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Full electro-optic terahertz time-domain spectrometerfor polarimetric studies

Federico Sanjuan, Gwenaël Gaborit, and Jean-Louis Coutaz

Doc ID: 325804 Received 16 Apr 2018; Accepted 21 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: We present a terahertz (THz) time-domain spectrometer dedicated to polarimetric studies. THz pulsesare generated through optical rectification in a <111>-cut cubic crystal. The <111> crystal cut producesa THz polarization state similar to that of the exciting laser beam. Detection of the THz pulses is performedby electro-optic sampling in a similar crystal and a dual detection scheme allows us to measuresimultaneously the two polarization components of the THz beam. We experimentally illustrate that thepolarization of the THz beam can be adjusted by adjusting the laser polarization. This technique alleviatesthe need for a polarization controller at THz frequencies.

Continuum removal for ground based LWIRhyperspectral infrared imagery applying non-negativematrix factorization

Bardia Yousefi, Saeed Sojasi, Clemente Ibarra-Castanedo, Xavier Maldague, Georges Beaudoin, and Martin Chamberland

Doc ID: 318836 Received 08 Jan 2018; Accepted 21 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: Continuum removal is vital in hyperspectral imageanalysis. It enables data to be used for any applicationand usually requires approximations or assumptionsto be made. One of these approximations isrelated to the calculation of the spectra of the background’sblackbody temperature. Here, we present anew method to calculate the continuum removal process.The proposed method eliminates the calculationfor ground-based hyperspectral infrared imageryby applying two acquisition sets before and after usingthe heating source. The approach involves a laboratoryexperiment on a long-wave infrared (7.7mmto 11.8mm - LWIR), with a LWIR-macro lens, an Infragoldplate and a heating source. To calculate thecontinuum removal process, the approach applies nonnegativematrix factorization (NMF) to extract Rank-1NMF, estimate the downwelling radiance and compareit with that of other conventional methods. NMF usesgradient-descent-based multiplicative rules (GD) andnon-negative least squares (NNLS) optimization algorithmsto obtain Rank-1 NMF. A comparative analysisis performed with 1%˘20% additive noise for all algorithmsby using the spectral angle mapper and normalizedcross correlation (NCC). Results reveal the promisingperformance of NMF-GD (average of 72.5% similaritypercentage using NCC) and NMF-NNLS (average of77.6% similarity percentage using NCC).

Windowed Fourier ridges for demodulation of carrierfringe patterns with nonlinearity: a theoreticalanalysis

Nimisha Agarwal, Chenxing Wang, and Kemao Qian

Doc ID: 332032 Received 17 May 2018; Accepted 21 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: Extracting phase or phase derivative accurately is the utmost requirement in optical metrology. However, inpractice, there are many error sources, among which nonlinear distortion in fringe patterns is often encountered.Several techniques have been proposed over time to remove the nonlinearity error. Among these techniques, thewindowed Fourier ridges (WFR) algorithm has been shown to be an effective solution insensitive to nonlinearity,but it lacks a theoretical justification. In this paper, we theoretically analyse the local frequency estimation errorand phase extraction error, which not only proves the mentioned insensitivity, but also supports performanceprediction and error control and thus is very important and useful in optical measurement practice. Thetheoretical results have been verified by computer simulations. Other error sources such as model error and noiseare also compared and discussed.

Extending depth-of-focus of fiber-optics optical coherence tomography using chromatic dual-foci design

Jinhan Li, Yuemei Luo, xianghong wang, Nanshuo Wang, EN BO, Si Chen, shufen chen, shi chen, Meng-Tsan Tsai, and Linbo Liu

Doc ID: 320780 Received 01 Feb 2018; Accepted 21 Jun 2018; Posted 22 Jun 2018  View: PDF

Abstract: We report a dual-foci fiber-optic probe design for depth-of-focus (DOF) extension in high-resolution endoscopic optical coherence tomography (OCT). We took the advantage of the broad spectral bandwidth of a supercontinuum source, and in the fiber probe chromatically shifted the foci of 750-1000 nm and 1100-1450 nm inputs axially. The interference signals from the two spectral bands were collected by a Si camera based spectrometer and an InGaAs camera based spectrometer, respectively. We verified the feasibility of the design using a phantom made of microparticles and swine small intestine tissue ex vivo. Results show that a transverse resolution below 5 µm over 300 µm could be maintained, the extended DOF is 2 times larger than that of the single focus probe by use of dual spectral band input and chromatic focal shift.

A broadband time resolved multi-channel fNIRSsystem to monitor in-vivo physiological changes ofhuman brain activity

Frederic Lange, Françoise Peyrin, and Bruno Montcel

Doc ID: 323340 Received 22 Feb 2018; Accepted 21 Jun 2018; Posted 22 Jun 2018  View: PDF

Abstract: We have developed a broadband Time Resolved multi-channel Near Infrared Spectroscopy system that canmonitor the physiological responses of the adult human brain. This system is composed of a supercontinuum laserfor the source part and of an ICCD camera coupled with an imaging spectrometer for the detection part. It allowsthe detection of the spectral, from 600 to 900 nm, and spatial dimensions as well as the arrival time of photonsinformation simultaneously. We describe the set up and its characterization in terms of temporal instrumentresponse function, wavelength sensitivity, and stability. The ability of the system to detect the hemodynamicresponse is then demonstrated. First, an in-vivo experiment on an adult volunteer was performed to monitor theresponse in the arm during a cuff occlusion. Secondly, the response in the brain during a cognitive task wasmonitored on a group of 5 healthy volunteers. Moreover, looking at the response at different time windows, wecould monitor the hemodynamic response in depth, enhancing the detection of the cortical activation. Those firstresults demonstrate the ability of our system to discriminate between the responses of superficial and deeptissues, addressing an important issue in fNIRS.

Comparative evaluation of signal-to-noise ratio andresolution of underwater imaging systems withartificial illumination

Alexander Luchinin, Lev Dolin, and Mikhail Kirillin

Doc ID: 327386 Received 30 Mar 2018; Accepted 21 Jun 2018; Posted 22 Jun 2018  View: PDF

Abstract: Characteristics of different underwater imaging systems are compared based on the results of Monte Carlosimulations of light transport in the sea water. The consideration includes systems with continuous-waveillumination, modulated illumination, pulsed systems with time gating detection and hybrid systems with probingpulse modulated at high frequency. To generalize the study, the ratio of SNR of different systems when imaging asinusoidal test pattern is analyzed. Pulsed systems are demonstrated to provide higher SNR as compared tocontinuous-wave systems for typical imaging distances varying in the range 35-60 m, while systems withmodulated illumination provide SNR comparable to that for continuous wave systems. Hybrid systems provide SNRcomparable to that in pulsed systems benefiting, however, from higher contrast transfer coefficient.

Investigation of Thermoforming Mechanism andOptical Properties Change of Chalcogenide Glass InPrecision Glass Molding

Lin Zhang, Wenchen Zhou, and Allen Yi

Doc ID: 330741 Received 30 Apr 2018; Accepted 21 Jun 2018; Posted 22 Jun 2018  View: PDF

Abstract: Chalcogenide glasses are emerging as enabling materials for low-cost infrared optics due to their transparency inshort-to-long wave infrared bands and the possibility to be mass produced by precision glass molding (PGM), anear net-shape process. This article is aimed to evaluate the thermoforming mechanism of As40S60 glass around itsglass transition temperature (Tg) and investigate its refractive index change and residual stresses in molded lensduring and after PGM. First, a constitutive model was introduced to precisely predict the material behavior in PGMby integrating subroutines into a commercial finite element analysis (FEA) software. This modeling approachutilizes the Williams-Landel-Ferry (WLF) equation and Tool-Narayanaswamy-Moynihan (TNM) model to describestress relaxation and structural relaxation behaviors, respectively. The numerical simulation revealed that thecooling rate above glass transition temperature (Tg) can introduce large geometry deviations to the molded opticallens. The residual stresses in a molded lens are generated mainly at the temperature around Tg due to theheterogeneity of thermal expansion from viscoelastic to solid state, while structural relaxation occurs during theentire cooling process. The refractive index variations inside molded lenses were predicted by performing FEMsimulation and further evaluated by measuring wavefront changes using an infrared Shack-Hartmann wavefrontsensor (SHS), while the residual stresses trapped inside the molded lenses were obtained by using a birefringencemethod. Combination of measurements of the molded infrared lenses and numerical simulation results providedan opportunity for optical manufacturers to gain better understanding of the mechanism and optical performanceof chalcogenide glasses during and after PGM.

Modeling for Detecting Weld Defects Based onMagneto-optical Imaging

Xiangdong Gao, Guohua Li, Ziqin Chen, Chongzhou Lan, and Yanfeng Li

Doc ID: 319355 Received 08 Jan 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: Magneto-optical (MO) imaging non-destructive testing (NDT) method for ferromagnetic weldments has beenproposed. The mechanism of MO imaging was analyzed by the Faraday MO effect, magnetic domain theory andmagnetic hysteresis loops. Then the relation between MO images and their corresponding excitation voltages wasinvestigated. To explain the MO imaging system, magnetic domain distribution models of various welding stateswere established. These models are excited by two kinds of magnetic fields. One is the external magnetic field (Hex)and the other is a weldment remanence field (Mr) after Hex is removed. Relations of magnetic field excitationvoltages, thickness of the spacer plate and the corresponding MO images were also researched, which indicates theproposed NDT method can be used to detect incomplete penetration defect. Then, an experiment which uses MOimaging to detect the defects of high strength steel (HSS) weldment was performed. Experimental results provedthis method can detect crack, sag and incomplete penetration of weldment effectively. Finally, a series of weldedjoint MO images of the HSS weldment were captured, which are used as the input data of defect classification modelestablished by using principal component analysis (PCA) and error back propagation (BP) neural network, and theaccuracy of this classification model can achieve at 92.8%.

Interferometric Particle Imaging of ice particles usinga multi-view optical system

Mohamed Talbi, Gerard Grehan, and Marc Brunel

Doc ID: 328049 Received 10 Apr 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: Interferometric Particle Imaging (IPI) enables particle’s size estimation in a wide range [from 10 μm to a few millimeters]depending on the optical system design. With a multi-view optical system it is possible to extract more information about the 3Dmorphologyof the particle. In this study, multi-view interferometric out-of-focus imaging of ice particles is performed in abackward scattering configuration. It is used to estimate ice particle volume, and thus to reduce uncertainty concerning particle’ssize estimation. It is further used to better analyze the presence of nearby particles whose images overlap.

Transverse mode instability threshold enhancementin Yb-doped fiber lasers by cavity modification

Kamran Hejaz, Mahdi Shayganmanesh, Ali Roohforouz, Reza RezaeiNasirabad, ali abedinajafi, saeed azizi, and Vahid Vatani

Doc ID: 328221 Received 11 Apr 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: To enhance transverse mode instability (TMI) threshold of a fiber oscillator, a novel configuration ispresented. In this configuration the oscillator cavity length is considerably reduced and the remaining activefiber is released out of the cavity to absorb rest of pump power and amplify the output signal of the cavity. Infiber oscillators, the index gratings generated by both forward and backward propagating signals caninteract with light propagating in the backward and forward directions and degrades the output beamquality. In proposed modified configuration, due to lower intra-cavity forward and backward signal powerthe index grating is smoothed and TMI threshold is increased. Experimental results indicate that thismodified configuration has higher TMI threshold than a conventional fiber oscillator. Finally higher TMIthreshold is achieved in bidirectional pumping scheme of modified configuration.

Spectrum reconstruction in Fourier transform imagingspectroscopy based on high-performance parallelcomputing

Weikang Zhang, Ven desheng, Zongxi Song, gang liu, Wei Xin, and zhixin li

Doc ID: 330320 Received 27 Apr 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: In this paper, parallel-processing algorithms for spectrum reconstruction in Fourier transform imagingspectroscopy are proposed using high-performance parallel computing. Because of the huge amount ofinterference data, traditional algorithms are inefficient and time-consuming. It is necessary to processinterference data as soon as possible to form spectral data for research and economy. We take advantageof parallel computing based on the graphics processing unit (GPU) to enable higher efficiency and reducedoperation time. Furthermore, traditional algorithms for processing interferograms on the centralprocessing unit (CPU) are introduced for comparison. The experimental results show that the runtime isreduced from 1.144 ms to 0.332 ms using our parallel algorithms, and for huge data, the designed parallel-processing mechanism on the GPU has advantages over the traditional pipeline.

Subwavelength-spaced transmissive metallic slits for360-degree phase control by using transparentconducting oxides

Soo Jin Kim and Junghyun Park

Doc ID: 331067 Received 07 May 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: We propose an apparatus that allows for active control of the transmission phase up to 360 degrees throughsubwavelength-spaced metallic slits partially filled with indium-tin-oxide (ITO). Incident light is coupled to theguided mode in the metallic slit at one side. After going through the slit with a certain length, light is coupled out tofree space at the other side. The transmission phase is governed by the mode index and the slit length. By applyingbias to the ITO in the metallic slit, it is possible to control the mode index, which in turn leads to tuning of thetransmission phase. The judiciously designed slit configuration facilitates the individual control of the relativephase between neighboring slit with a subwavelength distance. This phenomenon is different from resonancebasedmetasurface approaches that suffer from limited range of the phase change. It is believed that the devisedconfiguration may open novel promising future applications such as hologram imaging with phase spatial lightmodulators, light-field infrared microscopy, and beam forming and steering devices.

High resolution two-photon microscopy using pixel reassignment

Shiyi Sun, Shaocong Liu, Wensheng Wang, zhimin zhang, Cuifang Kuang, and Xu Liu

Doc ID: 331166 Received 08 May 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: An imaging system combines parallel detection and two-photon excitation is presented in this paper. In the proposed method, seven avalanche photodiodes (APD) are used in the detection path. The light is guided into the APD sensor by a fiber bundle with seven fibers. The circular arranged fiber end faces together function as a detection array. The outer contour fiber ends deviate from optical axis center and thus obtaining higher frequency information. Seven images are acquired simultaneously by the detection array. By using de-convolution and pixel reassignment to process the images acquired, both the resolution and the contrast of the final image are enhanced. The capability of image quality enhancement of the system constructed is demonstrated successfully both by theoretical simulation and experimental results.

High Power, Continuous-wave SupercontinuumGeneration in Highly Nonlinear Fibers Pumped withHigh Order, Cascaded Raman Fiber Amplifiers

vishal choudhury, Arun S, Roopa Prakash, and V R Supradeepa

Doc ID: 331778 Received 15 May 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: A novel method for efficient generation of high power, equalized continuous-wave supercontinuum source in an allconventional silica fiber architecture is demonstrated. Highly nonlinear fiber (HNLF) is pumped in its anomalousdispersion region using a novel, high power, L-band laser. The L-band laser encompasses a 6th order cascadedRaman amplifier which is pumped with a high power Ytterbium doped fiber laser and amplifies a low-power,tunable L-band seed source. The supercontinuum generated 35W of power with ~40% efficiency. TheSupercontinuum spectrum was measured to have a high degree of flatness of better than 5 dB over 400 nm ofbandwidth (1.3–1.7μm, limited by spectrum analyzer range) and a power spectral density in this region of >50mW/nm. The extent of the SC spectrum is estimated to be upto 2 μm

Bessel-like beam generated by an axicon based onparallel-plate waveguides

Tingting Shen, Tingting Lang, WU MENGRU, and Zhanghua Han

Doc ID: 325965 Received 14 Mar 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: The axicon is the simplest and most effective optical element for generating the zero-order Bessel-like beam. Thezero-order Bessel-like beam has the characteristics of small spot size, high brightness, good direction and largecollimation distance, can be applied to optical micro-manipulation and power transmission. In this paper, weproposed and designed a structure for phase manipulation based on PPWGs can be used to realize the functionalityof the axicon in the THz region. Meanwhile, we characterized the influence of the cone angle of the axicon and thewaist radius of the incident Gaussian beam on the generated zero-order Bessel-like beam by simulation. The planarstructure consisting of a parallel stack of thin copper plates can be easily fabricated to fulfill the phase requirementto realize the zero order Bessel-like beam, and also can be utilized in THz imaging systems, THz sensing systems,THz communication systems, etc.

Generation of optical Bessel beams with arbitrarilytrajectories using a magnetic-liquid deformable mirror

Mathieu Fortin, Michel Piche, Denis Brousseau, and Simon Thibault

Doc ID: 326759 Received 03 Apr 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: We propose a new strategy to curve the trajectory of the central lobe of a zero-order Bessel beam and a first-order Bessel beam along their propagation axis. Our method involves modifying the phase of a beamthat is incident on an adaptive mirror. As examples, we show that the most intense lobe of the beam can follow a parabolic trajectory, a cubic trajectory or a trajectory made by a combination of these orders. By using a phase correction emulating the effect of cylindrical mirrors, the central lobe always preserves its symmetry. Theoretical simulations were reproduced in laboratory using a magnetic-liquid deformable mirror. The parabolic trajectory of the 60-μm central spot of a zero-order Bessel beam exhibits a 0.6-mm off-axis shift after 30-cm length propagation.

