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Accepted papers to appear in an upcoming issue

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Image restoration and color fusion of digitalmicroscope

Shuai Pan, Bo Yang, Xinru Xie, and Zhuxi Yun

Doc ID: 354670 Received 05 Dec 2018; Accepted 13 Feb 2019; Posted 13 Feb 2019  View: PDF

Abstract: Traditional microscopes do not meet a wide field of view and high resolution at the same time. Wepropose a method for image restoration and color fusion of digital microscope. It combines a single highresolutiongray scale hologram with a low-resolution color image to obtain a high-resolution colorimage. Specifically, the high-resolution gray scale image is obtained by reconstructing three differentheight holograms using a wavelet-based method, and the color information is obtained using a portablecell phone microscope. The subsequent calibration and blending of colors ultimately result in a highresolution, wide-field color map that can be of great help in the study of pathology or biomedicine. Thismethod breaks the rule that the large field of view and high resolution of a traditional microscopecannot be simultaneously satisfied, which can realize a more comprehensive observation of the shapeand details of the slice.

A Time-of-Flight Imaging System Based on ResonantPhotoelastic Modulation

Okan Atalar, Raphaël Van Laer, Christopher Sarabalis, Amir Safavi-Naeini, and Amin Arbabian

Doc ID: 353158 Received 30 Nov 2018; Accepted 13 Feb 2019; Posted 13 Feb 2019  View: PDF

Abstract: A time-of-flight (ToF) imaging system is proposed and its working principle demonstrated. To re- alize this system, a new device, a free-space optical mixer, is designed and fabricated. A scene is illuminated (flashed) with a megahertz level amplitude modulated light source and the reflected light from the scene is collected by a receiver. The receiver consists of the free-space optical mixer, comprising a photoelastic modulator sandwiched between polarizers, placed in front of a standard CMOS image sensor. This free-space optical mixer downconverts the megahertz level amplitude modulation frequencies into the temporal bandwidth of the image sensor. A full scale extension of the demonstrated system will be able to measure phases and Doppler shifts for the beat tones and use signal processing techniques to estimate the distance and velocity of each point in theilluminated scene with high accuracy.

Thermal hydraulic performance ofmicrochannel heat sink for cooling highpowerdiode laser bar

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

Doc ID: 355974 Received 20 Dec 2018; Accepted 13 Feb 2019; Posted 13 Feb 2019  View: PDF

Abstract: Numerical and analytical methods are employed to investigate the thermal andfluid flow performance of microchannel heat sink for cooling high-power diode laser bar.Heat transfer characteristics and pressure drop in the microchannel under different flow ratesare studied. A thermal resistance network which is proved with an error less than 5.4% isproposed to characterize resistance components for the microchannel heat sink. Bothnumerical modeling and thermal resistance network analysis are verified by the experimentalresults based on wavelength shift method. Two new heat sinks are presented with moreuniform temperature distribution for laser emitters compared to the existing design, and theperformances are validated by numerical modeling and spatially resolved spectrummeasurements.

Research on simultaneous measurement oftemperature and refractive index based on thin-corefiber and pokal-taper

yimei zhong, Juan Qin, zhengrong tong, Weihua Zhang, Wei Huang, and Wenlin Gao

Doc ID: 356691 Received 03 Jan 2019; Accepted 13 Feb 2019; Posted 13 Feb 2019  View: PDF

Abstract: An in-line optical fiber sensor is proposed and demon- strated for simultaneous measurement of temperature and refractive index(RI). This sensor can be obtained by splicing two pokal-taper structures and a segment of thin-core fiber(TCF). The middle segment of the TCF works as the sensing region and the two pokal-taper structures work as an exciter and a coupler. The trans- mission spectra formed by different lengths of TCF are analyzed theoretically and then the appropriate length is selected during the experiment. The purpose of si- multaneous measurement of temperature and RI can be achieved due to different parameter responses of the two dips used in the experiment. The sensitivities of the two dips are 0.076nm/°C and 0.082nm/°C during the temperature range of -20°C—20°C. The sensitivities of the two dips are -43 nm/RIU and -30.83 nm/RIU during the RI range of 1.335—1.37. The proposed sensor hasmany advantages and wide application prospects.

A 2D reproduction of the face on the TurinShroud by infrared femtosecond pulse laserprocessing

Christophe DONNET, Julien Granier, Gaetan VERGÉ, Yannick BLEU, Stéphanie Reynaud, and francis vocanson

Doc ID: 347642 Received 16 Oct 2018; Accepted 13 Feb 2019; Posted 14 Feb 2019  View: PDF

Abstract: Femtosecond pulse laser processing concentrates a huge quantity of light energy inextremely short pulses of a few tens to hundreds of femtoseconds, enabling superficial lasermachining or marking of any kind of materials, with a reduced or insignificant heat affectedarea. A digitized paper printed image of the face on the Turin Shroud was used to monitor ascan head intercalated between a femtosecond pulsed laser source and a linen fabric sample,enabling the direct 2D reproduction of the image of the face with a laser beam sizecorresponding to one pixel of the digitized image. The contrast in the marked image wascontrolled by adjusting the energy density, the number of superimposed pulses per pixel, andthe distance between successive impacts. The visual aspect of the laser-induced image is verysimilar, at naked eye, to the source image. The negative photograph of the marked linen fabricreveals a face remarkably close to the well-known negative picture of the face on the TurinShroud. Analyses by infrared spectroscopy, Raman spectroscopy and scanning electronmicroscopy were performed to characterize the laser marked areas.

Rotation measurements using a a resonant fiberoptic gyroscope based on Kagome fiber

Alexia Ravaille, gilles Feugnet, Benoît Debord, Frédéric Gérôme, Fetah Benabid, and Fabien Bretenaker

Doc ID: 354540 Received 03 Dec 2018; Accepted 12 Feb 2019; Posted 13 Feb 2019  View: PDF

Abstract: We build a resonant fiber optic gyro based on Kagome hollow-core fiber. A semi-bulkcavity architecture based on a 18-m-long Kagome fiber permits to achieve a cavity finesse of with a resonance linewidth of 700 kHz. An optimized Pound-Drever-Hall servo-locking schemeis used to probe the cavity in reflection. Closed-loop operation of the gyroscope permits toreach an angular random walk as small as 0.004ph and a bias stability of 0.45/h over 0.5 s ofintegration time.

Tin Gallium Oxide Solar-Blind Photodetectors onSapphire Grown by Molecular Beam Epitaxy

Partha Mukhopadhyay and Winston Schoenfeld

Doc ID: 355384 Received 14 Dec 2018; Accepted 12 Feb 2019; Posted 13 Feb 2019  View: PDF

Abstract: We report on Tin Gallium Oxide ((SnxGa1-x)2O3) solarblindmetal-semiconductor-metal (MSM) photodetectorsgrown by plasma assisted molecular beam epitaxy on cplanesapphire substrates with varying Tin content up toXSn = 10%. Incorporation of Sn into Ga2O3 was found toshift the optical bandgap of the epilayers from 5.0 eV(248 nm) for 0% Sn to 4.6 eV (270 nm) for 10% Sncontent. Varying of the Sn concentration was also foundto enable controlled tuning of the peak responsivity andcut-off wavelengths of MSM devices fabricated from theepilayers, with peak responsivity ranging from 0.75 A/Wto nearly 16 A/W as the Sn concentration was increasedfrom 0% to 10%. The high responsivity is attributed tophotoconductive gain that increases for higher Snconcentrations and is accompanied by a slowing of thetemporal response of the MSM detectors.

