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Efficient coupling to a waveguide by combinedgratingsin a holographic waveguide display system

Lanlan Yang, yan tu, Zaiyao Shi, Jingjing Guo, Lili Wang, Yuning Zhang, Xiaohua Li, and Baoping Wang

Doc ID: 345016 Received 05 Sep 2018; Accepted 14 Nov 2018; Posted 14 Nov 2018  View: PDF

Abstract: Gratings are widely used as coupling parts in a waveguide display system for achieving a much lighter andcompacter system, but their diffraction efficiency needs to be improved. Two combined-gratings for integratingsubwavelength binary grating and volume holographic grating(VHG) are applied as in-coupler and out-coupler of aholographic waveguide display system. Two basic design rules are put forward to guarantee the maximumdiffraction energy guided into the waveguide and finally coupled out to enter into the user’s eyes, one is the gratingvector matching rule, another is the refractive index matching rule on the interface of the binary grating and theVHG. Finite element method is used to simulate the couple-in parts and the whole waveguide display system. Thecombined-grating with metal binary grating is different from that with dielectric binary grating for achievinghigher diffraction efficiency and an additional second peak in the diffraction efficiency curve varied with therelative position between the binary grating and the VHG. The simulation results indicate that VHG+Ag combinedgratingcan obtain much higher diffraction efficiency compared to gold, aluminum and other dielectric materials. Inaddition, several factors such as the Bragg wavelength, the index modulation of VHG, the binary grating thickness,the filling factor of the binary grating are discussed for VHG+Ag combined-grating. Moreover, the higher diffractionefficiency in the holographic waveguide system can be obtained by using VHG+Ag-VHG+Ag combined-gratings asin-coupler and out-coupler.

Joint estimation of unknown radiometric data, gain andoffset from thermal images

Sahar Papini, Peretz Yafin, Iftach Klapp, and Nir Sochen

Doc ID: 340183 Received 18 Jul 2018; Accepted 13 Nov 2018; Posted 14 Nov 2018  View: PDF

Abstract: Low cost, weight and size microbolometer-based thermal focal plane arrays are attractive forthermal-imaging applications. Under environmental loads like in agricultural remote sensing thesecameras tend to suffer from drift in gain and offset with time and thus requires constant calibration. Ourgoal is to skip this step via computational imaging. In a previous work we estimated unknown offsetvalue and radiometric image of an object, given the calibrated gain, from a pair of successive imagestaken at two different blur levels, eliminating the need for offset calibration due to temperature variation.Here we extend our model to a case with unknown gain and offset. We show that these values as well asthe objects radiometric value can be found jointly, by minimizing a cost function, relying on N pairs ofblurred and sharp images. The method addresses both space-invariant and space-variant cases.Simulations show promising accuracy with error characterized by root mean squared error of less than 1.6°C.

High resolution 3-D light fluence mapping forheterogeneous scattering media by localizedsampling

Maxim Cherkashin, Carsten Brenner, and Martin Hofmann

Doc ID: 341294 Received 01 Aug 2018; Accepted 13 Nov 2018; Posted 14 Nov 2018  View: PDF

Abstract: We demonstrate an innovative concept for three-dimensional optical fluence mappingin heterogeneous highly scattering media as, for example, biomedical tissues. We propose touse relative light extinction analysis principle together with a miniaturized collection fiber ina direct fluence measurement setup as a method to obtain the spatially resolved light intensitydistribution under transversally-inhomogeneous light propagation conditions and provide thelocal characterization of the transport medium. The system performance is validated in twoextreme conditions: an optically thin scattering medium and an absorption-dominated lighttransport. Both extremes demonstrate good agreement to theoretical expectations. Finally, wesuccessfully prove the ability of the system to deliver high resolution fluence maps through amodel study of the light distribution induced in a scattering medium by a vertical diode-laser barstack with individual bars pitched only 500 μm apart.

Study of morphological feature andmechanism of KDP surface damage under351nm nanosecond laser

Zhichao Liu, Geng Feng, Yaguo Li, Jian Cheng, Hao Yang, yi zheng, Jian Wang, and Qiao Xu

Doc ID: 346215 Received 19 Sep 2018; Accepted 13 Nov 2018; Posted 14 Nov 2018  View: PDF

Abstract: The surface damage morphology of KDP crystal under 351nm nanosecond laserirradiation is studied and the formation mechanism of each damage type are discussed. Thereare three unique types of KDP surface damage, crack, shell and crater, under the fluencebetween 5J/cm2 and 15J/cm2. The fracture feature of crack type damage indicates the puremechanic process during laser exposure. Some cracks result in the upwarp of the materialwith height of 0.1μm~0.5μm. The shell is a most typical damage morphology with aproportion as large as about 80%. The transverse size of shell ranges from 5μm to 82μm,related to the fluence. The crater has a distinguish core structure related to high-temperatureprocess. The evidence of dehydration reaction is found in the core by EDS semi-quantitativeanalysis. Internal morphology analysis with FIB suggests that the crack and shell damageoriginate from the surface or sub-surface machining defects, while the crater damage ismainly due to the material bulk defects.

Generation of optical vortex array in the course ofacousto-optic diffraction

Yuriy Vasylkiv, Iryna Martynyuk-Lototska, Ihor Skab, and Rostyslav Vlokh

Doc ID: 346952 Received 27 Sep 2018; Accepted 13 Nov 2018; Posted 14 Nov 2018  View: PDF

Abstract: Generation of an array of optical vortices (OVs) with fractional charges under the conditions of acousto-opticBragg diffraction is revealed experimentally. The OVs emerge in a wide diffracted optical beam due toreflection from a thick acousto-optic grating that contains bifurcated fringes of acoustic waves. Changes in theacoustic-wave frequency lead to deflection of the wide optical beam containing the OV array. The OVs preservetheir spatial positions only in the narrow AW frequency range, while larger changes in the frequency imposestheir movement out from the beam aperture, with appearance of the other OVs in the other places of the beamcross section.

Fiber optic surface plasmon resonance based highlysensitive arsenic sensor prepared using α-Fe2O3/SnO2core-shell nanostructure with optimized probeparameters

Sonika Sharma and Banshi Gupta

Doc ID: 347974 Received 10 Oct 2018; Accepted 13 Nov 2018; Posted 14 Nov 2018  View: PDF

Abstract: A novel SPR based fiber optic arsenic, As (III), sensor is presented using α-Fe2O3/SnO2 core-shell nanostructure(abbreviated as (α-Fe/Sn) CS) synthesized using hydrolysis. Due to extraordinary properties such as very largesurface area, great adsorption capabilities and chemical reactivity, α-Fe2O3 NPs offer excellent sensitivity andselectivity for As (III), while SnO2 shows great catalytic properties. To achieve the best sensing performance, (α-Fe/Sn) CS is synthesized at different temperatures and its morphological study is carried out using transmissionelectron microscopy. The performance of the probe fabricated over silver coated unclad core of the fiber withoptimized fabrication temperature and attachment time of (α-Fe/Sn) CS is investigated for 0 μg/L to 100 μg/Lconcentration of As (III). The sensor possesses limit of detection of 0.47 μg/L. Further, the roles of commoninterferands in sensor performance are investigated. The sensor possesses the advantages of real timedetection, capability of remote sensing and online monitoring which uphold its industrial application.

Multi-pass amplifiers with self-compensation of the thermal lens

Karsten Schuhmann, Klaus Kirch, Miroslaw Marszalek, Francois Nez, Randolf Pohl, Ivo Schulthess, Laura Sinkunaite, Gunther Wichmann, Manuel Zeyen, and Aldo Antognini

Doc ID: 348504 Received 16 Oct 2018; Accepted 13 Nov 2018; Posted 14 Nov 2018  View: PDF

Abstract: We present an architecture for a multi-pass amplifier based on a succession of optical Fourier transformsand short propagations that shows a superior stability for variations of the thermal lens compared to stateof-the-art 4f-based amplifiers. We found that the proposed multi-pass amplifier is robust to variations ofthe active medium dioptric power. The superiority of the proposed architecture is demonstrated by analyzingthe variations of the size and divergence of the output beam in form of a Taylor expansion aroundthe design value for variations of the thermal lens in the active medium. The dependence of the outputbeam divergence and size is investigated also for variations of the number of passes, for aperture effectsin the active medium and as a function of the size of the beam on the active medium. This architecturemakes efficient use of the transverse beam filtering inherent in the active medium to deliver a beam withexcellent quality (TEM00).

Polarization-Sensitive Beam Steering fromQuantum Emitters Coupled with BirefringentMetamaterials

Young-Bin Kim, Dae-Woong Hwang, Yoon-Jong Moon, and Sun-Kyung Kim

Doc ID: 347990 Received 11 Oct 2018; Accepted 12 Nov 2018; Posted 13 Nov 2018  View: PDF

Abstract: One-dimensional metal/dielectric subwavelength periodic patterns have dielectric or metallic material dispersionsdepending on the polarization of incident light. This feature enables the development of artificial, ultrathin,birefringent films. In this study, we report polarization-sensitive beam steering from quantum emitters coupledwith one-dimensional metal/dielectric metamaterial films. Electromagnetic simulations show that an Al/ITOmetamaterial film functioning as a quarter-wave plate leads to vertically directed radiation for one polarizationand a saddle-shaped, diverging radiation pattern for the orthogonal polarization. The strategy studied herein isextended to achieve polarized, vertically directed emission from organic light-emitting diodes. A tailored Al/ITOmetamaterial mirror yields an approximately 30-fold improvement in polarization ratio, in conjunction withpolarization-dependent Purcell factor enhancement.

Progress in virtual reality and augmentedreality based on holographic display

Zehao He, Xiaomeng Sui, Guofan Jin, and Liangcai Cao

Doc ID: 347102 Received 01 Oct 2018; Accepted 12 Nov 2018; Posted 14 Nov 2018  View: PDF

Abstract: The past, present and industry prospect of virtual reality (VR) and augmentedreality (AR) are presented. The future of VR/AR technology based holographic display ispredicted by analogy with the VR/AR based on binocular vision display and light fielddisplay. The investigations on holographic display which can be used in VR/AR arereviewed. The breakthroughs of holographic display are promising in VR/AR with highresolution. The challenge faced by VR/AR based on holographic display are analyzed.

Wide Tuning Range and High OSNR Self-SeededMulti-Wavelength Brillouin-Erbium Fiber LaserBased on Lyot Filter

Qi Zhao, Li Pei, Liangying Wu, Tigang NIng, Jingjing Zheng, and Jing Li

Doc ID: 347131 Received 01 Oct 2018; Accepted 12 Nov 2018; Posted 14 Nov 2018  View: PDF

Abstract: A tunable self-seeded multi-wavelength Brillouin-erbium fiber laser (BEFL) based on Lyot filter is experimentallydemonstrated in this paper. The Lyot filter is constructed by a polarization dependent isolator (PDI), two polarizationcontrollers (PCs) and a 20-cm-length polarization maintaining fiber (PMF). In this proposed structure, the PDI is used asa polarizer. Due to the periodic filtering characteristics of the Lyot filter, the multi-wavelength output of the laser showsdifferent Brillouin bands by adjusting the PCs. In the experiment, the single Brillouin band can be produced with thetuning range of 30 nm, from 1527.8 nm to 1557.8 nm. The optical signal-to-noise ratio (OSNR) of the output wavelengthsis ~20 dB. Daul Brillouin bands are observed.

Multi-population Genetic Algorithm for Peak-toaveragePower Ratio Suppression in Optical OFDMTransmission System

Yang Ye, Mingyi Gao, Yuanyuan Ma, Weidong Shao, Wei Chen, yonghu yan, and Hongliang Ren

Doc ID: 345830 Received 19 Sep 2018; Accepted 12 Nov 2018; Posted 14 Nov 2018  View: PDF

Abstract: We proposed and experimentally demonstrated the parallel multi-population genetic algorithm (MPGA)-basedselected mapping (SLM) technique to reduce the peak-to-average power ratio (PAPR) of optical orthogonalfrequency division multiplexing (OFDM) system. By introducing the parallel genetic algorithm (GA), the MPGA-SLMcan effectively escape the local optimization of the conventional GA and attains fast convergence on the globaloptimization. Compared with the conventional SLM method, we experimentally achieved 1-dB performanceimprovement at 3.8×10-3 BER by utilizing the MPGA-SLM in the back-to-back case and that of 0.7 dB in the 30-kmsingle mode fiber transmission case.

“Giant” quantum dots encapsulated insidefreeform lens

Hongyu Yang, Bo Huang, Lei Zhang, Yufen Yuan, Wenbin Xiang, Yiping Cui, and Jiayu Zhang

Doc ID: 342809 Received 03 Sep 2018; Accepted 12 Nov 2018; Posted 13 Nov 2018  View: PDF

Abstract: Freeform lens containing giant red and green quantum dots (QDs) were designedto be used for direct illumination-type LED backlight wide-color-gamut display.Encapsulating with the freeform lens could not only expand the illumination area, where theuniform lighting area was about 2cm in radius on the plane 1.5cm above the LED, but alsoavoid QDs to contact directly with the LEDs chip, which could reduce the QD’s surroundingtemperature from 94 to 61. Moreover, this encapsulation and the thick shell of QDs couldsignificantly improve the device’s lifetime up to more than 100h due to reduced temperature.A color gamut of ~130% NTSC standard could be obtained with the freeform lens.

THz imaging of inhomogeneous polymer multilayers: theory and experiment

Cyndie Poulin, Myriam Zerrad, Meriam Triki, Antoine Guille, Thierry Antonini, and Claude Amra

Doc ID: 342921 Received 21 Aug 2018; Accepted 12 Nov 2018; Posted 13 Nov 2018  View: PDF

Abstract: We extend an interferential multilayer model used in Optics in the terahertz domain to be able to simulate the mapping of the transmissivity of a multilayer structure of polymers. In particular, we are interested to extract the thickness gradient of a glue layer within an assembly of polymers. We developed an iterative procedure which we validated by THz imaging.