DEVELOPMENT OF A PHOTOPOLYMER HOLOGRAPHIC LENS FORCOLLIMATION OF LIGHT FROM A GREEN LED

Sanjay Keshri, Kevin Murphy, Vincent Toal, Izabela Naydenova, and Suzanne Martin

Doc ID: 327494 Received 18 Apr 2018; Accepted 19 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: A Holographic Optical Element (HOE) was developed to collimate a monochromatic Light Emitting Diode (LED). Thefabrication was achieved by the interference of collimated and diverging beams from a 532 􀢔􀢓 laser to producethe required photonic structure in a self-developing photopolymer material. The experimental values of diffractionefficiency and spatial period across HOE were compared with their expected theoretical values. Good agreementwas found for the spatial period however the diffraction efficiency varied significantly across the lens. In thispaper, two approaches have been taken to address this variation (i) modification of recording geometry (ii)optimization of recording intensity and exposure time at constant energy. The performance of an optimized HOE(cylindrical holographic lens) was then demonstrated using a 532 􀢔􀢓 laser beam. The optimized conditions for thecylindrical holographic lens was used to fabricate a spherical holographic lens of same numerical aperture for LEDapplication. This type of lens has the potential to be used in combination with LED sources.

Modeling Mutually Coupled Non-IdenticalSemiconductor Lasers on Photonic Integrated Circuits

Fabien Dubois, Masoud Seifikar, Alison Perrott, and Frank Peters

Doc ID: 327316 Received 29 Mar 2018; Accepted 19 Jun 2018; Posted 19 Jun 2018  View: PDF

Abstract: We model the situation of two lasers in a face to facearrangement, optically coupled through an attenuatingelement, where the distance between the lasers is ona scale typical in photonic integration (100’s of mm tomm’s). We acccount for the existence of a frequency differencebetween the two single moded lasers. A modifiedversion of the Lang-Kobayashi equations was employedto describe the interaction. By solving this delaydifferential equation (DDE) system we characteriseddifferent dynamical regimes including, one and twocolour states, and self pulsations. We focus on the effectvarying coupling strength and detuning betweenthe lasers has on the frequencies of the lasers. Using theresults of this frequency study, we identify the bifurcationscausing changes between the different frequencyregimes.

3D characterization of debris clouds underhypervelocity impact with pulsed digital inlineholography

Yonggang Zhou, Zhiliang Xue, Yingchun Wu, Aimin Xie, and Xuecheng Wu

Doc ID: 326950 Received 26 Mar 2018; Accepted 19 Jun 2018; Posted 20 Jun 2018  View: PDF

Abstract: The increasing space debris poses a great threat to in-orbit spacecrafts and satellites, because its hypervelocityimpact can bring about fatal mechanical and electrical damages to them. This work applies pulseddigital inline holography (DIH) to measure 3D positions and shapes of the debris clouds generated bythe hypervelocity impact in Whipple shield. Detailed operation procedures of synchronizing the pulseDIH system with the impact event and removing the strong plasma radiation are presented, ensuring thesuccessful capture of the transient state of ultrafast ejecta. Experiments on a 2.25 mm aluminum sphereimpacting on an 0.5 thickness aluminum target plate with a velocity of 3.6 km/s are carried out on thehypervelocity impact research center (HIRC) of China Aerodynamics Research and Development Center(CARDC), and results show that the holographic fringes are clearly recorded and the debris fragments arereconstructed and located accurately, agreeing well with the results measured by laser shadowgraph. Thiswork demonstrates the powerful capability and great potential of DIH in the diagnostics of hypervelocityimpact.

Optimized Laser Induced Breakdown Spectroscopy for theDetermination of High Toxic Lead in Edible Colors

Imran Rehan, M Zubair Khan, Kamran Rehan, sami ullah abrar, Zahid Farooq, Sabiha Sultana, Najm us Saqib, and hafeez anwar

Doc ID: 325335 Received 05 Mar 2018; Accepted 19 Jun 2018; Posted 19 Jun 2018  View: PDF

Abstract: An optimized laser induced breakdown spectroscopy (LIBS) system was utilized as a robust toolfor the detection of high toxic lead (Pb) in the often used edible colors available in the localmarket. Edible colors are extensively used in different food stuffs and sweet dish items. To attaina high sensitive LIBS system for the determination of trace amounts of toxic Pb in edible colorsand to achieve the best detection limit, various parametric dependence studies was performed.The quantitative determinations were accomplished under the condition of local thermodynamicequilibrium (LTE) in terms of optically thin plasma. Besides toxic Pb, other elements like Ca,Mg, Fe, and Na were also detected in edible colors. To estimate the concentration of toxic lead inedible colors, the calibration curves were plotted by preparing standard samples of different leadconcentrations in edible colors matrix. Results of LIBS technique were compared with theoutcomes of same samples studied using a standard analytical technique of inductively coupledplasma-optical emission Spectroscopy (ICP-OES) to confirm the contemporary LIBS setup. Thecolor samples were found above the safe permissible level due to the mass of toxic lead (Pb).Limit of detection (L.O.D.) of the LIBS setup was found as 0.86 +/- 0.03 ppm for toxic leadpresent in edible color samples.

Visualizing spatial distribution of atmosphericnitrogen dioxide by means of hyperspectral imaging

Naohiro Manago, Yohei Takara, Fuminori Ando, Naoki Noro, Makoto Suzuki, Hitoshi Irie, and Hiroaki Kuze

Doc ID: 324730 Received 23 Feb 2018; Accepted 18 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: We have developed a method to monitor the slant column density of nitrogen dioxide in the lower troposphereusing a compact hyper spectral camera with a high spectral resolution of 1 nm at the full width half maximum.Measurements of skylight spectra have been conducted in wavelength regions of 460 - 490 nm and 550 - 610 nm toretrieve the slant column densities of nitrogen dioxide, in addition to water vapor and oxygen dimer. The results ofground-based measurements are shown for the two cases of urban air pollution and aircraft emission near anairport runway.

Noise reduction in computational ghost imaging byinterpolated monitoring

Yang Zhaohua, yuzhe sun, Shaofan Qu, Yuanjin Yu, ruitao yan, Aixin Zhang, and Ling-An Wu

Doc ID: 327095 Received 28 Mar 2018; Accepted 18 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: An interpolation computational ghost imaging (ICGI) method is proposed and demonstrated that is able to reduce the noiseinterference from a fluctuating source and background. The noise is estimated through periodic illuminations by a specific assaypattern during sampling, which is then used to correct the bucket detector signal. To validate this method simulations and experimentswere conducted. Light source intensity and background lighting were randomly varied to modulate the noise. The results show thatgood quality images can be obtained, while with conventional computational ghost imaging (CGI) the reconstructed object is barelyrecognizable. The ICGI method offers a general approach applicable to all CGI techniques, which can attenuate the interference fromsource fluctuations, background light noise, dynamic scattering and so on.

Fourier transform infrared spectrometer based on anelectrothermal MEMS mirror

DongLin Wang, Hongqiong Liu, Jicheng Zhang, Qiao Chen, Wei Wang, Xiaoyang Zhang, and Huikai Xie

Doc ID: 330116 Received 23 Apr 2018; Accepted 18 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: This paper presents a micro Fourier transform infrared spectrometer (μFTIR), enabled by an H-shapedelectrothermal microelectromechanical systems (MEMS) mirror. A special driving method was developed forobtaining a linear, uniform-speed motion of 186 μm and the tilting angle of the MEMS mirror was as small as 0.06°,so there was no need of complex closed-loop control. A telecentric lens was employed in the interferometer of theμFTIR to reduce the influence of the MEMS mirror tilting effect. Also, a new phase interpolation algorithm, insteadof the traditional fringe interval method, was applied in the process of the spectral reconstruction to improve thespectral stability. Finally, the new μFTIR was applied in the composition prediction of soybeans, and theexperimental results show that it can accurately measure grain moisture, protein and fat contents.

Modeling of an Active THz Imaging System inBrownout Conditions

Clotilde Prophète, Romain Pierrat, Hervé Sik, Emmanuel Kling, Remi Carminati, and Julien de Rosny

Doc ID: 327111 Received 28 Mar 2018; Accepted 18 Jun 2018; Posted 19 Jun 2018  View: PDF

Abstract: We present a theoretical evaluation of a sub-THz system to image through a scattering medium composedof scatterers of sizes close to the wavelength. We specifically study the case of sand grain clouds createdby helicopter rotor airflow during landing in arid areas. The different powers received by one pixel of amatrix made of sub-THz sensors are identified. Photometric and antenna-based sensors are considered.Besides the thermal contribution to the noise, we focus our attention on the radiation backscattered bythe brownout. It appears that a configuration where the source and the camera are distant is the mostpromising configuration and is realistic for embedded systems.

Hybrid attack on an optical cryptosystem based onphase-truncated Fourier transforms and a randomamplitude mask

YI XIONG, Aohan He, and Chenggen Quan

Doc ID: 332011 Received 17 May 2018; Accepted 18 Jun 2018; Posted 19 Jun 2018  View: PDF

Abstract: In this paper, the security of a cryptosystem based on phase-truncated Fourier transforms (PTFTs) and a randomamplitude mask (RAM) is evaluated. In the cryptosystem, fake keys used as encryption keys in the second PTFTbasedstructure are generated by the first PTFT-based structure in which the RAM is encoded by random phasemasks (RPMs) used as public keys. Compared with the classical PTFT-based encryption scheme, the security levelof the cryptosystem is improved by using a cascaded PTFTs to encode the encryption keys and the plaintextsimultaneously. However, it is found that a known plaintext-ciphertext pair can provide enough constraints in theiterative process to retrieve the fake keys which then can be used to retrieve unknown arbitrary plaintext from thecorresponding ciphertext. Based on the analysis, we propose a specific attack based on hybrid iterative processesto break the cryptosystem. Two iterative processes with different constraints are involved in the proposed attack.The first known-plaintext attack (KPA)-based iterative process is used to retrieve two fake keys with the help oftwo public keys and a known plaintext-ciphertext pair, while the second amplitude-phase retrieval algorithmbasediterative process with a median filter is employed to retrieve the plaintext from the correspondingciphertext using two retrieval fake keys. To the best of our knowledge, it is the first time that the cryptosystem isattacked by the KPA-based iterative attack successfully. Numerical simulation results validate the feasibility andeffectiveness of the proposed attack.

Integrated design of pi/2 converter and itsexperimental performance

Junliang Jia, qichang li, Kepeng Zhang, Dongxu Chen, Chenhui Wang, Hong Gao, fuli li, and Pei Zhang

Doc ID: 331064 Received 08 May 2018; Accepted 17 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: Transverse modes of light have been widely exploited in both classical and quantum optics in recent years. Among the devices to manipulate the transverse modes of light, π/2 converter is a fundamental and important one which analogs to the quarter wave plate in the polarization degree of freedom. While π/2 converter is typically achieved by a pair of well-adjusted cylindrical lenses, it suffers the complexity in its installation and adjustment, which strongly limits its practical applications. Here an integrated design of π/2 converter is reported. We compute the necessary parameters for manufacture according to refractive theory of cylindrical-surface. Based on the change of refractive indices, we simulate the response of Gouy phase versus wavelengths.We also implement an experiment to convert Laguerre-Gaussian modes to Hermite-Gaussian modes by using our compact π/2 converter to confirm its simple adjustment and reliable performance in practice.

Effect of Mechanical Error on Dual-Wedge LaserScanning System and Error Correction

Yunaho Ge, Jihao Liu, Fenfen Xue, Enguang Guan, Weixin Yan, and Yanzheng Zhao

Doc ID: 318730 Received 23 Feb 2018; Accepted 17 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: Compared with the traditional mechanical beam deflectorin a beam-scanning system, the dual-wedge scanningsystem has several advantages,for example compactstructure, fast scanning speed, and low power consumption.High accuracy is the most important factorin dual-wedge scanning, but mechanical errors causedby machining or assembly errors adversely affect thisscanning accuracy. Horizontal and angular mechanicalerrors appear between the incident light and the dualwedgecentral optical axes. By building a mathematicalmodel of an ideal dual-wedge scanning trajectory and atrajectory affected by mechanical errors, this paper analyzesthe types and degree of influence on the scanningprocess, as well as the sensitivity of scanned imagesto different errors. Results show that the angularerror has the most significant influence on the scanningimage accuracy, in terms of trajectory shape and coverage.To correct the angular error, the two degrees-offreedom(DOF) flexible fine-tuning mechanism is customizedbased on the principle of the cantilever beamtype. After finite element analysis(FEA) and experimentalvalidations, the fine-tuning mechanism can guaranteethat the angular error in the dual-wedge central opticalaxes will be lower than 0.05 degree, thus ensuringscanning trajectory accuracy.

Time-resolved measurements of a swirl flame at 4 kHzvia computed tomography of chemiluminescence

Tao Yu, Can Ruan, Hecong Liu, Weiwei Cai, and Xingcai Lv

Doc ID: 321064 Received 27 Feb 2018; Accepted 17 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: A computed tomography of chemiluminescence (CTC) system was implemented to provide time-resolved 3Dmeasurements of an unconfined turbulent swirl flame. This system was designed in a cost-effective manner andemployed three customized view registration assemblies to simultaneously capture eight projections of the targetflame at a repetition rate of 4 kHz. Both time-resolved and time-averaged tomographic reconstructions wereperformed based on data acquired for a duration of 250 ms. Both qualitative and quantitative validationssuggested the correctness of our implementation. The time-resolved instantaneous reconstructions successfullycaptured the evolution of the structural features of the swirl flame such as local extinctions and the helical mode.Based on the reconstructions the centroids of chemiluminescence for all the layers were calculated. The trajectoryof these centroids provided insights into the flow motion and suggested a rotating helical structure of the swirlflame. These results demonstrated the feasibility of resolving the dynamics of turbulent swirl flames with a kHztemporal resolution using the relatively inexpensive CTC system.

Intensity-dependent Nonlinear Refraction ofAntimonene Dispersions in the Visible and NearinfraredRegion

Gaozhong Wang, Sean Higgins, Kangpeng Wang, Daniel Bennett, Nina Milosavljevic, John Magan, Saifeng Zhang, Xiaoyan Zhang, Jun Wang, and Werner Blau

Doc ID: 321491 Received 16 Mar 2018; Accepted 16 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: Antimonene is a stable 2D allotrope of antimony which is predicted to have direct bandgap, high third-order opticalnonlinear susceptibility and high electron mobility. These properties give it huge potential applications in photonics andoptoelectronics. However, the nonlinear refractive response of antimonene dispersions have not been fully investigated,which is the key to nonlinear refraction-based devices. In this work, we investigated the optical nonlinearities of theantimonene dispersions by spatial self-phase modulation (SSPM) at 405, 785 and 1064 nm wavelengths. The SSPM ringswere observed at 405, 785 and 1064nm, implying the broadband nonlinear optical response of antimonene dispersionsfrom visible to near-infrared. The effective nonlinear refractive index, n2, and the third-order susceptibility, χ(3), of theantimonene dispersion were measured to be ~10-5 cm2 W-1 and ~10-8 esu, respectively. Furthermore, the nonlinearity ofantimonene was demonstrated to be tuneable by the laser intensities. The relative change of nonlinear refractive index,Δn2e/n2e, was observed to range from 14% to 63% for different intensities. Our results will be helpful for the photonicapplications of antimonene in a broadband wavelength range, such as optical modulator and switcher.

Scaling ultrafast laser pulse induced glassmodifications for cleaving applications

Klaus Bergner, Michael Müller, Robert Klas, Jens Limpert, Stefan Nolte, and Andreas Tünnermann

Doc ID: 331483 Received 10 May 2018; Accepted 15 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: Ultrashort laser pulses allow for in-volume processing of glass through non-linear absorption. This resultsin permanent material changes, largely independent of the processed glass and is of particular relevancefor cleaving applications. In this article, a laser with a wavelength of 1030nm, pulse duration of19ps, 10kHz repetition rate and burst regime consisting of either 4 or 8 pulses with a intra-burst pulseseparation of 12.5ns is used. Subsequently, a Gaussian-Bessel focal line is generated in a fused silica substratewith the aid of an axicon configuration. We show how the structure of the modifications, includingthe length of material disruptions and affected zones can be directly influenced by a reasonable choiceof focus geometry, pulse energy and burst regime. We achieve single shot modifications with 2 m indiameter and 7.6mm in length, exceeding an aspect ration of 1:3.800. Furthermore, a maximum length of10.8mm could be achieved with a single shot.

