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Accepted papers to appear in an upcoming issue

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A Noise Adaptive Fading Kalman Filter for Free-SpaceLaser Communication Beacon Tracking

Lixing Li, Fasheng Yang, Yongmei Huang, and Qiang Wang

Doc ID: 268332 Received 15 Jun 2016; Accepted 22 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: We proposed a prediction algorithm for laser communication pointing, acquisition, and tracking (PAT) subsystems in order to further improve PAT accuracy and reduce the effect of processing delay. In terms of this prediction algorithm, a fading Kalman filter is employed, with the observation noise obtained by grey value distribution of the laser images. Moreover, to better fit the dynamics of a laser target, the two-stage dynamic model has been chosen as the state transition model for Kalman filtering. Besides, the two-stage dynamic model has been modified by accommodating its form to a change of time lag, thereby compensating the effect of time delay. A series of horizontal path (17km) experiments under different atmospheric conditions were conducted in the fields. According to the experimental results, the algorithm we proposed could effectively reduce the tracking error and improve pointing accuracy.

On the influence of ethanol admixture on the determination of equivalence ratios in DISI engines by laser-induced fluorescence

Michael Storch, Susanne Lind, Stefan Will, and Lars Zigan

Doc ID: 268998 Received 12 Jul 2016; Accepted 22 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: In this work, planar laser-induced fluorescence (PLIF) of a fuel tracer is applied for the analysis of mixture formation for various ethanol/iso-octane blends in a direct-injection spark-ignition (DISI) engine. The tracer triethylamine (TEA) was added to pure iso octane and ethanol as well as to their blends E20 and E85 for the measurement of the fuel/air-ratio. In general, ethanol blending strongly affects the mixture formation process, which is caused by specific physical fuel properties influencing the evaporation process of ethanol in comparison to iso-octane. As interactions of the fuel on tracer fluorescence appear possible, TEA fluorescence was studied for different fuel blends in a cuvette, a calibration cell under constant conditions and in an optically accessible IC engine at late injection timing. It was found that ethanol blending strongly affects the fluorescence intensity of TEA in the liquid phase, which can be explained by interaction of the tracer and ethanol molecules. However, in the gas phase a quantification of the fuel/air ratio is possible for different ethanol fuel blends, which is demonstrated in a DISI-engine. Under stratified charge conditions the engine results showed significant impact of high amount of ethanol on the mixture formation process, leading to a leaner mixture in comparison to iso-octane.

Shift-bonded Resonance Domain Diffraction Gratings

Ramon Axelrod, Michael Golub, and Yosi Shacham

Doc ID: 269570 Received 05 Jul 2016; Accepted 22 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: The resonance domain transmission diffractive optics with grating periods comparable to that of the illumination wavelength offers large angles of light deflection and nearly 100% Bragg diffraction efficiency. Optical design preferences for nearly normal incidence can be met by proper choice for the slant of the diffraction grooves relative to the substrate. However, straightforward fabrication of the slanted submicron high-aspect-ratio grooves is challenging. In this paper, optical performance comparable to that of the slanted grooves was achieved by an alternative solution of bonding two half-height symmetrical gratings with a lateral shift and an optional small longitudinal spacing. Results of design, nano-fabrication and optical testing are presented.

Immersed diffraction grating refractometers of liquids

Eduardo Barbosa and Luiz Felipe Gonçalves Dib

Doc ID: 270132 Received 08 Jul 2016; Accepted 22 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: In this work we report the development, construction and the performance of two liquid refractometers which use a reflective diffraction grating immersed in the test liquid. The liquid is contained in a transparent glass cell with a rectangular cross section. The grating is oriented in such a way that the propagation directions of the incident beam and the beam diffracted by the lower part of the grating immersed in the liquid are perpendicular. In this configuration, the refractive index is determined by measuring the angle of the zeroth-order diffraction beam coming from the upper part of the grating which is in contact with air. The diffractive refractometers (DR-1 and DR-2) have different angle measurement procedures and different light detection systems, and their advantages and drawbacks are pointed out. In the experiments precisions of the order of 10-5 and 10-4 for DR-1 and DR-2 are achieved. The performances of both systems are compared with the performance of a commercial Abbe refractometer in the measurement of sugar and NaCl aqueous solutions.

Polarization-based material classification technique using passive millimeter-wave polarimetric imagery

Fei Hu, Yayun Cheng, Liangqi Gui, Liang Wu, Xinyi Zhang, Xiaohui Peng, and Jinlong Su

Doc ID: 272459 Received 27 Jul 2016; Accepted 22 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: The polarization properties of thermal millimeter-wave emission capture inherent information ofobjects, e.g., material composition, shape, surface features. In this paper, a polarization-based materialclassificationtechnique using passive millimeter-wave polarimetric imagery is presented. Linearpolarization ratio (LPR) is created to be a new feature discriminator, which is sensitive to material typeand irrelevant to ambient radiation. The LPR characteristics of several commonly natural and artificialmaterials are investigated by theoretical and experimental analysis. Based on the priori informationabout LPR characteristics, the optimal range of incident angle and the classification criterion are discussed.Simulation and measurement results indicate that the presented classification technique is effective fordistinguishing between metals and dielectrics. This technique suggests possible applications for outdoormetal target detection in open scenes.

Modulation of large absolute PBG in 2D plasma photonic crystal containing anisotropic material

Qian Li, Kang Xie, Dongsheng Yuan, Wei Zhang, Lei Hu, Qiuping Mao, Hai Ming Jiang, Hu Zhijia, and Erlei Wang

Doc ID: 272893 Received 01 Aug 2016; Accepted 22 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: The large absolute photonic band gaps of 2D anisotropic magnetic plasma photonic crystals with hexagonal latticeand square lattice are firstly obtained by introducing tellurium dielectric rods using modified plane waveexpansion method. Equations for calculating the band structures in the irreducible part of the first Brillouin zoneare theoretically deduced. The modulation properties indicate that the location and band width of the absolute PBGcould be tuned by filling factor, plasma frequency and magnetic field, respectively. The effective tunable ranges andthe critical values of these parameters are given out. These results could be helpful in designing 2D anisotropicPPCs with large absolute PBGs.

Wavefront sensing by numerical evaluation ofdiffracted wavefields

Mohamed Bichra, Nail Sabitov, Thomas Meinecke, and Stefan Sinzinger

Doc ID: 273180 Received 04 Aug 2016; Accepted 22 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: A novel wavefront sensor principle based on diffraction theory and Fourier analysis with a modifiedangular spectrum propagator has been developed. We observe the propagation of a wavefront behind atwo-dimensional cross grating and derive a universal method to extract the phase gradient directly froma captured intensity image. To this end the intensity distribution is analyzed in the spectral domain andthe processing is simplified by an appropriate decomposition of the propagator kernel. This methodworks for arbitrary distances behind the grating. Our new formulation is verified through simulations.The wavefront generated by a freeform surface is measured by the new method and compared withmeasurements from a commercial Shack- Hartmann wavefront sensor.

Additive phase noise of fiber-optic links used in photonic microwave-generation systems

James Cahill, Weimin Zhou, and Curtis Menyuk

Doc ID: 272637 Received 27 Jul 2016; Accepted 21 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: In this work, we analyze the contributions of several mechanisms to the additive phase noise of theoptical fiber in a microwave-photonic link. We discuss their fiber-length dependence and their impact onthe phase noise of an opto-electronic oscillator. Furthermore, we present and verify for the first time amechanism by which double-Rayleigh-scattering directly generates microwave phase noise.

Portable Optofluidic Absorption flow Analyzer for Quantitative Malaria Diagnosis from Whole Blood

Earu Banoth, Vamshi Kasula, and Sai Gorthi

Doc ID: 271987 Received 22 Jul 2016; Accepted 21 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: Fast and automated diagnostic devices are bound to play a significant role in the on-going efforts towards malaria eradication. In this article, we present the realization of a portable device for quantitative malaria diagnostic testing at the point-of-care. The device measures optical absorbance (at λ = 405 nm) of single cells flowing through a custom designed microfluidic channel. The device incorporates the required functionality to align the microfluidic channel with the optical interrogation region. Variation in optical absorbance is used to differentiate Red blood cells (both healthy and infected) from other cellular components of whole blood. Using the instrument, we have measured single-cell optical absorbance levels of different types of cells present in blood. High-throughput single-cell level measurements facilitated by the device enable detection of malaria, even from a few micro-litres of blood. Further, we demonstrate the detection of malaria from a suspension containing all cellular components of whole blood, which validates its usability in real world diagnostic scenarios.

Thermography for skin temperature evaluation during dynamics exercise, a study case on an incremental maximal test in elite male cyclists

nicola ludwig, athos trecroci, marco gargano, damiano formenti, andrea bosio, ermanno rampinini, and giampiero alberti

Doc ID: 270699 Received 15 Jul 2016; Accepted 21 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: The use of thermal imaging in monitoring the dynamic of skin temperature during a prolonged physical exercise iscentral to assess the athletes’ ability to dissipate heat from the skin surface to the environment. In this study, seven elitecyclists completed an incremental maximal cycling test to evaluate their skin temperature response under controlledenvironmentconditions. Thermal images have been analyzed using a method based on maxima detection (Tmax). Dataconfirmed a reduction in skin temperature due to vasoconstriction during the exercise followed by a temperatureincrement after the exhaustion. A characteristic hot-spotted thermal pattern was found over the skin surface in allsubjects. This research confirmed also the notable ability by highly trained cyclists to modify skin temperature duringan incremental muscular effort. This study gives additional contributions in the understanding the capability of Tmaxmethod applied to thermoregulation and physiological processes.

Experimental Study of Compressive Line Sensing Imaging System in the Turbulence Environment

Bing Ouyang, Weilin Hou, Cuiling Gong, Fraser Dalgeish, Frank Caimi, Anni Dalgleish, GERO NOOTZ, Xifeng Xiao, and David Voelz

Doc ID: 268763 Received 20 Jun 2016; Accepted 21 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: The Compressive Line Sensing (CLS) active imaging scheme has been demonstrated to be effective in the scattering mediums, such as turbid coastal water, fog, and mist, through simulations and test tank experiments. The CLS sensing model adopts the distributed compressive sensing theoretical framework that exploits both intra-signal sparsity and highly correlated nature of adjacent areas in a natural scene. During sensing operation, the laser illuminates the spatial light modulator digital mirror device (DMD) to generate a series of one-dimensional binary sensing pattern from a codebook to encode current target line segment. A single element detector PMT acquires target reflections as the encoder output. The target can then be recovered using the encoder output and a predicted on-target codebook that reflects the environmental interference of original codebook entries. In this work, we investigated the effectiveness of the CLS imaging system in a turbulence environment. Turbulence poses challenges in many atmospheric and underwater surveillance applications. The development of a compact CLS prototype will be discussed. A series of experiments were conducted at the Naval Research Lab's Simulated Turbulence and Turbidity Environment (STTE) with the imaging path subjected to various turbulence intensities using this prototype. The experimental results showed that in the extreme turbulence environment; the time-averaged measurements improved both SNR and resolution of the reconstructed image. The contributing factors for this intriguing and promising result will be discussed.

Object authentication based on compressive ghost imaging

Zhipeng Chen, Jianhong Shi, and Guihua Zeng

Doc ID: 267026 Received 25 May 2016; Accepted 21 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: Ghost imaging is a transverse imaging technique that allows the object to be reconstructed using the correlation between a pair of light fields. As is known, in ghost imaging configurations, a large number of realizations are usually required for reconstruction of the objects. To reduce the number of realizations, some researchers have proposed an object authentication method with computational ghost imaging using realizations of less than 5% of the Nyquist limit. In this paper, we have further improved this method, where the classical correlation algorithm is replaced by a compressive sensing algorithm for object reconstruction. Hence the realizations for object authentication were further reduced from 5% of the Nyquist limit to 2% of the Nyquist limit.

Laser-shocked energetic materials with metal additives: evaluation of chemistry and detonation performance

Jennifer Gottfried and Eric Bukowski

Doc ID: 272827 Received 01 Aug 2016; Accepted 21 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: A focused, nanosecond-pulsed laser has been used to ablate, atomize, ionize, and excite milligram quantities of metal-doped energetic materials which undergo exothermic reactions in the laser-induced plasma. The subsequent shock wave expansion in the air above the sample has been monitored using high-speed schlieren imaging in a recently developed technique, laser-induced air shock from energetic materials (LASEM). The method enables the estimation of detonation velocities based on the measured laser-induced air-shock velocities, and has previously been demonstrated for organic military explosives. Here, the LASEM technique has been extended to explosive formulations with metal additives. A comparison of the measured laser-induced air-shock velocities for TNT, RDX, DNTF, and LLM-172 doped with Al or B to the detonation velocities predicted by the thermochemical code CHEETAH for inert or active metal participation demonstrates that LASEM has potential for predicting the early time (<10 μs) participation of metal additives in detonation events. The LASEM results show that while Al is mostly inert at early times in the detonation event (confirmed from large-scale detonation testing), B is active – and reducing the amount of hydrogen present during the early chemical reactions increases the resulting estimated detonation velocities.

Plasmon Driven Surface Catalysis on Photochemically Deposited based SERS Substrates

Donghui Si, Keyuan Feng, Kenji Kitamura, Anping Liu, Liang Pan, Wenhao Li, Ting Liu, Yingzhou Huang, and Xiaoyan Liu

Doc ID: 273978 Received 17 Aug 2016; Accepted 21 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: For the virtues of convenience and repeatability, photochemically deposited nanoparticles (NPs) as ferroelectric-based SERS substrates have great potential values in the surface plasmon related applications. In this work, the plasmon driven surface catalysis (PDSC) reactions is investigated on the lithium niobate (LiNbO₃) film with photochemically deposited Au NPs. The surface enhanced Raman scattering (SERS) spectra indicates the performance of PDSC reaction on substrate with various Au3+ concentration in photochemical deposition are obvious different. Combining structure characterization and electromagnetic field simulation, this result is mainly contributed to the surface plasmon coupling between Au NPs. Furthermore, the results also point out the exposure time in photochemical deposition play an important role in the PDSC reactions. Our studies on photochemically deposited Au NPs substrate provide a strong support and further understanding to the research on PDSC reaction, also to other surface plasmon related fields. © 2016 Optical Society of America

A New Method to Measure the Phase Modulation Characteristics of Liquid Crystal Spatial Light Modulator

Yunlong Wu, Nie Jinsong, and Li Shao

Doc ID: 267885 Received 13 Jun 2016; Accepted 20 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: The universal liquid crystal spatial light modulator (LC-SLM) is widely used in many aspects of optical study. The working principles and applications of LC-SLM were introduced briefly. The traditional Twyman-Green interference method which was used to measure the phase modulation characteristics of liquid spatial light modulator had some obvious disadvantages in the practical use. To avoid these, the traditional Twyman-Green interference method was improved. Also, a new method to process the interference fringes automatically to measure the shift distances and cycles by computers was proposed. The phase modulation characteristics of P512-1064 LC-SLM produced by Meadowlark Company were measured to verify the validity of the newly proposed method. In addition, in order to compensate and correct the non-linear characteristics of the phase modulation curve, three universal inverse interpolation methods were utilized. The root mean squared error (RMSE) and residual sum of squares (RSS) between the calibrated phase modulation curve and the ideal phase modulation curve were reduced obviously by taking advantage of the inverse interpolation methods. Subsequently, the method of shape preserving subsection cubic interpolation had acquired the best performance with high computation efficiency. The experimental results showed that the phase modulation characteristics of LC-LSM could be acquired and calibrated automatically with convenience and high efficiency by utilizing the newly proposed processing method.