Detection of Dynamic Signals from Multiplexed SOAbasedFiber-Ring Laser Sensors

Rong Chen, Chuanyi Tao, Xuhai Jiang, Junhua Cheng, Jing Zhang, Liming Mao, Na Li, and Xiangkai Zeng

Doc ID: 345322 Received 07 Sep 2018; Accepted 12 Nov 2018; Posted 13 Nov 2018  View: PDF

Abstract: A simple matched filter demodulation configuration for detecting dynamic signals from multiplexed semiconductor opticalamplifier (SOA)-based fiber-ring laser sensors is investigated theoretically and experimentally. It is feasible for multiple points FBGsensing because the inhomogeneous broadening of the SOA source makes it possible to produce multimode lasing without modecompetition. The best operating point for matched filter demodulation and the wavelength demodulation range are investigated. In theexperiment, the simultaneous dual-channel detection of dynamic strains at high frequencies is presented by using piezoelectrictransducers. An example application for simultaneous two-channel ultrasonic detection has been successfully demonstrated. Thedetection system design is simple, low cost and high precision, making it attractive for applications in structure health monitoring.

In vivo hemodynamic visualization of berberineinducedeffect on mouse cerebral cortex byphotoacoustic tomography

DAN WU, Xiuyun Guo, Ruihuan Cui, Man Wu, Qiquan Shang, and Huabei Jiang

Doc ID: 345865 Received 17 Sep 2018; Accepted 12 Nov 2018; Posted 13 Nov 2018  View: PDF

Abstract: While berberine, a traditional Oriental herbal drug commonly used for treatment of diarrhea, has recently beenused to treat a number of brain disorders such as stroke and Alzheimer’s disease, berberine-induced changes inhemodynamics are largely unknown. Here we utilize photoacoustic tomography (PAT) to study hemodynamiceffects of berberine in mice. In vivo photoacoustic images are obtained in ten functional regions of mouse brain.Cortical vascular network and dynamic changes in total hemoglobin (HbT) concentration are acquired at 532 nm.Functional atlas and statistical data arealso obtained at low-dose and high-dose berberine. Our results providecompelling evidence that both low-dose and high-dose berberine can increase the HbT concentration to variedextent in certain brain regions. This study also suggests that PAT provides a powerful tool for visualizing brainhemodynamic changes induced by drugs.

General model for phase shifting profilometry with object in motion

Lei Lu, Yongkai Yin, Zhilong Su, Xiaozhen Ren, Yinsen Luan, and Jiangtao Xi

Doc ID: 345465 Received 10 Sep 2018; Accepted 11 Nov 2018; Posted 13 Nov 2018  View: PDF

Abstract: When implementing the phase shifting profilometry to reconstruct the object, the object is always required to be kept stable as multiple fringe patterns are required. Movement during the measurement will cause fail reconstruction. This paper proposes a general model describing the fringe patterns with any three-dimensional movement based on Phase shifting profiloemtry. The object movement is classified as five types and their characteristics are analyzed respectively. Then, by introducing a virtual plane, the influence on the phase value caused by different types of movement is described mathematically and a new model including movement information is proposed. At last, with the help of the movement tracking and least-square algorithm, the moving object is reconstructed with high accuracy. The proposed method can remove the reference plane during the reconstruction of the moving object, which extends the application range of the phase shifting profilometry. The effectiveness of the proposed is verified by the experiments.

Comparative study of sampling Moiré and windowedFourier transform techniques for demodulation of asingle fringe pattern

Shien Ri, Nimisha Agarwal, Qinghua Wang, and Kemao Qian

Doc ID: 343069 Received 23 Aug 2018; Accepted 11 Nov 2018; Posted 13 Nov 2018  View: PDF

Abstract: Phase measurement techniques using a single-shot carrier fringe pattern play an important role in optical scienceand technology and have been widely used for various applications. In this paper, we focus on the comparativestudy of two major fringe analysis techniques, the sampling Moiré (SM) and the windowed Fourier transform(WFT). While SM converts a single fringe pattern to multiple phase-shifted Moiré fringe patterns to extract thephase information in the spatial domain, WFT obtains the phase information in the windowed Fourier domain;thus two methods look entirely different. We evaluate the phase extraction errors of SM and windowed Fourierridges (WFR) as a typical WFT method for both linear and nonlinear phases with/without noise against thereference Fourier transform (FT) technique. For the simulated fringe patterns with linear or nonlinear phase anddifferent random noise level, all the methods have high phase extraction accuracies. For a real experiment withmore complicated phase and discontinuities, SM and WFR, both being local methods, yields quite similar resultsand outperform FT.

Spatio-temporal and spatio-spectral metrologyof terahertz broadband uniformly topologicallycharged vortex beams

Maksim Kulya, Varvara Semenova, Andrei Gorodetsky, Victor Bespalov, and Nikolai Petrov

Doc ID: 345661 Received 17 Sep 2018; Accepted 10 Nov 2018; Posted 13 Nov 2018  View: PDF

Abstract: A comprehensive characterization of the diffraction properties of terahertz (THz)pulsed broadband vortex beams consisting of several electromagnetic field oscillations requiresstate-of-the-art techniques for studying the evolution of a wavefront as it propagates. For thispurpose, we have applied the capabilities offered by the THz Pulse Time Domain Holography(PTDH). Accurate metrological study of pulsed single-period THz fields propagation allowed usto reveal the spatio-temporal and spatio-spectral couplings in Broadband Uniform TopologicallyCharged (BUTCH) vortex beams. Here, we reveal the dynamics of not only such beam free-spacepropagation, but also in the experiment with edge diffraction, blocking 50% of the beam focalwaist. Despite the fact that in the amplitude representation one can observe the emergence ofstrong asymmetry, the analysis of the spectral trajectory of the singular point at some distancefrom the obstacle and the visualization of phase distribution for individual spectral componentstestify the conservation of transverse energy circulation (TEC). Similarly to the edge diffraction ofmonochromatic optical vortices, it can be interpreted as self-reconstruction of vortex properties.Given term has not previously been used to the case of pulsed broadband THz beams.

Effect of the surface roughness on theefficiency of diffractive optical elements

Lidong Zhao, Qingfeng Cui, and Yang Hu

Doc ID: 346754 Received 25 Sep 2018; Accepted 09 Nov 2018; Posted 13 Nov 2018  View: PDF

Abstract: The proposed study aims to investigate the effect of surface roughness, on theefficiency of diffractive optical elements (DOEs) used in imaging optical systems. Amathematical model describing the influence of surface roughness on the diffractionefficiency and polychromatic integral diffraction efficiency (PIDE) is presented and its effectsare analysed and simulated. Examples of single-layer diffractive optical elements (SLDOEs)containing PMMA substrate and multi-layer diffractive optical elements (MLDOEs)composed of a combination of PMMA and POLYCARB substrates for each layer used in thevisible region are analysed. The results can be used to analyse the effects of surface roughnesson the diffraction efficiency and PIDE of DOEs.

Double Random Phase Encoding for Cancelable Face and IrisRecognition

Randa Soliman, Ghada EL Banby, Abeer Algarni, Mohamed Elsheikh, Naglaa Soliman, mohamed amin, and Fathi Abd El-Samie

Doc ID: 334851 Received 17 Sep 2018; Accepted 09 Nov 2018; Posted 09 Nov 2018  View: PDF

Abstract: Most modern security systems depend on biometrics. Unfortunately, these systems have suffered for a long time from hacking trials.If the biometric databases have been hacked and stolen, the biometrics saved in these databases will be lost forever. Thus, there is abad need to develop new cancelable biometric systems. The basic concept of cancelable biometrics is to use another version of theoriginal biometric template created through a 1-way transform or an encryption scheme to keep the original biometrics safe andaway from utilization in the system. In this paper, the optical Double Random Phase Encoding (DRPE) algorithm is utilized forcancelable face and iris recognition systems. In the proposed cancelable face recognition scheme, the Scale Invariant FeatureTransform (SIFT) is used for feature extraction from the face images. The extracted feature map is encrypted with the DRPEalgorithm. On the other hand, the proposed cancelable iris recognition system depends on the utilization of two iris images for thesame person. Features are extracted from both images. The features extracted from one of the iris images are encrypted with theDRPE algorithm provided that the second phase mask used in the DRPE is generated from the other iris image features. This trendguarantees some sort of feature fusion between the two iris images into a single cancelable iris code and increases privacy of users.Simulation results show a good performance of the two proposed cancelable biometric schemes even in the presence of noise,especially with the proposed cancelable face recognition scheme.

Design of a built-in baffle for a Ritchey-Chretienoptical system

Lin Sun, Qingfeng Cui, Na Xie, and Jingfeng Wang

Doc ID: 345008 Received 04 Sep 2018; Accepted 09 Nov 2018; Posted 09 Nov 2018  View: PDF

Abstract: A baffle effectively prevents direct rays of stray light from entering an optical system.Existing design methods can result in very long outer baffle lengths, increasing the weight and volumeof the optical system, or large secondary mirror baffle sizes, increasing the central obscuration andresulting in the reduction of the illumination beam on the image. To overcome these challenges, adesign method for a built-in baffle is presented. The designed built-in baffle for a typicalRitchey-Chretien optical system is compared with a conventionally designed baffle. For the first case,the length of outer baffle is shortened from 3456 mm to 49.9 mm, the MTF can increase from 0.361to 0.421. And in another case, the outer baffle length is shortened from 3456 mm to 1924.2 mm, theMTF can increase from 0.361 to 0.408. Meanwhile, the stray light suppression capability is close to thetraditional method.

Multichannel Continuous-wave Fiber Cavity Ringdown GasSensing Utilizing Frequency-shifted Interferometry

Zhangyong Yang, Chunfu Cheng, Hui Lv, Zehao Chen, Jiaxuan Chen, and Yiwen Ou

Doc ID: 345720 Received 14 Sep 2018; Accepted 08 Nov 2018; Posted 09 Nov 2018  View: PDF

Abstract: We present a multichannel continuous-wave (CW) fiber cavity ringdown (FCRD) gas sensing methodbased on frequency-shifted interferometry (FSI). This scheme detects gas concentration by measuring theintensity decay rates of continuous light from different ringdown cavities (RDCs) in the spatial domain, unlikeconventional FCRD techniques by measuring the decay rates of pulse light in the time domain. It shares one CWlight source, one slow detector and one slow data collector. In order to illustrate the theory, acetylene gasconcentration measurement in a two-channel FSI-FCRD system was experimentally conducted in the range of0–1%. A linear relation was established between concentration and absorption loss which is proportional to theintensity decay rate, and the measurement resolution of 3.871%/dB and 3.658 %/dB were achieved respectively.The results reveal that the proposed system has the advantages of low cost, high sensitivity, high precision andgood stability in multichannel gas detection.

Flexible Ultra-Wideband Microwave Metamaterial Absorber with Multiple Perfect Absorption Peaks Based on the Split Square Ring

Yunpeng Liu, Binzhen Zhang, Junping Duan, and yongqing Xu

Doc ID: 342041 Received 28 Aug 2018; Accepted 08 Nov 2018; Posted 09 Nov 2018  View: PDF

Abstract: In this paper, a flexible ultra-wideband metamaterial absorber (MMA) with multiple perfect absorbing pecks has been proposed and investigated. In this design, we choose the rubber as the dielectric layer to achieve the fliexiblilty, select the opening square ring to reach the multiple perfect absorbing pecks. For the simulation results, the three layers absorber that reaches 90% absorptivity has achieved from 3.87GHz to 10.84GHz. Then, we propose a five layers absorber for easy facilitate, whose abosrptivity reaching 90% has achieved from 3.78GHz to 9.85GHz and the absorption peak has reached 99.99%, 100%, 100%, 99.99% at 4GHz, 5.82GHz, 8.46GHz, 9.71GHz respectively.

Quantification of Cerebral Vascular Perfusion Density via Optical Coherence Tomography based on Locally Adaptive Regional Growth

Jian Liu, Ning Ding, Yao Yu, Yushu Ma, XINCHENG YUAN, Yi Wang, Yuqian Zhao, Jingmin Luan, and Zenhe Ma

Doc ID: 341136 Received 30 Jul 2018; Accepted 07 Nov 2018; Posted 08 Nov 2018  View: PDF

Abstract: Optical coherence tomography (OCT) angiography is a non-invasive imaging modality that produces volumetric views of blood flow perfusion in vivo with resolution at capillary level, which has been widely adopted to monitor cerebral perfusion status after stroke in experimental settings. Accurate quantification of cerebral perfusion from OCT angiograms is important for understanding the cerebral vascular pathophysiology and assessing the treatment of ischemic stroke. Quantification of blood vessels from OCT angiography faces some problems, one is uneven illumination (which causes some blood vessels to be very bright, some is very dark), and the other is that the brightness in the same blood vessel also changes due to the difference in diameter or depth. In this paper, we proposed a locally adaptive region growing algorithm to solve this problem. The algorithm, which confines the region growing process to a local region, is used to segment blood vessels in different images to cope well with the intensity changes in blood vessels. During segmentation, the initial seed pixels were selected with the aid of the Otsu algorithm, the growth criterion considered both global and local information, and the thresholds were also adjusted adaptively as local regions varied. After these processes are completed, we can calculate the percentage of "pixels of the segmented blood vessels" as a "entire blood vessels" in the image, named cerebral vascular perfusion density (CVPD), and use it as an indicator to evaluate the cerebral blood perfusion of MCAO mice. Finally, the confirmation results given by magnetic resonance imaging (MRI) indicated a good agreement between the CVPD and the degree of cerebral infarction. This paper demonstrates that the algorithm can produce satisfactory vescular segmentation results, and CVPD can be used as an effective indicator for evaluating post-ischemic injury.