Multistage Single Clad 2μm TDFA with a SharedL-Band Pump Source

Robert Tench, Clement Romano, and Jean-Marc Delavaux

Doc ID: 327569 Received 03 Apr 2018; Accepted 15 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: We report the experimental performance and simulation of a multiwatt two-stage TDFA using an L-band (1567 nm)shared pump source. We focus on the behavior of the amplifier for the parameters of output power Pout, gain G, noisefigure NF, signal wavelength λs, and dynamic range. We measure the spectral performance of the TDFA for threespecific wavelengths (λs= 1909, 1952, and 2004 nm) chosen to cover the low-, mid-, and upper-wavelength operatingregions of the wideband amplifier. We also compare the performance of the two-stage shared pump TDFA with arepresentative one stage shared pump amplifier. A comparison of experimental results with simulation is presented.

The Impacts of Collection System on Laser-inducedBreakdown Spectroscopy Signal Detection

Tianqi Li, Sahar Shata, Zongyu Hou, Jian Dong, and Zhe Wang

Doc ID: 330120 Received 24 Apr 2018; Accepted 15 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: Collecting strong enough and repeatable signals from laser-induced plasmas is the primary goal of the Laser-Induced Breakdown Spectroscopy (LIBS) optical detection systems. Typically, the light emitted from the plasma isrefracted by the lens, collected by the fibre, and measured by the spectrometer. In the present work, we establisheda three-dimensional model to systematically evaluate the overall emission collected from different position of theplasma for a typical optical collection system composed of a focus lens and a collection fibre and sensitivityanalyses were further performed. In addition, experimental were conducted and partially validated the model.Results showed that for the collection system with optical fibre located on the focal point of the collection lens, thecollection efficiency distribution is almost constant within a large cylindrical-shape area; while for that of locatedoff the focal point, there would be a rhombus-shaped area with higher collection efficiency than other areas. Thismuch higher collection efficiency area is small in size but has large impact on the detected spectral intensity. Thespatial distributed collection efficiency on the lens parameters such as size and position was further discussed toclarify the impacts of the collection system. Furthermore, sensitivity analysis were performed to evaluate theimpact of the collection system on the signal repeatability. Based on these calculations, recommendations for thedesign of the collection for optimized spectral intensity and stability were proposed.

Optical design of dental light using a remotephosphor LED package for improvingillumination uniformity

Sie-Wook Jeon, Sunghyun Kim, Jina Choi, Inseok Jang, Younghyun Song, Wan Ho Kim, and JaePil Kim

Doc ID: 330982 Received 09 May 2018; Accepted 15 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: The projection-type dental lighting based on the remote phosphor light emittingdiode (LED) package is designed to enhance uniformity of illuminance and correlated colortemperature (CCT) on target plane and to remove glare in the eyes of patient. This dentallighting enables dentists to illuminate effectively patient’s mouth by increasing the inner area(50 mm x 25 mm) described in ISO 9680. The optical module comprised of the LED packageand optical lens is modelled to satisfying the inner area wider than 100 mm x 50 mm andilluminance over 5,000 lx per the designed optical module. The fabricated prototype dentallighting contains four optical modules, and the maximum illuminance is 22,786 lx. Themeasured inner area is 105 mm x 74 mm, and the ratio of inner area in outer area is about76%. Also, the CCT variation is below 450 K in total illuminance pattern.

Determination of optimized removal functions forimprinting continuous phase plates using fuzzy theory

Jing Hou, Mingchen Cao, Hongxiang Wang, Huiying Zhao, Bo Zhong, Zhuangde Jiang, and Yaguo Li

Doc ID: 313015 Received 08 Nov 2017; Accepted 14 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: A new evaluation method based on fuzzy theory was proposed to assess the manufacture efficiency and accuracy ofcontinuous phase plate (CPP) with magnetorheological finishing (MRF) imprinting. Two-dimensional sinusoidalwaves were employed to verify the effectiveness of the proposed method theoretically and experimentally in termsof two parameters, error root mean square (ERMS) and processing time, which indicate the accuracy and efficiencyof CPP manufacture. The weight factor was used for balancing the priorities of processing time and accuracy in ourmethod. The simulations and experiments were compared based on our proposed method. The results show thatthe optimum removal functions for various spatial periods are in good agreement between simulations andexperiments, and furthermore relative errors are 6.07%, 2.62%, and 6.00% for CPP with spatial periods of 12mm,18mm, 30mm, respectively. All the results indicate that the method provides a valid and feasible way to select theoptimized removal function for imprinting patterns of CPPs.

Rectangular Structure Based Pose Estimation Methodfor Non-cooperative Rendezvous

Limin Zhang, Feng Zhu, Yingming Hao, and Wang Pan

Doc ID: 326394 Received 20 Mar 2018; Accepted 14 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: Pose estimation for spacecraft is widely recognized as an important technology for space applications. Many spacemissions require accurate relative pose between the chaser and the target spacecraft. Stereo vision is a usual meanto estimate the pose of non-cooperative target during proximity operations. In this paper, an accurate algorithmfor pose estimation is proposed by taking advantage of the geometric structure of the object. With stereo cameras,our approach employs the corners of the solar panel as features and uses bundle adjustment to improve theaccuracy. Simulation results demonstrate that our method improves the precision and robustness fornon-cooperative spacecraft pose estimation. Our laboratory experiments further validate the approach. Theresults show that the rotation angle error of our method is within 0.8°, and the measurement error in translation isless than 0.4% at the distance from 3m to 1.2m.

Stokes imaging spectropolarimeter based onchanneled polarimetry with full-resolution spectraand aliasing reduction

Chunmin Zhang, Naicheng Quan, and Tingkui Mu

Doc ID: 327503 Received 03 Apr 2018; Accepted 14 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: A Stokes channeled interference imaging spectropolarimeter with full-resolution spectra and aliasing reduction ispresented. The sensor uses a Wollaston prism, a Savart polariscope and a linear analyzer as birefringentinterferometer and two high-order retarders to incorporate channeled polarimetry employing tempo-spatiallymixed modulated mode with no internal moving parts and offers a robust system. The performance of the system isverified through laboratory tests. Compared with the previous sensors, the most significant advantage of thedescribed instrument is that the reconstructed spectra retain the resolution of the interferometer and the errors inthe reconstructed spectral resolved polarization state caused by aliasing between the interference channels aresuppressed effectively. Additionally, the advantages of the interferometer are maintained, such as compactstructure and high optical throughput.

Short Fiber Resonant Optic Gyroscope Using the High-Frequency Pound-Drever-Hall Technique

Xiaojun Jin, Yi Lin, Ying Lu, Huilian Ma, and Zhonghe Jin

Doc ID: 327956 Received 09 Apr 2018; Accepted 13 Jun 2018; Posted 13 Jun 2018  View: PDF

Abstract: Optical gyros are attractive angular rotation sensors based on the Sagnac effect. The phase modulation technique isadopted to detect the weak resonant frequency shift induced by the Sagnac effect, which determines the detectionsensitivity of the gyros. The Pound-Drever-Hall (PDH) modulation is a mature laser frequency stabilizationtechnique which is widely recognized. A resonant optic gyros equipped with a short and high-finesse fiber ringresonator employing the high-frequency PDH modulation technique is proposed and demonstrated. Themodulation index and frequency are optimized to maximize the slope of the demodulation curve. Compared withthe low-frequency modulation, the high-frequency PDH modulation increases the slope of the demodulation curveby a factor of 1. and achieves an extra 15.8 dB of laser frequency noise suppression. The bias stability of the gyrooutput is improved from 9.6°/h to 8°/h and the equivalent lock-in frequency accuracy increases 12 dB.

Study on baseline correction methods for the FTIRspectra with different signal-noise ratios

Xianchun Shen, Shubin Ye, Liang Xu, Rong Hu, Lin Jin, HanYang Xu, Jianguo Liu, and Wenqing Liu

Doc ID: 330945 Received 04 May 2018; Accepted 13 Jun 2018; Posted 14 Jun 2018  View: PDF

Abstract: Removing the baseline from the spectra, which are measured by Fourier transform infrared spectrometer, is animportant pre-processing step for further spectra analysis such as quantitative and qualitative analysis. Anautomatic baseline correction method named iterative averaging, which is based on the basic knowledge of movingaverage, is presented. We also compared it with other methods, like rubber-band, adaptive iterative reweightpenalized least squares, automatic iterative moving average and morphological weighted penalized least squares,using simulated and experimental spectra with different signal-noise ratio to evaluate the performance of thesemethods by performance metrics and to select an appropriate method to analyze FTIR spectra. Performancemetrics such as root-mean-square error, goodness-of-fit coefficient and chi-square, are calculated. Iterativeaveraging method achieves the best results which are judged by performance metrics values, when it is applied tothe FTIR spectra with different SNRs. It also can correct the baseline of the FTIR spectra automatically and improvethe capability and adaptability of the unsupervised online analysis of the FTIR system effectively.

High-power visibly emitting Pr3+:YLF laser endpumpedby single-emitter or fiber-coupled GaN bluelaser diodes

Hiroki Tanaka, Shogo Fujita, and Fumihiko Kannari

Doc ID: 331661 Received 14 May 2018; Accepted 13 Jun 2018; Posted 14 Jun 2018  View: PDF

Abstract: We demonstrate the high-power continuous-wave operation of a Pr3+:YLF laser end pumped by blue laser diodes. As thepump source, we used four 5-W single-emitter blue laser diodes and a >20-W fiber-coupled module. In single-emitterdiodepumping, we obtained pump-limited output powers of 6.7 and 3.7 W at 640 and 607 nm, respectively. Wesuccessfully suppressed thermal aberration and obtained an output power of 3.4 W at a slope efficiency of 25% at 640nm with good beam quality in the fiber-coupled module pumping.

Spatially Resolved Temperature Measurement in CO2Arc under Different Gas Pressures

Hao Sun, Shaodi Fan, Yifei Wu, Yi Wu, Fei Yang, Mingzhe Rong, and Fengfeng Jiang

Doc ID: 328464 Received 17 Apr 2018; Accepted 13 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: Carbon dioxide (CO2) is a promising alternative to sulfur hexafluoride for high voltage circuit breaker application.It is important to have a detailed understanding of CO2 arc properties. In this paper, radial temperaturedistribution of the free burning direct current arc in pure CO2 was investigated. Optical emission spectrometry wasapplied under different pressures (0.5atm, 1atm, 1.5atm) and at different axial positions (1mm, 2mm, 3mm abovethe cathode). Assuming local thermodynamic equilibrium, the Fowler-Milne method was adopted for O I 715.67nmand O I 777.19nm in the periphery of the arc and single line method was adopted for C II 657.81nm near the centerof the arc. Radial temperature profiles obtained by these two methods were combined at the position wherenormal temperature was assigned. The results indicate that near the center of the arc, higher pressure would leadto lower temperature; as the distance from the cathode to the position measured increases, the maximumtemperature in the arc center would decrease. In addition, the temperature would decrease more sharply towardthe periphery if the central temperature of the arc is higher.

Low-coherence interferometry for phase-sensitivemeasurement of optical rotation

Chao Liu, Tianqi Li, and Taner Akkin

Doc ID: 325826 Received 12 Mar 2018; Accepted 13 Jun 2018; Posted 13 Jun 2018  View: PDF

Abstract: We present phase-sensitive measurement of optical rotation using spectral-domain and time-domain low-coherenceinterferometry. The method utilizes two decorrelated polarization states and simultaneous dual-channel detectionprovided by polarization-maintaining-fiber based implementation. The sample is placed between polarization optics tocontrol and switch left and right handed circular states that experience the sample in forward and backward directions.Phase difference between two interferometric signals yields the optical rotation. Results from glucose and fructosesamples are presented for validation.

Depth of focus extension by filtering in the frequencydomain in laser frequency-shifted feedback imaging

Yueyue Lu, Kaiyi Zhu, Jiyang Li, Shulian Zhang, and Yidong Tan

Doc ID: 327611 Received 09 Apr 2018; Accepted 12 Jun 2018; Posted 12 Jun 2018  View: PDF

Abstract: The depth of focus extension in optical imaging is of considerable interest. In this paper, a laser frequency-shiftedfeedback scanning imaging configuration is demonstrated whose depth of focus is greatly extended throughnumerical filtering. The transmission characteristics of the system are studied. The original image is acquiredthrough a two-dimensional scanning point by point with the target placed on a defocused plane. Filtered in thefrequency domain, images on any oriented plane can be refocused. The superior performances are presented byimaging a three-dimensional target and the process of the gradually refocusing is demonstrated. To obtain themaximum extension in the depth of defocus, a series of numerical experiments have been carried out, whichreveals its depth of focus is capable of being extended to fourth the length of the objective focus length. Thefabulous performances can motivate three-dimensional surface profile measurement.

Fiber coupling efficiency of Gaussian-Schell modelbeams in an ocean to fiber link with a Zernike tiltcorrection

Beibei Hu, Lin Yu, and YiXin Zhang

Doc ID: 328750 Received 18 Apr 2018; Accepted 12 Jun 2018; Posted 12 Jun 2018  View: PDF

Abstract: The fiber coupling efficiency of Gaussian-Schell model beams propagating through the oceanic turbulenceof the Zernike tilt correction is studied. We derive the expression of the Zernike tilt-corrected wavestructure function. The numerical analysis reveals that a higher correction factor and spatial coherenceof laser beam increase the fiber coupling efficiency of the link. Our work shows that the Zernike tiltcorrection increment under a strong turbulence condition is stronger than the weak turbulence condition,and the salinity fluctuation has a greater impact on the Zernike tilt correction increment than temperaturefluctuation does.

Directional Second Harmonic Generation Controlled bySub-wavelength Facets of an Organic Mesowire

Deepak Sharma, Shailendra Chaubey, Adarsh Vasista, Jesil Karumancheril, Ravi Tripathi, Alexandre Bouhelier, and G.V. Pavan Kumar

Doc ID: 330553 Received 27 Apr 2018; Accepted 11 Jun 2018; Posted 12 Jun 2018  View: PDF

Abstract: Directional harmonic generation is an important property characterizing the ability of nonlinear opticalantennas to diffuse the signal in well-defined region of space. Herein, we show how sub-wavelengthfacets of an organic molecular mesowire crystal can be utilized to systematically vary the directionalityof second harmonic generation (SHG) in the forward scattering geometry. We demonstrate this capabilityon crystalline diamonoanthraquinone (DAAQ) mesowires with subwavelength facets. We observed thatthe radial angles of the SHG emission can be tuned over a range of 130 degrees. This angular variationarises due to spatially distributed nonlinear dipoles in the focal volume of the excitation as well as thegeometrical cross-section and facet orientation of the mesowire. Numerical simulations of the near-fieldexcitation profile corroborate the role of the mesowire geometry in localizing the electric field. In additionto directional SHG from the mesowire, we experimentally observe optical waveguiding of the nonlineartwo-photon excited fluorescence (TPEF). Interestingly, we observed that for a given pump excitation, theTPEF signal is isotropic and delocalized, whereas the SHG emission is directional and localized at thelocation of excitation. All the observed effects have direct implications not only in active nonlinear opticalantennas, but also in nonlinear signal processing.

The influence of transversely inhomogeneouspseudo-thermal light source on lensless ghost imaging

Bowen Wang, Xiquan Fu, Xiaonan Zhu, Xiaohui Shi, and Suqin Nan

Doc ID: 325537 Received 06 Mar 2018; Accepted 11 Jun 2018; Posted 12 Jun 2018  View: PDF

Abstract: The influence of transversely inhomogeneous pseudo-thermal light source on lensless ghost imaging isinvestigated theoretically and experimentally. Based on classical optical theory, a model of lensless ghostimaging with the inside inclined light source is analyzed. We use the optical path difference betweendifferent transverse positions of the light beam to estimate the degree of inhomogeneity. The resultsindicate that the transversely inhomogeneous light source decreases the visibility and the signal-to-noiseratio of the reconstructed image. Finally, we implement the experiments to verify our results by using theinclined ground glass.

Improved light collection in ICOS cells using non-axially symmetric optics

Benjamin Clouser, Laszlo Sarkozy, and Elisabeth Moyer

Doc ID: 326325 Received 22 Mar 2018; Accepted 11 Jun 2018; Posted 12 Jun 2018  View: PDF

Abstract: High effective path lengths and stable optical configuration make Integrated Cavity Output Spectroscopy (ICOS) a useful spectroscopic technique for measuring trace gases. However, the skewed nature of the output ray geometry of ICOS cavities makes it difficult to collect the already weak cavity output onto small detectors. We derive the constraining effect of skewness in ICOS cavities with Herriott alignments, which limits light collection efficiency for compact instrument designs, and show how this constraint can be overcome by addition of a non-axially-symmetric optical component. We demonstrate the efficacy of this approach with the ICOS-based Chicago Water Isotope Spectrometer (ChiWIS), which incorporates a skew-correcting optical element consisting of eight ZnSe wedges, and show that it increases collection efficiency by approximately a factor of six.

