 12 Jan 2017; Posted 13 Jan 2017  View: PDF

Abstract: A versatile mobile optical remote sensing system utilizing lidar (light detection and ranging) technology has been constructed and adapted for multidisciplinary environmental monitoring tasks on the Chinese scene. A key application is differential absorption lidar (DIAL) monitoring of distributions of gaseous air pollutants. The system includes a 20 Hz Nd:YAG laser-pumped dye laser, optical transmitting/receiving systems, electronics and basic supporting installations, all integrated in a laboratory installed on a truck. Two optical receivers are available as vertically-looking Newtonian telescopes with diameter 40 and 30 cm, respectively, over which folding mirrors can be hoisted over the laboratory roof to interrogate the remote target area. Using harmonic pulses from the Nd:YAG laser alone, remote laser-induced fluorescence (LIF) and laser-induced break-down spectroscopy (LIBS) can be performed. In this way also water pollutants, vegetation, soils and surfaces from historical buildings can be studied. CW long-path absorption gas measurements and agricultural pest insect monitoring can also be performed. The wide applicability of the new system is illustrated in long-range measurements of atmospheric mercury and sulfur dioxide, and by LIF and LIBS monitoring of vegetation and soil samples. Remote passive monitoring of flying insects illustrates the additional functionality of the system.

Electrically tunable infrared filter based on a cascaded liquid-crystal Fabry-Perot for spectral imaging detection

qing tong, Jiuning Lin, yu lei, Zhaowei Xin, Dong Wei, Zhang Xinyu, Jing Liao, Haiwei Wang, and changsheng Xie

Doc ID: 279766 Received 14 Nov 2016; Accepted 12 Jan 2017; Posted 13 Jan 2017  View: PDF

Abstract: An electrically tunable infrared (IR) filter based on a key cascaded liquid-crystal Fabry-Perot (C-LC-FP) working in the wavelength range of 3-5 μm, is presented. The C-LC-FP is constructed by closely stacking two FP microcavities with different depth of 12 and 15 μm and fully filled by nematic LC materials. Through continuous wavelength selection of both microcavities, the radiation with high transmittance and narrow bandwidth can pass through the filter. According to the electrically controlled birefringence characteristics of nematic LC molecules, the transmission spectrum can be shifted through applying dual voltage signals over the C-LC-FP. Compared with common LC-FP with single microcavity, the C-LC-FP demonstrates better transmittance peak morphology and spectral selection performance. To be more specific, the number and the shifted scope of the IR transmission peak can be decreased and widened, respectively.

Engineering of cylindrical vector fields with a twisted nematic SLM

Alejandra Serrano, Victor Ruiz-Cortes, and Luis Palafox

Doc ID: 280475 Received 09 Nov 2016; Accepted 12 Jan 2017; Posted 13 Jan 2017  View: PDF

Abstract: We demonstrate a technique for the generation of vectorial optical fields based on a single pass of light onto a reflective twisted nematic spatial light modulator (TN-SLM). Using a beamsplitter and a quarter waveplate, a polarization rotator is implemented. As a result, each cell of the modulator is independently manipulated, generating linear polarization states. A curve of the behavior of this polarization rotator with the twisted nematic modulator in use proves a modulation up to 177 degrees, turning this setup suitable for engineering of cylindrical vector fields. A mathematical justification and an experimental demonstration of the generation of these beams and their quality are presented. The experimental results show that despite the presence of a small component of elliptical polarization, a twisted nematic modulator can be used to achieve local polarization control. A series of vector fields with variations of the parameters of topological charge, phase offset and quadratic phase are engineered, analyzed with a linear polarizer and captured. The proposed setup represents a simple approach for polarization manipulation using a twisted nematic modulator and few optical elements, achieving polarization purity greater than 94%.

Strain induced spectral tuning of the whispering gallery modes in a cylindrical micro-resonator formed by a polymer optical fiber

Vishnu Kavungal, arun mallik, Gerald Farrell, Qiang Wu, and Yuliya Semenova

Doc ID: 281878 Received 30 Nov 2016; Accepted 12 Jan 2017; Posted 13 Jan 2017  View: PDF

Abstract: A mechanical strain assisted technique for spectraltuning of whispering gallery modes (WGM) in acylindrical micro-resonator formed by a polymer opticalfiber (POF) is investigated. WGMs in the POF basedmicro-cylinder are excited by evanescent light couplingusing a tapered single mode silica fiber. WGMs observedin the transmission spectrum of the silica fiber taperhave a high extinction ratio of up to 19 dB and a Q-factorof up to 2.64 × 104. The application of tensile axial strain(μɛ) in the range from 0 to 1746 μɛ (0.17 %) to the POFmicro-resonator results in a linear shift of the WGMspectrum with a sensitivity of 0.66 pm/μɛ. Under theinfluence of the applied strain the WGMs undergo a blueshift and return to their initial spectral positions after thestrain is decreased. The proposed strain-tunable POFmicro-resonator has potential applications in fiber opticsensing and tunable micro lasers.

Pupil motion analysis and tracking in ophthalmic systems equipped with wavefront sensing technology

Serge Meimon, Jarosz Jessica, Cyril Petit, elena gofas-salas, Katharine Grieve, Jean-Marc Conan, Bruno Emica, Michel Paques, and Kristina Irsch

Doc ID: 278909 Received 17 Oct 2016; Accepted 11 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: Our eyes are constantly in motion, even during “steady” fixation. In ophthalmic systems equipped withwavefront technology, both eye and head motion potentially degrade its performance and/or increasethe cost and complexity, as they induce a movement of the entrance optical pupil of the system. Here, wecharacterize the pupil motion in an aberrometry setting, using a custom, high-speed pupil tracker (478Hz),and draw conclusions on design considerations of future ophthalmic systems. We also demonstrate thefeasibility of tracking such motion directly with a custom-built Hartmann-Shack sensor ( 6Hz) using amethod that offers certain benefits over previously suggested approaches, thereby paving the way to anefficient and cost-effective approach.

Impact of Non-Integer Planetary Revolutions on the Distribution of Evaporated Optical Coatings

James Oliver

Doc ID: 280385 Received 08 Nov 2016; Accepted 11 Jan 2017; Posted 18 Jan 2017  View: PDF

Abstract: Planetary substrate rotation for optical-coating deposition is evaluated based on initial and final positions for a given layer with different numbers of revolutions and various deposition-source locations. The influence of partial revolutions of the rotation system is analyzed relative to the total number of planetary revolutions in that layer to determine the relative impact on film thickness and uniformity. Guidance is provided on the necessary planetary revolutions that should take place in each layer versus the expected error level in the layer thickness for the modeled system.

Arbitrary patterned anisotropic diffractive opticalelements using Galvanometer polarization drawingmethod: Application in fabricating polarizationdependentliquid-crystal Fresnel lens cell

Kohei Noda, Jou Matsubara, Kotaro Kawai, Moritsugu Sakamoto, Tomoyuki Sasaki, Nobuhiro Kawatsuki, Kohei Goto, and Hiroshi Ono

Doc ID: 278310 Received 10 Oct 2016; Accepted 10 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: To fabricate two-dimensional anisotropic diffractive optical elements, the polarization drawing method usingpolarization-sensitive liquid-crystal polymers and Galvano scanner offers a flexible approach. This methodproduces an arbitrary anisotropic distribution in the polymers films by controlling the polarization state of anultra-violet laser beam during scanning. The fabrication of two patterned anisotropic diffractive elements, whichcannot be fabricated using conventional methods of polarization holography, demonstrates its efficacy. In addition,we also fabricate a liquid-crystal Fresnel lens using this method. Our approach has the potential to produce highlyfunctionalizeddiffractive optical elements having complex anisotropic spatial distributions.

Analysis of detection bandwidth limitations in time-stretch-based single-pixel imaging systems

Qiang Guo, Hongwei Chen, Minghua Chen, Sigang Yang, and Shizhong Xie

Doc ID: 282243 Received 05 Dec 2016; Accepted 10 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: Single-pixel imaging (SPI) has recently attracted considerable attention in magnetic resonance imaging and remote sensing for its data compression capability and broad operational wavelength range. However, the frame rates of single-pixel cameras are largely limited by the response time of digital micromirror devices (DMDs). To circumvent this challenge, a novel SPI technique called time-stretch-based single-pixel imaging (TSSPI) is proposed, which can increase the imaging speed of single-pixel cameras based on DMD by over three orders of magnitude. In the TSSPI system, photodetection bandwidth and pulse repetition rate are critical parameters influencing the quality of reconstructed images. In this paper, we quantitatively analyze their effects on reconstruction accuracy through simulation and experiment for the first time. Photodetectors with various bandwidths are separately used to acquire the same number of measurements for image reconstruction and the peak signal-to-noise ratios (PSNRs) of the reconstructed images are calculated to evaluate the reconstruction accuracy. We experimentally demonstrate that the ratio between photodetection bandwidth and pulse repetition rate has a strong impact on reconstruction quality. A threshold for this ratio is estimated and high-quality image reconstruction can be achieved only above this threshold. In addition, we also demonstrate that the ratio is related to the complexity of the illuminated scene.

Optimized Si₃N₄ grating couplers for relaxed alignment requirements under flood illumination

Daan Martens, Genghua Dong, and Peter Bienstman

Doc ID: 279164 Received 25 Oct 2016; Accepted 10 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: Grating couplers are an essential building block to integrated photonic circuits, as they allow surface access to the photonic chip. They are most commonly used in combination with an optical fiber, requiring precise alignment, resulting in a high instrumentation cost. In this paper, an alternate use is proposed: By flood illuminating part of the chip surface, the alignment conditions can be relaxed. The grating coupler parameters were optimized for this coupling method. The novel grating couplers were fabricated in Si₃N₄ and characterized through flood illumination measurements. At peak wavelength as well as within a 20 nm interval, the coupled power was increased considerably over a smaller coupler, a factor 6 and 4.5 respectively. The influence on bandwidth and required precision of coupling angle were also investigated. These optimized designs for flood illumination can provide a cost-efficient coupling mechanism for numerous applications.

Automatic Geometric Calibration and Three-Dimensional Detecting with an Artificial Compound Eye

Huijie Jian, Jianzheng He, Xueying Jin, xiangcheng chen, and Wang Wang

Doc ID: 281074 Received 17 Nov 2016; Accepted 10 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: A bicylinder-based geometric calibration and three-dimensional detecting method is developed for an artificial compound eye. The method proposed in this paper uses two coaxial cylinders as reference surfaces, which is more suitable for the demand of wide field of view than the traditional two-plane method. A weighted multiple-line intersection algorithm is employed to figure out the 3D intersecting point more precisely. In order to evaluate these methods, a number of known points that covers 110°×90° field of view are measured. Experimental results indicated the proposed methods is accurate, reliable and meets the needs for compound eye calibration.

Development of 1.6 μm DIAL using OPG/OPA transmitter for measuring atmospheric CO₂ concentration profiles

Yasukuni Shibata, Chikao Nagasawa, and Makoto Abo

Doc ID: 278572 Received 12 Oct 2016; Accepted 10 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: An experiment for the measurements of atmospheric CO2 vertical profiles up to 7 km altitude was successfullyconducted using a 1.6 μm ground-based differential absorption Lidar developed by Tokyo Metropolitan University.To achieve a high pulse repetition rate, large power output, and high frequency stabilization, we developed a new1.6 μm Lidar system using an optical parametric generator (OPG) transmitter. Unlike the previous system’stransmitter, OPG does not need a resonator. We amplified its output with two optical parametric amplifiers. Wevalidated our system against an in situ sensor and found the difference between their CO2 concentrationmeasurements to be 0.06 ppm.

Step heating infrared thermographic inspection of steel structure by applying least-square regression

Hanxue Zhao, Zhenggan Zhou, Guangkai Sun, Jin Fan, and Gen Li

Doc ID: 278870 Received 18 Oct 2016; Accepted 10 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: This paper reports the application of the least-squares regression method in the step heating thermographic inspection of steel structure. The surface temperature variation of a slab with finite thickness during both the step heating phase and the cooling down phase is presented. A mild steel slab with holes of various depths and diameters is chosen as the specimen. The step heating thermographic inspection experiments are carried out on the specimen with different heating time. The heating as well as the cooling down phases are recorded with an infrared camera and are analyzed separately by linear regression of the double logarithmic temperature increase versus time plots. And three statistics of the linear regression, the slope, the coefficient of determination and the F-test value, are used to image maps according to the processing results. The signal-to-noise ratio of each map is calculated to evaluate the performance of the three imaging methods with different duration of heating time and cooling time. The results prove that the F-test value maps present good performance for the sequences of the step heating phase while the slope maps present good performance for the sequences of the cooling down phase. The optimal heating time and cooling time for a steel structure are also concluded. The comparison with the results of the Thermographic Signal Reconstruction method proves that the least-squares regression method has better detectability and higher inspection efficiency.