Highly Sensitive Fiber Bragg Grating Based PressureSensor using Side-hole Packaging

Suneetha Sebastian, Sridhar S, Shivaprasad P, and Sundarrajan Asokan

Doc ID: 343102 Received 06 Sep 2018; Accepted 07 Nov 2018; Posted 08 Nov 2018  View: PDF

Abstract: In this work, an analysis of pressure response of Fiber Bragg Grating (FBG) sensor in side-hole package has beenpresented using finite element method. Various parameters of the side-hole packaging such as hole radius; thedistance of separation between them; the radius and length of the package and the choice of the package materialare considered and optimized in order to promote maximum pressure sensitivity of FBG sensor. This investigationon optimization of the side–hole package parameters gives rise to pressure sensitivity of nearly 105 times ascompared with the bare FBG sensor, with the numerical values of 3 pm/MPa for a bare FBG sensor, to ~2,80,000pm/MPa for optimized side–hole package FBG sensor. Such a high-pressure sensitivity of FBG sensor is beingreported for the very first time in this work and can be considered as the initial step towards the realization ofhighly sensitive hydrophone based on FBG, for sensing underwater acoustic signals.

Multiple Gamma value based phase error compensation method for phase measuring profilometry

Shaoyan Gai, Feipeng Da, and CHAO LIU

Doc ID: 344625 Received 31 Aug 2018; Accepted 07 Nov 2018; Posted 08 Nov 2018  View: PDF

Abstract: 3D measurement based on fringe projection has been widely used. However, the Gamma nonlinearity and system nonlinearities usually result in significant phase error. Furthermore, there are various Gamma values due to the non-uniform brightness distribution of projector and the nonlinear factors of system, which makes the problem more complicated. To solve this problem, a sub-area compensation method based on multiple Gamma value is proposed. In the beginning, a uniform image is projected on a standard whiteboard with smooth surface. The obtained image is partitioned by using histogram statistics. Then different phase error model for different region is established. Finally, phase error is compensated according to the regions. By applying this method, the accuracy of the phase algorithm is greatly improved. The method is simple and convenient compared with the existing methods.

Radiometric temperature measurement by incoherent digital holography

Masatoshi Imbe

Doc ID: 345306 Received 07 Sep 2018; Accepted 07 Nov 2018; Posted 08 Nov 2018  View: PDF

Abstract: This study aims to demonstrate radiometric temperature measurement using incoherent digital holography. Since in-focus images of thermal radiations can be reconstructed at any distance, three-dimensional radiometric temperature can be measured. This requires an optical configuration with a fixed magnification to record an incoherent hologram that contains information about the spectral radiance of an object. The derivation of spectral radiance from the intensity signal of a reconstructed image is described, in addition to the calibration procedures correlating the holographic signal to the radiation temperature. The experimental results and possible sources of uncertainty are discussed.

Mode detection of misaligned orbital angularmomentum beams based on convolutionalneural network

Qingsong Zhao, Shiqi Hao, Yong Wang, Lei Wang, Xiongfeng Wan, and Chenlu Xu

Doc ID: 345814 Received 13 Sep 2018; Accepted 07 Nov 2018; Posted 08 Nov 2018  View: PDF

Abstract: The utilizing of the beam carrying orbital angular momentum(OAM) for free spaceoptical(FSO) communication can increase channel capacity. However, the misalignment ofthe beam is an effect that must be mitigated in FSO communication systems. Due to therobustness of deep learning technology in pattern recognition, a neural network structure isproposed and improved to mitigate the effect of misalignment error. Firstly, compared with asimple convolutional neural network(CNN) proposed, the data augmentation is adopted in thetraining. Then, a view-pooling layer is added after the convolutional layer. This layer canlongitudinally compress feature maps from multiple receive angles. In order to verify theperformance of the proposed method, related experiments are conducted in this paper. It canbe seen from the results that when the tilt angle is less than 35°, the accuracy of OAM modedetection is above 99%, 93%, and 88%, respectively, corresponding to the condition of weak( 2 1 10 15 2/3 nC = × − m− ), medium ( 2 1 10 14 2/3 nC = × − m− ) and strong ( 2 1 10 13 2/3 nC = × − m− ) turbulence.

2-μm double pulse single frequency Tm:fiber laserpumped Ho:YLF laser for a spaceborne CO2 lidar

Fabien Gibert, Jessica Pellegrino, Dimitri EDOUART, Claire Cénac, Laurent Lombard, Julien Le Gouët, Thierry Nuns, Alberto Cosentino, Paolo Spano, and Giorgia Di Nepi

Doc ID: 347427 Received 03 Oct 2018; Accepted 07 Nov 2018; Posted 08 Nov 2018  View: PDF

Abstract: In the framework of spaceborne CO2 Lidar development, the transmitter is a critical unit. We report on thedevelopment and the assessment of performances of a 2-μm single frequency Thulium fiber laser pumped QswitchedHo:YLF laser. To fulfill the requirements of space-based operation a master oscillator power amplifier(MOPA) architecture has been chosen and the oscillator works in double pulse operation. The transmitter cangenerate a single mode dual wavelength emission “ON” and “OFF” around the R30e line of the 20013←00001 bandof 12CO2. It delivers a pair of OFF-ON pulses with 12 mJ and 42 mJ energy respectively at a pulse repetitionfrequency of 303.5 Hz. The pulse energy and central frequency stabilities are especially documented as well aspulse duration, polarization, overall efficiency, beam quality, pointing stability and spectral purity. The possiblelimitations by light induced damage or radiation induced attenuation on the laser performances are also evaluated.

Ultra-precision fabrication of nikel phosphorouslayer on aluminium substrate by SPDT and MRF

Yang Bai, Zhiyu Zhang, Xue Donglin, and Xuejun Zhang

Doc ID: 336408 Received 03 Jul 2018; Accepted 07 Nov 2018; Posted 09 Nov 2018  View: PDF

Abstract: The metal mirrors are rarely used in visible or ultraviolet system due to the ultra-precision fabrication difficulties. Inthis work, a plane aluminium alloy substrate (Φ100mm) surface deposited with nikel-phosphorous (NiP) layer byelectroless deposition technique is prepared. The NiP layer is processed by SPDT (single point diamond turning)technology to the accuracy of 60nm in RMS and surface roughness reaches 4.157 nm in Ra. A kind of water basedmagnetorheological polishing fluid for the ultra-precision of NiP layer is developed and MRF (magnetorheologicalfinishing) is applied to the final finishing of the mirror. The developed fluid that contains small size (1.5μm) carbonyliron powder and 50 nm nano-cerium possesses the material removal of 1.8μm/min and surface roughness of 1nm isdetermined as the optimal fluid formula. The surface residual error is improved from 60nm to 10nm and surfaceroughness decreases from 4.157nm to 0.851nm after MRF in 1.5 hours with one polishing cycle with the developedMR polishing fluid. Finally, the surface quality after MRF is tested by SEM and XRD and the results manifest thatthe periodical tool mark is swiped out and the surface is not contaminated by MR polishing fluid. The experimentresults and theoretical analysis of this work prove that MRF can satisfy the ultra-precision fabrication of NiP film on metalmirror and the surface quality can be applied in visible or even ultraviolet optical system by using suitable MR polishing fluids.

General equations for the null-screen test foraspherical surfaces with deformation coefficients

Daniel Aguirre, Manuel Campos-Garcia, J. Rufino Diaz-Uribe, and Brenda Villalobos-Mendoza

Doc ID: 342703 Received 20 Aug 2018; Accepted 06 Nov 2018; Posted 06 Nov 2018  View: PDF

Abstract: A modified approach to calculate the null-screen for testing fast convex/concave aspherical surfaces withdeformation coefficients is presented. Introducing the aberration polynomial into the equation of the sagitta, thenull-screens can be generated in a simple way, in contrast to the conventional design method. This approach is easyto implement for the calculation of the null-screen since the equations presented here are easy to programcomputationally. The validation of this approach was done by analyzing the fast aspherical surface of a convexcondenser lens (f/0.18). We obtained a percentage error smaller than 1.3% in the recovery of the coefficients thatdescribe the shape of the surface.

Fatigue Characteristics of Deformable MirrorsCaused by Fatigue of PZT

Jiaqiu Wang, Shuai Luo, Fang Ling, Zheqiang Zhong, and Bin Zhang

Doc ID: 340726 Received 26 Jul 2018; Accepted 06 Nov 2018; Posted 06 Nov 2018  View: PDF

Abstract: The correction ability of deformable mirrors (DMs) with different fatigued degreeshas been studied by analyzing quantitatively the fitting wavefront, the times-diffraction-limitfactor β, as well as the wavefront power spectral density (PSD). The results indicate that thefatigue of DMs can be ignored when the DM continually works below for 105 cycles, whilethe performance of the DM degrades gradually if the loading cycles of the DMs exceed 105.Consequently, the peak-valley (PV) value of the fitting wavefront of the DM decreases withthe increasing of the fatigue degree of the DM, resulting in the increasing of the PV value ofthe corresponding residual wavefront. Meanwhile, the larger PV value of the distortedwavefront or the higher proportion of the high spatial frequency components gives rise to thelarger residual wavefront after the existence of the fatigue of PZT actuators, the worsecorrected beam quality and the lower the correction ability of the DM. The correction abilityof the DM composed of different piezoelectric ceramics has also been evaluated by β factorof the corrected laser beam, which indicates that for the given working cycle, both the fatiguedegree and the correcting ability of the DM composed of different piezoelectric ceramics aredifferent.

Investigating surface morphology of Ag-AgClthin film by scattering pattern at normal andoblique incident

Razieh Talebi and Sepideh Izadi

Doc ID: 344854 Received 05 Sep 2018; Accepted 06 Nov 2018; Posted 06 Nov 2018  View: PDF

Abstract: We study the formation of periodic nanostructures on Ag-AgCl thin films byirradiating s-polarized laser beams at different incident angles. A theoretical model isproposed to describe the formation of the structures based on interference of incident beamand TE0 mode propagating in AgCl slab waveguide. The line-space of periodic nanostructureson Ag-AgCl thin film can be manipulated by changing the incident angle and wavelength oflaser beam. The scattering and diffraction pattern of periodic nanostructure during laserirradiation, gives useful information about the surface morphology of the structure. Theperiodic nanostructures forms on Ag-AgCl thin films are anisotropic structures.

Effect of ruling engine cosine error on grating performance and error correction methold

xiaotao mi, Shanwen Zhang, hongzhu Yu, haili yu, Min Cong, and Xiangdong Qi

Doc ID: 345442 Received 10 Sep 2018; Accepted 06 Nov 2018; Posted 06 Nov 2018  View: PDF

Abstract: The cosine error of the diffraction grating ruling engine is a systematic error caused by the measurement system. This error affects grating performance directly. To reduce the effects of the cosine error on grating performance, we analyze the cause of the cosine error, establish a mathematical model based on the error and the related grating indicators, and propose a method to reduce the error. To validate the proposed method, we present the results of grating ruling experiments performed before and after cosine error correction, which show that the method effectively reduces the cosine error effects.

Power scaling potential of continuous-wave Cr:LiSAFand Cr:LiCAF lasers in thin-disk geometry

Umit Demirbas

Doc ID: 347164 Received 01 Oct 2018; Accepted 05 Nov 2018; Posted 06 Nov 2018  View: PDF

Abstract: Continuous-wave (cw) output powers from Cr:Colquiriite lasers are currently limited to 3 W level due to weak thermal andmechanical properties of colquiriite host that hinder power scaling efforts. Thin-disk (TD) geometry, which has enabledrecord power levels in Yb:YAG gain media, has not been thoroughly studied for Cr:Colquiriites yet. In this work, we havenumerically investigated cw lasing potential of TD Cr:LiSAF and Cr:LiCAF lasers in detail. Our analysis has shown that dueto its very low thermal conductivity and high susceptibility to temperature quenching of fluorescence lifetime, TD lasersbased on Cr:LiSAF will require usage of ultra thin (100 μm thick) crystals with large diameters (15-25 mm), which will bevery hard to prepare/handle due to its glass-like thermo-mechanical strength. Assuming such TD crystals could beproduced, we estimate that cw powers above 15 W might be feasible from Cr:LiSAF thin-disk lasers (TDLs) pumped by a100 W red diode. As an alternative, usage of Cr:LiCAF, which is the strongest member of Cr:Colquiriites in terms of thermomechanicalproperties, enables tighter focusing of pump beam on the TD, which in turn facilitates adoption of smallerdiameter samples (10 mm). We have estimated that when the thermally stronger c-axis is used for heat extraction and aaxisis used for lasing, cw powers exceeding 30 W could be achieved from Cr:LiCAF TDLs at an incident pump power of100 W. On the other hand, our model shows that the small signal gain that could be achieved via cw pumping ofCr:Colquiriite TD elements are below 0.5%. Hence, the aforementioned performance requires usage of high quality (Q)factor cavities with minimal intracavity losses.

Degeneracy in freeform surfaces describedwith orthogonal polynomials

Nicholas Takaki, Aaron Bauer, and Jannick Rolland

Doc ID: 341853 Received 08 Aug 2018; Accepted 05 Nov 2018; Posted 06 Nov 2018  View: PDF

Abstract: Orthogonal polynomials offer useful mathematical properties for describingfreeform optical surfaces. Their advantages are best leveraged by understanding theinteractions between variables such as tip and tilt, base sphere and conic variables, andpackaging variables that define the problem of design for manufacture. These interactions cancause degeneracy, which can complicate the interpretation of design specifications inmanufacturing and, consequently, negatively impact the cost of fabrication and assembly.Optimization constraints to break degeneracy during design are also discussed.

