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Numerical and experimental validation of asingle-camera 3D velocimetry based on endoscopictomography

Jianan Zhao, Hecong Liu, and Weiwei Cai

Doc ID: 342901 Received 24 Sep 2018; Accepted 15 Jan 2019; Posted 15 Jan 2019  View: PDF

Abstract: Tomographic velocimetry as a 3D technique has attracted substantial research interests in recent yearsdue to the pressing need for the investigations of complex turbulent flows which are inherentlyinhomogeneous. However, tomographic velocimetry usually suffers from high experimental costsespecially due to the formidable expenses of multiple high-speed cameras and the excitation lasersource. To overcome this limitation, a cost-effective technique called endoscopic tomographicvelocimetry has been developed in this work. As a single-camera system, nine projections of the target3D luminous field at consecutive time instants can be registered from different orientations with onecamera and customized fiber bundles, while this is only possible with the same number of cameras in aclassical tomographic velocimetry system. Extensive numerical simulations were conducted with threeinversion algorithms and two velocity calculation methods. According to the RMS error analysis, it wasfound that the algebraic reconstruction technique outperformed the other two inversion algorithms, andthe 3D optical flow method exhibited a better performance than cross correlation in terms of bothaccuracy and noise immunity. Proof-of-concept experiments were also performed to validate ourdeveloped system. The results suggested that an average reconstruction error of the artificiallygenerated 3D velocity field was less than 6%, indicating a good performance of the velocimetry system.Although this technique was demonstrated by reconstructing continuous luminous fields, it can beeasily extended to discrete ones which are typically adopted in particle image velocimetry. Thistechnique is promising not only for flow diagnostics but other research areas such as biomedicalimaging.

Wollaston prism-based structured illumination microscope with tunable-frequency

Ana Doblas, Sebastian Bedoya, and Chrysanthe Preza

Doc ID: 348308 Received 16 Oct 2018; Accepted 15 Jan 2019; Posted 15 Jan 2019  View: PDF

Abstract: This work proposes an alternative structured illumination (SI) system based on a Wollaston prism (WP) illuminated by the diffracted field of an incoherent linear source. The proposed WP-based SI system presents several advantages. First, the generated fringes can be approximated by a pure sinusoidal pattern, thereby computational methods developed for sinusoidal SI can be used without the need of additional processing. Second, the SI pattern’s period can be continuously varied up to the cutoff frequency of the native widefield system. Most significantly, the phase shifting of the SI pattern required for demodulation in SI microscopy can be easily accomplished using a de Sénarmont compensator, which provides accurate lateral displacement of the fringes independently of the lateral modulation frequency. Experimental verifications confirm the presented theoretical predictions.

Highly coherent supercontinuum generation in apolarization-maintaining CS2-core photonic crystalfiber

feng xu, Jinhui Yuan, Chao Mei, Binbin Yan, Xian Zhou, Qiang Wu, Kuiru Wang, Xinzhu Sang, Chongxiu Yu, and Gerald Farrell

Doc ID: 354676 Received 05 Dec 2018; Accepted 15 Jan 2019; Posted 15 Jan 2019  View: PDF

Abstract: In this paper, we design a polarization-maintaining CS2-core photonic crystal fiber (PM-CCPCF). The two air holes atx-direction are infiltrated with C2H5OH in order to introduce the birefringence. By optimizing the structureparameters of the PM-CCPCF, it is demonstrated that the x-polarization fundamental mode has all-normaldispersion profile and the corresponding y-polarization fundamental mode has anomalous dispersion profile forpump wavelength 1.76 μm. Then, we investigate the supercontinuum (SC) generations when different fiber lengths,pump peak powers, and pump pulse widths are chosen, respectively. Simulation results show that for the xpolarizationand y-polarization fundamental modes, highly coherent SCs can be generated by appropriatelychoosing the fiber length and pump pulse parameters. Finally, nonlinear propagation dynamics are analysed whenthe optimized fiber length and pump pulse parameters are used. The bandwidth of the SCs generated for xpolarizationand y-polarization fundamental mode can be up to 0.82 and 1.26 octave, respectively.

Correction of errors due to uneven intensitydistribution and inaccurate phase shifts in aprism-base simultaneous phase-shiftinginterferometry

ting guo, Liu jun, Yang Jun, Lei Li, and Wenlong Lu

Doc ID: 349323 Received 25 Oct 2018; Accepted 15 Jan 2019; Posted 16 Jan 2019  View: PDF

Abstract: Simultaneous phase-shifting interferometry (SPSI) is a suitable technique fordynamic surface measurement due to its rapid measurement capability. Based on whetherthere are obvious multiple phase-shifting channels in the setup, it can be divided into themulti-channel type and the pixelated phase-mask type. For the former type, two importanterror sources are the uneven intensity distribution among different phase-shifting channels andinaccurate phase shifts in each phase-shifting channel. In order to diminish the influence ofthese two error sources, several methods have been proposed. However, in some of thesemethods, only one error source of the two was considered and corrected. In the methods wherethe two error sources were both considered, some assumptions such as the uniformbackground intensity and fringe contrast are needed. So a complete and universal suppressionmethod for both error sources is still needed in actual applications. In this paper, for aprism-based SPSI, we proposed such an error correction method which mainly contains thefollowing contributions. First, the intrinsic parameters of the system, including intensitydistribution coefficients and relative phase shifts among phase-shifting channels, arecalibrated in advance. We also checked the uniformity of phase shifts in each phase-shiftingchannel. Second, based on the obtained parameters, a corrected four-step phase-shiftingalgorithm is deduced to recover the more accurate measured phase. Both results of simulationand experiment verify the effectiveness of the proposed method.

Complex refractive index of Polycarbonate over theUV-Vis-IR region from 0.2 to 3 μm

Damien Brissinger

Doc ID: 352961 Received 27 Nov 2018; Accepted 15 Jan 2019; Posted 16 Jan 2019  View: PDF

Abstract: The complex refractive index dispersion of polycarbonate was identified from reflectance and transmittancemeasurements across the spectral range 0.2 - 3 μm. Two identification methods were investigated. A numericalidentification method that allows rigorous consideration of different experimental configurations is described. Theresults obtained are compared with values calculated with an analytical method assuming normal incidence.

Design and analysis for annular focus antenna withoff-axial parabolic and slanting hyperbolic rotatingsurfaces configuration

Biao Cao, Ping Jiang, JUNYI WANG, Shengqian Mao, Wei Caiyang, Yan Qin, and Yang Huajun

Doc ID: 348890 Received 30 Oct 2018; Accepted 14 Jan 2019; Posted 15 Jan 2019  View: PDF

Abstract: We propose a novel annular focus antenna with off-axial parabolic primary mirror and slanting hyperbolicsecondary mirror. Ray tracing based on three-dimensional vector reflection theory is utilized to design and analyzethe structural parameters of the antenna. In ideal conditions, there is no geometric loss in theory and thetransmitting efficiency increases by 24.54% compared with conventional Cassegrain optical antenna. Thetransmitting efficiency is also calculated in the conditions of off-axial and on-axial defocus. The simulated resultsdemonstrate that this design can increase transmission efficiency of the optical antenna effectively.

Eigen frequency measurements of a fiber opticgyroscope based on a staircase waveform with largetemperature range

Xunmin Zhu, Xingfan Chen, xiaowu shu, and Cheng Liu

Doc ID: 353096 Received 29 Nov 2018; Accepted 14 Jan 2019; Posted 15 Jan 2019  View: PDF

Abstract: The eigen frequency is a key parameter of a fiber optic gyroscope (FOG). We present an on-line eigen frequency tracking method for FOG technology based on the staircase waveform and a four-step frequency perturbation. Results show that the measurement accuracy of the eigen frequency does not exceed 1.7Hz for temperature range27. 5 − 62. 5°C and variation rate 0. 24 °C ⁄min. This is in good agreement with the theoretical model. The method, which exhibits a low time-space complexity, simply requires the addition of a low-rate digital-to-analog converter (DA) to the existing gyro system. There is no requirement for the type of staircase waveform in the phase on, and the staircase waveform remains unchanged. Thus, this method can be easily transplanted intoother algorithms.

All-Fiber Ring-Cavity for Frequency Stability Transferat 1.55 μm

PIERRE GRUNING, AMINE CHAOUCHE RAMDANE, karim manamani, Thinhinane Aoudjit, Vincent Roncin, and frédéric Du Burck

Doc ID: 343105 Received 31 Aug 2018; Accepted 14 Jan 2019; Posted 15 Jan 2019  View: PDF

Abstract: A compact set-up for transferring the stability of ametrological frequency reference at 1.55 μm isdescribed. One mode of a fiber-ring cavity is frequencylocked onto the reference. The stability transfer isachieved by locking an extended cavity diode-laser,tunable over 100 nm onto one cavity mode. Once locked,this tunable laser exhibits a relative frequency stabilityclose to 10-12 for integration times from 1 s to 3000 s(minimum of 6 10-13 at 10 s). We show that this stabilitylimitation is due to polarization fluctuations sensitivity offiber optic components. Using a second cavity, thefrequency stability transfer over 58 nm is demonstratedat a level of 4 10-12. Associated to a local frequencyreference and with an efficient acoustic and thermalinsulation, this compact set-up is intended for embeddedmetrological applications.

Effects of the shape distribution of aerosolparticles on their volumetric scatteringproperties and the radiative transfer throughthe atmosphere including polarization

Li Li, Zhengqiang Li, Oleg DUBOVIK, XU ZHENG, ZHANHUA LI, Jinji Ma, and Manfred Wendisch

Doc ID: 344951 Received 02 Oct 2018; Accepted 13 Jan 2019; Posted 14 Jan 2019  View: PDF

Abstract: The effects of shape distribution of aerosol particles on the volumetric scatteringproperties as well as the radiance and polarization distributions of skylight are investigated bynumerical simulations. The results demonstrate that indeed the shape distribution exerts asignificant influence on the skylight degree of linear polarization. The skylight polarizationcalculated assuming microscope-measured shape distributions is distinct from that usinginversion-based shape distribution. The significant effects will influence the retrieval ofsphericity of aerosols based on the sun-sky radiometer measurements. Our results suggest thatusing representative shape distributions obtained by direct microscopic observations ofaerosol samples captured in the natural atmosphere has high potential to improve the retrievalof aerosol shape parameter.

Aerosol Microphysical Parameters Vertical Profiles Measured by a Dual-Raman Lidar During 2007-2013 at Hefei, China

Hu Shunxing, chidong xu, Ji Yufeng, and Huanling Hu

Doc ID: 345015 Received 05 Sep 2018; Accepted 13 Jan 2019; Posted 14 Jan 2019  View: PDF

Abstract: L625 4-wavelength Dual Raman-Mie lidar was used to detect the elastically Mie backscattered light at the emitting wavelengths (532 and 355nm) emitted by one Nd:YAG laser, as well as the Raman light (607 and 386nm) inelastically backscattered by Nitrogen molecules at Hefei (117.3oE, 31.9oN), China from 2007 to 2013. From the four return signal profiles, aerosol high accurate extinction and the backscatter coefficients, lidar ratio, Ångström exponent and aerosol Junge exponent can be determined. Furthermore, with the priori assumption of nr=1.50, the profiles of more aerosol microphysical parameters can be retrieved with their respective errors, such as imaginary part of refractive index, Junge number density coefficient, particle mass index. 179 nights profiles of aerosol microphysical parameters had been obtained. Their variation and statistic feature were discussed.

Electrically tuned whispering gallery modemicroresonantor based on Kagomé photonic crystalfibers infiltrated with nematic liquid crystals

Fansheng Kong, Bin Yang, Chengkun Yang, Hao Zhang, Bo Liu, Haifeng Liu, and Jie Yu

Doc ID: 347589 Received 05 Oct 2018; Accepted 13 Jan 2019; Posted 14 Jan 2019  View: PDF

Abstract: In this study, an electrically tunable whispering gallery mode (WGM) microresonator based on Kagomé hollow- core photonic crystal fiber (HC-PCF) is proposed by infiltrating the cross sectional air holes with nematic liquid crystals (NLCs). Experimental results indicate that the LC molecules turn out planar alignment. As the applied electric field strength gradually increases, the WGMs resonance wavelengths shift toward longer wavelength region. The Freedericksz transition threshold of the proposed Kagomé HC-PCF microresonator is experimentally proved to be around 1. 2 Vµm-1. The electrically tunable microresonator integrated with NLCs is anticipated to find potential applications in optical filtering, all-optical switching, and electrically controlled micro-optics devices.

Characterization of cyclical Spatial HeterodyneSpectrometers for astrophysical and planetary studies

Sona Hosseini

Doc ID: 348409 Received 15 Oct 2018; Accepted 13 Jan 2019; Posted 14 Jan 2019  View: PDF

Abstract: High-resolution spectroscopy can make key science measurements for a variety of astrophysics and planetarytargets including solar system planetary atmospheres, comets, solar wind charge exchange emission, and theinterstellar and interplanetary medium. With the ability to record adjoining spectral lines simultaneously keyisotopic ratios such as D/H, 12C/13C, 16O/18O, etc. can be measured precisely. Traditional high spectral resolutionspectrometers are usually required to couple to large optics to compensate for their low throughput, which causesmajor disadvantages for achieving compactness, in particular in space and remote field applications. Also, the highcost of building and maintaining limits their quantity and usage for the long duration temporal measurement of thesources. Spatial Heterodyne Spectrometers (SHS) are based on a novel technique and are making headway as analternative to commonly used high spectral resolution spectrometers in science observations and industry. Todate, SHS instruments come in two major architecture: Michelson design and cyclical design. Cyclical SHS, alsoknown as reflective SHS can offer significant advantages in obtaining high-resolution spectra in shorterwavelengths. Although cyclical SHSs are presented before, there has been no mathematical and performancecharacterization of their technique. This report presents a comprehensive mathematical design and performanceof the cyclical tunable SHS technique to enable and expand its usage in a variety of platforms and applications, inthe industry and astronomical observations from the ground and space telescopes.

Fiber-optic Fabry–Perot pressure sensorbased on sapphire direct bonding for hightemperature applications

Wangwang Li, Ting Liang, Ping-gang Jia, Cheng Lei, Yingping Hong, Yongwei Li, Zong Yao, Wenyi Liu, and Jijun Xiong

Doc ID: 355887 Received 19 Dec 2018; Accepted 12 Jan 2019; Posted 14 Jan 2019  View: PDF

Abstract: In this study, a fiber-optic Fabry–Perot (FP) high-temperature pressure sensorbased on sapphire direct bonding is proposed and experimentally demonstrated. The sensor isfabricated by direct bonding of two-layer sapphire wafers, including a pressure diaphragmwafer and a cavity-etched wafer. The sensor is composed of a sensor head which contains avacuum-sealed cavity arranged as a FP cavity and a multimode optical fiber. The externalpressure can be measured by detecting the change in FP cavity length of the sensor.Experimental results demonstrate the sensing capabilities for pressures from 20 kPa to 700kPa up to 800 °C.

A characterization setup for event-based imagersapplied to modulated light signal detection

Damien JOUBERT, Mathieu Hébert, Hubert Konik, and Christophe Lavergne

Doc ID: 346967 Received 02 Oct 2018; Accepted 11 Jan 2019; Posted 14 Jan 2019  View: PDF

Abstract: Event-based cameras bring new perspectives forperception systems by making them faster, smarter,and less energy-consuming. While they are spreadinginto many application domains, new algorithms aredesigned for the treatment of the data they provideand new databases are needed to validate and trainthem. Simulations are an efficient way to increasedatabases, as it gives direct access to ground truthfor applications such as target detection or depthestimation. But it is provided the simulation modelsused are as close as possible to the physical reality.The model should also be designed generic enough tobe applicable to different kind of event-based imagers.The characterization setup proposed in this paper aimsat measuring the main characteristics of the DVS sensorin each pixel under outdoor lighting conditions. Asimulation model of the imager’s response can begenerated using the measured characteristics. Thesemeasurements are used to estimate the robustness of analgorithm to detect modulated light signals exploitingevent-based data. An improvement is provided to astate of the art LED detection algorithm, and improveits performance to detect light signals modulated athigh frequencies.