High contrast switching of transmission due to electro-hydrodynamic effect in stacked thin systems of liquid crystals

Svetlana Serak, Uladzimir Hrozhyk, Jeoungyeon Hwang, Nelson Tabiryan, diane steeves, and Brian Kimball

Doc ID: 267891 Received 07 Jun 2016; Accepted 20 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: We study the opportunity of using electro-hydrodynamic instabilities in nematic liquid crystal mixtures with negative dielectric anisotropy for switching laser beams. Switching between naturally transparent and energized diffuse light scattering states is achieved at application of low frequency a.c. electrical field of ~ 10 V amplitude. The specifics of diffuse light scattering state depending on orientation and thickness of liquid crystal layer are revealed. The switching occurs in milliseconds time-scale. Combination of thin flexible liquid crystal cells allows polarization independent fast switching in broadband range of visible wavelengths.

Micro-capillary-based Self-referencing Surface Plasmon Resonance Biosensor for Determination of Transferrin

Wei Peng, Shimeng Chen, Yun Liu, Zigeng Liu, and shuwen chu

Doc ID: 265489 Received 19 May 2016; Accepted 20 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: A novel self-referencing surface plasmon resonance (SPR) biosensor for detection of transferring is demonstrated using micro-capillary as the sensing element. The biosensor employs SPR mode as a measuring signal and Febry-Perot (FP) mode as a referencing signal. The SPR mode is generated in the gold film that is coated on the outside of the capillary; instead, the FP mode is excited in the capillary which is filled with water. The FP mode is sensitive to temperature and insensitive to refractive index (RI), which can be used as a referencing signal to compensate the effects caused by the temperature fluctuation. The sensor provides a high sensitivity of 1783.943nm/RIU (refractive index unit) and a resolution of about 7.287×10−5 RIU. The self-referencing biosensor was applied to measurement of Transferrin Protein. It can monitor the interaction of Transferrin Protein with Anti-Transferrin in real time (0-5.228µM). The simple and low-cost SPR sensor can be used for highly sensitive self-referencing biosensing for further investigations.

Ultra-high-speed spectropolarimeter based on photoelastic modulator

Zhang Rui Zhang-rui, Li Kewu, Yuanyuan Chen, tingdun wen, Minjuan Zhang, Yao Wang, Peng Xue, and Zhi WANG

Doc ID: 264093 Received 27 Apr 2016; Accepted 20 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: Combined with the advantages of photoelastic modulator (PEM) ultra-high-speed modulation, this paper presents amethod of ultra-high-speed spectropolarimeter based on PEM. The method provides the necessary measuring instruments forthe ultra-high-speed polarization spectroscopy. The main idea of this method is that an intensity modulator consisting of tworetarders is placed before the PEM. The incident light under test goes through two retarders to the PEM. The interferencesignals are obtained by the PEM modulation. The different Stokes element interference signals are modulated by the PEM atdifferent positions of the optical path difference (OPD). This method realizes the separation of Stokes element interferencesignals. The interference signals corresponding to each element are extracted, and the incident light Stokes element spectra canbe obtained from the Fourier transforms of the interference signals. The modulation frequency of the PEM is high (tens tohundreds of kilohertz), so this method can realize ultra-high-speed full polarization spectroscopy. A prototype ultra-high-speedspectropolarimeter based on PEM was designed and tested. If the single-sided Fourier transformation is used, the single-sidedinterferogram scanning time is approximately 5 μs (i.e. the prototype is capable of scanning 20000 interferograms persecond). Polychromatic light polarization spectroscopy is measured by the prototype. The experimental results show that theaverage error of the prototype is less than 0.03.

Flexible coaxial laser endoscope with arbitrarily selected spots in endoscopic view for photodynamic tumor therapy

Yan Hu and Ken Masamune

Doc ID: 267920 Received 13 Jun 2016; Accepted 20 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: Photodynamic therapy (PDT), which aims to directlydestruct tumor cells -- without any damage to proximal healthytissue, is widely used in clinic. However, the devices most oftenemployed in hospitals do not readily enable exact control of theirradiated target location. As a result, the laser often irradiatesnot only the tumor, but also neighboring healthy tissues orblood vessels, with more serious consequences resulting fromnecrosis. In this paper, we propose a novel flexible coaxial laserendoscope, which localizes the laser illumination only to theselected tumor target, with minimal illumination of thesurrounding tissue. In this system, visible light is firsttransmitted into an imaging-fiber bundle and then reflected bya polarizing beam splitter, which permits initial imaging of thetumor. Once the tumor target is confirmed, an automated stagemoves the laser fiber head and focusing lens system to theappropriate position. The laser light is then turned on, passedthrough a beam splitter, and focused onto the imaging-fiberbundle, ultimately irradiating only the specified target.To evaluate the effectiveness of the device, we first examinedthe endoscope image quality for MTF50, MTF20 and chromaticaberration, finding high contrast and low aberration. We thenmeasured the laser power at four locations within this system,from the laser fiber head to the endoscope tip. Although somepower loss is observed, the power density at the endoscope tipsatisfies therapy requirements. Finally, the laser positioningaccuracy of our system was measured at 21 positionsthroughout the endoscope image at distances from 20 mm to 50mm. We find that the maximum error is less than 1.2 mm, wellwithin clinical requirement. Therefore, we have developed anoptimal system for PDT that effectively transmits laser light tothe desired target with unprecedented precision, which weanticipate will find wide use in the clinic.

Tri-band transparent conductive coating of indium tin oxide

Huafei Du, Mingyun Lv, Junhui Meng, and Weiyu Zhu

Doc ID: 268805 Received 20 Jun 2016; Accepted 20 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: A tri-band transparent conductive coating for the visible, near-infrared (NIR) and mid-infrared (MIR) was deposited on sapphire substrate. The conductive layer was indium tin oxide (ITO), prepared by radio frequency (RF) magnetron sputtering. Deposition parameters, including RF power, substrate temperature and oxygen flow rate, were optimized to maximize the hall mobility and minimize the carrier concentration, which can improve the optical property without reducing the conductivity of the film. An index-matching stack of MgF2 was developed over ITO deposited at optimized conditions to reduce reflectance losses. The typical average transmission of coated element is about 90.55% in 0.4-1.6µm region and about 73.20% in 3.0-5.0µm region with sheet resistance of 61.2Ω/sq.

Optical rotation compensation for holographic 3D display with 360 degree horizontal viewing zone

Yusuke Sando, Daisuke Barada, and Toyohiko Yatagai

Doc ID: 270838 Received 18 Jul 2016; Accepted 20 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: A method for a continuous optical rotation compensation in a time-division-based holographic three-dimensional (3D) display with a rotating mirror is presented. Since the coordinate system of wavefronts after the mirror reflection rotates about the optical axis along with the rotation angle, the compensation or cancellation is absolutely necessary to fix the reconstructed 3D object. In this study, we address this problem by introducing an optical image rotator based on a right-angle prism that rotates synchronously with the rotating mirror. The optical and continuous compensation reduces the occurrence of duplicate images, which leads to the improvement of the quality of reconstructed images. The effect of the optical rotation compensation is experimentally verified and a demonstration of holographic 3D display with the optical rotation compensation is presented.

Evaluation of organic light-emitting diodes as light sources for a compact optoelectronic integrated neural coprocessor

Huarong Gu and Cardinal Warde

Doc ID: 270021 Received 08 Jul 2016; Accepted 20 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: Organic Light-Emitting Diodes (OLEDs) are a most promising candidate for light sources of the Compact Optoelectronic Integrated Neural (COIN) coprocessor because of its easy integration with the silicon electronics. However, the optical properties of OLEDs are different from that of Vertical-Cavity Surface-Emitting Lasers (VCSELs) which were previously used in the COIN system. The interconnect behavior of the COIN coprocessor is unknown if OLEDs are employed. In this paper, we build a mathematical model of the interconnect scheme of the COIN coprocessor, and investigate the influence of the spectral bandwidth, light-emitting area, and angular emission profile of OLEDs by numerical simulations. The simulation results show that OLEDs with properly selected properties can be used as the light sources for the COIN coprocessor.

Analysis of a Planetary Rotation System for Evaporated Optical Coatings

James Oliver

Doc ID: 273544 Received 09 Aug 2016; Accepted 20 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: The impact of planetary design considerations for optical coating deposition is analyzed, including the ideal number of planets, variations in system performance, and the deviation of planet motion from the ideal. System capacity is maximized for four planets, although substrate size can significantly influence this result. Guidance is provided in the design of high-performance deposition systems, based on the relative impact of different error modes. Errors in planet mounting such that the planet surface is not perpendicular to its axis of rotation are particularly problematic, suggesting planetary design modifications would be appropriate.

Bare and thin-film-coated substrates with null reflection for p- and s-polarized light at the same angle of incidence: reflectance and ellipsometric parameters as functions of substrate refractive index and film thickness

Rasheed Azzam

Doc ID: 273634 Received 11 Aug 2016; Accepted 20 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: Intensity reflectances and ellipsometric parameters of partially clad transparent substrate that supresses thereflection of incident p- and s-polarized light at the same angle of incidence from uncoated and single-layer-coatedareas are determined as functions of normalized film thickness ς and substrate refractive index n2 . The commonpolarizing angle is the Brewster angle of the ambient-substrate interface, and the light beam incident from theambient (air or vacuum) is refracted in the film at 45 angle from the normal to the parallel-plane film boundaries.For n2 ≤ 2, the differential reflection phase shift Δ =δ p −δ s ≈ ±90 for all values of ς so that the Brewster angle is alsoapproximately the principal angle of the film-substrate system independent of film thickness. Accurate techniquesfor monitoring the deposition of such films are also proposed.

MTF performance verification of athermalized large-aperture IR optical system for space environment

SE-CHOL CHOI, BYOUNG-SOO KIM, hyunjin lim, Hongchul Sim, and HONGYEON HWANG

Doc ID: 261474 Received 22 Mar 2016; Accepted 19 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: We develop an athermalized IR optical system operating in the temperature range of 10ºC-30ºC in vacuum. Since large amounts of defocus error can occur in IR optical systems in such an environment, we estimate the amount of defocus induced by the thermoelasic effect, thermo-optic effect, and air-to-vacuum transition. Futhermore, we measure the modulation transfer function (MTF) performance of our IR optical system in a thermal vacuum chamber. Our athermal system design and accurate estimation of the air-to-vacuum transition effect enables the realization of a stable IR optical system for space environment, which exhibits an MTF value greater than 18%.

IR radiation characteristics and operating rangeresearch for a quad-rotor UAV

Rui Guo, Mali Gong, Sifeng He, and Wei Wang

Doc ID: 268976 Received 24 Jun 2016; Accepted 19 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: The security threats caused by multi-rotor UAVs are serious especially in public places. To detect and control multirotorUAVs, the knowledge of IR characteristics is necessary. The IR characteristics of a typical commercial quadrotorUAV are investigated in this paper through thermal imaging with an IR camera. Combining the 3D geometryand IR images of the UAV, a 3D IR characteristics model is established so that the radiant power from differentviews can be obtained. An estimation of operating range to detect the UAV is calculated theoretically using SNR asthe criterion. Field experiments are implemented with an uncooled IR camera in an environment temperature of12℃ and a uniform background. For the front view, the operating range is about 150m, which is close to thesimulation result of 170m.

Moiré alignment algorithm for an aberration-corrected holographic grating exposure system and error analysis

Xulong Zhao, heshig bayan, wenhao li, yanxiu jiang, ying song, xiaotian li, Shan Jiang, and na wu

Doc ID: 268377 Received 15 Jun 2016; Accepted 19 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: To meet the required manufacturing accuracy of high-quality aberration-corrected holographic gratings, we propose a moiré alignment algorithm for the exposure system of holographic gratings. A model holographic grating exposure system is built with multiple degrees of freedom based on optical path function theory. The whole process algorithm is then derived, including the fourth-order orthogonal polynomial of the holographic gratings, fitted aberration coefficients, and an optimized Levenberg–Marquardt algorithm for the exposure system’s recording parameters. Finally, the simulated alignment and error analysis of a 2400 gr/mm aberration-corrected holographic grating’s exposure system are presented. The proposed moiré alignment algorithm for such exposure systems can effectively improve the alignment accuracy, ensuring better holographic grating aberration correction ability.

Iteratively Reconstruct 4D Light Field from Focal Stack

Xuanwu Yin, Guijin Wang, Wentao Li, and Qingmin Liao

Doc ID: 268973 Received 24 Jun 2016; Accepted 19 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: Acquiring and representing the 4D space of rays in the world (the light field) is important for many computer vision and graphics applications. In this paper, we propose a method to acquire 4D light field from focal stack with an iterative method. Firstly, a discrete refocusing equation is derived from integral imaging principle. With this equation, a linear projection system is formulated to model the focal stack imaging process. Then we reconstruct the 4D light field from the focal stack through solving the inverse problem with a filtering based iterative method. The experimental results show that our approach is effective, and outperforms state-of-the-art method in reconstruction accuracy, reduced sampling and occluded boundaries.

Angle- and Polarization-Insensitive MetamaterialAbsorber based on Vertical and Horizontal SymmetricSlotted Sectors

Sungjoon Lim, Nguyen Toan Trung, Dongju Lee, and HYUK-KEE SUNG

Doc ID: 269679 Received 30 Jun 2016; Accepted 19 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: This novel vertically and horizontally symmetric slotted-sector design aims to realize an angle- and polarizationinsensitivemetamaterial absorber. The unit-cell symmetries achieve polarization-insensitivity, while an optimizedslotted-sector inner angle enables angle-insensitivity. Because the absorptivity of a metamaterial absorberdepends on the incident angle and polarization, many researchers have studied angle- and polarization-insensitiveunit cells. In this work, a novel vertically and horizontally symmetric slotted-sector is proposed to realize an angleandpolarization-insensitive metamaterial absorber. The absorber performance is demonstrated with full-wavesimulation and measurements. Angular sensitivity is studied for different slotted-sector inner angles. For an 85°inner angle, the simulated absorptivity exceeds 90% and the frequency variation is less than 1.2% up to 70°incidence. The measured absorptivity at 10.34 GHz is close to 98.5% for all polarization angles at normal incidence.As the incidence angle varies from 0° to 70°, the measured absorptivity at 10.34 GHz remains above 90% in thetransverse electric (TE) mode.

Three-dimensional scene encryption and display based on computer-generated holograms

Liangcai Cao, Dezhao Kong, Guofan Jin, and Bahram Javidi

Doc ID: 270014 Received 07 Jul 2016; Accepted 19 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: An optical encryption and display method of a three-dimensional (3-D) scene is proposed based on computer-generated holograms (CGHs) using a single phase-only spatial light modulator. The 3-D scene is encoded as one complex Fourier CGH. The Fourier CGH is then decomposed into two phase-only CGHs with random distributions by the vector stochastic decomposition algorithm. Two CGHs are interleaved as one final phase-only CGH for optical encryption and reconstruction. The proposed method can support high-level nonlinear optical 3-D information security and complex amplitude modulation of the optical field. The exclusive phase key offers strong resistances of decryption attacks. Experimental results demonstrate the validity of the novel method.