Compact gas refractometer based on atapered four-core fiber

Zhihua Shao, Xue-Guang Qiao, and Qiangzhou Rong

Doc ID: 345879 Received 14 Sep 2018; Accepted 05 Nov 2018; Posted 05 Nov 2018  View: PDF

Abstract: A compact in-line interferometer is proposed and experimentally demonstrated forgas refractive index (GRI) measurement. The sensor comprises a tapered four-core fiber(TFCF) sandwiched between two single mode fibers (SMFs), forming an in-line SMF-TFCFSMFstructure. The fiber taper acts as a bridge between the external GRI variation and themultimode interference within the TFCF segment. A high sensitivity of 1280.94 dB/refractiveindex unit is obtained in GRI measurement around 1.0. Temperature change only shifts theinterference wavelength and the cross-sensitivity of temperature can be ignored by intensitydemodulation. The proposed gas refractometer with improved performance can be a goodcandidate for chemical sensing or bio-sensing.

Passively Q-switched 1.989 μm all-solid-statelaser based on a WTe2 saturable absorber

Lijuan Chen, Xin Li, Haikun Zhang, and Wei Xia

Doc ID: 342742 Received 14 Sep 2018; Accepted 05 Nov 2018; Posted 06 Nov 2018  View: PDF

Abstract: In this paper, the novel two dimension (2D) tungsten ditelluride (WTe2) wassuccessfully fabricated by liquid phase exfoliation (LPE) method and used as saturableabsorber (SA) for a diode-end-pumped passive Q-switching Tm:YAP laser operating at 2.0μm wavelength band. The saturable fluence and the modulation depth of the prepared WTe2SA were determined to be 5.1 μJ⁄cm2 and 7.2 %. The maximum average output power of 0.64W was obtained with the shortest pulse width of 368 ns at the pulse repetition rate of 78 kHz.The corresponding highest single pulse energy and largest pulse peak power were calculatedto be of 4.8 μJ and 12.7 W, respectively. To the best of our knowledge, it is the first time thatWTe2 has ever been used as the SA for 2.0 μm solid-state bulk lasers. The results indicatedthat WTe2 should be an excellent SA for generating 2.0 μm pulsed lasers.

Metamaterial structures of variable and gradient basisorientations embedded with periodic linear defects:phase engineered design, single step opticalrealization and applications

Saraswati Behera and Joby Joseph

Doc ID: 344630 Received 30 Aug 2018; Accepted 05 Nov 2018; Posted 06 Nov 2018  View: PDF

Abstract: Metamaterial structures of different basis shape, orientations and with gradient refractive index variations areapplicable in integrated photonics, miniaturized optoelectronics, diffraction limited focusing and super-resolutionimaging. We present design and experimental realizations of gradient metamaterial structures embedded withlinear periodic defects and propose its applications in on-substrate color filtering through simulation based study.A combination of phase engineered plane beams in double cone geometry and an axial plane beam are interferedto obtain different gradient basis metamaterial structures with linear defects in 2D and 3D respectively. The defectsize and spatial gradient amplitude modulations can be controlled computationally through shift in interferenceangle for some of the plane beams in double cone geometry without changing any optical components in theexperiment. The designed and realized metamaterial structures upon transferring to certain material will findapplication in optical circuits and in metalenses for enhanced light matter interactions.

Modeling the surface of fast-cured polymer droplet lenses for precision fabrication

Yulung Sung, Jacob Garan, Zhenyu Hu, Xiaonan Shan, and Wei-chuan Shih

Doc ID: 345452 Received 10 Sep 2018; Accepted 05 Nov 2018; Posted 05 Nov 2018  View: PDF

Abstract: Optical lenses with diameter in the millimeter range have found important commercial use in smartphone cameras. Although these lenses are typically made by molding, recent demonstration of fast-cured polymer droplets by inkjet printing has gained interest for cost-effective smartphone microscopy. In this technique, the surface of a fast-cured polydimethylsiloxane droplet obtains dynamic equilibrium via the interplay of surface tension, gravity, thermalization, and a steep viscosity hike. The nature of surface formation involves multiple physical and chemical domains, which represent significant challenges in modeling with the Young-Laplace theory assuming constant surface tension and viscosity. To overcome these challenges, we introduce the concept of effective surface tension, which allows fast-cured polymer droplets to be modeled as normal liquid droplets with constant viscosity.

All-Optical Switching in Long-Period FiberGrating with Highly Nonlinear ChalcogenideFibers

Leilei Wang, Jianghui Zeng, Liang Zhu, Dandan Yang, qian zhang, Peiqing Zhang, Xunsi Wang, and Shixun Dai

Doc ID: 342740 Received 20 Aug 2018; Accepted 04 Nov 2018; Posted 05 Nov 2018  View: PDF

Abstract: All-optical switching in long-period fiber grating (LPFG) with Ge–As–Sechalcogenide fibers was proposed. The switching performances at different resonantwavelengths and cladding modes were systematically investigated using coupled-modetheory. By utilizing the ultra-high nonlinearity of chalcogenide glass, the switching powerthreshold of the proposed LPFG switching at 1.55 μm was 105 MW/cm2 with power couplingfor the low-order LP09 cladding mode, which was approximately 200 times lower than that ofsilica LPFG. Furthermore, the temperature stability of the proposed LPFG switching wasexamined. The optical switching instability due to laser thermal effect can be well suppressedby optimizing the cladding radius and grating period. Considering the balance betweentemperature sensitivity and switching power threshold, an all-optical switch with temperaturesensitivity of 51 pm/°C was finally realized by selecting LP051 mode with cladding radius of39 μm.

A Dielectric Loaded Graphene-BasedPlasmonic Multi-Logic Gate Using MMI Splitter

Mir Hamid Rezaei and Abbas Zarifkar

Doc ID: 344499 Received 30 Aug 2018; Accepted 04 Nov 2018; Posted 05 Nov 2018  View: PDF

Abstract: In this paper, we propose a multi-logic gate (MLG) by utilizing a dielectric loadedgraphene-based plasmonic waveguide (DLGPW) in the mid-infrared spectral region. Theproposed MLG is composed of DLGPW-based switches and multimode interference (MMI)splitters and supports three logical operations AND, XNOR, and NOR, simultaneously.Firstly, by proper control of the graphene surface conductivity, a graphene plasmonicON/OFF switch is presented and then, a 3 dB MMI splitter based on DLGPW for thewavelength of 7.8 μm is designed and investigated. Our studies show that electro-opticallogic gates based on DLGPW have not been reported to date. The structure of the presentedMLG is very simple and CMOS-compatible. The calculated minimum extinction ratios (ER)for AND, XNOR, and NOR logic gates are 17.53 dB, 53.43 dB, and 17.53 dB, respectively.Also, by some modifications, this structure can act as a NAND logic gate with ER of 55.22dB. Compact footprint, high extinction ratio, and easiness of on-chip implementation aresome advantages of the presented MLG.

Improving the spatial dynamic range of digitalinline particle holography

Zachary Falgout, Yi Chen, and Daniel Guildenbecher

Doc ID: 342847 Received 20 Aug 2018; Accepted 03 Nov 2018; Posted 05 Nov 2018  View: PDF

Abstract: Digital in-line holography (DIH) has been proven to provide three-dimensionaldroplet position, size, and velocity distributions with a single-camera. This data is crucial forunderstanding multi-phase flows. In this work, we examine the performance of this diagnostic inthe limit of very small particles, on the order of a pixel in diameter and smaller, and proposea post-processing method to improve them: Lanczos interpolation. The Lanczos interpolationkernel is the digital implementation of the Whittaker sinc filter, and strikes a compromise betweenmaintaining the spatial frequency ceiling of the original digital image and computational costof the interpolation. Without Lanczos interpolation, or super-sampling, the ultimate detectableparticle size floor is on the order of 4 pixel widths. We show in this work that this limit can bereduced by 50% or more with super-sampling, depending upon the desired diameter accuracy,and examine the effect of super-sampling on the resulting accuracy of the extracted size andposition of spherical particles. Extending this resolution limit increases the overall detectionefficiency of the diagnostic. Since this increases the spatial dynamic range of the diagnostic, itcan also allow a larger field-of-view to be captured with the same particle size floor.

Hybrid high-order nonlocal gradient sparsity regularization for Poisson imagedeconvolution

Tao He, Jie Hu, and Haiqing Huang

Doc ID: 344327 Received 29 Aug 2018; Accepted 03 Nov 2018; Posted 05 Nov 2018  View: PDF

Abstract: Images obtained by photon counting sensors are always contaminated with Poisson noise. Total variation (TV) hasbeen extensively researched in image deconvolution because of its remarkable ability to preserve details.However, TV is based on the prior that the global image gradient obeys a Laplacian distribution and can hardlymaintain the information of each part of the image. We extended the global TV to nonlocal modeling andestablished an intensity-adaptive nonlocal regularization based on similar blocks. Meanwhile, to restrain thestaircase effect caused by the first-order regularization, we proposed a new hybrid nonlocal regularization bymodeling the sparsity of the high-order derivative. An efficient alternating direction method of multipliers (ADMM)algorithm was employed to solve the proposed model, and the adaptive selection strategy of regularizationparameters in the model was further studied and analyzed. The experimental results show that the proposedhybrid high-order nonlocal gradient sparsity (HHONGS) regularization model achieves a substantial computationaltime improvement compared to another nonlocal restoration algorithm while producing a relatively clearrecovery image.

Particle profiling and classification by a dualbandcontinuous-wave lidar system

Guangyu Zhao, Elin Malmqvist, Sandra Török, Per-Erik Bengtsson, Sune Svanberg, Joakim Bood, and Mikkel Brydegaard

Doc ID: 338758 Received 13 Jul 2018; Accepted 03 Nov 2018; Posted 05 Nov 2018  View: PDF

Abstract: A dual-band continuous-wave (CW) light detection and ranging (lidar) system hasbeen developed for particle classification. In this lidar system, the range-resolved atmosphericbackscattering signal is recorded by an optical imaging system satisfying the Scheimpflugprinciple instead of the conventional time-of-flight approach. It is thus possible to employlow-cost and compact CW diode lasers, facilitating the development of a robust multiplewavelengthatmospheric lidar system which can attain high accuracy of the retrievedparameters of atmospheric particles. The present work demonstrates a dual-band Scheimpfluglidar system employing two diode lasers at 405 nm (0.5 W) and 808 nm (3.2 W). Exposuresare milliseconds apart and interpolated. Measurements of various types of particles andsmoke have been performed to verify the feasibility of using the present system for improvedparticle classification and sizing, for the situation when plumes were dilute and no significantopacity was detected.

Simple Stokes Polarimeter Using a Liquid CrystalGrating with Ternary Orientation Domains

Michinori Honma, Natsuki Takahashi, and Toshiaki Nose

Doc ID: 342479 Received 15 Aug 2018; Accepted 02 Nov 2018; Posted 05 Nov 2018  View: PDF

Abstract: We propose a liquid crystal (LC) grating with a ternary orientation domain for application to optical polarizationmeasurements. The ternary orientation domain, which generates two-dimensional diffraction properties, is thekey to simultaneous acquisition of multiple of polarization parameters. The LC molecular orientation state and thepolarization dependence of the diffraction efficiency were investigated experimentally, focusing on theapplicability to a practical Stokes polarimeter. An experiment was conducted using the proposed LC grating as aStokes polarimeter and the four Stokes parameters (S0, S1, S2, and S3) were determined for linearly and circularlypolarized incident light. As a result, the feasibility of the proposed LC grating Stokes polarimeter has beendemonstrated experimentally. Finally, the operational performance of the proposed LC grating Stokes polarimeteris discussed using a figure of merit that is numerically derived from the measured polarization dependence of thediffracted light intensity.

System Design for a "Checkerboard" Imager

Yu Qinghua, Ben Ge, yan li, yingbo yue, Chen Fuchun, and sun li

Doc ID: 345584 Received 11 Sep 2018; Accepted 02 Nov 2018; Posted 05 Nov 2018  View: PDF

Abstract: In order to solve the problem of uneven spatial frequency sampling and lack of zero frequency sampling in the Segmented Planar Imaging Detector for Electro-optical Reconnaissance (SPIDER), we propose a "Checkerboard" imaging system design using square grid aperture arrangement, show its aperture matching method, and demonstrate that it can achieve the uniform sampling of all integer multiples of fundamental frequency in the highest frequency range with zero frequency in the direction of two orthogonal arrays. Through computer simulation, it is verified that the imaging effect of the "checkerboard" imaging system is superior to that of the SPIDER imaging system and the traditional single aperture imaging system at the same system diameter.

Modeling the Ship White Water Wake in the Midwave Infrared

Vivian Issa and Zahir Daya

Doc ID: 342953 Received 27 Aug 2018; Accepted 02 Nov 2018; Posted 07 Nov 2018  View: PDF

Abstract: We have modeled the white water wake of a ship as a single layer of bubbles packed on the sea surface withinthe perimeter of the trailing turbulent wake. The bubbles size is considered greater than the mid-wave infraredwavelengths such that the optical geometrical approximation remains valid. The upper half bubble hemisphereis meshed into facets and we calculate the probability density function of their slopes and constrain thatdistribution by the geometrical limits imposed by the position of the receiver through shadowing of facets byother bubbles and of facets that are facing away from the receiver. For the facets that are visible, we computethe mid-wave infrared emitted and reflected radiance for the white water wake for atmospheric, solar and seaconditions that prevailed during a ship wake measurement trial using a home grown simulation code, the SeaSurface Radiance Simulator. The range of slopes that are visible to the receiver for the white water wakegreatly exceed those that are present in the turbulent wake and in the sea background. Consequently thevariability in the white water wake radiance is substantial. As a function of the downstream distance astern ofthe ship, we have ad hoc assumed that the white water wake fraction decays linearly or proportionally to theturbulent intensity in the wake. Comparing to measurements we find an agreement in trend behavior of themid-wave radiance contrast of the white water wake with downstream distance for a white water wake fractionthat decays proportionally to the square of the turbulence intensity.