Fast Calculation Method with FoveatedRendering for Computer-Generated Hologramsusing Angle-Changeable Ray-Tracing Method

WEI LINGJIE and Yuji Sakamoto

Doc ID: 346028 Received 17 Sep 2018; Accepted 11 Jan 2019; Posted 11 Jan 2019  View: PDF

Abstract: The computer-generated hologram (CGH) technique is a technique that simulatesthe recording of holography. Although the CGH technique has a lot of advantages, it also hassome disadvantages; one of them is the long calculation time. Many researches on the humaneye have established that human sees 135 vertically and 160 horizontally, but can only see finedetail within a 5 central circle. Foveated rendering uses this characteristic of the human eye toreduce the image resolution in the peripheral area and achieve a high calculation speed. In thispaper, a new method for CGH fast calculation with foveated rendering using an angle-changeableray-tracing method is introduced. The experiments demonstrate the effectiveness and high-speedcalculation of this method.

Ultra-sensitive polymeric waveguide temperaturesensor based on asymmetric Mach-Zehnderinterferometer

Donghai Niu, Lilei Wang, Qiang Xu, Minghui Jiang, Xibin Wang, Xiaoqiang Sun, Fei Wang, and Da-Ming Zhang

Doc ID: 351601 Received 09 Nov 2018; Accepted 11 Jan 2019; Posted 11 Jan 2019  View: PDF

Abstract: We proposed and designed an ultra-sensitive polymeric waveguide temperature sensor based onasymmetric Mach-Zehnder interferometer which has different widths in the two interferometer arms.Polymer with larger thermo-optic coefficient (TOC) is employed to enhance the sensitivity of the waveguidetemperature sensor. The influences of the width difference between the two arms and the claddingmaterials with different TOCs on the sensitivity of the sensor were studied and experimentallydemonstrated. The devices were fabricated by using the standard photolithography and simple all-wetetching process. When the cladding material Norland Optical Adhesive 73 (NOA 73) and the widthdifference of 6.5 μm were selected, the sensitivity of the waveguide temperature sensor was measured to be30.8 nm/℃. Moreover, the minimum temperature resolution is about 0.97×10-3℃. The proposed sensorhas the distinct advantages of high sensitivity, high resolution, easy fabrication, low cost and biologicalcompatibility, which make it have the potential applications in temperature detections of organism,molecular analysis and biotechnology.

Experimental investigation on the nonlinear dynamicsof two mutually coupled 1550 nm multi-transversemodevertical-cavity surface-emitting lasers

Wen-Yan Yang, Guang-Qiong Xia, Elumalai Jayaprasath, Zao-Fu Jiang, Yu-Shuang Hou, Chun-Xia Hu, and Zheng-Mao Wu

Doc ID: 355722 Received 18 Dec 2018; Accepted 11 Jan 2019; Posted 11 Jan 2019  View: PDF

Abstract: We experimentally investigate the nonlinear dynamics of two mutually coupled 1550 nm multi-transverse-modevertical-cavity surface-emitting lasers (VCSELs). The results show that, through continuously varying couplingcoefficient, the Y-polarization fundamental transverse mode (Y-LP01) and the Y-polarization first-order transversemode (Y-LP11) in both VCSELs can be driven into period one, period doubling, multi-period and chaos states. Whenthe two mutually coupled VCSELs are simultaneously operating at the periodic state, the localized synchronizationsbetween the corresponding modes are observed. Moreover, mappings of dynamical states for typical transversemodesof the two mutually coupled VCSELs in the parameter space of the frequency detuning and couplingcoefficient are specified.

Suppression of FM-to-AM conversion inbroadband Nd:glass regenerative amplifierwith intra-cavity birefringent filter

Jiangtao Guo, Jiangfeng Wang, Xue Pan, Xinghua Lu, Gang Xia, Xiao Wang, Simin Zhang, Wei Fan, and Li xuechun

Doc ID: 354709 Received 05 Dec 2018; Accepted 10 Jan 2019; Posted 11 Jan 2019  View: PDF

Abstract: In order to suppress the frequency modulation to amplitude modulation (FMto-AM) conversion induced by a Nd:glass regenerative laser amplifier, a birefringent quartzcrystal was designed by theoretical simulation and inserted into the regenerative amplifier. Abroadband Nd:glass regenerative laser amplifier with a flat top region of ~3.7nm in the gainspectrum was developed. An all-fiber front-end system was used to generate a 2-ns shapedpulse with a spectral width of ~0.5nm, which was broadened by a two-stage phase modulator.Then the laser pulse was amplified by a spectral broadened regenerative amplifier. Theamplified output temporal waveform modulation depth was reduced from a maximum of 47.7%to 17.3% at a center wavelength of 1053.328 nm. The experimental results show that the FMto-AM conversion can be effectively suppressed in the spectral broadened Nd:glassregenerative laser amplifier, which indicates that it has potential application in the preamplifierof large-scale laser facilities.

Computational Requirements for Real-TimePtychographic Image Reconstruction

Kaushik Datta, Andrew Rittenbach, Dong-In Kang, John Paul Walters, Stephen Crago, and John Damoulakis

Doc ID: 348392 Received 15 Oct 2018; Accepted 09 Jan 2019; Posted 10 Jan 2019  View: PDF

Abstract: Ptychographic imaging techniques can be coupled with tomographic image reconstructiontechniques to obtain cross sectional 3D images with resolution on the nanometerscale. However, such ptychographic x-ray computed tomography (PXCT) techniques require thecollection of a large number of diffraction patterns. This work derives a set of equations thatcan be used to calculate the rate at which data can be collected given an experimental setup. Italso determines the computational system requirements needed to process ptychographic data inreal-time as soon as it has been collected. This will expedite the ptychography step of PXCT.These theoretical results are then applied to performance data collected from reconstructingsimulated diffraction patterns in order to determine the computational resources needed forreal-time ptychographic processing for representative experimental setups. All of our results areindependent of any specific ptychographic reconstruction algorithm.

Wavelength-tuning point diffractioninterferometer resisting inconsistent lightintensity and environmental vibration:Application to high-precision measurementof large-aperture spherical surface

Yue Sun, Hua Shen, Xuan Li, Jia Li, Jinming Gao, and Rihong Zhu

Doc ID: 351926 Received 15 Nov 2018; Accepted 09 Jan 2019; Posted 10 Jan 2019  View: PDF

Abstract: Phase-shifting point diffraction interferometers are used to measure largeaperture spherical optical elements because of their high measurement accuracy. As themost commonly used phase-shifting method, piezoelectric ceramic transducers are facedwith nonlinear problems. Wavelength-tuning is typically used to solve the phase-shiftingproblem; however, it is sensitive to environmental vibrations and light intensity changesduring tuning. Therefore, a global optimization iterative algorithm based on interferogramnormalization is proposed here. The method is insensitive to noise, defects, and lightintensity changes and has strong ability to resist environmental disturbance. Simulationsand experiments are performed to verify the effectiveness of the proposed method.

Theoretical and experimental investigation ofbroadband dispersion tailoring of high-ordermode in hybrid microsphere cavity

Chaozhen Ke, Jing Ma, Yantang Huang, Zhiping Zeng, Xu Canhua, and Jingjing Qin

Doc ID: 342217 Received 13 Aug 2018; Accepted 09 Jan 2019; Posted 09 Jan 2019  View: PDF

Abstract: The large normal dispersion of fundamental mode (TEn=1 mode) in whisperinggallery modes microsphere is detrimental to visible comb generation. Herein, wedemonstrated that this fundamental limitation can be removed by considering the high-orderradial modes (TEn=2 mode) of the hybrid-microsphere-cavity (HMC). The studied HMCconsists of a high-refractive-index coating (TiO2 or HfO2) and silica microsphere. Thesimulated electric field energy distribution and measured Q value in experiment show thatoptical confinement of the coating effectively excites the TEn=2 mode and reduces the freespectral range (FSR) and modal dispersion. In addition, the observed red-shift of WGM anddecrease trend of FSR have good accordance with simulations. The ZDW can be linearlyshifted to shorter-wavelength or even into visible region with reduction of coating thickness orrefractive-index and larger microcavity, which advancs for the visible comb generation.

Supervised Spatio-Spectral Classification ofFused Images using Superpixels

Karen Sanchez, Carlos Hinojosa, and Henry Arguello

Doc ID: 348427 Received 17 Oct 2018; Accepted 08 Jan 2019; Posted 09 Jan 2019  View: PDF

Abstract: The low spatial resolution of the hyperspectral (HS) images generally limits theclassification accuracy. Therefore, different multi-resolution data fusion techniques have beenproposed in the literature. In this paper, a method for supervised classification of spectralimages from data fusion measurements is proposed. Specifically, the proposed approach exploitsthe spatial information of an RGB image by grouping pixels with similar characteristics intosuperpixels, and fuse such features with the spectral information of an HS image. Simulationsresults on three datasets shown that the proposed classification method improves the overallaccuracy and reduces the computational complexity compared to the traditional approach thatfirst performs the fusion followed by the classification.

Ammonia measurements with femtosecondlaser-induced plasma spectroscopy (FLIPS)

Dayuan Zhang, Qiang Gao, Bo Li, Jixu Liu, and ZhongShan Li

Doc ID: 353209 Received 30 Nov 2018; Accepted 08 Jan 2019; Posted 08 Jan 2019  View: PDF

Abstract: Femtosecond laser-induced plasma spectroscopy (FLIPS) for in-situ ammonia(NH3) measurements was demonstrated in NH3/N2 mixtures. When femtosecond laser at 800 nm was focused at the flow field, the parent NH3 molecules would be photolyzed to generate NH fragments, and then indirect measurements of NH3 could be realized by detecting the NH fluorescence (A3Π− X3Σ-) at 336 nm. A detection limit of 205 ppm could be reached. This work is the first attempt for ammonia measurements with femtosecond laser, and the obtainedresults are useful for the development of ammonia diagnostics.

Simultaneous measurements of mixturefraction and flow velocity using 100 kHz 2DRayleigh scattering imaging

Naibo Jiang, Paul Hsu, Paul Danehy, zhili zhang, and Sukesh Roy

Doc ID: 349631 Received 31 Oct 2018; Accepted 08 Jan 2019; Posted 08 Jan 2019  View: PDF

Abstract: Two-dimensional (2D) Rayleigh scattering (RS) imaging at an ultrahigh repetitionrate of 100 kHz is demonstrated in non-reacting flows employing a high-energy burst-modelaser system. Image sequences of flow mixture fraction were directly derived from high-speedRS images. Additionally, a 2D instantaneous flow velocity field at 100 kHz was obtainedthrough optical-flow-based analysis of the RS images. In further analysis of both the mixturefraction and flow velocity field, the result for the centerline mixture fraction agreed well withthe scaling law. The demonstrated high-speed RS technique in conjunction with optical-flowbasedanalysis provides non-intrusive, simultaneous measurements of the flow mixing andvelocity field, extending the measurement capability of the RS technique to high-speed nonreactingand reacting flows.

Measurement of the inner diameter of monocapillarywith confocal X-ray scattering technology based oncapillary X-ray optics

Xiao Zhang, Yabing Wang, Yufei Li, Zhiguo Liu, Tianxi Sun, and Xuepeng Sun

Doc ID: 351489 Received 08 Nov 2018; Accepted 08 Jan 2019; Posted 08 Jan 2019  View: PDF

Abstract: The inner diameter is one of most important parameters in the design and fabrication ofmonocapillary X-ray optics which are widely used in X-ray technology. The confocal X-ray scatteringmethod based on X-ray capillary optics was proposed to nondestructively measure the inner and outerdiameters of the monocapillary. The positions of the boundaries of monocapillary X-ray optics weredetermined by a knife-edge scanning method and the X-ray optics was profiled in two planes or in thethree-dimensional space accordingly. This confocal method could conveniently give the inner surfacetopography of the monocapillary optics which can be used to show the difference between the actualinner surface and the theoretical one, and has potential applications in nondestructive measurements ofstratified substances, or the profile morphology of specific interface.

Fuzzy c-means clustering based segmentation and thefiltering method for discontinuous ESPI fringe patterns

wenjun xu, Chen Tang, Min Xu, and Zhenkun Lei

Doc ID: 351751 Received 13 Nov 2018; Accepted 08 Jan 2019; Posted 08 Jan 2019  View: PDF

Abstract: The filtering of ESPI fringe patterns with both noise and discontinuity is a challenging problemraised in recent years. Discontinuity-detectable and discontinuity-aware processing techniques are demanded. Inthis paper, a fuzzy c-means (FCM) clustering based fringe segmentation method is proposed. By applying the FCMclustering method to the estimated fringe orientation, we segment the discontinuous ESPI fringe patterns intocontinuous segments, thus the discontinuous region is identified and a discontinuous region mask is generated.Then the discontinuous region mask is introduced into the controlling speed function and an adaptive shapepreservingoriented partial differential equation (OPDE) model is proposed for discontinuous ESPI fringe patternsdenoising. According to our method, the discontinuous regions are effectively found and with the proposedadaptive shape-preserving OPDE, the noise is well eliminated, the shape of fringes and the discontinuity are wellkept. The performance of our method is illustrated with three computer-simulated and one experimentallyobtained discontinuous ESPI fringe patterns and comparison with related segmentation methods and OPDEs.

Fast-Adaptive Color-Collaborative Constellation Designs for Multi-Color MIMO-VLC Systems

Ye Xiao, Zhu Yi-Jun, zhang Yan-yu, and Zheng-Guo Sun

Doc ID: 352016 Received 14 Nov 2018; Accepted 07 Jan 2019; Posted 08 Jan 2019  View: PDF

Abstract: A fast-adaptive color-collaborative signal constellation (CCSC) is proposed for chromaticity-changeable multi-color multi-input multi-output (MIMO) visible light communications (VLC) systems. The design of CCSC aims at developing the constellation to minimize the average optical power with shaping based lattice code. For multi-color VLC signals, we get that the optimum shape of the constellation bounding region is an inequilateral $N$-D simplex. With the densest lattice packing structure, detailed design steps of CCSC are fully elaborated by lattice construction, effective points selection and chromaticity adjustment. As CCSC has a low complexity, its constellation structure can adapt fast to changeable chromaticity demands. Simulation results show that the performance of CCSC is better than the enhanced standard color shift keying (CSK) and is close to the iterative CSK modulation based on numerical search.

Surface plasma influence on nanosecond laserablation

Vasily Lednev, Pavel Sdvizhenskii, Roman Asyutin, Mikhail Grishin, Roman Tretyakov, and Sergey Pershin

Doc ID: 349642 Received 30 Oct 2018; Accepted 07 Jan 2019; Posted 08 Jan 2019  View: PDF

Abstract: The comparison of laser ablation and plasma evolution has been carried out for a molten steel sample in theabsence and in the presence of a surface plasma. Continuous wave (cw) laser beam was utilized for local melting ofa steel (Fe >99% wt.) sample, but it also induced a surface plasma according to optical emission spectroscopy. Cwlaser was switched off for a few milliseconds to dissipate the surface plasma but surface temperature did notchange according to optical pyrometer measurements. Molten metal was ablated by a nanosecond Nd:YAG laserpulse during cw laser operation and when it was switched off for five milliseconds. Comparison of laser ablationand plasma evolution in presence and in absence of the near surface plasma induced by cw laser beam has beencarried out. Time integrated plasma imaging detected slightly greater emissivity of the plasma induced during cwlaser operation. Cw laser operation resulted in a two-fold enhancement of the intensity of atomic lines in spectra aswell as slower decay of plasma emission. Plume temperature and electron density were slightly greater at earlystages of plume expansion in surface plasma.