Long-Range and High-Resolution Correlation Optical Time-Domain Reflectometry using a Monolithic Integrated Broadband Chaotic Laser

Limeng Zhang, Biwei Pan, Guangcan Chen, Dan Lu, and Ling-Juan Zhao

Doc ID: 281238 Received 23 Nov 2016; Accepted 10 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: We experimentally demonstrate a compact, long range, high-resolution chaotic correlation optical time-domainreflectometry based on a monolithic integrated chaotic laser (MICL). The MICL can directly generate broadbandchaotic signal covering a RF frequency range of over 40 GHz. Multi-reflection events can be precisely located in adetection range of ~47 km with a range-independent resolution of 2.6 mm.

Optical tweezers affected by monochromatic aberrations

Ronald Kampmann and Stefan Sinzinger

Doc ID: 281481 Received 23 Nov 2016; Accepted 09 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: The performance of optical tweezers in the presence of monochromatic aberrations is investigated theoretically and experimentally. For the calculation of optical forces we use a ray optics based force simulation, which is embedded in a ray tracing routine. By considering optical path differences caused by monochromatic aberrations we are able to simulate their effect on the trapping forces. Optical trapping experiments considering the influence of aberrations were performed with an optical tweezers system, specially adapted to trap particles in gaseous surrounding. The conformity of these measurements with the theoretical predictions verifies the correct performance of the optical force simulation routine. Based on the reliable simulation tool, further theoretical studies are performed of how optical aberrations affect the function and performance of optical tweezers.

Inversion of ellipsometry data using a constrained spline analysis

Mickael Gilliot

Doc ID: 280131 Received 03 Nov 2016; Accepted 09 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: Ellipsometry is a highly sensitive and powerful optical technique of thin films characterization. However the indirect and non-linear character of the ellipsometric equations requires numerical extraction of the interesting information such as thicknesses and optical constants of unknown layers. A method is described to perform the inversion of ellipsometric spectra for simultaneous determination of thickness and optical constants without requiring particular assumptions about the shape of a model dielectric function like in the traditional method of data fitting. The method is based on a Kramers-Kronig consistent description of the imaginary part of the dielectric function using a set of points joined by pieces of third degree polynomials. Particular connection relations constrain the shape of the constructed curve to a physically meaningful curve avoiding oscillations of natural cubic splines. The connection ordinates conditioning the shape of dielectric function can be used, together with unknown thicknesses or roughness, as fitting parameters with no restriction about the material nature. Typical examples are presented concerning metal and semiconductors.

Method for In-Depth Characterization of Electro-Optic Phase Modulators

Bassem Arar, Max Schiemangk, Hans Wenzel, Andreas Wicht, Achim Peters, Guenther Traenkle, and Olaf Brox

Doc ID: 280202 Received 07 Nov 2016; Accepted 09 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: A flexible method to measure the modulation efficiency and residual amplitude modulation, includingnon-linearities, of phase modulators is presented. The method is based on demodulation of the modulatedoptical field in the optical domain by means of a heterodyne interferometer and subsequent analysisof the I&Q quadrature components of the corresponding RF beat note signal. As an example, we determinethe phase modulation efficiency and residual amplitude modulation for both, the TE and TM modesof a GaAs chip-based phase modulator at the wavelength of 1064nm. From the results of these measurementswe estimate the linear and quadratic electro-optic coefficients for a P-p-n-N GaAs/AlGaAs doubleheterostructure.

Ultra-Low Loss Hybrid Core Porous Fiber for Broadband Applications

Mr. Islam, Jakeya Sultana, Javid Atai, Derek Abbott, sohel rana, and Mohammad rakibul Islam

Doc ID: 281087 Received 18 Nov 2016; Accepted 09 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: In this paper, we present the design and analysis of a novel hybrid porous core octagonal lattice photonic crystal fiber for terahertz (THz) wave guidance. The numerical analysis is performed using a full-vector finite element method (FEM) which shows that 80% of bulk absorption material loss of TOPAS can be reduced at a core diameter of 350 µm. The obtained effective material loss (EML) is as low as 0.04 cm-1 at an operating frequency of 1 THz with a core porosity of 81%. Besides, the proposed photonic crystal fiber also exhibits comparatively higher core power fraction, lower confinement loss, higher effective mode area and ultra-flattened dispersion profile with single mode propagation. The proposed fiber can be readily fabricated using capillary stacking and sol-gel technique and be used for broadband applications of terahertz waves.

Influence of Se beam pressure on deep-level defects in Cu(In,Ga)Se2 thin films studied by photocapacitance and time-resolved photoluminescence measurements

Shaoqiang Chen, Xiaobo Hu, Juanjuan Xue, Jiao Tian, and Guo-En Weng

Doc ID: 281883 Received 30 Nov 2016; Accepted 09 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: The properties of deep-level defects in Cu(In,Ga)Se₂ thin films grown under different Se beam pressure were investigated by photocapacitance (PC) and time-resolved photoluminescence (TRPL) measurements. A generally known deep-level defect located at around 0.8 eV above the valence band was identified for all samples by transient photocapacitance measurement, the position of which was unvaried with the Se beam pressure. The defect concentration and the capture cross section of the minority carrier were obtained from the steady-state photocapacitance and TRPL measurements, which were evaluated to be on the order of 10^-14 cm^-3 and 10^-14 cm^2, respectively, in the Se beam pressure range from 1.3×10^-3 to 4.4×10^-3 Pa. The relatively higher defect concentration and larger minority carrier capture cross section were considered as possible causes of the degradation of the conversion efficiency of CIGS solar cells grown under low Se beam pressure.

Towards optoelectronic logic circuits for visible light: achalcogenide glass single-mode single-polarizationoptical waveguide switch

zhi chen, Guande Wang, Xiong Wang, and Quanzhong Zhao

Doc ID: 282314 Received 06 Dec 2016; Accepted 09 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: In this paper, we propose an arsenic trisulfide (As-S) optical waveguide switch-based logic gate mainly comprisinga photorefractive Sn1As20S79 waveguide core and a LiNbO3 crystal substrate. In combination with the unique opticalstopping effect of Sn1As20S79, this device can realize logical operation on a electrical signal and a optical signal,holding promise to be applied in optoelectronic logic circuits. While most of previous research on As-S has focusedon applications in the infrared regime, this device operates at the visible wavelength of 632.8 nm and 441.6 nm,which are the specific wavelengths for the optical stopping. As the kernel part of this logic gate, an opticalwaveguide switch based on electro-optic coupler is employed to control optical signals by electrical signals,providing a solid foundation of operation for electro-optic logic function. Some crucial design specifications of theswitch are optimized by means of simulation analysis. It is found that less than 10 V applied voltage is sufficient torealize satisfactory function of the switch. Coupling efficiency of 90% and extinction ratio of greater than 10 dB areachieved by simulating the lightwave propagation in the waveguide switch. Since the waveguide structure of theswitch has no upper cladding, it is different from that of ridge waveguide or buried waveguide, and is thusconvenient to fabricate only using ultraviolet exposure without etching. Our work will open new possibilities forphotoelectric hybrid logical operation in visible light, and thus provide a fertile ground of applications inprogrammable optical chips.

Study on Multi-photon Induced Fluorescence Spectrum of SO₂

Zhan long Zhao, Lianshui Zhang, Guiyin Zhang, and miao zhang

Doc ID: 279832 Received 16 Dec 2016; Accepted 08 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: The laser induced fluorescence spectrum of SO₂ in the range of 200–460 nm has been obtained with the dyer laser (579 nm) pulsed by Nd:YAG laser as the excitation source. The transitions process, both X¹A₁→C¹B₂ excited by three-photon and X¹A₁→A¹A₂ excited by two-photon, have been evaluated. The relaxation kinetics of the excited molecules in the states of C¹B₂, A¹A₂ has been analyzed on the basis of the excitation spectrum in the range of 560–580 nm. The spectral sequence rules are assigned, and it can be calculated that the symmetric stretching vibration and the bending vibration frequencies of C¹B₂ state are ω₁=942.9 cm-¹, ω2=369.8 cm-¹, and the bending vibration frequencies of A¹A₂ state are ω₂=493.4 cm-¹. The analysis of the time resolved spectrum proved that the relaxation process C¹B₂→A¹A₂→X¹A₁ and the phosphorescent process a³B₁→X¹A₁ exists simultaneously.

Development of an incoherent broad-band cavity-enhanced aerosol extinction spectrometer and its application to measurement ofaerosol optical hygroscopicity

Weixiong Zhao, Xuezhe Xu, Bo Fang, Qilei Zhang, Xiaodong Qian, Shuo Wang, Pan Liu, Weijun Zhang, Zhenzhu Wang, Dong Liu, yinbo huang, Dean Venables, and Weidong Chen

Doc ID: 280928 Received 16 Nov 2016; Accepted 08 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: We report on the development of a blue light-emitting diode (LED) based incoherent broad-band cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for the measurement of the aerosol extinction coefficient at λ = 461 nm. With an effective absorption pathlength of 2.8 km, an optimum detection limit of 0.05 Mm-1 (5×10-10 cm-1) was achieved with an averaging time of 84 s. The baseline drift of the developed spectrometer was about ± 0.3 Mm-1 over 2.5 h (1σ standard deviation). The performance of the system was evaluated with laboratory generated monodispersed polystyrene latex (PSL) spheres. The retrieved complex refractive index (CRI) of PSL agreed well with previously reported values. The relative humidity (RH) dependence of the aerosol extinction coefficient was measured using IBBCEAS for the first time. The measured extinction enhancement factor f(RH) values for 200 nm dry ammonium sulphate particles at different RH were in good agreement with the modeled values. Field performance of the aerosol extinction spectrometer was demonstrated at the Hefei Radiation Observatory (HeRO) site.

Terahertz Conductivity Engineering in Surface Decorated Carbon Nanotube Films by Gold Nanoparticles

Rajib Mitra, Debanjan Polley, Animesh Patra, and Anjan Barman

Doc ID: 281105 Received 18 Nov 2016; Accepted 08 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: We report the controllable conductivity of single walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) with their surface walls decorated by gold nanoparticles (Au NPs) with varying concentration in terahertz (THz) frequency range. Colloidal Au NPs of nominal diameter ~ 15 nm are synthesized by the reduction of gold chloride solution using tri-sodium citrate. A simple chemical route is followed to attach Au NPs on the surfaces of both types of carbon nanotubes (CNTs). The attachment of Au NPs on the sidewalls of CNTs is confirmed by UV-visible spectroscopy and scanning electron microscope images. THz spectroscopic measurements are carried out at room temperature in transmission geometry in the frequency range of 0.3-2.0 THz. It is found that the THz conductivity of the surface decorated SWNT composites can either be increased or decreased in the range ± 15 % than the as prepared SWNT composites by carefully choosing the Au NP concentration. The conductivity variation is qualitatively explained in terms of carrier trapping potential for low Au NP density and alternative carrier conduction pathways at higher Au NP density and analysed with the help of a modified universal dielectric relaxation (UDR) model.

Dissimilar-fiber-long-period fiber gratings: Concept and demonstration

Pengfei Wang and Thomas Gaylord

Doc ID: 276360 Received 21 Sep 2016; Accepted 08 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: A new type of long-period fiber grating structure that contains dissimilar fiber types is proposed. This dissimilar-fiberlong-period fiber grating (DF-LPFG) structure is fabricated by splicing together sub-period-sections of dissimilar fibertypes. Due to the large index differences that can exist between various fiber types, the resulting DF-LPFGs can beexceptionally short, e.g. a few millimeters. As a demonstration, prototype DF-LPFGs were fabricated by periodicallysplicing together standard single-mode fiber and dispersion-compensating fiber using a commercially available cleaverand splicer. The resulting DF-LPFGs exhibited clear resonances with an attenuation of ~35 dB and an insertion loss of ~8dB. To the best of the authors’ knowledge, this is the first demonstration of the DF-LPFG concept. Other devices based onthis concept may also be realizable.

HIGH-RESOLUTION WAVELET-FRACTAL COMPRESSED OPTICAL COHERENCETOMOGRAPHY IMAGES

Mohammad Avanaki, Faiza MEKHALFA, Saba Adabi, and BERKANI DAOUD

Doc ID: 281155 Received 18 Nov 2016; Accepted 07 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: Three dimensional (3D) optical coherence tomography (OCT) images could assist specialists in diagnosis of adisease in a tissue by providing morphological information from it. Since the size of such images is usuallyextremely large, an appropriate image compression method can help in the storage and transmission of theseimages. Fractal image compression provides very high compression ratio and discrete wavelet transform (DWT)retains frequency and spatial information in the signal. In order to combine these two techniques, fractal codinghas to be performed in the wavelet domain. In this work, we propose a three dimensional extension version ofwavelet-fractal coding algorithm. The use of 3D fractal approximation to encode 3D wavelet coefficients allows toexploit inter and intra redundancy of the image sequences. The compression results of several OCT images usingthe 3D wavelet-fractal algorithm are evaluated qualitatively and quantitatively, and compared with the results ofthe 2D approach.

