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Accepted papers to appear in an upcoming issue

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Identifying sampling comb changes in Fourier transform spectrometers with significant self-emission and beamsplitter absorption

John Brasunas, Andrei Mamoutkine, and Nicolas Gorius

Doc ID: 234654 Received 02 Mar 2015; Accepted 18 May 2015; Posted 18 May 2015  View: PDF

Abstract: For accurate calibration of Fourier transform spectrometers we must constrain or re-sample the interferogram data to an invariant sampling comb. This can become challenging when instrument self-emission is significant and beam splitter absorption is present. The originallysampled interferogram center-burst position can move due not only to sampling comb changes, but also to an interaction between the strength of an external target and the so-called anomalous phase (the two ports of the interferometer contribute center-bursts at different locations, and the relative weighting of the two ports varies with the strength of the external target). We present a model of the anomalous phase to enable partitioning of changes in observed center-burst location between sampling comb changes and anomalous phase effects.

Optimization of Reconstructed Quality of Hard X-ray Phase Micro-Tomography

Qiang Liu, Xizeng Wu, and tiqiao xiao

Doc ID: 235317 Received 26 Feb 2015; Accepted 18 May 2015; Posted 18 May 2015  View: PDF

Abstract: For the better practicability of hard X-ray Propagation-based Phase-contrast Computed micro-Tomography (PPCT) in high resolution biological research, the high spatial resolution and contrast-to-noise ratio are simultaneously required for tiny structural discrimination and characterization. Most existing techniques to improve image quality are limited by high cost, physical limitations, and complexity of the experimental hardware and setup. A novel PPCT technique, combining the modulation transform function compensation (MTFC) algorithm based on wavelet transform and the generalized phase retrieval (PR) algorithm based on the transport of intensity equation, is proposed to optimize the reconstruction quality of tomographic slices. Our experimental results demonstrated the validity of the PPCT techniques and show that it is superior to the direct PPCT technique and the linearized PR PPCT technique by comparing their spatial resolutions and contrast-to-noise ratios simultaneously. This novel PPCT technique demonstrates great potential for biological imaging, especially for applications that require high spatial resolution and limit radiation exposure.

Assessing the reliability of diffuse correlation spectroscopy models on noise free analytical Monte Carlo data

Tiziano Binzoni and Fabrizio Martelli

Doc ID: 236202 Received 13 Mar 2015; Accepted 18 May 2015; Posted 19 May 2015  View: PDF

Abstract: It is shown that an analytical noise free implementation of Monte Carlo (Appl. Opt. 2015, in press) for diffuse correlation spectroscopy (DCS) may be successfully used to check the ability of a given DCS model to generate a reliable estimator of tissue blood flow. As an example, four different DCS models often found in the scientific literature are tested on a simulated tissue (semi-infinite geometry) with a Maxwell-Boltzmann probability distribution function for red blood cell peed. It is shown that the random model is the best model for the chosen speed distribution but that: 1) some inaccuracies in the DCS model in taking into account red blood cell concentration, and; 2) some inaccuracies probably due to too a low order approximation of the DCS model, are still observed. The method can be easily generalized for other speed/flow probability distribution functions of the red blood cells.

Direct deflection radius measurement of flexible PET substrates by using an optical interferometry

Jiong-shiun Hsu and PO-WEI LI

Doc ID: 237157 Received 30 Mar 2015; Accepted 17 May 2015; Posted 18 May 2015  View: PDF

Abstract: The deflection radius is essential in determining residual stress estimations in flexible electronics. However, the literature provides only indirect methods for obtaining a deflection radius. In this study, we present a measurement methodology for directly measuring the deflection radius of a polyethylene terephthalate (PET) substrate (a popular substrate of flexible electronics) by using an optical interferometer. A Twyman–Green optical interferometer was established and phase-shifting technology was used to increase the measurement resolution. Five PET substrates with known deflection radii were prepared to verify the measurement precision of the proposed measurement methodology. The results revealed that the error variance of our proposed measurement methodology is smaller than 3.5%.

Laser of Double-pulse Based on Semiconductor Optical Amplifier

HongGang Pan, Ailing Zhang, Yuming Xue, and Yanmei Shi

Doc ID: 234592 Received 24 Mar 2015; Accepted 16 May 2015; Posted 18 May 2015  View: PDF

Abstract: In this paper, a double-pulse laser with a semiconductor optical amplifier was proposed. By adjusting the polarization controller, we observed double-pulses with repetition frequencies 10.05 and 12.70 MHz, pulse widths from 33.40 and 30.13 ns. The laser consists of a SOA asymmetrically placed in a short fiber loop. Its switching time is determined by the off-center position of the SOA within the loop. In the loop, the two pulses which have the same widths transmit in the clockwise direction and counterclockwise direction separately.