Homography Based Identification for Automatic and Robust Calibration of Projection Integral Imaging Displays

Lode Jorissen, Jackin Boaz Jessie, Ryutaro Oi, Koki Wakunami, Makoto Okui, Yasuyuki Ichihashi, Gauthier Lafruit, Kenji Yamamoto, and Philippe Bekaert

Doc ID: 349957 Received 01 Nov 2018; Accepted 07 Jan 2019; Posted 08 Jan 2019  View: PDF

Abstract: Recent advances in the creation of micro-lens arrays as holographic optical elements (HOEs) allow the creation of projector based see-through light field displays suitable for augmented reality. These systems require an accurate calibration of the projector with relation to the micro-lens array, as any small misalignment causes the 3D reconstruction to fail. The methods reported so far, require precise placement of the calibration camera w.r.t the lens array screen, which affects the display configuration. We propose a calibration approach which is more robust, and which allows free camera placement. Hence, it does not limit the capabilities of the system. Both a homography based technique and structured light play a central role in realizing such a method. The method was tested on a projection based integral imaging display system consisting of a consumer-grade projector and a digitally designed holographic optical element (DDHOE) based micromirror-array screen. The calibration method compensates for the lens distortion, intrinsics and positioning of the projector with relation to the screen. The method uses a single camera and doesn't require the use of obtrusive markers as reference. We give an in-depth explanation of the different steps of the algorithm, and verify the calibration using both a simulated and a real-world setup

Broadband light absorption enhancement inrandomly rotated elliptical nanohole arrays forphotovoltaic application

Xuefei Qin, Yonggang Wu, Zongyi Zhang, Zihuan Xia, Jian Zhou, and jianwei zhu

Doc ID: 348067 Received 12 Oct 2018; Accepted 07 Jan 2019; Posted 08 Jan 2019  View: PDF

Abstract: Semiconducting nanohole arrays have been considered as a promising candidate for high efficiency solar cells. In thisarticle, optical absorption property of randomly rotated elliptical nanohole arrays consisting of 1×1, 2×2, and 4×4 cellshas been investigated. It’s found that average ultimate efficiency of the arrays increases with the increase of the size ofthe supercell. The 4×4 array has the highest ultimate efficiency, and the efficiency of the 4×4 array is less sensitive to theparameters of the random rotation angle than that of the 1×1 and 2×2 arrays. The comparison of absorption spectra ofthe three arrays shows that the number of absorption peaks of the 1×1 array is the least, but the peak is the highest andnarrowest, and that of the 4×4 array is the most, but the peak is the lowest and broadest. The spatial Fourierspectroscopy analysis of the array shows that the 4×4 arrays have the most Fourier spectrum component and the largestabsorption mode density. The enhancement of optical absorption of the 4×4 array is attributed to the folding of energybands and the increase of energy density of states caused by large supercells, and the over-coupling between incidentlight and Bloch resonant modes in the structure. The improved stability of the ultimate efficiency of the 4×4 arrays isdue to the fact that the distribution of the energy density of states of the 4×4 arrays with different random parameterstends to be the same, which leads to almost the same absorption efficiency of the different 4×4 arrays.

All-optical De-aggregation from 8PSK to 3×BPSK basedon FWM in HNLF

Limeng Pan, Hongxiang wang, and Yuefeng Ji

Doc ID: 349351 Received 26 Oct 2018; Accepted 07 Jan 2019; Posted 08 Jan 2019  View: PDF

Abstract: A scheme is proposed for all-optical de-aggregation from one 30 G-bit/s eight-phase-shift-keying (8PSK)signal to three 10 G-bit/s binary-phase-shift-keying (BPSK) signals based on four-wave mixing (FWM)in high nonlinear fiber (HNLF) without information loss or redundancy. The coded information of threeBPSK signals after the de-aggregation represents the every bit of coded information of input 8PSK signalrespectively. We conducted the theoretical analyses and simulations of the proposal. The error-vectormagnitude(EVM), bit-error rate (BER) and constellations are analyzed for system performance evaluation.The results show that when the optical signal-to-noise ratio (OSNR) of the input 8PSK signal is 18 dB and30 dB, the phase standard deviations of output BPSK signals decrease about 6.5 degrees and 1.5 degreesafter the de-aggregation, the OSNR-BER performance of the extracted BPSK signals is almost coincidewith the ideal BPSK signal, and it has 21 dB and 12 dB receiver OSNR difference respectively at the BERof 10􀀀3 indicating a larger noise tolerance compared to the input 8PSK signal. The scheme provides aneffective way of all-optical de-aggregation from 8PSK to BPSK to suit for the future dynamically reconfigurableoptical network, and makes it more effectual and easier for the receiving terminal which doesn’thave the matching 8PSK receiver.

Improved ozone DIAL retrievals in the uppertroposphere and lower stratosphere using an optimalestimation method

Ghazal Farhani, Robert Sica, Sophie Godin, Gerard M. Ancellet, and Alexander Haefele

Doc ID: 349885 Received 01 Nov 2018; Accepted 06 Jan 2019; Posted 07 Jan 2019  View: PDF

Abstract: We have implemented a first-principle Optimal Estimation Method to retrieve ozone density profiles usingsimultaneously tropospheric and stratospheric Differential Absorption Lidar (DIAL) measurements.Our retrieval extends from 2.5km to about 42km in altitude, and in the upper troposphere and the lowerstratosphere (UTLS) it shows a significant improvement in the overlapping region, where the OEM canretrieve a single ozone profile consistent with the measurements from both lidars. Here stratosphericand the tropospheric measurements from the Observatoire de Haute Provence are used, and the OEMretrievals in the UTLS region compared with coincident ozonesonde measurements. The retrieved ozoneprofiles have a small statistical uncertainty in the UTLS region relative to individual determinations ofozone from each lidar, and the maximum statistical uncertainty does not exceed a maximum of 7%.

Symbol Error Rate of Soft-Decision MultiplePulse Position Modulation over TurbulentChannels

Dima Bykhovsky

Doc ID: 351442 Received 19 Nov 2018; Accepted 04 Jan 2019; Posted 07 Jan 2019  View: PDF

Abstract: Soft-decision multiple-pulse-position modulation (MPPM) is one of the favoredfree-space optical (FSO) communication modulations. This paper derives theoretical expressionsfor the symbol error rate (SER) of both fast and slow fading conditions applied for soft-decisionMPPM without channel state information at the receiver (CSIR), as a particular case of nonmemorylesschannel conditions. The theoretical expressions for lognormal and gamma-gammamodeled turbulence were successfully verified by simulation.

Low-voltage-driven smart glass based onmicro-patterned liquid crystal Fresnel lenses

Xiaoqian Wang, Alwin Ming-Wai Tam, Shu-Zhen Jia, Qi Zhang, Xiang-Yu Chen, Ying-Fan Xiong, Qian Zhang, Zhen Liu, Vladimir Chigrinov, Hoi-Sing Kwok, and D Shen

Doc ID: 352572 Received 21 Nov 2018; Accepted 04 Jan 2019; Posted 07 Jan 2019  View: PDF

Abstract: We disclose a method of fabricating a low-voltage-driven smart glass based onmicro-patterned liquid crystal (LC) Fresnel lenses and implement three proof-of-conceptprototypes. Distinct from the conventional LC-based smart windows with the scattering state,the prominence of our proposed LC smart glass in blurry state under both normal and obliqueobservations stems from the image distortion caused by LC Fresnel lenses. Besides, the hightransmittance (>90%) in clear state is obtained by applying a low voltage of 2 V to eachprototype. Moreover, by elaborating the design of the LC smart glass, the reversed switchingstates (i.e. a clear (voltage OFF) state and a blurry (voltage ON) state) as well as fastswitching time can be simultaneously achieved.

CREOL: Design of a hybrid chalcogenide-glass on lithiumniobatewaveguide structure for high-performancecascaded third- and second-order opticalnonlinearities

Guillermo Camacho-González, Marcin Malinowski, Amirmahdi Honardoost, and Sasan Fathpour

Doc ID: 353400 Received 03 Dec 2018; Accepted 04 Jan 2019; Posted 07 Jan 2019  View: PDF

Abstract: Dispersion engineering for efficient supercontinuum generation (SCG) is investigated in a hybrid nonlinearphotonic platform that allows cascaded third- and second-order optical nonlinearities in transverse-electric (TE)guided modes. The highly nonlinear chalcogenide (ChG) waveguides enable SCG spanning over 1.25 octaves (fromabout 1160 to more than 2800 nm at -20 dB below maximum power), while the attained TE polarization iscompatible with efficient second-harmonic generation in a subsequent thin-film lithium niobate (LN) waveguidemonolithically integrated on the same chip. A low-energy pump pulsed laser source of only 25 pJ with 250-fsduration, centered at the 1550 nm wavelength, can achieve such wideband SCG. The presented design is suitablefor the f-to-2f carrier-envelope offset (CEO) detection technique of stabilized optical frequency comb sources.

Direct measurement of CO2 S-branch Ramanlinewidths broadened by O2, Ar, and C2H4

Naibo Jiang, Sukesh Roy, Paul Hsu, and James Gord

Doc ID: 351372 Received 07 Nov 2018; Accepted 04 Jan 2019; Posted 04 Jan 2019  View: PDF

Abstract: Direct measurements of CO2 S-branch Raman coherence-decay lifetimes resultingfrom CO2–O2, CO2–Ar, and CO2–C2H4 collisions by employing time-resolved picosecondrotational coherent anti-Stokes Raman scattering (CARS) spectroscopy are reported. Basedon the measured Raman coherence dephasing rates, the corresponding Raman linewidths ofvarious J levels are obtained. Our measured linewidth data will aid CO2 CARS fitting, whichis applied to the high-accuracy extraction of temperature and species concentrationinformation from CARS spectra.

Self-referenced technology for refractiveindex measurement under mechanicalvibration and temperature fluctuation

Wenping Guo, Renjie Li, Long Yu, Junyao Chen, Wei Li, and Kecheng Yang

Doc ID: 355169 Received 11 Dec 2018; Accepted 04 Jan 2019; Posted 04 Jan 2019  View: PDF

Abstract: A novel critical angle refractometer with self-referenced performance (SRCAR)under mechanical vibration and temperature fluctuation is presented. In a traditional CAR,mechanical vibrations and temperature fluctuations always exist and cause errors. To reducethese errors, a CAR is redesigned by introducing a reference glass with a known refractiveindex so that an exact calibration curve can always be determined even though intensemechanical vibrations exist. To verify the insensitivity to these vibrations, the refractive indexis monitored while the peak acceleration of the vibration is approximately 14 m/s2. TheSRCAR is also used to measure a sample under different temperatures to verify theinsensitivity to temperature fluctuations. Experimental measurements show that the SRCARhas the ability to lower the influences of vibrations as well as temperature fluctuations andretain a high precision of 2.5×10-4 refractive index units (RIU).

Shifting Colored Coded Apertures Design for SpectralImaging

Laura Galvis Carreno, edson mojica, Henry Arguello, and Gonzalo Arce

Doc ID: 348352 Received 17 Oct 2018; Accepted 04 Jan 2019; Posted 07 Jan 2019  View: PDF

Abstract: Compressive Spectral Imaging (CSI) systems sense 3D spatio-spectral data cubes with just a few twodimensional (2D) projections by using a coded aperture, a dispersive element, and a Focal Plane Array(FPA). The coded apertures in these systems, whose main function is the modulation of the data cube, areoften implemented through photomasks attached to piezoelectric devices. A remarkable improvement onthis configuration has been recently proposed, the replacement of the block-unblock coded apertures bypatterned optical filter arrays, referred to as ”colored” coded apertures, which allow spatial and spectralmodulation. When using these colored coded apertures, its real implementation in terms of cost andcomplexity, directly depends on the number of filters to be used as well as the number of shots to becaptured. A shifting color coded aperture optimization featuring these observations is proposed, with theaim to improve the imaging quality reconstruction and to generate an achievable optical implementationwith a limited number of filters, and requiring only one mask to acquire any number of shots. Themathematical model of the computational imaging strategy to overcome the practical limitations of actualCSI systems is presented along with a testbed implementation. Simulations, as well as experimentalresults, will prove the accuracy and performance of the proposed shifting colored coded aperture designover the current literature designs.

Single-shot coherent power-spectrum imagingof objects hidden by opaque scattering media

Wusheng Tang, Jiankun Yang, Wenjun Yi, Qianwen Nie, Jubo Zhu, Mengjun Zhu, Yanfang Guo, Mengzhu Li, Xiujian Li, and Wei Wang

Doc ID: 348020 Received 12 Oct 2018; Accepted 03 Jan 2019; Posted 04 Jan 2019  View: PDF

Abstract: We report coherent imaging of objects behind opaque scattering media with onlyone piece of power spectrum pattern. We solve out the unique solution and improve algorithmspeed for the inverse-problem. Based on the proposed scattering-disturbance model, with onlyone piece of Fourier-transform power spectrum pattern under coherent illumination, wesuccessfully reconstruct clear images of the objects fully hidden by an opaque diffuser. Theexperimental results demonstrate the feasibility of the reconstruction method and thescattering-disturbance model. Our method makes it possible of snapshot coherent imaging theobjects obscured by scattering media, which extends the methodology of X-raycrystallography to visible-light scattering imaging for underwater and living biomedicalimaging.

Design of nonlinearly spaced phase-shiftingalgorithms using their frequency transferfunction

Manuel Servin, Moises Padilla, Msc Garnica, and Gonzalo Paez

Doc ID: 349895 Received 01 Nov 2018; Accepted 03 Jan 2019; Posted 04 Jan 2019  View: PDF

Abstract: Here we show how to design phase-shifting algorithms (PSAs) fornonuniform/nonlinear (NL) phase-shifted fringe patterns using their frequency transferfunction (FTF). Assuming that the nonlinear phase-steps are known, we introduce the desiredzeroes in the FTF to obtain the specific NL-PSA formula. The advantage of designing NLPSAsbased on their FTF is that one can reject many distorting harmonics of the fringes. Wecan also estimate the signal-to-noise ratio (SNR) for interferograms corrupted by additivewhite Gaussian noise (AWGN). Finally, for non-distorted noiseless fringes, the proposed NLPSAretrieves the modulating phase error-free, just as standard/linear PSAs do.

Simple phase-shifting by polarizer rotations in a cube beam-splitter interferometer

Uriel Rivera-Ortega and Dorilian Lopez-Mago

Doc ID: 348638 Received 18 Oct 2018; Accepted 02 Jan 2019; Posted 04 Jan 2019  View: PDF

Abstract: A simple and low-cost method for phase-shifting interferometry by the rotation of a polarizer is presented. This proposal takes advantage of the polarization aberration in a beam-splitter cube due to its geometry, to the angular dependence with the coating and to the polarization angle of the input beam. The interferometric setup performs as a two-window common-path interferometer in which the added phase-shifting is achieved by simply rotating a polarizer at its output plane. The viability of the proposal will be sustained with experimental results in which the phase-shift and the resulting wavefront will be calculated with Farrel and the Three-step PSI algorithm respectively

A Novel broadband LP01-LP02 mode converter for O-, E-, S-, C-, L- and U-band

Dongya Shen, Chuan Ma, Yuan Hong, Wenping Ren, and Xiupu Zhang

Doc ID: 349136 Received 25 Oct 2018; Accepted 02 Jan 2019; Posted 07 Jan 2019  View: PDF

Abstract: This paper proposes a novel all-optical fiber mode converter for mode conversion from LP01 to LP02 and vice versa.The mode converter is formed by connecting a single-mode fiber, a taper-core multi-mode fiber, and a few-modefiber together. The taper fiber core is designed to convert LP01 mode to LP02. The few-mode fiber is used to cut offthe modes that are higher than LP02. It is shown that the proposed mode converter provides 20 dB extinction ratioand low insertion loss in a very broad optical bandwidth of 200 nm, from 1465 to 1665 nm. Further optimizing FMFradius only for each band of O-, E-, S-, C- and U-band etc., the mode converter can apply to any band of interest withhigher performance. It is found that the performance of the mode converter has a large tolerance to structuralparameters. The mode converter has the same performance in reciprocal operation, i.e. LP02 to LP01.

A methodology to design optical systems withcurved sensors

Christophe Gaschet, Wilfried Jahn, Bertrand Chambion, Emmanuel Hugot, Thibault Behaghel, Simona Lombardo, Sabri Lemared, Marc FERRARI, Stéphane Caplet, Stephane Getin, Aurélie Vandeneynde, and David Henry

Doc ID: 345654 Received 14 Sep 2018; Accepted 02 Jan 2019; Posted 03 Jan 2019  View: PDF

Abstract: Curved sensors are a suitable technological solution to enhance the vast majority ofoptical systems. In this work, we show the entire process to create curved sensor-based opticalsystems and the possibilities they offer. This paper defines the boundaries of the reachablecurvatures for a full range of monolithic sensors. We discuss how the curved focal plane shapeis related to the imaged scenes and optical parameters. Two camera prototypes are designed,realized and tested, demonstrating a new compact optical architecture for a 40 degree compactobjective, as well as a wide field fisheye zoom objective using a convex sensor to image a 180degree field of view.