Relative positioning method for near-field beam spot array with optical microscope image of lithographic patterns using linear regression

Jae Hahn, Seonghyeon Oh, and Jinhee Jang

Doc ID: 280462 Received 09 Nov 2016; Accepted 07 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: A method for simply analyzing the relation between spot positions of near field beam sources with micrometer pitch is proposed using optical microscope. Based on the locations of spots in an optical microscopy image of lithographic patterns, the effective relative position is derived using simple linear regression. Numerical analysis is performed to introduce the concept and to evaluate the methodology with random noise. The accuracy and uncertainty of the proposed method are discussed. To confirm the method feasibility, the experiments are conducted using fabricated probe array and the experimental and numerical results are compared on the basis of uncertainty. An arbitrary pattern is recorded with respect to relative coordinates obtained based on the effective positions. We suggest a simple strategy for controlling beam spot array locations for pattern design in near field lithography with less than 5-nm uncertainty.

Multi wavelength stabilization control of thermooptic system with adaptive reconfiguration

andri mahendra, Chunle Xiong, Xiang Zhang, Benjamin Eggleton, and Philip Leong

Doc ID: 280105 Received 07 Nov 2016; Accepted 06 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: Accurate temperature control is crucial for the reliable operation of photonic integrated circuits in the presence of internal thermal crosstalk or external thermal disturbance. We propose an adaptive multiple-input and multiple-output (MIMO) control scheme to stabilize the operation wavelength of on-chip wavelength demultiplexers that have many applications in photonic-chip-based optical signal processing. Using the MIMO control scheme, the wavelength drift is reduced from 0.5 nm to 0.1 nm when internal and external thermal disturbances occur.

Dielectric functions of Pd and Zr transition metals: an application of Drude-Lorentz models with simulated annealing optimization.

William Vargas

Doc ID: 280721 Received 14 Nov 2016; Accepted 06 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: An Accepted-Probability-Controlled Simulated Annealing (APCSA) method has shown to be a valuable tool to describe in parametric form, by means of an extended Drude-Lorentz model, the dielectric function of several metals through infrared, visible, and ultraviolet photon energies [A. D. Rakic, A. B. Djurisic, J. M. Elazar, M. L. Majewski, Appl. Opt. 37, 5271-5283 (1998)]. In this work, an improved APCSA approach is used to estimate the parameters involved in an extended Drude-Lorentz type model which incorporates the dielectric constant due to a background electronic polarization in the Drude term and the normalization of the individual oscillation strengths involved in the Lorentz contributions to the dielectric function. This last approach allows us to introduce a new parameter z to be optimized: the number density ratio, i.e. the ratio between number density of conduction electrons and number density of metal ions. From the optimization of the z value within this novel approach, we evaluate other parameters: electrical resistivity, electron mean free path, effective mass of conduction electrons and relaxation time, Fermi energy, and electronic density of states at the Fermi level. Application of the model is carried out to describe the dielectric functions of two transition metals, Pd and Zr, through ultraviolet, visible and infrared photon energies.

Optical sensor for dual sensing of oxygen and carbondioxide based on sensing films coated on filter paper

cheng-shane chu and JHIH-JHENG SYU

Doc ID: 275612 Received 12 Sep 2016; Accepted 06 Jan 2017; Posted 06 Jan 2017  View: PDF

Abstract: An optical sensor for the dual sensing of oxygen (O2) and carbon dioxide (CO2) based on sensing films coated onfilter paper is proposed. A ethyl cellulose (EC) doped with platinum (II) mesotetrakis(pentafluorophenyl)porphyrin (PtTFPP) and 7-amino-4-trifluoromethyl coumarin (AFC) serves as the oxygensensing material and reference blue emission dye for pH indicator, respectively. The CO2 sensing layer includes thepH-sensitive fluorescent indicator 1-hydroxy-3,6,8-pyrenetrisulfonic acid trisodium salt (HPTS) immobilizedwithin the EC. The oxygen and carbon dioxide sensitive materials can both be excited with a 405-nm LED and thetwo emission wavelengths can be detected separately. The experimental result reveals that the optical oxygen andcarbon dioxide sensors have sensitivities of IN2/I100%O2 =22.8 and IN2/I100%CO2 =3.6, respectively. The response timesof the optical oxygen sensor were 15 s upon switching from nitrogen to oxygen and 41 s when moving from oxygento nitrogen. The response times of the optical carbon dioxide sensor were 7 s upon switching from 100% N2 to100% CO2 and 39 s when moving from 100% CO2 to 100% N2. The proposed optical dual sensor can be used for thesimultaneously sensing of oxygen and carbon dioxide concentrations in the environmental applications.

Research about Fluid Hydrodynamic Fixed AbrasiveGrinding based on Small Tool

Bin Lin, Peng Liu, Xiaofeng Zhang, and Yan Li

Doc ID: 276088 Received 06 Oct 2016; Accepted 05 Jan 2017; Posted 06 Jan 2017  View: PDF

Abstract: A new grinding technology called fluid hydrodynamic fixed abrasive grinding (abbreviated as FHFAG process) isbeing proposed in this research. It combines the fixed abrasive grinding process and the fluid hydrodynamictheory. This research will examine the feasibility of applying the innovative process as ultra-precision machiningmethod for the hard and brittle materials such as fused silica glass and silicon. It aimed to turn fixed abrasivegrinding processing into a kind of deterministic surfacing processing method. Besides, the method could improvethe machining efficiency and machining accuracy at the same time. Specifically, a thin liquid film between thegrinding pad and the workpiece is introduced. The cutting depth based on one single grinding pad with a settledparticle size can be controlled by controlling the thickness of the liquid film. From the machining mechanism, thegrinding tool’s rotary speed and the original input pressure dominate the deterministic properties of the process. Aspecial self-balancing device and a special fluid supply method which supply the grinding liquid from the center ofthe motorized spindle are proposed to realize the new processing technology. The grinding pad can float on theworkpiece steadily from a preliminary experiment result. It is clearly demonstrated that FHFAG process can beused as deterministic processing method if the identified working parameters are well controlled.

Automatic regularization parameter selection by generalized cross-validationfor total variational Poisson noise removal

Michael Ng, Bahram Javidi, and Xiongjun Zhang

Doc ID: 280249 Received 08 Nov 2016; Accepted 05 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: In this paper, we propose an alternating minimization algorithm with an automaticselection of the regularization parameter for image reconstruction of photon-countedimages. By using the generalized cross-validation technique, the regularization parameter can beupdated in the iterations of the alternating minimization algorithm. Experimental results showthat our proposed algorithm outperforms the two existing methods including the maximumlikelihood expectation maximization estimator with total variation regularization and the primaldual method where their parameters must be set in advance.

Transversal aberrations at arbitrary Hartmann-planedistances: application in the least-squares fitting ofHartmann data

Alejandro Téllez-Quiñones, Daniel Malacara-Doblado, Zacarias Malacara-Hernandez, David Asael Gutiérrez-Hernández, and Daniel Malacara Hernandez

Doc ID: 280882 Received 15 Nov 2016; Accepted 04 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: In a previous work, we introduced the concept of transversal aberrations fU,Vg calculated at arbitraryHartmann-plane distances z = r [Applied Optics, 55, 2160-2168 (2016)]. These transversal aberrations canbe used to estimate the wave aberration functionW, as well as the classical transversal aberrations fX,Ygcalculated at a theoretical plane z = f ; where f is the radius of a reference semi-sphere. However, whenthe ray identification is difficult to achieve at z = f , the use of fU,Vg can be of great help. In the contextof a least-squares fitting of the Hartmann data, the use of fU,Vg is proposed by analyzing some simpleexamples for the case of aW with aberration terms up to the third order. These examples also consider thehypothesis f >> W, as presented in the majority of the optical applications.

Stacking illumination of a confocal reflector lightemitting diode automobile headlamp with anasymmetric triangular prism

Hsi-Chao Chen, Jia-Hao Zhou, and Yang Zhou

Doc ID: 280075 Received 07 Nov 2016; Accepted 04 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: A confocal reflector lamp with an asymmetric triangular prism was designed for a stacking illumination of lightemitting diode (LED) automobile headlamp fitting ECE R112 asymmetrical regulation. The optical system includesthree 1st elliptic reflectors, three 2nd parabolic reflectors and one asymmetric triangular prism. Three elliptic andparabolic reflectors were assembled with three confocal reflector modules; two modules projected the cut-off lineof 0o angle and the other module projected the cut-off line of 15o angle using of an asymmetric triangular prism. Theray tracing, optical simulation and mockup experiment results exhibited that the illumination distribution met theregulation of ECE R112 class B, and the ideal efficiency could reach 96.8% by theory. The tolerance analysis showedthe efficiency remained above 98% under the error values of ±0.2mm of the position of the LED light source, andthe y direction of the up-down movement was more sensitive than the x and z directions. The measurement resultsof mockup sample safety factor were all larger than 1.15 and supported the regulation of the ECE R112 Class B.

Research on artificial dielectric material for millimeter-wave imaging application

Jinbang wang, Hanxue MEI, Kui Yang, Lu Zhao, zhiguo liu, and Tao Zhang

Doc ID: 282660 Received 12 Dec 2016; Accepted 04 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: Material made of artificial molecules fabricated from cage-shaped granules of conductor (CGC) is introduced and its electrical and magnetic characteristics are presented. Its refractive index, calculated using complex relative permittivity and complex relative permeability, is 1.504 at 35 GHz. A two-element lens, consisting of a pair of spherical plano-convex lenses, was designed and fabricated by embedding CGC in PMMA. The active millimeter-wave (AMMW) imaging system was constructed with the two-element lens by having the curved surfaces face each other. Millimeter-wave (MMW) images of a right trapezoid and twin bars were obtained. The image quality was acceptable, proving that the CGC material has the ability to refract MMWs in MMW imaging and that ability contrasts with that of some traditional high polymer material.

High-accuracy absolute rotation rate measurements with a large ring laser gyro: establishing the scale factor

Robert Hurst, Marinus Mayerbacher, André Gebauer, Karl Schreiber, and John-Paul Wells

Doc ID: 277745 Received 27 Sep 2016; Accepted 03 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: Large ring lasers have exceeded the performance of navigational gyroscopes by several orders of magnitude and have become useful tools for geodesy. In order to apply them for tests in fundamental physics remaining systematic errors have to be significantly reduced. We derive a modified expression for the Sagnac frequency of a square ring laser gyro under Earth rotation. The modifications include corrections for dispersion (of both the gain medium and the mirrors), for the Goos-Hänchen effect in the mirrors, and for refractive index of the gas filling the cavity. The corrections were measured and calculated for the 16~m² Grossring laser located at the Geodetic Observatory Wettzell. The optical frequency and the free spectral range of this laser were measured, allowing unique determination of the longitudinal mode number, and measurement of the dispersion. Ultimately we find that the absolute scale factor of the gyroscope can be estimated to an accuracy of approximately 1 part in 10⁸.

Narrow band multifilter radiometer for Total OzoneContent measurements: MZS (Antarctica) campaign

Salvatore Scaglione, Danilo Zola, Francesca Menchini, and Ilaria Di Sarcina

Doc ID: 278514 Received 11 Oct 2016; Accepted 03 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: The importance of ground-based measurements of the Ultra Violet radiation has increased since the discoveryof the stratospheric ozone layer depletion. Spectroradiometers are the most widely used class of instruments,although the requirement to work in attended stations is sometimes limiting. In this work wepresent a filter radiometer, named F-RAD, with good optical stability, very short sampling time (1 minute)and proven reliability. The instrument is based on a stand-alone functioning , making it suitable for operationin hostile environments. The Total Ozone Column (TOC) was estimated by the irradiance ratio atwavelengths where the ozone absorbs the solar radiation and where the radiation is not absorbed. Directcorrelation between the TOC values estimated by F-RAD and by OMI was found, and the standard deviationsof the ratios between such values were calculated. Three wavelength ratios were identified to takeinto account the dependence of the measurements from the Solar Zenith Angle, AF−RAD(306.0 nm/325.3nm) for SZA < 50°, BF−RAD(309.9 nm/325.3 nm) and CF−RAD(317.5 nm/325.3 nm) for SZA > 50°. Consideringthe OMI ozone data as the reference values, the accuracy of the filter radiometer is estimated to be±4%. The data collected during the calibration campaign in Lampedusa (June-July 2009, Italy) and duringthe first Antarctica winter of the 2009-2013 measurement campaign at Mario Zucchelli Station (MZS)are reported. The Total Ozone Column measured by F-RAD instrument, by the Ozone Monitoring Instrumenton board of EOS-Aura satellite (NASA) and by the NOAA UV Monitoring Station in McMurdo(USA) are compared to asses the appropriateness of F-RAD for long term measurement campaign.

Beyond laser safety glasses: augmented reality inoptics laboratories

Franco Quercioli

Doc ID: 278757 Received 14 Oct 2016; Accepted 03 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: Blocking visibility of a laser beam after a pair of safety goggles have been worn is always an unpleasant experience.Working blindly is hard, sometimes even dangerous, and safety could be again at risk. A safe, clear view of the laserbeam path would be highly desirable.This paper presents a technique for laboratory laser safety, using a smartphone’s camera and display, inconjunction with an augmented reality headset to allow clear viewing of laser experiments without any risk oflaser eye injury. Use of the technique is demonstrated, and strengths and weaknesses of the solution are discussed.