Scanning Diffracted-Light Photography Using White-Light and Thermal Radiation Sources

Hawra Alghasham, Hira Farooq, Ceren Uzun, Sueli Skinner Ramos, Ayrton Bernussi, and Luis Grave de Peralta

Doc ID: 342617 Received 17 Aug 2018; Accepted 01 Nov 2018; Posted 02 Nov 2018  View: PDF

Abstract: A 4-f imaging arrangement of lenses with a camera, and a rotating slit placed at the Fourier plane of the system,was used to obtain the optical disturbance produced by a macroscopic sample. The sample was illuminated bycollimated beams from white-light and thermal radiation sources. The agreement between simulated andexperimental results, obtained by processing the captured images using a Fourier ptychographic algorithm,demonstrates that scanning with the slit, the direction of the light that is diffracted by the sample, permitsachieving the image diversity necessary for the successful implementation of the scanning diffracted-light imagingtechnique.

Topological charge measurement of vortex beamsby phase-shifting digital hologram technology

Xiansheng Hu, bamao Zhaxi, Osami Sasaki, Ziyang Chen, and Jixiong Pu

Doc ID: 344253 Received 27 Aug 2018; Accepted 01 Nov 2018; Posted 02 Nov 2018  View: PDF

Abstract: We propose a direct measurement method that is applicable to both integral and fractionalvortex beams. In this approach, the phase distribution of the vortex beam is visualized via thephase-shifting digital holography technique. The least square method is initiatively employed toimprove the measurement precision. The maximal error of the experimental results is below 4.8%.

Fast hydrogen detection via plasmonic MIM technology


Doc ID: 346500 Received 21 Sep 2018; Accepted 01 Nov 2018; Posted 02 Nov 2018  View: PDF

Abstract: In this study, a nano–scale sensor on Metal–Insulator–Metal (MIM) platform was studied numerically toinvestigate its hydrogen detection potential. The plasmonic MIM structure which consists of an air microringresonator (MRR) and a palladium (Pd) disk is used for this purpose. The results of the numericalstudy show that when the optimum geometric design parameters are employed, a sensitivity as highas 267 pm/(v/v-% hydrogen) can be obtained. In addition, a response time of 172.125 seconds could beachieved which is calculated according to the second law of Fick. The result of the study can lead futurestudies to design fast and high precision hydrogen gas sensors on a nano–scale base.

Accessible quantitative phase imaging inconfocal microscopy with sinusoidal-phasesynthetic optical holography

Arturo Canales-Benavides, Yue Zhuo, Andrea Amitrano, Minsoo Kim, Raul Hernandez-Aranda, P. Scott Carney, and Martin Schnell

Doc ID: 346297 Received 20 Sep 2018; Accepted 01 Nov 2018; Posted 01 Nov 2018  View: PDF

Abstract: We present a technically simple implementation of quantitative phase imaging inconfocal microscopy based on synthetic optical holography with sinusoidal-phase referencewaves. Using a Mirau interference objective and low-amplitude vertical sample vibration witha piezo-controlled stage, we record synthetic holograms on commercial confocal microscope(Nikon, model: A1R; Zeiss: model: LSM-880), from which quantitative phase images arereconstructed. We demonstrate our technique by stain-free imaging of cervical (HeLa), ovarian(ES-2) cancer cells and stem cell (mHAT9a) samples. Our technique has the potential to extendfluorescence imaging applications in confocal microscopy by providing label-free cell finding,monitoring cell morphology as well as non-perturbing long-time observation of live cells basedon quantitative phase contrast.

Free space variable optical attenuator using frustratedtotal internal reflection with 70 dB dynamic range

Tiberius Georgescu, Ioan Dancus, and Daniel Ursescu

Doc ID: 344664 Received 30 Aug 2018; Accepted 31 Oct 2018; Posted 31 Oct 2018  View: PDF

Abstract: With the advance of high power laser systems, there is an increasing need to dim the corresponding lightfield power over larger dynamic ranges. Usual means to control the attenuation of directed light usesoptical filters or coatings with tailored reflectance and transmittance properties. They do not provide thevariability that is often required in experiments. It is reported here a system that demonstrated continuousvariation of the transmittance over 70dB, using frustrated total internal reflection.

Surface plasmonic Bismuth ion-doped waveguide withblack phosphorus cladding

sampa nkonde

Doc ID: 346356 Received 21 Sep 2018; Accepted 31 Oct 2018; Posted 31 Oct 2018  View: PDF

Abstract: In this paper, a waveguide device with bismuth ion (Bi+) doped glass as core and black phosphorus (BP) acting ascladding is theoretically proposed. Finite-difference time-domain (FDTD) and numerical methods are used toelucidate the waveguide dispersion characteristics, elaborate the transverse electric (TE) mode profiles, solve thecharacteristic eigenvalue equations and calculate the gain /noise figure characteristics of the guiding medium. Thenumerical results show that the mode confinement factor for the fundamental mode with h = 5 μm, can reach 99.8%. The analytical results also indicate that with pump power fixed at 100 mW, the active ion concentration fixed at2 × 1027 ion/m3, the gain and noise figure of a waveguide device with 0.10 m-length is 34 and 3.38 dB, respectively.The proposed waveguide device is a promising candidate as a building block for various integrated photoniccircuits.

Analytic Inverse Solutions for Risley Prisms in FourDifferent Configurations for Positing and TrackingSystems

Shian-Fu Lai and Cheng-Chung Lee

Doc ID: 341824 Received 07 Aug 2018; Accepted 31 Oct 2018; Posted 01 Nov 2018  View: PDF

Abstract: The conventional ray deviation formula and analytical inverse solution for Risley prisms are traditionally derived by thefirst-order paraxial method, which is simplified and does not provide sufficient accuracy. When a light ray enters thewedge prism, the component that perpendicular to the base side is deviated by the wedge prism and the componentparallel to the base side is uninfluenced. In this study, the problem is presented and analyzed from scalar form of Snell'slaw and 2-D vector algebra to solve the problem. The rotation and refracting angles of a single wedge prism are obtainedby analyzing the propagation through the prism of incident rays from different directions, and ray deviation formulas arederived. Four configurations are described with ray deviation formulas and analytical inverse solutions deduced from thecorresponding formulas for a single wedge prism. In the final section, two examples are considered for the fourconfigurations. The numeric results demonstrate the accuracy of the inverse solution provided by the proposed method.

Thin lens aberrations for anamorphic lenses

Zhang Jinkai, Xiaobo Chen, Haining Liu, Fajia Li, and Xuan Sun

Doc ID: 342202 Received 04 Sep 2018; Accepted 31 Oct 2018; Posted 01 Nov 2018  View: PDF

Abstract: This paper provided the thin lens aberrations for anamorphic lenses, including the Central Thin Lens Aberrations,the Central Lagrange Invariant Shift, the Central Conjugate Shift, and the Central Pupil Shift. Based on the thin lenstheory and the paraxial lens module, the aberration of the anamorphic lens system can be easily corrected. TheCentral Lagrange Invariant Shift can be used for aberration correction for anamorphic zoom lens system. In orderto make a concise expression for Central Conjugate Shift, eight aberration coefficients are introduced: D_3x, D_5x, D_6x,D _10x, D_11y, D_12x, D_15x, and D_16y. Similarly, four aberration coefficients are introduced for Central Pupil Shift, which areD11x, D_11x, D16x, D_16x. A simulation is conducted at last which proves numerically the validity of the thin lensaberrations for anamorphic lens system.

Quantitative phase imaging of fiber Bragg gratings inmulticore fibers

Yijun Bao and Thomas Gaylord

Doc ID: 342597 Received 16 Aug 2018; Accepted 31 Oct 2018; Posted 01 Nov 2018  View: PDF

Abstract: Fiber Bragg gratings (FBGs) and multi-core fibers (MCFs) have independently demonstrated high levels ofperformance in numerous diverse applications. When integrated together, the devices can offer enhancedperformance as well as open more applications. In all of these cases, the refractive index (RI) characterization ofthe FBGs is crucial in monitoring and validating the fabricated devices. To accomplish this, quantitative phaseimaging (QPI) is a promising RI characterization candidate satisfying all of the needed requirements: noninvasive,quantitative, sub-micron resolution, no a priori knowledge, and 3D reconstruction. In this paper, we propose a newQPI method for characterization of the RI distribution of multiple FBGs in a single MCF. We have identified the keychallenges associated with this approach: pixel integration effect, aliasing effect, numerical aperture requirement,and characteristic functions recovery. We have further identified approaches for overcoming each of thesechallenges that have previously impeded this direction of research. The proposed method is supported bysimulations of 2D and 3D gratings.

Electrical internal quantum efficiency improved by top interval doping method

Ke Chen, Yuanyuan Wang, Xiaopeng Yu, Haishuo Wang, Rui Wu, and Hongmei Zheng

Doc ID: 342645 Received 17 Aug 2018; Accepted 31 Oct 2018; Posted 01 Nov 2018  View: PDF

Abstract: The electrical internal quantum efficiency is an important parameter to evaluate the utilization degree of the photonic current density. Amorphous silicon has a quite large absorption efficiency of the available incident light. However, the existing of substantial defects in the heavily doping amorphous silicon limits the electrical internal quantum efficiency. In this paper, we design a top interval doping structure for the amorphous silicon thin film solar cells. Most of the generated optical carriers in the top surface concentrate in the intrinsic region of the amorphous silicon layer. Due to the lower Fermi energy difference and smaller recombination rates, more optical generated carriers could be collected by the electrodes. Through the coupled calculation of optical simulation and electric simulation, the designed top interval doping amorphous silicon thin film solar cell’s electrical internal quantum efficiency is significantly enhanced in the whole wavelength range from 300 nm to 800 nm. The short circuit current density is improved from 11.45 to 14.20 mA/cm2, and the maximum output power increases from 5.78 W/cm2 to 6.93 W/cm2. All these results indicates that the top interval doping structure is suitable for improving the performance of the amorphous silicon thin film solar cells.

Random phase-shift Bragg grating-based random fiber laser with a half-open cavity

Ailing Zhang and Liyue Hao

Doc ID: 345123 Received 06 Sep 2018; Accepted 31 Oct 2018; Posted 01 Nov 2018  View: PDF

Abstract: A random fiber laser based on 25mm long random phase-shift fiber Bragg grating with a half-open cavity is experimentally demonstrated in this paper. The random phase-shift grating is fabricated in single-mode fiber with the beam-scanning method. The random feedback and light localization are achieved by introducing 20 phase shifts with random amplitudes along the grating length. Different couplers and different directions are adopted for investigating output characteristics under multiple conditions. The stable single-wavelength laser operation with the pump threshold of only 25mW is realized using a 980nm pump laser. The optical signal-to-noise ratio up to 67dB and the 3dB bandwidth of 17.7pm are obtained at the pump power of 350mW. It is found that the emitted wavelength varies linearly with the surrounding refractive index within a certain range by immersing the grating in different concentrations of NaCl solutions, which provides a potential method for lasing wavelength tuning and refractive index detection.

Three-dimensional endoscopic OCT usingsparse sampling with a miniature magneticdrivenscanning probe

Jie Wang, Yang Hu, and Jigang Wu

Doc ID: 345219 Received 06 Sep 2018; Accepted 31 Oct 2018; Posted 01 Nov 2018  View: PDF

Abstract: We propose to apply sparse sampling and compressive sensing (CS) reconstructionin three-dimensional (3D) endoscopic optical coherence tomography (OCT) for reducing theamount of data required in the imaging process. We used a home-made miniature sideimagingmagnetic-driven scanning probe with an outer diameter of 1.4 mm in a 1310 nmswept-source OCT system to acquire two-dimensional (2D) circumferential cross-sectionalimages of an ex vivo pigeon trachea sample. 3D imaging is then achieved by reconstructionfrom the multiple 2D images acquired while pulling the sample with a translation stage.Given a total translation distance, we achieved sparse sampling by randomizing the step sizesof the translation stage such that the total number of the acquired 2D frames are reducedcompared with conventional 3D imaging with equally-spaced step positions. We tested theCS reconstruction with reduced 2D frame numbers of 40%, 60%, and 80% compared with thecase of equally-spaced step positions. The results show that it is possible to recoverreasonable OCT images using sparse sampling with CS reconstruction. Compared withconventional equally-spaced sampling method, our method provides a novel way for imageacquisition and reconstruction, which could significantly reduce the amount of 3D OCTimaging data and thus the acquisition time.

Theoretical and experimental investigation ofcontinuous wave laser scribing on metal thin film:Effect of Power

Amir Hossein Shahbazi, ata koohian, Khosro Madanipour, and Mohammad Azadeh

Doc ID: 342497 Received 20 Aug 2018; Accepted 30 Oct 2018; Posted 31 Oct 2018  View: PDF

Abstract: In this paper, the scribing of the metal thin film using continuous wave laser is investigated theoreticallyand experimentally. We proposed a reversible relation between incident fluence and ablation width. Microscopicanalysis of the results compared to theoretical expectations. Scribing has been done by focusinga 450 nm laser diode beam on 100 nm chromium thin film. Beam power and scanning speed are varied inthe domains of 0.02 1.0 W and 0.05 5 mm/s, respectively. The microscopic images of the thin filmshow that the average ablation width on metal thin film varies slightly by increasing the scanning speedwhich was anticipated by theory. Moreover if scanning speed increases, the ablation quality is reducedsignificantly and is not compensated by increasing incident power. According to microscopic images ofthe sample, this method could be a good substitute for pulsed laser scribing in many applications likemaking solar cells.