High-spectral-resolution Mie Doppler lidar based ontwo-stage Fabry-Perot etalon for tropospheric windand aerosol accurate measurement

Fa Shen, Jie Ji, Chenbo Xie, Zhao Wang, and bangxin wang

Doc ID: 354957 Received 10 Dec 2018; Accepted 12 Feb 2019; Posted 13 Feb 2019  View: PDF

Abstract: A two-stage Fabry-Perot etalon (FPE) based high-spectral-resolution (HSR) Mie Doppler lidar technology isproposed that is capable of simultaneously detecting tropospheric wind and aerosol optical properties with highprecision.The lidar structure is designed and the measurement principle is analyzed. A two-channel integratedFPE forming a two-stage FPE ensures the relative stability of they spectra. The HSR first-stage etalon can effectivelysuppress the contamination of Rayleigh signal. The transmission and reflection spectra of the second-stage etaloncan form double edge to measure wind speed. Two multimode polarization insensitive optical circulators are usedto achieve high-efficiency utilization for backscattering signals. The parameters of the two-stage FPE are optimized.According to the selected system parameters, the detection performance of the proposed lidar is simulated.Simulation results show that with 150m range resolution and 1min total accumulation time for the pairedline-of-sight (LOS) measurement, within ±25m/s LOS wind speed range, the nighttime and daytime LOS wind speederrors are below 0.48m/s and 2.5m/s respectively for clear day, and below 0.58m/s and 5.5m/s respectively forhazy day from 0.1 to 8 km altitude; the backscatter ratio relative errors are below 2.7% up to 8 km for clear day,and below 4.6% up to 5 km for hazy day. Compared with the traditional dual-FPE based double-edge (DE) MieDoppler lidar, the wind speed accuracies are improved by 2.02~3.58 times for clear day and 2.14~4.31 times forhazy day.

Beam Smoothing by Diffraction-weakened LensArray combining with Induced SpatialIncoherence

Xiaohui Zhao, YAN-QI Gao, Fujian Li, Lailin Ji, Yong Cui, Daxing Rao, WEI FENG, and Weixin Ma

Doc ID: 355168 Received 11 Dec 2018; Accepted 12 Feb 2019; Posted 13 Feb 2019  View: PDF

Abstract: The smoothing scheme combining diffraction-weakened lens array with inducedspatial incoherence method is proposed and demonstrated to be an efficient smoothing scheme forbroadband laser system. In our simulation, the rms illumination nonuniformity of the target spotis reduced to 2% after sufficient smoothing time, The temporal characteristics and spatial powerspectral density of the scheme are theoretically analyzed. For the incident light has intensityfluctuations, the uniformity of target spot is stable, which means a robustness smoothing schemeand predicts practical applications to the smoothing of broadband laser system.

A modified constellation reshaping method forPAPR reduction of PDM CO-OFDM based onSLM algorithm

Wuhua Zou, Tianye Huang, Jiachen Yuan, Wang Dianhong, xiang li, and Zhuo Cheng

Doc ID: 356654 Received 03 Jan 2019; Accepted 12 Feb 2019; Posted 12 Feb 2019  View: PDF

Abstract: In this paper, we propose a modified constellation reshaping method forpeak-to-average power ratio (PAPR) reduction in polarization division multiplexing (PDM)coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems based onselective mapping (SLM) method. A modified quadrature amplitude modulation (M-QAM)constellation is generated, which has the same minimum distance as that of the conventionalQAM (C-QAM) constellation. The M-SLM method is denoted as the M-QAM constellationscombining with the traditional SLM method. At the receiver side, the mean square errorsbetween the constellations of the received data and each M-QAM rotated by different phaserotation factors are calculated. Then, the phase rotation factor with the minimum meansquare error is selected to recover the original data. The advantage of the proposed method isthat it does not need to send additional side information while nearly possesses the samePAPR reduction and bit error rate (BER) performance as those of the traditional SLMmethod.

Analysis and correction of distortions in a spatialheterodyne spectrometer system

Jilin Liu, Daikang Wei, Oliver Wroblowski, Qiuyu Chen, Klaus Mantel, FRIEDHELM OLSCHEWSKI2, Martin Kaufmann, and Martin Riese

Doc ID: 351623 Received 09 Nov 2018; Accepted 12 Feb 2019; Posted 13 Feb 2019  View: PDF

Abstract: In this paper a method for correcting the radial distortionof interferograms generated by a spatial heterodynespectrometer system is presented. Instead of utilizingcalibration patterns, the distortion model parametersare estimated based on the distorted fringe featuresgenerated by projecting the straight interferencestripes onto the detector. Comparisons between polynomialmodels and division models indicate that divisionmodels can deliver competitive performance on the reconstructedimage with fewer parameters. Simulatedinterferograms based on ray-tracing are used to demonstratethe correction of errors in spatial, phase and spectraldomain caused by optical distortion.

On acceleration sensitivity of 2 m whisperinggallery mode based semiconductorself-injection locked laser

Anatoliy Savchenkov, Danny Eliyahu, Brandon Heist, Andrey Matsko, Mahmood Bagheri, Clifford Frez, and Siamak Forouhar

Doc ID: 352640 Received 26 Nov 2018; Accepted 12 Feb 2019; Posted 13 Feb 2019  View: PDF

Abstract: While whispering gallery mode resonators are well known for their low accelerationsensitivity, xperimental research on the subject. We performed environmental sensitivity tests of a 2 µm semiconductor distributed feedback (DFB) laser, self-injection locked to a high-Q crystalline whispering gallery mode resonator. Measured acceleration sensitivity of the laser is below 5 10−11g−1 in the 1 200 Hz frequency bandwidth and thermal sensitivity does not exceed 12 MHz/oC. The laserâĂŹs frequency noise is below 50 Hz/Hz1/2 at Fourier frequencies ranging from 10 Hz to 1 MHz, reaching 0.4 Hz/Hz1/2 at 400 kHz. The instantaneous linewidth of the laser is improved by nearly four orders of magnitude compared to the free-running DFB laser, and is measured to be 50 Hz at 0.1 ms measurement time. The Allan deviation of the laser frequency is on the order of 10−9 from 1 s to 1,000 s. All se features make the laser attractive for metrology applications involving low noise 2 µm seedlasers.

Chromatic confocal microscopy using liquidcrystal display panels

Qi Cui and Rongguang Liang

Doc ID: 355108 Received 13 Dec 2018; Accepted 11 Feb 2019; Posted 12 Feb 2019  View: PDF

Abstract: A chromatic confocal microscopy system in combination with two liquid crystaldisplay (LCD) panels is proposed and demonstrated for surface profiling. The majoradvantage of this system is no mechanical translation is needed for three-dimensional (3D)imaging. The axial scanning is realized thanks to the chromatic aberration in the objective,whereas the lateral scanning is achieved by turning on different pixels on LCDs. Chromaticaberration of objective lens is used to provide wavelength-to-depth coding and decoding isrealized by using a dispersion prism. System performance is validated with a 50 μm stepstandard and the capability of 3D imaging is demonstrated with an onion epidermis.

Slow light in ultra-compact photonic crystaldecoder

Tina Daghooghi, Mohammad Soroosh, and Karim Ansari-Asl

Doc ID: 351475 Received 08 Nov 2018; Accepted 11 Feb 2019; Posted 11 Feb 2019  View: PDF

Abstract: In this study, merging two photonic crystal-based structures, a new design for all-optical 2-to-4 decoder has been proposed. The switching operation is based on Kerr effect and refractiveindex modification. The structure consists of one nonlinear ring resonator and three nonlinearcavities that have been modified for entering the slow light regime in order to enhancecoupling through waveguides. The maximum group index of 94 has been obtained for theproposed slow light waveguides. With this approach, the maximum and minimum normalizedoutput powers for logic 0 and 1 are 4% % and 82%, respectively. The data transfer rate of thedecoder is 220 GHz, and the size of the structure is 24×9.5 μm2. The maximum insertion lossand cross-talk are -7.45 dB and -16.38 dB, respectively. Considering the abovecharacteristics, the proposed decoder can be qualified as a part of optical integrated circuits.

