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Accepted papers to appear in an upcoming issue

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On the use of deep neural networks in opticalcommunications

Sanjaya Lohani, Erin Knutson, Matthew O'Donnell, Sean Huver, and Ryan Glasser

Doc ID: 318573 Received 04 Jan 2018; Accepted 20 Apr 2018; Posted 20 Apr 2018  View: PDF

Abstract: Information transfer rates in optical communications may be dramatically increased by making use ofspatially non-Gaussian states of light. Here we demonstrate the ability of deep neural networks to classifynumerically-generated, noisy Laguerre-Gauss modes of up to 100 quanta of orbital angular momentumwith near-unity fidelity. The scheme relies only on the intensity profile of the detected modes, allowingfor considerable simplification of current measurement schemes required to sort the states containingincreasing degrees of orbital angular momentum. We also present results that show the strength of deepneural networks in the classification of experimental superpositions of Laguerre-Gauss modes when thenetworks are trained solely using simulated images. It is anticipated that these results will allow for anenhancement of current optical communications technologies.

Shape reconstruction based on Zero-curl gradient fieldestimation in fringe reflection technique

Xiaoli Jing, Haobo cheng, yongfu wen, Kun Gao, Huaying Wang, and Hao Yang

Doc ID: 322667 Received 06 Feb 2018; Accepted 19 Apr 2018; Posted 20 Apr 2018  View: PDF

Abstract: A novel shape reconstruction method based on zero-curl gradient field estimation is presented in this paper. Zerocurlfield estimation makes the most of curl information to obtain the ideal gradient data, and achieves thereconstruction with quality map path integration method. In the estimation process, an algebraic approach isadopted to enforce integrability, which maintains the local information friendly. Moreover, we use the residualgradients of surface obtained from Southwell zonal reconstruction algorithm as the raw gradient data in zero-curlfield estimation, which has a stable tradeoff between smoothness and local shape confinement. The performance ofthe proposed method over antinoise capability is discussed and demonstrated by the simulations. Themeasurement experiment of an ultraprecision sphere mirror identifies the validity over general shapes, and thereconstruction results of hyperbolic surface with local shape map demonstrates the better performance on localdetails retention. Therefore, this method performs well in handling complex objects with local mutation regionsand high accuracy requirement of local information in practical measurement.

Design of a portable phantom device to simulate tissueoxygenation and blood perfusion

Xiang Lv, Hongyu Chen, Guangli Liu, Shuwei Shen, Qiang Wu, Chuanzhen Hu, Jialuo Li, Erbao Dong, and Ronald Xu

Doc ID: 322890 Received 13 Feb 2018; Accepted 19 Apr 2018; Posted 19 Apr 2018  View: PDF

Abstract: We propose a portable phantom system for calibration and validation of medical optical devices in a clinical setting. Thephantom system comprises a perfusion module and an exchangeable tissue-simulating phantom that simulates tissueoxygenation and blood perfusion. The perfusion module consists of a peristaltic pump, two liquid storage units, and twopressure suppressors. The tissue-simulating phantom is fabricated by a three-dimensional (3D) printing process withmicrochannels embedded to simulate blood vessels. Optical scattering and absorption properties of biologic tissue aresimulated by mixing graphite powder and titanium dioxide powder with clear photoreactive resin at specific ratios.Tissue oxygen saturation (StO2) and blood perfusion are simulated by circulating the mixture of blood and intralipid atdifferent oxygenation levels and flow rates. A house-made multimodal imaging system that combines multispectralimaging and laser speckle imaging are used for non-invasive detection of phantom oxygenation and perfusion, and themeasurements are compared with those of a commercial Moor device as well as numerical simulation. By acquiringmultimodal imaging data from one phantom and applying the calibration factors in different settings, we demonstratethe technical feasibility to calibrate optical devices for consistent measurements. By simulating retina tissue vasculatureand acquiring functional images at different tissue oxygenation and blood perfusion levels, we demonstrate the clinicalpotential to simulate tissue anomalies. Our experiments imply the clinical potential of a portable, low cost, and traceablephantom standard to calibrate and validate medical optical devices for improved performance.

Rapid optical imaging of polycrystalline materialstructure

Alexander Grigorev and Elena Cherkesova

Doc ID: 320506 Received 23 Jan 2018; Accepted 18 Apr 2018; Posted 19 Apr 2018  View: PDF

Abstract: The physical properties of polycrystalline materials that are widely used in various optical applications are determinedby their structure, wherein grain size and form and grain boundaries play a crucial role. Currently, there is no simpleand fast method to generate a direct image of polycrystalline material structures. In this study, we propose a method fordirect optical imaging of a crystalline material structure based on the difference between the optical properties of thegrains and grain boundaries near the fundamental absorption edge of the material. Our results indicate the possibleutility of the method in diverse imaging applications.

Measurement of 3D wavefronts using theIchikawa-Lohmann-Takeda Solution to the IrradianceTransport Equation

Jesús Arriaga Hernández, Fermin Granados, and Alejandro Cornejo-Rodriguez

Doc ID: 322739 Received 13 Feb 2018; Accepted 18 Apr 2018; Posted 19 Apr 2018  View: PDF

Abstract: In this paper, we use the Irradiance Transport Equation and the Fourier transform-based experimentalsolution given by Ichikawa-Lohmann-Takeda. We analyze experimental factors such as the digital filter,the introduced error for the rotation and period of the Ronchi ruling, and new method is demonstratedfor the measurement of 3D wavefront information.

Correction of phase-delay distortion for α-β circularscanning

Jian Liu, Xiaoyu You, Yuhang Wang, Liu Chenguang, and Jiubin Tan

Doc ID: 321025 Received 30 Jan 2018; Accepted 17 Apr 2018; Posted 18 Apr 2018  View: PDF

Abstract: α-β circular scanning with a large scanning field of view and high reliability can be widely applied in laser scanningimaging systems and laser processing. However, mechanical inertia of the galvanometers introduces phase delayand ultimately leads to scanning distortions in α-β circular scanning in both constant angular velocity scanning(CAVS) and constant line velocity scanning (CLVS). To compensate for the phase-delay distortions, two correctionmodels are respectively proposed for CAVS and CLVS, which utilize phase-frequency relationships based on thegalvanometer’s transfer function. Experimental results show that the presented models can effectively correctrotation distortion in CAVS and tortuosity distortion in CLVS. The correction of phase-delay distortion can improvethe image quality and refine positioning accuracy in laser scanning systems.

Synchronization of pairs of nanosecond pulses from a laser with two gain crystals pumped with two different sources.

Daniel Staufert and Roger Cudney

Doc ID: 323424 Received 16 Feb 2018; Accepted 17 Apr 2018; Posted 18 Apr 2018  View: PDF

Abstract: We report a laser that emits two Q-switched pulses, one at 1.047 µm and the other at 1.064 µm, generated by a Nd:YLF and a Nd:YVO4, respectively. The crystals are pumped by two fiber coupled diode lasers (808 nm and 880 nm); the delay between the pulses can be controlled by adjusting the power of the pumps. Two kinds of Q-switching techniques are reported, passive (Cr:YAG saturable absorber) and active (electro-optic modulator). We model both the active and passive Q-switching and make a comparison between numerical simulations and experiments. We show experimentally and theoretically that in both cases the pulses can be synchronized; however, the stability of the synchronization (sensitivity to pump power fluctuations) is better for active than for passive Q-switching. We also report that under certain experimental conditions a third wavelength is obtained, 1156 nm, which corresponds to the first Stokes shift of the 1047 nm pulse produced by stimulated Raman scattering from the Nd:YVO4 crystal.

Temperature-independent hygrometry by usingmicromachined Photonic Crystal Fiber

Pan Zhang, Hang-Zhou Yang, Kok-Sing Lim, Harith Ahmad, Qiangzhou Rong, Qin Tian, and Ding Zi

Doc ID: 319542 Received 10 Jan 2018; Accepted 17 Apr 2018; Posted 19 Apr 2018  View: PDF

Abstract: An in-fiber Mach-Zehnder interferometer (MZI) is proposed and experimentally demonstrated for relativehumidity and temperature measurements. The MZI is formed by a grapefruit-shaped photonic crystal fiber (G-PCF)cascaded with a short section of multimode fiber which serves as a mode coupler.To enhance sensitivity tohumidity, femtosecond laser micromachining was performed to remove a portion of cladding of G-PCF to expose itscore to the ambient medium. The output interference spectrum is Fast Fourier Transformed (FFT) to produce aspatial frequency spectrum that describe the intensity composition of the cladding modes in the MZI. In ourinvestigation, it was observed that the interference dip intensity has a sensitivity of –0.077dB/%RH to the changeof relative humidity in the range of 25%–80%RH whereas the dip wavelength has a temperature sensitivity of~3.3pm/°C in the range of 25°C to 70°C. In addition, the dip intensity was insensitive to temperature. Thesecharacteristics have provided a convenience in eliminating temperature cross-talk and achieving accuratehumidity measurement.

Dependence of temperature and far-field beamquality on substrate thickness of spectral beamcombining grating with 13.4kW/cm2 laser irradiation

Jiao Xu, Junming Chen, Peng Chen, yonglu wang, Yibing Zhang, Fanyu Kong, jin yunxia, and Jianda Shao

Doc ID: 325067 Received 06 Mar 2018; Accepted 17 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: In previous research, the thermal distortion and far-field beam quality of spectral beam combining grating wereanalyzed by theory and experiment under the irradiation of high-power continuous-wave (CW) laser. It wasconcluded that the thermal expansion of the substrate was the main cause of the grating distortion and decrease inthe beam quality. However, there was no further study to determine a method to decrease the heat deposition onthe grating surface and far-field beam quality factor, M2. In this paper, we theoretically simulate the influence of thesubstrate thickness on the temperature field distribution and far-field beam quality of a multilayer dielectricgrating. An experimental setup is proposed to verify the theoretical calculations. The experimental results are ingood agreement with the calculations. The conclusions indicate that the temperature rise of the grating and M2, areeffectively reduced by increasing the thickness of the substrate.

Investigation of Index Change in Compression Moldingof As40Se50S10 Chalcogenide Glass

Lin Zhang, Wenchen Zhou, Neil Naples, and Allen Yi

Doc ID: 317904 Received 18 Dec 2017; Accepted 17 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: Chalcogenide glasses are emerging as alternative materials for low-cost and high-volume glass molding process forinfrared optics. In precision glass molding, it is well-documented that the refractive index variation in the moldedelements can lead to substantial amount of aberrations. The variation has such a significant effect that the opticaldesigns with molded lenses need to carefully consider and compensate for index variation to achieve targetedoptical performance. This research is aimed to evaluate the refractive index change of a chalcogenide glass duringmolding process by both finite element method based simulation and optical experiment. First, a set of moldinserts were designed and machined by high-speed single-point diamond milling. The structure of the lower moldinsert was semi-closed and detachable, which facilitated the molded infrared prisms release from the mold.Second, finite element method simulation was implemented to predict the refractive index change during thecooling phase by using the Tool-Narayanaswamy-Moynihan model for structural relaxation behavior. It wasconfirmed that refractive index variation occurred inside the molded wedge due to rapid thermal cycling. However,the amount of variation in the molded element indicates that the refractive index change during the moldingprocess was not uniform. Finally, the refractive index of the molded wedge was measured by an optical setup. Theresults showed that the index shift is approximately -0.0226 for As40Se50S10, which matched the numerical result bysimulation. Compared with oxide glass materials, the index drop of As40Se50S10 has a significant effect on opticalperformance of molded optics and the post-molding refractive index should be taken into account in the opticaldesign. In summary, the results presented in this article provided reliable references for refractive index change ofAs40Se50S10 glass, crucial for precision glass molding or similar applications.

Improved space object detection using short exposureimage data with daylight background

David Becker and Stephen Cain

Doc ID: 319122 Received 05 Jan 2018; Accepted 16 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: Space object detection is of great importance in the highly dependent yet competitive and congested space domain.Detection algorithms employed play a crucial role in fulfilling the detection component in the space situationalawareness mission to detect, track, characterize and catalog unknown space objects. Many current space detectionalgorithms use a matched filter or a spatial correlator on long exposure data to make a detection decision at a singlepixel point of a spatial image based on the assumption that the data follows a Gaussian distribution. Long exposureimaging is critical to detection performance in these algorithms, however if imaging under daylight conditions itbecomes necessary to create a long exposure image as the sum of many short exposure images. This paper explores thepotential to increase detection capabilities of small and dim space objects in a stack of short exposure images dominatedwith a bright background. The algorithm proposed in this paper improves the traditional stack and average method offorming a long exposure image by selectively removing short exposure frames of data that do not positively contributeto the overall signal to noise ratio of the averaged image. The performance of the algorithm is compared to a traditionalmatched filter detector using data generated in MATLAB as well as laboratory collected data. The results are illustratedon a receiver operating characteristic curve to highlight the increased probability of detection associated with theproposed algorithm..

Gaussian probe beam with high spherical aberrationfor glucose concentration measurement

Etna Yáñez, Moisés Cywiak, and juan franco

Doc ID: 320836 Received 29 Jan 2018; Accepted 16 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: We demonstrate that an optical probe beam with high spherical aberration used for glucose concentrationmeasurements gives better sensitivity compared to a probe beam free of aberrations, under similar conditions. Weplace a singlet focusing lens at a large distance from a laser source with a Gaussian intensity profile to obtain aspherically aberrated probe beam with negligible truncation. The aberrated probe beam propagates through atransparent liquid sample. Intensity profiles of the transmitted beam are recorded by means of a homodyneprofiler to perform the glucose concentration measurements accurately.

Ultrashort polarization beam splitter based on liquidfilled dual-core photonic crystal fiber

jianshuai wang, Li Pei, Sijun Weng, Liangying Wu, Jing Li, and Tigang NIng

Doc ID: 324941 Received 27 Feb 2018; Accepted 16 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: An ultrashort polarization beam splitter (PBS) is proposed based on liquid-filled dual-core photonic crystal fiber(DCPCF). The two cores of DCPCF are formed by two side elliptical holes and a central circular hole in horizontaldirection. The properties of the PBS is analyzed first with a non-filled DCPCF by Finite Element Method (FEM).Then, the performances of the PBS are discussed when the DCPCF is filled with liquids in the central hole. As aresult, an ultrashort PBS is realized with a length of 78 μm when glycerol solution, with a concentration of 37%, isfilled in the central hole. In this case, an extinction ratio (ER) of 87 dB is obtained at 1550 nm wavelength. Thesignificantly short device shows a great advantage over being integrated in ultra-compact optical systems.