Polarization sensitivity error analysis andmeasurement of Greenhouse gases MonitoringInstrument(GMI)

Luo Yan, Li Zhi Wei, Qiu zhenwei, Hailiang Shi, Dihu Chen, and Xiong Wei

Doc ID: 344585 Received 30 Aug 2018; Accepted 29 Oct 2018; Posted 31 Oct 2018  View: PDF

Abstract: GMI (Greenhouse gases Monitoring Instrument) is a spatial heterodyne spectroscopy (SHS) sensor to monitorgreenhouse gases (GHG) from space. Due to several kinds of polarization sensitive optical elements in GMI, tosome extent, the instrument becomes a polarization sensitive sensor. Its polarization sensitivity will reducethe radiometric accuracy and spectral inversion accuracy of GHG column concentration. Theoreticalradiation response models for analyzing the polarization sensitivity of GMI, which is mainly affected byscanning mirror beam splitter and diffraction gratings, are presented in this paper. Based on these modelsand the polarization performance testing, the theoretical and experimental results of the main spectral bandof GMI, covering the wavelength ranges of 1.568~1.583 μm for the carbon dioxide (CO2) detection, have beengiven respectively. The result shows that the linear polarization sensitivity is less than 0.65% and 1.32% innadir (45°, 0°) and in oblique view direction (45±20°, ±31°) respectively, and it meets the qualificationrequirement for the absolute radiometric calibration accuracy better than 5%. The absolute radiometriccalibration accuracy directly affects the accuracy of GHG concentration retrieval.

Tunable near-infrared optical vortex parametric laserwith versatile orbital angular momentum states

Roukuya Mamuti, Shungo Araki, Shigeki Nishida, Katsuhiko Miyamoto, and Takashige Omatsu

Doc ID: 344439 Received 28 Aug 2018; Accepted 29 Oct 2018; Posted 30 Oct 2018  View: PDF

Abstract: We demonstrate a tunable vortex laser with versatile orbital angular momentum (OAM) states based on asingly resonant optical parametric oscillator (OPO) formed of a non-critical phase-matching LiB3O5 (NCPMLBO)crystal. The selective generation of a signal (idler) output with three OAMs, including an up-converted(negative) OAM, is achieved simply by appropriate shortening (or extending) of the cavity. The compactcavity configuration also allows for the generation of the signal (idler) output with various OAMs by simplytuning the signal wavelength. The vortex output is tuned within the wavelength region of 0.74 μm to 1.84 μmwith a maximum pulse energy of 2.16 mJ from a pump energy of 9.3 mJ.

Detection and analysis of signal-to-noiseratio in injection laser system of SG-IIupgrade facility

Gang Xia, Wei Fan, Xiaochao Wang, Jiangfeng Wang, Dajie Huang, Jiangtao Guo, and Xiao Wang

Doc ID: 344635 Received 30 Aug 2018; Accepted 29 Oct 2018; Posted 30 Oct 2018  View: PDF

Abstract: The temporal contrast levels of laser pulse in the injection laser system ofShenguang-II upgrade facility are accurately measured and analyzed in detail. Thesesignal-to-noise ratio levels are determined by the extinction ratios of an acousto-opticmodulator, an electro-optic intensity modulator, and a combination of pockels cell andthin film polarizers. In addition, a drifting direct current bias voltage of an electro-opticintensity modulator and a phase modulation are also demonstrated to affect thesignal-to-noise ratio of the injection laser system. With a precise control of these factors,the injection laser system can output a nanosecond laser pulse with a signal-to-noise ratioof 47.37 dB. Moreover, a nanosecond laser pulse signal-to-noise ratio measuring devicewith a dynamic range and accuracy of 50 dB and 1 dB, respectively, is developed todetect the signal-to-noise ratio of a nanosecond laser pulse, which is 47.06 dB within anaccuracy range of 1 dB. The signal-to-noise ratio measuring device can detected the highcontrast laser pulse for the seed source unit in the high power laser facility accurately andconveniently.

Texture mapping based on photogrammetricreconstruction of the coded markers

Yongkai Yin, Hailong Chen, Xiang-Feng Meng, Xiulun Yang, and Xiang Peng

Doc ID: 345064 Received 05 Sep 2018; Accepted 29 Oct 2018; Posted 30 Oct 2018  View: PDF

Abstract: Texture mapping is one of the key procedures to generate the photorealistic threedimensional(3D) model. To avoid the dependence on the features of the texture and thegeometric model, the coded marker is introduced as the control point to assist the texturemapping. Multiple texture images containing the markers are captured, and the 3Dcoordinates of the markers are reconstructed with photogrammetry, meanwhile the parametersof the texture camera are optimized with the bundle adjustment strategy. Then the poseparameters of the texture mapping can be calculated with the assist of the marker registrationand the iterative closest point (ICP) algorithms. The validity of proposed algorithm isdemonstrated with the experiment on an ordinary object.

On the development of an effective image acquisitionsystem for diamond quality grading

Wenjing WANG and Lilong Cai

Doc ID: 332906 Received 04 Jun 2018; Accepted 29 Oct 2018; Posted 30 Oct 2018  View: PDF

Abstract: In this paper, an effective diamond image acquisition system is proposed for capturing images of the diamondsample under inspection separately with transmitted light and reflected light. The proposed systemconsists of two parts: a lighting system and an imaging system. The lighting system is a newly designedintegrating sphere that can control the light distribution in the image plane and provide uniform illuminationto the diamond sample while it is being inspected under white LED lamps with a specific spectralpower distribution. The imaging system comprises industrial-grade lenses, cameras and a sample loadingplate. One set of lens and camera is installed at the port of the lower hemisphere. This arrangementensures that all light rays illuminated to the image plane are transmitted light. On the other hand, alllight captured by the other set of lens and camera installed on the upper hemisphere is reflected light.The proposed design utilizes the ray-tracing processing method based on the physical properties of materialsand adjusts the parameters of each optical component. When properly designed, the signal-to-noiseratio of captured diamond images is significantly improved, so that imperfections inside the diamond oron its surface can be clearly distinguished. The proposed image acquisition system is cost-effective andcompact. The experimental results agree well with the theoretical analysis and verify the effectiveness ofproposed image acquisition system. The proposed system will facilitate, improve and simplify automateddiamond quality grading.

Mapping distortion correction in freeform mirrortesting by computer-generated hologram

Xuefeng Zeng, Xuejun Zhang, Xue Donglin, Zhongyu Zhang, and Jian Jiao

Doc ID: 337683 Received 03 Jul 2018; Accepted 29 Oct 2018; Posted 30 Oct 2018  View: PDF

Abstract: The distortion could be introduced in the null testing using CGHs (computer-generated holograms) for off-axisaspheres or freeforms with significant deviation. It will lead to the failure of testing results to guide deterministicoptical processing. In this paper, based on ray tracing and calibration marks applied to mirror surface, a highaccuracy method was proposed to correct the distortion. The correction error is less than 1 mm. A second andfourth mirror (SFM) of a reflective telescope prototype with F number of 6.5 and FOV of 76 degree was polished. Inthe process, distortion was corrected, and the position misalignment error is as small as 0.783 mm. For the sake ofalignment, the two mirrors were fixed on a 790mm×390mm SiC substrate. The RMS value of mirror surface error is0.0433λ (λ=0.6328 μm) after ion beam finishing (IBF) .

Study of wide-spectrum and high-resolution diractionoptical elements by stacks of binary phase gratings

I-Lin Ho and Wang-Yang Li

Doc ID: 338314 Received 10 Jul 2018; Accepted 29 Oct 2018; Posted 30 Oct 2018  View: PDF

Abstract: This work theoretically investigates wide-spectrum and high-resolutiondiraction optical elements (DOE) that are made of stacks of low-resolutionbinary phase gratings, whereby the two-dimensional grids in dierent gratinglayers are arranged with specified displacements. We remodel the commonKinoform algorithm for this multi-scale architecture. Numerical computationsshow that, by increasing the number of stacking layers, the resolution ofthe far-field image can be improved and that the optical elements are moreinsensitive to variations of incident wavelengths, at the cost of part accuracyof image reconstructions. Practical concern on largely increasing the numberof grating layers are eciency of the optical designs in theory and themanufacture of stacks of ultra-thin grating films.

A compact omnidirectional multi-stereo visionsystem for 3D reconstruction

zhiyu xiang, Shuya Chen, Lei Luo, and Nan Zou

Doc ID: 340330 Received 20 Jul 2018; Accepted 29 Oct 2018; Posted 30 Oct 2018  View: PDF

Abstract: Omnidirectional stereovision is beneficial in wide applications thanks to its largefield-of-view. Traditional implementation of such a system employs two separate cameras lookingat separate mirrors to achieve 3D stereo reconstruction. In this paper, a compact omnidirectionalmulti-stereo system that consists of only one camera and multiple mirrors is proposed. Thenovelty lies in the designing of a principal mirror above the array of sub-mirrors to achievemultiple omnidirectional stereo pairs that have appropriate baselines and multiple viewpoints ina compact manner. The system’s imaging projection and error propagation model are presented.The experiments based on simulation and real data verify the effectiveness of our system.

Ronchi and Moiré Patterns used to test spherical and aspherical surfaces using deflectometry.

Jesús Arriaga Hernández and Alberto Jaramillo-Núñez

Doc ID: 340562 Received 24 Jul 2018; Accepted 29 Oct 2018; Posted 30 Oct 2018  View: PDF

Abstract: The aim of this work is to compare the Ronchi testing and Moir\' e deflectometry with the results obtained from different mirrors. In order to do so, we use Ronchi patterns formed by two identical Ronchi rulings angularly displaced and located close to the curvature center for each mirror, giving as a result a Moir\' e of the Ronchigrams (Moir\' e-Ronchigrams) pattern of both mirrors. The results obtained from the Ronchi testing and Moiré deflectometry are compared using the Zernike polynomials of every wavefront.

Fringe discretization and manufacturing analysis ofCGH in null test of freeform surface

Zihao Gan, Xiaoqiang Peng, Shanyong Chen, Chaoliang Guan, Hao Hu, Xinlei Li, and zuocai dai

Doc ID: 344247 Received 28 Aug 2018; Accepted 29 Oct 2018; Posted 29 Oct 2018  View: PDF

Abstract: Computer-generated hologram (CGH) is the core component for aspheric surface test. According to thefabrication demands, it is necessary to convert the designed CGH phase compensation function into theprocessed pattern, that is, the fringe discretization process. In this paper, we proposed a new discretizationmethod for CGH in test of freeform surface, and realized the encoding of processed fringes by MATLAB software.Furthermore, we designed the experiment to verify the accuracy of the new discretization method and comparedthe calculation efficiency between the new algorithm and the reported algorithm. Finally, based on the testingrequirement of freeform mirror in camera optical system, we completed the design, encoding and fabrication ofCGH sample, and analyzed the influence of various errors on wavefront accuracy of CGH.

Engineering a coaxial visible/infrared imaging systembased on monolithic multi-surface optics

Yupeng Xiong, Yifan Dai, guipeng tie, Fan Bin, Zihao Gan, and Shanyong Chen

Doc ID: 346920 Received 28 Sep 2018; Accepted 29 Oct 2018; Posted 31 Oct 2018  View: PDF

Abstract: All-reflective coaxial visible/infrared imaging system based on monolithic multi-surface optics has been a hot pointin recent years. Since multiple surfaces share a single substrate, their relative positions are fundamentally to beguaranteed as fabricated without any alignment. In this paper, the coaxial system is designed with multi-foldedideas. And both visible subsystem and infrared subsystem are comprised of two monolithic optical modules whichare machined by single point diamond turning (SPDT). A novel method based on computer generated hologram(CGH) is then proposed to simultaneously measure the shape and position of monolithic multi-surface optics. Theeffect of surface shape and position error on the wavefront aberration of the system is also discussed with the helpof Zernike annular polynomials. Then the wavefront aberration of the system is measured, from which we subtractthe contribution of surface shape and position error. The aberration induced by misalignment of the twomonolithic modules is then estimated. It indicates the concentricity is about 3μm. Finally, two similar systems withdifferent clear apertures are assembled as a coaxial visible/infrared imaging system. Coaxial visible and infraredimages are captured and fused to show clearer details.

Fusion of multi-focus image via Gaussian curvaturefilter and synthetic focusing degree criterion

Wei Tan, Huixin Zhou, shenghui Rong, Kun Qian, and Yue Yu

Doc ID: 338820 Received 20 Jul 2018; Accepted 29 Oct 2018; Posted 02 Nov 2018  View: PDF

Abstract: The aim of multi-focus image fusion technology is to acquire an image of every scene all in focused on the samevisual point at different focal settings. To achieve the goal, we propose an improved multi-focus image fusionalgorithm based on Gaussian curvature filter and synthetic focusing degree criterion. First, in order to realize thesalient feature extraction, a Gaussian curvature filter is applied to obtain the most sharpness regions. Then weobtain a coarse fusion map by composing a synthetic focusing degree criterion (FDC) which is combined of thespatial frequency and the local variance of image together. The coarse fusion map is further processed bymorphological filters and median filters to acquire an optimized fusion map. Finally, the fusion image is obtainedby weighted fusion operation. Experimental results demonstrate that our proposed algorithm can becompetitive with or even outperforms many existing fusion methods in both the qualitative and quantitative.

Depolarization characteristics of spatial modes inimaging probe using short multimode fiber

Manabu Sato, Kai Eto, Junpei Masuta, and Izumi Nishidate

Doc ID: 345753 Received 13 Sep 2018; Accepted 29 Oct 2018; Posted 05 Nov 2018  View: PDF

Abstract: Optical coherence tomography (OCT) is one of the standard imaging modalities at present, that is widely used in the medicaland biological fields, to obtain three-dimensional (3D) images with high spatial resolution. However, the depth up to whichthe 3-D images can be directly obtained is limited to within 3 mm. Therefore, the suitability of many kinds of catheters andneedles has been considered for minimally invasive imaging. We have examined the utility of a short multimode fiber(SMMF) using graded index optical fibers for minimal invasive imaging of deeper areas, up to 6–8 mm. The diameter andlength of the SMMF are 125 μm and 6–8 mm, respectively. In the core of the SMMF, scattering and multi-refraction occurdue to small variations in the refractive index to generate deforms and depolarization of images. In order to investigate thedepolarization characteristics, the images reflected at the facet of the SMMF were measured by changing the angle of thepolarizer, using an LED as the light source. The reflection image almost corresponds to that obtained with combined linearlypolarized (LP) modes with the ratio of LP01 : LP11 : LP21 equal to 1 : 0.2 : 0.7. Comparing the measured results withsimulations in the simple model, the depolarization ratio was estimated at 0.7 in the core. The degrees of polarization weremeasured to be 0.15 around the center and increased to 0.90 at the periphery.