Absorption correction and phase function effects on the closure of apparent optical properties

Jaime Pitarch, Gianluca Volpe, Simone Colella, Rosalia Santoleri, and Vittorio Brando

Doc ID: 270049 Received 07 Jul 2016; Accepted 19 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: We present a closure experiment between new IOP (absorption a, scattering b, backscattering bb) and AOP (remote-sensing reflectance Rrs, irradiance reflectance R and anisotropic factor at nadir Qn) data of Ionian and Adriatic seawaters, from very clear to turbid waters, ranging across one order of magnitude in Rrs. The internal consistency of the IOP-AOP matchups was investigated though radiative transfer closure. Using the in-situ IOPs, we predicted the AOPs with Hydrolight. Analysis in detail of the closure problem depicts a much more complex scenario than previously published. Closure was limited by two unresolved issues, one regarding processing of in-situ data and the other related to radiative transfer modelling. First, different correction methods of the absorption data measured by the Wetlabs ac-s produced high variations in simulated reflectances reaching 40 % for the highest reflectances in our dataset. Second, the lack of detailed volume scattering function measurements forces to adopt analytical functions that are consistent with a given particle backscattering ratio. Phase functions having reasonable angular shapes respect to measurements at few backward angles were Fournier-Forand (Mobley and Twardowski) and two-term Kopelevich. Between these phase functions, induced changes in the simulated reflectances varied within 20 %. Additionally, closure of Qn was generally not successful considering radiometric uncertainties. In particular, simulated Qn overestimated low values and underestimated high values, especially at 665 nm, where Hydrolight was unable to predict measured Qn values greater than 6 sr. The physical nature of Qn makes this mismatch almost independent of the measured IOPs, thus precluding Qn tuning by varying the former. Phase functions choice among the former mentioned could alter Qn within 10 %. The non-closure of Qn might be caused by inaccurate phase function, but also to intrinsic radiative transfer modelling issues. For the future, it remains the task of accurate absorption and phase functions measurements, especially at red wavelengths.

A design of terahertz photonic crystal transmission filter containing ferroelectric material

Chien-Jang Wu, JIAN-JIE CHEN, KAI-CHUN CHANG, and Tzu Chyang King

Doc ID: 274090 Received 19 Aug 2016; Accepted 19 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: The ferroelectric material KTaO3 (KTO) has a very high refractive index, which is advantageous to the photonic crystal (PC) design. KTO polycrystalline crystal has a high extinction coefficient. In this work, we theoretical study the transmission properties of PC band pass filter made of polycrystalline KTO at terahertz (THz) frequencies. Our results show that the defect modes of usual PC narrowband filters are no longer exist because of the existence of the high loss. We provide a new PC structure for the high extinction materials and it has defect modes in its transmittance spectra, providing a possible band pass filter design in the THz region.

Independent component analysis for enhancement ofan FMCW optical ranging technique in turbid waters

David Illig, William Jemison, and Linda Mullen

Doc ID: 267187 Received 02 Jun 2016; Accepted 19 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: Optical detection and ranging in turbid waters are challenged by the effects of absorption and scattering. Inparticular, backscatter creates a clutter return which can mask the presence of weak underwater targets. Thiswork explores the use of independent component analysis (ICA), a statistical signal processing approach, torecover weak targets from strong backscatter in turbid waters using a frequency-modulated continuous-wave(FMCW) optical rangefinder. ICA uses statistical differences between target and backscatter returns to suppress thebackscatter return. In laboratory test tank experiments, the use of ICA is observed to improve probability ofdetection at various turbidities and extend target detection range by four optical attenuation lengths.

Four step shear method for absolute measurement of flat surface based on phase measuring deflectometry

Dahai Li, Kewei E, Chen Zhang, Tao Zhang, Mengyang Li, Qin Wang, Chengying Jin, and Zhao Xiong

Doc ID: 270884 Received 19 Jul 2016; Accepted 19 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: This article proposes a new shearing approach to eliminate the systematic errors in Phase measuringdeflectometry (PMD). Besides of a normal measurement using PMD, another three measurements are taken whenthe test surfaces are translated and rotated with an amount of known magnitude in our proposed method. The fourmeasurements give three sheared wavefronts, and then the difference Zernike polynomials fitting and leastsquares algorithm are proposed to reconstruct the true test surface figure. The proposed method is demonstratedand verified through computer simulation and experimental results. The error propagation when the shearedwavefronts include random noise and the introduced errors due to the incorrect shearing values are bothanalyzed.

Acidic magnetorheological finishing of infraredpolycrystalline materials

sivan salzman, Henry Romanofsky, Garrett West, Kenneth Marshall, Stephen Jacobs, and John Lambropoulos

Doc ID: 270915 Received 20 Jul 2016; Accepted 19 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: Chemical-vapor–deposited (CVD) ZnS is an example of a polycrystalline material that is difficult to polish smoothlyvia the magnetorheological–finishing (MRF) technique. When MRF-polished, the internal infrastructure of thematerial tends to manifest on the surface as millimeter-sized “pebbles,” and the surface roughness observed isconsiderably high. The fluid’s parameters important to developing a magnetorheological (MR) fluid that is capableof polishing CVD ZnS smoothly were previously discussed and presented. These parameters were acidic pH (~4.5)and low viscosity (~47 cP). MRF with such a unique MR fluid was shown to reduce surface artifacts in the form ofpebbles; however, surface microroughness was still relatively high because of the absence of a polishing abrasivein the formulation. In this study, we examine the effect of two polishing abrasives—alumina and nanodiamond—onthe surface finish of several CVD ZnS substrates, and on other important IR polycrystalline materials that werefinished with acidic MR fluids containing these two polishing abrasives. Surface microroughness results obtainedwere as low as ~28 nm peak-to-valley and ~6-nm root mean square.

Single-shot Network Analyzer for Extremely Fast Measurements

Cejo Lonappan, Bahram Jalali, and Asad Madni

Doc ID: 272851 Received 03 Aug 2016; Accepted 19 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: A new instrument for fast measurement of frequency response of high bandwidth optical and electronic devices is reported. Single shot frequency spectrum measurements are enabled by the time-stretch technology. An extremely fast measurement time of 27 ns is reported for the instrument. The reported instrument enables single-shot impulse response measurements with 40 GHz bandwidth, which could be extended to beyond 100 GHz by using a faster electro-optic modulator. An ultra-low intra-pulse jitter of 31.5 fs is reported for the proposed instrument. The impulse responses measured using this technique are shown to correspond consistently with the manufacturer's specifications for the device under test. The reported instrument makes possible high-speed network parameter measurements thereby enabling high-speed production-level testing of high bandwidth opto-electronic devices/circuits/subsystems/systems and complex permittivity measurement of dielectric materials at a much reduced test time lowering the test costs in a production environment.

Gain properties of an uncoatd and a chiral coated slotted sphereembedded in a chiral background

zeeshan awan

Doc ID: 267012 Received 25 May 2016; Accepted 18 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: The gain properties of an uncoated and a chiral coated slottedsphere embedded in a chiral background have been investigated usingnumerical simulations. It is studied that a chiral background mediumenhances the gain of an uncoated slotted sphere in the forward directionas compared to the free space background. It is shown that the forwarddirection gain of a chiral coated slotted sphere embedded in a chiralbackground increases with the increase in the the background chirality.It is further studied that the maximum gain moves away from thepolar direction towards the forward direction as the chirality of thecoating increases for a fixed background chirality. Also this maximumgain gradually decreases as the chirality of the coating increases. Aninteresting feature of an angular window is introduced for a chiralcoated slotted sphere embedded in a chiral background where the gainis nearly constant for a specific range of angles.

Ultrashort pulsed laser induced heating- nanoscalemeasurement of the internal temperature ofdielectrics using black-body radiation

Jing Qian, Chengwei Wang, Yuanyuan Huang, Hongjin Li, Kongyu Lou, Guande Wang, and Quanzhong Zhao

Doc ID: 268784 Received 20 Jun 2016; Accepted 18 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: Nanoscale measurement of the temperature in the bulk of dielectrics initiated by a single ultrashort laser pulsewas first investigated by black-body radiation. A structureless broad continuum emission has been recorded at aninterval delay of 2 ns with temporal gate of 2 ns and spectral resolution of about 0.137 nm, which provides thehighest temporal and spectral precision ever. The temporally resolved emission spectrum was proved to be blackbodyradiation in nature and temperature was obtained by fitting the radiation with Planckian formula. Pulseenergy was varied from 110 to 270 μJ at 600 fs and pulse duration at 0.83 ns was also used. Temperature exhibiteda small variation with increasing pulse energy at 600 fs. However, due to energy transfer from heated electrons tolattice, temperature was sharply increased at pulse duration of 0.83 ns. It was estimated that heat accumulationstarted at 0.42~0.47 MHz for laser pulse at 600 fs while 0.25 MHz for laser pulse at 0.83 ns.

Resonant structures for infrared detection

K. Choi, Steven Allen, Jason Sun, Yajun Wei, Kimberley Olver, and Richard Fu

Doc ID: 269779 Received 08 Jul 2016; Accepted 18 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: We are developing resonator-QWIPs for long wavelength applications. Detector pixels with 25 μm pitch were hybridized to fanout circuits for radiometric measurements. With a moderate doping of 0.5 × 10¹⁸ cm¨³, we achieved a quantum efficiency of 37% and conversion efficiency of 15% in a 1.3 μm-thick active material and 35% QE and 21% CE in a 0.6 μm-thick active material. Both detectors are cutoff at 10.5 μm with a 2 μm bandwidth. The temperature at which photocurrent equals dark current is about 65 K under F/2 optics. The thicker detector shows a large QE polarity asymmetry due to nonlinear potential drop in the QWIP material layers.

Fluence-induced reversal of saturable absorption in a ruthenium-based porphyrin

Robert Hoffman, Andrew Mott, Micahel Ferry, and Timothy Pritchett

Doc ID: 270203 Received 11 Jul 2016; Accepted 18 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: Experimental nonlinear absorption data obtained using the open-aperture Z-scan technique are presented for 2,3,7,8,12,17,18-octaethyl-21H, H-porphine ruthenium (II) carbonyl in tetrahydrofuran. These data show saturation of nonlinear absorption that turns off at high fluences and is replaced by induced absorption (reverse saturable absorption). Large-angle scattering measurements demonstrate that the induced absorption is real and not merely the result of scattering of light outside of the collection aperture of the detector by scattering centers induced at high fluence. A possible mechanism based on a four-band effective rate equation model is proposed. The model is used to accurately predict the results of Z-scans taken at different pulse energies and to extract values for excited state lifetimes and absorption cross sections from the experimental data.

Duty cycle estimate of photoresist gratings via monitoring TM/TE diffraction efficiency ratio during development

Shen Biyao, Zeng Lijiang, and Lifeng Li

Doc ID: 270781 Received 19 Jul 2016; Accepted 18 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: We present an in situ duty cycle control method that relies on monitoring the TM/TE diffraction efficiency ratio of the −1st transmitted order during photoresist development. Owing to the anisotropic structure of a binary grating, at an appropriately chosen angle of incidence, diffraction efficiencies in TE and TM polarizations vary with groove depth proportionately, while they vary with duty cycle differently. Thus measuring the TM/TE diffraction efficiency ratio can help estimate duty cycle during development while eliminating the effect of photoresist thickness uncertainty. We experimentally verified the feasibility of this idea by fabricating photoresist gratings with different photoresist thicknesses. The experimental results were in good agreement with theoretical predictions.

Analytical solution of the correlation transport equation with static background: beyond diffuse correlation spectroscopy

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

Doc ID: 272427 Received 26 Jul 2016; Accepted 18 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: The correlation transport equation (CTE) is the natural generalization of the theory for diffusion correlation spectroscopy (DCS)and represents a more precise model when dealing with measurements of particles movement in fluids orred blood cells flow in biological tissues. Unfortunately, CTE is not methodically used duethe complexity of finding solutions.It is shown that actually a very simple modification of the theory/softwarefor the solution of the radiative transport equation, allows one to obtain exact solutions of the CTE. The presence of a static background is also taken into account and its influence on the CTE solutions is discussed.The proposed approach permits to easily work beyond the diffusion regime and potentially for any optical and/or physiological value. The validity of the approach is demonstrated by using ``gold standard' Monte Carlo simulations.

Generation of high intensity spectral supercontinuum of more than two octaves in a water jet

Maksim Melnik, Anton Tsypkin, Sergey Putilin, Victor Bespalov, Sergey Kozlov, and Evgenii Makarov

Doc ID: 270048 Received 12 Jul 2016; Accepted 16 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: In this paper, we demonstrate experimentally for the first time to our knowledge the generation of spectral supercontinuum (SC) of more than two octaves with high intensity in a water jet. The spectrum of the generated SC extends from 350 to 1400 nm with intensities up to 10¹¹ W/cm² and its generation efficiency is more than 50%. For the pump intensity 3.0x10¹² W/cm² in the spectral range from 400 to 800 nm spectrum is nearly flat (less than 40% deviation), which is useful for many applications.

Virtual pyramid wavefront sensor for phase unwrapping

Vyas Akondi, Brian Vohnsen, and Susana Marcos

Doc ID: 267451 Received 03 Jun 2016; Accepted 16 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: Noise affects wavefront reconstruction from wrapped phase data. A novel method of phase unwrapping is proposed with the help of a virtual pyramid wavefront sensor. The method was tested on noisy wrapped phase images obtained experimentally with a digital phase-shifting point diffraction interferometer. The virtuality of the pyramid wavefront sensor allows easy tuning of pyramid apex angle and modulation amplitude. It is shown that an optimal modulation amplitude obtained by monitoring the Strehl ratio helps in achieving better accuracy. Through simulation studies and iterative estimation, it is shown that the virtual pyramid wavefront sensor is insensitive to random noise.

Urban monitoring from infrared satellite images

Matteo Ghellere, Alice Bellazzi, Lorenzo Belussi, and Italo Meroni

Doc ID: 268619 Received 24 Jun 2016; Accepted 16 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: Starting from an experimental campaign in Milan, the article describes how the infrared (IR) signal, recorded byLandsat 8 sensors, can be used to evaluate and monitor key urban scale environmental variables. The possibility tocombine different spectral bands of the infrared signal with previously collected spectral bands is highlighted. Themonitored variables have been mapped in geo-referenced images using the GIS instruments. In this way, a mappingdatabase is created to be used as a benchmark to study the urban heat islands (UHI) and the environmentalchanges over the years.

The mirrors used in the LIGO interferometers for the first detection of gravitational waves

Laurent Pinard, Christophe MICHEL, Benoit SASSOLAS, laurent balzarini, Jerome Degallaix, Vincent Dolique, Raffaele Flaminio, Daniele Forest, Massimo Granata, Nicolas Straniero, julien teillon, Gianpietro Cagnoli, and Bernard Lagrange

Doc ID: 274558 Received 31 Aug 2016; Accepted 16 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: For the first time, a direct detection of gravitational wave occurred in the LIGO interferometers. These advanced detectors need large fused silica mirrors having optical and mechanical properties never reached up to now. This paper details the main achievements of these IBS coatings.

Low-loss and bend-insensitive terahertz fiber using rhombic shaped core

Md. Rabiul Hasan, Md. Ariful Islam, Md. Shamim Anower, and S. M. Razzak

Doc ID: 272789 Received 29 Jul 2016; Accepted 16 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: A novel porous-core photonic crystal fiber is presented and its guiding properties are numerically investigated by using finite element method. It is demonstrated that by introducing a rhombic shaped core made of circular air holes inside the conventional hexagonal cladding, it is possible to obtain very low bending loss of 3.04×10-11 cm-1 at the operating frequency of 1.0 THz. In addition to this, low effective material loss of 0.089 cm-1, very small confinement loss of 1.17×10-3 dB/cm and modal birefringence of order 10-3 are achieved for optimal design parameters. Other guiding properties including effective area, dispersion and higher order mode characteristics are also discussed thoroughly. The design of this porous fiber is relatively simple since it contains fewer air holes and consists of circular air holes only. Due to promising wave guiding properties, the proposed fiber would have a great potential for THz sensing, imaging and flexible communication applications.