Optimization of All-Dielectric Structures for Color Generation

Alma González-Alcalde, Rafael Salas-Montiel, Habib Mohamad, alain morand, Sylvain Blaize, and Demetrio Macias

Doc ID: 324968 Received 27 Feb 2018; Accepted 16 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: In this work, we propose an inversion scheme to tailor the chromatic response of an all-dielectric structure. To this end, we couple, through a previously defined objective functional involving the concept of color difference, a forward solver with an optimization algorithm. The former is based on the Differential Method (DM), whereas the latter is based on Particles Swarm Optimization (PSO). The optimal geometrical parameters of the structure that generates a specific color are obtained through the solution of an Approximation Problem. We illustrate the performance of our inversion scheme through some examples and discuss its limitations and potential applications.

Single-Frequency 3D Synthetic Aperture Imaging withDynamic Metasurface Antennas

Michael Boyarsky, Timothy Sleasman, Laura Maria Pulido Mancera, Aaron Diebold, Mohammadreza F. Imani, and David Smith

Doc ID: 315293 Received 08 Dec 2017; Accepted 16 Apr 2018; Posted 16 Apr 2018  View: PDF

Abstract: Through aperture synthesis, an electrically small antenna can be used to form a high-resolution imagingsystem capable of reconstructing three-dimensional (3D) scenes. However, the large spectral bandwidthtypically required in synthetic aperture radar (SAR) systems to resolve objects in range often requirescostly and complex RF components. We present here an alternative approach based on a hybrid imagingsystem that combines a dynamically reconfigurable aperture with synthetic aperture techniques, demonstratingthe capability to resolve objects in three dimensions (3D) with measurements taken at a singlefrequency. At the core of our imaging system are two metasurface apertures, both of which consist ofa linear array of metamaterial irises that couple to a common waveguide feed. Each metamaterial irishas integrated within it a diode that can be biased so as to switch the element on (radiating) or off (nonradiating),such that the metasurface antenna can produce distinct radiation profiles corresponding todifferent on/off patterns of the metamaterial element array. The electrically-large size of the metasurfaceapertures enables resolution in range and one cross-range dimension, while aperture synthesis providesresolution in the other cross-range dimension. The demonstrated imaging capabilities of this system representa step forward in the development of low-cost, high performance, 3D microwave imaging systems.

A wide field-of-view crossed Dragone optical systemusing the anamorphic aspherical surfaces

Shingo Kashima, Masashi Hazumi, Hiroaki Imada, Nobuhiko Katayama, Tomtoake Matsumura, yutaro sekimoto, and Hajime Sugai

Doc ID: 315704 Received 13 Dec 2017; Accepted 16 Apr 2018; Posted 16 Apr 2018  View: PDF

Abstract: A side-fed crossed Dragone telescope provides a wide field-of-view. This type of a telescope is commonlyemployed in the measurement of cosmic microwave background (CMB) polarization, which requires animage-space telecentric telescope with a large focal plane over broadband coverage. We report the designof the wide field-of-view crossed Dragone optical system using the anamorphic aspherical surfaces withcorrection terms up to the 10th order. We achieved the Strehl ratio larger than 0.95 over 32 18 squaredegrees at 150 GHz. This design is an image-space telecentric and fully diffraction-limited system below400 GHz. We discuss the optical performance in the uniformity of the axially symmetric point spreadfunction and telecentricity over the field-of-view. We also address the analysis to evaluate the polarizationproperties, including the instrumental polarization, extinction rate, and polarization angle rotation. Thiswork is a part of programs to design a compact multi-color wide field-of-view telescope for LiteBIRD,which is a next generation CMB polarization satellite.

Three-dimensional shape measurement using astructured light system with dual projectors

Chufan Jiang, Beatrice Lim, and Song Zhang

Doc ID: 326460 Received 20 Mar 2018; Accepted 16 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: This paper introduces a structured light system with two projectors and one camera for three-dimensional(3D) shape measurement to alleviate problems created by a single projector such as the shadow problem.In particular, we developed (1) a system calibration framework that can accurately calibrate each suchcamera-projector system; (2) a residual error correction method based on the system error function; and(3) a data fusion method utilizing the angle between the projection direction and surface normal. Experimentalresults demonstrate that the proposed dual-projector structured light system improves themeasurement accuracy besides extending the measurement range of a single projector system.

Airborne Lidar Detection and Mapping of Invasive LakeTrout in Yellowstone Lake

michael Roddewig, James Churnside, F. Hauer, Jacob Williams, Patricia Bigelow, Todd Koel, and Joseph Shaw

Doc ID: 323171 Received 16 Feb 2018; Accepted 16 Apr 2018; Posted 16 Apr 2018  View: PDF

Abstract: The use of airborne lidar to survey fisheries has not yet been extensively applied in freshwater environments.In this study, we investigated the applicability of this technology to identifying invasive lake trout(Salvelinus namaycush) in Yellowstone Lake, Yellowstone National Park, USA. Results of experimentaltrials conducted in 2004 and in 2015-16 provided lidar data that identified groups of fish coherent withcurrent knowledge and models of lake trout spawning sites, and one identified site was later confirmedto have lake trout.

Stokes polarimeter performance: general noise model and analysis

Nathan Hagen and Yukitoshi Otani

Doc ID: 313742 Received 17 Nov 2017; Accepted 16 Apr 2018; Posted 20 Apr 2018  View: PDF

Abstract: We calculate the photometric Stokes parameter covariance matrices and SNRs estimated by polarimeters exposed to general noise distributions such as mixed Poisson-Gaussian noise. The measurement model includes the effects of optical losses and detector quantum efficiency, enabling quantitative comparison of instruments that have different photometric efficiencies. We demonstrate this capability by comparing the performance of many common polarimeter configurations, including diattenuator-based systems such as Azzam's four-detector polarimeter [Opt. Lett. 10: 309 (1985)] and Kudenov's stacked photovoltaic polarimeter [Opt. Express 24: 14737 (2016)]. Working with the full covariance matrix under mixed Poisson-Gaussian noise, we also show that instruments optimized under assumptions of Gaussian noise simultaneously exhibit optimal behavior under Poisson noise.

Effects of aberrations on effective point spreadfunction in STED microscopy

Yanghui Li, Hui Zhou, Xiaoyu Liu, Yuxue Li, and Le Wang

Doc ID: 325173 Received 01 Mar 2018; Accepted 15 Apr 2018; Posted 16 Apr 2018  View: PDF

Abstract: Like all other imaging techniques, stimulated emission depletion (STED) microscopy suffers from aberrations.While their effects on the depletion patterns have been explicitly investigated, the study on how aberrations affectthe effective point-spread function (PSF) in STED microscopy is still missing. On the other hand, for STEDresearchers, this study is beneficial, as it directly bridges the image qualities and the aberrations. In this paper, wequantitatively analyze the effects of primary aberrations, including astigmatism, coma, trefoil, and sphericalaberration, in two-dimensional (2D) and three-dimensional (3D) STED microscopy, and further discuss thecorresponding aberration tolerance. Specifically, attention is given to the modification of the shape, the size, andthe peak intensity of the effective PSF in the presence of these aberrations.

A synthetic model of nonlinearity errors in laserheterodyne interferometry

Hongfang Chen, Bo Jiang, and Zhaoyao Shi

Doc ID: 326486 Received 23 Mar 2018; Accepted 15 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: The development of laser heterodyne interferometry raises the requirements of measurement resolution andaccuracy. However, periodic nonlinearity errors mainly suppress the accuracy of laser heterodyne interferometry.Based on the generation mechanism of nonlinearity errors, the sources of nonlinearity errors in laser heterodyneinterferometry are firstly analyzed in this paper. Then, a synthetic model is established to analyze the influences ofvarious nonlinearity error sources on the first and second harmonic nonlinearity errors. The first harmonicnonlinearity errors can be reduced and suppressed by adjusting the orientation error of optical elements inheterodyne interferometer. Furthermore, the azimuthal misalignment of the polarization beam splitter (PBS) isthe main source of the second harmonic nonlinearity errors. Therefore, when in heterodyne interferometer, theazimuthal misalignment of the PBS should be avoided as possible. This study provides theoretical basis forreducing and compensating nonlinearity errors in laser heterodyne interferometer.

Laser coarse-fine coupling tracking by cascadedrotation Risley-prism pairs

Anhu Li, Wansong Sun, Xingsheng Liu, and Wei Gong

Doc ID: 322533 Received 12 Feb 2018; Accepted 15 Apr 2018; Posted 16 Apr 2018  View: PDF

Abstract: Rotation Risley prisms are increasingly used for laser tracking due to high precision and good dynamicperformance. In this paper, a novel laser coarse-fine tracking method based on two pairs of rotation Risley prismsis proposed to perform the forward and inverse tracking function. The second pair of rotation Risley prisms withnarrower wedge angle can achieve higher precision tracking with narrower FOV than the first one, which can wellenrich the coarse-fine coupling tracking trajectory patterns. Moreover, an inverse algorithm based on the two-stepmethod and the Newton’s iterative method is applied to solve the inverse issue for laser coarse-fine couplingtracking. Two cases further demonstrate that the motion switching strategy executed with the inverse solutionscan steer the beam to track the desired motion trajectory. An experiment validates the availability of the cascadedrotation Risley-prism pairs to perform the laser coarse-fine coupling tracking function.

Linewidth in saturated absorption spectroscopy for two level atoms: an empirical formula

Geol Moon and Heung-Ryoul Noh

Doc ID: 322582 Received 05 Feb 2018; Accepted 15 Apr 2018; Posted 16 Apr 2018  View: PDF

Abstract: We present an empirical formula for linewidth in saturated absorption spectroscopy for two-level atoms, taking the coherence term in the Doppler-broadened limit into account. The full width at half maximum is obtained as $(1+(1+a s_0 )^b )\gamma_t$, where $s_0$ is the on-resonance saturation parameter, $\gamma_t$ is the transverse decay rate, and $a$ and $b$ are the parameters that depend on $\gamma_t$. We find that as $\gamma_t$ increases, $a$ and $b$ approach 1 and 1/2, respectively. These are the typical values in the case without the coherence term.

Partial saturation aided resolution enhancement fordigital holography

Zhilong Jiang, Xingchen Pan, Yan Kong, weiying qian, Shouyu Wang, and Liu Cheng

Doc ID: 320617 Received 24 Jan 2018; Accepted 14 Apr 2018; Posted 16 Apr 2018  View: PDF

Abstract: Because of the limited dynamic range of common detector, high frequency components weaker than the thresholdof the detector used are lost in digital holography even with the aid of coherent diffraction imaging (CDI) basediterative computation, and this makes digital holography (DH) less preferable for many interesting applications. Toovercome this problem, the partially saturated diffraction pattern was adopted to enhance the resolution of DHiteratively. Since more high frequency components were retrieved in comparison with our former CDI based digitalholographic method, the resolution of DH was improved further. The feasibility of the proposed method isdemonstrated both numerically and experimentally.

Design and analysis for a bend-resistant and largemode-area photonic crystal fiber with hybrid-cladding

Yan Qin, Yang Huajun, Ping Jiang, Fengji Gui, Wei Caiyang, and Biao Cao

Doc ID: 320454 Received 01 Feb 2018; Accepted 13 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: In this paper, an asymmetric large-mode-area photonic crystal fiber (LMA-PCF) with low bending loss at smallerbending radius is designed. The finite-element-method (FEM) with perfectly matched layer boundary (PML) is usedto analyze the performance of the photonic crystal fiber. To achieve LMA-PCF with low bending loss, the air holeswith double lattice constants and different sizes at the core are designed. Numerical results show that thisstructure can achieve low bending loss and large mode area with a smaller bending radius at the wavelength of1.55 μm. The effective mode area (EMA) of the fundamental is larger than 1000 μm2 when bending radius ≥10 cm.The bending loss of fundamental mode is just 0.0113 dB/m and the difference between the fundamental and highordermode of the bending loss is larger than 103 when bending radius is 10cm. Simulation results show this novelphotonic crystal fiber can achieve large mode area and have effective single-mode operation when bendingorientation angle ranging in ±110°. This novel photonic crystal has potential application in high-power fiber lasers.

TM01 mode in cylindrical hybrid plasmonic waveguidewith large propagation length

Ji Xu, Nannan Shi, Yilin Chen, Xinyi Lu, Hongyu Wei, Yuqing Lu, Ning Liu, Baifu Zhang, and Jin Wang

Doc ID: 325055 Received 28 Feb 2018; Accepted 13 Apr 2018; Posted 16 Apr 2018  View: PDF

Abstract: This study reports a cylindrical hybrid plasmonic waveguide (CHPW) consisting of a high-index dielectric core, asandwiched low-index dielectric layer and a metal cladding. The CHPW supports TM01 mode with radially polarizedtransverse component of electric field. Optical fields can be significantly enhanced in the sandwiched low-indexdielectric region with nanoscale thickness down to 5 nm, and very tight mode confinement with the same order ofnormalized mode area compared to that of the plasmonic waveguide is achieved. Moreover, the mode propagationloss is well compensated by adjusting the dimension of the waveguide to obtain longer propagation distance. Thecalculated figure of merit reaches a value of several times larger than that in the similarly reported structure. Theresults indicate that, this novel type of hybrid structure can support the limited propagation of radially polarizedmode with good confinement and low loss, consummate the whole system of manipulating the cylindrical vectorbeams, and show great potential of applications for various integrated nano-photonic devices.

Analyzing characteristics of spiral vector beamsgenerated by mixing of orthogonal LP11 modes in fewmodeoptical fiber

C Hari Krishna and SOURABH ROY

Doc ID: 320800 Received 26 Jan 2018; Accepted 12 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: We have demonstrated a method for the generation of spiral vector beams using a few-mode optical fiber. Thebeams are generated due to the combination of orthogonal linearly polarized modes with tilted polarization vectorin the few-mode optical fiber. The excitation of these modes is controlled by the incident state of polarization andcoupling conditions at the input end of the fiber. The beams with clockwise and counter clockwise nature of spiralpolarization are generated and switching between them is demonstrated. The obtained results emphasize thestrong dependency of polarization of generated spiral vector beams and other orthogonal linearly polarized modeson input state of polarization. The simulated results of mode mixing are verified experimentally with goodagreement.