Phase imaging and detection in pseudo-heterodyne s-SNOM measurements

Javier Alda, Camilo Moreno, Edward Kinzel, and Glenn Boreman

Doc ID: 279131 Received 19 Oct 2016; Accepted 03 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: When considering pseudo-heterodyne mode for the detection of the modulus and phase of the near-field from s-SNOM measurements, processing only the modulus of the signal may produce an undesired constraint in the accessible values of the phase of the near-field. A two-dimensional analysis of the signal provided by the data acquisition system makes it possible to obtain phase maps over the whole [0, 2π) range. This requires post-processing the data to select the best coordinate system in which represent the data along the direction of maximum variance. The analysis also provides a quantitative parameter describing how much of the total variance is included within the component selected for the calculation of the modulus and phase of the near field. The dependence of the pseudo-heterodyne phase results with respect to the mean position of the reference mirror is analyzed, and the evolution of the global phase is extracted from the s-SNOM data. The results obtained obtained from this technique compared well with the expected maps of the near-field phase obtained from simulations.

Optomechanical design of portable compact BTFmeasurement instrument

Jan Hosek, Vlastimil Havran, Sarka Nemcova, Jiri Bittner, and Jiri Cap

Doc ID: 279550 Received 07 Nov 2016; Accepted 03 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: Recent developments in optoelectronics and material processing techniques make it possible to designand produce a portable and compact measurement instrument for bidirectional texture function (BTF).Parallelized optics, on board data processing, rapid prototyping and other non-conventional productiontechniques and materials were the key to building an instrument capable of in situ measurements withfast data acquisition. We designed, built and tested a prototype of a unique portable and compact multicamerasystem for BTF measurement which is capable of in situ measurement of temporally unstablesamples. In this paper we present its optomechanical design.

Fourier domain post-acquisition aperture reshapingfrom a multi-focus stack

Julia Alonso

Doc ID: 278888 Received 17 Oct 2016; Accepted 03 Jan 2017; Posted 03 Jan 2017  View: PDF

Abstract: Computational optical imaging methods allows to extend the functionality of traditional cameras. Theshape of the aperture in an optical system determines the shape in which the out-of-focus points areblurred in a captured image. In this work we present a method in Fourier domain that allows, from anacquired multi-focus image stack, to synthesize images of a three-dimensional scene as if they had beenacquired with apertures with arbitrary shapes. Partially extended depth-of-field as well as all-in-focusimage reconstruction can be obtained as particular cases.

Effects of the Vertically Switching Electric Field on Optoelectronic Properties of Blue-Phase Liquid Crystal Cells Using the Director Model

Cheng-Yu Chi, SHI-HAO QIU, Guan-Jhong Lin, Tien-Jung Chen, Ying-Jay Yang, and Jin-Jei Wu

Doc ID: 277975 Received 30 Sep 2016; Accepted 02 Jan 2017; Posted 03 Jan 2017  View: PDF

Abstract: This study uses the director model to analyze the optoelectronic properties of polymer-stabilized blue phase liquid crystal (PS-BPLC). The director model revealed a linear relationship of refractive index change and the cosine squared of the angle between the LCs and the direction of the electric field. Moreover, we employed the simulations based on the Kerr effect and compared the results with those of the director model. The simulation results also show the high consistency with real circumstances. Consequently, it can be of great help to design BPLC displays and can be applied to make better strategies in developing the next generation LCD devices.

Creating adjustable uniform optical cages through polarization shaping in low NA optical system

Xiaocong Yuan, xiaoyu weng, Luping Du, and peng shi

Doc ID: 280009 Received 02 Nov 2016; Accepted 02 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: We propose a method to generate adjustable uniform optical cages with prescribe number and position along the optical axis in a low numerical aperture (NA) optical system. The uniform optical cages are the superposition of multiple dark and bright spots, which are of x- and y-polarized electric fields with neglected axial component obtained respectively by focusing an x-polarized vortex beam with topological charge 1 and a quasi y-polarized beam. By adjusting the number and position of the dark and bright spots with reversal radiation theory, valuable optical cages with uniformity up to 1, such as multiple optical cages, optical chain and optical tube, can be realized. Moreover, the influences of axial field to the quality of optical cages are also investigated. Numerical results show that an effective optical cage with uniformity up to 0.695 can be achieved even with NA close to 0.75. The generated optical cages may find valuable application in optical trapping of samples with large scale, which are difficult to be trapped under a high NA focusing condition.

Multiple self-mixing interferometry based on phase modulation and demodulation for vibration measurement

Chunlei Jiang, Xin Wen, Shuxin Yin, and Yunfei Liu

Doc ID: 274353 Received 02 Sep 2016; Accepted 02 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: In this paper, a high-precision and effective method of multiple self-mixing interference (MSMI) modulation anddemodulation is proposed. The MSMI signal is sinusoidal modulated by an electro-optic modulator. Then, the fourquadrantintegral technique is used to demodulate the modulated MSMI signal and reconstruct displacement of thevibration object. The four-quadrant integral technique is within a modulation period, the signal is integrated fourtimes, the integral system is operated by simple linear operations and can obtain the phase. This method not onlycan demodulate sinusoidal vibration but can also reconstruct an arbitrary wave. At the same time, withoutincreasing the hardware equipment and the complexity of the algorithm, the measurement accuracy of MSMI isdoubled than that of self-mixing interference. The simulation tests and experimental measurements are confirmedby conducting a series of experiments.

Single phase tunable white-light-emitting Sr3La(PO4)3:Eu2+, Mn2+ phosphor for white LEDs

shuqin lou, Zhijun Wang, Panlai Li, and Zhenggang Lian

Doc ID: 278930 Received 24 Oct 2016; Accepted 02 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: A novel near-ultraviolet excited white-light-emitting phosphor Sr3La(PO4)3:Eu2+, Mn2+ was synthesized by the solid-state method. Luminescence properties and the energy transfer mechanism were investigated in detail by the X-ray diffraction, photoluminescence spectra and decay curves. With the energy transfer between Eu2+ and Mn2+, a cold white light with chromaticity coordinates of (0.2790, 0.2273), correlated color temperature of 6501 K, Ra of 70, and external quantum efficiency of 35.5% was realized by changing the ratios of Eu2+ and Mn2+ in the Sr3La(PO4)3:Eu2+, Mn2+ phosphors. Resonant energy transfer from Eu2+ to Mn2+ ions has been demonstrated to be a dipole–dipole mechanism in Sr3La(PO4)3. The energy transfer efficiency increases with Mn2+ concentration increasing, and reaches the maximum of 55.6%.

Generation of a Frequency-Quadrupled Phase-Coded Signal Using Optical Carrier Phase Shiftingand Balanced Detection

Xuan LI, Zhao ShangHong, Shilong Pan, zihang zhu, kun qu, and tao lin

Doc ID: 280675 Received 11 Nov 2016; Accepted 02 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: A novel approach for photonic generation of a frequency-quadrupled phase-coded signal using optical carrier shifting andbalanced detection is proposed and demonstrated. The key component of the scheme is an integrated dual-polarizationquadrature phase shift keying (DP-QPSK) modulator. In the modulator, an RF signal is applied to the upper QPSKmodulator to generate high-order optical sidebands, while an electrical coding signal is applied to the bottom QPSKmodulator to perform optical carrier phase shifting. After that, a frequency-quadrupled phase-coded signal with an exact π-phase shift is generated through balanced detection. The proposed scheme has simple, compact structure and goodtunability. Besides, a phase-coded pulse can be directly obtained when a three-level rectangular coding signal is applied. Aproof-of-concept experiment is carried out. The generation of a 2-Gbit/s phase-coded signal with a frequency tuning from12.12 to 28 GHz is experimentally demonstrated, and the generation of a phase-coded microwave pulse is also verified.

Light splitting with imperfect wave plates

Dallin Durfee, Jarom Jackson, and James Archibald

Doc ID: 279468 Received 25 Oct 2016; Accepted 02 Jan 2017; Posted 03 Jan 2017  View: PDF

Abstract: We discuss the use of wave plates with arbitrary retardances, in conjunction with a linear polarizer, to split linearly polarized light into two linearly-polarized beams with an arbitrary splitting fraction. We show that for non-ideal wave plates, a much broader range of splitting ratios is typically possible when a pair of wave plates, rather than a single wave plate, is used. We discuss the maximum range of splitting fractions possible with one or two wave plates as a function of the wave plate retardances, and how to align the wave plates to achieve the maximum splitting range possible when simply rotating one of the wave plates while keeping the other one fixed. We also briefly discuss an alignment-free polarization rotator constructed from a pair of half-wave plates.

Space grating optical structure of the retina and RGB-color vision.

Norbert Lauinger

Doc ID: 278620 Received 27 Oct 2016; Accepted 02 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: Diffraction of light at the spatial cellular phase grating ONL (outer nuclear layer) of the retina could produce Fresnel near-field interferences in three RGB diffraction orders accessible to photoreceptors (Cones/Rods). At perpendicular light incidence the wavelengths of the RGB-diffraction orders in photopic vision – a fundamental R-wave with two G+B-harmonics – correspond to the peak-wavelengths of the spectral brightness sensitivity curves of the cones at 559nmR, 537nmG and 447nmB. In scotopic vision the R+G-diffraction orders optically fuse at 512nm, the peak-value of the rod’s spectral brightness sensitivity curve. The diffractive-optical transmission system with sender (resonator), space-waves and receiver antennae converts the spectral light components involved in imaging into RGB-space. The colors seen at objects are diffractive-optical products in the eye, as the German philosopher A. Schopenhauer predicted. They are secondly related to the overall illumination in object space. The RGB transmission system is the missing link optically managing the spectral tuning of the RGB photopigments.

On the measurement of fundamental mode bend loss in large-mode-area optical fibers

Changgeng Ye, Joona Koponen, Ville Aallos, Teemu Kokki, and Ossi Kimmelma

Doc ID: 279312 Received 24 Oct 2016; Accepted 01 Jan 2017; Posted 03 Jan 2017  View: PDF

Abstract: The measurement of fundamental mode bend loss is thoroughly studied in large-mode-area few-mode optical fibers. The influencing factors, including spectral properties of the light source, modal power content and cladding light, are experimentally investigated. Monte-Carlo simulations are performed to help understanding and illustrating the distribution of the variations. Practical guidelines and an example implementation are provided for precise and accurate measurements.

Development of a method to characterize chain -like aggregates in diffusion flames using dynamic light scattering

Tryfon Charalampopoulos and GUOCAI SHU

Doc ID: 280797 Received 22 Nov 2016; Accepted 31 Dec 2016; Posted 06 Jan 2017  View: PDF

Abstract: A new method is presented which can yield particle size distribution parameters and aspect ratio for chain-like aggregates in a diffusion flame using light scattering. Measurements of polarized and depolarized dynamic light scattering are carried out in a Fe (CO) 5 – seeded – CO - air diffusion flame as function of position above the reactor surface. The measurements are combined with the method of cumulants to yield both the translational and rotational diffusion coefficients of chain – like aggregates, along the central axis of the flame, in the temperature range 863 to 1087 degrees Kelvin. It is demonstrated that the laser beam Gaussian factor needs to be considered in the data analysis in order to obtain, physically meaningful results. In addition, the limitations of the approach are discussed.

Quantitative analysis of steel samples using laser-induced breakdown spectroscopy with an artificial neural network incorporating a genetic algorithm

Kuohu Li, Lianbo Guo, Jiaming Li, xinyan yang, Rongxing Yi, Xiangyou LI, Yongfeng Lu, and Xiaoyan Zeng

Doc ID: 279567 Received 26 Oct 2016; Accepted 30 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: In this work, a genetic algorithm (GA) was employed to select the intensity ratios of the spectral lines belong to the target and domain matrix elements, and then take these selected line-intensity ratios as inputs to construct an analysis model based on an artificial neural network (ANN), to analyze the elements Copper (Cu) and Vanadium (V) in steel samples. The results revealed that the root-mean-square errors of prediction (RMSEP) for the elements Cu and V can reach 0.0040 and 0.0039 wt%, respectively. Comparing to 0.0190 and 0.0201 wt% of the conventional internal calibration approach, the reduction rates of the RMSEP values reached 78.9% and 80.6%, respectively. These results indicate that the GA combining ANN can excellently execute the quantitative analysis in LIBS for steel samples and further improve the analytical accuracy.

Dispersion characteristics of suspended core fiber infiltrated with water

Ryszard Buczynski, Khoa Dinh, Lanh Chu Van, Van Cao, QUANG HO DINH, Mai Luu, and Marek Trippenbach

Doc ID: 278887 Received 31 Oct 2016; Accepted 30 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: In this paper we present study on dispersion characteristics in the suspended core fibers made of borosilicate of NC21A glass infiltrated with water. Replacement of air with water results in dramatic improvement of dispersion characteristics in fibers, valuable in the process of supercontinuum generation. A near-zero flat dispersion can be achieved in anomalous or normal dispersion range for various diameters of the cores.