Analysis of Optical Fiber Based LP01 ↔ LP02 Mode Converters for the O- S- and C-Band

Xiupu Zhang, Hakim Mellah, and Dongya Shen

Doc ID: 236108 Received 12 Mar 2015; Accepted 16 May 2015; Posted 18 May 2015  View: PDF

Abstract: In this paper, we propose a double fiber taper based mode converter that converts LP01 to LP02 and vice versa. The first taper is used to convert LP01 to some higher order LP0m (m>1) modes while the second taper suppresses the non-desired higher order modes (m>2) and results in LP02 overwhelmingly dominated. Simulation shows that conversion efficiency of almost 100% at the central wavelength of O- S- and C-band, and above 98% over the S- and C-band is achieved. Moreover, suppression of non-desired higher order modes is more than 10 dB over the whole O-, S- and C-band. In particular, the suppression is more than 19 dB for the whole C-band. The analysis also shows that the performance of the mode converter is not sensitive to slight variations of the converter’s parameters. In addition, the same converter can be used for converting LP02 back to LP01. It is shown that conversion efficiency higher than 99% and suppression of non-desired higher order modes higher than 30 dB can be obtained. Further, a (de)multiplexer for an LP02 and an LP01 mode is designed using the mode converter combined with a symmetric directional coupler. The multiplexer is broadband and has insertion loss less than 0.5 dB in the C-band.

Quantitative analysis and temperature induced variations of moiré pattern in fiber-coupled imaging sensors

Salman Karbasi, Ashkan Arianpour, Nojan Motamedi, William Mellette, and Joseph Ford

Doc ID: 237584 Received 06 Apr 2015; Accepted 15 May 2015; Posted 15 May 2015  View: PDF

Abstract: Imaging fiber bundles can map the curved image surface formed by some high-performance lenses onto flat focal plane detectors. Relative alignment between the focal plane array pixels and the quasiperiodic fiber bundle cores can impose an undesirable space variant moiré pattern, but this effect may be greatly reduced by flat-field calibration, provided the local responsivity is known. Here we demonstrate a stable metric for spatial analysis of the moiré pattern strength, and use it to quantify the effect of relative sensor and fiber bundle pitch, and that of the Bayer color filter. We measure the thermal dependence of the moiré pattern, and the achievable improvement by flat field calibration at different operating temperatures. We show that a flat-field calibration image at a desired operating temperature can be generated using linear interpolation between white images at several fixed temperatures, comparing the final image quality with an experimentally acquired image at the same temperature.

Photosensitivity of Gallium Doped Silica Core Fiber to 193nm ArF Excimer Laser

Kok-Sing Lim, Dinusha Gunawardena, Khairul Anuar Sharif, Nizam tm, Man-Hong Lai, Nasr Omar, siamak dawazdah emami, Shahrin Muhammad Yasin, Zulfadzli Yusoff, Hairul Abdul-Rashid, Harith Ahmad, and mohd zulkifli

Doc ID: 237691 Received 09 Apr 2015; Accepted 15 May 2015; Posted 18 May 2015  View: PDF

Abstract: Grating inscription in Ga doped silica core fiber (~5wt% Ga) has been demonstrated using ArF (193nm) and KrF (248nm) excimer lasers. In the comparative study with germanosilicate fiber with similar Ge concentration, Ga-doped silica core fiber shows greater photosensitivity to ArF excimer laser due to the higher absorbance in the region of 190 – 195 nm. In addition, the photosensitivity of Ga-doped silica core fiber has been greatly enhanced with hydrogenation. Ga-doped fibers are potential photosensitive fibers for FBGs production with ArF excimer laser.

False alarm suppression of multi-pulsed laser ranging system with Geiger-mode detector

Hanjun Luo, Huigang Xu, Zhengbiao Ouyang, Yadan Fu, and Benlian Xu

Doc ID: 236914 Received 25 Mar 2015; Accepted 15 May 2015; Posted 20 May 2015  View: PDF

Abstract: The false alarm probability is of great concern for designing and evaluating the performance of multi-pulsed laser ranging system with Geiger-mode avalanche photodiode (GM-APD). Based on the different statistical properties of the noise and echo photons with Poisson distribution and the multi-pulsed detection time chart, a false alarm suppression algorithm is presented, and the theoretical model of two cases and total false alarm probability with the system working at long dead time is established. By using the system design parameters, the multi-pulsed target detection probability with different echo intensity and detection number is analyzed, and the influence of four main factors, namely detection number, echo intensity, noise and echo position on the system false alarm probability is investigated. The results show that the false alarm probability can be suppressed by multi-pulsed detection and corresponding data processing method, to obtain an appropriate false alarm probability, it is suitable that the detection number is selected as 5, and the stronger echo intensity, lower noise level, more front echo position also can result in a lower false alarm probability.

Enhancing the absorption capabilities of thin film solar cells using sandwiched light trapping structures

Khaled Kirah, Sameh Abdellatif, Rami Ghannam, Ahmed Khalil, and Wagdy Anis

Doc ID: 235535 Received 04 Mar 2015; Accepted 15 May 2015; Posted 18 May 2015  View: PDF

Abstract: A novel structure for thin film solar cells is simulated with the purpose of maximizing the absorption of light in the active layer and of reducing the parasitic absorption in other layers. The proposed structure is formed of a thin film a-Si active layer sandwiched between two different structures for light trapping. The simulation was done using a new reliable, efficient and generic optoelectronic approach. The absorption profile, the external quantum efficient and the power conversion efficiency of the suggested solar cell are calculated. A noticeable enhancement is found in all the characteristics of the novel structure with an estimated 32% increase in the total conversion efficiency over a cell without any light trapping mechanisms.