Ying Zhong Tian, Haoyang CUI, zhiyan pan, jiaorong liu, Shouchen YANG, lilan liu, wenbin wang, and Long Li

Doc ID: 321266 Received 01 Feb 2018; Accepted 12 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: In the multi-focus microscopic image measurement method, the distortion of three-dimensional reconstruction model has always been an important factor affecting the measurement result. In spatial domains, the focus measure algorithm is based on the gradient change of the pixel point to determine the degree of focus of the pixel. So it will be difficult to accurately extract the focus of the pixel in the color difference is not obvious areas, resulting in three-dimensional model distortion. According to the optical principle, the high-frequency coefficients of the clear image are larger than the high-frequency coefficients of the blurred image. Based on the characteristic, this paper proposes a new multi-focus microscopic image three-dimensional reconstruction algorithm using non-subsampled wavelet transform (NSWT). The non-subsampled wavelet transform does not consider the downsampling in wavelet decomposition and has translational invariance. Therefore, the wavelet transform value of each pixel can be calculated in the image, so the high-frequency coefficient of each pixel can be obtained, then the convolution calculation is performed on the high-frequency coefficients of the pixel points in the fixed window as the focus measure value of the pixel point. Compared with the traditional algorithm, the algorithm proposed in this paper can show better unimodal and anti-noise performance on the focusing measure curve. In this paper, the reconstruction of the experimental object is Alicona standard block triangular and semi-cylindrical. The proposed algorithm and the traditional algorithm for comprehensive measure using root mean square error, peak signal to noise ratio and correlation coefficient as the measure index. The experimental results and comparative analysis prove the correctness of the proposed algorithm and enable more accurate reconstruction of three-dimensional models based on multi-focus microscopic images.

High-speed focal-distance-modulated fibre-coupledconfocal sensor for coordinate measuring systems

Tino Hausotte, Adreas Gröschl, and Janik Schaude

Doc ID: 322889 Received 12 Feb 2018; Accepted 12 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: This article presents a new robust, precise, high-frequency focal-distance-modulated confocal point sensor for probingin coordinate measuring systems (CMS). While maintaining the known advantages of the confocal measurementprinciple, the sensor represents an innovative combination of a fibre-coupled confocal illumination and detection with atuneable, acoustically driven gradient-index fluid lens (TAG lens) for modulation of the focus distance and a novel signalprocessing utilizing a lock-in amplifier. The new arrangement is able to achieve an approximately linear characteristiccurve for the optimised feedback control of the CMS in scanning sample mode. This article emphasises the opticalapplication and the signal processing of the setup.

Deep-learning-generated holography

Ryoichi Horisaki, Takagi Ryosuke, and Jun Tanida

Doc ID: 323038 Received 12 Feb 2018; Accepted 12 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: We present a method for computer-generated holography based on deep learning. The inverse process of light propagation is regressed with a number of computationally generated speckle datasets. This method enables non-iterative calculation of computer-generated holograms (CGHs). The proposed method was experimentally verified with a phase-only CGH.

Detection of iron atoms by emission spectroscopy and laser induced fluorescence in solid propellant flames

Gautier Vilmart, Nelly Dorval, Mikael Orain, Dominique Lambert, Robin Devillers, Yves Fabignon, Brigitte Attal-Tretout, and Alexandre Bresson

Doc ID: 323406 Received 15 Feb 2018; Accepted 12 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: Planar laser-induced fluorescence on atomic iron is investigated in this paper and a measurement strategy is proposed to monitor the fluorescence of iron atoms with a good sensitivity. A model is proposed to fit the experimental fluorescence spectra and a good agreement is found between simulated and experimental spectra. Emission and laser induced fluorescence measurements are performed in the flames of ammonium perchlorate composite propellants containing iron-based catalysts. Fluorescence signal from iron atoms after excitation at 248 nm is observed for the first time in propellant flames. Images of the spatial distribution of iron atoms are recorded in the flame in which turbulent structures are generated. Iron fluorescence is detected up to 1.0 MPa, which opens the way to application in propellant combustion.

Polychromatic wave-optics models for image-plane speckle. 1. Well-resolved objects

Noah Van Zandt, Jack McCrae, Mark Spencer, Michael Steinbock, Milo Hyde, and Steven Fiorino

Doc ID: 323482 Received 20 Feb 2018; Accepted 12 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: Polychromatic laser light can reduce speckle noise in wavefront-sensing and imaging applications that use direct-detection schemes. To help quantify the achievable reduction in speckle, this paper investigates the accuracy and numerical efficiency of three separate wave-optics methods. Each method simulates the active illumination of extended objects with polychromatic laser light. In turn, this paper uses the Monte-Carlo method, the depth-slicing method, and the spectral-slicing method, respectively, to simulate the laser-object interaction. The limitations and sampling requirements of all three methods are discussed. Further, the numerical efficiencies of the methods are compared over a range of conditions. The Monte-Carlo method is found to be the most efficient, while spectral slicing is more efficient than depth slicing for well-resolved objects. Finally, Hu’s theory is used to quantify method accuracy when possible (i.e., for well-resolved objects). In general, the theory compares favorably with the simulation methods.

Polychromatic wave-optics models for image-planespeckle. 2. Unresolved objects

Noah Van Zandt, Mark Spencer, Michael Steinbock, Brian Anderson, Milo Hyde, and Steven Fiorino

Doc ID: 323486 Received 21 Feb 2018; Accepted 12 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: Polychromatic laser light can reduce speckle noise in many wavefront-sensing and imaging applications. To helpquantify the achievable reduction in speckle noise, this study investigates the accuracy of three polychromaticwave-optics models under the specific conditions of an unresolved object. Because existing theory assumes a wellresolvedobject, laboratory experiments are used to evaluate model accuracy. The three models use Monte-Carloaveraging, depth slicing, and spectral slicing, respectively, to simulate the laser-object interaction. The experimentsinvolve spoiling the temporal coherence of laser light via a fiber-based, electro-optic modulator. After the lightscatters off of the rough object, speckle statistics are measured. The Monte-Carlo method is found to be highlyinaccurate, while depth-slicing error peaks at 7.8% but is generally much lower in comparison. The spectral-slicingmethod is the most accurate, always producing results within the error bounds of the experiment.

Compact InGaAsP/InP Nonblocking 4×4 Trenchcouplerbased Mach-Zehnder Photonic Switch Fabric

Ke Liu, Le Wang, Chenglong Zhang, Qingyu Ma, and Bing Qi

Doc ID: 318156 Received 20 Dec 2017; Accepted 12 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: The existing photonic switch matrices usually show the drawbacks of either large footprint or high crosstalk. Herewe propose a compact InGaAsP/InP rearrangeable nonblocking 4×4 photonic switch fabric based on 2×2 Mach-Zehnder interferometer (MZI) switch elements in a Benes architecture. Each switch element consists of twofrustrated total internal reflection (TIR) couplers and TIR mirrors serving as 90° waveguide bends, forming thesquare layout configuration of the 2×2 MZI switches. We investigate the design parameters of the switch elementand 4×4 photonic switch matrix by using finite difference time domain and transfer matrix methods, respectively.Our analysis results show that the proposed device exhibits an ultra-compact chip size of ~ 340 μm × 120 μm, theminimum cross-talk of - dB in the 1.5~1.6 μm wavelength range, the total insertion loss of ~3.9 dB, the lowelectrical energy of ~0.4 pJ/bit, and an operation speed up to 50 GHz. Experimentally we can demonstrate thefeasibility of fabricating 2×2 MZI switches and an operational low-loss trench coupler. The enabling component ofthe 2×2 MZI switch can scale its pattern in the two-dimensional directions. This as-formed compact 4×4 switchfabric can be potentially applied in large-scale InP-based photonic integrated circuits.

Efficient high power narrow linewidth 1.9 μm fiberhydrogen Raman Amplifier

zhixian li, wei huang, yulong chui, and Zefeng Wang

Doc ID: 318437 Received 26 Dec 2017; Accepted 12 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: We report here an efficient, high power, narrow linewidth 1.9 μm gas Raman amplifier by a hydrogen-filled hollowcorefiber. A 1.9 μm narrow linewidth CW seed laser is coupled into the hollow-core fiber together with a highpower pulsed 1064 nm MOPA laser through a shortpass dichromic mirror, and then amplified by stimulatedRaman scattering of hydrogen. With 2 m fiber length and 4.5 bar gas pressure, the maximum average 1908 nmStokes power of 570 mW is obtained, a record average power level for such experiments. The maximum peakpower is about 50 kW, the linewidth is about 1 GHz, and the quantum efficiency is about 51%. This work hasdemonstrated the potential to get high average power gas Raman laser in hollow-core fiber, and further providesthe possibility to achieve high average power 4 μm mid-infrared fiber laser by cascaded gas SRS with methane.

Design of an ultrasensitive SPR biosensor based on agraphene-MoS2 hybrid structure with MgF2 prism

Yuncai Feng, Youwen Liu, and Jinghua Teng

Doc ID: 321176 Received 31 Jan 2018; Accepted 11 Apr 2018; Posted 12 Apr 2018  View: PDF

Abstract: We propose a new configuration of biosensor based on the graphene-MoS2 hybrid structure by adopting the lowerrefractive index MgF2 prism in order to improve the sensitivity and the figure of merit (FOM). We can obtain anultrasensitive sensor with the values of sensitivity and FOM as high as 540.8°/RIU and 145/RIU, respectively, bymodulating the parameters in the configuration and comparatively choosing different absentee layer material. Theproposed structure is applicable in the realization of an integrated device for the surface plasmon resonance biosensor.

Polari-Metric Learning: A Siamese Approach toLearning Distance Metrics of Algal Mueller MatrixImages

Xianpeng Li, Ran Liao, Hui Ma, Priscilla Leung, and Meng Yan

Doc ID: 321356 Received 02 Feb 2018; Accepted 11 Apr 2018; Posted 12 Apr 2018  View: PDF

Abstract: Polarimetric measurements are becoming increasingly accurate and fast to perform in modern applications.However, analysis on the polarimetric data usually suffers from its high-dimensional nature spatially, temporally orspectrally. This paper associates polarimetric techniques with metric learning algorithms, namely Polari-MetricLearning (PML), by introducing a distance metric learning method called siamese network that aims to learn gooddistance metrics of algal Mueller Matrix images in low-dimensional feature spaces. As an experimental example,12162 Mueller matrix images of eight algal species are measured via a forward Mueller matrix microscope. Eightclassical metric learning algorithms including Principle Component Analysis (PCA), Multidimensional Scaling(MDS), Isometric Feature Mapping (Isomap), t-Distributed Stochastic Neighbor Embedding (t-SNE), LaplacianEigenmaps (LE), Locally Linear Embedding (LLE), Linear Discriminant Analysis (LDA) and Metric Learning to Rank(MLR) are considered, by which the algal Mueller matrix images are mapped to two-dimensional (2D) featurespaces with different distance metrics. Support vector machine (SVM) based holdout sample classificationaccuracies of the 2D feature vectors are provided in a supervised manner for quantitative comparisons of thelow-dimensional distance metrics, including the results of the eight metric learning algorithms and sixteen siamesearchitectures with varying convolution, inception and full connection modules. This study shows that the siameseapproach is an effective metric learning algorithm that can adaptively extract features exhibiting empiricalcorrelations with the fast-axis-orientation dependent and spatially variant algal retardance induced by the algalmicrostructures.

Real-time super-resolved 3D in turbid water using a fast range-gated CMOS camera

Petter Risholm, Jostein Thorstensen, Jens Thielemann, Kristin Kaspersen, Jon Tschudi, Chris Yates, Chris Softley, Igor Abrosimov, Jonathan Alexander, and Karl Henrik Haugholt

Doc ID: 315858 Received 19 Dec 2017; Accepted 11 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: We present a range gated camera system designed for real-time (10Hz) 3D estimation underwater. The system uses a fast-shutter CMOS sensor (1280x1024) customized to facilitate gating with 1.67ns (18 cm in water) delay steps relative to the triggering of a solid-state actively Q-switched 532nm laser. A depth estimation algorithm has been carefully designed to handle the effects of light scattering in water; i.e. forward and backward scattering. The raw range gated signal is carefully filtered to reduce noise while preserving the signal even in the presence of unwanted backscatter. The resulting signal is proportional to the number of photons that is reflected during a small time-unit (range) and objects will show up as peaks in the filtered signal. We present a peak finding algorithm that is robust to unwanted forward scatter peaks and at the same time can pick out distant peaks that are barely higher than peaks caused by sensor and intensity noise. Super-resolution is achieved by fitting a parabola around the peak which we show can provide depth-precision below 1 cm at high signal levels. We show depth estimation results when scanning a range of 8m (typically 1m-9m) at 10Hz. The results are dependent on the water quality. We are capable of estimating depth at distances of over 4.5m attenuation lengths when imaging high albedo targets at low attenuation lengths, and we achieve a depth resolution (σ) ranging from 1cm-9cm depending on signal level.

Research on surface relief optical waveguideaugmented reality display device

Wen Zhang, ZhiFeng Wang, and Jian Xu

Doc ID: 320139 Received 19 Jan 2018; Accepted 11 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: Recently, optical waveguide display device with light weight, high transparent, and full color has becoming moreand more popular in the wearable augmented reality(AR) display application. But existing waveguide displaydevices are less than satisfactory because of the cost, safety and mass production. Therefore, a type of the surfacerelief optical waveguide display device is proposed in the paper. Firstly, the geometrical relationship of waveguidedisplay device structure is confirmed according to the design method of the optical waveguide display device. Then,the influence of the waveguide structure for the image quality is analyzed, and the rationality of the surface reliefwaveguide scheme is verified by simulation. Finally, the prototype of the surface relief optical waveguide displaydevice with polycarbonate materials, field of view (FOV) of 38º, thickness of 4.5mm and transmittance of about80% is fabricated and demonstrated.

Piezo-, elasto- and acousto-optic properties of Tl3AsS4crystals

Bohdan Mytsyk, Taras Kryvyy, Natalya Demyanyshyn, Oksana Mys, Iryna Martynyuk-Lototska, Oleksandr Kokhan, and Rostyslav Vlokh

Doc ID: 323254 Received 13 Feb 2018; Accepted 11 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: Complete matrices of piezo-optic and elasto-optic tensors are experimentally determined for Tl3AsS4 crystals. It isrevealed that the piezo-optic coefficients are very high, ~ 10–11 N/m2 in the order of magnitude. This implies thatTl3AsS4 can be referred to the best piezo-optic materials. The same concerns the elasto-optic coefficients, of whichabsolute values are in the interval 0.28–0.54. It is also found that, at the anisotropic and isotropic interactions withthe slowest transverse and longitudinal acoustic waves, the acousto-optic figure of merit reaches extremely highvalues (1.99×10–12 s3/kg and 9.45×10–13 s3/kg, respectively). In other words, the Tl3AsS4 crystals can be referred toas one of the best acousto-optic materials for the visible and infrared spectral ranges.