Experimental study on chemical mechanical polishing of Chalcogenide glasses

Dongbai Xue, Peng Wang, Lingyan Jiao, Weihao Li, and yiqin ji

Doc ID: 355968 Received 21 Dec 2018; Accepted 10 Feb 2019; Posted 12 Feb 2019  View: PDF

Abstract: Chalcogenide glasses is one of the core components for the infrared athermalized optical system. Because of material properties, its processing properties are limited and surface defects are difficult to control. The chemical nature of Ge10As40Se50 has been established, which can react with sodium hydroxide (NaOH) and hydrogen peroxide (H2O2). On this basis, to investigate the properties of Chemical Mechanical Polishing by experiments furtherly. As experimental results, both agents can effectively improve the surface quality of substrates. When the concentration of H2O2 is about 10wt% to 15wt%, the best result is obtained, which surface defects and surface roughness are significantly improved (Surface roughness RMS ≈ 0.31nm).

Vignetted-aperture correction for spectralcameras with integrated thin-film Fabry-Pérotfilters

Thomas Goossens, Bert Geelen, Andy Lambrechts, and Chris Van Hoof

Doc ID: 356393 Received 07 Jan 2019; Accepted 09 Feb 2019; Posted 12 Feb 2019  View: PDF

Abstract: Spectral cameras with integrated thin-film Fabry-Pérot filters have become increasinglyimportant in many applications. These applications often require the detection of spectral featuresat specific wavelengths or to quantify small variations in the spectrum. This can be challengingsince thin-film filters are sensitive to the angle of incidence of the light. In prior work wemodeled and corrected for the distribution of incident angles for an ideal finite aperture. Manyreal lenses however experience vignetting. Therefore in this article we generalize our modelto the more common case of a vignetted aperture, which changes the distribution of incidentangles. We propose a practical method to estimate the model parameters and correct undesiredshifts in measured spectra. This is experimentally validated for a lens mounted on a visible tonear-infrared spectral camera.

A novel method for measuring the resonant absorptioncoefficient of rare-earth-doped optical fibers

Mostafa Peysokhan, Esmaeil mobini souchelmaei, Behnam Abaie, and Arash Mafi

Doc ID: 357254 Received 08 Jan 2019; Accepted 09 Feb 2019; Posted 11 Feb 2019  View: PDF

Abstract: A non-destructive method for measuring the resonant absorption coefficient of rare-earth-doped opticalfibers is introduced. It can be applied to a broad range of fiber designs and host materials. The methodcompares the side-collected spontaneous emission at two arbitrary locations along the fiber as a functionof the pump wavelength to extract the absorption coefficient. It provides an attractive and accurate alternativeto other available techniques. In particular, the proposed method is superior to the cut-backmethod, which destroys the sample and is prone to inaccuracies due to the cladding mode contamination.Moreover, because it does not involve any mechanical movement, it can be used for fragile optical fibers.

Realization of phosphor-in-glass thin film onsoda-lime silicate glass with low sinteringtemperature for high color rendering white LEDs

Shuvamoy Bindai, Anal Tarafder, and Annapurna Kalyandurg

Doc ID: 355267 Received 02 Jan 2019; Accepted 08 Feb 2019; Posted 13 Feb 2019  View: PDF

Abstract: Y3Al5O12:Ce3+ phosphor-in-glass (PiG) thin film on soda lime silicate glasssubstrate have been applied using screen printing method for generation of white LED light inmodern day lighting. In this work, a glass composition in ZnO-Bi2O3-B2O3 system has beenoptimized to have low softening temperature as well as matching refractive index with that ofY3Al5O12: Ce3+ phosphor. The sintering of the PiG layers was performed at a relatively lowtemperature of 560°C to avoid the chemical degradation of the phosphors. We employed acombination of powder X-ray diffraction, scanning electron microscopy (SEM), energydispersive spectroscopy (EDS), UV-visible absorption and fluorescence spectroscopy as wellas Fourier transfer infrared (FTIR) spectroscopy to study the detailed structure and differentspectral properties of PiG samples. This Y3Al5O12:Ce3+-based PiG exhibits an externalquantum efficiency of ∼40% even with its thickness of 5μm only. Under the excitation of bluelaser diode source, the synthesized PiG thin film has exhibited a bright white light with highcolor rendering index (CRI = 92 and CCT = 3877 K). The synthesized PiG sample was usedto design a high power white light emitting diode (WLED) module by combining it with a 3Wblue LED on-board chip. This module is expected to be a promising candidate for nextgenerationillumination at a relatively lower cost having long-term reliability.

Indoor three-dimensional high-precision positioningsystem with bat algorithm based on visible lightcommunication

Li Huang, Ping Wang, Zhongyu Liu, Xi Nan, Lingling Jiao, and Lixin Guo

Doc ID: 351422 Received 07 Nov 2018; Accepted 08 Feb 2019; Posted 11 Feb 2019  View: PDF

Abstract: A three-dimensional (3-D) positioning system on the basis of bat algorithm (BA) using visible lightcommunication (VLC) is proposed in this work. BA is a global optimization algorithm that can be used to solvethe indoor positioning problem. In BA, the positioning process is considered to be a process of searching for thereceiver by many bats in the indoor space of 3m × 3m × 4m. Therefore, taking advantage of the bat searchalgorithm, the 3-D low-complexity and high-precision indoor positioning is able to be actualized when thenumber of iterations reaches certain condition. The simulation results show that the system can achieve highprecisionpositioning in different signal-to-noise ratios (SNRs). Meanwhile, the trajectory tracking experiment iscarried out to testify the good performance of this positioning system. The proposed algorithm is a positioningmethod with good potential in various positioning applications.

High-resolution terahertz coded-aperture imagingfor near-field three-dimensional target

Cheng-Gao Luo, Bin Deng, Hongqiang Wang, and Yuliang Qin

Doc ID: 351718 Received 13 Nov 2018; Accepted 08 Feb 2019; Posted 08 Feb 2019  View: PDF

Abstract: In this paper, we propose a high-resolution terahertz coded-aperture imagingmethod with fast beam scanning for near-field three-dimensional target. This method utilizes acoded aperture to modulate incident terahertz wave randomly and to drive the terahertz beamto scan the entire imaging space step by step. Theoretical analyses based on physical opticsare performed and simulation experiments are implemented to demonstrate the feasibility ofthe proposed method.

Common-path interferometry with tilt carrier forsurface measurement of complex optics

Jia Li, Hua Shen, Jinsong Wang, and Rihong Zhu

Doc ID: 354846 Received 12 Dec 2018; Accepted 07 Feb 2019; Posted 08 Feb 2019  View: PDF

Abstract: We propose a novel common-path non-null interference system for the surfacemeasurement of complex optics. Due to the common-path structure, the systematic errors aremostly eliminated and the complexity of the system calibration is reduced of the proposedsetup. However, optical design of common-path non-null interference system is of greatdifficulty because lots of off-axis beams are used to compensate for the local gradient of themeasured piece. Different from the classical common-path interferometers which pay moreattention to the beam quality of on-axis FOV, the proposed system requires better quality forboth on-axis and off-axis outgoing beams. In the proposed setup, the lens groups with wideFOV affords wave aberrations better than 0.1 λ for the on-axis and off-axis FOVs.Simultaneously, the off-axis beams are prevented from generating pseudo reference beams byoptimizing the parameters of the lenses and the aperture. In addition, multiple tilted testbeams generated by a point-source generator based on fiber array, which is more versatilethan lens-array-type point-source-generator. Further, a universal measurement system withhigh accuracy and time-saving is formed, as evidenced by the measurement results of aparabolic mirror and different types of cylindrical mirrors.