Development of stable, narrow spectral line-width, fiber delivered laser source for spin exchange optical pumping

Bo Liu, Xin Tong, Lee Robertson, Chenyang Jiang, and Daniel Brown

Doc ID: 236009 Received 11 Mar 2015; Accepted 15 May 2015; Posted 18 May 2015  View: PDF

Abstract: We developed a stable, narrow spectral line-width, fiber delivered laser source for spin exchange optical pumping (SEOP). An optimized external cavity equipped with an off-the-shelf volume holographic grating (VHG) narrowed the spectral line-width of a 100 watt high power diode laser and stabilized the laser spectrum. The laser spectrum showed a high side mode suppression ratio (SMSR) of >30 dB and good long term stability (center wavelength drifting within ±0.01 nm during 220 hours operation). Our laser is delivered by a multi-mode fiber with power ~70 Watts, center wavelength 794.77 nm, and spectral bandwidth of ~0.13 nm.

Phase-shift feedback cavity ring-down spectroscopy

David Hovde and Anthony Gomez

Doc ID: 233908 Received 04 Feb 2015; Accepted 14 May 2015; Posted 14 May 2015  View: PDF

Abstract: Phase-shift cavity-enhanced techniques have been used to measure optical losses with relatively simple electronics. Instead of measuring the phase shift, in this work the intensity modulation frequency is varied using feedback to keep the phase shift locked to a target value. The modulation frequency then becomes a signal from which cavity losses can be estimated. The technique is applied with a super luminescent diode to measure losses resulting from the addition of acetylene to a cavity containing nitrogen at ambient temperature and pressure. The technique, phase-shift feedback cavity ring down, is compared to phase-shift cavity ring-down spectroscopy.

Intensity evaluation using a femtosecond pulse laser for absolute distance measurement

Hanzhong Wu, FuMin Zhang, XingHua Qu, Xiangsong Meng, Shiying Cao, and Jianshuang Li

Doc ID: 231650 Received 30 Dec 2014; Accepted 14 May 2015; Posted 14 May 2015  View: PDF

Abstract: In this paper, we propose a method of intensity evaluation based on different pulse models using a femtosecond pulse laser, which enables long range absolute distance measurement with nanometer precision and large non-ambiguity range. The pulse cross-correlation is analyzed based on different pulse models, including Gaussian, Sech², and Lorenz. The dc intensity and the amplitude of the cross-correlation patterns are also demonstrated theoretically. In the experiments, we develop a new combined system and perform the distance measurements on the granite rail system underground. The dc intensity and the amplitude of the interference fringes are measured, showing a good agreement with the theory, and the distance to be determined can be up to 25 m using intensity evaluation, within 64 nm deviation compared with a He-Ne incremental interferometer, corresponding to a relative precision of 2.7×10¯⁹.

Ultra-large magneto-optic rotations and rotary dispersion in terbium gallium garnet single crystal

Muhammad Anwar, Hassaan Majeed, and Amrozia Shaheen

Doc ID: 231681 Received 31 Mar 2015; Accepted 14 May 2015; Posted 14 May 2015  View: PDF

Abstract: We report systematically acquired data on the Verdet constant of terbium gallium garnet (TGG) for wavelengths ranging from visible to near-infrared (405 nm-830 nm) regime. Our experimental method of Stokes polarimetry is based on the Fourier decomposition of the received light intensity and allows unambiguous determination of both the Faraday rotation and the ellipticity of the emergent light. Temperature-dependent investigations in the range of 8 to 300 K extend earlier reports and verify the Verdet’s constant direct dependence on the magnetization, whose first order approximation is simply a manifestation of the Curie’s law. Further, a least-squares fitting of the experimental data correlates well with theoretical predictions. At a wavelength of 405 nm and temperature of 8 K, the rotation is approximately 500◦.

LD pumped actively Q-switched and mode-locked Nd:YAG/PbWO4 Raman laser

Ze Ding, Shuanghong Ding, Haixu Jia, Jiajia Liu, Lili Yang, Junqiang Huangfu, and ShiWu Wang

Doc ID: 232781 Received 23 Jan 2015; Accepted 13 May 2015; Posted 14 May 2015  View: PDF

Abstract: Compact laser diode pumped actively Q-switched and mode-locked Nd:YAG/PbWO4 Raman laser is demonstrated. With the incident pump power of 9.11 W and pulse repetition frequency of 15 kHz, the maximum average output power of 1.003 W at 1178 nm is obtained and the corresponding conversion efficiency is 11%. A perfect stable mode-locking operation with the modulation depth of 100% is obtained and the corresponding mode-locking pulse width is less than 207 ps. The actively Q-switched and mode-locked Raman laser is theoretically analyzed and calculated using the fluctuation rate equation model.