No-Reference Stereoscopic Image Quality AssessmentBased on Hue Summation-Difference Mapping Imageand Binocular Joint Mutual Filtering

Jiachen Yang, Kyohoon Sim, Bin Jiang, and Wen Lu

Doc ID: 319393 Received 09 Jan 2018; Accepted 10 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: The no-reference (NR) quality assessment for stereoscopicimage plays a significant role in 3D technology,but it also faces great challenges. In this paper,a novel NR stereo image quality assessment (SIQA)method is proposed. Based on the human visual system(HVS), this method mimics the summation anddifference channels, which considers binocular interactiveperception property, to process the visual information.Specially, the summation and difference imagesare calculated by contrast of hue and luminancein color patches. Meanwhile, considering the interactivefiltering between the left and right viewpoints,this method uses the filtered information as the weightingfactor to integrate the visual information of thesummation and difference channels to form the summationand difference mapping image (SDMI). Then,energy entropy, bivariate generalized gaussian distribution(BGGD) for the joint distribution of SDMIand the depth map (DPM) subband coefficients, andthe local log-euclidean multivariate gaussian descriptor(L2EMG) are detected as the feature descriptors. Supportvector regression (SVR) trained by the features isutilized to predict the quality of stereoscopic images.Experimental results demonstrate that the proposed algorithmachieves high consistency with subjective assessmenton four SIQA databases.

Orientation-dependent fiber-optic displacement sensor using a fiber Bragg grating inscribed in a side-hole fiber

Chen Fengyi, Xue-Guang Qiao, Ruohui Wang, Dan Su, and Qiangzhou Rong

Doc ID: 320015 Received 09 Feb 2018; Accepted 10 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: We propose and experimentally demonstrate an orientation-dependent fiber-optic bending sensor. The sensing probe consists of a fiber Bragg grating (FBG) inscribed in both the fiber core and the surrounding cladding of a section of a side-hole fiber (SHF). We utilized a side-illumination technique using a femtosecond laser to achieve the grating structure formation. The transmission intensities of both resonances are highly sensitive bending of the fiber, and the bending response shows orientation dependence. The surrounding temperature fluctuation causes a wavelength shift, but not an intensity variation. Therefore, the proposed sensor can be employed for simultaneous measurement of bending and temperature.

Fabrication of a silica-based complex-Fouriertransform integrated-optic spatial heterodynespectrometer incorporating 120° optical hybridcouplers

Riki Uda, Kohei Yamaguchi, Kazumasa Takada, and Katsunari Okamoto

Doc ID: 319490 Received 11 Jan 2018; Accepted 10 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: We report the first demonstration of a silica-based planar waveguide spatial heterodyne spectrometerincorporating 120° optical hybrid 3×3 MMI couplers as the output couplers in 32 MZIs which enabled us to derivethe spectrum without use of the previously reported dynamic phase shifting. The free spectral range was 640 GHzand the spectral resolution was 14 GHz. We used a CO2 laser irradiation method to calibrate the light powers fromall the output ports of the couplers and to measure the optical phases and amplitudes at the individual MZIs. Wesolved the resultant system of three linear equations at each MZI and performed a complex Fourier transformationto derive a narrow-band light spectrum. The background noise level of the retrieved spectrum was 0.05 withrespect to the peak even when no window function was applied.

Signature of phase singularities in diffusive regime indisordered waveguide lattices: Interplay andqualitative analysis

Somnath Ghosh

Doc ID: 321287 Received 01 Feb 2018; Accepted 09 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: Co-existence and interplay between mesoscopic light dynamics with singular optics in spatially disorderedwaveguide lattices is reported. Two CW light beams of 1.55 mm operating wavelength are launchedas inputs to 1D waveguide lattices with controllable weak disorder in a complex refractive index profile.Direct observation of phase singularities in the speckle pattern along the length is numerically demonstrated.Quantitative analysis of onset of such singular behavior and diffusive wave propagation is analyzedfor the first time.

Freeform characterization based onnanostructured diffraction gratings

Mohamed Bichra, Thomas Meinecke, Patrick Feßer, Lutz müller, Martin Hoffmann, and Stefan Sinzinger

Doc ID: 318641 Received 03 Jan 2018; Accepted 09 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: The in-line characterization of freeform optical elements during the production cycle is challenging.Recently, we presented a compact sensor setup for the characterization of the wavefront generated byfreeform optical elements in transmission. The sensor is based on a common-path interferometerconsisting of diffractive components and Fourier filtering being adapted to the subsequent numericalpost processing. Additionally, it offers several degrees of freedom for enlarging the measurement rangeof the wavefront gradients. In this contribution, we propose an advanced sensor setup for themeasurement of wavefronts generated by freeform elements in reflection. The main advantage is theuni-axial illumination of the test object and the measuring system without the need for conventionalbeamsplitters. Due to this uni-axial arrangement, the main challenge is to avoid the effect of stray lightand back reflections on the measurement signal-to-noise ratio. This is achieved by implementing ahighly absorbing amplitude grating based on nanostructured silicon. We demonstrate theexperimentally realized measurement system and compare its performance to a commercial ShackHartmann Sensor.

Solution of Dispersion Relations of MultilayerOptical Fibers: A Comprehensive Study

Hisham Okda, ishac Kandas, Mostafa Hussein Aly, and M. ElOsairy

Doc ID: 321489 Received 05 Feb 2018; Accepted 09 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: The exact solution of modal dispersion relation of multilayer optical fibers is very critical and complicated especially incase of complex refractive indices of some layers added to the fiber. In this paper, a different methodology is proposedto solve the complex dispersion relations for cladding modes, based on the well-defined proper expressions ofelectromagnetic fields in the different layers of optical fibers. An optical fiber, coated by a dielectric nonlinear layer, isanalyzed using the exact four-layer model and the obtained results are compared with those analyzed in literaturebased on the approximate three-layer model, where the effect of the coating layer is neglected when solving thedispersion relation. The obtained results show a remarkable difference between the exact and the approximate valuesof effective refractive indices of the cladding modes. The inappropriate values of effective refractive indices stronglyaffect phase matching and coupling between modes which are necessary to be fulfilled in different applications such assecond harmonic generation. The proposed approach for solving general dispersion relations is also employed to getcomplex values of effective refractive indices of the cladding modes for a five-layer optical fiber with a metallic thin filminserted between the nonlinear layer and the fiber cladding. Using the appropriate expressions that describe theelectric field in the different dielectric and metallic layers of optical fibers, field distributions are displayed for somecladding modes.

Applicability of model with average inversion level tocladding-pumped multi-core erbium-doped fiberamplifier

Hirotaka Ono and Makoto Yamada

Doc ID: 324565 Received 21 Feb 2018; Accepted 09 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: This paper investigates the applicability of a model of a cladding-pumped multi-core erbium-doped fiberamplifier (CP-MC-EDFA) that employs the average inversion level of an erbium ion. The model is modifiedto include the effects of multiple cores for modifications of the background loss coefficient of thepump light. The model is validated experimentally by measurements of the pump power, gain transient,and inter-core cross-gain modulation of a cladding-pumped 12-core EDFA in which the pump light isuniformly distributed in the inner cladding. The calculated and measured pump power, gain transientresponse, and gain change caused by the inter-core cross-gain modulation agree well, suggesting the modifiedmodel is useful for characterizing a CP-MC-EDFA.

Quantitative measurement of thin phase objects:comparison of speckle deflectometry anddefocus-variant lateral shear interferometry

Mikael Sjodahl and Eynas Amer

Doc ID: 324645 Received 22 Feb 2018; Accepted 09 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: The two techniques Lateral Shear Interferometry and Speckle Deflectometry are analysed in a commonoptical system for their ability to measure phase gradient fields of a thin phase object. The optical systemis designed to introduce a shear in the frequency domain of a telecentric imaging system that gives asensitivity of both techniques in proportion to the defocus introduced. In this implementation, both techniquessuccessfully measure the horizontal component of the phase gradient field. The response of bothtechniques scales linearly with the defocus distance and the precision is comparative, with a random errorin the order of a few rad/mm. It is further concluded that the precision of the two techniques relates tothe transverse speckle size in opposite ways. While a large spatial coherence width, and correspondinglya large lateral speckle size, makes Lateral Shear Interferometry less susceptible to defocus, a large lateralspeckle size is detrimental for Speckle Correlation. The susceptibility for the magnitude of the defocusis larger for the Lateral Shear Interferometry technique as compared to the Speckle Deflectometry technique.The two techniques provides the same type of information, however, there are a few fundamentaldifferences. Lateral Shear Interferometry relies on a special hardware configuration in which the shearangle is intrinsically integrated into the system. The design of a system sensitive to both in-plane phasegradient components requires a more complex configuration and is not considered in this paper. SpeckleDeflectometry on the other hand requires no special hardware and both components of the phase gradientfield is given directly from the measured speckle deformation field.

Design of a Delayed XOR Phase Detector for OpticalPhase-locked Loop toward High-speed Coherent LaserCommunication

Yang Liu, Shoufeng Tong, Shuai Chang, Yansong Song, Yan Dong, Xin Zhao, Zhe An, and Fuwan Yu

Doc ID: 324655 Received 22 Feb 2018; Accepted 09 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: Optical phase-locked loop is an effective detection method in high-speed and long-distance laser communication.Although this method can detect weak signal light and maintain a small bit error rate, it is difficult to performbecause identifying the phase difference between the signal light and the local oscillator accurately has alwaysbeen a technical challenge. Thus, a series of studies is conducted to address this issue. First, a delayed exclusive-OR(XOR) phase detector with multi-level loop compound control is proposed. Then, a 50 ps delay line and relativesignal-to-noise ratio control at 15 dB are produced through theoretical derivation and simulation. Thereafter, aphase discrimination module is designed on a 15 × 5 􀜋􀜕􀫛 PCB board. Finally, the experiment platform is built forverification. Experimental results show that the phase discrimination range is −1.1 GHz to 1.1 GHz and the gain is0.82 mV/MHz. Three times standard deviation, that is, 0.064 V, is observed between the test and theoretical values.The accuracy of phase detection is better than 0.07 V, which meets the design standards. A coherent carrierrecovery test system is established. The delayed XOR gate has good performance in this system. When thecommunication rate is 5 Gbps, the system realizes a bit error rate of 1.55×10−8 when the optical power of thesignal is −40.4 dBm. When the communication rate is increased to 10 Gbps, the detection sensitivity drops to-39.5 dBm and still shows good performance in high-speed communications. This work provides a reference forfuture high-speed coherent homodyne detection in space. Ideas for the next phase of this study are presented at theend of this paper.

Theoretical compensation of static deformations offreeform multi mirror substrates

Johannes Hartung, Henrik von Lukowicz, and Jan Kinast

Doc ID: 320162 Received 19 Jan 2018; Accepted 09 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: Varying temperatures influence the figure errors of freeform metal mirrors by thermal expansion. Furthermore,different materials lead to thermo-elastic bending effects. The article presents a derivationof a compensation approach for general static loads. Utilizing perturbation theory this approach worksfor shape compensation of substrates which operate in various temperature environments. Verificationis made using a finite element analysis which is further used to produce manufacturable CAD models.The remaining low spatial frequency errors are deterministically correctable using diamond turning orpolishing techniques.

Band Optimization of Passive Methane Gas LeakDetection Based on Uncooled IRFPA

Zhang Xu, Weiqi Jin, Li Li, Xia Wang, Ji Chen, and Yuchao Jia

Doc ID: 319335 Received 08 Jan 2018; Accepted 07 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: Current methane gas leak detection technology uses infrared imaging in the medium wave (MW) or long wave(LW) bands, essentially applying cooled infrared detectors. In this study, a simplified three-layer radiative transfermodel is adopted based on methane gas detection theory, considering background radiation, atmospheric infraredabsorption, gas absorption, and emission characteristics to analyze the contrast of methane gas thermography indifferent infrared bands. The analysis results suggest that under certain conditions, the 6.6-8.6μm LW bandprovides higher contrast compared to the 3-5μm MW band. The optimal imaging wavelength band is selectedaccording to imaging contrast advantages and disadvantages, and infrared optical systems and infrared filters aredesigned and optimized. We build a passive methane gas leak detection system based on uncooled infrared focalplane array detectors. By collecting gas images under different conditions, the imaging detection capabilities formethane gas leaks in the MW and LW bands in a laboratory environment are compared. Finally, the developingtrends in methane gas detection technology are analyzed.

Modeling of micro- and milli-joule energy LIDARswith PMT/SiPM/APD detectors: A sensitivity analysis

Ravil Agishev

Doc ID: 325137 Received 28 Feb 2018; Accepted 07 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: The paper demonstrates a renewed concept and applications of the generalized methodology for atmospheric LIDAR capabilityprediction as a continuation of a series of our previous works, where the dimensionless parameterization appeared as a tool forcomparing systems of different scale, design, and applications. The modernized concept applied to micro- and milli-scale LIDARs withrelatively new silicon photomultiplier detectors (SiPM) and traditional photomultiplier tube (PMT) and avalanche photodiode (APD)detectors allowed prediction of the remote-sensing instruments’ performance and limitations. Such a generalized, uniform, andobjective concept is applied for evaluation of the increasingly popular class of limited-energy LIDARs using the best optical detectors,operating on different targets (backscatter or topographic, static or dynamic) and under intense sky background conditions. It can beused in the LIDAR community to compare different instruments and select the most suitable and effective ones for specificapplications.

Design of an adjustable bipod flexure for largeaperture mirror of space camera

Bei Liu, Wei Wang, Yanjun Qu, Xupeng Li, Xiao Wang, and Hui Zhao

Doc ID: 325198 Received 02 Mar 2018; Accepted 06 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: An adjustable bipod flexure technique for large aperture mirror of space camera is presented. The proposedflexure mount can decrease the surface distortions caused by the machining error and the assembly error of themirror assembly in a horizontal optical testing layout. Through the analysis of the compliance matrix ofconventional bipod flexure, the positional relationship between the rotation center and the apex of the flexure isinvestigated. Then the principle of the adjustable flexure, known as the trapezoidal switching principle, isproposed based on the analysis result. The structure and application of the flexure is also described. The opticalperformance of the mirror mounted by the adjustable flexures in different misalignments was performed usingfinite element methods. The result shows that the astigmatic aberration due to the gravity is effectively reduced byadjusting the mount and the RMS value of the mirror can be minimized with the misalignment between the flexurepivot and the neutral plane minimized. New monolithic bipod flexures based on the optimal regulating variable Δuaccording to the measurement results are manufactured to replace the ABFs to secure the mirror’s safety againstlaunch loads. Modal analysis verified the mechanical safety of mirror assembly with respect to the new monolithicflexures.

Aberration correction in holographic optical tweezersusing high-order optical vortex

Yansheng Liang, YaNan Cai, ZhaoJun Wang, Ming Lei, Zhiliang Cao, Yue Wang, Manman Li, Shaohui Yan, Piero Bianco, and Baoli Yao

Doc ID: 325450 Received 07 Mar 2018; Accepted 06 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: Holographic optical tweezers (HOT) is a powerful optical trapping and manipulating tool in numerous applications such asin life science and colloidal physics. However, the imperfections in the spatial light modulator and optical components in thesystem will introduce detrimental aberrations to the system, which will significantly degrade the trapping performance. Toaddress this issue, we develop an aberration correction technique by using high-order vortex as the correction metric. Theoptimal Zernike polynomial coefficients for quantifying the system aberrations are determined by comparing the distortedvortex and the ideal one. The efficiency of the proposed method is demonstrated by comparing the optical trap intensitydistribution, the trap stiffness, and the particle dynamics in Gaussian trap and optical vortex trap, before and after theaberration corrections.