Computational Image Speckle Suppression using Block Matching and Machine Learning

Tianjiao Zeng, Hayden K.H. So, and Edmund Lam

Doc ID: 349073 Received 23 Oct 2018; Accepted 07 Feb 2019; Posted 07 Feb 2019  View: PDF

Abstract: We develop an image despeckling method that combines nonlocal self-similarity (NSS) filters with machine learning, which makes use of convolutional neural network (CNN) denoisers. It consists of three major steps: block matching, CNN despeckling, and group shrinkage. Through the use of block matching, we can take advantage of the similarity across image patches as a regularizer to augment the performance of the data-driven denoising using a pre-trained network. The outputs from the CNN denoiser and the group coordinates from block matching are further used to form 3D groups of similar patches, which are then filtered through a wavelet-domain shrinkage. The experimental results show that the proposed method achieves noticeable improvement compared with state-of-the-art speckle suppression techniques, both in visual inspection and objective assessments.

Curved detectors for astronomical applications: characterization results on different samples

Simona Lombardo, Thibault Behaghel, Bertrand Chambion, Stéphane Caplet, Wilfried Jahn, Emmanuel Hugot, Eduard Muslimov, Melanie Roulet, Marc FERRARI, Christophe Gaschet, and David Henry

Doc ID: 346854 Received 26 Sep 2018; Accepted 07 Feb 2019; Posted 08 Feb 2019  View: PDF

Abstract: Due to the increasing dimension, complexity and cost of the future astronomical surveys, new technologies enabling more compact and simpler systems are required. The development of curved detectors allows to enhance the performances of the optical system used (telescope or astronomical instrument), while keeping the system more compact. We describe here a set of five curved CMOS detectors developed within a collaboration between CEA-LETI and CNRS-LAM.These fully-functional detectors 20 Mpix (CMOSIS CMV20000) have been curved to different radii of curvature and spherical shapes (both convex and concave) over a size of 24x32 mm^2. Before being able to use them for astronomical observations, we assess the impact of the curving process on their performances.We perform a full electro-optical characterization of the curved detectors, by measuring the gain, the full well capacity, the dynamic-range and the noise properties, such as dark current, readout noise, pixel-relative-non-uniformity. We repeat the same process for the flat version of the same CMOS sensor, as a reference for comparison. We find no significant difference among most of the characterization values of the curved and flat samples. We obtain values of readout noise of 10e- for the curved samples compared to the 11e- of the flat sample, which provides slightly larger dynamic ranges for the curved detectors. Additionally we measure consistently smaller values of dark current compared to the flat CMOS sensor. The curving process for the prototypes shown in this paper does not significantly impact the performances of the detectors. These results represent the first step towards their astronomical implementation.

Absorption of light by water in the region ofhigh transparency: recommended values forphoton-transport calculations

Matthew Fewell and Alice von Trojan

Doc ID: 348325 Received 15 Oct 2018; Accepted 07 Feb 2019; Posted 08 Feb 2019  View: PDF

Abstract: Prompted by data requirements for photon-transport simulation, we have surveyedmeasurements of the absorption coefficient of light by water in the wavelength range 171–2000 nm, covering the whole region where the absorption length exceeds 1 mm. Absorptionspectra were compiled for pure water, clean seawater and seawater containing a moderateamount of organic matter. The intensive and detailed nature of the laboratory and at-seaobservations leading to the pure-water and clean-seawater spectra lend confidence to theseresults. As to dissolved organic matter in seawater, this is so highly variable in compositionand concentration that this spectrum can only be considered as indicative of its effects.

A miniaturized ring-down spectrometer for CubeSat-based planetary science

Bradley Gibson

Doc ID: 345707 Received 12 Sep 2018; Accepted 07 Feb 2019; Posted 07 Feb 2019  View: PDF

Abstract: A robust, miniaturized cavity ring-down spectrometer has been developed as a laboratory demonstration model for future CubeSat deployments of near- and mid-infrared spectrometers for in-situ planetary science. The spectrometer is compact enough to ensure compatibility with standard CubeSat spacecraft buses, with a probed gas volume of less than 2.5 cc to ease mass, volume, and power requirements of sample gas handling subsystems. When operated at 1.39 µm for water vapor isotope measurements, a noise-equivalent absorption coefficient of 3.7 × 10−9 cm−1 Hz−1/2 is obtained. Oxygen isotope measurements were performed to demonstrate scanning performance. The spectrometer has been designed to use only components with functional equivalents throughout the 1 - 5 µm range to maintain flexibility across a wide array of planetary science targets - preliminary results from a 3.27 µm implementation intended for methane measurements are also presented.

Effect of imaging geometry and noise model on polarimetric contrast optimization

jun dai, Matthieu Boffety, and Francois Goudail

Doc ID: 347261 Received 01 Oct 2018; Accepted 06 Feb 2019; Posted 07 Feb 2019  View: PDF

Abstract: We study the effect of noise model and imaging geometry on contrast optimization with active polarimetric imager. Considering scenes with various polarization contrast sources and fluctuation statistics of polarimetric properties, we show that to maximize the range of scene orientation angles for which contrast is sufficient, one has to take into account not only the polarization difference between target and background but also the variance of fluctuations in the image. In particular, for scenes exhibiting depolarization contrast, the best strategy is often to set the illumination and analysis polarization states orthogonal to each other in order to reduce the variance of the image. These results are important for designing and optimizing remote sensing or robotics-oriented polarization imagers.

Quantitative femtosecond, two-photon laser-induced fluorescence of atomic oxygen in high-pressure flames

Kazi Arafat Rahman, venkatasubramanian athmanathan, Mikhail Slipchenko, Sukesh Roy, James Gord, zhili zhang, and Terrence Meyer

Doc ID: 354807 Received 10 Dec 2018; Accepted 06 Feb 2019; Posted 06 Feb 2019  View: PDF

Abstract: Quantitative femtosecond two-photon laser-induced fluorescence of atomic oxygen was demonstrated in an H2/Air flame at pressures up to 10 atm. Femtosecond excitation at 226.1 nm was used to pump the 3p3PJ’=0,1,2←←2p3PJ”=0,1,2 electronic transition of atomic oxygen. Contributions from multiphoton de-excitation, production of atomic oxygen and photolytic interferences were investigated and minimized by limiting the laser irradiance to ~1011 W/cm2. Quantitative agreement was achieved with the theoretical equilibrium mole fraction of atomic oxygen over a wide range of fuel-air ratios and pressures in an H2/Air laminar calibration burner.

Highly coherent, Watt-level deep-UV radiation via afrequency-quadrupled Yb-fiber laser system

Zakary Burkley, Adam Brandt, Cory` Rasor, Samuel Cooper, and Dylan Yost

Doc ID: 356977 Received 11 Jan 2019; Accepted 06 Feb 2019; Posted 06 Feb 2019  View: PDF

Abstract: We demonstrate a 1.4 W continuous wave (CW) laser at 243.1 nm. The radiation is generated throughfrequency quadrupling the output of a ytterbium-doped fiber amplifier system which produces > 10 Wof CW power at 972.5 nm. We demonstrate absolute frequency control by locking the laser to an opticalfrequency comb and exciting the 1S–2S transition in atomic hydrogen. This frequency-stabilized, highpowerdeep-UV laser is of significant interest for precision spectroscopy of simple and exotic atoms, twophotonlaser cooling of hydrogen, and Raman spectroscopy.