Temporal super-resolution based on localization microscopy algorithm

tomer yaron, avi Klein, Hamootal Duadi, and Moti Fridman

Doc ID: 278800 Received 17 Oct 2016; Accepted 29 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: We investigate the resolution limits of time-lensesbased on four-wave mixing process and present superresolutiontechnique in the time domain based on localizationmicroscopy algorithm. Our temporal superresolutiontechnique retrieves features shorter by a factorof two than the resolution limit of the system. Wepresent both measured and calculated results of thesuper-resolution scheme and present calculated superresolutionof input signal with higher complexity.

Radiation force of a high-average-power laser and its effects on second harmonic generation

Haitao Liu, Yingchun Liang, Ruifeng Su, and Fuli Yu

Doc ID: 279289 Received 21 Oct 2016; Accepted 29 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: The radiation force of a high-average-power that caused by reflection at the input surface of a mounted KH2PO4 (KDP) crystal is studied, along with its effects on the second harmonic generation (SHG) efficiency of the laser beam. A comprehensive model incorporating principles of momentum transfer, mechanics, and optics is proposed, taking advantages of which the radiation force, mechanical stress within the KDP crystal that caused by the radiation force, and the SHG efficiency that affected by the stress are successively studied. Moreover, the effects of the intensity of the laser beam on the radiation force, the stress, and the SHG efficiency are determined. It demonstrates that high-average-power laser beam causes macroscopic radiation force, and further contributes negative effects to the SHG efficiency.

Tunable compensation of GVD-induced FM-AM conversion in front-end of high power laser

Rao Li, Wei Fan, Youen Jiang, Zhi Qiao, Peng Zhang, and Zunqi Lin

Doc ID: 279689 Received 31 Oct 2016; Accepted 29 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Group velocity dispersion (GVD) is the one of the main factors leading to frequency modulation (FM) to amplitude modulation (AM) conversion in the front-end of high power laser. In order to compensate the FM-AM modulation, the influence of GVD, which is mainly induced by the phase filter effect, is theoretically investigated. Based on the theoretical analysis, a high precision, high stability, tunable GVD compensatory using gratings is designed and experimentally demonstrated. The results indicate that the compensator can be implemented in the high power laser facility to compensate the GVD of fiber with a length between 200-500m when the bandwidth of phase modulated laser are 0.34nm or 0.58nm and central wavelength is in the range of 1052. 3217-1053.6008 nm. Due to the linear relationship between the dispersion and the spacing distance of gratings, the compensator can easily achieve close-loop feedback controlling. The proposed GVD compensator promises significant applications in the large laser facility especially in the future PZ fiber front-end of high power lasers.

Simulation of concave-convex imaging mirror system for development of a compact and achromatic full-field X-ray microscope

Jumpei Yamada, Satoshi Matsuyama, Yasuhisa Sano, and Kazuto Yamauchi

Doc ID: 279719 Received 28 Oct 2016; Accepted 29 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: We propose the use of two pairs of concave-convex mirrors as imaging optics for the compact full-field X-ray microscope with high resolution and magnification factors. The optics consists of two pairs of hyperbolic convex and elliptical concave mirrors with the principal surface near the object, consequently enabling the focal length to be 10 times shorter than conventional advanced Kirkpatrick–Baez mirror optics. This paper describes characteristics of the optics calculated by ray-tracing and wave-optical simulators. The expected spatial resolution is approximately 40 nm with a wide field of view of more than 10 μm and a total length of about 2 m, which may lead to the possibility of laboratory-sized, achromatic and high-resolution full-field X-ray microscopes.

Alternate optical desings for Head Mounted Displays with wide Field of View

Bo Chen and Alois Herkommer

Doc ID: 281102 Received 18 Nov 2016; Accepted 29 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: The widely applied head mounted display (HMD) design form is generally a prism with one surface in total internal reflection (TIR), which however limits the angle of the incident rays, and thus decrease the design freedom and affects the performance. To obtain better performance of the HMD optics, in this paper, two seldom used design forms of HMD systems are presented and compared to the standard TIR HMD optics. One of them is a catadioptric HMD system, consisting of one lens and two mirrors; the other is a prism HMD with different folding geometry. The designs are compared for a field of view of 40°×30°, however we also investigate systems with increased field of view of 50°×30°. The evaluation indicates good performance of our systems. Especially the prism with an alternate folding geometry has great advantages in both performance and size.

Propagation of Polarized Waves Through Bounded Composite Materials

Sajad Ghatrehsamani and Graham Town

Doc ID: 281299 Received 21 Nov 2016; Accepted 29 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: We describe a numerical model, based on a Monte-Carlo algorithm, to calculate the propagation of polarized waves through highly scattering micro-structured materials, and to properly account for the effect of both loss and boundaries. As an example, we investigate the impact of a strongly scattering object of air-polymer composite material on a broad band collimated source. We also calculate the depolarization of linearly polarized and circularly polarized waves escaping from the sample boundaries, especially at large scattering angles, and we showing how boundaries can modify the distribution and the polarization of the scattered waves propagating out of the sample.

Ballistic Targets Micro-motion and Geometrical Shape Parameters Estimation from Sparse Decomposition Representation of Infrared Signatures

Junliang Liu, Shangfeng Chen, Huanzhang Lu, and Bendong Zhao

Doc ID: 281094 Received 18 Nov 2016; Accepted 28 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Micro-motion dynamics and geometrical shape are considered to be essential evidence for infrared (IR) ballistic targets recognition. However, it is usually hard or even impossible to describe the geometrical shape of an unknown target with a finite number of parameters, which results in a very difficult task to estimate target micro-motion parameters from the imperfect or limited IR signals. Considering the shapes of ballistic targets are relatively simple, this paper explores a joint optimization technique to estimate micro-motion and dominant geometrical shape parameters from sparse decomposition representation of IR irradiance intensity signatures. By dividing an observed target surface into a number of segmented patches, an IR signature of the target can be approximately modeled as a linear combination of the observation IR signatures from the dominant segmented patches. Given this, a sparse decomposition representation of the IR signature is established with the dictionary elements defined as each segmented patch’s IR signature. Then, an iterative optimization method, based on batch second-order gradient descent algorithm, is proposed to jointly estimate target micro-motion and geometrical shape parameters. Experimental results demonstrate that the micro-motion and geometrical shape parameters can be effectively estimated using the proposed method, when the noise of IR signature is in an acceptable level, for example SNR > 0 dB.

Plasmonic characteristics of two vertically coupled graphene-coated nanowires integrated with substrate

Yaser Hajati and Morteza Hajati

Doc ID: 280217 Received 07 Nov 2016; Accepted 28 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: In this paper, we theoretically investigate the guiding properties of two vertically coupled cylindrical graphene-coated nanowire (GNW) integrated with a thin high-index dielectric substrate. We show that the plasmonic properties of the proposed structure can be effectively modulated by changing the thickness of the dielectric substrate, the nanowire radius, the gap distance between the substrate and GNWs, as well as the Fermi level of graphene. Through optimizing the geometric and structural parameters, surface plasmon mode with high optical performance and low propagation loss can be achieved in the studied structure. Compared with plasmon mode guided in single GNW over substrate, a highly improved figure of merit with nearly two-fold electric field enhancement can be yielded in double GNW over substrate counterpart.

Generation of double-scale pulse in a LD pumped Yb:Phosphate solid state laser

Sha Wang, Yan-biao Wang, Guoying Feng, and Shouhuan Zhou

Doc ID: 280580 Received 10 Nov 2016; Accepted 28 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: We have demonstrated a generation of the double-scale pulse in a SESAM mode locked Yb:Phosphate glass solid state laser. The double-scale pulse with spectrum bandwidth of 4.6 nm is obtained at a central wavelength of 1030 nm with maximum output power of 377 mW and 80 MHz repetition rate. The autocorrelation function of the double-scale pulse contained a 510 fs short peak and 12.51 ps long pedestal. To our best knowledge, this is the first demonstration of a double-scale pulse mode locked solid state laser.

Concentration dependent correlated scatteringproperties of Intralipid®-20% dilutions

Sujatha Narayanan Unni and Michael Raju

Doc ID: 272325 Received 26 Jul 2016; Accepted 28 Dec 2016; Posted 05 Jan 2017  View: PDF

Abstract: Dilutions of Intralipid-20% are widely used as optical phantoms for mimicking scattering properties ofturbid media like tissues. One of the frequently used methodologies for quantifying scattering coefficientand anisotropy of Intralipid-20% is the use of single particle Mie scattering theory which in factis not valid for non-tenuous media. Hence, two methodologies consisting of analytical wave theory andeffective medium theory, incorporating particle size distribution and concentration dependent correlatedscattering phenomena, are used to estimate effective scattering coefficient and anisotropy of Intralipid-20% dilutions (1% to 100% v/v) from 380 nm to 1000 nm.

Development of a compact optical absolute frequency reference for space with 10¯¹⁵ instability

Thilo Schuldt, Klaus Doeringshoff, Evgeny Kovalchuk, Anja Keetman, Julia Pahl, Achim Peters, and Claus Braxmaier

Doc ID: 278923 Received 17 Oct 2016; Accepted 28 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: We report on a compact and ruggedized setup for laser frequency stabilization employing Doppler-free spectroscopy of molecular iodine near 532 nm. Using a 30 cm long iodine cell in triple-pass configuration in combination with noise cancelling detection and RAM control, a frequency instability of 6 × 10¯¹⁵ at 1 s integration time and a Flicker noise floor below 3 × 10¯¹⁵ for integration times between 100 s and 1,000 s was found. A specific assembly-integration technology was applied for the realization of the spectroscopy setup, ensuring high beam pointing stability and high thermal and mechanical rigidity. The setup was developed with respect to future applications in space including high-sensitivity inter-spacecraft interferometry, tests of fundamental physics and navigation and ranging.

Robust laser stripe extraction for 3D reconstruction based on cross structrued light sensor

Leiying He, Shanshan WU, and Chuanyu WU

Doc ID: 274521 Received 26 Aug 2016; Accepted 28 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: A cross-structured light sensor architecture for 3D reconstruction was established. An improved center of massmethod was proposed for laser stripe extraction. For each initial laser stripe center point, the center of massmethod was performed along the normal direction that was calculated using the Hessian matrix. The normaldirections can be used to divide the laser stripe center points into two categories. Laser stripe extractionexperiments showed that the proposed method is fast and robust. 3D reconstruction of a cylinder was used toanalyze reconstruction accuracy, with relative accuracy of less than 0.15 mm. 3D reconstruction of a shoe lastshowed that cross-structured light sensors can obtain more abundant information than single-structured lightsensors.

Linear Variable Filters for NASA's OVIRS Instrument: Pushing the Envelope of Blocking

Karen Hendrix

Doc ID: 275237 Received 06 Sep 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: The NASA OVIRS spectrometer provides high resolving power spectra over a broad wavelength region: 0.4 – 4.3µm, in a compact assembly. Thick, complex blocker designs (up to 153µm, 1839 layers) and precision manufacturing enable this performance.

Study of propagation of vortex beams in aerosol optical medium

Alexey Porfirev, Mikhail Kirilenko, Svetlana Khonina, Roman Skidanov, and Victor Soifer

Doc ID: 277565 Received 26 Sep 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: A theoretical and experimental study of the propagation of vortex laser beams in a random aerosol medium is presented. The theoretical study is based on the extended Huygens-Fresnel principle with the generation of a random field, using the fast Fourier transform. The simulation shows that the stability of vortex beams to fluctuations of an optical medium falls with rising order of optical vortices. Moreover, a coherence length (radius) of the random medium is of great importance. The coherence radius extension affects adversely the conservation of a beam structure in the random medium. During further free-space propagation, increasing coherence enables to reduce negative effects of fluctuations for beams with high-value topological charges. Experimental studies in the random aerosol medium have shown that at small distances vortex beams mostly demonstrate lower stability than a Gaussian beam. However, at considerable distances, vortex beams start to demonstrate greater stability that may be explained by their capacity to be regenerated after they passed obstacles.

Analysis on expressible depth range of integral imaging based on degree of voxel overlap

Sung-Wook Min, Young Min Kim, and KiHong Choi

Doc ID: 278255 Received 17 Oct 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: This paper proposes a practical method to analyze expressible depth range of integral imaging system based onimage blur at defocused depths, which is one of the most noticeable image degradations, caused by overlaps amongvoxels in both real and focused mode. In order to obtain the preferably precise area of overlaps among voxels ateach depth, display pixels are regarded as surface light sources in the process of voxel size calculation. As acriterion for determining the range, we determine the tolerable limit of the overlaps among voxels to be at leastresolved from each other. Based on this principle, several mathematical expressions about the expressible depthrange can be derived in both real mode and focused mode, and their feasibilities are demonstrated by severalexperiments. The analyses are processed based on both wave optics and ray optics.