Toward a Multimodal Fusion of LayeredCultural Object Images: Complementarity ofOptical Coherence Tomography and TerahertzTime-domain Imaging in the Heritage Field

Corinna Ludovica Koch Dandolo, Maxime Lopez, Kaori Fukunaga, YOSHIMI UENO, Ruven Pillay, David Giovanacci, Yann Le Du, Xueshi Bai, Michel Menu, and Vincent Detalle

Doc ID: 346467 Received 20 Sep 2018; Accepted 02 Jan 2019; Posted 03 Jan 2019  View: PDF

Abstract: Terahertz time-domain imaging (THz-TDI) and Spectral domain opticalcoherence tomography (SD-OCT) are two techniques capable of providing 3Ddatasets from which depth profiles and cross-sectional images of an object can bederived. They are novel photonics technologies of particular relevance to the field ofheritage science, for which the comprehension of the stratigraphic structure of acultural heritage object may help in the understanding of its artistic technology andstate of preservation. The differences in imaging depth, field of view and axial/lateralresolutions of the two imaging techniques provide different but complementaryinformation of the same scene. It follows that the user will benefit from a detailedcomparison of the information content of the two different datasets and images,which would ultimately relies on multimodal image fusion. Consequently we havedeveloped a first data processing chain with the aim of representing THz-TDI andSD-OCT cross-sectional images in a unique image grid and space, in which thedifferent datasets are dimensionally consistent.

Numerical simulations of partially coherentillumination for multi-scattering phase objects viaa beam propagation method

Yoshimasa Suzuki, Satoshi Watanabe, mayumi odaira, Toshiro Okamura, and Yoshimasa Kawata

Doc ID: 346908 Received 27 Sep 2018; Accepted 02 Jan 2019; Posted 03 Jan 2019  View: PDF

Abstract: Many studies have performed imaging under partially coherent illumination.However, to the best of our knowledge, there are no imaging methods for complicated objectssuch as cell colonies, which are large and diffract light multiple times. In this paper, wepropose an image calculation method for the partially coherent illumination of a large-scalethree-dimensional multi-diffractive object. The image is calculated via the summation ofcoherent images of each illumination angle using the beam propagation method. We apply thismethod to various microscopic observations, including phase contrast and differentialinterference contrast. Our method shows excellent agreement with experimental images of abead and a photonic crystal fiber. As with a cell colony, our method reproduced thecharacteristics of the image through experimentation. Finally, we discuss the accuracy and therestriction conditions of our method.

Automated, Unsupervised Inversion of MultiwavelengthLidar Data With TiARA: Assessment of RetrievalPerformance of Microphysical Parameters UsingSimulated Data

Detlef Mueller, Eduard Chemyakin, Alexei Kolgotin, Richard Ferrare, Chris Hostetler, and Anton Romanov

Doc ID: 346995 Received 28 Sep 2018; Accepted 02 Jan 2019; Posted 04 Jan 2019  View: PDF

Abstract: We evaluate the retrieval performance of the automated, unsupervised inversion algorithm TiARA(Tikhonov Advanced Regularization Algorithm) which is used for the autonomous retrieval of microphysicalparameters of anthropogenic and natural pollution particles. TiARA (version 1.0) has been developedin the past 10 years and builds on the legacy of a data-operator controlled inversion algorithm that is usedsince 1998 for the analysis of data from multiwavelength Raman lidar. The development of TiARA hasbeen driven by the need to analyze in (near) real-time large volumes of data collected with NASA LangleyResearch Center’s HSRL-2 (High-Spectral-REsolution Lidar). HSRL-2 was envisioned as part of theNASA ACE (Aerosols-Clouds-Ecosystems) mission in response to the NAS Decadal Study (DS) missionrecommendations 2007. TiARA could thus also serve as inversion algorithm in the context of a futurespace-borne lidar. We summarize key properties of TiARA on the basis of simulations with monomodallogarithmic-normal particle size distributions which cover particle radii from approximately 0.05 – 10 mm.The real and imaginary parts cover the range from non-absorbing to highly light-absorbing pollutants.Our simulations included up to 25% measurement uncertainty. The goal of our study is to provide guidancewith respect to technical features of future space-borne lidars if such lidars will be used for retrievalsof microphysical data products, absorption coefficients, and single-scattering albedo. We investigated theimpact of two different measurement-error models on the quality of the data products. We also obtainedfor the first time a statistical view on systematic and statistical uncertainties if a large volume of data isprocessed. Effective radius is retrieved to 50% accuracy for 58% of cases with an imaginary part up to 0.01iand up to 100% of cases with an imaginary part of 0.05i. Similarly, volume concentration, surface-areaconcentration and number concentrations are retrieved to 50% accuracy in 56-100% of cases, 99-100% ofcases, and 54-87% of cases, respectively, depending on the imaginary refractive index. The numbers representmeasurement uncertainties of up to 15%. If we target 20% retrieval accuracy, the number of casesthat fall within that threshold are 36-76% for effective radius, 36-73% for volume concentration, 98-100%for surface-area concentration, and 37-61% for number concentration. That range of numbers again representsa spread in results for different values of the imaginary part. The real part should be retrieved toapproximately 0.075 or better. At present we obtain an accuracy of (on average) 0.1 for the real part. A casestudy from ORACLES is used to illustrate data products obtained with TiARA.

Lidar thermometry using two-line atomic fluorescence

Elin Malmqvist, Jesper Borggren, Marcus L.E. Alden, and Joakim Bood

Doc ID: 347062 Received 02 Oct 2018; Accepted 02 Jan 2019; Posted 04 Jan 2019  View: PDF

Abstract: In this work, Scheimpflug Lidar has been combined with the thermometric technique two-line atomic fluorescence(TLAF), to carry out stand-off, spatially resolved temperature measurements. Indium atoms were seeded into amodified Perkin-Elmer-burner and two tunable single-mode diode lasers with their wavelengths tuned to 410.17nm and 451.12 nm were used to excite the seeded atoms. The fluorescence signal was collected using both a linescandetector and a two-dimensional intensified CCD (ICCD) camera. One-dimensional flame temperature profileswere measured at different heights above a porous-plug burner, located at a distance of 1.5 m from the Lidarsystem. The technique was also used to demonstrate two-dimensional temperature measurements in the sameflame. The accuracy of the measured temperature was found to be limited mainly by uncertainty in the spectraloverlap between the laser emission and the indium atom absorption spectrum as well as uncertainty in laserpower measurements. With the constraint that indium can be introduced into the measurement volume, it isanticipated that the developed measurement concept could constitute a valuable tool, allowing in-situ spatiallyresolved thermometry in intractable industrial applications, sufferings from limited optical access, thus requiringremote single-optical-port sensing.

Point-to-multipoint and ring network communication based on chaotic semiconductor lasers with optical feedback

Qiliang Li, Qi Bao, DeWang Chen, Shuna Yang, Miao Hu, Ran Zeng, Hao Chi, and Shuqin li

Doc ID: 351814 Received 13 Nov 2018; Accepted 01 Jan 2019; Posted 02 Jan 2019  View: PDF

Abstract: Inthispaper,twoconfigurationsofpoint-to-multipoint(PTM)andringnetwork,basedonthechaoticsemiconductorlasersubjecttoopticalfeedback,areinvestigated.AbifurcationdiagramandthemaximumLyapunovexponent(MLE)inthesystemhavebeenusedtodistinguishtheexistenceofchaos,andthecomplexdegreeofthechaoticoutputismeasuredthroughLempel-Zivcomplexity(LZC).Theseresultsshowthatthefeedbackstrengthhasasignificanteffectonthedynamicsofsystem,namely,theincreaseofitcaninducethesystemtoenterintochaos.InPTMmodel,itcanbeseenthatarbitraryreceiverlaser(RL)andthecentraltransmitterlaser(TL)areidenticallysynchronized,andmoreover,thesynchronizationsolutionsarerobust;themessagecanbeencodedbymodulatingthebiascurrentofthecentralTL,andateachRLendthemessagefromTLcanbesimultaneouslyrecoveredbymonitoringthepowererrorbetweenRLandTL.Asaresult,theunidirectionalbroadcastmessagetransmission,basedonPTM,canbewellachieved.Intheringnetworkconfiguration,thecouplingbetweentwoadjacentlasersthroughapartiallytransparentmirrorinducesthedelayandchaoticdynamics.Weprovethatthedynamicsisidenticallysynchronized,andthesynchronizationagainstexternalperturbationalsopossessesagoodrobustness;themessageintroducedonarbitrarytwolasersinthisringnetworkcanbesimultaneouslyexchanged.

Huygens’s Principle: Exact and approximatewavefronts propagated through conic lenses

Maximino Avendaño Alejo, M. Carmen López-Bautista, Luis Castañeda, and Samuel Maca García

Doc ID: 351885 Received 16 Nov 2018; Accepted 01 Jan 2019; Posted 02 Jan 2019  View: PDF

Abstract: Exact and approximate formulae for refracted wavefronts through singlet lensesare obtained by considering an incident plane wavefront propagating along the optical axis.We provide two different approaches for the wavefronts approximated at second order basedon Huygens’ Principle and Malus-Dupin theorem respectively. We have in the first methodfound a way to use iterative wavelets, instead of the usual evaluated integral to arrive at theseformulas, showing a physical and mathematical correspondence between both methods. Finallywe introduce a parabolic wavefront into the Irradiance Transport Equation in order to provide ananalytical solution for the distribution of illumination.

External right angle measurement using a twoautocollimatorsystem

Yun He, Qi Liu, Jingjing He, Zhijie He, Zezhu Hu, Huizong Duan, and Hsien-Chi Yeh

Doc ID: 348658 Received 18 Oct 2018; Accepted 01 Jan 2019; Posted 04 Jan 2019  View: PDF

Abstract: We report on a non-contact method for external right angle measurement using two autocollimators. A precisemathematical model is deduced to evaluate and deduct the measuring error. Based on the calibration using ninehollow rectangular prisms, the values measured with our method are well-coincident compared with the resultsmeasured by a ZYGO interferometer. The measuring accuracy is superior to 0.1 arc-second for the right-angleerrors within 3.0 arc-second and becomes 0.4 arc-second for the extended right-angle errors within 8.0 arc-second.This method can be widely used in the situations for external right angle measurement, such as angle measurementfor the body of the torsion balance and the test mass in spaceborne laser interferometry.

Pupil segmentation in the light-field cameraand its relation to 3-dimensional objectpositions and the reconstructed depth of field

Gene Serabyn

Doc ID: 346096 Received 17 Sep 2018; Accepted 01 Jan 2019; Posted 10 Jan 2019  View: PDF

Abstract: A ray-trace simulation of the light-field camera is used to calculate point sourceresponses as a function of 3-dimensional source positions. Each point source location yields aunique and well-determined segmented-pupil pattern in the lenslet array’s focal plane, withlateral object offsets changing the pattern’s location and symmetry, and defocus distancesaltering the pattern’s diameter. Segmented-pupil images can thus be used to infer pointsources’ 3-dimensional locations. Numerical simulations show that the centroids and widthsof segmented pupil images can be used to deduce lateral image positions to the size a detectorpixel, and image defocus to the accuracy of the lenslet focal length. In sparse-source cases,such as, e.g., fluorescence microscopy or particle tracking, 3-dimensional point-sourcelocations can thus be accurately determined from the observed point source response patterns.The degree of pupil segmentation also directly constrains the ability to refocus light-fieldimages – for image defocus distances large enough that the number of pupil segments exceedsthe number of pixels within a “whole” pupil behind a single lenslet, the image can no longerbe brought to focus numerically, thus defining the light-field camera’s depth-of-field. Thisconstraint implies a depth-of-field larger than the usual imaging depth-of-focus by a factor ofthe number of detector pixels per lenslet, consistent with the general expectation.

Accurate diffraction field calculation method based onL1-norm minimization from three-dimensional objects

Gokhan Esmer

Doc ID: 346078 Received 12 Oct 2018; Accepted 31 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: Calculation of three-dimensional (3D) diffraction field from arbitrarily distributed field samples over 3Dspace is an important problem in holographic 3D television systems. Straightforward superposition ofdiffracted fields from the samples may not provide accurate calculation of the diffraction field becauseof the possible mutual couplings between those samples. We define an inverse problem to overcomethat deviation caused by mutual couplings. First, the diffraction field on a reference plane is estimatedaccurately from the known field values at the sampling points. Then, the diffraction field over entirespace can be calculated from the field on the reference plane. Sparse representation of the diffractionfield on the reference plane may provide suitable framework in terms of L1-norm minimization. Oncethe diffraction field over the reference plane is obtained, harmonics that form the diffraction field canbe calculated. After that, field over the entire 3D space can be found by using those harmonics. In thiswork, we proposed a method based on SPGL1 algorithm that solves the the inverse problem of accuratecalculation of diffraction field on the reference plane by using fewer number of samples in calculationcompared to the methods based on L2-norm minimization. Furthermore, the proposed method requiresless memory allocation as well.

Reduction of Non-uniformity for a 16×16Arrayed Waveguide Grating Router Based onSilica Waveguides

Xiang Xia, Tingting Lang, Libin Zhang, and Zhonghua Yu

Doc ID: 351494 Received 09 Nov 2018; Accepted 30 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: Here, a newly-designed 16×16 cyclic arrayed waveguide grating router,capable of achieving loss uniformity across the whole free spectral range (FSR), isfabricated and experimentally demonstrated. This device is based on commonly-usedsilica waveguides, which are compatible with basic planar lightwave circuit technology.The design, simulation, and experimental verification of the proposed method arepresented, with the experimental results showing that the loss non-uniformity of FSRreduced from 2.70 dB to 1.05 dB using this new design. This design only brings in tinychange of mask and real estate.

High power pulse, pulse pair and pulse traingenerated by breathers in dispersionexponentially decreasing fiber

Heping Jia, Rongcao Yang, Jinping Tian, and Wenmei Zhang

Doc ID: 351321 Received 07 Nov 2018; Accepted 28 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: Based on the derived rational solutions of the nonautonomous nonlinearSchrödinger equation with varying coefficients, we present a simple scheme to generate highpower pulse, pulse pair and pulse train with non-oscillating amplitudes in dispersionexponentially decreasing fiber. Without requiring to eliminate the background, the stablepulse train can be generated from the first-order Akhmediev breather, and the high powerpulse and pulse pair can be generated from the second-order Kuznetsov-Ma breather.Moreover, it is found that the characteristics of these pulses can be controlled by adjustingeigenvalue parameter and fiber parameters. The results presented here are expected to beuseful in large capacity and high power optical communication system.

Spectroscopic Investigation of High-PressureFemtosecond Two-Photon LIF of CO up to 20bar

Yejun Wang and Waruna Kulatilaka

Doc ID: 352159 Received 20 Nov 2018; Accepted 28 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: Extension of laser diagnostic methods to high pressure is critically importantbecause most practical combustion systems operate at elevated pressures. However, increasedcollisional quenching, fluorescence trapping, and other spectroscopic complications makehigh-pressure laser diagnostics extremely challenging. As the pressure increases, collisionaleffects broaden and shift excitation spectral lines, reducing the excitation quantum efficiencyof the laser-induced fluorescence (LIF) technique, in particular when using conventionalnarrowband, nanosecond-duration laser pulses. In this work, spectroscopic investigation ofbroadband, femtosecond two-photon LIF (fs-TPLIF) of CO was performed in a high-pressurestatic gas cell, up to total pressures of 20 bar. The fluorescence emission spectrum broadenedmarginally at the highest pressure investigated and hence can be neglected in most cases. Thesub-quadratic dependence of the CO fs-TPLIF signal on the laser fluence increased as thepressure is increased. Moreover, the CO fs-TPLIF signal decays slower with increasingpressure compared to the previously reported ns-TPLIF data. The signal drop when the totalpressure is increased from 1–13 bar is approximately 30% in the fs excitation, as compared toapproximately 60% drop in the ns excitation in CO/N2/O2 mixtures. The pressure effects onthe fluorescence signal were observed to be similar in the Ångström and third positive bands,suggesting that the third positive band could also be used for CO measurements withbroadband fs laser pulses. Furthermore, experimentally investigated are the effect of pressureon the CO fluorescence signal in different quenching gases using fixed CO mole fractions, aswell as number densities. Overall, the fs-TPLIF scheme is shown to be a promisingdiagnostics tool for CO detection in practical combustion systems at elevated pressure.

Automatic Morphological Filtering Algorithmfor Airborne LiDAR Data in Urban Areas

Zhenyang Hui, Leyang Wang, YAO YEVENYO ZIGGAH, Shangshu Cai, and Yuanping Xia

Doc ID: 343185 Received 30 Aug 2018; Accepted 28 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: Filtering is a key step for most airborne LiDAR post-applications in urban areas.To solve the problems of complex parameter settings and low filtering accuracy incomplicated urban environments, an automatic morphological filter was proposed. In thispaper, the optimal maximum filtering window can be determined automatically by applying aseries of morphological top-hat operation. Meanwhile, the thresholds for filtering werecalculated adaptively according to the gradient changes. Seven publicly available datasetsprovided by the ISPRS were used to evaluate the performance. Experimental results show thatthe proposed method achieved an average total error of 4.07% and an average kappacoefficient of 90.90%, which are the best performances when comparing to some otherfiltering methods.