Design of a BEF-adaptive freeform lens to enhance overall performance in direct-lit LED backlighting

Xiaobing Luo, Qi Chen, Hu Run, Dan Wu, Bin Xie, Xingjian Yu, and Kai Wang

Doc ID: 235583 Received 05 Mar 2015; Accepted 13 May 2015; Posted 14 May 2015  View: PDF

Abstract: In this study, a brightness enhancement film (BEF)-adaptive method was proposed to design freeform lenses for enhancing brightness performance in the direct-lit light-emitting diode (LED) backlight system. Detailed design algorithm was presented based on the analysis of the output optical properties of BEF. By introducing a constriction factor, we could control the light intensity distribution curve (LIDC) at will to adapt to the characteristics of BEF and make more light transmit through the BEF. Compared with LED backlight system without the freeform lens, the one with the BEF-adaptive lens could improve the axial luminance by 20.67% and output efficiency by 6.02%.

High power, micro-integrated diode laser modules at 767 nm and 780 nm for portable quantum gas experiments

Max Schiemangk, Kai Lampmann, Aline Dinkelaker, Anja Kohfeldt, Markus Krutzik, Christian Kürbis, Alexander Sahm, Stefan Spieβberger, Andreas Wicht, Goetz Erbert, Guenther Traenkle, and Achim Peters

Doc ID: 236192 Received 13 Mar 2015; Accepted 13 May 2015; Posted 14 May 2015  View: PDF

Abstract: We present micro-integrated diode laser modules operating at wavelengths of 767 nm and 780 nm for cold quantum gas experiments on potassium and rubidium. The master-oscillator-power-amplifier concept provides both narrow linewidth emission and high optical output power. With a linewidth (10 μs) below 1 MHz and an output power of up to 3 W, these modules are specifically suited for quantum optics experiments and feature the robustness required for operation at a drop tower or on-board a sounding rocket. This technology development hence paves the way towards precision quantum optics experiments in space.

Model-based recognition of 3D articulated target using laser radar range data

Jian-Feng Sun, lv dan, Qi Li, and Qi Wang

Doc ID: 234649 Received 17 Feb 2015; Accepted 13 May 2015; Posted 13 May 2015  View: PDF

Abstract: Laser radar (ladar) is suitable for 3D target recognition because ladar range images can provide rich 3D geometric surface information of targets. In this paper, we proposed a part-based 3D model matching technique to recognize articulated ground military vehicles in ladar range images. The key of this approach is to solve the decomposition and pose estimation of articulated parts of targets. The articulated components were decomposed into isolate parts based on 3D geometric properties of targets, such as surface point normals, data histogram distribution, and data distance relationship. The corresponding poses of these separate parts were estimated through the linear characteristic of barrels. According to these pose parameters, all parts of the target were roughly aligned to 3D point cloud models in library and fine matching was finally performed to accomplish the 3D articulated target recognition (3ATR). The recognition performance was evaluated with 1728 ladar range images of 8 different articulated military vehicles with various part types and orientations. Experimental results demonstrated that the proposed approach achieved a high recognition rate.

Capability of shifted excitation Raman difference spectroscopy under ambient daylight

Martin Maiwald, André Mueller, Bernd Sumpf, Goetz Erbert, and Guenther Traenkle

Doc ID: 234908 Received 17 Feb 2015; Accepted 13 May 2015; Posted 13 May 2015  View: PDF

Abstract: We present shifted excitation Raman difference spectroscopy (SERDS) under ambient daylight using a dual-wavelength diode laser at 785 nm. The monolithic diode laser provides more than 110 mW in cw-operation. Both excitation lines show an emission width ≤ 0.2 cm 1 and a spectral distance of 10 cm-1 as targeted for SERDS. Polystyrene is used as test sample and ambient daylight to generate real-world background interference. Here, a broadband background signal with narrowband absorption lines from water vapor and Fraunhofer lines from singly-ionized calcium (Ca II) obscure the Raman lines of polystyrene. SERDS clearly separates the Raman signals from the background signals with a 13-fold improvement in signal-to-background noise.

Surface shape evaluation with a corneal topographer based on a conical null-screen with a novel radial point distribution

Manuel Campos-Garcia, Cesar Cossio Guerrero, Victor Moreno-Oliva, and Oliver Huerta-Carranza

Doc ID: 235538 Received 03 Mar 2015; Accepted 12 May 2015; Posted 13 May 2015  View: PDF

Abstract: In order to measure the shape of fast convex aspherics, such as the corneal surface of the human eye, we propose the design of a conical null-screen with a radial point distribution (spots similar to ellipses) drawn on it in such a way that its image, which is formed by reflection on the test surface, becomes an exact array of circular spots if the surface is perfect. Any departure from this geometry is indicative of defects on the evaluated surface. We present the target array design and the surface evaluation algorithm. The precision of the test is increased by performing an iterative process to calculate the surface normals, reducing the numerical errors during the integration. We show the applicability of the null-screen based topographer by testing a spherical calibration surface of 7.8 mm radius of curvature and 11 mm in diameter. Here we obtain an rms difference in sagitta between the evaluated surface and the best fitting sphere of 2 μm.