Automatic Visual Inspection of missing Split Pin in China Railway High-speed

Shengfang Lu and zhen liu

Doc ID: 268789 Received 20 Jun 2016; Accepted 15 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: The split pin (SP) on the caliper brake (CB) is a vital component of brake system of a bogie traveling along the ChinaRailway High-speed (CRH), and the absence of the SP could cause serious train accidents. A new automatic visualinspection method is proposed for the quick and accurate detection of SP faults of the CRH. The proposed approachis based on the histogram of gradient (HOG) combined with the complete local binary pattern (CLBP). First, a fastpyramid template matching (FPTM) technique is presented for localizing the region of interest to reduce thesearching scope. Under the multi-resolution pyramid model for target localization, a coarse-to-fine strategy isemployed to ensure that the recognizing speed of the SP for the entire image is increased significantly. Second, ahierarchical framework is adopted at the localizing and inspecting stages of the SP to automatically implement theinspection tasks. To increase the robustness to the outside complex illumination, the HOG feature for localizing thetarget and the CLBP feature for examining the state of the SP (i.e., missing or not-missing) are extracted in the Sobelgradient domain. The localization and recognition stages are both fulfilled through the use of their respectiveintersection kernel support vector machine (IKSVM) classifiers and corresponding features. In conclusion,experimental results indicate that the inspection system achieves a high accuracy rate of more than 99.0% and areal-time speed, thus proving that the proposed method is effective for the fault inspection of SP and can satisfy therequirements of CRH’s actual application.

Stable multi-wavelength fiber lasers for temperature measurements using an optical loop mirror

Silvia Diaz, Abian Socorro, Rodolfo Martínez-Manuel, Ruben Fernandez, and Ioseba Monasterio

Doc ID: 269335 Received 27 Jun 2016; Accepted 15 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: In this work, two novel stable multi-wavelength fiber laser configurations are proposed and demonstrated by using a spool of single-mode fiber as optical loop mirror and one or two fiber ring cavities, respectively. The lasers are comprised of fiber Bragg grating reflectors as the oscillation wavelength selecting filters. The influence of the length of the spool of fiber on the laser stability both in terms of wavelength and laser output power was investigated. Application for temperature measurement is also shown.

Barrier layer induced channeling effect of As ion-implantation in HgCdTe and its influences on electrical properties of p-n junctions

Changzhi Shi, Chun Lin, Yanfeng Wei, Lu Chen, and Mingxing Zhu

Doc ID: 269684 Received 30 Jun 2016; Accepted 14 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: The HgCdTe layers (xCd~0.285 and 0.225) were grown by MBE and LPE, respectively, followed by the deposition ofCdTe and ZnS films as barrier layers by thermal evaporation. Then, the p-on-n photodiodes were fabricated byarsenic ion implantation, Hg overpressure annealing, passivation and metallization. The SIMS and TEM resultsindicate that the evaporated CdTe layer with column structure induces the channeling effect of arsenic ionimplantation causing the device performance degradation. This effect could be suppressed by depositing CdTe filmwith layered structure through E-beam evaporation. Finally, the I-V and C-V characteristics of these p-n junctionswere estimated and analyzed.


Carosena Meola, Simone Boccardi, and Giovanni Carmagno

Doc ID: 267550 Received 01 Jun 2016; Accepted 14 Sep 2016; Posted 15 Sep 2016  View: PDF

Abstract: The present work is concerned with the use of a QWIP infrared camera to measure very small temperaturevariations, which are related to thermo-elastic/plastic effects, developing on composites under relatively lowloads, either periodic or due to impact. As it comes out from previous work, some temperature variations aredifficult to measure being at the edge of the IR camera resolution and/or affected by the instrument noise.Conversely, they may be valuable to get either information about the material characteristics and its behaviourunder periodic load (thermo-elastic), or to assess the overall extension of delaminations due to impact (thermoplastic).An image post-processing procedure is herein described which, with the help of a reference signal, allowsfor suppression of the instrument noise and better discrimination of thermal signatures induced by the twodifferent loads.

Effects of temperature on the removal efficiency ofKDP crystal during the process of magneto-rheologicalwater-dissolution polishing

Yifan Zhang, Yifan Dai, Hao Hu, and guipeng tie

Doc ID: 267716 Received 06 Jun 2016; Accepted 14 Sep 2016; Posted 15 Sep 2016  View: PDF

Abstract: As a kind of important nonlinear optical element, KDP crystal has great demand in the inertial confinementfusion (ICF) system. Based on the dissolution mechanism of solid materials, the factors that affect the materialremoval rate of KDP crystal in magneto-rheological (MR) water-dissolution polishing are investigated toimprove the machining efficiency. It is found that the material removal rate is proportional to the product ofthe saturation concentration and diffusion coefficient, and the relationship between the removal efficiency andthe temperature meets the unilateral Gaussian function. Polishing experiments are carried out on amagneto-rheological finishing (MRF) machine with self-designed MRF fluid heating devices. The experimentalresults show that practical efficiency - temperature curve is consistent with the theoretical curve, and themaximum machining efficiency increases by about 50% with the rise of temperature from 294K to 302K,.Meanwhile, when the MR fluid temperature is lower than 308K, the crystal surface quality and surfaceroughness in different processing temperatures have no remarkable difference with constant crystaltemperature (294K). This research indicates that it is feasible to drastically improve KDP crystal MRFefficiency by controlling the processing temperature.

Determination of optical constants including surface characteristics of optically thick nanostructured Ti films: Analyzed by Spectroscopic ellipsometry

Ramesh Chandra, jyoti jaiswal, Satyendra Mourya, Gaurav Malik, Samta Chauhan, Amit Sanger, Ritu Daipuriya, and Manpreet Singh

Doc ID: 268107 Received 13 Jun 2016; Accepted 14 Sep 2016; Posted 15 Sep 2016  View: PDF

Abstract: In the present work, optically thick nanostructured titanium (Ti) films of thickness ranging from ~100-900 nmwere deposited on glass substrate by DC magnetron sputtering at room temperature. Microstructural and surfaceproperties of the samples were studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Themorphological results revealed a systematic normal grain growth mechanism with increasing thickness analyzedby Scanning electron microscope (SEM). The influence of thickness on film surface roughness has been investigatedby Atomic force microscopy (AFM). The optical dispersion behavior was examined by spectroscopic ellipsometry(SE) over the long wavelength range of 246-1688 nm. The experimentally observed SE parameters weretheoretically fitted with Drude-Lorentz and Bruggeman effective medium approximation theory. The surfaceproperties of Ti film measured by XPS and AFM were further accounted in the optical model to determine opticalconstants (n and k) and the obtained results are expected to be the best available for bulk Ti metal.

Lasers and infrared thermography: advantageous cooperation

Boris Vainer

Doc ID: 269633 Received 30 Jun 2016; Accepted 14 Sep 2016; Posted 15 Sep 2016  View: PDF

Abstract: In the brief review, the beneficial outcomes arisen from a simultaneous use of the laser- and infrared thermography (IRT)-based techniques are demonstrated. The most recent literary and original experimental results collected from different research and practical areas are presented. It is shown that the modern IRT acts as an indispensable laser partner in various biomedical and many other applications and technologies. And vice versa, the laser-based methods and techniques often serve as an appropriate research instrument enriching IRT measurement data with an independently obtained information.

Tunable Yb:CaF2–SrF2 laser and femtosecondmode-locked performance based on SESAM

Feng Zhang, Hongtong Zhu, Jie Liu, Yifeng He, Peng Jiang, Fei Tang, and Liangbi Su

Doc ID: 269716 Received 07 Jul 2016; Accepted 14 Sep 2016; Posted 15 Sep 2016  View: PDF

Abstract: We experimentally demonstrate an effective continuous-wave tunable operation and femtosecond passivelymode-locked pulse from a Yb:CaF2–SrF2 mixed crystal laser for the first time. Pumped by a 977 nm fibercoupled laser diode (LD), continuous-wave mode-locked (CWML) pulse as short as 634 fs was generated. Theshortest pulse operated under a repetition rate of 87 MHz at the central wavelength of 1047 nm. Thecalculated time-bandwidth product was 0.503, which was 1.6 times as the Fourier transform-limitedsech2-shape pulses.

Method for End Face Treatment of Specialty Optical Fiber with Thick-walledSilica Glass Tubes

Xinyang Su, Yi Zheng, Junpeng Yang, Qingling Li, and Jianwei Li

Doc ID: 269940 Received 14 Jul 2016; Accepted 14 Sep 2016; Posted 15 Sep 2016  View: PDF

Abstract: A “cleaving-polishing” process for end face treatment of specialty fiber supported by thick-walled silica glass tubesis proposed. The fiber tension is determined by the fiber fracture theory for improved cleaving. This methodovercomes polishing problems caused by steel or ceramic ferrules. Approximately 20 minutes on average isrequired for polishing a specialty fiber end face with a sampling roughness of 7.42 nm, confirmed by microscopy(400×) and interferometry. A comparison of laser coupling efficiencies between fibers with cleaved ends and fiberswith polished ends showed that the coupling efficiency of the former could be enhanced by 15% through polishing.

All-Optical Detection of Acoustic Pressure Waves with applications in Photo-Acoustic Spectroscopy

Mikael Lassen and Philip Westergaard

Doc ID: 273748 Received 12 Aug 2016; Accepted 14 Sep 2016; Posted 15 Sep 2016  View: PDF

Abstract: An all-optical detection method for the detection of acoustic pressure waves is demonstrated. The detection system is based on a stripped (bare) single-mode fiber. The fiber vibrates as a standard cantilever and the optical output from the fiber is imaged to a displacement-sensitive optical detector. The absence of a conventional microphone makes the demonstrated system less susceptible to the effects that a hazardous environment might have on the sensor. The sensor is also useful for measurements in high temperature (above $200^{\circ}$C) environments where conventional microphones will not operate. The proof-of-concept of the all-optical detection method is demonstrated by detecting sound waves generated by the photo-acoustic effect of NO$_2$ excited by a 455 nm LED, where a detection sensitivity of approximately 50 ppm was achieved.

Comparison of quantitative defect characterisation using flash and lock-in thermography

Christiane Maierhofer, Mathias Röllig, Rainer Krankenhagen, and Philipp Myrach

Doc ID: 272677 Received 28 Jul 2016; Accepted 13 Sep 2016; Posted 14 Sep 2016  View: PDF

Abstract: Using optical excitation sources for active thermography enables a contactless, remote and non-destructive testing of materials and structures. Currently, two kinds of temporal excitation techniques have been established: pulse or flash excitation using mostly flash lamps and periodic or lock-in excitation using halogen lamps, LED or Laser arrays. From the experimental point of view, both techniques have their advantages and disadvantages. Concerning the comparison of the testing results of both techniques, only very few studies have been performed in the past. In this contribution, the phase values obtained at flat bottom holes in steel and CFRP and the spatial resolution measured at crossed notches in steel using flash and lock-in excitation are compared quantitatively.

Digital passband processing of wideband modulated optical signals for enhanced underwater imaging

Linda Mullen, Justin Nash, and Robert Lee

Doc ID: 268164 Received 15 Jun 2016; Accepted 13 Sep 2016; Posted 14 Sep 2016  View: PDF

Abstract: Radar modulation, demodulation and signal processing techniques have been merged with laser imaging to enhance visibility in murky underwater environments. The modulation provides a way to reject multiply scattered light that would otherwise reduce image contrast and resolution. Recent work has focused on the use of wideband modulation schemes and digital passband processing to resolve range details of an underwater scene. Use of the CLEAN algorithm has also been investigated to extract object features that are obscured by scattered light. Results from controlled laboratory experiments show an improvement in the range resolution and accuracy of underwater imagery relative to data collected with a conventional short pulse system.

A polarimetric dehazing method for visibility improvement based on visible and infrared image fusion

Jian Liang, Wenfei Zhang, Liyong Ren, Haijuan Ju, and EnShi Qu

Doc ID: 270104 Received 07 Jul 2016; Accepted 13 Sep 2016; Posted 14 Sep 2016  View: PDF

Abstract: Polarimetric dehazing methods have proven effective in enhancing the quality of chromatic hazy images. Considering that the infrared radiance has better capacity in travelling through the haze, in this paper we propose a polarimetric dehazing method based on visible and infrared image fusion to improve the visibility of hazy images, especially for dense haze condition. Experimental results demonstrate that the visibility of hazy images can be effectively enhanced, and the color information can be finely maintained. The visibility of dehazed images can be promoted at least 100%. This kind of dehazing method can be used widely in many dehazing applications.

Determination of global and diffusePhotosynthetically Active Radiation from Multi-FilterShadowband Radiometer (MFRSR)

Pamela Trisolino, Alcide Di Sarra, Daniela Meloni, and Giandomenico Pace

Doc ID: 272455 Received 04 Aug 2016; Accepted 13 Sep 2016; Posted 14 Sep 2016  View: PDF

Abstract: A method to estimate the photosynthetically active radiation from multi-filter shadowband radiometer, MFRSR,measurements, was developed and tested from observations carried out on the island of Lampedusa, in the centralMediterranean. Calibrated irradiances in the 4 MFRSR bands within the PAR spectral range were combined linearlyto estimate PAR. The coefficients of the linear combination were derived with the least squared method fordifferent sky conditions. The analysis shows that global PAR irradiance may be estimated with an overalluncertainty of 4-6%. The applicability of the method was tested by using radiative transfer simulations of thediffuse irradiance spectrum, for different aerosol and cloud conditions. The diffuse PAR irradiance can beestimated with an overall accuracy of less than 9%. The application of this method allows to obtain continuous andlong-term calibrated measurements of global and diffuse PAR; in addition, information on the spectral dependencyof PAR can be derived from the signals in the 4 bands.

2016 Topical Meeting on Optical Interference Coatings: Manufacturing Problem Contest [invited]

Daniel Poitras, Li Li, Michael Jacobson, and Catherine Cooksey

Doc ID: 275145 Received 02 Sep 2016; Accepted 13 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: For the Manufacturing Problem contest, participants were asked to fabricate on provided blank substrates a challenging filter with specific reflectance and transmittance targets covering a wavelength range from 400 nm to 1100 nm. The problem was selected such that in order to achieve a performance close to the targets, a submitted filter had to include at least one thin absorbing layer. Nine teams from six countries participated in the contest using different deposition techniques. The teams’ designs had a number of layers varying from 36 to 5, and a total thickness from 2.0 µm to 14.6 µm. The performances of all submitted filters were measured by two independent laboratories and the results were presented at the Optical Interference Coating meeting in June 2016.

Infrared thermographic inspection of water ingress in composite honeycomb panels

Vladimir P Vavilov, Denis Nesteruk, and Yang-Yang Pan

Doc ID: 270668 Received 15 Jul 2016; Accepted 13 Sep 2016; Posted 20 Sep 2016  View: PDF

Abstract: Quantitative aspects of infrared thermographic detection of water in aviation honeycomb panels are discussed in the framework of both 1D analytical and 3D numerical models. A criterion of transition from 3D to 1D test geometry is introduced, and the influence of honeycomb cell structure on modeling results is demonstrated. Optimal test conditions are formulated both theoretically and experimentally in two practical cases where the gravity force causes the water to be against the facesheet at the bottom of the cells or if there is an air gap at the top of the cells under the upper facesheet.

Polarized Skylight Navigation

Moshe Hamaoui

Doc ID: 272747 Received 29 Jul 2016; Accepted 13 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: Vehicle state estimation is an essential prerequisite for navigation. The present approach seeks to useskylight polarization to facilitate state estimation under autonomous unconstrained flight conditions. Atmosphericscattering polarizes incident sunlight such that solar position is mathematically encoded in theresulting skylight polarization pattern. Indeed, several species of insects are able to sense skylight polarizationand are believed to navigate polarimetrically. Sun-finding methodologies for polarized skylightnavigation (PSN) have been proposed in the literature, but typically rely on calibration updates to accountfor changing atmospheric conditions and/or are limited to 2D operation. To address this technology gap, agradient-based PSN solution is developed based upon the Rayleigh sky model. The solution is validatedin simulation, and effects of measurement error and changing atmospheric conditions are investigated.Finally, an experimental effort is described wherein polarimetric imagery is collected, ground-truth isestablished through independent imager-attitude measurement, the gradient-based PSN solution is applied,and results are analyzed.