Optoelectronic application of graphene nanoribbonfor mid-Infrared band-pass filtering

Alireza Tavousi, Mohammad Ali Mansouri-Birjandi, and Morteza Janfaza

Doc ID: 327367 Received 30 Mar 2018; Accepted 11 Jun 2018; Posted 12 Jun 2018  View: PDF

Abstract: In this study, an ultra-compact optoelectronic band-pass filter is proposed. A single piece of Graphene-nanoribbon(GNR) is placed between two input-output GNRs to form a Fabry-Perot-like cavity. The GNR, as mid-infrared surfacewaveguide, enhances the compatibility with complementary metal oxide-semiconductor processing technologies.The transmission characteristics of band-pass filter are tuned by the modulation of surface charge carrier densitysimply through changing the bias voltage applied on the GNR cavity and thus a tunable filter at room temperatureis achieved. It is found that increasing the gate voltage and the silica substrate thickness or middle GNR width alterthe max peak of transmission spectra of the filter toward smaller wavelengths. In contrast, increasing the middleGNR length redshifts max peak of filter toward longer wavelengths. The finite different time domain (FDTD) inhousecode has been employed to verify the designs.

Short-range azimuth measurement method basedon the adaptive filtering mechanism using laser andmagnetic

lin gan and He Zhang

Doc ID: 324936 Received 27 Feb 2018; Accepted 10 Jun 2018; Posted 12 Jun 2018  View: PDF

Abstract: In order to accurately measure the target position in the short range, this paper presents a measurementmethod based on the laser and magnetism composite (L-M) mechanism. A single-beam pulsed laser is used tomeasure the target distance dynamically. The magnetic sensor is used to acquire the scanning period signaland the azimuth information is calculated by the L-M signal. The variable step size least mean square (VSS-LMS)algorithm with step memory effect is designed to reduce the interference. The numerical simulation andexperimental results show that the method of azimuth measurement has good measurement accuracy andanti-interference. In addition, this short-range azimuth measurement has great potential in small movingbodies.

Sensitivity study on the effect of the optical andphysical properties of coated spherical particles onlinear polarization in clear to semi-turbid waters

Masada Tzabari, Carynelisa Haspel, David Iluz, and amit lerner

Doc ID: 327013 Received 28 Mar 2018; Accepted 10 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: The influence of internal inhomogeneities within hydrosol particles on the polarization characteristics of light isinvestigated by combining an accurate coated sphere (core-shell) single scattering model with a radiative transfermodel that employs Stokes formalism and considers refraction of direct solar radiation at the air-water interfacefollowed by single scattering. A Junge particle size distribution is assumed. Variations in what we call the "linearpolarization phase function" (LPPF; the degree of linear polarization as a function of scattering angle and the Evectororientation as a function of scattering angle) are examined as a function of variations in the characteristicsof the hydrosol particles. An extensive sensitivity study on the influence of variations in the real and imaginaryparts of the refractive index of both the core and shell of the hydrosol particles and on the influences of variationsin the ratio between the core radius and shell radius is conducted, varying the values of these parameters over theentire parameter space documented in the literature for actual hydrosol particles. In addition, calculations areconducted for specific parameter combinations in order to demonstrate the influence of some of the mostimportant groups of hydrosols, namely phytoplankton, gas bubbles, carbonaceous hydrosols, and mineralhydrosols, on the polarization field under water. Variations as a function of solar zenith angle are also investigated.Due to the assumption of single scattering, the results presented are relevant to conditions of low wind speed and alow scattering optical depth and/or low single scattering albedo within the water body (clear to semi-turbid watersat shallow geometric depths and/or moderate to strong absorption within the water body) outside of Snell’swindow. Possible implications for aquatic animal polarization vision, for light polarization pollution, and forremote sensing are discussed.

Life Cycle Analysis of Electrically Actuated SMA Springusing Talbot Interferometry

Reena Disawal, Tameshwer Nath, Shashi Prakash, and Palani Anand Iyamperumal

Doc ID: 327516 Received 03 Apr 2018; Accepted 10 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: Electrically actuated shape memory alloys find wide applications in engineering and science. Suchmaterials are known to retain/remember their state. In stressed/deformed state, when activated byapplication of suitable excitation mechanism, such as use of heat or potential, they return to their originalunstressed state. To test their reliability, it is a standard procedure to undertake the life cycle analysis. Inthis paper, life cycle analysis of shape memory alloy (SMA) spring using Talbot interferometric techniqueis reported. The life cycle of the SMA spring is analyzed in terms of the displacement drift, which sets inbecause of the functional fatigue generated due to its repeated use. Collimated light from He-Ne lasertransmitted through beam splitter is converged through a focusing lens onto a plane mirror attached tothe spring. Back-reflected light from the mirror is incident on a set of two Ronchi gratings separated byTalbot distance forming a moiré pattern. Resulting interferograms are analysed using fringe rotationmechanism. The angle of orientation is a function of displacement drift. There is deterioration in the SMAproperty because of repeated cycles, and spring loses its property to return back to its original unstretchedposition. The values of displacement drifts generated after 1, 1000, 2000, 3000, 4000, 5000 suchcycles measured using Talbot interferometer are 0, 0.875 mm, 1.275 mm, 1.459 mm, 1.720 mm and 1.859mm respectively. It is observed that, SMA effect deteriorates as the number of stretching/contractioncycles increase. The uncertainty analysis is also reported. The expanded uncertainty was determined tobe 201.61 μm.

Analysis of 90 days operation of the gyroscopeGINGERINO

Jacopo Belfi, Nicolo' Beverini, Giorgio Carelli, Angela Di Virgilio, Umberto Giacomelli, Enrico Maccioni, Andreino Simonelli, Fabio Stefani, and Giuseppe Terreni

Doc ID: 327742 Received 10 Apr 2018; Accepted 10 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: GINGER (Gyroscopes IN GEneral Relativity) is aproposed experiment with the aim of measuring ina ground laboratory the gravito-electric and gravitomagneticeffects foreseen by General Relativitythrough an array of ring laser gyroscopes. GINGERINOis a square ring-laser prototype, which hasbeen built to investigate the level of noise inside theGran Sasso underground laboratory. GINGERINOhas shown the advantage of the underground location.Now it provides suitable data for geophysics and seismology.Since May 2017 it is continuously acquiringdata. The analysis of the first 90 days shows that theduty cycle is higher than 95%, and the quantum shotnoise limit is of the order of 10􀀀10(rad/s)/pHz. It islocated in a seismically active area, and it recorded partof the of central Italy earthquakes. Its high sensitivityin the frequency band of fraction of Hz makes itsuitable for seismology studies. The main purposeof the present analysis is to investigate the long termresponse of the apparatus. Simple and fast routines tosuppress the disturbances coming from the laser havebeen developed. The Allan deviation of the raw datareaches some 10􀀀6 after about 106s of integration time,while the processed data shows an improvement ofone order of magnitude. Disturbances at the daily timescale are present in the processed data and the expectedsignal induced by polar motion and solid Earth tide iscovered by those disturbances.

Development and application of a low cost smartphone-based turbidimeter using scattered light

Abdullah Bayram, Eyyup Yalcin, Serafettin DEMIC, Orhan Gunduz, and Mehmet Solmaz

Doc ID: 322501 Received 22 Feb 2018; Accepted 10 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: We demonstrate the development and application of a low-cost smartphone turbidimeter system to be used on water samples collected from natural resources. The proposed system depends on the spectroscopic measurements of both forward and side scattered light. A custom-designed cradle was fabricated using 3D printing, and plastic optical fibers were used to couple light from smartphone’s built-in flash and transmit the collected scattered light to the camera sensor. The performance parameters of the smartphone turbidimeter were investigated, compared to commercial systems and the lowest limit of detection was found to be 5.58 NTU for forward scattered detection. The results obtained in the proposed scattered light based spectroscopic turbidimeter and the practicality achieved by this extremely low-cost device will have a great impact on water science and technology.

Partial least squares regression calculation for quantitative analysis of metals submerged in water measured using laser-induced breakdown spectroscopy

Tomoko Takahashi, Blair Thornton, Takumi Sato, Toshihiko Ohki, Koichi Ohki, and Tetsuo Sakka

Doc ID: 324764 Received 02 Mar 2018; Accepted 10 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: Effects of different parameters regarding partial least squares (PLS) regression analysis are investigated for quantitative analysis of water-submerged brass samples. The concentrations of Cu and Zn in various brass alloys were quantified using PLS and the performances after different signal processing steps (normalisation, smoothing and background subtraction) and database segmentation by excitation temperature are compared. In addition, the effects of averaging numbers on the results are examined. From the results, normalisation was found to be the most effective among three established signal processing methods. The effects of both peak and background fluctuations seen in the signals are reduced by normalisation. It was found that temperature segmentation of database in an appropriate range, which should be high enough for reliable peak detection, can further improve the accuracy of PLS calculations. The proposed method is applicable in real time, and can potentially be used for automated fast and accurate measurements of solids at oceanic pressures.

1.6 MHz scanning rate direct absorption temperaturemeasurements using a single vertical cavity surfaceemitting laser diode

Benjamin Kaebe, Nicholas Robins, Toby Boyson, Sean O'Byrne, and Harald Kleine

Doc ID: 324921 Received 27 Feb 2018; Accepted 10 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: This paper presents 1.6MHz scan rate, non-intrusive, time-resolved temperature measurements of anormal shock reflection from a plane end wall within a shock tube. A vertical-cavity surface-emitting laser(VCSEL) was used to conduct tunable diode laser absorption spectroscopy (TDLAS) with water vapor asthe probe species. The results are compared with analytical predictions. Temperatures measured withthis technique agree within a single-scan standard deviation of 33K with calculated temperatures at aVCSEL modulation frequency of 800 kHz and is sufficiently rapid to be used to investigate highly transientshock wave interaction processes.

One Symbol Training Receiver for SPAD-basedUnderwater VLC System

Chao Wang, Hong-Yi Yu, Zhu Yi-Jun, Tao Wang, and Ya-Wei Ji

Doc ID: 325017 Received 27 Feb 2018; Accepted 10 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: For the long distance single photon avalanche diode (SPAD)-based underwater visible light communication(UVLC) system, the multiple-symbol union detection scheme is presented. However, an error floorcurve of bit-to-error ratio (BER) occurs and can not vanish even though the transmitted power approachesinfinity. In this paper, to solve the problems of error floor and channel estimation in the long distanceSPAD-based UVLC system, we propose the one training symbol maximum likelihood (ML) detectionreceiver. Firstly, we add one training symbol in the head of each frame to eliminate the error floor andensure the reliable blind estimation of the long distance UVLC channel. Meanwhile, the training ML detection(TMLD) receiver is developed. And then, to improve the system performance, a training modified(TM) quasi-maximum-likelihood (quasi-ML) receiver with Anscombe root transformation is proposed.Compared to the traditional mean detection scheme of the SPAD receiver, the simulation results showthat the proposed TM quasi-ML and TMLD schemes significantly improve the error-rate performance.

A Regression-Based Technique for Improved OpticalRangefinding using Tunable Focus Lenses

Syed Reza, Tariq Khwaja, Mohsin Ali Mazhar, and Haris Khan Niazi

Doc ID: 325183 Received 01 Mar 2018; Accepted 10 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: In this paper, we present a novel method of target range estimation by tuning the spot size of a Gaussian Beam atthe plane of a reflective target. The beam spot size tuning is achieved through the use of a Tunable Focus Lens(TFL). Using a carefully aligned sensor assembly, diameter of the reflected beam is recorded at the plane of animaging detector for different TFL focal length settings. This dataset is then used to estimate the distance of thetarget from the TFL. The proposed rangefinder is compact and requires minimal post-data-acquisition signalprocessing resulting in a fast response time compared to other spatial signal processing-based sensor designs. Theestimation of target distance through a multiple data-point measurement dataset also ensures that the proposedmethod is robust to errors associated with obtaining range estimates from a single measurement data-point.Experimental results demonstrate an excellent agreement with theory. With our proposed estimation method, weshow a significant improvement in the measurement dynamic range of the sensor as well as its resolutioncompared to similar sensing schemes in prior art. We also experimentally demonstrate the possibility to extendthe measurement dynamic range by incorporating a bias lens of a fixed focal length with the sensor module. Theproposed sensor module is electronically-controlled and consequently can be fully automated and compactlypackaged with the use of commercially-available miniature optical components.

Dynamic Mach-Zehnder interferometer based on the lateral displacement of a point source array

Yu Ding, Lei Chen, Lu Kong, Ying Yang, Zhiyuan Liu, Qinyuan Sun, and Donghui Zheng

Doc ID: 325703 Received 09 Mar 2018; Accepted 10 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: A dynamic Mach-Zehnder interferometer based on lateral displacement of a point source array is proposed. The point source array is generated by a point source and a phase grating, where four point sources are of identical intensity. The lateral displacement of each point source can be adjusted to introduce π/2 phase step in the interferograms. With a specially designed lens array in the spatial split imaging system, four separated and clear imaging interferograms can be captured in a single shot. Using four-bucket algorithm, the phase distribution can be retrieved exactly, thereby realizing dynamic measurement. The experimental results show the feasibility and high precision of the dynamic Mach-Zehnder interferometer.

Implementation of nearly arbitraryspatially-varying polarization transformations: anon-diffractive and non-interferometricapproach using spatial light modulators

Matthew Runyon, Codey Nacke, Alicia Sit, Marissa Granados Báez, Lambert Giner, and Jeff Lundeen

Doc ID: 328186 Received 24 Apr 2018; Accepted 09 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: A fast and automated scheme for general polarization transformations holds greatvalue in adaptive optics, quantum information, and virtually all applications involving light-matterand light-light interactions. We present an experiment that uses a liquid crystal on silicon spatiallight modulator (LCOS-SLM) to perform polarization transformations on a light field. Weexperimentally demonstrate the point-by-point conversion of uniformly polarized light fieldsacross the wave front to realize arbitrary, spatially varying polarization states. Additionally, wedemonstrate that a light field with an arbitrary spatially varying polarization can be transformedto a spatially invariant (i.e., uniform) polarization.

Strain transferring mechanism analysis of the surface-bonded FBG sensor

Minfu Liang, Ningning Chen, Xinqiu Fang, and Gang Wu

Doc ID: 326718 Received 27 Mar 2018; Accepted 09 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: The mechanical analysis model of surface-bonded Fiber Bragg Grating (FBG) shear strain transfer is established inconsideration of the linear visco-elastic effect of the adhesive layer, which is simplified as a standard linear solidmodel. And the strain transfer relation is acquired and validated by anchor bar uniaxial tension experiments.There is good correspondence between calculated values and experimental results. Finally, the influences of shearmodulus, length and width of the adhesive layer and thickness of the interlayer on the instantaneous and quasistaticstrain transfer are analyzed by numerical simulation.

Optical tweezers for trapping in a microfluidic environment.

Ronald Kampmann, Stefan Sinzinger, and Jan Korvink

Doc ID: 330775 Received 01 May 2018; Accepted 09 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: Optical tweezers use the force from a light beam to implement a precise gripping tool. Based purelyon an optical principle, it works without any bodily contact with the object. In this paper we describean optical tweezers which targets an application within the framework of nuclear magnetic resonance(NMR) spectroscopy of small objects, which are embedded inside a microfluidic channel that will be integratedin a micro-NMR detector. In the project’s final stages, the whole system will be installed within thewide bore of a superconducting magnet. The aim is to precisely maintain the position of the object to bemeasured, without the use of susceptibility disturbing materials or geometries. In this contribution wefocus on the design and construction of the tweezers. For the optical force simulation of the system weused a geometrical optics approach, which we combined with a ray fan description of the output beamof an optical system. By embedding both techniques within an iterative design process, we were able todesign efficient optical tweezers that met the numerous constraints. Based on details of the constrainsand requirements given by the application, different system concepts were derived and studied. Next,a highly adapted and efficient optical trapping system was designed and manufactured. After the componentswere characterized using vertical scanning interferometry, the system was assembled to achievea monolithic optical component. The proper function of the optical tweezers was successfully tested byoptical trapping of fused silica particles.