Numerical model of tapered fiber Bragg gratings for comprehensive analysis and optimization of their sensing and strain-induced tunable dispersion properties

Tomasz Osuch, Kazimierz Jędrzejewski, and Konrad Markowski

Doc ID: 236352 Received 17 Mar 2015; Accepted 12 May 2015; Posted 13 May 2015  View: PDF

Abstract: A versatile numerical model for spectral transmission/reflection and group delay characteristics analysis and design of tapered fiber Bragg gratings (TFBGs) is presented. This approach ensures the flexibility with defining both distribution of refractive index change of the gratings (including apodization) as well as shape of the taper profile. Additionally, sensing and tunable dispersion properties of TFBG were fully examined, considering strain-induced effects. Presented numerical approach together with Pareto optimization were also used to design the best tanh apodization profiles of TFBG in terms of maximization its spectral width with simultaneous minimization of the group delay oscillations. Experimental verification of the model confirms its correctness. Combination of model versatility and possibility to define the other objective functions of Pareto optimization, creates universal tool for TFBG analysis and design.

Concept and Modeling Analysis of a High Fidelity Multi-mode Deformable Mirror

Chao Zhou, Tingwen Xing, Yun Li, and Anding Wang

Doc ID: 236788 Received 24 Mar 2015; Accepted 12 May 2015; Posted 13 May 2015  View: PDF

Abstract: Conventional deformable mirrors (DM) cannot meet the requirement of aberration controlling for an advanced lithography tools. This paper illustrates an approach using the property that deformation of a thin plate is similar to optical modes to realize a high fidelity multi-mode deformable mirror whose deformation has a character of optical aberration modes. The way to arranging actuators is also examined. In this paper, a 36-actuator deformable mirror is taken as an example to generate low order Zernike modes. The result shows that, this DM generate the 4th Fringe Zernike mode (Z4) defocus, and primary aberration Z5~Z8 with an error less than 0.5%, generates the fifth order aberration Z10~Z14 and generates the seventh order aberration Z17~Z20 with an error less than 1.1%. The high fidelity replication of Zernike mode indicates the DM satisfies a demand of controlling aberrations corresponding to the first 20 Zernike modes in an advance lithography tool.© 2015 Optical Society of America

Inherent Optical Properties of Jerlov Water Types

Michael Solonenko and Curtis Mobley

Doc ID: 236972 Received 26 Mar 2015; Accepted 12 May 2015; Posted 13 May 2015  View: PDF

Abstract: The diffuse attenuation coefficient Kd(λ) was first expressed in terms of the inherent optical properties (IOPs) of water according to well-established empirical bio-optical models. Boltzmann simulated annealing was then used to find the best sets of IOPs to fit Kd(λ) spectra to the reference spectra Kd0(λ) that define the Jerlov water types. Absorption a(λ) and scattering b(λ) coefficients were thus obtained for all Jerlov water types over the wavelength range 300–700 nm. The chlorophyll concentrations corresponding to the Jerlov water types were also obtained via bio-optical models. The result is a self-consistent set of spectral IOPs, chlorophyll concentrations, and Jerlov water types useful for a variety of underwater optical communications and remote sensing applications.

Optimization of galvanometer scanning for Optical Coherence Tomography

Virgil-Florin Duma, Jannick Rolland, Patrice Tankam, Jinxin Huang, and Jungeun Won

Doc ID: 232259 Received 13 Jan 2015; Accepted 12 May 2015; Posted 12 May 2015  View: PDF

Abstract: We study experimentally the effective duty cycle of galvanometer-based scanners (GSs) with regard to the three main parameters of the scanning process: theoretical/imposed duty cycle (of the input signal), scan frequency, and scan amplitude. Sawtooth to triangular input signals for the device are considered. The effects of the mechanical inertia of the oscillatory element of the GS are analyzed, as well as their consequences for OCT imaging. The saturation of the device when the theoretical duty cycle and the scan amplitude are increased to the limit is demonstrated for a useful range for scan frequencies by direct measurement of the position of the galvomirror. Investigations of OCT imaging of large samples also validate this saturation, as well as the gaps/blurred portions obtained between neighboring images when using both triangular and sawtooth scanning at high scan frequencies. For this latter aspect, the necessary overlaps between neighboring B-scans, and therefore between the corresponding volumetric/3-D reconstructions of the sample, are evaluated and implemented with regard to the same parameters of the scanning process. OCT images that are free of these artifacts are thus obtained.

Improving Space Domain Awareness through Unequal-Cost Multiple Hypothesis Testing in the Space Surveillance Telescope

Tyler Hardy, Stephen Cain, Jae Jeon, and Travis Blake

Doc ID: 232530 Received 23 Jan 2015; Accepted 12 May 2015; Posted 12 May 2015  View: PDF

Abstract: This paper investigates algorithms to improve the detection of space objects with the Space Surveillance Telescope (SST) system. These space objects include both natural objects such as asteroids and artificial satellites in Earth orbit. Using a proposed Multiple Hypothesis Test (MHT), the detection performance is compared to the currently used algorithm, as well as an equal-cost MHT algorithm. To compare these algorithms a data set collected by the SST of a Geosynchronous Earth Orbit (GEO) satellite, ANIK-F1 entering the Earth's eclipse, is utilized. It is found that an unequal-cost MHT gives increased performance over both a point detector and equal-cost MHT over a large range of potential intensities. Results are presented as probability of detection and Receiver Operating Characteristic (ROC) curves. In addition, the performance of the algorithm as a function of number of hypotheses used is investigated.