Influences of Aberration on Spatial Resolution of STEDMicroscope in Probing Specimen with DiscontinuousRefraction Indices

chao xiao, Chen Zhang, jie Zhu, wei zhao, Jintao Bai, qingli He, and kaige wang

Doc ID: 348629 Received 29 Oct 2018; Accepted 04 Feb 2019; Posted 04 Feb 2019  View: PDF

Abstract: The probing depth and system aberrations have direct impacts on the spatial resolution of Stimulated EmissionDepletion (STED) microscope. Base on the vectorial diffraction theory, the influence of coma and astigmatism onthe focal patterns of STED microscope in probing stratified mediums with discontinuous refractive indices (e.g.glass coverslip, solution and biological samples etc) have been illustrated in details. The spatial resolution of theSTED system has been discussed by analyzing the Full Width of Maximum (FWHM) size of the fluorescence spots. Itis found that, while probing in the stratified mediums with discontinuous refractive indices, the spatial resolutionof STED microscope can be very sensitive to the existence of aberrations, e.g. coma and astigmatism, at differentprobing depth, as a result of mismatched axial positions of the excitation and depletion patterns. The spatialresolution of STED can be degraded upto 1.87 and 1.95 folds compared to that without aberrations. Therefore, acareful evaluation of the influence of aberration and discontinuous refractive indices should be taking into accountwhen applying STED microscope to realize super-resolution image.

Simultaneous measurement of phase transmission and linear or circular dichroism of an object under test

Sergej Rothau, Xiao Rao, and Norbert Lindlein

Doc ID: 355972 Received 20 Dec 2018; Accepted 04 Feb 2019; Posted 05 Feb 2019  View: PDF

Abstract: This publication presents a novel interferometric method for the simultaneous spatially resolved analysis of an object under test regarding the phase transmission function and the magnitude and orientation of dichroism. Analogous to the classical phase shifting interferometry the measurement strategy is based on the variation of phase and polarization in an interferometer. This procedure allows to analyse simultaneously and spatially resolved the dichroic properties of the object and its impact on the phase of the incoming light in one measurement cycle. The theoretical description of the investigated methods and their experimental implementation are presented.

Full image reconstruction with reduced speckle noise,from a partially illuminated Fresnel hologram, using astructured random phase

Maria Cruz

Doc ID: 346582 Received 01 Oct 2018; Accepted 03 Feb 2019; Posted 04 Feb 2019  View: PDF

Abstract: In computer generated holograms a random phase is added to spread out the object wave, but this introducesa strong speckle noise in the reconstructed image. Spread out the object wave helps to record alarge object in a smaller hologram. We propose a random repeated and displaced phase, which reducesthe speckle noise in the reconstructed image and spread out the object information in a limited area. Thephase is independent of the object, and it could be calculated by sections reducing the hologram computingtime. We present simulated and experimental results that prove the improvement in the quality of thereconstructed image and the whole object reconstruction, using only a small part of the hologram.

On the Temperature Sensitivity ofScattering-Type Near-field Nanoscopic Imagingin the Visible Range

Amun Jarzembski, Cedric Shaskey, Ryan Murdick, and Keunhan Park

Doc ID: 351465 Received 08 Nov 2018; Accepted 02 Feb 2019; Posted 04 Feb 2019  View: PDF

Abstract: Due to its superb imaging spatial resolution and spectroscopic viability, scatteringtypescanning near-field optical microscopy (s-SNOM) has proven to be widely applicable fornanoscale surface imaging and characterization. However, limited works have investigatedthe sensitivity of the s-SNOM signal to sample temperature. This article reports the sampletemperature effect onto the non-interferometric (self-homodyne) s-SNOM scheme at a visiblewavelength ( = 638 nm). Our s-SNOM measurements for an arrayed vanadium/quartz sampledemonstrate a monotonic decrease of the signal intensity as sample temperature increases. Asa result, s-SNOM imaging cannot distinguish quartz and vanadium when the sample is heatedto 309 K: all signals are close to the root-mean-square noise of the detection scheme usedfor this study (i.e., 19 V-rms). While further studies are required to better understand theunderlying physics of such temperature dependence, the obtained results suggest that s-SNOMmeasurements should be carefully conducted to meet a constant sample temperature condition,particularly when a visible-spectrum laser is to be used as the light source.

Pose error correction in offline three-dimensionalprofile measurement system for large-diameteraspheric mirror

Jianpu Xi, Bin Li, Dongxu Ren, and Zexiang Zhao

Doc ID: 351539 Received 08 Nov 2018; Accepted 01 Feb 2019; Posted 04 Feb 2019  View: PDF

Abstract: This paper proposes an off-line measurement method for a large aspheric mirrorduring its grinding stage. A measurement method and mathematical model to realisethree-dimensional (3D) profile measurement for large-diameter aspheric mirrors are proposed,based on a cylindrical coordinate system. The measurement error induced by the alignmenterror is examined based on the error analysis of the measurement and workpiece coordinatesystems. The corresponding pose error obtained through the nonlinear least squares method iseliminated to improve the measurement accuracy. To evaluate the entire surface profile error,3D profile model is established. The total uncertainties of the proposed measurement systemare also estimated. Comparison experiments for a 300-mm- diameter K9 glass workpiece areconducted on UPFM900 and Taylor Hobson PGI 3D profile instruments, and the profileaccuracy is found to be improved from 15.3 to 7.12μm after eccentricity and tilt errorelimination.

Design of dual-band infrared zoom lens withmultilayer diffractive optical element

Bo Zhang, Qingfeng Cui, Mingxu Piao, and Yang Hu

Doc ID: 348248 Received 15 Oct 2018; Accepted 01 Feb 2019; Posted 01 Feb 2019  View: PDF

Abstract: A mid-wave infrared (MWIR)/ long-wave infrared (LWIR) dual-band zoom lens design with multilayer diffractiveoptical elements (MLDOEs) is presented. The mathematical relationship between the substrate material selection fordual-band MLDOE and polychromatic integral diffraction efficiency (PIDE) is deduced in the oblique incidentsituation, and further, a method for optimal selection of substrate material is proposed to obtain the high PIDE in anincident angle range. In the optimization process, the optimal substrate material combination is selected based onthe proposed method, and the principle of lens material replacement is discussed. After optimization, the 5× hybriddual-band infrared zoom system is obtained which is consisted of 7 lenses. The modulation transfer function valuesin all configurations are larger than 0.5 and 0.3 in MWIR and LWIR, respectively. The distortion values are less than2% both in MWIR and LWIR for all configurations.

Graphene Based Bidirectional Radiative ThermalTransfer Method for Heat Engines

Alireza Nojeh, George Sawatzky, and Lorne Whitehead

Doc ID: 353354 Received 03 Dec 2018; Accepted 01 Feb 2019; Posted 01 Feb 2019  View: PDF

Abstract: We present a method for substantially enhancing the rate of heat transfer into and out of the working fluid of a heatengine, using bidirectional thermal radiation exchange between the external environment and many individualgraphene layers that are dispersed and suspended within an inert gas. This hybrid working fluid has the uniquecomposite property of high optical absorption/emission yet low specific heat. Consequently, it can heat and coolrapidly, enabling a much greater cycle frequency and a commensurate increase in specific power, in comparison toconventional closed cycle heat engines for which the cycle frequency is limited by the use of slower, non-radiative,thermal transfer.

Digital holographic particle volume reconstructionusing a deep neural network

Tomoyoshi Shimobaba, Takayuki Takahashi, Yota Yamamoto, Yutaka Endo, Atsushi Shiraki, Takashi Nishitsuji, Naoto Hoshikawa, Takashi Kakue, and Tomoyoshi Ito

Doc ID: 354570 Received 04 Dec 2018; Accepted 01 Feb 2019; Posted 01 Feb 2019  View: PDF

Abstract: This paper proposes a particle volume reconstruction directly from an in-line hologram using a deepneural network. Digital holographic volume reconstruction conventionally uses multiple diffraction calculationsto obtain sectional reconstructed images from an in-line hologram, followed by detection of thelateral and axial positions, and the sizes of particles by using focus metrics. However, the axial resolutionis limited by the numerical aperture of the optical system, and the processes are time-consuming. Themethod proposed here can simultaneously detect the lateral and axial positions, and the particle sizesvia a deep neural network (DNN). We numerically investigated the performance of the DNN in terms ofthe errors in the detected positions and sizes. The calculation time is faster than conventional diffractedbasedapproaches.