A 44 mJ, 2.1 μm single-frequency Ho:YAG amplifier

Quanxin Na, Chunqing Gao, Qing Wang, YIXUAN ZHANG, gao mingwei, Qing Ye, Yujia Wang, and zhang meng

Doc ID: 280784 Received 14 Nov 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: A single-frequency two-stage amplifier delivering up to 44 mJ at 2.1 μm is demonstrated. The first-stage amplifier is double-end-pumped by a 1.9 μm Tm:YLF laser, and is seeded with a 15 mJ single-frequency Ho:YAG laser operating at 200 Hz. The second-stage amplifier is end-pumped by another 1.9 μm Tm:YLF laser. The output pulse width from the second stage amplifier is 113 ns, with a beam quality of M2~1.32.

Simultaneous dual-wavelength Q-switched Nd:YAG laser at 1052 and 1073 nm

haifeng lin, wenzhang zhu, feibing xiong, and jianjian ruan

Doc ID: 280313 Received 07 Nov 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: We report a continuous-wave (CW) dual-wavelength Nd:YAG laser at 1052 and 1073 nm, for the first time to the best ofour knowledge, in free-running mode. The maximum output power reaches 6.64 W with slope efficiency of about 42.1%with respect to the absorbed power. Inserting a Cr:YAG saturable absorber, the dual-wavelength laser can operate in Qswitchingregime with maximum average output power of 880 mW. The minimum pulse width and the highest pulserepetition rate are 28 ns and 17.12 kHz, respectively. The dual-wavelength laser has potential to generate 5.7 THz wavevia difference frequency method.

Real-time image haze removal using an aperture-division polarimetric camera

Wenfei Zhang, Jian Liang, Liyong Ren, Haijuan Ju, EnShi Qu, Zhaofeng Bai, Yao Tang, and Zhaoxin Wu

Doc ID: 279988 Received 02 Nov 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Polarimetric dehazing methods have been proven to be effective in enhancing the quality of images acquired in turbid media. We report a new full-Stokes polarimetric camera, which is based on the division of aperture structure. We design a kind of automatic polarimetric dehazing algorithm and load it into the FPGA modules of our designed polarimetric camera, achieving a real-time image haze removal with an output rate of 25 fps. We demonstrate that the image quality can be significantly improved together with a good color restoration. This technique might be attractive in a range of real-time outdoor imaging applications such as navigation, monitoring and remote sensing.

Separation of foreground and background from light field using gradient information

Rae-Hong Park and Jae Young Lee

Doc ID: 279703 Received 31 Oct 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Nowadays, computer vision or machine vision applications using a light field camera have been increasinglystudied. However, the abilities that the light field camera has are not fully used in these applications. In this paper,we propose a direct separation method of the foreground and background using the gradient information, whichcan be used in various applications as a pre-processing. From an optical phenomenon that the bundles of rays fromthe background are flipped, we derive that the disparity sign of the background in the captured three-dimensionalscene has the opposite disparity sign of the foreground. Using the majority weighted voting algorithm based on thegradient information with the Lambertian assumption and the gradient constraint, the foreground and thebackground can be separated at each pixel. As a pre-processing, the proposed method can be used for variousapplications such as occlusion detection, saliency detection, disparity estimation, and so on. Experimental resultswith EPFL light field dataset and the Stanford Lytro light field dataset show that the proposed method achievesbetter performance in terms of the occlusion detection and thus can be effectively used as a pre-processing forsaliency detection and disparity estimation.

Active computational imaging for circumventing resolution limits at macroscopic scales

Prasanna Rangarajan, Indranil Sinharoy, Predrag Milojkovic, and Marc Christensen

Doc ID: 279599 Received 27 Oct 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Macroscopic imagers are subject to constraints imposed by the wave nature of light and the geometry of image formation. The former limits the resolving power while the latter results in a loss of absolute size and shape information. The suite of methods outlined in this work afford macroscopic imagers the unique ability to capture unresolved spatial detail while recovering topographic information. The common thread that binds these methods is the notion of imaging under patterned illumination. The notion is advanced further in developing computational imagers whose resolving power is decoupled from the constraints imposed by the collection optics and the image sensor. These imagers additionally feature support for multiscale reconstruction.

Modification of Degenerative Photoluminescence in Aged Monolayer WS2 by PC61BM Surface Processing

Yu Liu, Xin Zheng, Han Li, Zhongjie Xu, and Tian Jiang

Doc ID: 280454 Received 08 Nov 2016; Accepted 26 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Due to the unique physical properties, monolayer transition metal dichalcogenides (TMDCs) have been widely used in the applications of light-emitting devices (LED). However, monolayers of TMDCs undergo dramatic aging effects including intense degradation in the optical behavior, extensive cracking and severe quenching of the direct gap photoluminescence (PL), which seriously limits the device performance. In this study, we show that monolayer WS2 stored for three months even in the glovebox exhibits obvious degenerative PL with changed peak position, which can be attributed to the presence of large number of trions induced by the aging effect. PC61BM surface processing was employed to modify the surface of the aged monolayer WS2. As expected, higher uniformity in PL spectrum was obtained. Besides, PL peak wavelength was modified to be same with that of non-aged one and did not change even at higher excitation power. This strategy is shown to successfully suppress the formation of trion by transferring the excess electron from WS2 to PC61BM. The results demonstrate the feasibility of applying PC61BM surface modification to improve the performance of the LED based on monolayer WS2.

Design and Optimization for Main Support Structure of a Large Area Off-axis Three-mirror Space Camera

Lei Wei, Xiaoxue Gong, Dong Ma, and zhang lei

Doc ID: 277868 Received 30 Sep 2016; Accepted 26 Dec 2016; Posted 06 Jan 2017  View: PDF

Abstract: To ensure excellent dynamic and static performance of large-area, off-axis three mirror anti(TMA)-space cameras,and to realize a lighter weight for the entire system, truss support structure design is applied in this study. In contrast totraditional methods, this paper adopts topology optimization based on the solid isotropic materials with penalization(SIMP) method on the truss structure design. Through reasonable object function and constraint choice, optimal topologyresults that have concerned the effect of gravity in X, Y, Z axis are achieved. Subsequently, the initial truss structure isdesigned based on the results and manufacturing technology. Moreover, to reduce the random vibration response of thesecondary mirror and fold mirror without mechanical performance decline of the whole truss, a weighted optimizationof truss size is proposed and the final truss structure is achieved. Finite element (FEM) analysis and experiments haveconfirmed the reliability of the design and optimization method. The designed truss-structure camera maintains excellentstatic performance with the relative optical axis angle between the primary mirror and corresponding mirrors(secondary mirror and fold mirror) being less than 5.3’’. Dynamic performances, such as random and sinusoidal vibrationresponses, also met the requirements that the acceleration RMS value for mout points of fold mirror should be lessthan 20g and the primary frequency reached 97.2 Hz.

An ASIC Chipset Design to Generate Block-based Complex Holographic Video

Young-Ho Seo, Youn-Hyuk Lee, and Dong-wook Kim

Doc ID: 278313 Received 11 Oct 2016; Accepted 26 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: In this paper, we propose a new hardware architecture implemented using a VLSI (very large scaled integrated circuit) in an ASIC (application-specific integrated circuit) where block-based calculations are used to generate holograms. The proposed hardware is structured to produce a part of a hologram in the block units in parallel. A block of a hologram is calculated using an object point, and then the calculation is repeated for all object points to obtain intermediate results that are then accumulated to produce the final block of a hologram. This structure can be used to produce holograms of various sizes in real-time with optimized memory access. The proposed hardware was implemented using the Hynix 0.18μm CMOS technology of Magna Chip, Inc., and it has about 448K gate counts and a silicon size of 3.592×3.592 mm². It can generate complex holograms and can operate in a stable manner at a clock frequency of 200 MHz.

A Geometric Model for Independently Tilted Lens and Sensor with Application for Omnifocus Imaging

Indranil Sinharoy, Prasanna Rangarajan, and Marc Christensen

Doc ID: 278891 Received 17 Oct 2016; Accepted 26 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Optical imaging systems in which the lens and sensor are free to rotate about independent pivots offer greater degrees of freedom for controlling and optimizing the process of image gathering. However, to benefit from the expanded possibilities, we need an imaging model that directly incorporates the essential parameters. In this work, we propose a model of imaging that can accurately predict the geometric properties of the image in such systems. Furthermore, we introduce a new method for synthesizing an omnifocus (all-in-focus) image from a sequence of images captured while rotating a lens. The crux of our approach lies in insights gained from the new model.

Estimating phase shifts from three fringe patterns by use of cross-spectrum

Hongwei Guo and Haifei Ding

Doc ID: 278102 Received 03 Oct 2016; Accepted 26 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: In phase shifting technique, using self-calibrating algorithms allow us determining phases and phase shifts simultaneously, thus eliminating the errors caused by miscalibrations of phase shifters. However, it is difficult to estimate phase shifts when only three fringe patterns are available, because in which case the problem becomes under-determined. In this paper, we analyze the effects of phase shift errors on the calculated phases, and find that the phase shift errors introduce special correlations between different frequency components of the calculated phases. We measure these correlations by calculating the cross-spectrum of cis functions between the calculated phases and their trebles, and further define a single-valued objective function. A gradient-guided search strategy is used for minimizing this objective function, so that the phase shifts are estimated from three fringe patterns. The simulation and experimental results demonstrate that the newly proposed algorithm, in comparison with the existing correlation-based algorithms, has several advantages such as being insensitive to the ununiformities of the background intensities and the modulations, having a high stability, and offering an improved computational efficiency.

Holographic micro-information hiding

Tomoyoshi Shimobaba, Yutaka Endo, Ryuji Hirayama, Daisuke Hiyama, Yuki Nagahama, Satoki Hasegawa, Marie Sano, Takayuki Takahashi, Takashi Kakue, Minoru Oikawa, and Tomoyoshi Ito

Doc ID: 274124 Received 23 Aug 2016; Accepted 26 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: We propose a holographic micro information hiding scheme in which the embedding information to be embedded is small and imperceptible to the human eyes.This scheme converts the embedding information into a complex amplitude via scaled diffraction.The complex amplitude of the reduced embedding information is added to the complex amplitude of the host image, followed by conversion to a hologram.The reduced embedded information is inconspicuous from the hologram during the reconstruction process; however, the reduction leads to the degradation of the embedded image quality.Therefore, to improve the quality of the embedded image quality, we employ iterative optimization and the time averaging effect of multiple holograms.

High-speed Pulse Train Amplification in SemiconductorOptical Amplifiers with Optimized Bias Current

Hooshang Ghafouri-Shiraz, Mingjun Xia, Lianping Hou, and Anthony Kelly

Doc ID: 277735 Received 21 Oct 2016; Accepted 24 Dec 2016; Posted 05 Jan 2017  View: PDF

Abstract: In this paper we have experimentally investigated the optimized bias current of semiconductor optical amplifiers (SOAs)in order to achieve the high-speed input pulse train amplification with high gain and low distortion. Variations of theamplified output pulse duration with the amplifier bias currents have been analyzed and it is found that compared withthe input pulse duration, the amplified output pulse duration is broadened; as the SOA bias current decreases from thehigh level (larger than the saturated bias current) to the low level, the broadened pulse duration of the amplified outputpulse initially decreases slowly and then rapidly. Based on the analysis, an optimized bias current of SOA for high-speedpulse train amplification is introduced. The relations between the SOA optimized bias current and the parameters of theinput pulse train (pulse duration, power and repetition rate) are experimentally studied. It is found that the larger inputpulse duration, the lower input pulse power or the higher repetition rate can lead to a larger SOA optimized bias current,which corresponds to a larger optimized SOA gain. The effects of assist light injection and different amplifiertemperatures on the SOA optimized bias current are studied and it is found that assist light injection can effectivelyincrease the SOA optimized bias current while SOA has the lower optimized bias current at the temperature 20°C thanthat at other temperatures.

Frequency domain computation of steady state modes of optoelectronic oscillators with stability analysis

Sajad Jahanbakht

Doc ID: 281062 Received 17 Nov 2016; Accepted 23 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: A frequency domain approach for computing all of the steady state modes of single-loop optoelectronic oscillators (OEOs) corresponding to the exact parameter values, especially the fiber length, is presented. Computing these modes is useful in designing single mode OEOs and analyzing the effects of these modes on the phase noise performance. This computation is also useful in analyzing injection-locked OEO systems where the locking state depends on the values of oscillation frequencies and power levels of the steady state modes of the OEOs involved. The proposed steady-state computation approach requires a much smaller amount of run-time compared to time domain methods; however, its results have to be checked for stability. Two stability analysis schemes, one based on the frequency domain Nyquist stability analysis and the other based on solving a slowly-varying perturbation system in the time domain are presented. The validities of these schemes are verified by comparing their results with each other, with full time domain integrations and with previously published results. It is shown that the modes of a single-loop OEO computed by the presented approach are either stable or unstable which justifies the need to use the proposed stability analysis schemes. Simulations show that the unstable modes ultimately converge to the dominant mode, i.e. the mode with the largest small signal loop gain. The effect of exciting any mode on the phase noise is also investigated through simulations.