Rapid quantitative protein detection byLight Transmission Spectroscopy

Alison Deatsch, Arial Shogren, Scott Egan, Jennifer Tank, Nan Sun, Steven Ruggiero, and Carol Tanner

Doc ID: 345185 Received 06 Sep 2018; Accepted 27 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: Rapid, sensitive, and quantitative protein detection is critical for many applicationsin medicine, environmental monitoring, and the food industry. Advancements in detection ofproteins include the use of antigen-antibody binding, however many current methods aretime-consuming and have limiting factors such as low sensitivity and the inability to provideabsolute values. We present a new high-throughput method for protein detection using LightTransmission Spectroscopy (LTS), which can quantify and size nanoparticles in fluidsuspension. LTS can quantify proteins directly and target specific proteins through antigenantibodybinding. This work shows that LTS can distinguish between and quantify bovineserum albumin, its antibody, and the BSA+Ab complex and determine BSA proteinconcentrations down to 5 μg/mL. We use both Mie and discrete dipole approximation modelsto provide geometric insight into the binding process.

MTF spectral characteristics in turbid atmosphere andits application for imaging band selection

Xin Zheng, Pengfei Wu, and ruizhong rao

Doc ID: 346168 Received 17 Sep 2018; Accepted 27 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: The formalized modulation transfer function (MTF) is used to describe the effects induced by the turbidatmosphere on image quality. The spectral characteristics of formalized MTF is analyzed in detail here. The zeroand nonzero spatial frequency components of formalized MTF, which represent different image information, showstrong wavelength dependence. Furthermore, both components vary sharply at some wavelengths, which issignificantly correlated with molecule absorption. The formalized MTF spectral characteristic is obviously differentfrom atmospheric transmittance. According to its spectral characteristic, the turbid atmosphere effects on imagingcan be predicted and a waveband selection method for optimal imaging was proposed. Comparisons between theproposed and other method show the good consistency at some wavebands. The simulating imaging results andactual imaging results both verify that the optimal imaging band analysis and selection method is effective.

Exposure Study on UV-induced Degradationof PTFE and Ceramic Optical Diffusers

Benjamin Tsai, Catherine Cooksey, David Allen, Christopher White, Eric Byrd, and Deborah Jacobs

Doc ID: 347597 Received 08 Oct 2018; Accepted 27 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: We report on a study of the ultraviolet (UV) induced degradation on optical gradepolytetrafluoroethylene (PTFE) and ceramic diffuser samples. Long term UV exposure maysignificantly alter the reflectance and lead to an error in the calibration of optical instruments.A large integrating sphere was used to irradiate the samples for 334.7 d at an irradiance levelof 194.9 W/m2. Samples were qualified and measured for reflectance factor, bidirectionalreflectance distribution function (BRDF), and fluorescence, before and after the exposure, andat 12-week intervals during the exposure. This study revealed significant differences betweenthe aging behavior of ceramic and PTFE samples.

Light scattering by pure water and seawater:the depolarization ratio and its variation withsalinity

Xiaodong Zhang, Dariusz Stramski, Rick Reynolds, and E. Blocker

Doc ID: 352197 Received 16 Nov 2018; Accepted 27 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: We measured the linearly polarized scattering of pure water and seawater atvarious salinities and estimated the depolarization ratio using five different methods of data analysis after removing the scattering due to contamination by residual nanoparticles. The depolarization ratio values (δ) estimated for pure water using these different methods are largely consistent with each other and result in a mean value of 0.039 ± 0.001. For seawater,our results reveal a trend of a slight linear inc nity (S), δ = 0.039 + a1×S, where a1 varies in the range of 1×10-4 to 2×10-4 ethods.

110.4 mJ, 1 kHz repetition rate, Ho:YAG master-oscillator power amplifier

Chuanpeng Qian, baoquan yao, Youlun Ju, Xiaoming Duan, Benrui Zhao, Tongyu Dai, and Yuezhu Wang

Doc ID: 349510 Received 29 Oct 2018; Accepted 27 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: We reported a high energy, high pulse repetition frequency Ho:YAG master oscillator and power amplifier (MOPA), which was resonantly dual-end-pumped by Tm:YLF lasers at room temperature. At the pulse repetition frequency of 1 kHz, the Ho:YAG MOPA laser system produced a maximum pulse energy of 110.4 mJ with a 28 ns pulse width, corresponding to a peak power of approximately 3.94 MW. The output wavelength of Ho:YAG MOPA laser system was 2090.9 nm. In addition, the beam quality factor M2 of about 1.7 was achieved at maximum output level.

Tunability of Hi-Bi photonic crystal fiberintegrated with selectively filled magneticfluid and microfluidic manipulation

Weiheng Wang, Miao Yinping, Li Zhen, Zhang Hongmin, Li Bin, Yang Xiaoping, and Jian-Quan Yao

Doc ID: 349401 Received 29 Oct 2018; Accepted 27 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: Optical fiber microfluidics technology can implement the mutual tune of light fieldand fluid in micro-nano scale. In this paper, the one core of high-birefringence photoniccrystal fiber (Hi-Bi PCF) is used as a microfluidic channel. The birefringence of Fe3O4nanofluid is experimentally and theoretically investigated by selectively infiltrating themagnetic fluid into the core of the Hi-Bi PCF. The presence of magnetic fluid alters thebirefringence of the original Hi-Bi PCF and can be modulated by the intensity of the externalmagnetic field. The optical field distribution was simulated and the birefringence of the Hi-BiPCF with selective filling was approximately 6.672×10-4. The experimental results show thatthe structure has a highly linear response to the external magnetic field from 0Oe to 300Oeand the sensitivity is 16.8pm/Oe with a high resolution of 1.19Oe. Due to several advantagessuch as all fiber compact structure, low transmission loss and high linear response, this devicecan find various applications including the weak magnetic field measurement with highaccuracy, optical fiber gyroscopes, and magneto-optic modulators. Especially, it also hasimportant significance to realize the all-fiber microfluidic chip laboratory.

Holographic waveguide head-up display with 2-Dpupil expansion and longitudinal image magnification

Craig Draper, Colton Bigler, Micah Mann, Kalluri Sarma, and Pierre-Alexandre Blanche

Doc ID: 345913 Received 14 Sep 2018; Accepted 26 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: Head-up displays (HUDs) are used in aircraft to overlay relevant flight information onthe vehicle’s external for pilots to view with continued focus on the far field. In thesesystems, the field of view (FOV) is traditionally limited by the size of the projectionoptics. Though classical HUD systems take a significant amount of space in the flightdeck, they have become a necessity in avionic transportation. Our research aims toreduce the size of the HUD footprint while offering a wide FOV projected in the far fieldwith an expanded pupil. This has been accomplished by coupling the image-bearinglight into a waveguide under total internal reflection conditions, redirecting that light inthe orthogonal direction, and then out-coupling the light toward the pilot. Each step wasachieved using holographic optical elements. The injection hologram has optical powerto obtain longitudinal magnification, whereas the redirection hologram expands thepupil in 1 dimension and the extraction hologram expands the pupil in a 2nd dimension.Varying diffraction efficiency along the direction of the light propagation ensures evenimage intensity throughout the expanded pupil. We used ray tracing optical simulationsto optimize the design of the system and present a fully operational demonstrator of theHUD. This HUD produces an image with a FOV of 24°x 12.6°at a viewing distance of 4.5in. (114 mm) from the waveguide, with infinite longitudinal magnification and 1.9× by1.6× horizontal and vertical pupil expansion, respectively.

Demonstration of resolving power λ/Δλ > 10,000 for a space-based x-ray transmission grating spectrometer

Ralf Heilmann, Jeffery Kolodziejczak, Alexander Bruccoleri, Jessica Gaskin, and Mark Schattenburg

Doc ID: 347998 Received 11 Oct 2018; Accepted 26 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: We present measurements of the resolving power of a soft x-ray spectrometer consisting of 200 nm-period lightweight, alignment-insensitive critical-angle transmission (CAT) gratings and a lightweight slumped-glass Wolter-I focusing mirror pair. We measure and model contributions from source, mirrors, detector pixel size, and grating period variation to the natural line width spectrum of the Al and Mg Kα₁α₂ doublets. Measuring up to 18th diffraction order at characteristic Al-K wavelengths we consistently obtain small broadening due to gratings corresponding to a minimum grating resolving power R_g > 10,000 with 90% confidence. Upper limits are often compatible with $R_g = \infty$. Independent fitting of different diffraction orders, as well as ensemble fitting of multiple orders at multiple wavelengths, gives compatible results. Our data leads to uncertainties for the Al-Kα doublet line width and line separation parameters 2-3 times smaller than values found in the literature. Data from three different gratings are mutually compatible. This demonstrates that CAT gratings perform in excess of the requirements for the Arcus Explorer mission and are suitable for next-generation space-based x-ray spectrometer designs with resolving power 5-10 times higher than the transmission grating spectrometer on the Chandra X-ray Observatory.

Low-Cost Gaussian Beam Profiling with Circular Irisesand Apertures

Tariq Khwaja and Syed Reza

Doc ID: 348102 Received 12 Oct 2018; Accepted 26 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: The fundamental Gaussian TEM00 mode is the most common mode of propagation within various optical devices,modules, and systems. Beam profilers are widely used in accurately ascertaining the cross-sectional irradianceprofile of a TEM00 mode for free-space optical communication systems as well as tracking beam evolution whenpropagating within optical submodules. We demonstrate beam profiling methods that use low-cost, off-the-shelf,widely available circular apertures such as circular irises and spatial filters. In order to demonstrate beamprofiling with any circular aperture, we first derive exact analytical expressions for power transmittance of theTEM00 mode through a decentered circular aperture and then use this mathematical derivation to estimate theirradiance profile of a Gaussian beam by 1) fixing the location of a circular aperture and changing its radius, and 2)scanning the entire area of the beam profile by translating a circular aperture of a fixed radius across the region ofinterest. This method is fast and easily reproducible and simply puts to use circular irises/circular spatial filterswhich are commonly available in most optical laboratories. Consequently, the proposed method provides a cheapand convenient means to estimate the profile of a Gaussian beam with simple optical components. Ourexperimental results demonstrate a performance which is comparable to a standard knife-edge-based estimate ofbeam profile. Moreover, a strong agreement with presented theory validates the analytical expressions derived inthis paper.

Optimization-based real-time open-loop control of anoptofluidic refractive phase modulator

Pouya Rajaeipour, Kaustubh Banerjee, Hans Zappe, and Caglar Ataman

Doc ID: 348183 Received 12 Oct 2018; Accepted 26 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: We present a novel open-loop control method for an electrostatically-actuated optofluidic refractive phasemodulator, and demonstrate its performance for high-order aberration correction. Contrary to conventionalelectrostatic deformable mirrors, an optofluidic modulator is capable of bidirectional (push-pull)actuation through hydro-mechanical coupling. Control methods based on matrix pseudo-inversion, thecommon approach used for deformable mirrors, thus perform sub-optimally for such a device. Instead,we formulate the task of finding driving voltages for a given desired wavefront shape as an optimizationproblem with inequality constraints that can be solved using an interior-point method in real-time. Weshow that this optimization problem is a convex one, and that its solution represents a global minimumin residual wavefront error. We use the new method to control both the refractive phase modulator anda conventional electrostatic deformable mirror, and experimentally demonstrate improved correctionfidelity for both.

Three degrees of freedom laser interferometerbased on differential wavefront sensing withwide angular measurement range

Fuzhong Yang, Ming Zhang, Weinan Ye, and Leijie Wang

Doc ID: 349003 Received 22 Oct 2018; Accepted 25 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: We present a three-degree-of-freedom laser interferometer based on differentialwavefront sensing with wide angular measurement range. To obtain measurement signalswith high AC/DC ratio and improve the linearity of differential wavefront sensing in widerange angular displacement measurement, fiber bundle instead of quadrant photodiode isapplied to receive the interference light. Meanwhile, a decoupled algorithm with quadraticcorrection derived by the ray tracing method and kinematic analysis is detailed in the case ofwide range angular displacement. The simulation and experimental results prove that the laserinterferometer with the proposed structure could realize hundreds of microradian range ofangular displacement measurement, which are expanded in the differential wavefront sensing.

A multiple-camera holographic system featuringefficient depth grids for representation of real 3Dobjects

Yu Zhao, Munkh-Uchral Erdenebat, MD-SHAHINUR ALAM, Mei-Lan Piao, Jeon Seok, and Nam Kim

Doc ID: 345875 Received 17 Sep 2018; Accepted 25 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: Recently, computer-generated holograms (CGHs) of real three-dimensional objects have become widely used tosupport holographic displays. Here, a multiple-camera holographic system featuring efficient depth grid is developedto provide the correct depth cue. Multi-depth cameras are used to acquire depth and color information from realscenes, and then virtually reconstruct point-cloud models. Arranging the depth cameras in an inward-facingconfiguration allowed simultaneous capture of objects from different directions, facilitating rendering of the entiresurface. Multiple relocated point cloud gridding (MR-PCG) method is proposed to generate efficient depth grids byclassifying groups of object points with the same depth values in the red, green, and blue (RGB) channels. Computergeneratedholograms (CGHs) are obtained by applying a Fast Fourier transform (FFT) diffraction calculation to thegrids. Full-color reconstructed images were obtained flexibly and efficiently. The utility of our method was confirmedboth numerically and optically.

A note on the field stabilization control of theE-ELT telescope under wind disturbance

Kainan Wang and André Preumont

Doc ID: 343199 Received 27 Aug 2018; Accepted 25 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: This paper discusses the field stabilization control of the M5 unit under winddisturbances. The first part is a literature survey of the spectral content of the wind disturbance.Next, a simplified model of tip/tilt mirror control system is used to analyze the conditionsfor control-structure interaction. The influence of the asymptotic decay rate of the wind tiltdisturbance on the magnitude and spectral content of the control torques is pointed out. A fulltelescope model is developed to justify a decoupled tip/tilt control design, and to analyze theresponse of the primary mirror M1 to the disturbance generated by the control torques of M5 unit.

Propagation trajectory measurement andautofocusing generation of Airy beams using digitalpropagation

Chaoyue Zhao, Hongwei Li, Jin Wei, Dongmei Wang, and Wei Gao

Doc ID: 352107 Received 19 Nov 2018; Accepted 24 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: We present a method of measuring propagation trajectory of Airy beams using digital propagation based on thetheory of angular spectrum. The dependence of the transverse displacement of Airy beams on artificialpropagation distance in phase masks is investigated with no motion of imaging apparatus. The parabolicpropagation trajectory is experimentally verified, which is consistent with the theoretical predictions. On thisbasis, we generate autofocusing beams by combining multiple Airy beams and digital propagation. Results showthat this technique can provide an accurate and easy measurement of self-accelerating characteristic in a fixedplane, as well as a flexible manipulation without translating the target.

Laser induced breakdown spectroscopy of Aluminum plasma inthe absence and presence of magnetic field

Navid Chishti, Shazia Bashir, Asadullah Dawood, and Muhammad khan

Doc ID: 342309 Received 20 Aug 2018; Accepted 23 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: The effect of magnetic field on Laser Induced Breakdown Spectroscopy (LIBS) of Aluminum (Al) plasma has been investigated. Al targets were exposed to Nd: YAG laser pulses at different irradiances ranging from 1 to 2.7 GWcm-2, under Argon (Ar) and Neon (Ne) environments at various pressures ranging from 5 to 760 torr and at different time delays from0.42 to 9.58 µs. All spectroscopy measurements were performed in the absence and presence of transverse magnetic field of strength 0.9 Tesla. When laser irradiance is increased by keeping the pressure (10 torr) and time delay constant (1.25 µs), both excitation temperature (Te) and number density (ne) increase upto a certain values. Same trend is observed for Te andne when the ambient gas pressureof Ar and Ne is increased by keeping the irradiance (1.7 GWcm-2) and time delay constant. At higher irradiances and pressures, the saturation isobserved which is attributed to self-regulating regime of plasma. In the case of time delay both electron temperature and number density decay exponentially which is according to adiabatic expansion model. It is revealed that emission intensity and electron temperature are higher in the presence of magnetic field as compared to field free case which is attributed to magnetic confinement as well as Joule heating effect. Plasma plume confinement is confirmed by analytical evaluation factor β. β is an analytical factor which is the ratio of plasma pressureto magnetic pressurei. e. β = Plasma pressure . It confirms the validity of magnetic fieldMagnetic pressureconfinement if β is less than 1. As the evaluated values of β are less than 1 for all cases, therefore, they confirm the validity of magnetic ent.