Enhancement of Goos-Hänchen shift due to a Rydberg state

seyyed Hossein Asadpour, Hamid Reza Hamedi, and mahmoud jafari

Doc ID: 319860 Received 24 Jan 2018; Accepted 06 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: This paper hints at the Goos-Hänchen shifts properties of a cavity containing an ensemble of atoms using a four-level atomic system involving a Rydberg state. By means of the stationary phase theory and density matrix formalism in quantum optics, we study theoretically the Goos-Hänchen shifts in both reflected and transmitted light beams. It is realized that as a result of the interaction between Rydberg and excited states in such a four-level atom light coupling scheme the maximum positive and negative Goos-Hänchen shifts can be obtained in reflected and transmitted light beams owning to the effect of the Rydberg electromagnetically induced transparency (EIT) or Rydberg electromagnetically induced absorption (EIA). In particular, when the switching field is absent and the Rydberg EIT is dominant in the medium, a giant Goos-Hänchen shift can be achieved for both reflected and transmitted light beams.

Analytical-performance improvement of laserinducedbreakdown spectroscopy for theprocessing degree of wheat flour usingcontinuous wavelet transform

Ping Yang, Yining Zhu, Shisong Tang, Zhong Qi Hao, Lianbo Guo, Xiangyou LI, Yongfeng Lu, and Xiaoyan Zeng

Doc ID: 318478 Received 28 Dec 2017; Accepted 06 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: The quality and safety of food is one of the most important issues in our life. Wheat is one of the most importantcomponents of the modern agricultural product processing industry. The phenomenon of mislabeled andadulteration is getting more and more serious in the grain market. They threaten the credibility of producers andtraders and the rights of the consumers. Therefore, it is very significant to guarantee the processing degree ofwheat flour. In this work, two different spectral peak recognition methods, i.e. artificial spectral peak recognitionand automatic spectral peak recognition, are carried out to study the adulteration problem in food industry. Threegrades of the processing degree of wheat flour from Northern in China are classified by laser-induced breakdownspectroscopy (LIBS). In order to search for an automatic classification model, continuous wavelet transform (CWT)is used to the automatic recognition of LIBS spectrum peak. Principal component analysis (PCA) is used to reducethe collinearity of LIBS spectra data. First 20 PCs were selected to represent the spectra data for the followingdiscrimination analysis by support vector machine (SVM). The results showed that the classification accuracies ofautomatic spectral peak recognition is better than artificial spectral peak recognition. The classification accuraciesof artificial spectral peak recognition and automatic spectral peak recognition are 95.33% and 98.67%; the 5-foldcross-validation classification accuracies are 94.67% and 96.67%; and the operation time were 240 and 2 mins,respectively. It can be concluded that LIBS can provide simpler and faster classification without the use of anychemical reagent, which represents a decisive advantage for applications dedicated to rapidly detecting theprocessing degree of wheat flour and other cereals.

Investigations on the active compensation of the focalshift in scanning systems using a temperature signal

Falk Nagel, Andreas Patschger, Jean Pierre Bergmann, and Jens Bliedtner

Doc ID: 322785 Received 09 Feb 2018; Accepted 06 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: For the purpose of realizing a fast and cost-efficient manipulation of the laser beam in production applications, likewelding, marking and cutting, scanner systems in combination with F-Theta objectives are state-of-the-art. Due tothe absorption of the laser beam power and the resulting heat load acting on the optical system, a change of the focalplane (the so-called focal shift) occurs which significantly affects the behavior during the application process. Alinear correlation between the temperature on the optical surface of a standard F-Theta objective and the focalshift was determined whereby the coefficient of determination R² is higher than 0.99. Furthermore, two industrialwelding applications were investigated using this standard objective, and the resulting temperature distributionalong the optical surfaces was also investigated. The results show that a single measurement point appears to besufficient in order to obtain a capable input signal for a compensation method. A compensation device was implementedand a sufficient reduction of the focal shift was realized for the examined time range.

Investigation on surface/subsurface deformationmechanism and mechanical properties of GGG singlecrystal induced by nanoindentation

Chen Li, Feihu Zhang, Xin Wang, and Xiaoshuang Rao

Doc ID: 323066 Received 12 Feb 2018; Accepted 06 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: In this paper, nanoindentation tests of GGG single crystal are performed on Agilent G200 nanoindenter. The surfacemorphology and subsurface deformation mechanism induced by the nanoindentation are analyzed by a scanningelectron microscope (SEM) and a transmission electron microscope (TEM), respectively. The ductile deformationmechanism of GGG single crystal induced by the nanoindentation is a combination of “poly-crystalline nanocrystallites”and “amorphous transformation”. In addition, the relationships between the normal force and elasticrecovery, micro hardness, elastic modulus and fracture toughness of GGG single crystal are researched. Due to thesize effect caused by the tip radius of the indenter, the elastic recovery rate and fracture toughness decrease firstand then tend to be stable as the normal force increases, while the micro hardness and elastic modulus increasefirst and then decrease to be stable as the normal force increases. The stress-strain curve of GGG single crystal isdeveloped by using the nanoindentation test with a spherical indenter. When GGG single crystal deforms fromelastic regime into ductile regime, the original single crystal is changed into “poly-crystalline nano-crystallites” and“amorphous transformation” structures verified by TEM. Therefore, the material strength decreases, which resultsin a discontinuity of the stress-strain curve for GGG single crystal.

Paraxial design of optical element with variable focallength and fixed position of principal planes

Antonin Miks and Pavel Novak

Doc ID: 323074 Received 12 Feb 2018; Accepted 06 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: Our work deals with the paraxial analysis of the problem of the paraxial design of the active optical element withvariable focal length that maintains positions of its principal planes fixed during the change of its optical power.Such optical elements are important in the process of design of more complex optical systems (such as e.g. zoomsystems), where the requirement of the fixed position of principal planes during the change of optical power isessential for the design process. The proposed solution is based on the principle of the generalized membranetunable-focus fluidic lens with several membrane surfaces.

Temporally shaped Laguerre-Gaussian femtosecond laser beams

Tom Bolze and Patrick Nuernberger

Doc ID: 318645 Received 03 Jan 2018; Accepted 06 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: Femtosecond vortex beams with adjustable temporal pulse shapes are generated. These shaped laser pulses are characterized in the spectral domain by determination of the spectral amplitude and phase as well as in the spatial domain by expansion of the beam profile in a superposition of Laguerre-Gaussian transversal laser modes. The experiments demonstrate that the temporal pulse shapes impressed with a pulse shaper based on a programmable liquid-crystal spatial light modulator are basically unaltered by subsequent transmission through a spiral phase plate, while a high-quality optical vortex is imposed. The combination of programmable pulse shapes and optical vortices in femtosecond laser beams opens new possibilities for applications in micromachining, high harmonic generation, or microscopy.

Polarization-dependent wide-angle color filterincorporating meta-dielectric nanostructures

Shangliang Wu, Yan Ye, Minghui Luo, and Linsen Chen

Doc ID: 321290 Received 01 Feb 2018; Accepted 06 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: A meta-dielectric nanostructure with narrow cavities is proposed, performing as a reflective color filter for TMpolarizedlight while as a broadband reflector for TE-polarized light. By varying the cavity depth or changing theincident light polarization, reflective colors of the proposed structure cover the entire visible spectrumconveniently. In particular, the reflections of this proposed structure show good angular tolerance up to 50° forboth polarizations. Furthermore, it can display colors even with two grating slits, which shows high printingresolution up to 70555 dpi, having great potential for applications of a large area color imaging and anticounterfeitingdevices.

Compact millijoule diode-seeded two-stage fiber master oscillator power amplifiers using multi-pass and forward pumping scheme

Po-Yen Lai, Chun-Lin Chang, Sheng-Lung Huang, and Shih-Hung Chen

Doc ID: 318841 Received 03 Jan 2018; Accepted 05 Apr 2018; Posted 05 Apr 2018  View: PDF

Abstract: The multi-pass scheme of a diode-seeded fiber master oscillator power amplifier of nJ to mJ output energy level at a repetition rate <100 kHz is numerically analyzed with an experimental benchmark. For a 6/125 single-mode preamplifier with smaller input energy (< 1 nJ), the output energy is significantly improved from 0.7% to 80% and 95% of the maximum extractable energy using the double-pass and four-pass schemes, respectively. For a 30/250 large-mode area power amplifier using the double-pass and forward pumping scheme, the required input energy is decreased from 100 µJ to 18 µJ for mJ energy extraction with accompanying Stokes waves less than 10% of total energy. The system based on the full master oscillator power amplifier configuration with output energy exceeding mJ level can be optimally simplified to two stages for commercialization.

Polymer/silica hybrid integration waveguide Bragggrating based on surface plasmon polariton

Liang Tian, Fei Wang, Yuanda Wu, Xiaoqiang Sun, Yi Yunji, and Da-Ming Zhang

Doc ID: 320652 Received 25 Jan 2018; Accepted 05 Apr 2018; Posted 05 Apr 2018  View: PDF

Abstract: We proposed a device composed of Bragg grating and long-range surface plasmon polariton waveguide. Thewaveguide is formed by embedding a thin Au stripe in negative UV photoresist (SU-8 2005). The corrugated gratingstructure is created on a silica substrate using contact lithography and inductively coupled plasma etching, which istransferred onto the SU-8 2005 film by spin coating process, producing a periodic modulation of refractive indexalong the waveguide. We achieve a transmission peak with an extinction ratio of 17 dB and a 3-dB bandwidth of 0.9nm at a wavelength of 1575.2 nm, and a reflection peak with a side-mode suppression ratio of 9.7 dB, a 3-dBbandwidth of 0.9 nm at a wavelength of 1575.2 nm when the heating electrode isn’t working. The shift of thereflection peak with heating power over the range 0–6 mW is approximately 2.9 nm. This thermal dependenceexhibits an average slope of -0.48nm/mW.

Hybrid pumped gain-switched thulium fiber laser at high repetition rate

DEBASIS PAL, Aritra Paul, Sourav Das Chowdhury, Mrinmay Pal, Ranjan Sen, and ATASI PAL

Doc ID: 322844 Received 09 Feb 2018; Accepted 05 Apr 2018; Posted 05 Apr 2018  View: PDF

Abstract: A gain-switched all-fiber thulium laser at 2 µm with high repetition rate has been demonstrated under hybrid pumping scheme combined of a pulsed pump at 1.56 µm and CW pump at 793 nm. The in-band pulsed pump at 1.56 µm triggers the gain switching pulses while the CW pump at 793 nm facilitates the energy storage. Therefore, the seed cavity delivers high energy pulses allowing the elimination of multi-stage amplification. Such hybrid pump configuration is effective for generating gain-switched pulses of high average power with better slope efficiency and pulse width of few hundreds of nanosecond. The optimized cavity under such hybrid pump configuration provides output power of 5.92 W from the gain-switched oscillator with slope efficiency of 60% and pulse width of 300 ns at the repetition rate of 344 kHz. Maximum pulse energy of 17.2 µJ and peak power of 53.9 W has been achieved at this repetition rate. Stable gain-switched pulses at reduced pump pulse energy have been achieved by the use of CW pump at 793 nm. This novel pump configuration facilitates gain switching at higher repetition rates since, the energy per pump pulse decreases inherently for higher repetition rates. The gain-switched laser also operates at 520 kHz and 1.3 MHz repetition rate by changing the 1.56 µm pulsed pump and cavity parameters.

A Deep Learning Approach to Non-uniformity Correction of Uncooled Long-wave Infrared Detectors

Zewei He, Yafei Dong, Jiangxin Yang, Yanlong Cao, Christel-loic Tisse, and Yanpeng Cao

Doc ID: 320251 Received 01 Feb 2018; Accepted 05 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: Fixed-pattern noise (FPN), which is caused by the non-uniform responses of focal-plane-array (FPA) optoelectronics, imposes a challenging problem in infrared and hyper-spectral imaging systems. In this paper, we successfully demonstrate that a better performing non-uniformity correction (NUC) operator can be learned from a large amount of simulated training images instead of hand crafted as before. Our proposed training scheme, which is based on convolutional neural networks (CNNs) and a column FPN simulation module, gives rise to a powerful technique to reconstruct the noise-free infrared image from its corresponding noisy observation. Specifically, a column FPN model is utilized to comprehensively depict the non-linear characteristics of column amplifiers in the readout circuit of FPA. A large amount of high-fidelity training images are simulated and then fed into our end-to-end deep network architecture to learn the intrinsic difference between undesirable FPN and original image details. The estimated column FPN is subtracted from the raw image to obtain final NUC result. Comparative results with state-of-the-art methods, using real-captured noisy infrared images, demonstrate that our proposed deep learning based NUC method delivers better performances of FPN removal, detail preservation and artifacts suppression.

Supralinear behavior and its wavelength dependence of silicon photodiodes with over-filled illumination in visible lights

Minoru Tanabe and Kenichi Kinoshita

Doc ID: 320564 Received 05 Feb 2018; Accepted 05 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: Spectral supralinear behavior of silicon (Si) photodiodes (PDs) with over-filled illumination in the visible region was investigated. Comparing the results with the supralinearity results in under-filled illumination conditions, the supralinearities of the Si PDs with over-filled illumination sharply increased at the photocurrent over hundreds nA, and the maximum supralinearity value of approximately 5% was ob- served at the 405-nm wavelength. To validate the supralinearity increase under over-filled illumination in visible light, the linearity factor and the photocurrent relating to the Si PD position and their wave- length dependence were examined. The linearity factors increased as the laser beam approached the Si PD electrode as well as with decreasing wavelength, although the examined photocurrent decreased as the laser beam strayed off the beam detection area of the Si PD. These results show that the supralinearity with over-filled illumination in the visible region was caused by the recombination losses near the Si PD electrode. These experimental results can help obtain accurate measurements with photometry instruments constructed of Si PDs and for the three-dimensional theoretical modeling of the Si photo devices.

An improved force prediction model for grinding Zerodur based on comprehensive material removal mechanism

Guoyan Sun, Lingling Zhao, Qingliang Zhao, and Limin Gao

Doc ID: 322713 Received 12 Feb 2018; Accepted 05 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: There are few investigations in dealing with the force model on grinding brittle materials so far. However, the dynamic material removal mechanisms have not yet been sufficiently explicated through the grain-workpiece interaction statuses with considering the brittle material characteristics. This manuscript proposes an improved grinding force model for Zerodur which contains ductile removal force, brittle removal force and frictional force, corresponding to the ductile and brittle material removal phases as well as the fiction process respectively. The critical uncut chip thickness agc of brittle-ductile transition and the maximum uncut chip thickness agmax of single abrasive grain are calculated to identify the specified material removal mode, while the comparative result between agmax and agc can be applied to determine the selection of effective grinding force components. Subsequently, indentation fracture tests are carried out to acquire accurate material mechanical properties of Zerodur in establishing the brittle removal force model. Then the experiments were conducted to derive the coefficients in the grinding force prediction model. Simulated through this model, correlations between the grinding force and grinding parameters can be predicted. Finally, three groups of grinding experiments are carried out to validate the mathematical grinding force model. The experimental results indicate that the improved model is capable of predicting the realistic grinding force accurately with the relative mean errors of 6.04% to the normal grinding force and 7.22 % to the tangential grinding force respectively.