Nonuniformity correction based on focal plane array temperature in uncooled Long-Wave infrared cameras without a shutter

Bo Zhou, Kun Liang, Cailan yang, and Li Peng

Doc ID: 280155 Received 04 Nov 2016; Accepted 22 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: In uncooled long-wave infrared (LWIR) camera systems, the temperature of a focal plane array (FPA) is variable along with the environmental temperature as well as operating time. The spatial nonuniformity of FPA, which is partly affected by the FPA temperature, obviously changes as well, resulting in reduced image quality. This study presents a real-time nonuniformity correction algorithm based on FPA temperature to compensate for nonuniformity caused by FPA temperature fluctuation. First, gain coefficients are calculated by using a two-point correction technique. Then offset parameters at different FPA temperatures are obtained and stored in tables. When the camera operates, the offset tables are called to update the current offset parameters by a temperature-dependent interpolation. Finally, the gain coefficients and offset parameters are used to correct the output of the infrared camera in real time. The proposed algorithm is evaluated and compared with two representative shutter-less algorithms (minimizing the sum of the squares of errors algorithm, MSSE; template-based solution algorithm, TBS) using infrared images captured by a 384×288-pixels uncooled infrared camera with a 17-μm pitch. Experimental results show that this method can timely trace the response drift of detector units when the FPA temperature changes. The quality of the proposed algorithm is as good as MSSE while the processing time is as short as TBS, which means the proposed algorithm is good for real-time control and at the same time has high correction effect.

An Enhanced MMW and SMMW/THz Imaging System Performance Prediction and Analysis Tool for Concealed Weapon Detection and Pilotage Obstacle Avoidance

Steven Murrill, Charmaine Franck, Eddie Jacobs, Douglas Petkie, and Frank De Lucia

Doc ID: 272931 Received 02 Aug 2016; Accepted 22 Dec 2016; Posted 23 Dec 2016  View: PDF

Abstract: The U.S. Army Research Laboratory (ARL) has continued to develop and enhance a millimeter-wave (MMW) andsub-millimeter-wave (SMMW)/terahertz (THz)-band imaging system performance prediction and analysis tool forboth the detection and identification of concealed weaponry, and for pilotage obstacle avoidance. The details of theMATLAB-based model which accounts for the effects of all critical sensor and display components, for the effects ofatmospheric attenuation, concealment material attenuation, active illumination, target & background orientation,target & background thermal emission, and various imaging system architectures have been reported on in 2005,2007, and 2011. This paper provides a comprehensive review of a newly enhanced MMW and SMMW/THz imagingsystem analysis and design tool that now includes an improved noise sub-model for more accurate and reliableperformance predictions, the capability to account for post-capture image contrast enhancement, and thecapability to account for concealment material backscatter with active-illumination-based systems. Present plansfor additional expansion of the model’s predictive capabilities are also outlined.

Free-form surface generation in a double pole coordinate system for off-axis illumination application

Donglin Ma, XiuHua Yuan, and Rongguang Liang

Doc ID: 275639 Received 12 Sep 2016; Accepted 21 Dec 2016; Posted 23 Dec 2016  View: PDF

Abstract: We apply the previously proposed double pole ray mapping technique to design a non-symmetrical optical surface for generating off-axis rectangular illumination pattern, which is aimed for road luminaire. This paper explores the methods to determine the edges of unsymmetrical collection solid angle in the source space for different target requirements by taking the mechanical structures of optical surfaces into consideration. By sampling source grids within the defined region in double pole coordinate system, we achieve a nearly perfect mapping between source and target with a high uniformity for the off-axis rectangular illumination pattern. The testing result of the prototyped freeform lens also shows a good illumination performance, consistent with our simulation result. Besides, the tolerance analysis of the luminaire system is performed to understand the sensitivity of LED’s position on illumination performance.

Elliptic Visualizing Optical Resolution and Kinetic Energy

Nils Abramson

Doc ID: 275374 Received 20 Sep 2016; Accepted 21 Dec 2016; Posted 21 Dec 2016  View: PDF

Abstract: Diffraction limited resolution as introduced by Abbe is well established, but interference limited resolution was not well known until holographic interferometry was introduced. The Holodiagram is used to simplify holography and in a new way visualize the distribution, ratio and relation between resolutions of different optical techniques, including relativistic phenomena. Resolution, when measured by optical methods based on the number of wavelengths of light, is in the following defined as the minimum distance between resolvable points, or the largest object needed to be resolved. Everywhere in the diagram this resolution is represented by two orthogonal diagonals of rhombs.

Effects of Cell Gap on the Optoelectronic Properties of Pure Blue Phase Liquid Crystal Devices: Estimating the Kerr Constant

Jin-Jei Wu, Cheng-Yu Chi, Guan-Jhong Lin, Shui-Shang Hu, Sin-Yan Tsai, Tien-Jung Chen, Ja-Hon Lin, and Ying-Jay Yang

Doc ID: 278838 Received 26 Oct 2016; Accepted 21 Dec 2016; Posted 21 Dec 2016  View: PDF

Abstract: In this study, the Kerr constant of pure blue phase liquid crystal (BPLC) without polymer doping at room temperature, and the optoelectronic properties dependent on the cell thickness are explored. The relation between the phase and the voltage in oblique incident light was measured via a reasonable vertical electric field for different thicknesses of BPLC cells. It was found that the Kerr constant formula can be amended with the functions related to the cell-gap. This study demonstrates a method to estimate the Kerr constant, especially for cells within a small electrical field, which will benefit optoelectronic applications.

AdjacencyEffectsinsatelliteradiometricproductsfromcoastalwaters:atheoreticalanalysisforthenorthernAdriaticSea

Barbara Bulgarelli, Viacheslav Kiselev, and Giuseppe Zibordi

Doc ID: 273162 Received 14 Nov 2016; Accepted 21 Dec 2016; Posted 22 Dec 2016  View: PDF

Abstract: Biases induced by land perturbations in satellite derived water-leaving radiance are theoretically estimated for typical observation conditions in a coastal area of the northern Adriatic Sea. Two different correction procedures, alternatively deriving (AC-1) or not (AC-2) the atmospheric properties from the remote sensing data, are considered. In both cases, biases due to adjacency effects largely increase by approaching the coast and with the satellite zenith angle, while seasonal and spectral dependence significantly differ. For AC-1 schemes average biases exceed – and +5% only at blue and red wavelength, respectively. For AC-2 schemes, adjacency effects at those wavelengths from which atmospheric properties are inferred add significant perturbations. For the specific case of a correction scheme deriving the atmospheric properties from the NIR region and by adopting a power-law spectral extrapolation of adjacency perturbations on the derived atmospheric radiance, average biases become all negative with values up to -60% and -74% at 412 and 670 nm at the coast, respectively. The seasonal trend of estimated biases at a specific validation site is consistent with intra-annual variation of overall biases from match-ups between in situ and satellite products derived with SeaDAS from SeaWiFS and MODIS data. Nevertheless, estimated biases at blue wavelengths exceed systematic differences determined from match-ups analysis. This may be explained by uncertainties and approximations in the simulation procedure, and by mechanisms of compensation introduced by the turbid water correction algorithm implemented in SeaDAS.

All-fiber passively Q-switched 604 nm praseodymium laser with a Bi2Se3 saturable absorber

Zhiping Cai, Huiyu Lin, Wensong Li, Jinglong Lan, Xiaofeng Guan, and Huiying Xu

Doc ID: 280921 Received 16 Nov 2016; Accepted 21 Dec 2016; Posted 22 Dec 2016  View: PDF

Abstract: We experimentally demonstrated a simple passively Q-switched praseodymium (Pr3+) -doped all-fiber laser at 604 nm with Bi2Se3 saturable absorber (SA). A Bi2Se3/polyvinyl alcohol (PVA) composite film is sandwiched between two ferrules to construct a fiber-compatible Q-switcher. Two fiber end facet mirrors build a compact-linear resonator. The repetition rate of the achieved 604 nm Q-switching pulse can be widely tuned from 86.2 to 187.4 kHz and the pulse duration can be as narrow as 494 ns. To the best of our knowledge, this is the shortest operation wavelength of Bi2Se3-based pulsed all-fiber laser at 604nm.

High brightness, low coherence, digital holographic microscopy for 3D visualization of in-vitro sandwiched biological sample

Dahi Abdelsalam and Takeshi Yasui

Doc ID: 279673 Received 28 Oct 2016; Accepted 20 Dec 2016; Posted 21 Dec 2016  View: PDF

Abstract: We achieve practically a bright-field digital holographic microscopy (DHM) configuration free from coherent noise for 3D visualization of in-vitro sandwiched sarcomere sample. Visualization of such sandwiched samples by conventional atomic force microscope (AFM) is impossible, while visualization using DHM with long coherent lengths is challenging. The proposed configuration is comprised of an ultrashort pulse laser source and a Mach-Zehnder interferometer in transmission. Periodically-poled-lithium-niobate (PPLN) crystal was used to convert the fundamental beam by second harmonic generation (SHG) to the generated beam fit to the CCD camera used. The experimental results show that the contrast of the reconstructed phase-image is improved to a higher degree compared to a He-Ne laser-based result. We attribute this improvement to 1) the feature of the femtosecond pulse light, which acts as a chopper for coherent noise suppression and 2) the fact that the variance of a coherent mode can be reduced by a factor of 9 due to low loss through a nonlinear medium.

Spectral Unmixing Method for Multi-Pixel Energy Dispersive X-ray Diffraction System

Li Zhang and Tianyi YangDai

Doc ID: 278014 Received 03 Oct 2016; Accepted 20 Dec 2016; Posted 21 Dec 2016  View: PDF

Abstract: An algorithm of spectral unmixing (SU) is presented, allowing the improvement of material classification accuracybased on the low spatial resolution images obtained by multi-pixel energy dispersive x-ray diffraction (EDXRD)systems. The method, which consists of signal subspace identification and endmember extraction, performs verywell even when the pixel count is rather small. EDXRD combined with SU has been utilized for liquid securityscreening for the first time. The spectra and abundance distributions of endmembers are extracted from themeasured data sets corresponding to objects of different material composition, which demonstrates the validity ofthe proposed method.

Glass Processing with Pulsed CO₂ Laser Radiation

Christian Weingarten, Emrah Uluz, Andreas Schmickler, Karsten Braun, Edgar Willenborg, André Temmler, and Sebastian Heidrich

Doc ID: 264078 Received 03 Nov 2016; Accepted 20 Dec 2016; Posted 20 Dec 2016  View: PDF

Abstract: Recent results of processing fused silica using a high power Q-switch CO2 laser source with a maximum output power of 200 W are presented. Compared to the processing with continuous wave (cw) laser radiation, the main advantage of pulsed laser radiation is the influence of the light-matter interaction with high laser peak power at small average laser power. An application for the approach presented in this paper is the flexible manufacturing and form correction of optics. This laser based process is nearly independent of the surface geometry and can even be enhanced by laser polishing and expanded to other glass materials. Hence, the high power Q-switch CO2 laser source is used to ablate glass material with an ablation rate up to 2.35 mm³/s and also for ablating glass material locally in a vertical dimension down to 3 nm.

Modified Twin-Spot Launching: An Improved launchingTechnique for Enhancing Data Rates in MultimodeFiber

Thomas Joseph and Joseph John

Doc ID: 280620 Received 10 Nov 2016; Accepted 20 Dec 2016; Posted 20 Dec 2016  View: PDF

Abstract: Compiled December 20, 2016Several launching techniques such as center launching, offset launching, mode field diameter matchedcenter launching, twin-spot launching, etc. have been employed in the past to reduce modal dispersion inmultimode fibers (MMF). Unfortunately all these methods require stringent alignment accuracy of inputbeam with the fiber axis. In this paper we propose a new optical launching method, viz. mode field diametermatched twin-spot launching (MFDM-TSL) technique, which combines the desirable features of twoearlier techniques so as to excite only the fundamental mode in an MMF with much higher misalignmenttolerance compared to the existing launching techniques. Also we derive for the first time an analyticalexpression for power coupling coefficients of the excited modes in an infinite parabolic refractive indexprofiledMMFunder twin-spot launching. The proposed technique can excite the fundamental mode withmore than 9 dB extinction ratio at 1300 nm even though the two beams are at a lateral offset position of5 μm from the axis, i.e. 10 μm apart. Additionally it is tolerant to variations in the mode field diameter(MFD), relative positions, power and phase of the input beams. The comprehensive analysis shows cancellationof the odd/even symmetrical mode groups in an MMF depending on the relative phase of theinput beams which results in reduced group-delay differences of the excited mode groups.