Structured ultrasound-modulated optical tomography

Maïmouna Bocoum, Jean-Luc Gennisson, jean-baptiste laudereau, Anne Louchet-Chauvet, Jean-Michel Tualle, and Francois Ramaz

Doc ID: 346368 Received 19 Sep 2018; Accepted 31 Jan 2019; Posted 01 Feb 2019  View: PDF

Abstract: Ultrasound-modulated optical tomography (UOT) is an imaging technique which couples light and ultrasoundin order to perform in-depth imaging of highly scattering media. In previous work, we introducedplane-wave UOT, an imaging method analogous to X-ray tomography based on the filtered backprojectionfor image reconstruction. Angle-limited measurements however led to drastic loss of lateral spatial resolution.Here, we present a new structured ultrasonic plane wave UOT method that allows partial recoveryof the resolution. For image reconstruction, we present a generalization of Fourier Slice Theorem alongwith a generalized filtered backprojection formalism. The method is successfully tested on simulated andexperimental data.

Phase shifting interferometry-based Fouriertransform channeled spectroplarimeter

Ali Altaqui and Michael Kudenov

Doc ID: 353335 Received 05 Dec 2018; Accepted 30 Jan 2019; Posted 31 Jan 2019  View: PDF

Abstract: Channeled spectropolarimetry is a snapshot technique for measuring the spectraldependence of the state of polarization of light. However, it suffers from two majorlimitations, namely, its high sensitivity to environmental perturbations, and its susceptibilityto channel crosstalk. These limitations reduce the polarimetric reconstruction accuracy of thespectropolarimeter. A new calibration technique for channeled spectropolarimetry ispresented that utilizes the concept of phase shifting interferometry to accurately acquire anddemodulate the retardation phase factors, thereby, improving the accuracy of the Stokes datareconstruction as well as enabling more robust performance. The new technique also enablesthe acquisition of high-resolution intensity spectrum by adopting a dual-scan measurementtechnique for reducing crosstalk. Experimental results show that calibrations using phaseshifting interferometry yield higher data reconstruction accuracy as compared to the selfcalibrationtechnique.

Reversibility and repeatability of tensile deformationresponse in holographic sensor

Hongpeng Liu, wang rui, wang baohua, Li Li, jiao xinying, Song Qinggong, and Yu Dan

Doc ID: 353399 Received 04 Dec 2018; Accepted 30 Jan 2019; Posted 31 Jan 2019  View: PDF

Abstract: Reversibility and repeatability of tensile deformation response in holographic sensor formed byhighly stretchable acrylamide polymer have been investigated. The diffraction spectrum ofvolume grating was used to characterize the deformation. Two-way shifts of peak wavelengths, i.e.red-shift in transmission and blue-shift in reflection, were observed in stretching. The reductionof average refractive index provided an experimental evidence for the physical mechanism. Toachieve linear response and high repeatability, the limitation of tensile displacement wasdetermined as 5.0mm, and the relevant deformation is 6.6%. This value can be considered as aboundary between the elastic and plastic deformations in the sample with thickness less than120μm. There was a totally linear relation between peak wavelength and deformation within theelastic range. The reversible and repeatable deformation response validated the practicalapplicability of a holographic sensor.

Bidirectional Transmittance and Reflectance Models for Soil Signature Analysis

Romuald Tapimo, Cipriani Carlos Atemkeng, Herve Thierry Kamdem, Myriam Lazard, David Yemele, Rene Tchinda, and Edouard Henri Zefack Tonnang

Doc ID: 354523 Received 10 Dec 2018; Accepted 30 Jan 2019; Posted 31 Jan 2019  View: PDF

Abstract: The propagation of radiation in an absorbing-scattering soil with constant or spatial variation of the refractiveindex is investigated. The soil consists of plane parallel with Fresnel reflection at the boundaries and is exposed atone boundary to a diffuse or collimated incident radiation. The discrete spherical harmonics method usingMarshak boundary conditions is introduced to approximate the directional hemispherical reflectance andtransmittance as well as the bidirectional reflectance. The effect in spatial variation of the refractive index on thereflectance and transmittance predictions is examined. A comparison of the directional- transmittance andreflectance with the literature results demonstrates that the present method gives accurate results for opticallythin and thick soil with the maximum relative error in all cases less than 1%. The bidirectional radiance forvariable refractive index soils also shows excellent agreement as compared to the literature results. The resultsdemonstrated that the anisotropic soil interfaces causes a significant decrease of energy reflected and transmittedas well as the bidirectional reflectance.

Pixel-by-pixel absolute phase retrieval assisted by an additional 3D scanner

Yatong An and Song Zhang

Doc ID: 355243 Received 12 Dec 2018; Accepted 30 Jan 2019; Posted 06 Feb 2019  View: PDF

Abstract: This paper presents a novel absolute phase unwrapping method assisted by a low-cost three-dimensional (3D) scanner. The proposed absolute phase unwrapping method leverages a low-cost 3D scanner to capture rough 3D data of the scene, and transforms the rough 3D data to the world coordinate system to generate an artificial reference phase map Φref. By referring to Φref, we can do absolute phase unwrapping directly without projecting any additional patterns, such that the DFP system can achieve higher measurement speed. We develop a multi-resolution system consisting of a DFP system and Kinect V2 to validate our method. Experiments demonstrate that our method works for a large depth range, and the speed of the low-cost 3D scanner does not necessarily limit our DFP measurement speed. Assisted by Kinect V2, our DFP system achieves 53Hz with a resolution 1600x1000 pixels when we measure dynamic objects that are moving in a large depth range.

Photochemical reflective optical fiber sensor forselective detection of phenol in aqueous solutions

ZHENGKUN WANG, Nianbing Zhong, MING CHEN, HAIXING CHANG, DENGJIE ZHONG, Yongwu Wu, Huinin Liu, Xin Xin, M Zhao, Bing Tang, Tao Song, and Shenghui Shi

Doc ID: 354475 Received 03 Dec 2018; Accepted 29 Jan 2019; Posted 11 Feb 2019  View: PDF

Abstract: A PHOTOCHEMICAL FIBER-OPTIC SENSOR HAS BEEN DEVELOPED BY INTEGRATING A PLASTIC OPTICAL FIBER (POF), POLYMER MEMBRANE, GOLDMIRROR, AND TIO2-BASED COMPOSITE, AND WAS SHOWN TO SENSITIVELY AND SELECTIVELY DETECT PHENOL IN AQUEOUS SOLUTION. THE SENSINGELEMENT CONSISTED OF A THINNED POF AND VISIBLE-LIGHT-DRIVEN SIO2/N-DOPED TIO2 COATING. THE GOLD MIRROR WAS USED TO DEVELOP AREFLECTIVE POF PROBE. THE POLYMER MEMBRANE WITH HIGH PHENOL PERMSELECTIVITY WAS EMPLOYED TO FORM A MICRO-CHANNELBETWEEN THE MEMBRANE AND PROBE. OUR FINDINGS HIGHLIGHT THE SENSOR’S CAPABILITY OF PHENOL DETECTION IN AQUEOUS SOLUTIONS WITHHIGH SENSITIVITY OF 0.294×10-3 (MG·L-1)-1, PH IMMUNITY RANGING FROM 2.0 TO 14.0, AND HIGH SELECTIVITYWITH A LIMIT OF DETECTION OF 30 ΜG·L-1.