Integrated Research of Multi-wavelengthMethod in Anisotropic Scattering Flame onSoot Temperature and Radiative CoefficientReconstruction

mingjie li, Ke Sun, and Zhu He

Doc ID: 326890 Received 16 Apr 2018; Accepted 09 Jun 2018; Posted 13 Jun 2018  View: PDF

Abstract: At present, the studies of scattering flame problems combined withmulti-wavelength reconstruction technology are rather limited. In this paper, amulti-wavelength method combined with a CSM-DOM forward method is developed for thesimultaneous reconstruction of temperature and inhomogeneous radiative coefficient of anaxisymmetric laminar ethylene diffusion flame. The scattering source term in the radiativetransfer equation (RTE) is solved by the forward solution method based on the discreteordinates method (DOM), which coupled a spatial scheme of collocation spectral method(CSM) and the spherical rings arithmetic progression quadrature (SRAPn). The Tikhonovregularized method is employed to overcome the ill-posed matrix to obtain the globalradiative source term. The boundary radiation intensity is input into the algorithm as a knownvalue for inversion of temperature, absorption coefficient and scattering coefficient. Theretrieval results demonstrate that the temperature and the radiation parameters of thescattering flame can be well reconstructed for the flame with axisymmetric distribution, evenfor the flame with noisy data. In addition, the scattering coefficient are more difficult to berebuilt than temperature. The inversion accuracy does not deteriorate with a slight increase innoise. Besides, the addition of scattering terms to the proposed algorithm can improve theaccuracy in reconstructing the radiation parameters. The developed method in this paperwould be a useful development for multispectral algorithms, which could be used in laterexperiments based on hyperspectral techniques.

Multiple wavelength-selecting and beamsplittingphotonic crystal functional devicebased on the mode coupling between thecentral microcavity and the adjacentwaveguides

Xing Liu, Chao Wu, shuai feng, xiao Chen, Chuanbo Li, and Yiquan Wang

Doc ID: 328770 Received 18 Apr 2018; Accepted 08 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: The beam-splitting and wavelength-selecting characteristics of the twodimensionalsquare-lattice photonic crystal with a rectangular microcavity and adjacent W1-typed waveguides are studied. Based on the abundant defective modes with differentsymmetries supported by the central microcavity, a multiple-functional device with theabilities of beam splitting and wavelength-selecting is achieved. Through altering theconnecting location between the input/output channels and the central microcavity, theproposed device can achieve three kinds of functions at different wavelengths within an ultrasmallwavelength band about 3 nm, a maximum transmittance of 0.57 and signal to noiseratio of 149 are achieved for the one-channel selecting, 0.31 and 146 for two-channelsplitting, and a maximum transmittance of 0.24 for the three-channel light beam sharing. Thecorresponding forward directions of light propagation along the output channels can also beflexibly adjusted.

Systematic investigation of methods for multiple freeform optimization in multi-lens imaging systems

Chang Liu and Herbert Gross

Doc ID: 327740 Received 10 Apr 2018; Accepted 07 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: With the development in freeform technology, it has now become more and more feasible to use freeform surfaces in real system designs. While the freeform surfaces helping optical designers achieve more and more challenging system features, the methods for multiple freeform implementations are still underdeveloped. We therefore investigate strategies to use freeform surfaces properly in imaging optical systems with one Scheimpflug system and one lithographic system. Based on the studies of the influences of the freeform normalization radius, freeform order and system eccentricity, the methods of determining the optimal location for implementing one freeform surface are discussed. Different optimization strategies to optimize two freeform surfaces are discussed to compare their resulting influences on the system performance. On top of that, ways to implement more than one freeform surface in the optical system is also investigated. In the end, a workflow is presented as guidance for implementing multiple freeform surfaces with respect to system aberration constitutions.

Optimized Pupil-Plane Phase Masks for High ContrastImaging

Jacob Wirth, Abbie Watnik, and Grover Swartzlander

Doc ID: 326086 Received 15 Mar 2018; Accepted 07 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: Adifferential evolution algorithm (DEA) is shown to improve the design of phase-only pupil plane masksfor imaging in the presence of a high intensity point source. Strehl and suppression ratio metrics forvarious phase basis functions were experimentally and numerically calculated. Experiments performedwith a spatial light modulator demonstrated 100 times suppression of the peak intensity. The Strehl ratiowas found to be higher for the DEA masks compared to the individual phase basis function.

Development of a prototype Active Optics system forfuture Space Telescopes

Martin Devaney, Fiona Kenny, Alexander Goncharov, Matthias Goy, and Claudia Reinlein

Doc ID: 327560 Received 03 Apr 2018; Accepted 07 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: It is envisaged that future large Space Telescopes will be light-weight and employ active optics to maintainoptical quality throughout the mission lifetime. We have proposed a 4m, two-mirror space telescopewith an active optics system based on re-imaging the telescope primary mirror onto a small active mirror(110mm optical pupil). Using Zemax we demonstrate the feasibility of using this mirror to correct loworderZernike aberrations, and that the aberration is well corrected across the 2.5 arcminute field of thetelescope, operating at 0.55 mm. We describe the modelling carried out to develop the active mirror design.Using end-to-end modelling, a 25-actuator mirror with polar actuator geometry, and a ratio of mechanicalto optical pupil diameter of 2 has been chosen. A single-actuator prototype has been manufactured andused to test stroke, linearity and hysteresis. Finally, we describe the design of a laboratory breadboardwhich will image phase screens onto an exact replica of the space active mirror, and show the results ofmeasuring the phase screen accuracy..

Optical Constants and Electrochromic Characteristics of MxWO3 Bronzes

Zahid Hussain

Doc ID: 327984 Received 10 Apr 2018; Accepted 06 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: AbstractConcentration (x) dependent ellipsometric data on three tungsten bronzes (HxWO3, LixWO3, NaxWO3) are investigated to examine systematically about their electrochromic characteristics. Maximum decrease in n and maximum increase in k, are found as the limits of electrochromic effects. Differences in the optical constants of these three tungsten bronzes, are perhaps due to different impurity scattering mechanism associated with their individual unit cell configurations. Optical densities and the complex dielectric loss functions (-1/of tungsten bronzes have been calculated to obtain knowledge about their local configurations. Oscillator strengths, dipole strengths, and the degrees of delocalization of the polaronic wave functions are calculated and are found to be very low, giving the convincing argument that there is no indication of Drude free electron behaviour in these bronzes, at least, in the investigated concentration range.

Reflective EUVL Tool Design with GeneralizedGaussian Constant Mathematics

Li-Jen Hsiao and Hoang Yan Lin

Doc ID: 326001 Received 10 Apr 2018; Accepted 06 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: This study aims to develop a systematic design procedure for extreme ultraviolet lithography tools.Through analysis using Generalized Gaussian Constants, relationships between optical properties andrequirements can be obtained, and can be used to help ensuring that optical system properties requiredfor the tool are upheld during the design process. As verification of the design method, an eight mirror0.4 NA tool design has been demonstrated.

Superior signal persistence of circularly polarized lightin polydisperse, real-world fog environments

J D Van Der Laan, Jeremy Wright, Shanalyn Kemme, and D Scrymgeour

Doc ID: 327015 Received 27 Mar 2018; Accepted 06 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: We present simulation results quantitatively showing circularly polarized light persists in transmissionthrough several real-world and model fog environments better than linearly polarized light over broadwavelength ranges from the visible through the infrared. We present results for polydisperse particle distributionsfrom realistic and measured fog environments comparing the polarization persistence of linearand circular polarization. Using a polarization-tracking Monte Carlo program we simulate polarized lightpropagation through four MODTRAN fog models (moderate and heavy radiation fog, and moderate andheavy advection fog) and four real-world measured fog particle distributions (Garland measured radiationand advection fogs, Kunkel measured advection fog, and SNL’s fog facility’s fog). Simulations wereperformed for each fog environment with wavelengths ranging from 0.4 to 12 mm for increasing opticalthicknesses of 5, 10, and 15 (increasing fog density or sensing range). Circular polarization persists superiorlyfor all optical wavelength bands from the visible to the long-wave infrared, in nearly all fog typesfor all optical thicknesses. Throughout our analysis we show that if even a small percentage of a fog’sparticle size distribution is made up of large particles, those particles dominate the scattering process. Innearly all real-world fog situations, these large particles and their dominant scattering characteristics arepresent. Larger particles are predominantly forward-scattering and contribute to circular polarization’spersistence superiority over broad wavelength ranges and optical thicknesses/range. Circularly polarizedlight can transmit over 30 percent more signal in its intended state compared to linearly polarized lightthrough real-world fog environments. This work broadens the understanding of how circular polarizationpersists through natural fog particle distributions with natural variations in mode particle radius andsingle or bi-modal characteristics.

Peculiarities of acousto-optic interaction in biaxialcrystal of alpha-iodic acid

Maxim Kupreychik and Vladimir Balakshy

Doc ID: 321136 Received 31 Jan 2018; Accepted 06 Jun 2018; Posted 06 Jun 2018  View: PDF

Abstract: By the example of an alpha-iodic acid crystal we demonstrate unusual peculiarities of acousto-opticinteraction in gyrotropic biaxial crystals. The basic attention is given to the most interesting cases ofanisotropic diffraction in geometry, when the wave vector of ultrasound is directed almost orthogonally toone of the optical axes, and the directions of incident and diffracted light beams are close to the optical axis. Itis shown that in this case a peculiar character of optical anisotropy originates unique variants of acoustoopticinteraction which are fundamentally impossible in uniaxial crystals. A wide variety of frequencydependences of the Bragg angles allows choosing optimal configurations of crystal cuts for each specificacousto-optic device. The influence of the effect of optical activity on diffraction characteristics is examinedas well.

NARX Neural Network Model for Strong ResolutionImprovement in Distributed Temperature Sensor

Luis Silva, Jorge Samatelo, Marcelo Segatto, João Bazzo, Jean Carlos Cardozo da Silva, Cicero Martelli, and Maria Pontes

Doc ID: 325182 Received 01 Mar 2018; Accepted 05 Jun 2018; Posted 06 Jun 2018  View: PDF

Abstract: This paper proposes an approach to process the response of a Distributed Temperature Sensor using aNonlinear Autoregressive with External Input Neural Network. The developed model is composed ofthree steps: extraction of characteristics, regression and reconstruction of the signal. Such an approach isrobust since it does not require the knowledge of the characteristics of the signal, it has a reduction of datato be processed, resulting a low processing time, besides the simultaneous improvement of spatial resolutionand temperature. We obtain total correction of the temperature resolution and spatial resolution of5 cm of the sensor.

Twin-image reduction method using a diffuser forphase imaging in-line digital holography

Kazusa Oe and Takanori Nomura

Doc ID: 326053 Received 14 Mar 2018; Accepted 05 Jun 2018; Posted 06 Jun 2018  View: PDF

Abstract: Phase imaging by digital holography is widely used. In-line optical setup is preferable for a practicaluse. A twin image, however, is a serious obstacle to achievement of high-quality phase imaging in in-linedigital holography. For in-line digital holography, a time division phase-shifting method or a wave splittingphase-shifting method is used to eliminate the twin image. The former requires multiple exposuresand the latter requires specially designed optical elements. To solve these problems, a twin image reductionmethod using a diffuser is proposed. In the proposed method, recording a digital hologram using adiffuser and signal processing enable to reduce the twin image on a reconstructed plane. A preliminaryexperimental result confirms the feasibility of the proposed method.

Eavesdropping of display devices by measurement ofpolarized reflected light

Yitian Ding, Ronan Kerviche, Amit Ashok, and Stanley Pau

Doc ID: 326315 Received 20 Mar 2018; Accepted 05 Jun 2018; Posted 06 Jun 2018  View: PDF

Abstract: Display devices, or displays, such as those utilized extensively in cell phones, computer monitors, televisions,instrument panels, and electronic signs are polarized light sources. Most displays are designed for direct viewingby human eyes, but polarization imaging of reflected light from a display can also provide valuable information.These indirect (reflected/scattered) photons, which are often not in direct field-of-view and mixed with photonsfrom the ambient light, can be extracted to infer information about the content on the display devices. In this work,we apply Stokes algebra and Mueller calculus with the edge overlap technique to the problem of extracting indirectphotons reflected/scattered from displays. Our method applies to recovering information from linearly andelliptically polarized displays that are reflected by transmissive surfaces, such as glass, and semi-diffuse opaquesurfaces, such as marble tiles and wood furniture. The technique can further be improved by applying Wienerfiltering.

Mirror based flexible one-step calibration method oflight-sectioning system for surface topograhpy

Cong Liu, Xiaopeng Liu, zhihong Xu, Xiaoyuan He, and Xin Kang

Doc ID: 327160 Received 28 Mar 2018; Accepted 05 Jun 2018; Posted 06 Jun 2018  View: PDF

Abstract: A flexible, easy-to-implement one-step calibration method of the light-sectioning system is proposed forsurface topography using a mirror adapter. The calibration method employs an arbitrary non-planar objectwith feature points as a target. With the assistance of the mirror adapter, the real and the reflectedimages of calibration are spatially separated, and captured by a camera. It is developed a direct calculation(DC) method and a virtual camera (VC) method to optimize the full parameters of the system. TheDC method estimates the relative rotation and translation, respectively, and the VC method regards thetwo images as captured by two cameras in a physical sense through image flipping. The parameters ofthe laser plane can be solved accordingly. Numerical simulation is performed to analyze the precision ofthese two methods. A three-dimensional (3D) toy and a mechanical element are measured to verify thevalidity in translation experiments.

Dispersion-engineered microstructured optical fiber formid-infrared supercontinuum generation

Hamed Saghaei

Doc ID: 327652 Received 10 Apr 2018; Accepted 05 Jun 2018; Posted 06 Jun 2018  View: PDF

Abstract: Due to the large scientific and technical interest in the mid-infrared (MIR) spectral region, and the limitationsof MIR light sources, we focus on the generation of a broad supercontinuum inside a short pieceof As2Se3 microstructured optical fiber (MOF) with a square lattice. This is accomplished by filling theholes in the innermost ring of the proposed MOF with Ge33As12Se55 to produce ultra-flat and near-zerodispersion. Simulations reveal that, by launching 100 fs input pulses centered at l0 = 6.2 μm with a peakpower of 2 kW into the MOF, an optical spectrum as wide as 9.5 μm will be achieved. This spectrum is asuitable source for MIR applications such as spectroscopy, food quality control, and gas sensing.

790 W incoherent beam combination of Tm-dopedfiber laser at 1941 nm using a 3×1 signal combiner

Weichao Yao, Chongfeng Shen, Zhenhua Shao, jianlei wang, Fei Wang, Yongguang Zhao, and Deyuan SHEN

Doc ID: 328484 Received 16 Apr 2018; Accepted 05 Jun 2018; Posted 06 Jun 2018  View: PDF

Abstract: In this paper, we report on high power incoherent beam combination of three Tm-doped fiber amplifiers at 1941nm based on a 3×1 signal combiner. An output power of 790 W is achieved from the signal combiner with a slopeefficiency of 52.2% with respect to the launched pump power and a beam quality factor M2 of 2.7. The beam qualityfactor is close to the theoretical limit of the 3×1 fiber combiner. The parameters of amplifier are optimized toincrease the laser efficiency. Our analyses show that this structure is sufficient to support kW level output powerwhile maintaining the high beam quality.

Precision measurements of optically thick alkali metal number density within a hybrid alkali metal cell

wei quan, kesheng shen, Yueyang Zhai, xulin wang, Liwei Jiang, Wenfeng Fan, feng liu, jie qin, and shuangai wan

Doc ID: 328935 Received 20 Apr 2018; Accepted 05 Jun 2018; Posted 06 Jun 2018  View: PDF

Abstract: The number density of alkali metal vapor and their ratio within hybrid cells are of great significance for the optimal rotation sensitivity of alkali metal-noble gas co-magnetometers. To measure the number density of optically thick Rb vapor accurately within a hybrid cell containing optically thin K vapor and optically thick Rb vapor, a novel method combining alkali metal absorption spectroscopy and Raoult's Law is proposed in this paper. The relative error between experimental results and theoretically predicted results is within ±%5 from 365 K to 450 K and the measurement accuracy is improved more than 10 times compared to previous study. This novel method could be applied to check the number density ratio of alkali metal within hybrid cells more precisely.

Design of high numerical aperture extreme ultravioletlithography illumination system

Jiahua Jiang, Yanqiu Li, Shihuan Shen, and Shanshan Mao

Doc ID: 330043 Received 23 Apr 2018; Accepted 05 Jun 2018; Posted 06 Jun 2018  View: PDF

Abstract: High numerical aperture (NA) anamorphic imaging projection objective is the industrial choice forextreme ultraviolet (EUV) lithography under advanced technology node. The illumination system hasto match the elliptical entrance pupil of the high NA projector. In this paper, an illumination systemsuitable for the high NA anamorphic projection objective is designed. The two mirror relay system ofthe illumination system is designed by a two stage process. The first order initial configuration withspherical surfaces is calculated by a method based on matrix optics. Then after tilting and decenteringthe two spherical surfaces to eliminate obscuration, the two mirror surfaces are fitted into conic surfaces.To realise many different illumination modes, a facet mirror matching method based on combinatorialoptimization is proposed to allocate the mapping relationship between field and pupil facets under differentillumination modes. Simulation results of the system illumination uniformity show the systemcan achieve high uniformity on the reticle under different illumination modes.