Validation of Modeled Sparse Aperture Post-Processing Artifacts

Philip Salvaggio, John Schott, and Donald McKeown

Doc ID: 272062 Received 21 Jul 2016; Accepted 19 Dec 2016; Posted 20 Dec 2016  View: PDF

Abstract: Sparse aperture imaging introduces a number of interesting image quality issues. Just as with traditional systems, resolution, signal-to-noise ratio and post-processing are all relevant to image quality. This work will examine post-processing artifacts that arise in sparse aperture imagery, which are more complex than the edge-overshoot artifacts that appear in traditional imagery. Modeling has predicted the existence of these artifacts and this work will verify that prediction with real data. Artifacts rising from various causes will be examined and it will be established that model predictions can be used in future trade studies regarding artifacting.

High-quality Mach-Zehnder interferometer based on a micro-cavity in single-multi-single mode fiber structure for refractive index sensing

Shiliang Qu, Yi Liu, Guoqiang Wu, and Renxi Gao

Doc ID: 274285 Received 23 Aug 2016; Accepted 19 Dec 2016; Posted 19 Dec 2016  View: PDF

Abstract: A fiber in-line Mach-Zehnder interferometer (MZI) based on a micro-cavity with two symmetric openings in single-multi-single mode fiber (SMSF) structure was proposed. The interference spectrum simulation result by using FD-BPM method shows that the MZI can still be with high-quality interference even if the micro-cavity deviates along the radial direction for 3μm. Therefore it allows larger fabrication tolerance and tremendously decreases the fabrication difficulty. Then a micro-cavity with two symmetric openings in SMSF was fabricated by using femtosecond laser induced water breakdown. The insertion loss of the micro-cavity immerged in water is only -8dB and the MZ interference peak contrast in transmission spectrum reaches more than 30dB. The MZI based on the micro-cavity in SMSF can be used as a practical liquid refractive index sensor as its high-quality interference spectrum, ultrahigh sensitivity (9756.75 nm/RIU), high refractive index resolution (2×10−5 RIU), good linearity (99.93%), and low temperature crosstalk (0.04 nm/°C).

Accurate and robust calibration method based onpattern geometric constraints for fringe projectionprofilometry

Peng Wang, Peng Lu, Changku Sun, and Bin Liu

Doc ID: 279181 Received 20 Oct 2016; Accepted 19 Dec 2016; Posted 19 Dec 2016  View: PDF

Abstract: In fringe projection profilometry (FPP), the relationship between phase and height is of uttermost significanceto perform the accurate measurement. To enhance accuracy and robustness, a calibration methodis presented based on pattern geometric constraints. By analyzing the pattern distribution in the imagecoordinate, this method establishes one-to-one mapping relationship between phase and height directly,and the lens distortion of camera is considered and involved in the mathematical description, so as toeliminate error propagation. (x, y) coordinates are calculated from camera calibration with known heightvalues. This method is practical for the reason that strict system constraints is not needed and its calibrationprocedure is efficient. Experiments including error evaluation and robustness evaluation are conductedto verify its accuracy and robustness respectively. The results reveal that this method has desiredproperties of high accuracy and strong robustness. These performances guarantee its flexibility underdifferent circumstances.

Derivation of the correlation diffusion equation withstatic background and analytical solutions

Tiziano Binzoni, Alwin Kienle, Fabrizio Martelli, and Andre Liemert

Doc ID: 279576 Received 26 Oct 2016; Accepted 18 Dec 2016; Posted 19 Dec 2016  View: PDF

Abstract: A new correlation diffusion equation has been derived from a correlation transport equation allowingto take into account for the presence of moving scatterers and static background. Solutions for thereflectance from a semi-infinite medium have been obtained (point-like and ring detectors). The solutionshave been tested by comparisons with “gold standard” Monte Carlo (MC) simulations. These formulassuitably describe the electric field autocorrelation function, for Brownian or random movement of thescatterers, even in the case where the probability for a photon to interact with a moving scatterer is verylow. The proposed analytical models and the MC simulations show that the “classical” model, oftenused in diffuse correlation spectroscopy, underestimates the normalized field autocorrelation functionfor increasing correlation times.

Launch Light Dependency of Step-Index Multimode Fiber Connections Analyzed by Modal Power Distribution Using Encircled Angular Flux

Shigeru Kobayashi, Manabu Yasukawa, and Okihiro Sugihara

Doc ID: 274062 Received 17 Aug 2016; Accepted 18 Dec 2016; Posted 19 Dec 2016  View: PDF

Abstract: The propagating modal power distribution (MPD) of step-index multimode fibers (SI-MMFs), which strongly influences the performance of systems and components composed of these fibers, has not often been discussed, because, until recently, there has been no definition to show the MPD. Encircled angular flux (EAF) is a newly developed metric for defining the MPD in step-index multimode waveguides including fibers standardized by the International Electrotechnical Commission. Using the combined analysis of EAF and insertion loss, we studied the launch light dependency of SI-MMF connections. Our studies contribute to enhance both current applications and future higher data rate communications using SI-MMFs.

GRIN optofluidic waveguide in PDMS

Mutasem ODEH, BOB VOORT, Arslan Anjum, Marcus Dahlem, Clara Dimas, and Bruna Paredes

Doc ID: 278666 Received 17 Oct 2016; Accepted 11 Dec 2016; Posted 04 Jan 2017  View: PDF

Abstract: We demonstrate a gradient-index (GRIN) optofluidic waveguide using polydimethylsiloxane (PDMS) cured with a radial variation of temperature. The waveguide wraps the microfluidic channel and the GRIN profile localizes the light around it, making the device suitable for evanescent sensing applications. The fabricated waveguide shows good light confinement, with a propagation loss of 1.47 dB/cm at a wavelength of 632.8 nm.

Comparison of low cost 3D structured light scanners for face modeling

TOLGA BAKIRMAN, Mustafa Gumusay, Hatice Catal Reis, Serra Yosmaoglu, Mehmet Yaras, Dursun Seker, and Bülent Bayram

Doc ID: 279048 Received 18 Oct 2016; Accepted 10 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: This study aims to compare three different structured light systems to generate accurate 3D human face models. Among these systems, the most dense and expensive one was selected as the reference and the other two that were low cost and low resolution were compared according to the reference system. One female and one male face were scanned with the mentioned instruments at different times. Point cloud filtering, mesh generation and hole filling steps were carried out using a trial version of a commercial software; moreover, the data evaluation process was realized using a piece of open source software. Various filtering and mesh smoothing levels were applied and the acquired results were analyzed for comparison purposes. This study proposes an effective data reduction procedure. The proposed processing steps for data reduction can be used for all kinds of point cloud data. Additionally, reliable data processing phases for 3D face modeling have been described. 3D human face models were created using three different resolution structured light scanners. The study shows that low-cost structured light scanners have a great deal of potential for 3D object modeling, including the human face. This study proposes a method for optimal data reduction and a data processing methodology for high and low resolution structured light systems, which can be applied for any point cloud processing related studies. An extremely inexpensive structured light system has been used due to its capacity to obtain spatial and morphological information in case study of 3D human face modelling. This study also discusses the benefits and accuracy of low-cost structured light systems.

Time-resolved thermal lens spectroscopy with single-pulsed laser excitation beam: An analytical model for dual-beam mode-mismatched experiments

Mohammad Sabaeian, Hamidreza Rezaei, and Abdolmohammad Ghalambor-Dezfouli

Doc ID: 272186 Received 26 Jul 2016; Accepted 08 Dec 2016; Posted 12 Dec 2016  View: PDF

Abstract: The pulsed laser beam excitations are more commonly used in thermal lens spectroscopy (TLS) than continuous-wave (CW) ones, because CW excitations limit the measurement to linear absorption processes [Marcano et al., J. Opt. A: Pure Appl. Opt. 5, 256 (2003)]. In this work, for the first time, we present a new and full analytical model for a single-pulsed laser excitation dual-beam mode-mismatched TLS for low absorption solid-state and liquid samples. Our model has been based on a new solution of time-dependent heat equation for a finite radius cylindrical sample exposed to a single-pulsed excitation laser beam. For low absorbent samples, unlike previous models, all aberration terms associated in the thermal lens were taken into account in Fresnel integration. Besides, the model provides a full analytical mathematical expression for the temperature rise, normalized signal intensity, and Z-scan photo-thermal lens signal (PTLS). The model was confirmed with experimental data of distilled deionized water with excellent agreement. Therefore, the model allows us to extract thermo-optical properties of samples in an analytical and more accurate way.

Image Multiplexing and Encryption Using Non-negative Matrix Factorization Method Adopting Digital Holography

Hsuan-Ting Chang, Jr-Wei Shui, and K.-P. Lin

Doc ID: 272761 Received 06 Sep 2016; Accepted 08 Dec 2016; Posted 12 Dec 2016  View: PDF

Abstract: In this paper, a joint multiple-image encryption and multiplexing system, which utilizes both the non-negative matrix factorization (NMF) scheme and digital holography, is proposed. A number of images are transformed into noise-like digital holograms, which are then decomposed into a defined number of the basis images and the corresponding weighting matrix using the NMF scheme. The determined basis images are similar to the digital holograms and appear as noise-like patterns, which are then stored as the encrypted data and serve as the lock in an encryption system. On the other hand, the column vectors in the weighting matrix serve as the keys for the corresponding plain images or the addresses of the multiplexed images. Both the increased uniformity of the column weighting factors and the parameters used in the digital holography enhance the security of the distributed keys. The experimental results shows that the proposed method can successfully perform multiple-image encryption with high-level security.

Model-based optimization of near-field binary-pixelated beam shapers

Christophe Dorrer and Jeremy hassett

Doc ID: 278283 Received 07 Oct 2016; Accepted 05 Dec 2016; Posted 08 Dec 2016  View: PDF

Abstract: The optimization of components that rely on spatially dithered distributions of transparent or opaque pixels and an imaging system with far-field filtering for transmission control is demonstrated. The binary-pixel distribution can be iteratively optimized to lower an error function that takes into account the design transmission and the characteristics of the required far-field filter. Simulations using a design transmission chosen in the context of high-energy lasers show that the beam-fluence modulation at an image plane can be reduced by a factor 2, leading to performance similar to using a non-optimized spatial dithering algorithm with pixels of size reduced by a factor 2 without the additional fabrication complexity or cost. The optimization process preserves the pixel distribution statistical properties. Analysis shows that the optimized pixel distribution starting from a high-noise distribution defined by a random-draw algorithm should be more resilient to fabrication errors than the optimized pixel distributions starting from a low-noise, error-diffusion algorithm while leading to similar beam-shaping performance. This is confirmed by experimental results obtained with various pixel distributions and induced fabrication errors.

Relationship Analysis between Transient Thermal Control Mode and Image Quality for Aerial Camera

weiyi liu, Yulei Xu, Yuan Yao, yongsen xu, and Shen Honghai

Doc ID: 267116 Received 26 May 2016; Accepted 25 Nov 2016; Posted 04 Jan 2017  View: PDF

Abstract: Thermal control and temperature uniformity are important factors for aerial cameras. This paper describes the problems with existing systems and introduces modifications. The modifications have improved the temperature uniformity from 12.8℃ to 4.5℃, and they enable images to be obtained at atmospheric and low pressures (35.4 KPa). Firstly, thermal optical analysis of the camera is performed by using finite element analysis method. This modeled the effect of temperature level and temperature gradient on imaging. Based on the results of the analysis, the corresponding improvements to the thermal control measures are implemented to improve the temperature uniformity. The relationship between temperature control mode and temperature uniformity is analyzed. The improved temperature field corresponding to the thermal optical analysis is studied. Taking into account that the convection will be affected by the low pressure, the paper analyzes the thermal control effect and imaging results are obtained in low pressure. The experimental results corroborate the analyses.

Reactive Dynamics Analysis of Critical Nb2O5 Sputtering Rate for Drum Based Metal-like Deposition

Shigeng Song, CHENG LI, Hin On Chu, and Des Gibson

Doc ID: 274926 Received 30 Aug 2016; Accepted 11 Oct 2016; Posted 11 Oct 2016  View: PDF

Abstract: Drum based metal-like film deposition for oxide was investigated using single wavelength in-situ monitoring. The data was used to investigate oxidation mechanism using combined second order kinetic and parabolic models. A critical Nb2O5 deposition rate of 0.507nm/s was found at drum rotation 1rev/s. However, N2O5 samples prepared at varying deposition rates showed deposition rate must be much lower than critical deposition rate to achieve reasonable absorption. Thus simulation for volume-fraction of metal in oxide layer was done using EMA and distribution function. Simulation gave high agreement with experimental results, and allows prediction of extinction coefficients at various deposition rates.

Dependence of depth of focus on spherical aberration of optical systems

Antonin Miks and Jiri Novak

Doc ID: 267338 Received 31 May 2016; Accepted 05 Jul 2016; Posted 06 Jul 2016  View: PDF

Abstract: This paper presents a theoretical analysis and computation of aberration coefficients of the third and fifth order of transverse spherical aberration of an optical system, which generates a ray bundle with a diameter of a geometric-optical circle of confusion smaller than a predetermined limit value. Equations were derived for the calculation of aberration coefficients of an optical system, which satisfy given conditions, and for the determination of the maximum possible depth of focus for given conditions.

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