Imaging Photonic Crystals Using Hemispherical Digital Condensers and Phase-Recovery Techniques

Maged Alotaibi, Sueli Skinner Ramos, Hira Farooq, Nouf Alharbi, HAWRA ALGHASHAM, and Luis Grave de Peralta

Doc ID: 322921 Received 12 Feb 2018; Accepted 05 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: We describe experiments where Fourier ptychographic microscopy (FPM) and dual-space microscopy (DSM) are implemented for imaging photonic crystals using a hemispherical digital condenser (HDC). Phase-recovery imaging simulations show that both techniques should be able to image photonic crystals with a period below the Rayleigh resolution limit. However, after processing the experimental images using both phase-recovery algorithms, we found that DSM can, but FPM cannot image periodic structures with a period below the diffraction limit. We studied the origin of this apparent contradiction between simulations and experiments and we concluded that the occurrence of unwanted reflections in the HDC is the source of the apparent failure of FPM. We thereafter solved the problem of reflections by using a single-directional illumination source and showed that FPM can image photonic crystals with a period below the Rayleigh resolution limit.

27.5 W/m² collection efficiency solar laser using a diffuse scattering cooling liquid

Conor Smyth, Shamil Mirkhanov, Adrian Quarterman, and Keith Wilcox

Doc ID: 323328 Received 15 Feb 2018; Accepted 05 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: We report a solar pumped solid state laser using a 20 mm long, 3 mm diameter Nd:YAG laser rod. This rod was placed in a liquid cooling chamber using a water-white emulsion paint mix. This mix provides cooling for the laser crystal and also doubles as a diffuse light scattering liquid. This enhances sunlight scattering and leads to a greater absorption in the laser rod. We numerically model the solar absorption in the laser rod using a ray-tracing model and predict a 2.6-times enhancement in absorption when a 98% reflective diffuse scatter is modelled compared to 0% scattering. We experimentally demonstrated this, showing a 2.58 times increase in average output power of the solar laser compared to the use of pure water as a cooling liquid. Using the water-white paint scattering cooling liquid we demonstrated a laser with an output power of 2.3W and with a collection efficiency of 27.5 W/m².

Gamma and gamma-coupled beams

Andrey Sedukhin

Doc ID: 325232 Received 01 Mar 2018; Accepted 05 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: A new class of scalar, rotationally symmetric Gaussian-like beams is introduced. The slowly varying amplitudes of such beams are represented as analytical solutions to the paraxial wave equation, described in terms of the incomplete gamma functions and their products with quadratic exponential and power functions of different kinds. The specific functional forms of these solutions give rise to such names as gamma, gamma-Gaussian, gamma-parabolic, and gamma-anti-Gaussian beams. It is established that, within a focal volume specified by a waist size and the depth of field of about three Rayleigh lengths of the fundamental Gaussian beam of the same waist size, the parametrically optimized zero-order gamma and gamma-coupled beams possess more stabilized transverse sizes, very weak transverse irradiance sidelobes, more uniform axial irradiance distributions, and more steep controllable fall-offs of the last distributions relative to those which are inherent in the above fundamental Gaussian beam and the Bessel-Gauss beams with linear and quadratic radial dependence and the same waist size.

The Blue Fluorescence as Frequency Offset Reference in Rubidium 5S-5P-5D Transition

Piyush K. Mandal, Vaishali Naik, Vas Dev, Alok Chakrabarti, and Ayan Ray

Doc ID: 325357 Received 05 Mar 2018; Accepted 05 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: In this work we address the issue of suitability of Blue fluorescent light as frequency offset reference during ladder level excitation 5S1/2→5P3/2→5D3/2 of 85Rb atoms. A simple pump-probe spectroscopy experiment is performed to generate the non-degenerate Blue light emission due to existence of spontaneous decay route 5D3/2→6P3/2→5S1/2. By varying the relative intensity of pump-probe combination we can hover between regimes dominated by mechanisms like Double Resonance Optical Pumping and Autler Townes Splitting. The efficacy of Blue fluorescence as frequency offset reference is pronounced under DROP regime due to its narrow (~natural) linewidth. To provide further insight to the stability performance, the pump laser connecting 5P3/2→5D3/2 transition, is stabilized to the peak of Blue light with the help of probe stabilized to saturation absorption signal of 5S1/2→5P3/2 transition. For this purpose we used coherence induced modulation transfer technique. The error frequency noise power spectra and subsequent Allan Variance calculation clearly shows that probe fluctuations are transferred to pump laser due to existing two photon coherent coupling.

Analysis of short wavelength infrared radiation duringlaser welding of plasticsprocess

Jiri Martan, Jiri Tesar, Martin Kučera, Petra Honnerova, Martina Benešová, and Milan Honner

Doc ID: 319859 Received 18 Jan 2018; Accepted 03 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: In this article, a new measurement system and a new approach in calculation for infrared (IR) radiation investigation inquasi-simultaneous transmission laser welding of plastics are presented. The measurement system is based on a MW/SWIR(medium-wave/short-wave infrared) camera and optical filters narrowing the spectral region to SWIR. The measured signalscontain radiation from the melted zone in between the semitransparent and absorbing polymers, as well as radiation from thesurface and interior of the semitransparent polymer. The new calculation approach was developed to distinguish between thesesignals. It is based on simplification of the process to two places with two temperatures (surface and molten interface) andknowledge of the spectral optical properties of the material, filters and camera response. The results of measurement andcalculation for three different optical filters and polyoxymethylene (POM) samples with two thicknesses are shown and discussed.Good agreement is obtained for the calculation variant using normal transmissivity of the semitransparent polymer.

Extending axial focus of optical coherencetomography using parallel multiple aperture synthesis

EN BO, Xin Ge, Xiaojun Yu, Jianhua Mo, and Linbo Liu

Doc ID: 322665 Received 06 Feb 2018; Accepted 03 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: Compromising the inherent trade-off between transverse resolution and depth of focus (DOF) remains a longstandingissue in optical coherence tomography (OCT). In this paper, we report a novel technique—parallelmultiple aperture synthesis (pMAS) to simultaneously generate multiple optical apertures in an OCT sample armby employing a two-surface coated mirror. In the proposed pMAS, the DOF is extended by a factor of 16.49 withoutsacrificing the transverse resolution for proof-of-concept experiments when multiple distinctive apertures aredigitally synthesized. The microparticles and tissue experiments demonstrate the feasibility of pMAS to addressthe fundamental problem of limited DOF in high resolution OCT.

Passive mode locking resulted from weak polarizationdependence based on evanescent field interactionwith monolayer graphene absorber

Guiming Li, Yuan Chen, Xiaohong Yan, and Luming Zhao

Doc ID: 318682 Received 28 Dec 2017; Accepted 03 Apr 2018; Posted 04 Apr 2018  View: PDF

Abstract: Weak polarization dependence based on evanescent field interaction with monolayer graphene absorber isdemonstrated. By covering a single-layer graphene on the top of a fiber taper, the symmetry of the light fieldpropagation was destroyed. Polarization dependent loss (PDL) of 2 dB was obtained and no saturable absorptionwas observed. Passive mode locking was achieved by using the graphene-covered fiber taper in a fiber laser. It isfound that the weak PDL down to 2 dB is capable for achieving mode locking in a fiber laser. Therefore, the claim ofsaturable absorption of any graphene or 2D-materials in a fiber laser needs to be more careful.

A Polarization-insensitive, Ultra-broadband, and Compact Metamaterial-inspired Optical Absorber with Wide-Angle and Highly Efficient Performances

Mohammad Mehrabi, Hamid Rajabalipanah, Ali Abdolali, and Majid Tayarni

Doc ID: 320045 Received 22 Jan 2018; Accepted 03 Apr 2018; Posted 04 Apr 2018  View: PDF

Abstract: Because of exhibiting extraordinary features, metamaterial absorbers have captured considerable attention in recent years, especially at visible frequencies. In this paper, a new design of metamaterial-inspired perfect optical absorber (MIPVA) is investigated which exhibits ultra-broadband, polarization-independent, and wide-angle performances. The proposed MIPVA provides a flat and near unity absorbance (>99%) in an ultra-broad range of radiation wavelengths from 𝛌=500 to 625 nm, while retaining its convincing absorptivity over the entire visible wavelengths. A comprehensive parametric study is accomplished to demonstrate the effects of structural parameters on the absorptivity of the designed MIPVA. To clarify the physical mechanism of absorption, the electric field and surface current distributions of MIPVA are also monitored and elaborately discussed through the paper. The results show that the proposed MIPVA exhibits a polarization-insensitive absorption behavior in a wide range of incident wave angles. The interference theory is also utilized to verify the results. In addition, our MIPVA has a compact and low-profile design, while its ability to absorb the solar radiations is significantly improved with respect to the preceding studies in terms of both the frequency bandwidth and absorptivity; thereby, it is a worthy candidate to play an essential role in different visible-range applications.

Optical cage generated by azimuthal- and radialvariantvector beams

Zhongsheng Man, Bai Zhidong, Li Jinjian, shuoshuo zhang, Li Xiaoyu, Yuquan Zhang, Ge Xiaolu, and fu Shenggui

Doc ID: 323027 Received 12 Feb 2018; Accepted 03 Apr 2018; Posted 04 Apr 2018  View: PDF

Abstract: We propose a method to generate an optical cage using azimuthal- and radial-variant vector beams in a highnumerical aperture optical system. A new kind of vector beam that has azimuthal- and radial-variant polarizationstates is proposed and demonstrated theoretically. Then, an integrated analytical model to calculate theelectromagnetic field and Poynting vector distributions of the input azimuthal- and radial-variant vector beams isderived and built based on Richards and Wolf's vector diffraction theory. From calculations, a full polarizationcontrolledoptical cage is obtained by simply tailoring the radial index of the polarization, the uniformity U of whichis up to 0.7748 and the cleanness C is 0. Additionally, a perfect optical cage can be achieved with U = 1 and C = 0 byintroducing an amplitude modulation; its magnetic field and energy flow are also demonstrated in detail. Suchoptical cages may be helpful in applications such as optical trapping and high resolution imaging.

Design Optimization and Tolerance Analysis of aSpot-Size Converter for the Taper-Assisted VerticalIntegration Platform in InP

Valery Tolstikhin, Shayan Saeidi, and Ksenia Dolgaleva

Doc ID: 323400 Received 15 Feb 2018; Accepted 03 Apr 2018; Posted 04 Apr 2018  View: PDF

Abstract: We report on design optimization and tolerance analysis of a multi-step lateral taper spot-size converterbased on indium phosphide, performed using Monte-Carlo method. Being a natural fit to (and a keybuilding block of) the regrowth-free taper-assisted vertical integration platform, such a spot-size converterenables for an efficient and displacement-tolerant fiber coupling to InP-based photonic integratedcircuits at the wavelength 1.31 mm. An exemplary four-step lateral taper design featuring 0.35 dB couplingloss at optimal alignment of a standard single-mode fiber, 7 mm 1-dB displacement tolerance in any directionin a facet plane, and a great stability against manufacturing variances is demonstrated.

Measurement of effective optical path length ofdiffusing integrating cavities using time-resolvedspectroscopy

Xue Zhou, Jia Yu, Lin Wang, and Zhiguo Zhang

Doc ID: 323221 Received 13 Feb 2018; Accepted 02 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: A method to measure the effective optical path length (EOPL) of a diffusing cavity using time-resolved spectroscopyis presented. A 710 nm short-pulsed laser was employed as the light source with a FWHM of 0.7 ns. From thetemporal response curves, the time to establish a uniform optical field was obtained as approximately 4 ns for thiscavity. Correspondingly, light was scattered 5-6 times by the inner coating. EOPLs with different port fractions wereobtained by the selection of an appropriate initial time. Moreover, we verified a previously reported theoreticalEOPL law using time-resolved spectroscopic results. This work provides a method to measure the EOPL of adiffusing cavity at different wavelengths.

Intensity demodulated torsion sensor based on Thin-Core polarization maintaining fiber

Xue Kang, Weigang Zhang, Yanxi Zhang, Jiang Yang, LEI CHEN, Ling Xin Kong, Yun-Shan Zhang, Lin Yu, Tieyi Yan, and Pengcheng Geng

Doc ID: 320713 Received 26 Jan 2018; Accepted 02 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: An intensity demodulated torsion sensor is designed and realized, which consists of a polarization ring as the sensepart and a section of thin-core polarization maintaining fiber as the demodulation part. An intensity map of asinusoidal change can be got at some specific wavelengths, and the experimental results are corresponding to thetheoretical analysis well. The maximum sensitivity is about 0.29 dB/deg at the wavelength of 1584.6 nm, and theminimum sensitivity is about 0.10 dB/deg at the wavelength of 1510.2 nm. Meanwhile, the temperaturecharacteristic is measured in the experiment. More broadly, the proposed structure can be used in the integratedsmart device for screw looseness detection of devices in Aeronautics and Astronautics.

Supercontinuum Generation at 1.55 μm in As2S3 CorePhotonic Crystal Fiber

Harshul Balani, Ghanshyam Singh, Manish Tiwari, Vijay Janyani, and Ashish Ghunawat

Doc ID: 313081 Received 09 Nov 2017; Accepted 02 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: This paper proposes a design and mathematical study of As2S3chalcogenide PCF for broadband supercontinuumgeneration. The proposed design offers large nonlinearity coefficient and ultra flattened dispersion. The proposeddesign was analyzed using Full-vectorial finite element method. Through this method, it is investigated that anultra-broad supercontinuum spectra of 0.8–4.5 μm is attained using a As2S3 core PCF design with 20 fs pump pulsewidth and a length of 10 mm having 3 kW power at a −40 dB spectral and temporal intensity. The proposedoctagonal PCF has shown a low ZDW at the pump wavelength of 1.55 μm.

IGA-rule 17 for performance estimation ofwavelength-extended InGaAs photodetectors: validityand limitations

Yonggang Zhang, Y G, x c, Yingjie Ma, Xue Li, Shao Xiumei, Haimei Gong, and Jiaxiong Fang

Doc ID: 318161 Received 21 Dec 2017; Accepted 02 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: A rule of thumb, denoted as IGA-rule 17, has been developed to describe the temperature and cutoff wavelengthdependent dark currents of wavelength-extended InGaAs photodetectors in 2-3 μm band. The validity andlimitations of the rule are discussed. This rule is intended as an index for device developer to evaluate theirtechnologies in processing, and a simple tool for device user to estimate reachable performance at variousconditions in their design, as well as an effective bridge between the two.