Optimization of injection molding processparameters and axial surface compensationfor producing aspheric plastic lens with largediameter and center thickness

Xirui Lan, Chuang Li, Yang Chao, and Changxi Xue

Doc ID: 351344 Received 07 Nov 2018; Accepted 23 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: Form accuracy is an important parameter to measure whether a plastic lens can beused in imaging optics. Form accuracy exhibited by aspheric plastic lens produced byinjection molding is affected by process parameters and mold core. This paper proposes tooptimize the process parameters through two stages. Stage one: An initial selection of processparameters was conducted in a wide range in virtue of the Taguchi method, and the processparameters were determined based on the signal-to-noise (S/N) ratio which significantlyaffected the axial deformation. Then the initial process parameters were obtained. Stage two:The regression model of process parameters was established according to the response surfacemethodology (RSM), with the optimal process parameters finally determined. For reducingthe form accuracy error of aspheric plastic lens caused by material shrinkage and machiningerror of mold core, an axial deformation compensation model was established. The asphericplastic lens with form accuracy of 1.013μm was experimentally verified, which met therequirements of imaging optics.

Propagation of Bessel-Gaussian beam in agradient-index medium

Shixin Pei, Shanshan Xu, Fenping Cui, Qingwei Pan, and Zhaolou Cao

Doc ID: 347023 Received 01 Oct 2018; Accepted 23 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: Based on the ABCD matrix method and Collins diffraction integral formula,analytical expression for Bessel-Gaussian beams propagation in a gradient-index medium isderived. The propagation trajectory, intensity and phase distributions of the zeroth-order,second-order and superposition cases are numerically investigated. The effect of beam waistradius w0 on the properties of the beam propagation in a gradient-index medium is discussedin detail. The result shows that the beam is focused at z/L = N/2 (N = 0,1, 2,…) and propagatesperiodically in the medium. Evolution of vortical structure of superposed Bessel-Gaussianbeam is investigated, showing that the superposed beam forms new singularities and therotation of the beam mainly occurs near the singularities.

Time-varying tool influence function model of bonnetpolishing for aspheric surfaces

Bo Zhong, Chunjin Wang, Xianhua Chen, and Jian Wang

Doc ID: 347570 Received 05 Oct 2018; Accepted 23 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: For bonnet polishing of an aspheric surface, the tool influence function (TIF) is inevitably time-varying, induced bythe different surface curvatures on the aspheric surface. Accordingly, this paper investigated how the surfacecurvature affects the bonnet-workpiece contact area, and then presented a time-varying TIF model. The timevaryingTIF was modelled based on the finite element analysis and kinematics analysis methods, and validated byexperiments. The experimental results exhibited good agreement with the theoretical results. The proposedmethod can forecast the TIF for different polishing positions on aspheric surfaces, and provide the theoreticalfoundation for dynamic compensation of aspheric surface polishing.

Application of Laser Induced BreakdownSpectroscopy (LIBS) to assess palladium catalystdeactivation

SAHAR BELYANI, Mohammad Keshavarz, seyyed mohammad reza darbani, and Masoud Kavosh Tehrani

Doc ID: 349137 Received 24 Oct 2018; Accepted 23 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: This work introduces a new method for investigation of palladium (Pd) catalyst deactivation byLaser Induced Breakdown Spectroscopy (LIBS). For this purpose, deactivation of Pd/(OH)2/Ccatalyst for synthesis of hexanitrohexaazaisowurtzitane (HNIW or CL-20) as a high performanceenergetic compound was studied. LIBS spectrum of fresh catalyst (Pd/(OH) 2/C) with 10% Pdwas compared to spent catalyst (Pd/C) containing 7% Pd. LIBS tests are also carried out underargon (Ar) ambient gas in order to correlate with the same one under air atmosphere.Experimental results indicate that line intensities of Pd was lower for all of the spent catalystsamples under the same conditions. The C2 swan bands are also greater in spent catalyst becauseof deactivation, which provides the fewer amount of Pd in active sites of carbon. Furthermore,the intensity of Hα in spent catalyst is lower than fresh one because of conversion of Pd(OH)2/Cto Pd/C during deactivation.

Optical Design of a Multi-Channel Narrow-Band Imager for Lyman UltravioletObservation of Diffuse Sources

Zheng Lou, Li Ji, and Sen Wang

Doc ID: 348023 Received 30 Oct 2018; Accepted 22 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: This paper describes a novel optical design for a multi-channel narrow-bandimager observing at the Lyman ultraviolet wavelengths. As one of the key instrumentsonboard the Census of Warm-Hot Intergalactic Medium, Accretion, and Feedback Explorer(CAFE) space mission, the imager is designed to map the neutral hydrogen Lyman-α lineemissions from the intergalactic medium and nearby galaxies. The optical design features aninstantaneous FOV of 20 arcmin in diameter and a moderate and adjustable spectralresolution of 500~2000. A highly dispersive monochromator system is used to split theincident light into several wavelength channels, each with a full-field imaging capability andadjustable bandwidth, and the ensuing imaging optics form the individual channel images ondifferent areas of the same microchannel plate detector. Channel wavelengths are tunable anda continuous wavelength scanning across the entire band of interest is proposed, which yieldsspectrally resolved 3D images with moderate spectral resolutions.

Fast and easy fabrication methodology of Fresnelzone plates for the EUV and soft x-ray region

Andreas Schümmer, Hnas-Christoph Mertins, Claus Schneider, Roman Adam, Stefan Trellenkamp, René Borowski, Larissa Juschkin, and Ulf Berges

Doc ID: 348060 Received 12 Oct 2018; Accepted 22 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: Zone plate design and efficient methods for the fabrication of zone plates for theEUV and soft X-ray applications in a newly developed scanning reflection microscope arepresented. Based on e-beam lithography three types of transmission zone plates with focallength between 6 mm and 15 mm are reported: i) phase shifting zone plates made by 190 nmthick PMMA rings on Si3N4 membranes, ii) absorbing zone plates made by 75 nm thick Au -ring structures on Si3N4 and ii) free standing Au rings of 50 nm thickness and increasedtransmission in the EUV range. Experiments at the DELTA synchrotron facility reveal aminimum spot size and resulting spatial resolution of 9 ± 3 􀟤􀝉 which is the theoretical limitresulting from the synchrotron beam parameters at 60 eV photon energy. Images of a Ti/Sichess board test pattern are recorded exploiting the energy dependence of the element specificreflectance.

Classification between digs and dust particles onoptical surfaces with acquisition and analysis ofpolarization characteristics

Fan Wu, Yongying Yang, Jiabin Jiang, Pengfei Zhang, Yanwei Li, Xiang Xiao, Guohua Feng, Jian Bai, Kaiwei Wang, Qiao Xu, hongzhen jiang, and Bo Gao

Doc ID: 349404 Received 26 Oct 2018; Accepted 22 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: In the automatic detection for surface defects of optical components, the digs and dust particles exhibit similarfeatures: point-like shape and variable intensity reflectivity. On this condition, these two types with entirelydifferent damages are easily confused so that misjudgments will be induced. To solve this problem, a Polarization-Characteristics-based Classification method of Digs and Dust particles (PCCDD) is proposed based on thepolarimetric imaging technique and dark-field imaging technique. Firstly, a dark-field imaging system equippedwith a Polarization State Generator (PSG) and a Polarization State Analyzer (PSA) is employed to measure andestablish normalized Mueller Matrices datasets of digs and dust particles. And by a nonlinear global searchcombined with a separability evaluation method, the optimal number of acquisitions and correspondingpolarization measurement states of the PSG and the PSA are obtained, as well as the parameters of classificationfunction. Then, multiple polarization images are acquired under the optimal states to extract a multi-dimensionalfeature description that relates only to the polarization characteristics of the defect, which subsequently acts as theinput vector of the classifier to finally achieve the classification. This method takes full advantage of the differenceon polarization characteristics between digs and dust particles, and the features that the properties of digs arerelatively invariant while those of dust particles are changeable. The classification process involves only simplematrix operations. Compared with the traditional discrimination method based on intensity images, the featuresobtained by this method have a higher separability. Experiments show that the classification accuracy reaches over90%. This method can be further applied to the recognition and discrimination of other defects in the field ofsurface defects detection.

Numerical and experimental investigations of pressure-driven gas flow in Hollow-Core Photonic Crystal Fibres

Billah Masum, Saiied Aminossadati, Mehmet Kizil, and Christopher Leonardi

Doc ID: 348241 Received 16 Oct 2018; Accepted 21 Dec 2018; Posted 21 Dec 2018  View: PDF

Abstract: A comprehensive understanding of gas flow behaviour in long Hollow-Core Photonic Crystal Fibres (HC-PCFs) is critical in evaluating their sensing performance for low concentration gases, especially in terms of response time. The aim of this paper is to numerically and experimentally investigate the pressure-driven gas flow dynamics in a relatively long HC-PCF based gas sensor. The gas flow in the core of a 1.1 m long HC-PCF was numerically modelled to examine the gas sensing response time in terms of the time for the gas to fill the core (gas filling time). The model was validated against the experimental results of continuous-wave modulated photothermal spectroscopy. The model was then used to analyse the effects of gas inlet pressure, core diameter, fibre length and gas type on the gas flow field and gas filling time. The results revealed that a lower gas filling time was achieved as the pressure difference between the inlet and outlet increased, the core diameter increased and/or the core length decreased.

Low-Voltage Wide Field-of-View LIDAR ScanningSystem Based on MEMS Mirror

Jingkun Zhou and Keyuan qian

Doc ID: 342010 Received 09 Aug 2018; Accepted 21 Dec 2018; Posted 02 Jan 2019  View: PDF

Abstract: LIDAR has been widely used in many fields such as autopilot and target detection.However, commonly used LIDAR with a rotary mechanical structure is difficult to achieve highvertical resolution. Some LIDARs with Micro-Electro-Mechanical-System(MEMS) union aredriven by high voltage and cannot uniformly scan in a large scan angle. This paper proposes auniform scanning system in wide Field-of-View(FOV) based on MEMS mirror for 3D imagingLIDAR. We use a dual-axis electromagnetic driving MEMS mirror which can be used forarbitrary-direction optical beam steering with a low operating voltage. We design a uniformangle scanning system and set up the scanning system to analyze the scan angle, spot size andluminous flux on the target plane. The experimental results show that this system can scanuniformly within a large FOV with small spot size at target plane one hundred meters away.

Stress-induced optical waveguides written by an ultrafast laser in Nd3+, Y3+ co-doped SrF2 crystals

B. Hari Babu, Chengkun Lyu, Thomas Billotte, D. Pallares Aldeiturriaga, Bertrand Poumellec, Jose-Miguel Lopez-Higuera, Xiaotao Hao, and Matthieu Lancry

Doc ID: 347120 Received 01 Oct 2018; Accepted 20 Dec 2018; Posted 21 Dec 2018  View: PDF

Abstract: The femtosecond (fs) laser-induced stress affected zone is an efficient tool to produce birefringence, and the refractive index contrast in the Nd3+, Y3+ co-doped SrF2 crystal with respect to different pulse energies, and repetition rates. To avoid an excessive heat accumulation as the waveguides are fabricated with a repetition rate of 500 kHz, minimum propagation loss in codoped SrF2 crystal is 1.63 ± 0.21 dB/cm for TM polarization at a 632.8 nm. The measured retardance can be interpreted by stress-induced birefringence in response to free of stress volume expansion photo-induced in the non-spherical irradiated zone. The steady-state and time-resolved photoluminescence properties are also carried out in and out of the laser irradiated zone enable the local changes of the Nd3+ and Y3+ network before and after written optical waveguides by using an fs laser in co-doped SrF2 crystals.

A Single-shot Wavelength-independent Phase-shifting Method for Full-field Optical Coherence Tomography

Yue Zhu and Wanrong Gao

Doc ID: 349124 Received 24 Oct 2018; Accepted 20 Dec 2018; Posted 21 Dec 2018  View: PDF

Abstract: One limitation of a PZT-based phase-shifting method in full-field optical coherence tomography (FFOCT) is that there exist interference residuals because a light source with a broadband is used. In this work, an achromatic phase-shifting method was proposed in which a linear polarizer and a quarter-wave plate were employed to generate the circularly polarized light in the reference arm of a basic Linnik interferometer. The light field reflected from the reference arm is supposed with the unpolarized light backscattered from the sample when the path difference is within the coherence length of the light source. A first phase difference of π/2 can be generated on the propagation of superposed light beams through the polarized beam splitter (PBS). An additional phase difference of π/2 can be obtained by the proposed numerical method, thus producing the similar effects as four-frame phase-shifting way. An en face tomographic image can be obtained with a single-shot in this new FF-OCT system. The axial and lateral resolution of the system is around 1.375µm and 0.9µm, respectively. The system offers a dynamic range of ~57dB and an imaging rate of 30fps. Tomographic images of Intel microchip, onion cells and microcracks in a glass were displayed with clear sub-structures. This article aims at producing fringe-free OCT images in a single shot.

Background luminescence in x-ray luminescencecomputed tomography (XLCT) imaging

Michael Lun and Changqing Li

Doc ID: 351976 Received 19 Nov 2018; Accepted 20 Dec 2018; Posted 21 Dec 2018  View: PDF

Abstract: X-ray luminescence computed tomography (XLCT) is an emerging hybrid imaging modality. It has been recentlyreported that materials like water, tissue, or even air can generate optical photons upon x-ray irradiation whichcan increase the noises in measurements of XLCT. In this study, we have investigated the x-ray luminescence fromwater, air, as well as tissue mimicking phantoms, including one embedded with a 0.01 mg/mL GOS:Eu3+microphosphor target. We have measured the optical emission spectrum from each sample, including samples ofmeat and fat, using a spectrograph. Our results indicate that there are plenty of optical photons emitted by x-rayirradiation and a small phosphor concentration, as low as 5.28 μM in a deep background can provide enoughcontrast for XLCT imaging.

Apochromatic lens design in short-wave infrared band using the Buchdahl dispersion model

wei wang, Xing Zhong, Jiang Liu, and Xiaoheng Wang

Doc ID: 346848 Received 26 Sep 2018; Accepted 20 Dec 2018; Posted 20 Dec 2018  View: PDF

Abstract: Chromatic aberration is an important artifact that influences imagine quality. Thus, it should be optimized during lens design. However, the typical combination and selection method of glass materials for visible band can hardly satisfy the apochromatic requirements of short-wave infrared (SWIR) lenses. Therefore, we propose a method of glass selection for apochromatic lens design in SWIR band through vector operation based on Buchdahl model and third-order aberration theory. The proposed method overcomes the limitations of traditional methods and the unstable calculation results of special material properties. A design example is presented, which indicates that the proposed method can correct the secondary spectrum in SWIR band and simplify the design using ordinary mass-produced glasses.

Broadband aberration-corrected snapshotspectrometer with a toroidal slicer mirror

Yinxin Zhang, Zhenkun Zhang, Huaidong Yang, Yun Zhang, Zhanhua Huang, and Guofan Jin

Doc ID: 347185 Received 01 Oct 2018; Accepted 20 Dec 2018; Posted 20 Dec 2018  View: PDF

Abstract: We demonstrate a broadband aberration-corrected snapshot spectrometer bydeveloping a toroidal slicer mirror as the focusing mirror. A collimating slicer mirror and anintegrated grating divide the entire wavelength range into several windows. The toroidalsub-mirrors of the focusing mirror compensate the coma and correct the astigmatism atdifferent windows to compress the spectral spots over the waveband. From 200 nm to 1000nm, the RMS spot radii are less than 30 μm and the spectral resolution at 600 nm is 151.8 pm.The optics has a small volume of 11 cm × 11 cm × 1.5 cm by employing folded structure.