Information transmission using radial carpet beams

Mahdi Khodadadi Karahroudi, Mohammad Khodadadi Karahroudi, abolhasan mobashery, and Bahman Parmoon

Doc ID: 353249 Received 30 Nov 2018; Accepted 29 Jan 2019; Posted 30 Jan 2019  View: PDF

Abstract: Radial Carpet (RC) beam is a new class of beams that is a subfamily of combined half-integer Bessel-like beamswhich are a set of solutions for the wave equation and has been introduced recently. In this paper, we propose anindoor optical communication link using RC beams encoding/decoding. By employing spatial light modulators(SLM), loaded with radial gratings and fork shaped gratings as encoder and decoder, respectively, we generate anddetect different modes of RC beams as encoding states. In the experiment, we transmit a 2-bit gray scale image of50×50 pixels by four different states of RC modes. The system bit error rate (BER) is measured and a zero BER isachieved after transmitting 2500 modes. We then transmit an 8-bit RGB image of 70×77 pixels by 16 differentmodes of hexadecimal states to analyze the performance of the communication link in the presence of RC modeswith higher RC orders. By defining an optimum threshold value, the maximum improvement of 100% in the fidelityfor transmitting 3 40 hexadecimal states in an indoor ideal medium is achieved. The obtained results show anacceptable performance for the proposed communication system based on RC beams especially in the case of lowerRC orders.

Influence of asymmetric grating structures onmeasurement accuracy in integrated phase gratinginterference-based metrology

Tao Zhang, Xingyu Zhao, Jiwen Cui, and Jiubin Tan

Doc ID: 353375 Received 03 Dec 2018; Accepted 29 Jan 2019; Posted 30 Jan 2019  View: PDF

Abstract: We present an analysis of position error caused by asymmetry in phase grating measurement systems,demonstrating that such error is dependent on the structure of grating and the measurement order. Theasymmetry-induced error varies as a function of diffraction order, with the nature of this variation depending ongrating structure. We verify our analysis by comparing the average error obtained with a multi-orderinterferometer to the error simulated using an AFM scanning profile. The deviations of different orders ofasymmetry-introduced error are less than +/- 3nm. This result provides an explanation of diffraction fields andmeasurement errors from asymmetric gratings.

A compact low-noise passively mode-lockedEr-doped femtosecond all-fiber laser with 2.68GHz fundamental repetition rate

Jia-Zheng Song, Hushan Wang, Huang Xinning, Xiaohong Hu, Ting Zhang, Yishan Wang, Yuanshan Liu, and Jian-Guo Zhang

Doc ID: 354774 Received 10 Dec 2018; Accepted 29 Jan 2019; Posted 30 Jan 2019  View: PDF

Abstract: A passively mode-locked Er-doped fiber laser with a fundamental repetition rate of2.68 GHz is reported. The oscillator operating at a central wavelength of 1558.35 nm has acompact, robust structure and low-noise performance. The timing jitter integrated from 30MHz down to 300 Hz is 82.5 fs and the timing jitter performance is analyzed based on thetheory model. The amplification and compression of the high repetition rate optical pulses arealso investigated. After a three-stage amplifier, the average power is boosted to 430 mW.Meanwhile, based on the nonlinear self-phase modulation effect, the spectral bandwidth isbroadened from 7.56 nm to 19.2 nm and the corresponding pulse width is compressed to 244fs.

Experimental investigation of laser-inducedbreakdown spectroscopy assisted with laser-inducedfluorescence for trace aluminum detection in steatiteceramics

Nan Zhao, Dongqi Lei, Xiangyou LI, Jiaming Li, Qiongxiong Ma, Qingmao Zhang, Liang Guo, and Yongfeng Lu

Doc ID: 348913 Received 22 Oct 2018; Accepted 29 Jan 2019; Posted 31 Jan 2019  View: PDF

Abstract: Laser-induced breakdown spectroscopy (LIBS) assisted with laser-induced fluorescence (LIF) was introduced todetect trace aluminum in steatite ceramics in this work. Mechanism and transition process of laser-inducedaluminum atomic fluorescence in laser-induced plasma was described and discussed. Selective enhancement of LIFand temporal synchronicity between radiation laser and fluorescence were studied. The influence of ablation laserenergy, power density of radiation laser, interpulse delay was experimentally investigated. The results showedthat 60 mJ in ablation laser energy and 4 μs in interpulse delay were the optimal choice for fluorescent intensity.The fluorescence was increased to the saturation level over 4 MW/cm2. Spectral stability improvement of LIBS-LIFwas also discovered in this work. The results proved that LIBS-LIF is a feasible and effective modification of LIBS forceramics analysis.

Fast and high efficiency superconducting nanowiresingle-photon detector at 630 nm wavelength

Heqing Wang, Hao Li, Lixing YOU, Yong Wang, Lu Zhang, Xiaoyan Yang, Weijun Zhang, Zhen Wang, and Xiaoming Xie

Doc ID: 351455 Received 13 Nov 2018; Accepted 28 Jan 2019; Posted 30 Jan 2019  View: PDF

Abstract: Fast and high efficiency single-photon detectors have important applications in the fields of life science andquantum information. We report herein a serially connected two superconducting nanowire avalanche photondetector (SC2-SNAP) fabricated on a dielectric mirror aiming to 630 nm wavelength. This detector shows asystem detection efficiency (SDE) of 84.8% at a dark count rate of 10 Hz, and offers fast detection speed whilemaintaining a high SDE, where the counting rate reaches 53.9 MHz at an SDE of 60%. This fast and high efficiencysingle-photon detector may find applications in fluorescence correlation spectroscopy and quantum keydistribution.

Design of Silicon-wire Waveguide Ultra-compact Racetrack Resonators: Geometrical Parameters for Optimal Coupling

Ramón José Pérez

Doc ID: 346647 Received 10 Oct 2018; Accepted 28 Jan 2019; Posted 28 Jan 2019  View: PDF

Abstract: In this paper it is shown that a suitable choice of the geometrical parameters of a Silicon-wire waveguide micro-racetrack resonator structure can lead to a substantial improvement in the control of coupling coefficients and, hence, the design of ultra-compact devices for high performance channel add-drop filters and all-optical switching applications. On the one hand, it will be showed that the reduction of the Silicon-wire rectangular waveguide cross-section area (width height) is possible, from standard (450 nm 220 nm) to (380 nm 200 nm) on both, the bus and the resonator waveguides; this action, apart from still guaranteeing a quasi-TE single-mode operation, would provide an effective improvement into scale-of-integration by a 1.30 factor per device volume. On the other hand, it will be shown by a semi-analytical method (analytical calculation + numerical simulation) that achieving the waveguide-racetrack optimal coupling condition for a particular application can be reduced to a prime calculation of the main resonator geometrical parameters (bend-radius, straight length, air-gap and overall coupling length). In particular, the design of high performance ultra-compact waveguide-racetrack resonator structures, with pre-established Q-factor (Q ≥ 2000), Free-Spectral-Range (FSR ≥ 15 nm), Full-Width-at-Half-Maximum (FWHM ≤ 5 nm), Finesse (F ≥ 40) or Extinction-Ratio signals(ER ≥ 20 dB) can be systematically obtained with this procedure.