Propagation of electromagnetic multi-Gaussian Schell-model beams with astigmatic aberration in turbulent ocean

Daomu Zhao and Chuanyi Lu

Doc ID: 272482 Received 26 Jul 2016; Accepted 12 Sep 2016; Posted 14 Sep 2016  View: PDF

Abstract: An analytical expression for the elements of the cross-spectral density matrix of electromagnetic multi-Gaussian Schell-model beams with astigmatic aberration propagating through the turbulent ocean is derived. We investigate the statistical characteristics of the beams on propagation in great detail. It is found that, due to astigmatism, the circular symmetry of such beams suffers a certain degree of damage in the near field. In addition, astigmatism also destroys the attractive far-field flat profiles in free space. Meanwhile, we also show that astigmatism and oceanic turbulence both have certain effects on the spectral degree of polarization.

LIBS and AR techniques to discriminate healthy and cancerous breast tissues

Parviz Parvin, fatemeh ghasemi, Najme Sadat Hosseinimotlagh, Ahmad Amjadi, and shahriar abachi

Doc ID: 272226 Received 22 Jul 2016; Accepted 12 Sep 2016; Posted 14 Sep 2016  View: PDF

Abstract: Laser induced breakdown spectroscopy (LIBS) and subsequent acoustic response (AR) during micro–plasmaformation are employed to identify cancerous human breast tissues. The characteristic optical emissions identifyCa, Na and Mg rich species in cancerous tissues compared to those of healthy ones. Furthermore, we show that thecharacteristic parameters of the micro–plasma, generated on the unhealthy tissues, are elevated. We report higherdecibel (dB) audio signals emanating from laser induced micro–plasma and a subsequent audio blue–shift formalignant tissues. The higher abundance of trace elements in cancerous tissues as well as higher plasmatemperature and electron density in laser induced micro–plasma (leading to a stronger shockwave), intensify theacoustic signals.


Detlef Mueller, Alexei Kolgotin, Eduard Chemyakin, and Anton Romanov

Doc ID: 266604 Received 29 Aug 2016; Accepted 12 Sep 2016; Posted 14 Sep 2016  View: PDF

Abstract: Mutliwavelength Raman/high-spectral-resolution lidars that measure backscatter coefficients at 355, 532, and 1064 nm and extinction coefficients at 355 and 532 nm can be used for the retrieval of particle microphysical parameters such as effective and mean radius, number, surface-area and volume concentrations, and complex refractive index from inversion algorithms. In this study we investigate correlation properties that may exist between the optical properties measured with these lidars and the underlying microphysical properties. Goal of the study is if results from data inversion can be improved, or if data inversion can even be replaced with simpler schemes if such correlation properties are used in the inversion in terms of a-priori or a-posteriori constraints. We made the simplifying assumption of error-free optical data in order to find out what correlation in the best case situation would exist. Clearly, for practical applications, erroneous data need to be considered, too. On the basis of simulations with synthetic optical data we find the following results which hold true for arbitrary particle size distributions, i.e., regardless of the modality or the shape of the size distribution function: surface-area concentrations and ex-tinction coefficients are linearly correlated with a correlation coefficient above 0.99. We also find a correlation coefficient above 0.99 for the extinction coefficient versus (1) the ratio of the volume concentration to effective radius and (2) the product of number concentration times the sum of the squares of mean radius and standard deviation of the investigated particle size distributions. Besides that we find that for particles of any mode fraction of the particle size distribution the complex refractive index is uniquely defined by extinction- and backscatter-related Ångström exponents, lidar ratios at two wavelengths and effective radius.


Detlef Mueller, Alexei Kolgotin, Eduard Chemyakin, and Anton Romanov

Doc ID: 266606 Received 29 Aug 2016; Accepted 12 Sep 2016; Posted 14 Sep 2016  View: PDF

Abstract: We developed a mathematical scheme that allows us to improve retrieval products obtained from the inversion of multiwavelength Raman/HSRL lidar data, commonly dubbed “3 backscatter + 2 extinction” (3β+2α) lidar. This scheme works independently of our automated inversion method that we currently develop in the framework of the ACE (Aerosol-Cloud-Ecosystem) mission and which is successfully applied since 2012 to data collected with the first airborne multiwavelength 3β+2α HSRL, developed at NASA Langley Research Center. The mathematical scheme uses gradient correlation relationships we presented in part 1 of our study in which we investigated lidar data products and particle microphysical parameters from one and the same set of optical lidar profiles. For an accurate assessment of regression coefficients that are used in the correlation relationships we specially designed the proximate analysis method that allows us to search for a first-estimate solution space of particle microphysical parameters on the basis of a look-up table. The scheme works for any shape of particle size distribution. Simulation studies demonstrate a significant stabilization of the various solution spaces of the investigated aerosol microphysical data products if we apply this gradient correlation method in our traditional regularization technique. Surface-area concentration can be estimated with an uncertainty that is not worse than the measurement error of the underlying extinction coefficients. The retrieval uncertainty of effective radius is as large as +-0.07 mu for fine mode particles and approximately 100 % for particle size distributions composed of fine (submicron) and coarse (supermicron) mode particles. Volume concentration uncertainty is defined by the sum of the uncertainty of surface-area concentration and the uncertainty of effective radius. The uncertainty of number concentration is better than 100% for any radius domain between 0.03 and 10 mu. For monomodal PSDs the uncertainties of the real and imaginary parts of the CRI can be restricted to +-0.1 and +-0.01 on the domains [1.3; 1.8] and [0; 0.1], respectively.

Fiber-MZI based FBG sensor interrogation: Comparative study with CCD spectrometer

Bhargab Das and vikash chandra

Doc ID: 269430 Received 30 Jun 2016; Accepted 12 Sep 2016; Posted 12 Sep 2016  View: PDF

Abstract: We present an experimental comparative study of two most commonly used fiber Bragg grating (FBG) sensor interrogation techniques: CCD spectrometer and fiber Mach-Zehnder interferometer (F-MZI). Although, interferometric interrogation technique is historically known to offer the highest sensitivity measurements, however, very little information exists regarding how it compares with the current commercially available spectral characteristics based interrogation systems. It is experimentally established here that the performance of modern day CCD spectrometer interrogator is very close to F-MZI interrogator with the capability of measuring Bragg wavelength shifts with sub-picometer level accuracy. The results presented in this research study can further be used as a guideline to choose between the two FBG sensor interrogator types for small amplitude dynamic perturbation measurements down to nano-level strain.

Lower-upper-threshold correlation for underwaterrange-gated imaging self-adaptive enhancement

Liang Sun, Xinwei Wang, Liu Xiaoquan, PENGDAO REN, PINGSHUN LEI, Jun He, Songtao Fan, zhou yan, and liu yuliang

Doc ID: 273741 Received 12 Aug 2016; Accepted 12 Sep 2016; Posted 14 Sep 2016  View: PDF

Abstract: In underwater range-gated imaging (URGI), enhancement of low-brightness and low-contrast images is critical forhuman observation. Traditional histogram equalizations enhance images overly with details lost. To compressover-enhancement, a lower-upper-threshold correlation method is proposed for underwater range-gated imagingself-adaptive enhancement based on double-plateau histogram equalization. The lower threshold determinesimage details and compresses over-enhancement. It is correlated with the upper threshold. First, the upperthreshold is updated by searching local maximum in real time, and then the lower threshold is calculated by theupper threshold and the number of nonzero units selected from filtered histogram. With the method, thebackgrounds of underwater images are constrained with enhanced details. Finally, the proof experiments areperformed. PSNR, variance, contrast and human visual properties are used to evaluate the objective quality of theglobal and ROI images. The evaluation results demonstrate that the proposed method adaptively selects the properupper and lower thresholds under different conditions. The proposed method contributes to URGI with effectiveimage enhancement for human eyes.

Collection optics for a Raman spectrometer based on the 90° geometry of scattered light collection

Dmitry Petrov, Ivan Matrosov, and Danila Sedinkin

Doc ID: 270200 Received 29 Jul 2016; Accepted 11 Sep 2016; Posted 12 Sep 2016  View: PDF

Abstract: In the present work, technical solutions aimed at increasing intensities of Raman signals of gas media are considered for the 90° geometry of scattered light collection. The efficiency of classical lens, mirror-lens, and pure mirror variants of the collection optics providing solid angles of scattered light collection of 0.36, 1.84, and 1.84 sr, respectively, is investigated. It is experimentally established that, despite a smaller collection angle, for relatively narrow input slit of the spectrometer (<100 μm), the lens optics with corrected off-axis aberrations allows larger signal intensities to be register. However, the low f/# mirror collection optics described in the work can be used to increase the Raman signal intensities in cases when the image of the scattering volume formed by them is commensurable with the sizes of the input slit of the spectrometer.

Three-dimensional Displacement Measurement Based on the Combination of Digital Image Correlation and Optical Flow

Fei Xiao, Ran Zhao, and Sun Ping

Doc ID: 268657 Received 20 Jun 2016; Accepted 11 Sep 2016; Posted 12 Sep 2016  View: PDF

Abstract: A novel simultaneous three-dimensional(3D) displacement measurement technique based on combination of digital image correlation(DIC) and optical flow(OF) is proposed. In this method, both of the in-plane and out-of-plane displacements can be accurately extracted from only two continuous interferograms. The velocity field between two consecutive frames is estimated by DIC. After that, according to the optical flow constrained equation, the whole-field out-of-plane displacement map is obtained by the estimations of the in-plane displacement components and the local frequency of the original image. The operation of the proposed method is simple compared with other phase demodulation methods. Moreover, The new method works perfectly at the areas with dense fringes. In order to verify the effectiveness, the new algorithm is applied to simulated and experimental interferograms. The results of simulation and experiment show that the new method can demodulate the out-of-plane component of deformation-phase from the visible in-plane velocity field without unwrapping process. Further, the proposed algorithm provides a new approach for whole-field 3D displacement measurement and dynamic deformation measurement.

Spectral Response, Dark current, and Noise Analyses in Resonant Tunneling Quantum Dot Infrared Photodetectors

Mohammad Hossein Sheikhi, Hamed Dehdashti Jahromi, Ali Mahmoodi, and Abbas Zarifkar

Doc ID: 270716 Received 18 Jul 2016; Accepted 11 Sep 2016; Posted 14 Sep 2016  View: PDF

Abstract: Reduction of dark current at high temperature operation is a great challenge in conventional quantum dot infrared photodetectors as rate of thermal excitations resulting in the dark current increases exponentially with temperature. Resonant tunneling barriers is the best candidate for suppression of dark current, enhancement in signal-to-noise ratio and selective extraction of different wavelength response. In this paper, we use a physical model developed by authors recently to design proper resonant tunneling barrier for quantum infrared photodetectors and to study and analyze spectral response of these devices. Calculated transmission coefficient of electron by this model and its dependency on bias voltage are in agreement with experimental results. Furthermore, based on the calculated transmission coefficient the dark current of a quantum dot infrared photodetector with resonant tunneling barrier is calculated and compared with experimental data. The validity of our model is proven through this comparison. Theoretical dark current by our model shows better agreement with experimental data and is more accurate than the previously developed model. Moreover, noise in the device is calculated. Finally, effect of different parameters such as temperature, size of quantum dots, and bias voltage on the performance of the device is simulated and studied.

Suppression of FM-to-AM modulation by polarizingfiber front-end for high power lasers

Zhi Qiao, Xiaochao Wang, Wei Fan, Youen Jiang, RAO LI, Zunqi Lin, and Canhong Huang

Doc ID: 269332 Received 30 Jun 2016; Accepted 11 Sep 2016; Posted 12 Sep 2016  View: PDF

Abstract: FM-to-AM modulation is an important effect in the front-end of high power lasers that influences the temporal profile. Various methods have been implemented in standard fiber and polarization maintaining (PM) fiber front-ends to suppress the FM-to-AM modulation. To analyze the modulation in the front-end, a theoretical model is established and detailed simulations show that polarizing (PZ) fiber, whose fast axis has a large loss, can successfully suppress the modulation. Moreover the stability of the FM-to-AM modulation can be improved which is important for the front-end to obtain a stable output. To verify the model, a PZ fiber front-end is constructed experimentally. The FM-to-AM modulation without any compensation is less than 4% whereas that of the PM fiber front-end with the same structure is over 20%. The stability of the FM-to-AM modulation is analyzed experimentally and the peak-to-peak and root mean square are 2% and 0.38%, respectively, over 3 hours. The experimental results agree with the simulation results and both prove that the PZ fiber front-end can successfully suppress the FM-to-AM conversion. The PZ fiber front-end is a promising alternative for improving the performance of the front-end in high power laser facilities.

Design, simulation and quality evaluation ofmicro-optical freeform beam shapers at differentillumination conditions

Daniel Infante Gómez and Hans Peter Herzig

Doc ID: 266894 Received 24 May 2016; Accepted 10 Sep 2016; Posted 12 Sep 2016  View: PDF

Abstract: A design method to generate thin micro-optical freeform (MOF) beam shapers by clipping or wrapping an original and much thicker freeform surface is provided. MOFs are situated at the border between refractive and diffractive optical elements. The influence of parameters such as the clipping factor q, the peak-to-valley amplitude of the original surface, the design wavelength and the spectrum of the light source (single wavelength and multiple wavelength lines) into the quality of the output intensity distributions has been studied. Integer q values are mandatory for good quality at monochromatic illumination. On the contrary, the quality obtained by broadband illumination oscillates with q and peaks maximally at around q=3.

All optical noise reduction of fiber laser via intracavity SOA structure

Kang Ying, Dijun Chen, Zhengqing Pan, Xi Zhang, Haiwen Cai, and Ronghui Qu

Doc ID: 273571 Received 10 Aug 2016; Accepted 09 Sep 2016; Posted 09 Sep 2016  View: PDF

Abstract: We have designed a specially intracavity semiconductor optical amplifier (SOA) structure to suppress the relative intensity noise (RIN) for a fiber DFB laser. By exploiting the gain saturation effect of the SOA, a maximum noise suppression of 30 db around the relaxation oscillation frequency is achieved and the whole resonance relaxation oscillation peak completely disappears. Moreover, via a specially designed intracavity SOA structure, the optical intensity inside the SOA will be in a balance state via the oscillation in the laser cavity and the frequency noise of the laser will not be degraded with the SOA.