Improvements to Dispersed Reference Interferometry:beyond the linear approximation

Andrew Henning, James Williamson, Haydn Martin, and Xiangqian Jiang

Doc ID: 345367 Received 11 Sep 2018; Accepted 28 Oct 2018; Posted 29 Oct 2018  View: PDF

Abstract: Interferometric instruments with dispersion introduced in the reference arm have previously been createdas the controlled dispersion can be used to generate a signal which contains a clearly identifiablepoint, the location of which relates to the position of the scattering surface in the measurement arm. Inthe following we illustrate that the linear approximations that have been used previously can lead to significanterrors, and that second order terms need to be included in order to correct this. These correctionsare vital if these instruments are to be used for metrological applications.

Low-power total internal reflection thermo-opticswitch based on hybrid SiON-polymer X-junctionwaveguides

Qian Qian Song, Kaixin Chen, Lingfang Wang, Jia Qi Guo, Shuo Chen, and Zheng Xiang

Doc ID: 341008 Received 30 Jul 2018; Accepted 26 Oct 2018; Posted 29 Oct 2018  View: PDF

Abstract: We propose and demonstrate a low-power 2×2 total internal reflection thermo-optic switch based on an X-junctionconfiguration formed with silicon oxynitride (SiON) core and polymer cladding. Unlike these X-junctions reportedso far, our proposed configuration features a slot formed on the center of the X-junction and filled with polymercladding. With such a configuration, the opposite thermo-optic characteristics of SiON and polymer and hence heatutilization efficiency can be fully utilized. Our fabricated proof-of-principle switch shows extinction ratios of largerthan 15.34 dB and switching powers of less than ~59.6 mW. The rise time and fall time of switching are 1.42 ms and0.85 ms, respectively. The insertion losses are less than 10.6 dB for all channels and the polarization dependentloss (PDL) is ~0.3 dB.

Reducing residual focus error signal in optical pickuphead astigmatism displacement systems using novelsignal conditioning method

Vo Sang, Fengzhou Fang, Xiaodong Zhang, and Linlin Zhu

Doc ID: 341429 Received 02 Aug 2018; Accepted 26 Oct 2018; Posted 29 Oct 2018  View: PDF

Abstract: As an important measurement technique, focusing error detection by the astigmatic method is widely usedowing to its simple operation and low cost. Nevertheless, the existing of focus error signal (FES) signal areprone to control circuit and signal conditioning method caused by noise. To address this, in this paper anastigmatic detection system is constructed with a modified digital video disc (DVD) optical head. By designstable laser drive control circuit, low noise signal conditioning method, the developed of system can reducethe FES of background noise. Additionally, by analyzing the data interpolation and approximation model, thecorresponding defocus error signal is extracted. The exactly optical design of the method have been verifiedthrough simulations. Moreover, an experiment is set up to verify the feasibility of the developed method. It isconcluded that the method is effective to reduce the background noise is 2nm and the standard deviation is2.15mV with PZT working frequencies range from 300Hz to 2kHz.

High-efficient calculation method forcomputer-generated holographic stereogramusing a look-up table

Zi Wang, Guoqiang Lv, Qibin Feng, Anting Wang, and Hai Ming

Doc ID: 341779 Received 07 Aug 2018; Accepted 26 Oct 2018; Posted 29 Oct 2018  View: PDF

Abstract: A high-efficient calculation method to synthesize computer-generated holographicstereogram using a look-up table (LUT) is proposed. The complete phase distribution (CPD)of a spherical wave with larger size than the hologram is pre-calculated and stored as a LUT,and the wavefront converging to each viewpoint can be directly obtained by adding a specificpart of the pre-calculated CPD to the parallax image, instead of computing the wavefrontspixel by pixel in the conventional method. The computation amount and calculation time areeffectively reduced to 1/3 of the conventional method. The working memory size is reducedeffectively using the symmetry of the phase distributions of different viewpoints. Simulationand optical experiment are performed to verify the proposed method.

Design and experimental demonstration of pointingcorrection module for a Fizeau imaging interferometer

Jianwei Xue, aimin jiang, Sen Wang, jing wang, Yanfeng Dai, and Zhichao Dong

Doc ID: 341971 Received 09 Aug 2018; Accepted 26 Oct 2018; Posted 29 Oct 2018  View: PDF

Abstract: To increase the spatial resolution while circumventing the problems of increased mass and volume of monolithictelescopes, a Fizeau imaging interferometer testbed (FIIT) with three individual sub-telescopes was designed andconstructed for high resolution astronomical observation. FIIT is intended to be mounted on a distributed smallsatellitesconstellation with a formation fly configuration, thus the extremely stable pointing of the sub-telescopesis the prerequisite for phased imaging, which is because the satellite suffers from some extent of detrimental jittersand drifts needs to be corrected by FIIT itself. FIIT takes use of a shared tip/tilt detection module with crosscorrelationalgorithm, three fast steering mirrors and closed loop control technology for pointing correction ofthree sub-telescopes, which can make sure the images of them are co-aligned for a long period of time used to imagesome faint astronomical objects. This study gives a detailed description of the detection algorithm of imageshifts, the hardware design and data processing flow, followed by closed loop experiments of wide-band white lightpoint source. The results of residual errors on the detection camera and the beam combining camera demonstratethe performance of the pointing correction function, which is a significant milestone for FIIT.

Fourier conjugate adaptive optics for deep-tissue largefield of view imaging

Lyubov Amitonova

Doc ID: 342570 Received 17 Aug 2018; Accepted 26 Oct 2018; Posted 29 Oct 2018  View: PDF

Abstract: Light microscopy enables multifunctional imaging of biological specimens at unprecedented depths andresolutions. However, the performance of all optical methods degrades with the imaging depth due to sampleinducedaberrations. Methods of adaptive optics (AO), which are aimed at pre-compensation of these distortions,still suffer from a limited field of view and imaging depth as well as have inconvenient microscope design. Here Ipropose and investigate a new approach to overcome these limitations: Fourier image plane conjugate AO. Twoexperimental designs of the new approach are carefully studied and an accurate comparison between differentmethods of AO is presented. Fourier conjugate AO provides a larger field of view, which can only be limited by theangular memory effect, and allows the optimal use of the spatial light modulator. Moreover, theoretically possibleimaging depth of Fourier conjugate AO is limited only by working distance of the objective and not by themicroscope design.

An alternative approach for optical monitoringof arbitrary distributed substances

Artur Martirosyan, Radik Kostanyan, Pavel Muzhikyan, and Hrayr Azizbekyan

Doc ID: 339876 Received 16 Jul 2018; Accepted 25 Oct 2018; Posted 26 Oct 2018  View: PDF

Abstract: In this paper, we propose a novel approach for optical monitoring of integralproperties of arbitrarily distributed substances by means of specially designed opticalelement – radially-quadratic transmittance apodizing filter. The developed remote sensingmethod deals with non-matrix detectors, and requires only one-step conversion of lightenergy into electrical signal to investigate the substance under study. Due to the fact thatdetectors work in the linear sensitivity range, the nonlinear uncertainty of measurementsis minimal. Theoretical studies have been performed to derive formulas characterizing thesubstance parameters: distribution center, drift and drift speed of the center, radialstandard deviation and its changing rate, diffusion. The technique is applied to remotelymonitor the process of reduction of artificial snow area on the mock-up surface coveredwith a soil.

Digital holographic study on dynamicresponse of plates with geometric andmaterial discontinuities simulating insertpotted metallic honeycomb sandwichstructure

Binu P. Thomas, Annamala S, and Chittur Narayanamurthy

Doc ID: 345595 Received 14 Sep 2018; Accepted 25 Oct 2018; Posted 26 Oct 2018  View: PDF

Abstract: Inspection of face sheet bonding through optical interferometry techniques likeholography and shearography in insert potted honeycomb cored sandwich panels is differentfrom those without inserts due to its complex response towards thermal and vibrationstressing. In this paper dynamic responses of metallic honeycomb cored sandwich structureswith bonded and debonded inserts are studied using time average digital holography and areillustrated. At high frequencies the face sheet regions at perfectly bonded insert act as hardpoints and regions across a debonded insert locally resonate in the sensitivity range ofinterferometry. Since the discontinuities created by such inserts are very complex to simulatenumerically, to validate this fast inspection procedure, insert potted sandwich structures aresimulated through plates with multiple holes and with fully and partially bonded multiplelocal stiffeners. The simulated dynamic response of plate is compared with time averagedigital holography results. The operational deflection shapes near stiffeners is similar to thatof fully potted inserts in a sandwich panel. Thus the extent of debond can be evaluated at highfrequencies as simulated through partially bonded stiffeners.

Schlieren two-photon microscopy for phase-contrastimaging

Hao Xie, Yuanlong Zhang, Lingjie Kong, Peng Xi, and Qionghai Dai

Doc ID: 343087 Received 27 Aug 2018; Accepted 24 Oct 2018; Posted 24 Oct 2018  View: PDF

Abstract: While simultaneous phase-contrast and two-photonfluorescence imaging in microscopy can bring abundantbiomedical information, it is difficult to retrievephase information from conventional two-photon microscopes.In order to realize low-cost, in-situ phasecontrastand two-photon fluorescence imaging, wepropose Schlieren Two-Photon Microscopy (S2PM), amethod that implements phase-contrast imaging ontwo-photon microscopes. This method involves spatiallymodulated fluorescence plates, which are madeof two-photon fluorescence dyes or up-conversionnanoparticles (UCNPs). We demonstrate the fluorescenceintensity fluctuation reflects the phase gradientsof the specimen via theoretical analysis, simulationsand experiments. The proposed method is fully compatiblewith commercial two-photon microscopes, thusenabling widespread applications in live tissue imaging.

Design Photonic Crystal Elliptical-Hole taperedLow-Index-mode Nanobeam Cavities for sensing

Lijun Huang, Dajiang He, Xianwu Mi, Jianqun Ding, Shenghai Chen, and Xiaoliang Peng

Doc ID: 337594 Received 02 Jul 2018; Accepted 23 Oct 2018; Posted 24 Oct 2018  View: PDF

Abstract: A one-dimensional photonic crystal elliptical-hole tapered low-index-mode nanobeamcavities sensor fully encapsulated in water environment is firstly proposed. In the proposed structure, toconfine the light in the low-index region and enhance the light-matter interaction, tapered major axis ofthe elliptical hole away from the nanobeam cavities center is optimized. By three-dimensionalfinite-difference time-domain simulation, the results show that the low-index-mode of middle geometrycell is confined in the photonic bandgap of two-side cells. The highest quality factor of 6.04×105 isachieved when 13 tapered segments and 5 mirror segments are placed at the both sides of the hostwaveguide. The proposed nanobeam structure possesses theoretically the sensitivity of 244.7 nm/RIU(refractive index unit) in water circumstances. Moreover, an ultra-compact footprint of 6.4 μm×0.85μm is achieved, which is only a half of the size compared to the best value reported for the nanobeamstructure. The results indicate that it is a promising sensor for excellent on-chip sensing with respect tothe very small footprints.

Ratiometric optical sensor for high-resolution Imagingof pH with Low Cross-Talk

Zike Jiang, Jiantao Chen, Jiewei Du, Tiesheng Liu, Xiaofeng Li, Huibin Yu, Qi Zhang, Yimeng Hu, Fengchen Liu, Xinsheng Yu, and Zhonghai Zhou

Doc ID: 344522 Received 07 Sep 2018; Accepted 23 Oct 2018; Posted 25 Oct 2018  View: PDF

Abstract: We synthesize lipophilic, highly efficient and pH-insensitive oleic acid-modified quantum dots (QDs) with themaximum emission at a wavelength of 628 nm. The pH sensing film is fabricated by encapsulating 5-Hexadecanoylamino-fluorescein(5-Fluorescein) and QDs as the reference in D4–Hydromed (D4) and plasticizedpolystyrene (PS). Using the light-emitting diode (LED) with a central wavelength of 410 nm as an excitation source,it is shown that the emission wavelengths of the pH sensitive indicator and the reference dye have no spectraloverlap and match respectively the channels of a 3CCD (RGB) camera with low cross-talk. A series of validationexperiments shows that this ratiometric pH optode has good properties in high sensitivity, long-term stability, andphotostability. It had a fast response time of <20 s when going from pH 6.3 to 8.0. The pH images suggested that theproposed ratiometric pH sensing approach had great advantage and promise for the field applications.

Calibration method of overlay measurement errorcaused by asymmetric mark

Juyou Du, Fengzhao Dai, Yang Bu, and Xiangzhao Wang

Doc ID: 341711 Received 06 Aug 2018; Accepted 22 Oct 2018; Posted 24 Oct 2018  View: PDF

Abstract: With the process nodes extending to sub-10nm in advanced semiconductor manufacturing, the overlayrequirements keep progressively scaling down, which makes it very important to measure overlay precisely formonitoring on-product performance. The overlay mark being asymmetrical when generated via the lithographyprocess, this asymmetry will be slightly variated even in the same process or same lot, and it will bring overlaymeasurement error. In general, the wafer alignment data are used for correcting this overlay measurement error,utilizing its wavelengths and polarizations dependence. However, there is a residual error cannot be removed.Because the structures of wafer alignment mark and overlay mark are different, and affected by process differently.In this paper, a new method is proposed for calibrating overlay measurement error introduced by asymmetricmark, which is based on the relationship between measurement data of the overlay mark and the single layer mark.The validity is verified by simulation with different types of asymmetric mark. It is very useful for improvingoverlay measurement accuracy, and for understanding how the overlay measurement error affected byasymmetric mark.