An extreme ultraviolet spectrometer for the Shenguang III laser facility

Gang Xiong, Guohong Yang, Jiyan Zhang, Minxi Wei, Yang Zhao, Bo Qing, Min Lv, Zhenghua Yang, Feng Wang, Shenye Liu, Houzhi Cai, and Jinyuan Liu

Doc ID: 234756 Received 18 Feb 2015; Accepted 12 May 2015; Posted 12 May 2015  View: PDF

Abstract: An extreme ultraviolet spectrometer has been developed for high energy density physics experiments at the Shenguang-III (SG-III) laser facility. Alternative use of two different varied-line-spacing gratings covers a wavelength range of 10-260Å. A newly developed X-ray framing camera with single wide stripline is designed to record time-gated spectra with about 70ps temporal resolution and 20lp/mm spatial resolution. The width of the stripline is up to 20mm, enhancing the capability of the spatial resolving measurements. All components of the X-ray framing camera are roomed in a aluminum air box. The whole spectrometer is mounted on a diagnostic instrument manipulator (DIM) at the SG-III laser facility for the first time. A new alignment method for the spectrometer based on the superimposition of two laser focal spots is developed. The approaches of the alignment including offline and online two steps are described. A carbon spectrum and a aluminum spectrum have been successfully recorded by the spectrometer using 2400l/mm and 1200l/mm gratings, respectively. The experimental spectral lines show that the spectral resolution of the spectrometer is about 0.2 Å and 1Å for the 2400l/mm and 1200l/mm gratings, respectively. A theoretical calculation was carried out to estimate the maximum resolving power of the spectrometer.

Parity decomposition theory of full wavefront aberration measurement using the intensity differences of aerial images in micro-lithography

Satoshi Yashiki

Doc ID: 235297 Received 02 Mar 2015; Accepted 12 May 2015; Posted 12 May 2015  View: PDF

Abstract: The theory of full wavefront aberration measurements is developed using the intensity differences of aerial images, which are the projected images of one-dimensional measurement patterns consisting of single- or multi-bars. The key concept is the parity decomposition about the optical axis for two optical components: illumination pupil and wavefront aberration. An additional mathematical treatment, which is a perturbative approach with regard to aberration, is applied to the partially coherent imaging formula. The intensity difference of the two peaks has terms that are linear to the odd and even aberration with rigorously canceled squared aberration terms. The full wavefront aberration measurement is realized from simultaneous linear equations about the intensity difference. The validity of this approach is numerically confirmed under practical lithography conditions.

Dual-mode superresolution imaging with stimulated emission depletion microscopy and fluorescence emission difference microscopy

Cuifang Kuang, Yifan Wang, Ye Ma, Xu Liu, Yue Fang, Yingke Xu, and Zhihua Ding

Doc ID: 235098 Received 02 Mar 2015; Accepted 10 May 2015; Posted 11 May 2015  View: PDF

Abstract: A dual-mode superresolution imaging system with two different superresolution imaging methods, STED and FED, is presented. Electrical shutters controlled by the host computer are introduced to switch the two imaging modes. Principles of both methods are analyzed theoretically and enhancements in the lateral resolution and SNR are demonstrated theoretically and experimentally. Results show that both the two imaging methods offered by the proposed system can break the diffraction barrier. Furthermore, the presented system provides a meaningful way to image fluorescent samples by a corresponding imaging mode according to the specific characteristics of samples analyzed for study. For samples which can endure high-power illumination, it is appropriate to use the STED mode to achieve a better resolution, while for samples which are vulnerable to high intensity, the FED method is a better choice because no high-power beam is needed and the FED method can provide better resolution than STED when no high-power beam is allowed. The flexible switching of the two superresolution imaging modes can help researchers to make most of the advantages of each imaging method. It is believed that the presented system has the potential to be widely used in the future nanoscale investigations.

Neural network implementation for a reversal procedure for water and dry matter estimation on plant leaves using selected LED's wavelengths

Elian Conejo, jean frangi, and Gille Rosny

Doc ID: 234577 Received 13 Feb 2015; Accepted 09 May 2015; Posted 11 May 2015  View: PDF

Abstract: An inversion method based on neural network was used to estimate water and dry matter contents on plant leaves from transmittance and reflectance measurements using light emitting diodes (LEDs) at specific wavelengths in NIR and FIR (1050, 1450, 1550 and 1650 nm). These LED's were implemented into a portable radiometer Radiométre Portatif de Mesure In Situ (RAMIS II). The preliminary results showed a RMSE value of 0.0027 g/cm2 equivalent to 20 % error approximately on water estimation computed on 127 plant leaf samples over 51 species. Dry matter estimation was also performed showing potential implementation after future improvements. The inversion method permits to be implemented in a portable system based on any silicon platform with the capability to perform non destructive measurement in situ on plant tissue.