Pre-compensation of the thermal-induced refractive index changes into a Fully-Aperiodic LPF for heat load resilience

dia darwich, Romain Dauliat, Raphael Jamier, Aurélien Benoit, Kay Schuster, and Philippe Roy

Doc ID: 269065 Received 11 Jul 2016; Accepted 09 Sep 2016; Posted 12 Sep 2016  View: PDF

Abstract: In this paper, a strategy consisting in pre-compensating the thermal-induced transverse refractive index changes is undertaken to push further the appearance threshold of a multimode regime. First, a standard air-silica Large Pitch Fiber and a Fully-Aperiodic Large Pitch Fiber are confronted in regard to their heat load resilience and capabilities for singlemode emission. Thereafter, slight refractive index depressions are judiciously introduced into the active core area. This approach enhances the delocalization of the high-order modes even under severe heat load levels. This combination of aperiodic cladding microstructuration and index-pre-compensation theoretically increases the multimode regime threshold while preserving large mode field areas. This investigation is performed at 1.03 and 2µm operating wavelengths

High-spatial-resolution localization algorithm based on cascade deconvolution in a distributed Sagnac interferometer invasion monitoring system

Shaohua Pi, Bingjie Wang, Jiang Zhao, and qi sun

Doc ID: 268516 Received 17 Jun 2016; Accepted 08 Sep 2016; Posted 09 Sep 2016  View: PDF

Abstract: In the Sagnac fiber optic interferometer system, the phase difference signal can be illustrated as convolution of the waveform of invasion with its occurring-position associated transfer function h(t), deconvolution is introduced to improve the spatial resolution of the localization. In general, to get a 26 m spatial resolution at a sampling rate of 4×10^6 s-1, the algorithm should mainly go through three steps after the pre-processing operations. Firstly, transforming the decimated phase difference signal from time domain into real cepstrum domain, where a probable region of invasion distance could be ascertained. Secondly, a narrower region of invasion distance is acquired by coarsely assuming and sweeping the transfer function h(t) within the probable region and examining where the restored invasion waveform x(t) gets its minimum standard deviation. Thirdly, fine sweeping the narrow region point by point with same criteria to get the finally localization. Besides, the original waveform of invasion could be restored for the first time as a by-product, which provides more accurate and pure characteristics for further processing such as the following pattern recognition.

Non-contact measurement of liquid refractive index by using properties of the cuvette wall

Ming Xu, Junpeng Ren, RunCai Miao, and Zongquan Zhang

Doc ID: 269618 Received 01 Jul 2016; Accepted 08 Sep 2016; Posted 08 Sep 2016  View: PDF

Abstract: We present a method of non-contact measurement of the refractive index of a liquid in a glass cuvette, which uses someoptical properties of the cuvette wall and the principle of total internal reflection. By coating a transmission-scatteringpaint layer on the outer surface of the cuvette, we transform an incident laser beam into a transmitted scattered light.When the transmitted scattered light reaches the interface between the container wall and the liquid inside, the lightbeams satisfying the condition of total internal reflection are reflected to the coating layer, automatically forming acircular dark pattern that is related to the refractive index of the liquid. Based on an analytic relation between thediameter of the circular dark pattern and the refractive index of the liquid, we devised a method of in situ non-contactrefractive index measurement. We tested the effect of several parameters on the measuring accuracy and found thatthe optimal thickness of transmission-scattering layer is in the range of 50-70μm, and the aperture of diaphragm shouldbe in the range of 0.7-1.0mm. We measured the refractive indices of ethanol, Coca Cola and red wine, and achieved anaccuracy of ±3×10-4RIU(refractive index unit).

Multi-Camera System Extrinsic Stability Analysis and Large-Span Truss String Structure Displacement Measurement

Cong Liu, Shuai Dong, Mohammed Mokhtar, Xiaoyuan He, Jinyu Lu, and Xiaolong Wu

Doc ID: 269634 Received 30 Jun 2016; Accepted 07 Sep 2016; Posted 08 Sep 2016  View: PDF

Abstract: A novel technique for measuring the displacements of large-span truss string structures that employs multi-camera systems is proposed. The coordinates of the stereo-vision systems are unified in a single, global coordinate system by employing 3D data reconstructed using close-range photogrammetry. To estimate the cameras' attitude motions during an experiment, an instantaneous extrinsic rectification algorithm was developed. Experiments in which a camera was rotated and translated were conducted to verify the accuracy and precision of the developed algorithm. In addition, the proposed multi-camera systems were employed to analyze a large-span truss string structure. The displacement results obtained from numerical simulations and experiments using pre-calibration and rectification methods are compared in this paper, and the stability of the cameras' extrinsic parameters is discussed.

A proposal for a compact design for real-time opticalbistability switching via a semiconductor cavitycontaining quantum wells

Mostafa Sahrai, Solmaz Ebadollahi-Bakhtevar, and Hamed Sattari

Doc ID: 272526 Received 27 Jul 2016; Accepted 07 Sep 2016; Posted 08 Sep 2016  View: PDF

Abstract: A compact design for semiconductor cavities including coupled AlGaN/AlGaAs quantum wells is proposed for allopticalswitching of the bistability process. First, physical and geometrical parameters are optimized to engineerthe conducting electrons energy levels in the quantum wells. Then, finite element simulations based onSchrödinger equations are executed to estimate the states of the charge carriers for AlGaN/AlGaAs as the activeregion. Next, the optical coupling and pumping fields are applied to the active region to both initiate the bistabilityand facilitate its real-time control. Maxwell-Bloch approach based on rotating-wave approximation is employed toanalyze the optimal conditions for controlling the behavior of OB. It is found that the threshold of OB can beoptimized to have low values by tuning the intensity of coupling fields and the rate of an incoherent pumping field.This provides a fast real-time switching facility to control output intensity of the systems. The proposed schemecould have potential applications in optical memories, in which the paramount is to have active control overreadout of the system’s quantum states. Thanks to high nonlinear response of semiconductors, the featured devicewould be a prospective candidate for on-chip ultra-subluminal wave propagation studies and narrow-band realtimeswitching and filtering applications.

Modification of Spatial Domain Algorithms for Apertureless Light Propagation

Karl-Heinz Brenner and Soheil Mehrabkhani

Doc ID: 273329 Received 05 Aug 2016; Accepted 07 Sep 2016; Posted 08 Sep 2016  View: PDF

Abstract: Light propagation algorithms in the spatial domain hold an implicit assumption, that the calculation region represents a virtual aperture, i.e. the amplitude outside of the calculation region is zero. With typically bright objects on a dark background, this assumption is legitimate and the calculation is correct. With dark objects on a bright background, however, the assumption is violated and the calculation result is dominated by diffraction effects at a virtual aperture. This virtual aperture diffraction is especially a problem for pure phase elements, because the amplitude in and beyond the calculation region is constant one. In this paper, we explain the background of the problem and present a general and effective method to remove this problem.


Amin Al-Habaibeh, Maryam Asrar, and Mohammed Houda

Doc ID: 269478 Received 30 Jun 2016; Accepted 07 Sep 2016; Posted 08 Sep 2016  View: PDF

Abstract: Intravenous cannulation is the process of inserting a cannula into a vein to administrate medication, fluids or to take blood samples. The process of identification and locating of veins plays an important role during the intravenous cannulation procedure to reduce health care costs and suffering of patients. This paper compares between the three technologies to assess their suitability and capability for the detection of veins to support the cannulation process. Three types of cameras are used in this study, a visual, an infrared and a near infrared. The collected images from the three technologies have been analysed using a wide range of image processing techniques and compared with identification templates to evaluate the performance of each technology. The results show that the near infrared technology supported by suitable LED illumination is the most effective for the visualisation of veins. However, infrared thermography is found to be successful when followed by a cold stimulation.

Development of one-shot aspheric measurement system with Shack-Hartmann sensor

Yasunori Furukawa, YUICHI TAKAIE, YOSHIKI MAEDA, YUMIKO OHSAKI, Seiji Takeuchi, and Masanobu Hasegawa

Doc ID: 268406 Received 29 Jun 2016; Accepted 07 Sep 2016; Posted 08 Sep 2016  View: PDF

Abstract: We present a measurement system for a rotationally symmetric aspheric surface that is designed for accurate and high volume measurement. The system uses the Shack-Hartmann sensor and is capable of measuring aspheres with a maximum diameter of 90 mm in one-shot. In our system, a reference surface, made with the same aspheric parameter as the test surface is prepared. The test surface is recovered as the deviation from the reference surface using a figure-error reconstruction algorithm with a ray coordinate and angle transformation table. In addition, we developed a method to calibrate the rotationally symmetric system error. These techniques produce stable measurements and high accuracy. For high-throughput measurement, a single measurement scheme and auto-alignment are implemented, which produced a 4.5 minute measurement time including calibration and alignment. In this paper, we introduce the principle and calibration method of our system. We also demonstrate that our system achieved an accuracy better than 5.8 nm RMS and a repeatability of 0.75 nm RMS by comparing our system’s aspheric measurement results with those of a probe measurement machine.

A two-stage automated measurement process for high-resolution 3D digitization of unknown objects

Maciej Karaszewski, Michał Stępień, and Robert Sitnik

Doc ID: 268633 Received 20 Jun 2016; Accepted 07 Sep 2016; Posted 08 Sep 2016  View: PDF

Abstract: In this paper, a process for high-resolution, automated 3D digitization of unknown objects (i.e., without any digital model) is presented. The process has two stages—the first leads to a coarse 3D digital model of the object, and the second obtains the final model. A rough model, acquired by a 3D measurement head with a large working volume and relatively low resolution, is used to calculate the precise head positions required for the full digitization of the object, as well as collision detection and avoidance. We show that this approach is much more efficient than digitization with only a precise head, when its positions for subsequent measurements (so called next-best-views) must be calculated based only on a partially recovered 3D model of the object. We also show how using a rough object representation for collision detection shortens the high-resolution digitization process.

An improved transmission method for measuring the optical extinction coefficient of micro/nano particle suspensions

Lin Hua Liu, Xingcan Li, Junming Zhao, and Wang Chengchao

Doc ID: 268792 Received 20 Jun 2016; Accepted 07 Sep 2016; Posted 08 Sep 2016  View: PDF

Abstract: Extinction coefficientis fundamental to analyze radiative transport in micro/nanoparticle suspensions. In the traditional transmission methodformeasuring the extinction coefficient of particles in a cuvette, areference systemis used tocompensate the influence of the cuvetteand base fluid. However, the multiple reflections and refractions between the air/glass and liquid/glass interfaces in the cuvette cannot be totally eliminatedby using the reference system, and the inducedmeasurement error increases significantlywithincreasingdifferencein refractive index between twoneighboring mediaat these interfaces. In this paper,an improved transmission method is proposed to measure the extinction coefficient of micro/nano particles. The optical constants of the glass and the liquid are determined first as input. Then the extinction coefficient of the particles is determined based on an optical model taking into account the multiple reflection and refraction at the glass/liquid interfaces. An experimental validation ontheimproved transmission method was conducted for suspensionswith various mean particle sizes. In the traditional transmission method,neglectinghigher-order transmission terms caused by multiple reflections at medium interfaces in the optical model introduces additional errors. By considering the higher-order transmission terms,the improvedtransmission method generally achieved high accuracy improvement over the traditional transmission method for extinction coefficient measurement , especially for the case with small optical thickness of particlesuspensions. This provides an alternative and more accurate way for measuring the extinction characteristics of micro/nano particle suspensions.

Refraction index sensor based on phase resonances in a subwavelength structure with double period

Diana Skigin and Marcelo Lester

Doc ID: 269093 Received 24 Jun 2016; Accepted 06 Sep 2016; Posted 08 Sep 2016  View: PDF

Abstract: In this paper we numerically demonstrate a refraction index sensor based on phase resonance excitation in a subwavelength-slit structure with double period. The sensor consists of a metal layer with subwavelength slots arranged in a bi-periodic form, separated from a high refraction index medium. Between the metallic structureand the incident medium, a dielectric waveguide is formed, whose refraction index is going to be determined.Variations in the refraction index of the waveguide are detected as shifts in the peaks of transmitted intensity originated by resonant modes supported by the compound metallic structure. At normal incidence, the spectral position of these resonant peaks exhibits a linear or a quadratic dependence with the refraction index, which permits to obtain the unknown refraction index value with a high precision for a wide range of wavelengths. Since the operating principle of the sensor is due to morphological resonances of the slits' structure, this device can be scaled to operate in different wavelength ranges while keeping similar characteristics.

Exact recovery of wavefront from multi-shearing interferograms in spatial domian

Dede Zhai, Shanyong chen, Shuai Xue, and Ziqiang Yin

Doc ID: 270171 Received 11 Jul 2016; Accepted 06 Sep 2016; Posted 08 Sep 2016  View: PDF

Abstract: An exact algorithm based on the multi-shearing interferograms has been proposed to reconstruct a two-dimensional wavefront in spatial domain. It allows large shears and high resolution of the reconstructed wavefront to be achieved. A simple model is proposed to explain the requirement of shear amounts to reconstruct two-dimensional exactly. In this paper we use simultaneous linear equations to express the relationship between difference wavefronts and the unknown original wavefront, and then the least-squares method is applied to reconstruct the wavefront which is simple for implementation and robust to noise. To solve the memory problem, an improved wavefront reconstruction algorithm based on virtual sub-aperture stitching was proposed to improve the calculation efficiency. Lastly, Numerical simulations are implemented and the proposed algorithm is compared with another modal and zonal method. In the point-to-point mapping based fitting reconstruction algorithm, no any assumption and prerequisite about the original wave front is necessary. The results indicate that the proposed algorithm is capable of reconstructing continuous or discontinuous wavefront exactly with large grid. Numerical simulation also shows high accuracy recovery capability of the proposed method in the existence of mixed noise.

Development of a fast and accurate PCRTM radiative transfer model in solar spectral region

Xu Liu, Qiguang Yang, Hui Li, Zhonghai Jin, Wan Wu, Susan Kizer, Daniel Zhou, and Ping Yang

Doc ID: 268547 Received 16 Jun 2016; Accepted 06 Sep 2016; Posted 09 Sep 2016  View: PDF

Abstract: A fast and accurate principal component based radiative transfer model in solar spectral region (PCRTM-SOLAR) has beendeveloped. The algorithm is capable of simulating reflected solar (RS) spectra in both clear sky and cloudy atmosphericconditions. Multiple scattering of the solar beam by the multi-layer clouds and aerosols are calculated using a discrete ordinateradiative transfer (DISORT) scheme. The PCRTM-SOLAR model can be trained to simulate top-of-atmosphere (TOA) radiance orreflectance spectra with spectral resolution ranging from 1 cm-1 resolution to a few nanometers. Broadband radiances orreflectance can also be calculated if desired. The current version of the PCRTM-SOLAR covers spectral range from 300 nm to2500 nm. The model is valid for solar zenith angles (SZA) ranging from 0 to 80 degree, the instrument view zenith angles (VZA)ranging from 0 to 70 degree, and the relative azimuthal angles (RAA) ranging from 0 to 360 degree. Depending on the numberof spectral channels, the speed of current version of PCRTM-SOLAR is few-hundred to over one thousand times faster than themedium speed correlated-k option (MODTRAN5). The absolute RMS error in channel radiance is smaller than 10-3mW/cm2/sr/cm-1 and the relative error is typically less than 0.2 percent.

Optical performance improvement of phosphor-in-glass based white light-emitting diodes through optimized packaging structure

Mingxiang Chen, Yang Peng, Ruixin Li, Xing Guo, and Huai Zheng

Doc ID: 272528 Received 27 Jul 2016; Accepted 06 Sep 2016; Posted 09 Sep 2016  View: PDF

Abstract: To improve the optical performance of multi-components phosphor-in-glass (PiG) based white light-emittingdiodes (WLEDs), we proposed an optimized packaging structure, which is a combined structure of patterned PiGwith crater-type lens. The patterned PiG yields a red phosphor circle surrounded by a yellow phosphor concentricring. The comparison simulations and experiments between the conventional mixed structure, patternedstructure, and proposed structure were conducted. Compared with the mixed structure and patterned structure,the luminous efficacy of proposed structure is increased by 19.3% and 10.7% at the driving current of 350 mA,respectively. Furthermore, the deviation of correlated color temperature (CCT) of the patterned PiG is reducedfrom 906 K to 129 K by the crater-type lens at the average CCT of 4100 K. The results demonstrate that theproposed packaging structure can improve the luminous efficacy and angular color uniformity (ACU) of PiG-basedWLED simultaneously..