Evaluation of laser frequency offset locking using anelectrical delay line

Yusuke Hisai, Kohei Ikeda, Haruki Sakagami, Tomoyuki Horikiri, Takumi Kobayashi, Kazumichi Yoshii, and Feng-Lei Hong

Doc ID: 327469 Received 10 Apr 2018; Accepted 05 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: Frequency offset locking between two Nd:YAG lasers is performed using frequency locking with an electrical delayline. The relative frequency instability of the offset locking is measured to be 3.5×10-12 for an averaging time of 1 s,which is approximately 77 times smaller than that of the free-running case. The frequency instability of thefrequency locking is compared to that of the phase locking between the two Nd:YAG lasers. Furthermore, a compactsolid-state laser is frequency-locked to an optical frequency comb with a frequency instability of 8.2×10-11 for anaveraging time of 1 s, which is improved by approximately 20 times, with respect to the free-running case. Theoffset-locking scheme using a delay line is useful for various applications including a research on quantum optics,interferometric measurements, and experiments involving laser cooling such as an optical lattice clock.

Optical detection of acoustic waves with surface plasmons

Alexandre Kolomenskii, Elizabeth Surovic, and Hans Schuessler

Doc ID: 318650 Received 10 Apr 2018; Accepted 05 Jun 2018; Posted 06 Jun 2018  View: PDF

Abstract: For broadband and sensitive detection of acoustic waves the surface plasmon resonance (SPR) can be used, which responds to variations of dielectric properties in close proximity to a metal film supporting surface plasmon waves. When an acoustic wave is incident onto a receiving plate positioned within the penetration depth of the surface plasmons, it creates displacements of the surface of the plate and thus modulates the dielectric properties, affecting SPR and the reflection of the incident light. Here we study characteristics and determine the optimal configuration of such an acousto-optical transducer with surface plasmons for efficient conversion of an acoustic signal into an optical one. We simulate the properties of this transducer and present estimates showing that it can have a large frequency bandwidth and high sensitivity.

Modelling the longitudinal intensity pattern of diffraction resistant beams in stratified media

Grazielle Vittorino and Michel Zamboni-Rached

Doc ID: 325736 Received 12 Mar 2018; Accepted 04 Jun 2018; Posted 05 Jun 2018  View: PDF

Abstract: In this paper, we study the propagation of the Frozen Wave typebeams through non-absorbing stratified media and develop atheoretical method capable to provide the desired spatially shapeddiffraction resistant beam in the last material medium. In this context, we also develop a matrix method to dealwith stratified media with large number of layers. Additionally, we undertake some discussion about minimizing reflection of the incident FW beam on the first material interface by using thin films. Our results show that itis indeed possible to obtain the control, on demand, of thelongitudinal intensity pattern of a diffraction resistant beameven after it undergoes multiple reflections and transmissions at the layerinterfaces. Remote sensing, medical and military applications, noninvasive optical measurements, etc., are some fields that can be benefited by the method here proposed.

Four wave mixing in Ar-filled hollow core band gapphotonic crystal fiber

Xingtao Zhao, jirui cheng, qiang xiong, lu hua, and guohui jiang

Doc ID: 326951 Received 10 Apr 2018; Accepted 04 Jun 2018; Posted 05 Jun 2018  View: PDF

Abstract: We conducted a nonlinear experiment using a femtosecond laser with the In order to study the four wave mixing effect and wavelength conversion in a hollow core gap photonic crystal fiberfilled with argon, we conducted an experiment using a femtosecond laser with the pulse width of 120 fs, arepetition rate of 76 MHz, tunable central wavelength from 760 nm to 980 nm. It is observed that new spectra isgenerated in both sides of the pump at some special wavelength, which can exactly satisfy the phase matching conditionsof four wave mixing. Combined experimental results with theoretical analysis, we find that the experimentalphenomenon is mainly caused by four wave mixing, and some other nonlinear phase effects such as self-phasemodulation, stimulated Raman scattering and soliton effect have also occurred in this nonlinear process.

Optofluidic lenses with horizontal-to-vertical aspectratios in the sub-unit regime

Shravani Prasad, Michelle del Rosso, Julie Vale, and Christopher Collier

Doc ID: 327660 Received 05 Apr 2018; Accepted 04 Jun 2018; Posted 05 Jun 2018  View: PDF

Abstract: Elliptical optofluidic lenses can provide tunable optical parameters in different optical planes. This tunability isachieved through modifications to the aspect ratio (AR). We present an optofluidic lens with a sub-unit AR. In ourexperimental analysis, we alter the shape of the microdroplet and observe a ten percent reduction in AR onapplying a high voltage across the microdroplet. In our theoretical analysis, we observe improved tunability offocal length, longitudinal spherical aberration, and beam cone angle in the sub-unit AR regime compared to thesuper-unit AR regime. We ultimately test and characterise the optofluidic lens in an imaging application.

Hybrid lens design for ultra-wide-angle imaging witha high Strehl ratio in a folded system

YuShan Chang, Long Hsu, and Kuang-Lung Huang

Doc ID: 328890 Received 19 Apr 2018; Accepted 04 Jun 2018; Posted 05 Jun 2018  View: PDF

Abstract: When UV-curable material is used with a spherical glass lens, it is classified as a hybrid lens which can provide a new degree offreedom in designing a lens system. This method is used to explore the optical limitation of an ultra-wide-angle imagingsystem of a folded structure, which is utilized to achieve a compact volume. The f-number and field of view of the system are2.0 and 190°, respectively. Diffraction-limited performance is achieved within a field of view of 80° with Strehl ratios greaterthan approximately 80%. Even at the maximum field of view of 190°, the Strehl ratio is nearly 75%. The lens configuration isNNPNN, where N and P denote negative and positive optical power, respectively; this configuration uses only two asphericalhybrid lens surfaces. Comparisons of different optimizations are also provided.

Surface ripples suppression in subaperture polishingwith fragment-type tool paths

Zhichao Dong and Weizhi Nai

Doc ID: 327923 Received 10 Apr 2018; Accepted 03 Jun 2018; Posted 05 Jun 2018  View: PDF

Abstract: In order to reduce the ripple-induced effect in subaperture polishing of high power laser optics, the tool paths areinvestigated and optimized in this study. Various fragment-type curves (i.e., fractal and fractal-like unicursal curves)are designed as tool paths, and most importantly, a novel algorithm for generating random fractal-like tool path isproposed in detail. Compared with scanning paths, fragment-type paths possess multi-directionality during multiplepolishing iterations, which could better smooth the surface texture and restrain the polishing-induced surfaceripples. In particular, the random fractal-like path exhibits high randomness, boundary-adaption, and step-lengtharbitrariness, which make it more flexible and powerful for iterative polishing. Experiments were conducted on aCNC machine, with conclusions that during iterative polishing (1) the repetitive usage of a single fractal path wouldaggravate surface ripples; (2) the combination of multiple fractal paths or using the random fractal-like path canrestrain surface ripples efficiently; (3) pitch pads exhibit better ripple-smoothing effect than polyurethane. Theproposed random fractal-like path exhibits good prospect for the manufacture of high power laser optics whichdemands very low surface ripples.

Effect of solvent film and zeta potential on interfacialinteractions during optical glass polishing

Liang Shangjuan, Jiao Xiang, Tan Xiaohong, and Jianqiang Zhu

Doc ID: 326344 Received 20 Mar 2018; Accepted 03 Jun 2018; Posted 05 Jun 2018  View: PDF

Abstract: The deployment of polishing slurry is one of the important research topics in the field of chemical-mechanicalpolishing. It is expected that technological breakthroughs in this process will lead to an improvement of the surfacequality of fabricated optical components. In this investigation, we added several types of electrolytes into ceriumoxide polishing slurries, and evaluated their influence on the material removal rate (MRR) and surface roughness(Sa) during K9 glass polishing. Furthermore, we investigated their influence on the zeta potential, particle sizedistribution, and suspension stability of the slurries. The results showed that the introduction of an electrolyte intothe polishing slurry not only changes the zeta potential of the ceria particles surface, but also changes the type andthickness of the deposited solvent film. The presence of a hydrophilic solvent film resulted in repulsion betweenindividual particles and between the particles and the glass surface. On the contrary, a hydrophobic solvent filmenhanced the attraction between the individual particles and between the particles and the glass surface.Moreover, thicker solvation films corresponded to a greater force. This had a great impact on the interfacialinteraction between the particles and the glass surface during the polishing process. The presence of thehydrophobic solvent film resulted in a high MRR, while the hydrophilic solvent film was associated with low Sa. Inthis paper, the interaction mechanisms of the abrasive particles and the glass interface during the polishingprocess are elucidated by considering the zeta potential and the solvent film type. In addition, a method forreducing the resulting Sa after glass polishing is proposed.

Corrected Calibration Algorithm with Fixed ConstraintRelationship and Error Compensation Technique forBinocular Vision Measurement System

Ju Huo, Guiyang Zhang, Jiashan Cui, and Ming Yang

Doc ID: 326360 Received 20 Mar 2018; Accepted 03 Jun 2018; Posted 05 Jun 2018  View: PDF

Abstract: This paper is concerned with the precise calibration algorithm and error compensation technique for a binocular visionmeasurement system. By invoking a fixed constraint relationship between the binocular cameras, these two cameras canbe preferably bounded together as one camera, which means that in each iteration only one camera needs externalparameters tuning for optimized encapsulation and the iteration time is reduced. The global optimal solutions areobtained by substituting the initial iterative solutions into the optimized iterative equations of the spatial points. Thederived improved iterative algorithm obtains the camera parameters with high precision and better-perform in noiseresistance.Moreover, the error compensation matrix is constructed to correct the relative pose of binocular cameras,upon which the solutions to error compensation matrix are solved via the unit quaternion. Consequently, the relativepose matrix is revised, allowing for further improvement in the calibration performance. Finally, simulation and practicalexperiments are demonstrated. The relevant results confirm the precision and robustness of the proposed approach.

A Novel 3D Imaging Scanner

Zhouyi Wu, Chao Han, Changhuei Yang, and Jiangtao Huangfu

Doc ID: 323028 Received 13 Feb 2018; Accepted 03 Jun 2018; Posted 05 Jun 2018  View: PDF

Abstract: This paper proposes a multi-view three-dimensional display method based on scanning imaging system,with the light-intensity characteristic recorded by an improved flatbed scanner. Within the effective scanningdepth of the imaging sensor, two transmission images are respectively and simultaneously acquiredby two linear CCD modules with different focal planes. Then the phase gradient information of thetarget can be obtained by appropriate retrieval algorithm. Further, the multi-view three-dimensional effectis presented through dynamic angles of view. Theoretical analysis of this method is discussed, andexperiments are carried out by building a scanner. The experiment results are presented with algae specimenand transparent beads. This method can be hopefully applied to present three-dimensional effect ofobjects of flat translucent multilayer structure with wide field of view.

Evolution mechanism of surface roughness during ionbeam sputtering of fused silica

Mingjin Xu, Yifan Dai, Lin Zhou, Xiaoqiang Peng, and Wenlin Liao

Doc ID: 325454 Received 09 Mar 2018; Accepted 03 Jun 2018; Posted 05 Jun 2018  View: PDF

Abstract: Ultra smooth surface with sub-nanometer roughness and low damage is great challenges for optical fabrication. Ion beam sputtering (IBS) hasobvious advantages on the improvement of surface quality and the removal of surface defects. However, surface defects with different propertiesand structures display different evolution laws during IBS process, which affects the roughness change and needs classification studies. In this paper,classification experiments are carried out to study the surface topography evolution of plastic scratches, brittle scratches and micro-particles duringIBS process. The plastic scratches and micro-particles can be removed while the brittle scratches can be passivated, so that surface defects can bereduced and surface quality can be improved. The corresponding evolution mechanisms are discussed in depth. It points out that the microtopographycharacteristics and material properties are important factors affecting the evolution of surface topography. Through the summary ofevolution laws of different surface states, the Gaussian distribution law of surface roughness is established. The evolution regularity and mechanismof surface roughness during IBS process are expounded from the perspective of microscopic morphology, which lays a foundation for ultra smoothsurface manufacturing with low damages.

Super-resolution imaging properties of cascaded microsphere lenses

Yun Deng, Songlin Yang, Yang Xia, Yurong Cao, Jianguo Wang, Fengge Wang, and Yong-Hong Ye

Doc ID: 325617 Received 09 Mar 2018; Accepted 03 Jun 2018; Posted 05 Jun 2018  View: PDF

Abstract: In this paper, the imaging properties of a cascaded microsphere lens are studied. The cascaded microsphere lens consists of two lenses. A hexagonally close-packed 960-nm-diameter array of polystyrene microspheres is used as the first lens. The second lens is a single silica microsphere with a diameter of about 5 μm. The blu-ray disc is observed by both the cascaded microsphere lens and the single silica microsphere. Studies reveal that the magnification of the cascaded microsphere lens is about 1.4 times greater than that of the single silica microsphere, while the field of view of the cascaded microsphere lens which is close to the diameter of the polystyrene microsphere is decreased. The focal position of the cascaded lens microsphere must be close to the sample in order to observe it.

Estimating Axial Resolution with Diffraction Theory

Timothee Cognard, Christopher Dainty, and Martin Devaney

Doc ID: 327360 Received 03 Apr 2018; Accepted 03 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: Depth estimation is a classic machine vision and image processing problem aiming at mapping the distancesof objects from the camera. The accuracy of this depth map depends on the axial resolutionachieved by the system, which is usually estimated using geometrical optics theory. This paper proposesa novel formula using diffraction theory. A comparison with the geometrical approach for estimating theaxial resolution is provided and results for several simulations are discussed.

Experimental study of the morphological evolution ofthe millisecond–nanosecond combined pulse laserablation of aluminum alloy

Bo-shi YUAN, Wang Di, Yuan Dong, Wei Zhang, and guang yong jin

Doc ID: 328712 Received 18 Apr 2018; Accepted 02 Jun 2018; Posted 04 Jun 2018  View: PDF

Abstract: A comparative study of the interactions of the millisecond–nanosecond combined pulse laser and millisecond pulselaser with aluminum alloy is presented. During the interaction between the laser and aluminum alloy, the couplingeffect of the nanosecond pulse laser on the molten pool, formed by the millisecond laser, is analyzed. During thenanosecond laser irradiation in the combined approach, the expansion velocity of the plasma plume reaches 600m/s, while the laser ablation depth increased by approximately 9 times. Based on experiments, the high-speedshadow imaging method, correlation of the temperature evolution characteristics, and ablation morphology areconsidered for a comprehensive analysis. The coupling effect between the millisecond–nanosecond combinedpulse laser and aluminum-alloy molten pool phase is explained.

High loop rate Adaptive Optics Flood IlluminationOphthalmoscope with structured illuminationcapability

Elena Gofas-Salas, Pedro Mece, Cyril Petit, Jessica Jarosz, Laurent Mugnier, Aurelie Montmerle Bonnefois, Kate Grieve, José-Alain Sahel, Michel Paques, and Serge Meimon

Doc ID: 328784 Received 03 May 2018; Accepted 02 Jun 2018; Posted 04 Jun 2018  View: PDF

Abstract: The design and performance of an Adaptive Optics Flood Illumination Ophthalmoscope (AO-FIO) platform,based on eye motion and dynamic aberrations experimental analysis, is described. The systemincorporates a custom-built Real Time Controler, enabling up to 70Hz loop rate without jitter, and an AOcorrectedillumination capable of projecting high resolution features in the retina. Wide-field (2.7°5.4°)and distortionless images from vessel walls, capillaries and the lamina cribrosa are obtained with an enhancedcontrast and signal-to-noise ratio, thanks to the careful control of AO parameters. The high spatialand temporal resolution (image acquisition up to 200 Hz) performance achieved by this platform enablesthe visualization of vessels deformation and blood flow. This system opens up the prospect of a returnto favor of Flood Illumination Adaptive Optics systems provided that its high pixel rate and structuredillumination capabilities are exploited.

Annular waveguide lasers at 1064 nm in Nd:YAGcrystal produced by femtosecond laser inscription

P Wu, SHAN HE, and Hongliang Liu

Doc ID: 328286 Received 12 Apr 2018; Accepted 01 Jun 2018; Posted 04 Jun 2018  View: PDF

Abstract: We report on the fabrication of annular cladding waveguides in Nd:YAG laser crystal by using femtosecond laserinscription. The circular cross sections of the optical waveguides were in dual-cladding and tri-cladding shapeswith different diameters. Under the optical pump at 808 nm, the generated cw lasers at 1064 nm have beenrealized in the annular cladding waveguides. For dual-cladding and tri-cladding waveguides, the slope efficienciesof the waveguide lasers were calculated to be 21.3% and 20%, and the maximum output power measured were 82mW and 84 mW, respectively. In addition, the annular modal profiles were obtained for these cladding waveguides.