Non-refracted extraordinary rays in a uniaxial crystal

Pengqian Wang

Doc ID: 348566 Received 17 Oct 2018; Accepted 19 Dec 2018; Posted 20 Dec 2018  View: PDF

Abstract: We theoretically investigate non-refracted extraordinary rays where the ray does not change its directionwhen transmitted from vacuum into a uniaxial crystal even at oblique incidence. This is possible onlywhen the optic axis is in the plane of incidence. We find that within the usual birefringence range of pno ne n2o, for a given angle of cut, there exits only one angle of incidence that produces a nonrefractedextraordinary ray. Beyond this range, the number of solutions may be up to three. Numericalexamples are given. All cases can be solved algebraically from a quartic equation.

Inline Laser Power Measurement by PhotonMomentum

John Lehman, Kyle Rogers, Daniel Rahn, and Paul Williams

Doc ID: 349222 Received 05 Nov 2018; Accepted 19 Dec 2018; Posted 20 Dec 2018  View: PDF

Abstract: We present a novel measurement scheme and instrumentation for quantifying laser power by means of photonmomentum. The optical design is optimized such that the incoming laser beam is minimally perturbed and isavailable for other purposes along the incoming beam axis. Additionally, the geometry of the instrument givesaccess to the small but measurable transmittance between two passive mirrors that face the force sensor. The forcesensor is based on a commercially available weighing instrument (“scale”) that has a temporal response ofapproximately 5 sec and a readability of approximately 1 μg (~2 W). Our measurement results demonstrate beamprofile and power for 500 W, but the mirror and mass (or force) calibration are suitable for very high power up to50 kW and beyond. The optics are based on commercially available, off-the-shelf mirrors optimized for the angle ofincidence and maximum reflectance at the wavelength of 1070 nm. The size of the complete instrument has aninput aperture of ø75 mm, but this constraint is only a matter of optimizing the beam path and box geometry.

Simulation and Observation for Volume Emission Rates Emittedfrom O2(0-1) and O(1S) Nightglow at Northwest China

Yuanhe Tang, Peng Sun Sun, Haiyang Gao, Jin Cui, Zijian Li, Haoxuan Wang, huan lv, Min Jia, Hanchen Liu, Cunxia Li, and Qingsong Liu

Doc ID: 351182 Received 06 Nov 2018; Accepted 19 Dec 2018; Posted 20 Dec 2018  View: PDF

Abstract: Being susceptible to the change of atmospheric conditions, the volume emission rate (VER) is verysuitable to be used as a light source by passive remote sensing for measuring atmospheric wind and temperature.Thus, the VERs emitted from O2(0-1) and O(1S) of nightglow at 80-120 km are studied in this paper. Based onthe NRLMSISE-00 (Naval Research Laboratory Mass Spectrometer Incoherent Scatter) model dataand the GBAII (ground based airglow imaging interferometer) instrument observation for a local time andplace simulated VER profiles represented by four layers are obtained for the nightglow of O2(0-1) and O(1S).The O2(0-1) nightglow model peak values at 94 km on Dec. 6th, 2013 and Nov. 8th, 2011 are 8111photons•cm-3•s-1 and 8406 photons•cm-3•s-1, respectively; however, the O(1S) VER peak at a higher altitude ofabout 96 km on Dec. 18th, 2011 is only 338 photons•cm-3•s-1. The upper atmospheric VER values have beenderived to transfer into the ground–bsaed detected column intensities by our GBAII (ground-based airglowimaging interferometer) prototype. The calculated column integrated emission rate (IER) of O2(0-1) for 0° and45° zenith angles are 1.48×107 and 1.91×107 photons•cm-2•s-1, respectively; the calculated column IER of O(1S)are 5.53×105 and 7.03×105 photons•cm-2•s-1, respectively. Correspondingly, the detected column IER obtainedby GBAII are 1.87×107 for O2(0-1), and 6.57×105 photons•cm-2 •s-1for O(1S), respectively.

Generating plasmonic vortex field with arbitrarytopological charges and positions by meta-nanoslits

Baojie Tang, Baifu Zhang, and Jianping Ding

Doc ID: 353027 Received 28 Nov 2018; Accepted 19 Dec 2018; Posted 20 Dec 2018  View: PDF

Abstract: A novel plasmonic vortex lens (PVL) consisting of an array of gold film nanoslits for vortex-field generation witharbitrary topological charges and positions is proposed. The performance of the PVL is analyzed theoretically anddemonstrated numerically by the finite element method (FEM). By utilizing symmetric and anti-symmetric phase,the plasmonic vortex generated at the center of PVL can carry arbitrary topological charges (integer or fraction).Two circularly polarized illuminations with opposite spins can excite a composite plasmonic vortex field withsymmetry-breaking distribution, in which the breaking point rotates with the phase difference between two spins.In addition, we can shift the center of plasmonic vortex to any desired position such that a flexible location manipulationof plasmonic vortex is achieved. The designed PVL can also work as a miniaturized polarimeter for characterizingthe state of polarization of the incident light.

Characterization of Metallic-Packaging FiberBragg Grating Sensors with Coated and BareFibers

ym zhang, Fanyong Meng, Yanming Song, mingli dong, and Lianqing Zhu

Doc ID: 345267 Received 06 Sep 2018; Accepted 19 Dec 2018; Posted 19 Dec 2018  View: PDF

Abstract: Metallic packaging of fiber Bragg grating (FBG) sensors is developed using theultrasonic welding method. Both polyimide-coated fiber and bare fiber could be bonded wellto aluminum alloy substrate using Sn-Bi alloy. Two kinds of metal-packaged FBG sensors,coated FBG and bare FBG, are characterized for studying the thermal sensitivity, strainresponse, short-term creep and temporal temperature response. Both FBG sensors showedincreasing sensitivity with temperature from -40 °C to 80 °C. Metal-packaged coated FBGsensor displayed relative strengths in strain stability, repeatability, creep, spectra shape andtemperature response when compared with the bare one. Moreover, the boundaries betweenoptical fiber and metal alloy are intact, and cross-sectional SEM micrographs clearlyillustrated that metal alloy coated well with the coated and bare fiber.

Thermomechanical response of copper films irradiatedby femtosecond-pulsed lasers with dynamicoptical properties

Yunpeng Ren, KAI QIN, Yan Chen, Qing Lin, Dongyang Xu, Zhiduo Xin, Jian Ni, and Liang Ge

Doc ID: 347813 Received 22 Oct 2018; Accepted 19 Dec 2018; Posted 19 Dec 2018  View: PDF

Abstract: By taking account the dynamic thermophysical properties and optical properties,the ultrafast thermoelastic response of thin copper film irradiated by femtosecond laser hasbeen researched. The temperature and stress fields of copper film irradiated by femtosecondlaser are analyzed in this work. The simulation results reveal that the degree of thermomechanicalresponse is much underestimated especially with higher laser fluence and smallerpulse duration. It is necessary to employ dynamic properties in ultrafast thermoelastic simulationfor accuration.

Beam pointing drift prediction in pulsed lasers by a probabilistic learning approach

Hui Chang, Zhongwei Fan, JiSi Qiu, Ge Wenqi, HaoCheng Wang, Ying Yan, XiongXin Tang, Hongbo Zhang, and Hong Yuan

Doc ID: 348946 Received 30 Oct 2018; Accepted 19 Dec 2018; Posted 21 Dec 2018  View: PDF

Abstract: In laser systems, it is well-known that beam-pointing is shifted due to many unmodeled factors such as vibrations from hardware platform and air disturbance. In addition, beam-pointing shift also varies with laser sources as well as time, rendering the modeling of shifting errors difficult. While a few works have addressed the problem of predicting shift dynamics, several challenges still remain. Specifically, a generic approach that can be easilyapplied to different laser systems is highly desired. In contrast to physical modeling approaches, we aim to predict beam-pointing drift using a well-established probabilistic learning approach, i.e., Gaussian Mixture Model (GMM). By exploiting sampled datapoints (collected from laser system) that comprise time and corresponding shifting errors, the joint distribution of time and shifting error can be estimated. Subsequently, Gaussian Mixture Regression (GMR) is employed to predict the shifting error at any query time. The proposed learning scheme is verified in a pulsed laser system (1064nm, Nd:YAG, 100Hz), showing that the drift prediction approach achieves remarkable performances.

A semi-analytical method for n-k inversion ofellipsometry data.

Mickael Gilliot

Doc ID: 348875 Received 23 Oct 2018; Accepted 19 Dec 2018; Posted 19 Dec 2018  View: PDF

Abstract: A semi-analytical method is presented to unambiguously perform the wavelength-bywavelengthextraction of the optical constants (refractive index n and extinction coefficient k) in athin film from the ellipsometry measurement. It works by recasting the ellipsometric equationsunder a parametric polynomial form, and drawing parametric curves from the polynomialsolutions, which intersections at zero define solutions of the ellipsometry problem. The interestof the method is the possibility to extract all the solutions of the considered ellipsometric problemin a given range of n and k values, in contrast to the standard least-squares fitting, which providesa single unsure solution conditioned by initial guess values.

General formula to design freeform singlet freeof spherical aberration and astigmatism

Rafael Gonzalez Acuña, Héctor Chaparro Romo, and Julio Gutierrez-Vega

Doc ID: 351567 Received 09 Nov 2018; Accepted 18 Dec 2018; Posted 19 Dec 2018  View: PDF

Abstract: An analytical closed-form formula for the design of freeform lenses free of sphericalaberration and astigmatism is presented. Given the equation of the freeform input surface, theformula gives the equation of the second surface in order to correct the spherical aberration.The derivation is based on the formal application of the variational Fermat principle under thestandard geometrical optics approximation.

Spatial resolution enhancement forpushbroom-based microscopic hyperspectralimaging

Zhe Jiang, Zekuan Yu, Yue Yu, Zhiyu Huang, Qiushi Ren, and Changhui Li

Doc ID: 348455 Received 29 Oct 2018; Accepted 18 Dec 2018; Posted 19 Dec 2018  View: PDF

Abstract: Hyperspectral imaging (HSI) is a promising tool for microscopic histopathologystudies. Pushbroom microscopic hyperspectral imaging systems are widely used because ofits low cost and easy implementation. However, the spatial resolution of pushbroom HSIsystems is limited by the width of the optical entrance slit. A narrower slit leads to longerexposure time and slower imaging speed. In this paper, we explored several spatial resolutionenhancement algorithms, originally designed for remote-sensing hyperspectral imaging, forpushbroom microscopic HSI systems. Our results demonstrate that those algorithms couldeffectively achieve a higher spatial resolution without sacrificing imaging speed.

Extreme background-rejection techniques forthe ELROI optical satellite license plate

Rebecca Holmes and David Palmer

Doc ID: 347373 Received 02 Oct 2018; Accepted 18 Dec 2018; Posted 19 Dec 2018  View: PDF

Abstract: The Extremely Low-Resource Optical Identifier (ELROI) is a concept for anautonomous, low-power optical “license plate” that can be attached to anything that goes intospace. ELROI uses short, omnidirectional flashes of laser light to encode a unique ID numberwhich can be read by a small ground telescope using a photon-counting sensor and innovativeextreme background-rejection techniques. ELROI is smaller and lighter than a typical radiobeacon, low-power enough to run on its own small solar cell, and can safely operate for the entireorbital lifetime of a satellite or debris object. The concept has been validated in ground tests,and orbital prototypes are scheduled for launch in 2018 and beyond. In this paper we focuson the details of the encoding scheme and data analysis that allow a milliwatt optical signalto be read from orbit. We describe the techniques of extreme background-rejection needed toachieve this, including spectral filtering and temporal filtering using a period- and phase-recoveryalgorithm, and discuss the requirements for an error-correcting code to encode the ID number.Worked examples with both simulated and experimental (long-range ground test) data illustratethe methods used. We present these techniques to describe a new optical communication concept,and to encourage others to consider observing and analyzing our upcoming test flights.

Sparsity-regularized approaches to directlyreconstructing hemodynamic response in brainfunctional diffuse optical tomography

Bingyuan Wang, Yao Zhang, dongyuan liu, Xuemei Ding, mai dan, Tiantian Pan, Huijuan Zhao, and Feng Gao

Doc ID: 336325 Received 28 Jun 2018; Accepted 18 Dec 2018; Posted 19 Dec 2018  View: PDF

Abstract: In brain functional diffuse optical tomography (DOT), the conventional indirect approaches first separatelyreconstruct the spatial changes of the absorption coefficients at every time point and then calculate the spatialexcited levels in terms of the hemodynamic models. The direct approaches combine the two steps necessary in theindirect approaches and obtain the spatial excited levels directly. Although the reconstruction quality has beenimproved by the direct approaches to some extent, they still lack sharp edges and suffer from low spatial resolutionbecause of the ill-posedness of the inverse problems. In this paper, the a priori sparsity is introduced to obtain thesparse solutions and further improve the reconstruction quality. Simulation experiments are conducted toillustrate the expected performance improvements of the proposed approaches.

Bandwidth-enhanced depth priority integralimaging using band-limited diffusingillumination technique

Yimin Lou, Juanmei Hu, Fengmin Wu, and Aixi Chen

Doc ID: 344922 Received 06 Sep 2018; Accepted 17 Dec 2018; Posted 18 Dec 2018  View: PDF

Abstract: Display bandwidth and display mechanism determine the performance of the threedimensional(3D) display system. In this paper, a bandwidth-enhanced depth priority integralimaging (DPII) technique is proposed. Information transmission efficiency (ITE) defined asthe output display bandwidth divided by the input display bandwidth is used to assess the IIsystem. By analyzing the ITE, we find that only a part of input display bandwidth is usedefficiently to present the 3D image in traditional DPII system. The DPII system sacrifices theITE for depth enhancement. The low ITE that fundamentally limits the 3D performance of theDPII system is ascribed to the diffusing illumination mechanism of the display system. Toenhance the 3D performance, a collimated illumination DPII system as a special case of bandlimiteddiffusing illumination technique has been proposed and demonstrated firstly. Thebandwidth and ITE of such DPII system is increased. The depth of field (DOF) of the systemis doubled. The resolution of the 3D image is increased to the level of the resolution priorityII system without sacrificing the viewing angle. More general case, band-limited illuminationDPII system is also demonstrated. By modulating the divergence angle of the illuminationsystem, the 3D image’s resolution and DOF can be controlled. The bandwidth and ITE of theDPII system using band-limited illumination is also higher than that of traditional DPIIsystem. Experiments are presented to prove the bandwidth-enhanced mechanism of the DPIIsystem.

A small footprint cholesteric liquid crystallaser

Andrii Varanytsia, TIANYI GUO, and Peter Palffy-Muhoray

Doc ID: 351964 Received 15 Nov 2018; Accepted 17 Dec 2018; Posted 18 Dec 2018  View: PDF

Abstract: We demonstrate a small optical bench footprint laser assembly based on the smallpulsed Nd:YAG laser head SSY-1 for pumping cholesteric liquid crystal (CLC) lasers andillustrate its performance using low molecular weight CLC samples doped with thefluorescent dye PM597. Low lasing threshold, narrow laser line and far field interferencepatterns of the CLC laser were observed using the SSY-1-based laser assembly as the pump.The emission characteristics of the CLC laser are similar to those observed with comparableCLC materials pumped by physically an order of magnitude larger and many orders ofmagnitude more expensive commercial Nd:YAG laser systems. The small footprint CLClaser demonstrated in this work provides an opportunity for significant size and cost reductionof CLC lasers and fostering their practical application.

Extension of the Matched Filter algorithm tomultiple guide star Shack-Hartmann wavefrontsensor

Piotr Piatrou

Doc ID: 345543 Received 11 Sep 2018; Accepted 17 Dec 2018; Posted 17 Dec 2018  View: PDF

Abstract: The Adaptive Optics (AO) systems with multiple Laser Guide Stars (LGS) maysignificantly benefit in terms of hardware simplification from merging several LGS opticalchannels into one with a single wavefront sensor. As Shack-Hartmann sensors typically sufferfrom incomplete filling of the camera area, there exists an opportunity to overlay several Hartmannspot patterns densely within a compact composite one resulting in very frugal use of the camerapixels. We show that such a pattern with only slight spot overlap can be composed even in a quiteextreme case of the Giant Magellan Telescope Laser Tomography AO (LTAO) system employingsix highly elongated side-launched laser beacons. The problem of disentangling the overlappedspots is efficiently solvable by a generalization of the Matched Filter (MF) algorithm, which is themain focus of this work. Dynamic calibration by the star dithering in case of extended MF is stillpossible albeit being more complicated. Computational complexity increase and performancedegradation in comparison to the classical Matched Filter can be minimized to acceptable valuesby careful system parameter tuning.