Ion beam figuring approach for thermally sensitivespace optics

Yin Xiaolin, Weijie Deng, Wa Tang, zhang binzhi, Xue Donglin, Feng Zhang, and Xue-Jun Zhang

Doc ID: 272676 Received 28 Jul 2016; Accepted 05 Sep 2016; Posted 07 Sep 2016  View: PDF

Abstract: During the ion beam figuring (IBF) of a space mirror, the mirror will be heated by thermal radiation of the neutralfilament and particle collisions. The adhesive layer used to bond the metal parts and the mirror is very sensitive totemperature rise. When the temperature exceeds the designed value, the mirror surface shape will change markedlybecause of the thermal deformation and stress release of the adhesive layer, thereby reducing the accuracy of IBF. Tosuppress the thermal effect, we analyzed the heat generation mechanism. By using thermal radiation theory, weestablished a thermal radiation model of the neutral filament. Additionally, we acquired a surface-type Gaussian heatsource model of the ion beam sputtering based on the removal function and Faraday scan result. Using the finiteelement-method software ABAQUS, we developed a method that can simulate the thermal effect of the IBF for the fullpath and all dwell times. Based on the thermal model, which was experimentally confirmed, we simulated the thermaleffects for a 675 mm × 374 mm rectangular SiC space mirror. By optimizing the dwell time distribution, the peaktemperature value of the adhesive layer during the figuring process was reduced under the designed value. After oneround of figuring, the RMS value of the surface error changed from 0.094 λ to 0.015 λ (λ = 632.8 nm), which proved theeffectiveness of the thermal analysis and suppression method.

Diffraction analysis for DMD-based scene projectors in the long-wave infrared

Qing Han, Jianzhong Zhang, Qiang Sun, and Jian Wang

Doc ID: 269904 Received 12 Jul 2016; Accepted 05 Sep 2016; Posted 07 Sep 2016  View: PDF

Abstract: Diffraction effects play a significant role in the digital micromirror devices (DMD)-based scene projectors in the long-wave infrared (IR) band (8µm to 12µm). The contrast provided by these projector systems can become noticeably worse because of the diffraction characteristics of the DMD. We apply a diffraction grating model of the DMD based on scalar diffraction theory and Fourier transform to address this issue. In addition, simulation calculation is conducted with MATLAB. Finally, the simulation result is verified with experiment. Simulation and experimental results indicate that, when the incident azimuth angle is 0° and the zenith angle is between 42°and 46°, the scene projectors will have a good imaging contrast in the long-wave IR. The diffraction grating model proposed in this study provides a method to improve the contrast of DMD-based scene projectors in the long-wave IR.

Non-index-matching measurement of the refractive index distribution of a molded lens by two-color wavefronts

Tomohiro Sugimoto

Doc ID: 269943 Received 07 Jul 2016; Accepted 05 Sep 2016; Posted 07 Sep 2016  View: PDF

Abstract: This paper presents a nondestructive and non-index-matching method for measuring the refractive index distribution of a molded lens with high refractivity. The method measures two-color wavefronts of a test lens immersed in a liquid with a refractive index dispersion different from that of the test lens and calculates the refractive index distribution by eliminating the refractive index distribution error caused by the shape error of the test lens. The estimated uncertainties of the refractive index distributions of test lenses with nd = 1.77 and nd = 1.85 were 1.9x10^(-5) RMS and 2.4x10^(-5) RMS respectively. I validated the proposed method by evaluating the agreement between the estimated uncertainties and experimental values.

An efficient compressed imaging method for micro satellite optical camera

li jin and Zilong Liu

Doc ID: 270129 Received 08 Jul 2016; Accepted 05 Sep 2016; Posted 07 Sep 2016  View: PDF

Abstract: Imaging integrated with compression is considered the holy-grail of micro-satellite photography because it improves the degree of integration of camera system, removing compression system, high capacity storage system and high-speed image transmission system which consume lots of resources of satellite platform. In this paper, we propose an efficient compressed imaging method for remote sensing photography. We consider wavelet coefficients as pixels of block wise Mega-Pixel sensor (BMPS). We integrate the saliency information stage into BMPS to perform compressed sampling (CS) in order to further improve imaging performance. In compressed sensing process, we use transformed post-wavelet coefficients to calculate saliency information of images in post-wavelet domain. According to different region having different saliency information, the corresponding sensing resources are allocated to perform CS. CS can obtain the compressed discrete sparse samples of the original signal at the much lower sample rate than Nyquist frequency. The discrete samples signal can be reconstructed by non-linear recovery algorithm in the ground. Experimental results show that the proposed compressed imaging method outperforms the traditional saliency-based methods in terms of multiple assessment approaches.

Mode-locked all-fiber dumbbell-shaped laser based on nonlinear amplifying optical loop mirror

Sheng-Ping Chen, Bing-Ke Yang, He Chen, xue qi, and jing hou

Doc ID: 270568 Received 14 Jul 2016; Accepted 05 Sep 2016; Posted 07 Sep 2016  View: PDF

Abstract: We report on a new design for a passively mode-locked dumbbell-shaped fiber laser employing all normal dispersion fibers at 1 μm based on a nonlinear optical loop mirror (NOLM) and a nonlinear amplifying optical fiber-loop mirror (NALM). The laser produced noise-like pulses of 16.2 nJ and 26.4 nJ from the two output ports respectively, at a repetition rate of 8.85 MHz. Several interesting phenomena are observed and briefly discussed in the paper.

Analysis of the convergence rules of full range PSD surface error of magnetorheological figuring KDP crystal

Chen Shaoshan, Deyu He, Yi Wu, Zaijing Zhang, Yunlei Chen, and Huangfei Chen

Doc ID: 263438 Received 02 May 2016; Accepted 05 Sep 2016; Posted 07 Sep 2016  View: PDF

Abstract: A new non-aqueous and abrasive-free magnetorheological finishing (MRF) method is adopted for processing potassium dihydrogen phosphate(KDP) crystal due to its low hardness, high brittleness, temperature sensitivity, and water solubility. This paper researches the convergence rules of surface error of an initial single-point diamond turning (SPDT)-finished KDP crystal after MRF polishing. Currently SPDT process contains spiral cutting and fly cutting. The main difference of these two processes lies in the morphology of intermediate-frequency turning marks on the surface which affects the convergence rules. The turning marks after spiral cutting are a series of concentric circles. While, the turning marks after flying cutting are a series of parallel big arc. Polishing results indicate MRF polishing can only improve the low frequency error (L<10mm) of a spiral cutting KDP crystal. MRF polishing can improve the full range surface error (L>0.01mm) of a flying cutting KDP crystal if the polishing process is not more than two times for single surface. We can conclude a flying cutting KDP crystal will meet better optical performance after MRF figuring than a spiral cutting KDP crystal with similar initial surface performance.

The basic geometry and aberration characteristics of conicoidal conformal domes

Dang Yang, WANG ZHANG, chen Shouqian, HUI WANG, Jiaqian Yu, Fan Zhigang, and Le Nhu

Doc ID: 268252 Received 16 Jun 2016; Accepted 05 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: This paper investigated the geometry and aberration characteristics of conicoidal conformal domes. Firstly, on thebasis of previous research, we got the expression which was suitable for describing the external surface of theconicoidal conformal dome. Based on the theory of differential geometry, this paper firstly proved that the Dupinindex line of a quadric surface was an ellipsoid and the radius of curvature had extreme values in the meridianplane and sagittal plane. Then the uniform formulas of curvature which were suitable for ellipsoid, paraboloid andhyperboloid were deduced in the meridian plane and sagittal plane respectively. Meanwhile, the angle between theaxis of imaging systems and the surface normal was calculated. With the help of computers, the plots of curvaturedifferences and the angle in the case of different edge slopes, fineness ratios and the locations of the rotationalcenter were obtained. Finally, we analyzed the Zernike polynomial coefficients of Z4, Z5 and Z8 which representdefocus, astigmatism and coma respectively for the model established in CODE V. The research indicates thedynamic ranges of defocus, astigmatism and coma increase with the growing of edge slopes and fineness ratios, buthave little change with the variation of the rotational center positions. Moreover, the curves of Z5 and Z8 haveturning points, and the curves of curvature differences and angle difference only similar to the curves of Z5 and Z8when the look angle changes after the turning point. For the look angle changing from zero to the turning point, thecurves of Z5 and Z8 change rapidly. This is mainly caused by the significant variations of the symmetry of theconformal dome participating in imaging. Therefore, the aberrations with small scanning angles should be takenmore attention when designing the conformal systems.

Optical image encryption based on joint Fresnel transform correlator with double optical wedges

xue shen, Shuaifeng Dou, Ming Lei, and Yudan Chen

Doc ID: 268532 Received 21 Jun 2016; Accepted 04 Sep 2016; Posted 23 Sep 2016  View: PDF

Abstract: An optical cryptosystem based on the joint Fresnel transform correlator (JFTC) with double optical wedges is designed. The designed cryptosystem retains the two major advantages of JTC based optical cryptosystem. First, the encrypted image is real-valued and therefore is easier to record and transmit. Second, the encryption process is simplified since it doesn’t require accurate alignment of optical elements or the generation of the complex conjugate of the key. On top of that, the designed optical cryptosystem can produce decrypted image with higher quality than JTC based optical cryptosystem, because the original encrypted image is divided by Fresnel transform power distribution of key mask to generate the new encrypted image, which significantly reduces the noises during the decryption process. Simulation results showed that the correlation coefficient of the decrypted image and the original image can reach as large as 0.9819 after denoising and adequately selecting half central interval a and encrypted image width w. Another improvement relative to JTC based optical cryptosystem is that the attack resistibility gets enhanced due to the nonlinearity of the encryption process as well as the additional key parameter a which enlarged the key space.

Sensitivity, Stability, and Precision of Quantitative Ns-LIBS-Based Fuel-Air Ratio Measurements for Methane-Air Flames at 1–11 bar

Paul Hsu, Mark GRAGSTON, YUE WU, zhili zhang, Anil Patnaik, Johannes Kiefer, Sukesh Roy, and James Gord

Doc ID: 270744 Received 18 Jul 2016; Accepted 03 Sep 2016; Posted 07 Sep 2016  View: PDF

Abstract: Nanosecond-laser–based laser-induced breakdown spectroscopy (ns-LIBS) is employed for quantitative local fuel-air (F/A) ratio (i.e., ratio of actual fuel-to-oxidizer mass over ratio of fuel-to-oxidizer mass at stoichiometry) measurements in well-characterized methane-air flames at pressures of 1 – 11 bar. Nitrogen and hydrogen atomic-emission lines at 568 nm and 656 nm, respectively, are selected to establish a correlation between the line intensities and the F/A ratio. The effects of laser-pulse energy, camera gate delay, and pressure on the sensitivity, stability, and precision of the quantitative ns-LIBS F/A ratio measurements are investigated. The optimal laser energy and camera gate delay are determined for each pressure condition. It is found that measurement stability and precision are degraded with an increase in pressure. Primary limitations of the F/A ratio measurement employing ns-LIBS at elevated pressures are identified as instabilities caused by the laser-induced dense plasma and the presence of high-level soot. Potential improvements are suggested.

Implementation of a flexible laser beam shapingtechnique for generation of 100mJ-level picosecondpulses

Kirilas Michailovas, Jonas Adamonis, Aidas Aleknavičius, Stanislovas Balickas, Virginija Petrauskiene, Titas Gertus, and Andrejus Michailovas

Doc ID: 269694 Received 01 Jul 2016; Accepted 02 Sep 2016; Posted 07 Sep 2016  View: PDF

Abstract: We present implementation of the energy efficient and flexible laser beam shaping technique in a high-power andhigh-energy laser amplifier system. The beam shaping is based on a spatially variable wave plate (SVWP) fabricatedby femtosecond laser nanostructuring of glass. We reshaped the initially Gaussian beam into a super-Gaussian of the12th order with efficiency of about 50%. The 12th order of the SG beam provided the best compromise between largefill factor, low diffraction on the edges of the active media, and moderate intensity distribution modification duringfree-space propagation. 150mJ pulses of 532nm radiation were obtained. High energy, pulse duration of 85ps andthe nearly flat-top spatial profile of the beam make it ideal for pumping OPCPA systems.

Multi-scale Target Extraction Using Spectral Saliency Map for Hyperspectral Image

JING ZHANG, Wenhao Geng, Li Zhuo, Qi Tian, and Yan Cao

Doc ID: 267824 Received 16 Jun 2016; Accepted 02 Sep 2016; Posted 07 Sep 2016  View: PDF

Abstract: With the rapidly growth of the capabilities for hyperspectral imagery acquisition, how to efficiently find the significant target in hyperspectral imagery has become a fundamental task for remote-sensing applications. Existing target extraction methods mainly separate targets from background with threshold based on pixels and single-scale image information extraction. However, due to the high dimensional characteristics and the complex background of hyperspectral image, it is difficult to obtain good extraction results with existing methods. Saliency detection has been a promising topic because saliency feature can quickly locate saliency regions from complex background. Considering the spatial and spectral characteristics of hyperspectral image, a multi-scale target extraction method using spectral saliency map is proposed for hyperspectral image, which includes: (1) spectral saliency model is constructed for detecting spectral saliency map in hyperspectral image; (2) Focus Of Attention (FOA) as the seed point is competed in the spectral saliency map by the Winner-Take-All (WTA) network; (3) the multi-scale image is segmented by region growing based on minimum-heterogeneity rule after calculating the heterogeneity of seed point with its surrounding pixels; (4) the salient target is detected and segmented under the constraint of spectral saliency map. The experimental results show that proposed method can effectively improve the accuracy of target extraction for hyperspectral image.

Design and optimization of seed pulse generationscheme for precise beam synchronization in theXingguang-III laser

Song Zhou, Xiaoming zeng, Kainan Zhou, huang xiaojun, Xiaodong Wang, xiao wang, Na Xie, dongbin Jiang, Wu Zhaohui, Lei Zhao, Jing Wen, Ying Zhang, Zheng Huang, Li Sun, Yi Guo, Qing li, Qihua Zhu, Jingqin Su, and Feng Jing

Doc ID: 269311 Received 08 Jul 2016; Accepted 02 Sep 2016; Posted 06 Sep 2016  View: PDF

Abstract: Xingguang-III is a large hybrid OPA + CPA laser that outputs synchronized femtosecond, picosecond and nanosecond beams with three different wavelengths, i.e. 800 nm, 1053 nm and 527 nm respectively. We present here an in-house front-end system design based on white-light continuum generation and femtosecond parametric amplification, generating the 1053 nm seed laser for the ps/ns beam directly from the 800 nm femtosecond laser, which enables the three beams to have intrinsic synchronization. The results show that a 1053 nm/20 μJ/8.4 ns seed pulse is generated and the shot-to-shot timing jitter (peak-to-valley) between the fs and the ps beam is less than 1.32 ps.

Continuous and discrete diffractive elements with polar symmetries

Jürgen Jahns

Doc ID: 272993 Received 01 Aug 2016; Accepted 01 Sep 2016; Posted 07 Sep 2016  View: PDF

Abstract: Diffractive elements are considered with polar symmetry, i.e., where the transmission function dependson the radial and/or the azimuthal coordinate. Well-known examples are the axicon, the Fresnel zoneplate, and the Siemens star. Here, we are interested, in particular, in elements, where both coordinates arecoupled, as in the case of the spiral axicon. The spiral axicon is known for generating a wave field with anorbital angular momentum. Here, we consider the variety of elements that can be generated. In particular,we analyze the performance of the element for the case, where the continuous structure is broken up anddiscretized. This leads to the generation of off-axis intensity zeroes and vortices. For this conceptualstudy, scalar diffraction theory is used for the analysis and numerical simulations were used to calculateexamples of generated light distributions.