Effects of a measurement floor on Mueller matrix measurements in a dual rotating retarder polarimeter BSDF system

Michael Marciniak and Stephen Nauyoks

Doc ID: 233759 Received 04 Feb 2015; Accepted 08 May 2015; Posted 11 May 2015  View: PDF

Abstract: Since a measurement of the Bidirectional Scatter Distribution Function (BSDF) of a material is proportional to the intensity of the scattered light, a BSDF measurement system with the addition of a dual rotating retarder polarimeter can be used to calculate the Mueller matrix of a scatterer. One advantage of a BSDF system using a laser source is its large dynamic range, which allows the measurement of scattered light both near to and away from the specular region. As BSDF measurements move away from the specular region and into a more diffusescatter region, the measured signal decreases and may approach the system’s measurement floor. Therefore, BSDF and Mueller-matrix measurements are dependent, not only on the scatter from the sample, but also on the noise floor of the system. By analyzing numerically created BRDF data, we show that since the noise floor of a system is typically constant, the Mueller-matrix measurement at the noise floor appears to be that of a perfect depolarizer. Therefore, as the BSDF measurement space moves away from the high-signal region and the noise floor is approached, the Mueller matrix assigned to the sample artificially approaches that of a perfect depolarizer. The rate and location in scatter-angle space of this shift is dependent on the BSDF of the material and on the signal-tonoise ratio in the system. Therefore, caution must be taken when drawing conclusions about measured Mueller matrices for scattered light, particularly in measurement regions where the measured signal approaches the system floor.

Synthetic aperture microscopy based on referenceless phase retrieval with an electrically tunable lens

Dennis Lee, Andrew Weiner, Kyunghun Han, and Hyeon Jeong Lee

Doc ID: 237599 Received 06 Apr 2015; Accepted 08 May 2015; Posted 11 May 2015  View: PDF

Abstract: Phase imaging microscopy, based either on holography or non-holographic methods such as phase retrieval, has seen considerable recent attention. Phase retrieval offers the advantage of being free of a reference arm and enables a more stable and compact setup. We present an optical setup which provides enhanced resolution by implementing synthetic aperture imaging based on phase retrieval using an electrically tunable lens (ETL). The ETL is a more compact and less expensive alternative to computerized translation stages and spatial light modulators. Before applying phase retrieval, we discuss a general calibration algorithm which performs image registration, corrects for magnifications, and determines the axial locations of image planes. Finally we obtain resolution-enhanced images of a phase grating and of cells to demonstrate the practical application of our technique.

A 1550 nm modulating retro-reflector based on coated nanoparticles for free space optical communication

Etai Rosenkrantz and Shlomi Arnon

Doc ID: 239606 Received 22 Apr 2015; Accepted 08 May 2015; Posted 11 May 2015  View: PDF

Abstract: Nowadays, there is a renaissance in the field of space exploration. Current and future missions depend on astronauts and a swarm of robots for reconnaissance. In order to reduce the power consumption, weight and size of the robots, an asymmetric communication system may be used. This is achieved by installing modulating retroreflectors (MRRs) on one side of the link, while the other side is equipped with an interrogating laser. In this paper we theoretically study an innovative device that can serve as a MRR in the infrared range of the spectrum. The device is based on a ferroelectric PZT thin-film containing TiO2 coated Ag nanoparticles, which exhibit strong plasmonic resonance in the infrared range. After intensive analyses, which included calculations and simulations, we were able to design the device to operate at the 1550 nm wavelength. This is of great importance since the design of devices operating at 1550 nm as this wavelength is a mature technology widely used in free-space optics. Hence, this MRR can serve in asymmetric communication links relying on 1550 nm transmissions, which are also eye-safe. To the best knowledge of the authors, this is the first time coated metal nanoparticles have been proposed to modulate light in the infrared region. The performance of this device is unique reaching a 17.5 dB modulation contrast with only a ±2 V operating voltage. This modulator may also be used for terrestrial communication, such as fiber optics and optical interconnects in future data centers.

Development of a multidimensional fluorimeter and its application for authenticating objects marked with upconverting security markers

Anatoliy Borodin, Mikhail Gouzman, and Vladislav Kuzminskiy

Doc ID: 233706 Received 03 Feb 2015; Accepted 06 May 2015; Posted 12 May 2015  View: PDF

Abstract: We present a conceptual design of a multidimensional fluorimeter, where a set of individually controlled laser diodes used as excitation light sources enables the user to obtain 3D spectra, i.e. excitation-emission matrices (EEMs), in a single measurement, as well as acquire multidimensional spectra by scanning excitation and emission wavelengths, and the power density and frequency modulation of excitation light. The performance of our fluorimeter prototype is evaluated by authenticating protected objects marked with upconverting security markers. A method, based on the analysis of EEMs representing security markers, for authenticating objects is proposed, to avoid authentication errors and to improve the speed of information processing by introducing digitized EEMs, basis EEMs, and basis markers.