Unimorph Mirror for Adaptive Optics in Space Telescopes

David Alaluf, Renaud Bastaits, Kainan Wang, Mihaita Horodinca, Grégory Martic, Bilal Mokrani, and André Preumont

Doc ID: 319196 Received 09 Jan 2018; Accepted 01 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: This paper presents a unimorph deformable mirror intended to be used as secondary corrector in space telescopes. The deformable mirror consists of a single-crystal Silicon wafer (76.2 mm diameter, 500 µm thickness) covered with an optical coating on the front side and an array of 25 independent PZT actuators acting in d31 mode on the back side. The mirror is mounted on an isostatic support with three linear PZT actuators controlling the rigid-body motion. The first part of the paper presents the experimental results obtained with the manufactured prototype. The mirror was tested in terms of RMS wavefront error, open-loop long-term stability, voltage budget for active control, rigid-body actuation, reectivity and dynamic response. The prototype is fully compliant with the requirements set by the European Space Agency (ESA). The second part of the paper, purely based on numerical simulations, presents a robust way to face thermal distortion, inherentto unimorph arhitecture.

Fabrication of an Infrared Shack–Hartmann Sensor byCombining High-Speed Single-Point Diamond Millingand Precision Compression Molding Processes

Lin Zhang, Wenchen Zhou, Neil Naples, and Allen Yi

Doc ID: 319556 Received 11 Jan 2018; Accepted 01 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: A novel fabrication method by combining high-speed single-point diamond milling and precision compressionmolding processes for fabrication of discontinuous freeform microlens arrays was proposed. Compared with slowtool servo diamond broaching, high-speed single-point diamond milling was selected for its flexibility infabrication of true 3D optical surfaces with discontinuous features. The advantage of single-point diamond millingwas that the surface features can be constructed sequentially by spacing virtual spindle axes at arbitrary positionsbased on the combination of rotational and translational motions of both the high speed spindle and linear slides.By employing this method, each micro lenslet was regarded as a microstructure cell by moving the virtual spindleaxis pass through the vertex of each cell. An optimization arithmetic based on minimum-area fabrication wasintroduced to the machining process to further increase machining efficiency. After the mold insert was machined,it was employed to replicate the microlens array onto chalcogenide glass. In the ensuing optical measurement, theself-built Shack-Hartmann wavefront sensor was proven to be accurate in infrared wavefront detection by bothexperiments and numerical simulation. The combined results showed that precision compression molding ofchalcogenide glasses could be an economic and precision optical fabrication technology for high-volumeproduction of infrared optics.

Sr/Ca ratio analysis of seashell using laser-induced breakdown spectroscopy under objective-lens focusing and single-lens focusing

Yuandong Li, Yuan Lu, Yunjiao lan, Ying Li, Jinjia Guo, and Ronger Zheng

Doc ID: 322937 Received 12 Feb 2018; Accepted 01 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: Laser-induced breakdown spectroscopy (LIBS) is a new technique for seashell elemental analysis, and now that application is in rapid developing. In this work, LIBS was applied for the scallop shell (Chlamys (Azumapecten) Farreri) analysis using the element ratio Sr/Ca, and the analytical result was compared under objective lens (OL) focusing and single lens (SL) focusing respectively. It is interesting to find that, under the 2 focusing arrangements, the ratio (Sr/Ca) variation on the shell cross section was performing totally different, while in technical aspect the 2 focusing arrangements presented almost the same characteristic. The difference of shell sampling amount and size might be the reason for inconsistent analysis performance under the 2 focusing arrangements. The SEM-EDS scanning results of shell proved that LIBS analysis under OL focusing was closer to the actual Sr/Ca distribution than that under SL focusing. The obtained results might be useful for the methodology of LIBS in seashell applications.

Rapid measurement and compensation method ofeccentricity in automatic profile measurement of ICFcapsule

Shaobai Li, Yun Wang, Wang Qi, MA XIANXIAN, WANG LONGXIAO, Weiqian Zhao, and Xusheng Zhang

Doc ID: 309919 Received 24 Oct 2017; Accepted 01 Apr 2018; Posted 09 Apr 2018  View: PDF

Abstract: In this paper, we propose a new measurement and compensation method for the eccentricity of the inertialconfinement fusion (ICF) capsule, which combines computer vision and laser differential confocal method to alignthe capsule in rotation measurement. This technique measures the eccentricity of the capsule by obtaining the subpixelprofile with a moment-based algorithm then performs the preliminary alignment by the two-dimensional(2D) adjustment. Next, we use the laser differential confocal sensor (LDCS) to measure the height data of theequatorial surface of the capsule by turning it around then obtain and compensate the remaining eccentricityultimately. This method is a non-contact, automatic, rapid, high-precision measurement and compensationtechnique of eccentricity for the capsule. Theoretical analyses and preliminary experiments indicate that themaximum measurement range of eccentricity of this proposed method is 1.8 mm for the capsule with a diameter of1 mm, and it could eliminate the eccentricity to less than 0.5 μm in 30s.

Fringe projection system for high-temperature workpieces – design, calibration and measurement

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

Doc ID: 322967 Received 12 Feb 2018; Accepted 31 Mar 2018; Posted 03 Apr 2018  View: PDF

Abstract: In the Collaborative Research Centre 1153 Tailored Forming the geometry of hot measurement objects needs to be captured fast, area-wise and with high precision. The documentation of the hybrid components’ shrinkage behaviour directly after the forming process can yield insight into the development ofresidual stresses.In this paper, we present a fringe projection measurement set-up designed for the topography measurement of high-temperature steel shafts, comprising two cameras with different lenses and a projector. In order to separate the measurement signal from light by self-radiation, a green bandpass filter is installed in front of the measurement camera’s sensor. The optical sensors are protected from the measurementobject’s temperature and possible scale by a glass panel and a working distance of at least 250 mm. High resolution measurements are guaranteed due to a telecentric measurement camera and a triangulationangle of more than 30°. The triangulation angle requires an additional entocentric calibration camera to provide a highly accurate projector model estimation. Special attention is therefore devoted to the developed calibration routine, the glass panel effect and the applied distortion models. The quality of the calibration routine is validated by a reference sphere measurement. Furthermore, the geometry data of a red-glowing heating rod (approximately 1020 °C) is acquired to demonstrate the performance of the presented system.In future applications, the presented set-up will be used with a force controlled-clamping unit to enable secure and position stable topography acquisition of hot measurement objects.

3D-Printed Polymer Antiresonant Waveguides for ShortReach Terahertz Applications

Lieke van Putten, Jon Gorecki, Eric Rodrigue Numkam Fokoua, Vasilis Apostolopoulos, and Francesco Poletti

Doc ID: 320397 Received 23 Jan 2018; Accepted 31 Mar 2018; Posted 03 Apr 2018  View: PDF

Abstract: In this work, we present a 3D printed waveguide that provides effective electromagnetic guidance in theTHz regime. The waveguide is printed using low-cost polycarbonate and a conventional fused depositionmodelling printer. Light guidance in the hollow-core is achieved through antiresonance and it improvesthe energy effectively transported to the receiver compared to free space propagation. Our demonstrationadds to the field of 3D printed terahertz components, providing a low-cost way of guiding terahertzradiation.

An approach for correcting particle size distributionmeasured by optical particle counter in high-pressuregas pipes

Lifeng Lu, Xiaolin Wu, Zhongli Ji, Zhiyi Xiong, Mingxing wang, and Xuan Song

Doc ID: 321471 Received 05 Feb 2018; Accepted 30 Mar 2018; Posted 03 Apr 2018  View: PDF

Abstract: A set of on-line particle detection devices was developed for the quick and accurate assessment of particle sizeand concentration in high-pressure natural gas, which can be applied at any pressure below 10 MPa. In actualsite tests with P=3.42 and 2.36 MPa, the on-line tested results of particle size and concentration are generallysmaller as compared to those of the off-line gathered under atmospheric conditions. That’s mainly due to thedetection performance degradation of optical particle counter (OPC) caused by gas pressure change leading tothe refractive index change of the sounding medium with which the optical paths of the incident light andscattering light are changed. Aiming at solving the unfavorable problem, an analysis of the dynamic change ofoptical measurement volume of the optical detection system with gas pressure was conducted based on the gasstate parameters and geometric optics theory, and a dynamic model of both was established, which can beaccompanied by a particle size modification method based on light scattering theory. After a correction of testedresults, the deviations in median diameter and concentration between the modified on-line and off-line testresults were within an acceptable range. Therefore, the proposed modification is a feasible and reliableapproach to enhance on-line sparticle detection.

New Method for Measuring the AC Half WaveVoltage of Mach-Zehnder Modulator Based onOpto-electronic Oscillation

jun hong, Chen Chu, Zhiqiang Peng, ling li, Liu Haibo, and jian guo

Doc ID: 324785 Received 23 Feb 2018; Accepted 30 Mar 2018; Posted 03 Apr 2018  View: PDF

Abstract: A new method for measuring the alternating current(AC) half wave voltage of Mach-Zehnder Modulator(MZM) is proposedand verified by experiment in this paper. Based on the opto-electronic self-oscillation technology, the physical relationshipbetween the saturation output power of the oscillating signal and the AC half wave voltage is revealed, and the value of theAC half wave voltage is solved by measuring the saturation output power of the oscillating signal. The experimental resultsshow that the measured data of this new method involved are in agreement with a traditional method, and not only anexternal microwave signal source but also the calibration for different frequency measurement is not needed in our newmethod. The measuring process is simplified with this new method on the premise of ensuring the accuracy of measurement,and it owns good practical value.

Deformation Reconstruction by means of Surface Optimization. Part II: Time-resolved Electronic Speckle Pattern Interferometry

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

Doc ID: 322623 Received 13 Feb 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: Analysis of time-resolved electronic speckle pattern interferograms using an optimization algorithm is shown to provide full-field measurements of transient surface deformation with high spatial and temporal resolution. The arrangement uses a CW laser and high-speed camera to capture speckle images, with the recovery of the time-resolved deformation achieved by spatiotemporal processing using an optimization algorithm. It is shown that the process allows imaging of high-speed non-monotonic out-of-plane displacements with sub-micrometer amplitude. Time-resolved amplitude and phase recovery is demonstrated by analyzing the out-of-plane deformation of harmonic and transient events in a friction membranophone.

Residual vibration control based on a global searchmethod in a high-speed white light scanninginterferometer

Zhenyuan Song, Tong Guo, Xing Fu, and Xiaotang Hu

Doc ID: 315413 Received 11 Dec 2017; Accepted 28 Mar 2018; Posted 29 Mar 2018  View: PDF

Abstract: To achieve high-speed measurements using white light scanning interferometers, the scanning devicesused need to have high feedback gain in close-loop operations. However, flexure hinges induce a residual vibrationthat can cause a misidentification of the fringe order. The reduction of this residual vibration is crucial because thehighly nonlinear distortions in interferograms lead to clearly incorrect measured profiles. Input shaping can beused to control the amplitude of the residual vibration. The conventional method uses Continuous WaveletTransform (CWT) to estimate parameters of the scanning device. Our proposed method extracts equivalent modalparameters using a global search algorithm. Due to its simplicity, ease of implementation, and response speed, thisglobal search method outperforms CWT. The delay time is shortened by searching because fewer modes areneeded for the shaper. The effectiveness of the method has been confirmed by the agreement between simulatedshaped responses and experimental displacement information from the capacitive sensor inside the scanningdevice, and the intensity profiles of the interferometer have been greatly improved. An experiment measuring thesurface of a silicon wafer is also presented. The method is shown to be effective at improving the intensity profilesand recovering accurate surface topography. Finally, frequency localizations are found to be almost stable withdifferent proportional gains, but their energy distributions change.

Multistate passively mode–locked thulium-dopedfiber laser with nonlinear amplifying loop mirror

Xiao-Fa Wang, Xiaoling Peng, and Junhong Zhang

Doc ID: 320898 Received 29 Jan 2018; Accepted 28 Mar 2018; Posted 29 Mar 2018  View: PDF

Abstract: In this paper, a multistate passively mode-locked thulium-doped fiber laser with nonlinear amplifying loop mirroris reported. An ultra-high numerical aperture fiber is employed to compensate the cavity abnormal dispersion, andthe net cavity dispersion value is fixed at -0.046 ps2. By changing the pump power, three different mode-lockedregions, namely Q-switched mode-locking operation, mode-locking operation and dual-wavelength mode-lockingoperation, are observed sequentially. When the pump power is raised to the threshold of 1.60 W, the transitionstate of the Q-switched mode-locking begins to be observed. With the pump power increases from 2.88 W to 8.75W, stable single-wavelength mode-locking operation is obtained. And the center wavelength is 1988.73 nmcorresponding to 3-dB spectral bandwidth of 11.21 nm. As the pump power is raised beyond to 8.75 W, dualwavelengthmode-locking operation is developed, where the dual-wavelength are 1969.70 nm and 1984.12 nmwith 3-dB spectral bandwidth of ∼4.11 nm and ∼6.14 nm, respectively.

Measurement of two-dimensional thickness of micro-patterned thin film based on image restoration in spectroscopic imaging reflectometer

Mingab Kim and Jinyong kim

Doc ID: 321150 Received 31 Jan 2018; Accepted 28 Mar 2018; Posted 29 Mar 2018  View: PDF

Abstract: This article introduces a method to overcome the limitation of thickness measurement of micro-patterned thin film. A spectroscopic imaging reflectometer system which consists of an acousto-optic tunable filter, a CCD camera and a high magnitude objective lens was proposed and the stack of multispectral images was generated. To secure improved accuracy and lateral resolution in reconstruction of two-dimensional thin film thickness, prior to the analysis on spectral reflectance profiles from each pixel of multispectral images, image restoration based on iterative deconvolution algorithm was applied to compensate image degradation coming from blurring.

The application of double metal/dielectric gratings inoptical displacement detection

Mengwei Li, hao geng, Qiannan Wu, rui zhang, Yueping Han, and gao wang

Doc ID: 322655 Received 09 Feb 2018; Accepted 28 Mar 2018; Posted 29 Mar 2018  View: PDF

Abstract: A high-resolution displacement detection based on in-plane and out-of-plane moving grating is discussed inthis paper. To improve the detective resolution and stability, a model of double metal/dielectric optical gratingis established to investigate the tolerance of grating parameters. The zero-order optical diffraction efficientof the grating are calculated by rigorous coupled wavelength analysis (RCWA), which depend on thegrating parameters. The dependency relation curve is a cosine and pulse curve respectively, for in-planemovement with the highest slope superior to 0.29%/nm and the highest resolution can reach to 0.01 nm, forout-of-plane movement with the highest slope superior to 1.63%/nm and the optimum resolution can reachto 0.002 nm. These results indicate that the in-plane effect is feasible to a long range and high-resolution displacementdetection, and the out-of-plane effect is suitable to small-range and high-resolution displacementdetection. Both the two kinds of the effect provide us a designed solution for the development of a highresolutiondisplacement sensor.