A plane chessboard-based calibration method forLWIR ultra-wide angle camera

chen yichao, Fuyu Huang, Fengming Shi, Bingqi Liu, and Hao Yu

Doc ID: 348507 Received 16 Oct 2018; Accepted 17 Dec 2018; Posted 19 Dec 2018  View: PDF

Abstract: A method is proposed to calibrate the long-wave infrared (LWIR) ultra-wide angle camera in this article. Besides, anovel calibration chessboard is designed and an advanced chessboard corner positioning method is adopted toimprove the calibration precision. The designed calibration chessboard can achieve high thermal infrared contrastand exhibits outstanding stability, which is made of thermoelectric semiconductor refrigeration device. Theproposed subpixel corner positioning method can accurately locate the corners on the calibration chessboardaccording to the characteristics of the infrared image and the checkerboard pattern. Both the principle of theproposed infrared chessboard and the subpixel corner positioning procedure were presented, and the calibrationexperiment show that the mean reprojection error (MRE) and the root mean square error (RMSE) were reduced to0.32 pixels and 0.39 pixels, respectively. Comparison studies were also performed to verify the calibration effect ofthe proposed method, and the possibilities of camera calibration error of the proposed method were analyzed.

Multi-polarization, Polarization-independence, WideangleRCS Reduction Metasurface Based on RandomPhase Gradients

Guoxiang Dong, Xiaoping Li, yanming liu, Shitao Zhu, Yuchen He, and Anxue Zhang

Doc ID: 349799 Received 31 Oct 2018; Accepted 15 Dec 2018; Posted 17 Dec 2018  View: PDF

Abstract: A novel metasurface based on random phase gradients is proposed for Radar cross section (RCS) reduction. In thiswork, wideband, polarization-independence and wide-angle RCS reduction is realized for both circularly polarized(CP) wave and linearly polarized (LP) wave, respectively. Thus, true polarization-independence RCS reduction isrealized by the proposed metasurface. This proposed metasurface is composed by different types of units, andthese units do not have certain period. Under both CP incidence and LP incidence, random phase gradients can beformed on the proposed metasurface. The incidence can be diffused because of these random phase gradients,resulting in multi-polarization, polarization-independence, wide-angle RCS reduction. The 10dB RCS reduction isranged from 12.6GHz to 17.0GHz, and18 GHz to 22 GHz for right hand circularly polarized (RHCP) incident wave,and it is ranged from 12.4GHz to 17.0 GHz, and 18.0GHz to 21.8GHz for left hand circularly polarized (LHCP)incident wave. Meanwhile, the 10dB RCS reduction is ranged from 12.0GHz to 17.0GHz for x-polarized incidentwave, and it is ranged from 13.0GHz to 17.0 GHz, and 17.6GHz to 21.8GHz for y-polarized incident wave. Both thesimulation and experimental results verify the value of this proposed metasurface in stealth technology.

Testing the surface quality of a reflective parabolic trough solarcollector with two flat null-screens

Manuel Campos-Garcia, Andrés Peña-Conzuelo, Oliver Huerta-Carranza, J. Rufino Diaz-Uribe, Ulises Edmundo Espinoza-Nava, and Victor Moreno-Oliva

Doc ID: 352274 Received 19 Nov 2018; Accepted 14 Dec 2018; Posted 17 Dec 2018  View: PDF

Abstract: In this work, we present a technique for quantitatively assessing the optical quality of a parabolic troughsolar collector. The presented method is an adaptation of the null-screen technology; a collection of processes thatretrieve information from the reflection of a known from the surface, and then use that information to reconstruct thesurfaces normal vectors. Via numerical simulations, it is shown that precision attainable to this method is up to0.068 mrad, depending of the source of systematical error, in this study we only consider displacements of thephysical null-screen as sources of error.

Rapid qualitative and quantitative analysis ofelemental composition of Cu(In, Ga)Se2 thin filmsusing laser induced breakdown spectroscopy

Junshan Xiu, Shiming liu, Shenggui Fu, Tao wang, Mingxing Meng, and yunyan liu

Doc ID: 345609 Received 11 Sep 2018; Accepted 14 Dec 2018; Posted 14 Dec 2018  View: PDF

Abstract: The composition of Cu, In, Ga and Se constituting the Cu(In, Ga)Se2 (CIGS) layer isimportant for the performance of the thin film. Laser induced breakdown spectroscopy (LIBS) isvery useful in quantitative analysis of elemental composition. In this paper, detection parametersof LIBS were optimized and the CIGS thin films deposited at different sputtering powers weredetected. LIBS results showed that intensity ratio (Ga/(ln+Ga)) of analytical spectral line of CIGSfilm increased initially then reduced with an increase of the sputtering power, and the evolutionwas consistent with optical band gaps calculated from the transmission spectra. The intensity ratiosof Ga/(ln+Ga) and Cu/(ln+Ga) detected were very highly correlated corresponding to the valueobtained from energy dispersive X-ray spectroscopy. All results indicate that it is available andfeasible of LIBS to fabricate high performance CIGS thin film using one-step radio frequency (RF)magnetron sputtering method.

High performance blue light detector based on ZnOnanowire arrys

Yanru Xie, Hefu Li, Dong Zhang, Qingru Wang, and Liqiang Zhang

Doc ID: 349148 Received 02 Nov 2018; Accepted 14 Dec 2018; Posted 07 Jan 2019  View: PDF

Abstract: Organic-inorganic hybrid heterojunctions are ever so promising for low cost and highefficient photoelectric devices. We report a p-n junction diode composed of inorganic ZnOnanowire arrays (ZNAs) and organic 2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-MeOTAD). A maximum photoresponsivity of 1.32 mA/W is observedunder illumination at zero bias. We also demonstrate that the photocurrent time response is observedto be rapid, consistent as well as repeatable. On blue light weak irradiance (410 nm, 75 μW/cm2),the rise time constant and decay time constant were found to be 0.12 and 0.06 s, respectively. Theseresults suggest ZNAs/spiro-MeOTAD heterojunction as a candidate for efficient self-powered bluelight detector.

A Compact, High Sensitivity Atomic MagnetometerUtilizing the Light-Narrowing Effect and In-PhaseExcitation

Yuhao Guo, shuangai wan, XiaoGuang Sun, and jie qin

Doc ID: 348304 Received 25 Oct 2018; Accepted 13 Dec 2018; Posted 14 Dec 2018  View: PDF

Abstract: The high sensitivity optically pumped atomic magnetometer working in the geomagnetic range utilizing the lightnarrowingeffect and in-phase excitation is described. The setup is based on a simple pump-probe arrangementbuild around a Cs vapour cell whose active volume is 64 mm3. The transverse oscillating field is applied parallel tothe probe beam to drive the Zeeman resonance, and the in-phase component of the resonance signal is measuredto determine the field. The sensitivity of the magnetometer is improved by pumping most atoms into the stretchedstate. Consequently, spin-exchange relaxation is suppressed, and a sensitivity of 0.1 pT/Hz1/2 in the range of 10 μTis achieved. This magnetometer has the advantages of large dynamic range, high performance of low-frequencystabilization, high response speed

OH PLIF Measurements with High Spatio-TemporalResolution for the Study of Auto-Ignition

Christoph Arndt and Wolfgang Meier

Doc ID: 347732 Received 10 Oct 2018; Accepted 13 Dec 2018; Posted 13 Dec 2018  View: PDF

Abstract: For the detailed understanding of transient combustion processes, in particular, of auto-ignition,quantitative measurements with high spatio-temporal resolution are desirable. These can, for instance, serve asvalidation data for time-resolved numerical simulations, and, in particular for the combustion models used inthose simulations. In the current study, the DLR Jet-in-Hot-Coflow Burner (DLR JHC) was used to inject aturbulent methane jet into the hot exhaust gas of a lean hydrogen/air flame and a steady state jet flame wasestablished. In addition, fuel could be injected in a transient manner. Here, an auto-igniting jet was observed.The flame stabilization of the steady state jet flame and the auto-ignition during transient fuel injection werestudied using high-speed laser-based and optical measurements. A strategy for quantifying high-speed OH planarlaser-induced fluorescence (PLIF) is presented and the measurement uncertainties are evaluated. The flamestabilization mechanism in steady state jet flames was assessed using probability density functions (PDFs) of theOH concentration at different axial and radial locations. The formation of auto-ignition kernels during transientfuel injection is evaluated based on time-series of the OH concentration. It is shown how the OH concentrationlevels and PDF shapes can be used to characterize the chemical state of the reacting flow and to distinguishbetween auto-ignition and flame propagation.

Experimental Investigation of a High Power 1018 nmFiber Laser Using 20/400 μm Ytterbium-Doped Fiber

Majid Lafouti, Hamid Latifi, Hosain Fathi, Saeid Ebrahimzadeh, Saeed Sarikhani, and hassan sarabi

Doc ID: 347665 Received 10 Oct 2018; Accepted 12 Dec 2018; Posted 13 Dec 2018  View: PDF

Abstract: A 472 W monolithic fiber laser operating at 1018 nm by employing a low core/cladding diameter ratio active fiber of20/400 μm is reported in this article in which the slope efficiency and beam quality factor (M2) are, respectively, 49.4%and 1.17. To realize the setup, the effects of the characteristics of the experimental elements- reflectivity of the outputcoupling fiber Bragg grating, length of the active fiber, etc. - over the output behavior of the system have beeninvestigated. This is the highest recorded output signal power, efficiency and beam quality factor in monolithic 1018 nmytterbium-doped fiber lasers using 20/400 μm core/cladding diameter ratio fibers.

High-efficiency, broadband, and wide-angle alldielectricquarter wave plate based on anisotropicelectric and magnetic dipole resonances

Jiaqi Yang and Tian Lan

Doc ID: 349298 Received 25 Oct 2018; Accepted 11 Dec 2018; Posted 11 Dec 2018  View: PDF

Abstract: Metadevices based on dielectric nanostructure with excitation of electric and magnetic resonances have shown highefficiency for polarization control compared with conventional manipulating methods as well as plasmonic structuremetadevices. Since both the electric and magnetic dipole resonances can be precisely adjusted by optimizing geometricparameters of the resonators to meet the desired wavelength, this paper proposes an approach to implement the hightransmittance metadevices operating at preferred wavelengths. By employing this method, we demonstrate an alldielectricquarter wave plate (QWP) metasurface with high transmittance (>85%) and high polarization conversionefficiency (>0.88) in a broad telecom waveband. At the same time, conversion efficiency is nearly unaffected for incidentangles within 75°. With features of high transmittance, wide-angle and invertible linear to circular polarizationconversion, the all dielectric QWP can be a good replacement for plasmonic metasurface devices and offers a furtherstep in developing polarization and phase manipulation metadevices.

Supernumerary bows: caustics of a refractive sphereand analysis of the relative overall Gouy phase shiftof the supernumerary rays

Paul Etienne Ouellette

Doc ID: 343112 Received 23 Aug 2018; Accepted 04 Dec 2018; Posted 05 Dec 2018  View: PDF

Abstract: The modified Young’s theory of interference related to the supernumerary rainbows is based on a differenceof 90 in the Gouy phase shifts for the parallel rays producing these bows. An observation screenplaced at a given distance from a refractive sphere illuminated by a point source of light should also showsupernumerary screenbows. An extensive description and analysis of the caustics involved is given. Forany k order, k being the number of reflections inside the sphere, a procedure is established to determinethe number of Gouy phase shifts encountered by any ray along its path from the source to the screen.Special consideration is given to the order k = 0. For any k supernumerary bow, on any spherical screenwhose center is that of the sphere, the difference in the Gouy phase shifts for the two rays producing abow always amounts to 90. An indirect proof of this characteristic is given. All considerations are madewithin the framework of geometrical optics being, on the one hand, the limit of the electromagnetic theoryas the wave length goes to 0, and being, on the other hand, complemented by the Gouy phase shifttheory.

Numerical simulation and experimentalverification of dense multi-view full-resolutionautostereoscopic 3D display based dynamicshutter parallax barrier

Yang Meng, Zhongyuan Yu, Chunyu Zhang, Ye Wang, Yumin Liu, Han Ye, and Laurence Chen

Doc ID: 345623 Received 12 Sep 2018; Accepted 03 Dec 2018; Posted 04 Dec 2018  View: PDF

Abstract: We come up with a practical setup and simulation for building up a glasslessautostereoscopic 3D display system based on the concept of “eye space” with dynamic shutterparallax barrier. “Eye space” is designed based on geometrical optics to get multi-view asmuch as possible through adjusting width of slit and parallax barrier dynamically. Thedynamic parallax barrier is placed in front of the display screen to form the shutter screen.The addressable drive circuit controls the switches of pupil windows on the shutter screen.The two signals are synchronous that drive circuit and frame frequency scanning of displayscreen. The shutter parallax barrier makes it possible that all right and left eyes in the “eyespace” see their own views simultaneously. The numerical simulation and experimentalverification with simplified 1D pupil windows and FPGA-based driving circuit unit arementioned in this paper, which have good practical value.

CIOMP-Study on low order aberrations measurements oflarge aperture flats based on scanning pentaprism

Er Qi, Haixiang Hu, and Xiao Luo

Doc ID: 336087 Received 03 Jul 2018; Accepted 23 Nov 2018; Posted 30 Nov 2018  View: PDF

Abstract: The PPS (pentaprism scanning technology) is an absolute testing method which has advantages of simple structure,absolute testing without extra reference flat, providing in-situ surface measurement, etc. It plays an important rolein the manufacturing process of large flat mirrors. For calibrating the PPS’s uncertainty, this paper developed amulti-mode scanning method to implement the measurement of low order aberrations and introduced a concept ofautocorrelation coefficient to evaluate the data processing progress. These improvements were applied to themeasurement of a large flat mirror (1630mm in diameter), which demonstrates the measuring uncertainty of PPScan be about 20nm rms. Furthermore, aimed at the special requirement of M3MP, which is the prototype mirror ofM3M (the tertiary mirror) in TMT (Thirty Meter Telescope) project and has an un-circular aperture, this paperanalyzed the slope distribution of low order aberrations, power and astigmatism. Then the sample route lines ofPPS are reorganized and new data process algorism is implemented. All these work were done to improve PPS’sperformance on measuring low order aberrations of large flat mirrors.

Detection of material zones on the surface of asteel-aluminium hybrid component using reflectionmodels and a monochromatic fringe projectionprofilometry system

Lorenz Quentin, Rüdiger Beermann, Markus Kaestner, and Eduard Reithmeier

Doc ID: 347051 Received 28 Sep 2018; Accepted 21 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: The limits of traditional lightweight engineering are being extended by the development of hybrid components.Lightweight potential is especially high when using dissimilar materials, e.g. a friction-weldedsteel-aluminium combination. An important factor for the mechanical properties of such a combinationis the geometry and location of the joining zone between the materials. The geometry of these objectscan be reconstructed by optical triangulation techniques like fringe projection profilometry. In this paper,we present a method to robustly detect the different material zones on the surface of an hybridsteel-aluminium component. We use reflection models and the data from a fringe projection profilometrysystem. The intensity values and the 3D geometry data from the fringe projection system are usedto estimate material-specific reflection parameters for each 3D point and detect different material areasbased on a global theshold.

Multicore optical fiber based vibration sensors for biomedical applications

Md Rejvi Kaysir and Md Jahirul Islam

Doc ID: 331662 Received 16 May 2018; Accepted 28 Jul 2018; Posted 30 Jul 2018  View: PDF

Abstract: Vibration is one of the key parameters for extracting information from surrounding environments, and optical fiber-based sensors show great promise for achieving such information. In this work, an intensity-based multicore fiber (MCF) based vibration sensor is designed, fabricated and characterized for biomedical applications. The fabricated MCF has seven cores, in which the middle core is used for launching light and the surrounding cores are used for collecting lights from any reflective substances. The working principle of the MCF sensor is based on the intensity modulation of reflected light from vibrating substances that is coupled to the collecting cores (i.e. side cores) of the MCF. Here, light from a 532 nm laser was launched into the middle core of the MCF and the reflected light from a mirror, situated at the output face of MCF, was collected from a single side core. To characterize the sensor and demonstrate the sensing activities of MCF, two experimental approaches were taken: (i) static sensitivity and (ii) dynamic measurements. The static measurement demonstrated the region of maximum sensitivity and helped to find out the optimal design parameters of MCF for any desired applications. A simple ray tracing model also included getting the maximum sensitive regions of the designed sensor that verifies our experimental results. Dynamic measurement demonstrates the vibration sensing activities of the sensor. This information provides pathways to design MCF based vibration sensors for the specific applications.

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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