DIFFRACTION MODEL FOR THERMOREFLECTANCE DATA

SAHIDA KURESHI, Drazen Fabris, Shawn Tokairin, Chris Cardenas, and Cary Yang

Doc ID: 220919 Received 20 Aug 2014; Accepted 05 May 2015; Posted 06 May 2015  View: PDF

Abstract: Thermoreflectance imaging provides the capability to map temperature spatially on the submicron scale, by using a light source and CCD camera for data acquisition. The ability to achieve such spatial resolution and observe detailed features is influenced by optical diffraction. By combining diffraction from both the sample and substrate, a model is developed to determine the intensity of the thermoreflectance signal. This model takes into account the effective optical distance, sample width, wavelength, signal phase shift, and reflectance intensity, while showing qualitative and quantitative agreement with experimental thermoreflectance images from 1 μm and 10 μm wide gold lines at two wavelengths.

Coherent diffractive imaging microscope with a high-order harmonic source

Khuong Dinh, Hoang Le, Peter Hannaford, and Lap Dao

Doc ID: 226904 Received 17 Nov 2014; Accepted 05 May 2015; Posted 06 May 2015  View: PDF

Abstract: We perform extreme ultraviolet coherent diffractive imaging (CDI) by using a focussed narrow-bandwidth high harmonic generation (HHG) source with wavelength around 30 nm as an illumination beam. We achieve a resolution of ~ 210 nm with an exposure time of 30 s for a 13 μm x 13 μm sample which is constructed from an absorption function and a resolution of ~ 45 nm with an exposure time of only 5 s for a 3 μm x 3 μm sample which is constructed from a transmission function. In particular, we report successful reconstruction of a complex sample absorption function using a table-top high harmonic source and this will open the path to the realization of a compact soft x-ray microscope to investigate biological samples such as membrane proteins.

Fast and accurate focusing analysis of large photon sieve using pinhole ring diffraction model

Tao Liu, Xin Zhang, Jizhen Zhang, Yanxiong Wu, Hemeng Qu, and Lingjie Wang

Doc ID: 233834 Received 05 Feb 2015; Accepted 04 May 2015; Posted 04 May 2015  View: PDF

Abstract: In this paper, we developed a pinhole ring diffraction model for the focusing analysis of large photon sieve. Instead of analyzing individual pinholes, the focusing of all of the pinholes in a single ring zone is discussed. Explicit equation for the diffracted field of individual pinhole ring has been proposed. The validity range of this generalized model is investigated and the sufficient conditions for the validity of this pinhole ring diffraction model are analytically described. A practical example has been given and investigation reveals the high accuracy of the pinhole ring diffraction model. This simulation method could be used for the fast and accurate focusing analysis of large photon sieve.

Determination of carcinogenic Fluorine in cigarettes using pulsed UV laser induced breakdown spectroscopy

Mohammed Gondal, Yusuf Habibullah, Luqman Oloore, and Mohammed Iqbal

Doc ID: 236499 Received 18 Mar 2015; Accepted 30 Apr 2015; Posted 01 May 2015  View: PDF

Abstract: A spectrometer based on pulsed UV Laser induced breakdown spectroscopy (LIBS) and high sensitive ICCD camera was developed to determine the carcinogenic substances like fluorine in various brands of cigarettes available commercially. In order to achieve the high sensitivity required for the determination of trace amounts of fluoride in cigarettes and eventually the best limit of detection, the experimental parameters (influence of incident laser energy on libs signal intensity and time response of plasma emission) were optimized. In addition, the plasma parameters like electron temperature and electron density were evaluated using Boltzman’s plot for cigarettes tobacco for the first time. To the best of our knowledge, LIBS has never been applied to determine the fluorine concentration in cigarettes. Along with the detection of flourine, other trace metals like Ba, Ca, Ni, Cu and Na were also detected in cigarettes. For determination of the concentration of flourine, calibration curve was drawn by preparing standard samples in various fluoride concentrations in tobacco matrix. The concentration of fluorine in different cigarettes tobacco samples was 234,317,341 and 360 ppm respectively, which is considered to be much higher than the safe permissible limits. The limit of detection of our LIBS spectrometer was 14 ppm for fluorine.

Theory and algorithms of an efficient fringe analysis technology for automatic measurement applications

Rigoberto Juarez-Salazar, Wuiyevaldo Guerrero-Sanchez, and Carlos Robledo-Sanchez

Doc ID: 235747 Received 06 Mar 2015; Accepted 29 Apr 2015; Posted 11 May 2015  View: PDF

Abstract: Some advances in fringe analysis technology for phase computing are presented. A full scheme to phase evaluation, able to automatic applications, is proposed. The proposal consist of: a fringe-pattern normalization method, the Fourier fringe-normalized analysis, a generalized phase-shifting processing for inhomogeneous nonlinear phase shifts and spatio-temporal visibility, and a phase-unwrapping method by a rounding-least-squares approach. The theoretical principles and the computer programs written in the free software GNU Octave are given. Numeral examples and an experimental evaluation are presented.

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