Adjustable microscopic measurement of nanogapwaveguide and plasmonic structures

Mengqi Shen, Supannee Learkthanakhachon, Suejit Pechprasarn, Yaping Zhang, and Michael Somekh

Doc ID: 309820 Received 23 Oct 2017; Accepted 27 Mar 2018; Posted 28 Mar 2018  View: PDF

Abstract: We investigate the performance of surface plasmon and Fabry-Perot modes formed between two closely spacedlayers. The motivation for this study is twofold, firstly, to look for modes that may be excited at lower incidentangles compared to the usual Kretschmann configuration with similar or superior refractive index responsivityand, secondly, to develop a simple and applicable method to study these structures over a wide range ofseparations without recourse to the construction of ad hoc structures.Using back focal plane observation and appropriate signal processing, we show results for the Otto configuration atvisible wavelengths at a range of separations not reported hitherto. Moreover, we investigate a hybrid structure wecall the Kretschmann-Otto configuration that give modes that change continuously from a hybridized surfaceplasmon mode to a zero order Fabry Perot mode. The ability to change the separation to small gap distancesenables us to examine the Fabry-Perot modes where we show that it is has superior refractive index responsivity,by more than an order of magnitude, compared to the Kretschmann configuration.

Design and assessment of a 360° panoramic and highperformancecapture system with two tiledcatadioptric imaging channels

Weitao Song, Xuming Liu, Peng Lu, Yetao Huang, DONGDONG WENG, Yuanjin Zheng, yue liu, and Yongtian Wang

Doc ID: 318243 Received 21 Dec 2017; Accepted 25 Mar 2018; Posted 29 Mar 2018  View: PDF

Abstract: It has always been a challenge to obtain a 360° panoramic imaging system with a high resolution and non-visibleseam. In this study, a 360° panoramic and high-performance system has been developed based on two tiledimaging channels with a field of view (FOV) of 190° and F/# of 2.0. In this study, some issues on 360° panoramictiled methods, such as relative illuminance, and ghost images, were analyzed in detail and taken into considerationduring the design procedure. In the final design, the stop has been fulfilled for each field angle, and the ghostimages have also been well optimized. A proof-of-concept prototype producing a high performance 360° panoramicvideo has been developed.

Enhance field water-color measurements with a Secchi disk and its implication for fusionof active and passive ocean color remote sensing

Zhongping Lee, Shaoling Shang, Keping Du, Bing-Yi Liu, Gong Lin, Jianwei Wei, and Xiaolong Li

Doc ID: 323275 Received 16 Feb 2018; Accepted 25 Mar 2018; Posted 29 Mar 2018  View: PDF

Abstract: Inversion of the total absorption (a) and backscattering (bb) coefficients of bulk waterthrough a fusion of remote-sensing reflectance (Rrs) and Secchi disk depth (ZSD) is developed. Anapplication of such a system to a synthesized wide-range dataset shows a reduction of ~3 folds inthe uncertainties of inverted a(λ) (in a range of ~0.01 – 6.8 m-1) from Rrs(λ) for the 350-560 nmrange. Such a fusion is further proposed to process concurrent active (ocean LiDAR) and passive(ocean color) measurements, which can lead to nearly “exact” analytical inversion of an Rrsspectrum. With such a fusion, it is found that the uncertainty in the inverted total absorption inthe 350-560 nm range could be reduced to ~2% for the synthesized data, which can thussignificantly improve the derivation of absorption coefficients of other varying components.Although the inclusion of ZSD places an extra constraint in the inversion of Rrs, no apparentimprovement over the quasi-analytical algorithm (QAA) was found when the fusion of ZSD andRrs was applied to a field dataset, which calls for more accurate determination of the absorptioncoefficients from water samples.

Optical characterization of Chinese hybrid rice using laser-induced fluorescence techniques-Laboratory and remote-sensing measurements

zheng Duan, Ting Peng, Shiming Zhu, Ming Lian, Yiyun Li, Wei fu, Jiabao Xiong, Quanzhi Zhao, Sune Svanberg, Jiandong Hu, and Guangyu Zhao

Doc ID: 314197 Received 24 Nov 2017; Accepted 25 Mar 2018; Posted 26 Mar 2018  View: PDF

Abstract: Chinese hybrid rice of different varieties, growing in paddies in the Pingqiao district, north of Xinyang city, Henan Province, China, was studied in detailed spectroscopic characteristics using laser-induced fluorescence. The base for the studies was the new South China Normal University mobile lidar laboratory, which was dispatched on site, providing facilities both for laboratory studies using a 405 nm excitation source, as well as remote-sensing measurements at ranges from around 40 m to 120 m, mostly employing the 532 nm output from a Nd:YAG laser. We, in particular, studied the spectral influence of the species varieties as well as the level of nitrogen fertilization supplied. Specially developed contrast functions as well as multivariate techniques were applied, and useful characterization of the rice could be achieved.

Experimental study on measuring pulse duration inthe far field for high energy petawatt lasers

Jianwei Yu, Xiaoping Ouyang, Li zhou, Youen Jiang, Bao-Qiang Zhu, and Jianqiang Zhu

Doc ID: 315474 Received 11 Dec 2017; Accepted 25 Mar 2018; Posted 26 Mar 2018  View: PDF

Abstract: We study the feasibility of measuring pulse duration in the far field in high energy petawatt lasers with single shotautocorrelation. This single shot autocorrelation technique makes use of parametric upconversion in media withrandomly oriented ferroelectric domains, which supports transverse second-harmonic generation with twocounterpropagating fundamental beams. We show this technique possesses a large time window, capable ofmeasuring pulse with the temporal duration ranging from sub-picosecond to tens of picosecond. We test theperformance of this technique in the presence of multipulse structures, intensity modulations in the near field andspatial-temporal coupling in fundamental beams. We also investigate the influences of beam pointing discrepancyon the measurement. Our study can be served as a preliminary experiment for robustly characterizing the pulseduration in high energy petawatt lasers.

Analysis and Correction about Measurement Error ofEdge Sensor Caused by Deformation of Guide FlexureApplied in the SSA of TMT

haifeng cao, zhang jingxu, Fei Yang, qichang an, Hongchao Zhao, and Peng Guo

Doc ID: 314390 Received 08 Dec 2017; Accepted 23 Mar 2018; Posted 26 Mar 2018  View: PDF

Abstract: The Thirty Meter Telescope (TMT) project will design and build a thirty-meter diameter telescope for research inastronomy in visible and infrared wavelengths. The primary mirror of TMT is made up of 492 hexagonal mirrorsegments under active control. The highly segmented primary mirror will utilize edge sensors to align and stabilizethe relative piston, tip, and tilt degrees of segments. The Support System Assembly (SSA) of segmented mirrorutilizes a Guide Flexure to decouple the axial support and lateral support while its deformation will bring inmeasurement error of edge sensor. We have analyzed the theoretical relationship between the segment movementand the measurement value of edge sensor. Besides, we have proposed an error correction method with matrix.The correction process and the simulation results of the edge sensor will be described in this paper.

Wafer defect detection by polarization insensitiveexternal differential interference contrast module

Amit Nativ, Haim Feldman, and Natan Shaked

Doc ID: 319722 Received 18 Jan 2018; Accepted 21 Mar 2018; Posted 21 Mar 2018  View: PDF

Abstract: We present a system, which is based on a new external, polarization-insensitive differential interferencecontrast (DIC) module, specifically adapted for detecting defects in semiconductor wafers. We obtained defectsignal enhancement relative to the surrounding wafer pattern when compared to bright-field imaging. The new DICmodule proposed is based on a shearing interferometer, which connects externally at the output port of an opticalmicroscope, and enables imaging thin samples, such as wafer defects. This module does not require polarizationoptics (such as Wollaston or Nomarski prisms), and is insensitive to polarization, unlike traditional DIC techniques.In addition, it provides full control of the DIC shear and orientation, which allows obtaining a differential phaseimage directly on the camera (with no further digital processing), while enhancing defect detection capabilities,even if the size of the defect is smaller than the resolution limit. Our technique has the potential of futureintegration into semiconductor production lines.

Optimization of optical properties of photonic crystal fibers infiltrated with carbon tetrachloride for supercontinuum generation with sub-nJ femtosecond pulses

QUANG HO DINH, Jacek Pniewski, Hieu le van, Aliaksandr Ramaniuk, Van Cao, Krzysztof Borzycki, Khoa Dinh, Mariusz Klimczak, and Ryszard Buczynski

Doc ID: 318735 Received 03 Jan 2018; Accepted 21 Mar 2018; Posted 29 Mar 2018  View: PDF

Abstract: A photonic crystal fiber made of fused silica glass, infiltrated with carbon tetrachloride (CCl4), is proposed as a new source of supercontinuum. Guiding properties in terms of effective refractive index, attenuation and dispersion of the fundamental mode are studied numerically. As a result two optimized structures are selected and verified against supercontinuum generation in details. We proved the possibility of coherent flat supercontinuum generation in the range of 0.82–1.74 μm with a selected fiber structure using as a pump 300 fs pulses with a central wavelength of 1.55 μm and low peak pulse power of 2.5 kW. The proposed solution may lead to new low-cost all-fiber optical systems.

Silicon Microsphere Whispering Gallery Modes excitedby Femtosecond Laser Inscribed Glass Waveguides

Huseyin Cirkinoglu, Mustafa Bayer, Ulas Gokay, Ali Serpenguzel, Belen Sotillo, Vibhav Bharadwaj, Roberta Ramponi, and Shane Eaton

Doc ID: 319727 Received 17 Jan 2018; Accepted 15 Mar 2018; Posted 16 Mar 2018  View: PDF

Abstract: We report on coupling to the 500 μm radius silicon microsphere whispering gallery modes by a femtosecond laserinscribed glass optical waveguide. The shallow glass waveguide with a large mode field diameter in the nearinfraredis written at a depth of 25 μm below the glass surface, resulting in a high excitation impact parameter of525 μm for the microsphere. The excited whispering gallery modes of the silicon microsphere have quality factorsof approximately 105 in the 90° elastic scattering and the 0° transmission. The integration of such spherical siliconmicroresonators on femtosecond-laser inscribed glass waveguides is promising for photonic communication,computation, and sensing applications.

Characterization of the focusing performance of axialline-focused spiral zone plates

Chenglong Zheng, Shi-Lei Su, Huaping Zang, Ziwen Ji, yongzhi tian, Shu Chen, kaijun Mu, lai Wei, Quanping Fan, Chuanke Wang, Xiaoli Zhu, Changqing Xie, leifeng cao, and Erjun Liang

Doc ID: 314801 Received 01 Dec 2017; Accepted 12 Mar 2018; Posted 12 Apr 2018  View: PDF

Abstract: Axial line-focused spiral zone plates were developed for operation at optical wavelengths. The design, fabrication,and diffraction properties of the proposed element are presented. Numerical results showed that hollow beamscould be generated, and that the element can be employed for a multi-wavelength operation. The hollow beamwithin the focal depth was demonstrated experimentally, using a charge-coupled device camera and sliding guide.The results were consistent with those obtained by the simulations. The proposed optical device exhibitssignificant potentials for various applications including optical manipulation and lithography.

High-speed CGH based on Resource Optimization for Block-based Parallel Processing

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

Doc ID: 318415 Received 27 Dec 2017; Accepted 26 Feb 2018; Posted 26 Feb 2018  View: PDF

Abstract: A huge amount of computation is required to generate a hologram using a computer. In order to speed up the computer generated-hologram (CGH) operation, we use parallel programming technique using GPGPU (Global Purpose Graphic Processing Unit). In this paper, we propose three techniques to improve CGH performance in the condition using GPU. The first is to remove the memory bottleneck by allocating shared memory and a dedicated thread for this process, and the second is to optimize the block allocation within the GPU using a hologram pixel-based method. The third is to increase the computation time by minimizing the idle region by using multiple threads of host processor and device. When these three techniques were implemented in the GTX 1080Ti GPU, it took 25.05ms to generate the HD digital hologram with 10K object points, and compared to the previous researches, the performance improvement was at least 1.56 times up to 216.71 times.

A ultra-high sensitivity refractive index sensor of D-shape PCF based on Surface Plasmon Resonance

junjun Wu, shuguang Li, xinyu wang, Min Shi, Xinxing Feng, and Yundong Liu

Doc ID: 314037 Received 21 Nov 2017; Accepted 23 Feb 2018; Posted 13 Apr 2018  View: PDF

Abstract: We propose a D-shape photonic crystal fiber (PCF) refractive index sensor with ultra-high sensitivity and wide detection rang. The gold layer is deposited on the polished surface, avoiding the filling or coating inside the air-holes of PCF. The influences of the gold layer thickness and the diameter of the larger air-holes are investigated. The sensing characteristics of the proposed sensor are analyzed by the finite element method. The maximum sensitivity can reach 31000nm/RIU, and the refractive index detection range is from 1.32 to 1.40. Our proposed PCF has excellent sensing characteristics and is competitive in sensing devices.

The giant Goos–Hӓnchen shift in two different enantiomers chiral molecules via quantum coherence

Rajab Nasehi and Mohammad Mahmoudi

Doc ID: 302077 Received 18 Jul 2017; Accepted 25 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: The GH shifts in the reflected and transmitted probe light through a cavity mixture of left-handed and right-handedchiral molecules into two enantiomer states are investigated. Due to broken mirror symmetric of the left- andright- handed chiral molecules in presence of cyclic population transfer, such the quantum systems can beselectively excited because of the coexistence of one- and two-photon transitions. With the help of coupling Rabifrequencyand damping effects due to scattering processes, the generated GH shifts accompany by simultaneouslynegative and positive lateral shift in reflected and transmitted probe lights are realized to be greatly enhanced. It isfound that the large negative and positive GH shifts are available in the presence of multi-photon resonance andoff-resonance conditions for two different enantiomers chiral molecules. Moreover, the switching betweensuperluminal and subluminal light propagation are extremely dependence to choose the left- and right-handedchiral molecules. Furthermore, the effects of pulse shape and mode of Laguerre-Gaussian probe light on the GHshifts leads to switch between negative and positive shift are also studied. The negative and positive GH shifts inreflected and transmitted probe beam for an incident Gaussian and different mode of Laguerre-Gaussian shapedbeam are also discussed with various widths by use of two different enantiomer chiral molecules.

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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