Ruling of echelles and gratings with diamond tool by torque equilibrium method

Jiri Jirigalantu, xiaotian li, Shanwen Zhang, xiaotao mi, JianXiang Gao, heshig bayan, Xiangdong Qi, and Yuguo Tang

Doc ID: 268912 Received 24 Jun 2016; Accepted 31 Aug 2016; Posted 07 Sep 2016  View: PDF

Abstract: Ruling of echelles and gratings by the torque equilibrium method is proposed to eliminate corrugated grating lines, rough blazed grating surfaces and complex fabrication work such as step-by-step diamond tool deflection. A mathematical model of the torque equilibrium between the diamond tool and the metallic film during the ruling process is deduced to realize optimized diamond tool geometrical parameter design. Then, two echelles with identical areas of 80×100 mm2 are separately ruled using the traditional deflecting tool ruling method and the proposed method, and the scatter lightscatter light results for the two echelles are 9.6×10-4 and 3.1×10−4, respectively.

Affordable Dispersion Mitigation with an AnalogElectrical Filter

Er'el Granot, shalom bloch, and Shmuel Sternklar

Doc ID: 272060 Received 22 Jul 2016; Accepted 31 Aug 2016; Posted 01 Sep 2016  View: PDF

Abstract: A new method for dispersion mitigation is presented for low-cost and simple networks. Themethod does not require dispersion compensating fibers, special optical filters, coherent detection,or external modulation. It can work in a direct modulation scheme and with a standard opticaldetector. The disadvantage of this method is the requirement to operate in the weak modulationregime of the signal. In this regime, the dispersive channel can be regarded as linear in the powerdomain, and not only in the field domain, so that the effects of dispersion can be reduced with aproper electronic filter. Since electronic filters are usually considerably cheaper than coherentoptical solutions, this solution can be implemented in low cost networks, where dispersion is amore severe problem than noise. We show that by adding the filter to a low-noise OOK system it ispossible to transmit data at bit rates of 50Gb/s to distances at least six-fold larger than its OOKlimit (6km in this case), i.e., 40km and beyond.

Simple calculation of computer-generated hologram for lensless holographic 3D projection using nonuniform sampled wavefront recording plane

Shouping Nie, Chenliang Chang, Jun Wu, Yijun Qi, Caojin Yuan, and Jun Xia

Doc ID: 272147 Received 22 Jul 2016; Accepted 31 Aug 2016; Posted 01 Sep 2016  View: PDF

Abstract: In this paper we present a method for calculation of computer-generated hologram (CGH) from 3D object. A virtual wavefront recording plane (WRP) which is close to the 3D object is established. This WRP is nonuniformly sampled according to the depth map of the 3D object. The generation of CGH only involves two nonuniform fast Fourier transform (NUFFT) and two fast Fourier transform (FFT) operations, the whole computational procedure is greatly simplified by diffraction calculation from 2D planar image instead of 3D object voxels. Numerical simulations and optical experiments are carried out to confirm the feasibility of our proposed method. The CGH calculated with our method is capable to project zoomable 3D objects without lens.

A simplified weighting function for high dynamic range video frame formation

David Griffiths and Alfred Wicks

Doc ID: 267343 Received 01 Jun 2016; Accepted 30 Aug 2016; Posted 31 Aug 2016  View: PDF

Abstract: High dynamic range imagery has matured from a laboratory demonstration to an integrated capability in consumer level cameras. However, high dynamic range video has lagged in development despite the introduction of several different frame formation methodologies and system architectures. The most common formation methodology involves the calculation of a high dynamic range image from a series of rapidly bracketed frames at varying exposure levels, then through the use of a radiometric calibration, recombined utilizing a weighted maximum likelihood estimator. The ideal weighting scheme to minimize the error on final image formation has been investigated by several authors. A new non-recursive, simplified weighting scheme is proposed that utilized only knowledge of the optical attenuation, integration time and sensor gain. A method is developed to test the various weighting schemes for their resilience to error with limited available exposures over a wide range of exposure value offsets, a common scenario for multi imager based high dynamic range video systems.

Strong electric field enhancements in asymmetric metallic nanostructures and High-Order Harmonic Generation

Masoud Mohebbi and hassan ebadian

Doc ID: 267980 Received 09 Jun 2016; Accepted 30 Aug 2016; Posted 31 Aug 2016  View: PDF

Abstract: Numerical investigation of high order harmonic generation (HHG) is carried out in noble gases near metal nano-dimers. The effect of geometry, shape and gap of dimers in the plasmon resonance and local electric field enhancement has been investigated numerically by using FDTD methods. It is shown that lack of symmetry in dimer shapes plays an important role in the HHG process producing appreciable modifications to the energy-resolved photoelectron spectra.

Active thermography inspection of the contamination of the protective glass on laser scanning heads

Jiri Skala, Michal Svantner, Jiri Tesar, and Aleš Franc

Doc ID: 269635 Received 30 Jun 2016; Accepted 30 Aug 2016; Posted 30 Aug 2016  View: PDF

Abstract: Industrial lasers are an expanding technology of welding and other material processing. Lasers are often used withoptical scanning heads which provide more versatility, accuracy and speed. The output part of the scanning head is covered bya protective glass which might get contaminated by various particles from the laser processing. This decreases the transmissivity ofthe glass and it can affect the production quality. The contamination needs to be checked regularly but a visual inspection might notalways be effective. This paper proposes two alternative methods of inspecting the protective glass – flash-pulse activethermography and laser active thermography. They are based on the thermal excitation of the glass and measuring the responsewith an infrared camera. The experimental setup and practical results are described and the advantages and disadvantages arediscussed. The presented methods proved to be effective in detecting the contamination of the glass.

Simultaneous interferometric measurement of linear coefficient of thermal expansion and temperature-dependent refractive index coefficient of optical materials

James Corsetti, William Green, Jonathan Ellis, Greg Schmidt, and Duncan Moore

Doc ID: 270170 Received 11 Jul 2016; Accepted 29 Aug 2016; Posted 30 Aug 2016  View: PDF

Abstract: Characterizing the thermal properties of optical materials is necessary for understanding how to design an optical system for changing environmental conditions. A method is presented for simultaneously measuring both the linear coefficient of thermal expansion and the temperature-dependent refractive index coefficient of a sample interferometrically in air. Both the design and fabrication of the interferometer is presented as well as a discussion of the results of measuring both a steel and a CaF2 sample.

A New Approach To Inverting Backscatter and Scatter from Photon-Limited Lidar Observations

Willem Marais, Robert Holz, Yu Hen Hu, Ralph Kuehn, Edwin Eloranta, and Rebecca Willett

Doc ID: 259412 Received 16 Feb 2016; Accepted 29 Aug 2016; Posted 29 Aug 2016  View: PDF

Abstract: Atmospheric lidar observations provide a unique capability to directly observe the vertical column of cloud and aerosol scattering properties. However, detector and solar background noise hinder the ability of lidar systems to provide reliable backscatter and extinction (scatter) estimates. Standard methods for solving this inverse problem are only effective with high signal-to-noise ratio observations that are only available at low-resolution in uniform scenes. This paper describes a novel method for solving the inverse problem with high-resolution, lower signal-to-noise ratio observations that are effective in non-uniform scenes. Specifically, the noise associated with photon-counting lidar observations can be modeled using a Poisson distribution, and state-of-the-art tools for solving Poisson inverse problems are adapted to the atmospheric lidar problem. It is demonstrated through photon-counting HSRL (High Spectral Resolution Lidar) simulations that the proposed algorithm yield inverted backscatter and scatter cross-sections (per unit volume) with smaller MSE (Mean Squared Error) values at higher spatial resolutions, compared to the standard approach. A limited case study of real experimental data is also provided where the proposed algorithm is applied on HSRL observations and the inverted optical depths are compared against those of AERONET. In addition, three case studies on real data are also provided to juxtapose the inversion results of the new and the standard approaches.

Retrieval of the particle size distribution function from the data of lidar sensing under the assumption of known refractive index

Iogannes Penner, Svetlana Samoilova, and Michael Sviridenkov

Doc ID: 267443 Received 02 Jun 2016; Accepted 29 Aug 2016; Posted 30 Aug 2016  View: PDF

Abstract: We suggest a method for retrieval of the particle size distribution function from the data of vertical lidar sensing. We have used the data obtained at the Zvenigorod AERONET site obtained in 2011–2012, 462 models altogether. For each laser shot both fine (with particle sizes in the range from 0.05 to 0.6 um) and coarse aerosol fractions (from 0.6 to 10 um) were considered, with emphasize on the coarse fraction. The suggested method is the improvement of the Tikhonov method. The Tikhonov method is not optimal for coarse particles, because its stabilizer does not account for and cannot account for the presence of the coarse mode (in fact, the data on the presence of several extrema of the particle size distribution function). The components of the matrix located in quadrants II and IV are sensitive to the change of these parameters. The neglect of this fact will lead again to arbitrariness of estimating the contribution of the coarse particles even for exact values on the main diagonal and two diagonals adjacent to it. The suggested method allows the coarse fraction up to 2.5 um to be determined unambiguously. For larger particles (> 2.5 um) it is recommended to use the available sets of the coefficients, but with level of values to be determined.

Atmospheric Propagation and Combining of High-Power Lasers: Response to Comments.

William Nelson, Phillip Sprangle, and Christopher Davis

Doc ID: 270071 Received 06 Jul 2016; Accepted 28 Aug 2016; Posted 29 Aug 2016  View: PDF

Abstract: Response to comments.

Overview of Advanced LIGO Adaptive Optics

Aidan Brooks, Benjamin Abbott, Muzammil Arain, Giacomo Ciani, Ayodele Cole, Greg Grabeel, Eric Gustafson, Christopher Guido, Matthew Heintze, Alastair Heptonstall, Mindy Jacobson, Won Kim, Eleanor King, Alexander Lynch, Stephen O'Connor, David Ottaway, Ken Mailand, Guido Mueller, Jesper Munch, Virginio Sannibale, Zhenhua Shao, Michael Smith, Peter Veitch, Thomas Vo, Cheryl Vorvick, and Phil Willems

Doc ID: 269484 Received 07 Jul 2016; Accepted 26 Aug 2016; Posted 26 Aug 2016  View: PDF

Abstract: This is an overview of the adaptive optics used in Advanced LIGO (aLIGO), known as the thermal compensation system (TCS). The thermal compensation system was designed to minimize thermally-induced spatial distortions in the interferometer optical modes and to provide some correction for static curvature errors in the core optics of aLIGO. The TCS is comprised of ring heater actuators, spatially tunable CO2 laser projectors and Hartmann wavefront sensors. The system meets the requirements of correcting for nominal distortion in Advanced LIGO to a maximum residual error of 5.4nm, weighted across the laser beam, for up to 125W of laser input power into the interferometer.

Accurate feature detection for out-of-focus cameracalibration

Yuwei Wang, Wang Wang, xiangcheng chen, Jiayuan Tao, and Mengchao Ma

Doc ID: 269221 Received 24 Jun 2016; Accepted 25 Aug 2016; Posted 02 Sep 2016  View: PDF

Abstract: For conventional camera calibration methods, well-focused images are necessary to detect features accurately. However, thisrequirement causes practical inconveniences to image acquisition through long- and short-distance photogrammetry. In thisstudy, three active phase-shift circular grating (PCG) arrays are used as calibration patterns. The PCGs’ centers are regarded asfeature points that can be accurately extracted by ellipse fitting of 2π-phase points even though patterns are substantiallyblurred. In the experiments, Gaussian filters are utilized to blur pattern images, and different standard deviations are set fordifferent fuzzy degrees. Pattern images with different defocusing degrees are also captured. The period and number of PCGsand noise are considered. Experimental results indicate that our method is accurate, reliable, and insensitive to imagedefocusing.

Methane detection using scattering material as the gas cell

Hongze Lin, Chunsheng Yan, Fei Gao, Yujian Ding, and Sailing He

Doc ID: 268433 Received 16 Jun 2016; Accepted 22 Aug 2016; Posted 23 Aug 2016  View: PDF

Abstract: A compact methane (CH4) detection system is presented and developed by using an alumina ceramic scattering material as its gas cell. Due to the material’s high scattering performance, the optical path length of the gas cell at 1653.7nm can reach 15.96 cm although its physical length along the light transmission direction is only 0.50cm. The wavelength modulation spectroscopy technique is employed to enhance the detection sensitivity, and the second harmonic gas absorption signal with low noise is detected and processed. The long-term stability of the system is investigated by the Allan deviation analysis method. Detection limits of 4.5 ppm and 2.6 ppm are achieved at averaging times of 20s and 200s, respectively. The dynamic gas exchange performance is also experimentally studied. The experimental results indicate that our system is a good choice for practical applications owing to its small volume, high sensitivity and stability.

Removal of all mosaic grating errors in a single interferometer system by a phase-difference reference window

yuxian lu, Xiangdong Qi, xiaotian li, haili yu, Shan Jiang, heshig bayan, and Yin Lu

Doc ID: 265116 Received 13 May 2016; Accepted 10 Aug 2016; Posted 11 Aug 2016  View: PDF

Abstract: An interference method to remove all mosaic grating errors using a phase-difference reference window without compensations for coupled mosaic errors or analyzing the far-field diffraction intensity patterns is proposed. The reference window is achieved by adding a small-aperture prism, therefore the incident light on the mosaic gratings contains two incident angles and optical paths, eliminating the uncertainty of longitudinal mosaic error in the interferometer. The mathematical model of the method is established and optical structure is designed. Interference fringes with reference window and alignment process are simulated, and the accuracy for mosaic errors are analyzed. The result shows that our method can eliminate longitudinal mosaic error and all other mosaic grating errors. The accuracy of angle mosaic errors can be less than 1μrad and position mosaic errors can be to nanometer level. Compared with far-field diffraction intensity patterns method, our method reduces the complexity of the optical structure and ensures the measuring accuracy.

Spectrometer Baseline Control via Spatial Filtering

Edward Wollack, Meghan BURLEIGH, Christina Richey, Stephen Rinehart, and Manuel Quijada

Doc ID: 269688 Received 30 Jun 2016; Accepted 28 Jul 2016; Posted 31 Aug 2016  View: PDF

Abstract: An absorptive half-moon aperture mask is experimentally explored as a broad-bandwidth means of eliminating spurious spectral features arising from reprocessed radiation in an infrared Fourier transform spectrometer. In the presence of the spatial filter an order of magnitude improvement in the fidelity of the spectrometer baseline is observed. The method is readily accommodated within the context of commonly employed instrument configurations and leads to a factor of two reduction in optical throughput. A detailed discussion of the underlying mechanism and limitations of the method are provided.

An easy-to-operate calibration method for structuredlight systems

Rui Chen, Jing Xu, zhiling ye, Jiadi Li, ken chen, and Yong Guan

Doc ID: 264523 Received 03 May 2016; Accepted 21 Jul 2016; Posted 20 Sep 2016  View: PDF

Abstract: Traditional calibration methods of structured light measurement systems are expensive and difficult to operate. In this paper, an accurate, low-cost, and easy-to-operate calibration method is proposed, where each projector pixel is considered as a line-of-sight in space, and an off-the-shelf LCD monitor is used to display the calibration pattern. Experimental results verify the accuracy and validity of the proposed method.

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.

Atmospheric propagation and combining of high power lasers: comment

Gregory Goodno and Joshua Rothenberg

Doc ID: 263228 Received 26 Apr 2016; Accepted 31 May 2016; Posted 29 Aug 2016  View: PDF

Abstract: Nelson et al [Appl. Opt. 55, 1757 (2016)] recently concluded that coherent beam combining and remote phase-locking of high power lasers are fundamentally limited by the laser source linewidth. These conclusions are incorrect and not relevant to practical high power coherently combined laser architectures.

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