Femtosecond, two-photon, laser-induced fluorescence(TP-LIF) measurement of CO in high-pressure flames

Kazi Arafat Rahman, Karna Patel, Mikhail Slipchenko, Terrence Meyer, zhili zhang, Yue Wu, James Gord, and Sukesh Roy

Doc ID: 325985 Received 14 Mar 2018; Accepted 01 Jun 2018; Posted 05 Jun 2018  View: PDF

Abstract: Quantitative, kHz-rate measurement of carbon monoxide mole fractions by femtosecond (fs) two-photon, laserinducedfluorescence (TP-LIF) was demonstrated in high-pressure, luminous flames over a range of fuel-air ratios.Femtosecond excitation at 0.1 nm was used to pump CO two-photon rovibrational Χ1Σ+→B1Σ+ transitions in theHopfield-Birge system and avoid photolytic interferences with excitation irradiance ~1.7×1010 W/cm2. The effectsof excitation wavelength, detection scheme, and potential sources of de-excitation were also assessed to optimizethe signal-to-background and signal-to-noise ratios and achieve excellent agreement with theoretically predictedCO mole fractions at low and high pressure.

Quantitative estimation of elemental compositionemploying synthetic generated spectrum

Prashant Kumar, Rajesh Kushawaha, Swaroop Banerjee, Subramanian K P, and Rudraswami N G

Doc ID: 325238 Received 01 Mar 2018; Accepted 01 Jun 2018; Posted 04 Jun 2018  View: PDF

Abstract: Composition of multi-element samples is estimated by using synthetic generated spectrum utilizing nonlinearfitting routine. By fitting simultaneously a large number of emission lines, the error in the estimationis minimized. The procedure for synthetic spectrum generation includes self-absorption of emissionlines by taking into account the number density of different species in the plasma. The Stark width ofdifferent emission lines are iteratively calculated based on the observed width and the degree of selfabsorptionin the individual lines. This procedure is found to be successful for achieving convergenceof retrieval algorithm even for dense spectrum as well as for resolving merged lines with accuracy. Thisscheme was applied on stainless steel and brass sample and laser induced breakdown spectroscopy resultsmatches well with reference value obtained from electron probe micro-analyzer measurement.

Vision Measurement Error Analysis for Nonlinear LightRefraction at High Temperature

Huaxia Deng, Fei Wang, Jin Zhang, Guoce Hu, mengchao ma, and Xiang Zhong

Doc ID: 325255 Received 05 Mar 2018; Accepted 01 Jun 2018; Posted 04 Jun 2018  View: PDF

Abstract: For the vision measurement at high temperature, pixel error from light refraction by high temperature is aproblem that can not be neglected. The refractive index distribution is nonlinear around the high temperaturecomponent leading to the light deflection. In this paper, the influence of measurement parameterson the deflection of imaging light and the accuracy after binocular reconstruction are systematically analyzed.The heat transfer theory is used to simulate the air temperature distribution near the measuredcomponent and the corresponding refractive index distribution of air is obtained according to the refractiveindex formula. Then the imaging measurement model of the nonlinear refractive index air mediumfor high temperature component is established to obtain the light deflection error. The binocular visionsystem reconstruction theory is applied to evaluate the measurement error between the theoretical reconstructionpoint and the object point. The influences of error sources, such as the temperature, opticalwavelength and camera parameters, are investigated systematically. It is found that temperature and basedistance are the largest error sources on the final measurement error when the measured distance is fixed.

Classical and quantum analysis of propagationinvariant vector flat-top beams

Nkosiphile Andile Bhebhe, Carmelo Rosales, and Andrew Forbes

Doc ID: 326318 Received 19 Mar 2018; Accepted 01 Jun 2018; Posted 04 Jun 2018  View: PDF

Abstract: Laser beams with a near uniform intensity profile, such as flat-top and super-Gaussian beams, have foundmany applications, particularly in laser materials processing. Unfortunately such beams are not eigenmodesof free-space and thus alter their intensity profile during propagation. This may be overcomeby creating vector flat-top beams. Here we exploit the polarisation dependent efficiency of spatial lightmodulators to create a vector flat-top beam that maintains its intensity profile and vector nature duringpropagation. We apply a holistic classical and quantum toolkit to analyse the dynamics of the vector stateduring propagation and demonstrate the versatility of these beams in an optical trapping and tweezingapplication. Our simple generation approach and holistic analysis toolbox will appeal to an audiencewho wish to employ these beams in a variety of applications.

How the alternating degeneracy in rotational Ramanspectra of CO2 and C2H2 reveals the vibrationaltemperature

Dirk van den Bekerom, Jose Palomares Linares, Eddie van Veldhuizen, Sander Nijdam, richard van de sanden, and Gerard van Rooij

Doc ID: 326470 Received 20 Mar 2018; Accepted 01 Jun 2018; Posted 04 Jun 2018  View: PDF

Abstract: The contribution of higher vibrational levels to the rotational spectrum of linear polyatomic moleculeswith a center of symmetry (CO2 & C2H2) is assessed. An apparent nuclear degeneracy is analyticallyformulated by vibrational averaging and compared to numerical averaging over vibrational levels. Itenables inferring the vibrational temperature of the bending and asymmetric stretching modes from theratio of even to odd peaks in the rotational Raman spectrum. The contribution from higher vibrationallevels is already observable at room temperature as ˜ ge/o = 0.96/0.04 for CO2 and ˜ ge/o = 1.16/2.84 forC2H2. The use of the apparent degeneracy to account for higher vibrational levels is demonstrated onspectra measured for a CO2 microwave plasma in the temperature range of 300 to 3500K, and shown to bevalid up to 1500K.

Efficient illumination angle self-calibration in Fourier ptychography

Regina Eckert, Zachary Phillips, and Laura Waller

Doc ID: 325181 Received 06 Mar 2018; Accepted 31 May 2018; Posted 01 Jun 2018  View: PDF

Abstract: Fourier ptychography captures intensity images with varying source patterns (illumination angles) in order to computationally reconstruct large space-bandwidth-product images. Accurate knowledge of the illumination angles is necessary for good image quality; hence, calibration methods are crucial, despite often being impractical or slow. Here, we propose a fast, robust, and accurate self-calibration algorithm that uses only experimentally-collected data and general knowledge of the illumination setup. First, our algorithm makes a direct estimate of the brightfield illumination angles based on image processing. Then, a more computationally-intensive spectral correlation method is used inside the iterative solver to further refine the angle estimates of both brightfield and darkfield images. We demonstrate our method for correcting large and small misalignment artifacts in both 2D and 3D Fourier ptychography with different source types: an LED array, a galvo-steered laser, and a high-NA quasi-dome LED illuminator.

Multicomponent analysis using a confocal Ramanmicroscope

ZHENGYUAN TANG, Sinead Barton, Tomas Ward, John Lowry, Michelle Doran, Hugh Byrne, and Bryan Hennelly

Doc ID: 328080 Received 13 Apr 2018; Accepted 31 May 2018; Posted 01 Jun 2018  View: PDF

Abstract: Measuring the concentration of multiple chemical components in a low volume aqueous mixture by Raman spectroscopy has received significantinterest in the literature. All of the contributions to date focus on the design of optical systems that facilitate the recording of spectra with highsignal-to-noise ratio, by collecting as many Raman scattered photons as possible. In this study, the confocal Raman microscope set-up isinvestigated for multicomponent analysis. Partial Least Squares Regression is used to quantify physiologically relevant aqueous mixtures ofglucose, lactic acid, and urea. The predicted error is 17.81 mg/dL for glucose, 10.6 mg/dL for lactic acid and 7.6 mg/dL for urea, although this canbe improved with increased acquisition times. A theoretical analysis of the method is proposed, which relates the numerical aperture and themagnification of the microscope objective, as well as the confocal pinhole size, to the performance of the technique.

Thermally induced chirp studies on spectral broadening of semiconductor laser diode arrays

Hongyou Zhang, Yangtao Jia, Chung-En Zah, and Xingsheng Liu

Doc ID: 331795 Received 16 May 2018; Accepted 31 May 2018; Posted 05 Jun 2018  View: PDF

Abstract: Spectral width broadening has many factors. Diode lasers are not always monochromatic due to several broadening mechanisms, widening the energy distribution of emitted photons. In this paper, we report the two main factors affecting time average spectral width broadening of a laser diode array (LDA)—a transient rise of the active region temperature of an LDA due to injection current, and the temperature and stress nonuniform distribution of different emitters within an LDA. We find that temperature and stress nonuniformity broadens the spectral width by almost 0.1–1.0 nm as a function of different operating conditions, while the thermal induced chirp that is attributed to injection current plays a more signification role in spectral width broadening.

Measurement of thermal effects of diode-pumpedsolid-state laser by using digital holography

YANG YU, Jianglei Di, Weijuan Qu, and Anand Asundi

Doc ID: 327684 Received 04 Apr 2018; Accepted 31 May 2018; Posted 04 Jun 2018  View: PDF

Abstract: Thermal lensing is one of the most important factors which can affect the performance of high power solid-state lasers,such as limiting the power scaling capability and deteriorating output beam quality. In this paper, a novel and accuratemeasurement of digital holography (DH) is proposed to determine the thermal lensing of diode-pumped solid-statelasers with high resolution.The digitally recorded hologram can reveal the phase change when light travels through the laser gain medium. Fromthe phase map, we can obtain the index variations induced by temperature differences inside the laser crystal when it ispumped by laser diodes (LD), as well as determine the focal length of the integrated thermal lensing focus length. Therewere many works on measuring the static laser medium thermal lens because there is no laser output from the cavity inthe setup. Our experiment setup was able to achieve online measurement with laser output at the same time. Themeasuring result can provide an accurate guide for compensating the thermal lensing in laser design to achieve highpower and good beam quality output. Moreover, detailed index variations in the direction of the laser crystal crosssection can be numerically reconstructed, by which the thermal effects, pump uniformity, crystal uniformity, etc. can berevealed from the holography result.

Ridge waveguide assisted highly efficient TE-pass polarizer based on hybrid plasmonic waveguide

Haixia Zhu, Ran Hao, and Erping Li

Doc ID: 328962 Received 20 Apr 2018; Accepted 31 May 2018; Posted 01 Jun 2018  View: PDF

Abstract: A ridge waveguide assisted highly efficient transverse electric (TE)-pass polarizer is proposed based on hybrid plasmonic waveguide (HPW) on silicon-on-insulator platform. Since the transmission of plasmonic polarizer is greatly influenced by the interaction between the metal and the optical field, there is a large insertion loss (IL) in the polarizer based on HPW. Here, not only the electric field distribution but also the periodic coupling between fundamental TM mode and plasmonic mode are taken into consideration to decrease the IL and shorten the length of the device. For a 4.2μm long polarizer, the calculated extinction ratio is ~29.5dB and the IL is 0.18dB at the central wavelength 1550nm. In addition, more than dB extinction ratio is achieved across a wide bandwidth of 100nm.

Statistics of normalized Stokes polarization parameters

Nathan Hagen

Doc ID: 330398 Received 27 Apr 2018; Accepted 31 May 2018; Posted 04 Jun 2018  View: PDF

Abstract: The normalized Stokes parameters are formed from the ratio of the polarization components to the intensitycomponent of the light. Such ratio distributions are known to have an undefined mean and variance,and yet researchers in the polarization community work with these normalized parameters all the time.We show that while in theory the normalized parameters have a pathological probability density, in practicethey are quite well-behaved. We provide expressions for their approximate densities and confirm theresults with laboratory measurements.

Broadening of the sum-frequency phase-matchingbandwidth by temperature gradient in MgO:PPLN

Dismas Choge, Huaixi Chen, Yi-Bin Xu, Lei Guo, Guang-Wei Li, and Wanguo Liang

Doc ID: 330346 Received 25 Apr 2018; Accepted 31 May 2018; Posted 06 Jun 2018  View: PDF

Abstract: We demonstrate bandwidth broadening in acascaded MgO-doped periodically poled lithiumniobate (MgO:PPLN) crystals (ᴧ=10.3 μm) usingtemperature-gradient technique. Up to 2.8 nmbandwidth at 600 nm spectral region is achievedusing two 50 mm long cascaded MgO:PPLN crystalsvia sum frequency generation. This techniquecombines the merits of high conversion efficiencyattributed to cascaded nonlinearity and thereconfigurability of temperature gradient inducedchirp for broadening of input wavelengthacceptance range.

Modeling and calibration of a precise opticalpositioning system based on four linear cameras

Kai Zhou, Xiangjun Wang, Hong Wei, Lei Yin, Zijing Wan, and Wang Zhong

Doc ID: 324741 Received 27 Feb 2018; Accepted 31 May 2018; Posted 07 Jun 2018  View: PDF

Abstract: This study is intended for modeling and calibration of a precise optical positioning system for tracking 3D positionsof remote targets in a large space. This system is made up of four linear cameras which are equipped withcylindrical lenses. The four cameras are paired up as two identical groups. Cameras in each group are packagedtogether with their imaging orientations normal to each other. The specially designed structure makes the systemsuperior to existing three-linear-CCD-camera systems used for position tracking, in the efficiency of eliminatingdistortion of cylindrical lenses, which is a long-standing problem existing in precise calibration of linear cameraswith cylindrical lenses. During the modeling and calibration process, each camera group is treated as an integrated2D image sensor. A complete imaging model is established for each camera group, and the object-space error isused in calibration for obtaining optimal camera parameters. Simulative and real experiments have verified that,when the two cameras in each group have a good distortion consistency, the proposed calibration approach caneffectively fit the model of linear cameras and correct the distortion of cylindrical lenses, thus leading to asignificant improvement of positioning accuracy.

An imaging method based on the combination ofmicrolens arrays and aperture arrays

Xuewen Chen, Yong Song, weiguo zhang, Muhammad Sulaman, zhao nan, BingTao Guo, Qun Hao, and lin li

Doc ID: 328154 Received 11 Apr 2018; Accepted 30 May 2018; Posted 01 Jun 2018  View: PDF

Abstract: Conventional imaging methods will cause a serious distortion for large object plane imaging with a limited objectto-sensor distance (OTSD). Here, we propose an imaging method based on the combination of microlens arrays andaperture arrays to realize the low distortion, large object plane imaging range (OPIR) and compact design imagingat close OTSD. Two-stage microlens arrays are utilized to reduce the distance between the object and sensor withlow distortion. And two-stage aperture arrays are sandwiched between the microlens arrays to eliminate straylight between different microlenses. The theoretical analysis and simulation results indicate that our proposedmethod can realize a low distortion imaging with a large OPIR when the OTSD is limited seriously. This imagingmethod can be used widely in small-size optical devices where the OTSD is extremely limited.

Enhanced Mid Infrared Emission of Erbium Doped Fluoro-Bromozirconate Glass

Wenlong Ding, Xiaosong Zhang, Lan Li, Qi Ding, Shaohua Wu, Shuili Yu, and Jiajia Zhang

Doc ID: 328467 Received 18 Apr 2018; Accepted 30 May 2018; Posted 01 Jun 2018  View: PDF

Abstract: A series of erbium doped fluoro-bromozirconate glasses modified by various Br- was prepared by using the melt-quenching method. The mid-infrared fluorescence intensity (2.7 μm) has improved by increasing content of Br-. The DSC, X-ray diffraction (XRD), Raman spectra, FTIR and mid-infrared luminescence spectra were measured. The decreased phonon density shows that the structural changes by inserting the Br- can enhance mid infrared luminescent intensity. From the Judd-Ofelt analysis, it is found that the intensity of Ω2 enhanced with the introduction of Br-, which shows larger asymmetry and stronger covalency. Using the Fuchtbauer-Ladenburg theory and McCumber theory, large stimulated emission cross-section (2.9×10-20 cm2) and absorption cross-section (1.68×10-20 cm2) at 2.7 μm were determined. Hence, erbium doped fluoro-bromozirconate glass is a promising candidate for mid-infrared application.

Coherent noise reduction of phase images in digitalholographic microscopy based on the adaptiveanisotropic diffusion

Yumin Wu, Haobo cheng, yongfu wen, Chen Xin, and Yingwei Wang

Doc ID: 326039 Received 15 Mar 2018; Accepted 29 May 2018; Posted 01 Jun 2018  View: PDF

Abstract: The suppression of coherent noise can obtain higher quality reconstructed images in digital holographicmicroscopy. A robust and effective phase coherent noise denoising algorithm is proposed in this paper, whichcombines the anisotropic diffusion equation and the phase quality map. In order to accurately identify the noise andsignal pixels, we introduce the phase quality map and edge detection to quantify the quality of the pixel information.In addition, a synthetic diffusion function is established to control the speed of the anisotropic diffusion process basedon the quality coefficient. Several experiments have been carried out to validate the effectiveness of the proposedalgorithm for coherent noise reduction. The results demonstrate that the proposed algorithm can reduce coherentnoise and preserve edge details well.