Inverse Problem based on Fast-ADMMAlgorithm in Multi-angle TIRFM

jinyu li, Wei Han, Yanmin Li, Yachen Chen, Yu Shang, Youhua Chen, and Zhiguo Gui

Doc ID: 341173 Received 30 Jul 2018; Accepted 22 Oct 2018; Posted 25 Oct 2018  View: PDF

Abstract: Multi-angle total internal reflection fluorescence microscopy (TIRFM) hasbecome one of the most important techniques for achieving axial super resolution. Thekey process in this technique is solving the inverse problem. This paper applies animproved alternating direction method of multipliers (ADMM) algorithm to solve theinverse problem and validates the accuracy of the algorithm by reconstructing simulatedmicrotubule structures in multi-angle TIRFM images. The reconstruction times fordifferent algorithms and the convergence speeds of the improved and original algorithmsare compared. Experimental results show that the improved algorithm can achieve anaxial resolution of 40 nm, reduce the influence of the penalty parameter on convergence,and improve the convergence speed of the iterative process while ensuring imagereconstruction quality. Based on the algorithm, a three-dimensional image with the depthinformation of microtubules and mitochondria is reconstructed.

Three-dimensional thermal model of a highpower diode laser bar

Di-Hai Wu, Chung-en Zah, and Xingsheng Liu

Doc ID: 342161 Received 13 Aug 2018; Accepted 22 Oct 2018; Posted 22 Oct 2018  View: PDF

Abstract: An analytical, three-dimensional, steady-state thermal model of a high power diodelaser bar is presented in this paper. The heat spreading angle in a laser bar heatsink subject toseveral convective conditions on the bottom-side was calculated with this model. Thermaldesign curves for the heatsink and submount are also presented. Special discussion ispresented for two kinds of our conduction-cooled laser bars. Finite element simulation andexperimental results based on the wavelength shift method are compared with this analyticalsolution. The familiar 45° angle in thermal design for a commercial hard solder conductioncooledlaser bar (HCS) was found to lead to a 12% increase in thermal resistance relative to afree lateral diffusion heatsink.

Diffraction Grating 3D Display Optimization

Young Ju Jeong

Doc ID: 344417 Received 31 Aug 2018; Accepted 22 Oct 2018; Posted 22 Oct 2018  View: PDF

Abstract: This paper proposes a 3D light field optimization algorithm for a pixelwise directional 3D display using diffraction grating. Design of grating optics is important in the development of 3D displays and augmented reality devices. Unlike typical 3D optics such as lenticular lenses and parallax barriers, grating optics can be manufactured for each independent pixel. This can be a significant advantage, but it can also cause difficulties because the light field arrangement can reduce the width of the gratings, yielding low luminance and high crosstalk. A light field generation algorithm that simultaneously optimizes the grating width and 3D quality is proposed in this paper. Experimental results confirm the proposed theory.

Evaluation of image matching techniques foroptical fiber specklegram sensor analysis

Eric Fujiwara, Yoshi Ri, Yu Tzu Wu, Hiroshi Fujimoto, and Carlos Suzuki

Doc ID: 340682 Received 25 Jul 2018; Accepted 21 Oct 2018; Posted 22 Oct 2018  View: PDF

Abstract: A quantitative study of image matching techniques applied to fiber specklegramsensor analysis is presented. The fiber status is modulated by a microbending transducer, sothe output speckle field can be correlated to the input displacements. Once acquired andpreprocessed, the specklegrams variations were evaluated according to 7 approaches.Although the average intensity per se did not provide reliable information, the correlation andsum of differences methods yielded ~11 and ~14 mm-1 sensitivities, respectively, within a~0.06 mm range and low linearity and hysteresis errors, with enhancement possibility byintensity level cancellation. Moreover, the phase-only correlation and the mutual informationmetrics provided very high sensitivities (22 and 120 mm-1, respectively) for a <0.02 mmrange, making these techniques suitable for detecting subtle variations in the fiber status dueto physical or chemical stimuli.

Research on high-resolution imagingtechnology based on light field manipulationfor lenslet-based plenoptic camera

Xincheng Liu, Haotong Ma, ren ge, bo qi, Zongliang Xie, qiu chu, and junjie bai

Doc ID: 340966 Received 27 Jul 2018; Accepted 21 Oct 2018; Posted 22 Oct 2018  View: PDF

Abstract: In this paper, an aberrations correction method for an extended target is proposedto solve the problem that the lenslet-based plenoptic camera cannot image clearly under theinfluence of the aberrations. We propose a light field manipulation method to improve theperformance of the light field imaging system. The principle of this method is that thesub-aperture images extracted from the raw light field image will offset when the light fieldimaging system is affected by the aberrations, and the symmetrical arrangement of thesub-aperture images array is destroyed. By repairing the symmetrical arrangement of thesub-aperture images array, the influence of phase aberrations on the imaging system can beeliminated, and the resolution of the plenoptic camera can be improved. We use imagecorrelation algorithm to process the sub-aperture images of the plenoptic camera, calculateand compensate each sub-aperture image’s displacement caused by aberrations, restore thesymmetrical arrangement of the sub-aperture images array, then a corrected high-resolutionrefocused image can be generated. In particular, this method only uses the raw light fieldinformation obtained by the plenoptic camera in a single exposure, while without addingother hardware devices. Furthermore, it takes the extended target itself as the referenceimage, so the ideal position need not be calibrated in advance. Besides, the parallaxinformation of the sub-aperture images are retained, and the method is simple and easy to beused. Numerical simulation and experimental results show that the technology proposed inthis paper can work well for high resolution imaging of plenoptic camera with phaseaberrations. This method can be potentially applied to analyze lens aberration, media inducedimage distortion such as water turbulence in underwater imaging and atmospheric turbulencein remote imaging. It may have important application prospects in the fields of astronomicalobject detection, remote sensing, etc.

Design and realisation of a wide field of view infraredscanning system with integrated MEMS mirror

Chengxi Zhu, Matthew Hobbs, Matthew Grainger, and Jon Willmott

Doc ID: 342288 Received 14 Aug 2018; Accepted 21 Oct 2018; Posted 24 Oct 2018  View: PDF

Abstract: We present a wide field of view (FOV) infrared scanning system, designed for single-pixel near-infrared thermalimaging. The scanning system consisted of a two-axis micro-electro-mechanical system (MEMS) mirror that wasincorporated within the lens. The optical system consisted of two groups of lenses and a silicon avalanchephotodiode. The system was designed for both the production of real-time thermal images and also to utilise thetechniques of radiation thermometry to measure the absolute temperature of targets from 500 oC to 1100 oC. TheFOV of our scanning system was +/- 30° when fully utilising the MEMS mirror’s scanning angle of +/- 5°. The pixelFOV (calculated from the distance to target size ratio) was 100:1. The image quality was analysed, including theMTF, spot diagrams, ran fan plots, lateral chromatic aberrations, distortion, relative illumination and size-ofsourceeffect. The instrument was fabricated in our laboratory and one of the thermal images, which was takenwith the new lens, is presented as an example of the instrument optical performance.

Vision system with high dynamic range foroptical surface defect inspection

Zhaolou Cao, Fenping Cui, and Chunjie Zhai

Doc ID: 341707 Received 06 Aug 2018; Accepted 19 Oct 2018; Posted 30 Oct 2018  View: PDF

Abstract: We report a machine vision system with high dynamic range designed for opticalsurface defect inspection. The system consists of two motorized linear stages and onemotorized rotation stage for automatically scanning the surface. As intensity of long scratchesand digs differ a lot under dark-field illumination, gains of red, green and blue channels areset to be different value to extend the dynamic range of ordinary colored detector in a singlesnapshot, which greatly improve the efficiency compared with multi-exposure-basedapproaches. Image stitching is then employed to get high-resolution image of the entireoptical surface for further processing to quantitatively evaluate surface quality based on thestandards of MIL-PRF-13830B and ISO 10110-7:2008. The system can be widely applied inoptical industry as it provides a low-cost solution for optical surface quality check.

PolySpec: polynomial spectrum models for fastand light-weight spectroscopic evaluation

Johannes Emmert, Niels Göran Blume, Andreas Dreizler, and Steven Wagner

Doc ID: 347029 Received 01 Oct 2018; Accepted 16 Oct 2018; Posted 26 Oct 2018  View: PDF

Abstract: For the analysis of spectroscopic data, model fitting approaches are commonlyapplied. The spectrum model applied in these fitting processes significantly influences theperformance of the spectroscopic evaluation, which can be critical in real-time process diagnosticsand control. In this work a spectrum model is introduced that uses a polynomial description ofabsorbances, transmittances or similar in dependence on parameters such as temperature, pressureand mole fraction. Using this approach, either experimental spectra or spectrum databases canbe compressed into a matrix of polynomial coefficients. The evaluation of this model consists ofa single matrix multiplication and, with a slight modification, derivatives with regard to specificparameters can be calculated in the same way. Both these points are important to model fittingmethods for spectroscopic data, as the simple evaluation method allows for a fast analysis andthe direct calculation of derivatives simplifies the application of gradient-based fitting methods.Additionally, the easy parallelizability of the matrix multiplication promotes the application ofthis method in real-time evaluations on programmable logic devices.

Object Plane Detection and Phase Retrieval fromSingle-Shot Holograms using Multi-Wavelength In-LineHolography

Hanqing Zhang, Tim Stangner, Krister Wiklund, and Magnus Andersson

Doc ID: 337820 Received 04 Jul 2018; Accepted 15 Oct 2018; Posted 17 Oct 2018  View: PDF

Abstract: Phase retrieval and the twin-image problem in digital in-line holographic microscopy can be resolved byiterative reconstruction routines. However, recovering the phase properties of an object in a hologramneeds an object plane to be chosen correctly for reconstruction. In this work, we present a novel multiwavelengthiterative algorithm to determine the object plane using single-shot holograms recorded atmultiple wavelengths in an in-line holographic microscope. Using micro-sized objects, we verify the objectpositioning capabilities of the method for various shapes and derive the phase information using syntheticand experimental data. Experimentally, we built a compact digital in-line holographic microscopysetup around a standard optical microscope with a regular RGB-CCD camera and acquire holograms ofmicro-spheres, E. coli and red blood cells, that are illuminated using three lasers operating at 491nm,532nm and 633nm, respectively. We demonstrate that our method provides accurate object plane detectionand phase retrieval under noisy conditions, e.g., using low-contrast holograms with inhomogeneousbackground. This method allows for automatic positioning and phase retrieval suitable for holographicparticle velocimetry, and object tracking in biophysical or colloidal research.

Precision manual measurements of Gaussian beam sizes

Mikis Mylonakis, SAURABH PANDEY, Kostas Mavrakis, Giannis Drougakis, Georgios Vasilakis, Dimitris Papazoglou, and Wolf von Klitzing

Doc ID: 340558 Received 25 Jul 2018; Accepted 15 Oct 2018; Posted 17 Oct 2018  View: PDF

Abstract: We present a simple manual method to quickly, and accurately measure Gaussian beam sizes from the sub-millimeter to the centimeters range without the need of any specialized equipment.Simply moving a wire through the beam and recording the relative losses using an optical power meter, one can measure the beam diameters with a repeatability of 1\%. The precision of this method has been verified down to the limit of a commercial slit-based beam profiler (3\%).

Coupling Ultrafast Laser Pulses into Few-Mode Optical Fibers: A Numerical Study of the Spatiotemporal Field Coupling Efficiency

Zhe Guang and Yani Zhang

Doc ID: 335750 Received 09 Jul 2018; Accepted 10 Oct 2018; Posted 10 Oct 2018  View: PDF

Abstract: Few-mode optical fibers have been widely used in applications such as data transmission and laser amplification. The coupling of laser beams into such fibers is important because it determines the fiber mode contents, which influence the beam quality, laser amplification efficiency, and appropriate distortion control methods. Ultrafast lasers, as a widely used type of laser source for intense-field applications, can generate pulses with broad spectra and varying phases, adding complexity to the fiber mode coupling problem. In this paper, we numerically study the coupling performance of ultrafast laser pulses into few-mode fibers, investigating the mode coupling efficiency under different launching field conditions. Certain modes can be optimized with their coupling efficiencies in presence of pulse spatiotemporal couplings, which provides a new perspective toward generating complex waveforms and studying laser matter interactions.

Theoretical range precision obtained bymaximum-likelihood estimation in laser radarcompared with the Cramer-Rao Bound

Zhiyong Gu, Jiancheng Lai, Wang Chunyong, Yan Wei, Yunjing Ji, and zhenhua li

Doc ID: 336114 Received 17 Jul 2018; Accepted 30 Sep 2018; Posted 29 Oct 2018  View: PDF

Abstract: The waveform fitting technique has been a prevailing method for accurate extraction of the range of objects fromthe observed signal. Exploration of range precision then became a significant research to evaluate the performanceof the technique with the corruption of noise. In this paper, we derive analytical solution of themaximum-likelihood estimation (MLE) for the Gaussian model as the probability of density function (PDF) of therange estimator. The variance of the linear version of the PDF is consistent with the Cramer-Rao bound (CRB).Thus, the variance of the PDF is regarded as the theoretical range precision (TRP) compared with the CRB. Theverification results show the TRP can perfectly describe the variance of the simulation data while the CRB providesa lower bound. At a higher signal to noise ratio (SNR), both the TRP and CRB have the ability to provide an accuratedescription of the range precision. At a lower SNR, the TRP still perform well while the CRB is too loose to boundthe variance on the unbiased estimation.

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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