Optimal Iodine absorption line applied for spaceborne high spectral resolution lidar

Dong Junfa, Jiqiao Liu, Decang Bi, xiuhua ma, Xiaopeng Zhu, Xiaolei Zhu, and Weibiao Chen

Doc ID: 327151 Received 30 Mar 2018; Accepted 29 May 2018; Posted 30 May 2018  View: PDF

Abstract: Spaceborne High Spectral Resolution Lidar(HSRL) provides a wide range of observations, measurements of aerosol backscattering and extinction coefficients and aerosol depolarization ratio with high accuracy, which are of great significance to the study of air pollution monitoring and climate change. The transmittance of the different absorption lines of the iodine vapor filter with different cells and finger temperatures at 532 nm wavelength was measured . The 1064 nm fundamental frequency pulse energy and frequency doubled 532 nm pulse energy output of different seeder laser wavelengthes were measured. Based on the relationship between the laser output power and the absorption line shape of iodine vapor filter and the atmospheric model, the echo power was calculated and compared. The 1110 iodine absorption line was selected as the optimized filter for the HSRL, which could increase 22% and 14% efficiency compared to traditional 1109 line and new proposed 1105 line at 532 nm HSRL channel, respectively.

Enhanced Plasmonic Photovoltaic using EmbeddedNovel Gear-shaped nanoparticles

Marina Medhat, Yasser El-Batawy, Alaa Abdelmageed, and Ezzeldin Soliman

Doc ID: 327103 Received 29 Mar 2018; Accepted 29 May 2018; Posted 04 Jun 2018  View: PDF

Abstract: In this paper, novel gear-shaped nanoparticles are introduced for the first time to enhance the photovoltaic (PV)efficiency. This has been achieved via increasing the overall power absorption by the PV semiconductor material in bothvisible and near infrared ranges. The modes of the new gear-shaped nanoparticles are investigated. A parametric study hasbeen performed that demonstrates how the design parameters of the proposed nanoparticles can be engineered for bestoverall power absorption within Si surrounding medium. A Figure of Merit (FoM) is defined that takes into account allobjectives. An optimization technique is applied to obtain the optimum set of gear’s dimensions, penetration depth, andperiodicity for the maximum possible FoM. The optimum gear-shaped nanoparticles design offers 48% enhancement in theFoM if compared with bare Si block with no nanoparticles and 7% enhancement over the conventional disk-shapednanoparticles. The enhancement gained by the embedded gear-shaped nanoparticles on the J-V characteristics of the PV isalso studied and the effects of changing the dimensions and the position of nanoparticles on the J-V characteristicsenhancement are investigated.

Characterization of an amplified piezoelectric actuatorfor multiple reference optical coherence tomography

Sean O'Gorman, Kai Neuhaus, Sergey Alexandrov, Josh Hogan, Carol Wilson, Paul McNamara, and Martin Leahy

Doc ID: 321318 Received 09 Feb 2018; Accepted 29 May 2018; Posted 11 Jun 2018  View: PDF

Abstract: The characterization of an amplified piezoelectric actuator(APA) as a new axial scanning method for multiplereference optical coherence tomography (MR-OCT)is described. MR-OCT is a compact optical imaging devicebased on a recirculating reference arm scanning opticaldelay using a partial mirror that can enhance theimaging depth range by more than ten times of the referencemirror scanning amplitude. The scanning amplitudeof the used APA was varied between 30 and250μm depending on the scanning frequency of between0.8 and 1.2 kHz. A silver coated miniature mirrorwas attached to the APA via UV cured optical adhesiveand the light source was a super-luminescentdiode (SLED) with 1310 nm center wavelength and56nm bandwidth. The sensitivity was measured withand without the partial mirror in the reference delayline as a function of scan speed, frequency, and range,therefore, providing results for MR-OCT and TD-OCTmodes. It was found that the APA provides morethan twice of the mechanical scanning range comparedto other opto-mechanic actuators but results indicatedegradation of SNR and sensitivity at larger imagingdepths. In conjunction with MR-OCT the scan range ofmaximum 200μm can be enhanced up to 1 to 1.5mm byusing a reduced amount of orders of reflections whichcould be of interest to increase sensitivity in the future.

Serialised holography for brand protection andauthentication

Dinesh Vather, Izabela Naydenova, Dervil Cody, Monika Zawadzka, Suzanne Martin, Emilia Mihaylova, Stephen Curran, Paul Duffy, Josune Portillo, Daniel Connell, Stephen McDonnell, and Vincent Toal

Doc ID: 327134 Received 29 Mar 2018; Accepted 28 May 2018; Posted 06 Jun 2018  View: PDF

Abstract: The problems presented by counterfeit productsand documentation are discussed. Limitations ofexisting holograms for anti-counterfeitapplications are described. We describe theadvantages of full holographic serialisation andthe requirements in terms of materials andtechniques for mass production of serialisedholograms.These requirements having been met, we reportfor the first time, mass production of fullyserialised holograms. The novelty of approach isthe direct use of product manufacturer’sinformation as the object in a holographicrecording system along with a self-processingphotopolymer and modular optical system tofacilitate mass production of serialised volumeholograms.Various types of serialised holograms for overtand covert authentication are described. Wediscuss briefly the application of Optrace’smanufacturing methods for future generationholographic devices.

Three-dimensional measurement of inner surface profile using supercontinuum beam

Toshitaka Wakayama, Yuta Takahashi, Yuichi Ono, Yusuke Fujii, Takuya Gisuji, TAKUTO OGURA, Natsumi Shinozaki, Shun Yamauchi, Misaki Shoji, Hiromu Kawasaki, Takeshi Higashiguchi, and Toru Yoshizawa

Doc ID: 327152 Received 29 Mar 2018; Accepted 28 May 2018; Posted 31 May 2018  View: PDF

Abstract: We demonstrate an inner surface profile measurement that has a smooth spatial distribution. Supercontinuum beam suppresses the speckle contrast to 22% and the standard deviation of point clouds to 40%, as compared to that of the use of a conventional green He-Ne laser at a wavelength of 543.5 nm. A compact probe for the inner surface profile measurements using the supercontinuum beam measures the depth removed by wear of a small hole in automobile components. The radial spatial resolution was evaluated to be 2 μm, which was the same order of the wavelength of the supercontinuum beam. The supercontinuum beam enables the radial spatial resolution five-fold as compared to the monochromatic wavelength beam because of reduction of the speckle effects.

ABER performance analysis of LDPC-coded OFDM FSO system under Málaga distribution considering atmospheric attenuation and pointing errors

Mengyi Duan, Ping Wang, Xiaoxia Liu, Yutao Li, Wenwen Chen, and Ang Li

Doc ID: 326407 Received 20 Mar 2018; Accepted 27 May 2018; Posted 31 May 2018  View: PDF

Abstract: The average bit error rate (ABER) performance of low-density parity-check (LDPC)-coded orthogonal frequency-division multiplexing (OFDM) free-space optical communication system with K-ary quadrature amplitude modulation (QAM) and phase shift keying (PSK) modulation schemes is investigated over the composite Málaga (M) fading channel with atmospheric attenuation and pointing errors considered. The probability density function (PDF) and cumulative distribution function (CDF) regarding to the aggregated channel model are derived and with the help of generalized Guass-Lagurre quadrature rule, the analytical ABER expressions for both QAM and PSK OFDM systems are then obtained. On the basis of them, the ABER performance is analyzed with different turbulence strengths, weather conditions, normalized beam width, normalized jitter and specifically, different values of Málaga distribution parameter ρ . Monte Carlo simulation is offered to confirm the correctness of the proposed ABER models. Moreover, LDPC codes are added into the simulation to enhance the system performance. The result shows that, for the same turbulence, weather and pointing error conditions, whether the LDPC codes are taken into account or not, the ABER performance of 16-QAM OFDM system is better than that of 16-PSK OFDM system over Málaga fading channel, and the ABER result decreases with higher ρ for both modulation schemes. Furthermore, the LDPC coding can significantly improve the system performance over this aggregated fading channel for these two modulation schemes, and lower LDPC code rate can obtain a better ABER performance. This work is beneficial for the FSO system design.

Numerical Investigation of Feed-forward LinewidthReduction Scheme Using a Mode-Locked Laser Modelof Reduced Complexity

Sean O Duill, Omar Sahni, Stephane Trebaol, Pascal Landais, Laurent Bramerie, Stuart Murdoch, Pascal Besnard, and Liam Barry

Doc ID: 320808 Received 16 Feb 2018; Accepted 24 May 2018; Posted 29 May 2018  View: PDF

Abstract: We provide numerical verification of a feed-forward, heterodyne-based phase noise reduction scheme using singlesideband modulation that obviates the need for optical filtering at the output. The main benefit of a feedforwardheteroydyne linewidth reduction scheme is the simultaneous reduction of the linewidth of all modes of a modelockedlaser (MLL) to that of a narrow linewidth single-wavelength laser. At the heart of our simulator is an (MLL)model of reduced complexity. Importantly, the main issue being treated is the jitter of MLLs and we show how tocreate numerical waveforms that mimic the random walk nature of timing jitter of pulses from MLLs. Thus themodel does not need to solve stochastic differential equations that describe the MLL dynamics, and the modelcalculates self-consistently the line-broadening of the modes of the MLL and shows good agreement with both theoptical linewidth and jitter. The linewidth broadening of the MLL modes are calculated after the phase noisereduction scheme and we confirm that the phase noise contribution from the timing jitter still remains. Finally weuse the MLL model and phase noise reduction simulator within an optical communications systems simulator andshow that the phase noise reduction technique could enable MLLs as optical carriers for higher order modulationformats such as 16-state and 64-state quadrature amplitude modulation.

Simulated annealing optimization in wavefront shaping controlled transmission

Zahra Fayyaz, NAFISEH mohammadin, Faraneh Salimi, afreen fatima, mohammadreza rahimitabar, and Mohammad Avanaki

Doc ID: 319134 Received 17 May 2018; Accepted 24 May 2018; Posted 22 Jun 2018  View: PDF

Abstract: In this research, we present results of the simulated annealing (SA), a heuristic optimization algorithm, for focusing light through a turbid medium. The performance of the algorithm on phase and amplitude modulations has been evaluated. A number of tips to tune the optimization parameters are provided. Moreover, the effect of measurement noise on the performance of the SA algorithm is explored.

Holographic characterization of diffraction gratings modulation in photopolymers

Haoyu Li, Yue Qi, Changliang Guo, Ra'ed Malallah, and John Sheridan

Doc ID: 327402 Received 03 Apr 2018; Accepted 22 May 2018; Posted 23 May 2018  View: PDF

Abstract: It is known that in general the recorded holographic grating refractive index profiles are notidentical to the sinusoidal exposing pattern in photopolymer materials. During exposure highharmonics of the fundamental refractive index period are generated within the layer volume. Aset of equations to calculate the amplitudes of the higher harmonics of refractive index inducedin the grating are introduced. Then an algorithm involving the use of the 3-D nonlocal photopolymerizationdriven diffusion (NPDD) model is presented and applied to calculate theresulting grating diffraction efficiencies. The experimental observation results that the gratingdiffraction efficiency cannot reach the theoretical maximum value (ηmax = 100%) and that in thecase of over-modulation the minimum value (ηmin = 0%) is also never achieved, are explained(theoretically). The predictions of the simulations are also fit to measured experimental data foran Acrylamide/polyvinyl alcohol (AA/PVA) photopolymer material with good agreement beingachieved.

Calibration of a high spectral resolution lidarusing a Michelson interferometer, with dataexamples from ORACLES

Sharon Burton, Chris Hostetler, Anthony Cook, Johnathan Hair, Shane Seaman, Salvatore Scola, David Harper, John Smith, Marta Fenn, Richard Ferrare, Pablo Saide, Eduard Chemyakin, and Detlef Mueller

Doc ID: 326234 Received 22 Mar 2018; Accepted 14 May 2018; Posted 19 Jun 2018  View: PDF

Abstract: The NASA Langley airborne 2nd generation High Spectral Resolution Lidar (HSRL-2) uses a density-tuned fieldwidenedMichelson interferometer to implement the HSRL technique at 355 nm. The Michelson interferometeroptically separates the received backscattered light between two channels, one of which is dominated by molecularbackscattering while the other contains most of the light backscattered by particles. This interferometer achieveshigh and stable contrast ratio, defined as the ratio of particulate backscatter signal received by the two channels.We show that a high and stable contrast ratio is critical for precise and accurate backscatter and extinctionretrievals. Here we present retrieval equations that take into account the incomplete separation of particulate andmolecular backscatter in the measurement channels. We also show how the accuracy of the contrast ratioassessment propagates to error in the optical properties. For both backscattering and extinction, larger errors areproduced by underestimates of the contrast ratio (compared to overestimates), more extreme aerosol loading,and— most critically— smaller true contrast ratios. We show example results from HSRL-2 aboard the NASA ER-2aircraft from the 2016 ORACLES field campaign in the southeast Atlantic off the coast of Africa during the biomassburning season. We include a case study where smoke aerosol in two adjacent altitude layers showed oppositedifferences in extinction- and backscatter-related Ångström exponents and a reversal of the lidar ratio spectraldependence, signatures which are shown to be consistent with a relatively modest difference in smoke particlesize.

Modal Analysis of a Novel Class with Thin MultiTrench-assisted Liquid Filled Optical WaveguideCoupler for Simultaneous Multi-sensing Applications

sanjeev raghuwanshi, Manish Kumar, and Om Prakash

Doc ID: 326694 Received 23 Mar 2018; Accepted 10 May 2018; Posted 04 Jun 2018  View: PDF

Abstract: Analysis of a novel class of the thin multi trench-assisted optical coupler for multi-sensing of chemicaldetection is presented. The design structure is an optical waveguide coupler consisting of closely-coupledtrenches with different liquid for the chemical sensing. The refractive index profile of the coupler isallowed to vary due to chemical filled in these trenches. The scalar finite difference method (FDM) is usedto analyze TE (s 􀀀 polarized) as well as TM (p 􀀀 polarized) modes thereafter propagate them along thestructure through various trenched sections. We excite the structure with Eigenmode profile which canbe well approximated by Gaussian shape pulse. The trenches with different chemicals and separationbetween them are well demonstrated by using an example. The main finding of this paper is that thecoupling period of the structure can be changed by altering the refractive index of the trench region. InFDM analysis, we have used the variable discretization step for the better accuracy of these results. A newapproach based on thin multi-trench assisted optical coupler scheme to analyze and design of chemicalsensor is than proposed for diagnosis of adulteration present in beverages, medical industry.

Preparation and quantitative characterization of Polydimethylsiloxane optical phantomswith Zinc-Phthalocyanine dye absorbers

Adamo Monte, Arnaldo Reis, Luismar Junior, and Andrea Antunes

Doc ID: 326388 Received 19 Mar 2018; Accepted 07 May 2018; Posted 08 May 2018  View: PDF

Abstract: We described a method for the preparation of polydimethylsiloxane (PDMS) phantoms tomimic the optical properties of biologic tissues at distinct wavelengths ranging from thevisible to the near-infrared spectra. The present method for fabricating solid optical tissuephantoms using Zinc-Phthalocyanine chromophores has demonstrated high photostabilitywith optical absorption coefficients up to 1.0 mm−1, making this phantom proper withabsorption bands ranging from 600 to 850 nm. It also happens that the chromophoreabsorption coefficient is linear as a function of its concentration inside the previous opticalwindow. The optical scattering properties were quantitatively selected by adding TiO2particle concentrations to the PDMS phantom. Thus, the quantitative optical properties ofabsorption and scattering for a large batch fabrication were demonstrated, making the Zinc-Phthalocyanine phantoms suitable for use as a reference standard.

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

Rajab Nasehi and Mohammad Mahmoudi

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

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

Dependence of depth of focus on spherical aberration of optical systems

Antonin Miks and Jiri Novak

Doc ID: 267338 Received 31 May 2016; Accepted 05 Jul 2016; Posted 06 Jul 2016  View: PDF

Abstract: This paper presents a theoretical analysis and computation of aberration coefficients of the third and fifth order of transverse spherical aberration of an optical system, which generates a ray bundle with a diameter of a geometric-optical circle of confusion smaller than a predetermined limit value. Equations were derived for the calculation of aberration coefficients of an optical system, which satisfy given conditions, and for the determination of the maximum possible depth of focus for given conditions.

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