An Image Contrast Enhancement MethodBased on Display and HVS Characteristics

Guo Chen, Li Li, Weiqi Jin, Mingcong Liu, and Feng Shi

Doc ID: 348720 Received 19 Oct 2018; Accepted 28 Jan 2019; Posted 28 Jan 2019  View: PDF

Abstract: At the present time, there are many image contrast enhancement methods wherethe main considerations are detail enhancement, noise suppression, and high contrastsuppression. Traditional methods ignore the characteristics of the display, or merely considerthe display as a whole. However, due to the limited dynamic range of most display devices onthe market, the difference between two adjacent grayscales of the display is often below theJND (Just Noticeable Difference) of the human visual systems (HVS), which causes manyimage details to be invisible on the display. To solve this problem, we present a preprocessingmethod for image contrast enhancement. The method combines the characteristics of thehuman eye and the display to enhance the image by examining the local histogram. Whendisplaying the processed image, the algorithm maintains as much image information aspossible, and image details will not be lost due to the limits of the display device. Moreover,this algorithm performs well for noise suppression and high contrast suppression. Thealgorithm is an image enhancement method and can also be a correction method for imagesenhanced by other methods when prepared for display.

A General Silicon-on-Insulator Higher Order ModeConverter based on Substrip Dielectric Waveguides

Basma Abu-elmaaty, Mohammed sharaf, Ramesh Pokharel, and Hossam Shalaby

Doc ID: 352335 Received 19 Nov 2018; Accepted 28 Jan 2019; Posted 28 Jan 2019  View: PDF

Abstract: A general silicon mode-converter waveguide, that con- verts a fundamental mode to any higher-order mode, is proposed. Specifically, dielectric substrip waveguides are inserted in the fundamental mode propagation path so that the conversion is done directly in the same prop- agation waveguide, without coupling the power into another waveguide as it happens in traditional mode converters. The device has a very small footprint com- pared to traditional converters. A mathematical model is developed to determine the design parameters of the used dielectric material and analyze the whole perfor- mance of the proposed device. Both the effective index method (EIM) and the perturbative mode-coupled the- ory are used in our mathematical analysis to get exact values for both the coupling coefficient and the length of the used dielectric material so as to ensure a maxi- mum coupled power transfer to the higher-order mode. In addition, full vectorial 3D-FDTD simulations are performed to validate our mathematical model. Our re- sults show good agreement between the approximate EIM method and accurate full vectorial 3D-FDTD simu- lations in characterizing the device parameters and per- formance.In order to validate the design model, two mode con-verters are simulated, fabricated, and tested for con- verting a fundamental TE0 mode into both first- and second-order (TE1 and TE2) modes, respectively. Good insertion losses and low crosstalks are obtained. Good agreement between simulated and fabricated resultsare achieved.

Prediction of Lifetime by lumen degradation and colorshift for LED lamp, in non-accelerated reliability testover 20,000 hours

Hao Jian, Hong-Liang Ke, Lei Jing, Qiang Sun, and Ren-Tao Sun

Doc ID: 353005 Received 28 Nov 2018; Accepted 28 Jan 2019; Posted 28 Jan 2019  View: PDF

Abstract: Although the predicted lifetime of classical 6,000 hours test given by Energy Star is taken as the normal lifetime of LEDproducts in most researches and applications, the aim of this study is to explore the error in lifetime prediction of LEDlamp based on 6,000 hours test. A non-accelerated aging test with ten LED lamps is conducted for 20,000 hours (fromMarch, 2016 to now) under room temperature, which is long enough for this kind of lamp reaching the real lifetime withthe normalized luminous flux dropping to 70% naturally. At different aging periods, the correspondent lifetime of eachsample is predicted by the lumen degradation, and the median lifetime τ0.5 of ten samples is obtained by applying theWeibull distribution. Result shows that the τ0.5 of real lifetime is 16,867 hours in this work, and the aging time should beat least 9,000 hours to make the error in predicting the lifetime less than 3%. On the other hand, the Du’v’ values of0.006, 0.007 and 0.008 are taken as the three thresholds for predicting the lifetime by color shift. For case of 0.008, thecalculated shape parameter of 8.4 in Weibull distribution is similar with that of real lifetime, which means the Du’v’ of0.008 for this kind of lamp gives the same failure mechanism as that of lumen degradation of 70%.

Effects of end surface and angle coupling on modesplitting and suppression in a cylindrical microcavity

Ming Yan, Xiaobei Zhang, Jiawei Wang, Fengyu Hou, Lei Yang, Wen Sun, Yong Yang, and Tingyun Wang

Doc ID: 351587 Received 13 Nov 2018; Accepted 28 Jan 2019; Posted 28 Jan 2019  View: PDF

Abstract: Cylindrical microcavity conventionally has the characteristics of simple fabrication and high Q factor, where therich physics of mode splitting and suppression caused by mode excitation, coupling and interference has beenrealized for highly sensitive sensing and cavity quantum electrodynamics. In this paper, we show experimentallyand theoretically, that a simple method to tailor these two mechanisms via near-end surface and angle coupling ina single mode fiber cylindrical microcavity. Mode splitting can be enhanced due to the interference betweenlocalized and axial modes as the effect of near-end surface coupling, validated by the coupled-mode model. Besides,we also demonstrate that the coupling angle between the fiber taper and cylindrical microcavity can efficientlyaffect the mode suppression in the transmission spectrum. Such a kind of device owns a simple structure, simplefabrication process and simple mechanism to tailor the mode splitting and suppression for applications in cavityquantum electrodynamics, sensitive sensing and other topics of photonics.

Bloch surface waves at the telecommunicationwavelength with Lithium Niobate as top layer forintegrated optics.

Tatiana Kovalevich, Djaffar Belharet, Laurent Robert, gwenn ulliac, Myun-Sik Kim, Hans Peter Herzig, Thierry Grosjean, and Maria Pilar Bernal

Doc ID: 347874 Received 19 Oct 2018; Accepted 28 Jan 2019; Posted 29 Jan 2019  View: PDF

Abstract: Lithium niobate (LN) based devices are widely usedin integrated and nonlinear optics. This material is robustand resistive to high temperatures, which makesthe LN-based devices stable, but challenging to fabricate.In this work we report on the design, manufacturingand characterization of engineered dielectric mediawith thin film lithium niobate (TFLN) on top for thecoupling and propagation of electromagnetic surfacewaves at the telecommunication wavelengths. The designedone-dimentional photonic crystal (1DPhC) sustainsBloch surface waves at the multilayer/air interfaceat 1550 nm wavelength with a propagation detectedover a distance of 3 mm. The working wavelengthand improved BSW propagation parameters open theway for exploration of nonlinear properties of BSWbased devices. It is also expected that these novel devicespotentially would be able to modify BSW propagationand coupling by external thermal/electrical stimulidue to the improved quality of the TFLN top layerof 1DPhC.

Performance analysis of the infrared imaging system for aircraft plumes detection from the geostationary orbit

Hang YUAN, Xiao-rui Wang, BingTao Guo, Dong Ren, weiguo zhang, and Ke Li

Doc ID: 354753 Received 10 Dec 2018; Accepted 28 Jan 2019; Posted 29 Jan 2019  View: PDF

Abstract: In view of the optical detection requirements of the wide area and the continuous surveillance of the air targets, the detection ability of the infrared imaging system in the geostationary orbit for the aircraft plume is studied. The point spread model of the sub-pixel imaging of the full chain including the aircraft plume - the sea surface - the environmental atmosphere - the optical system - the imaging detector is established. The detection ability of the typical imaging system in the geostationary orbit is analyzed from the signal-to-noise ratio (SNR) and the detection range in combination with the effect of point spread function (PSF) of the optical system. Meanwhile, the optimal coupling condition of the PSF to the spatial resolution is discussed. The imaging characteristics of the aircraft target on the focal plane of the infrared imaging system under different spatial sampling rates are simulated and verified. Research shows that the SNR of the system increases first, and then decreases gradually with an increasement of the spatial sampling rates. The detectable range covered by the pixel footprint decreases as the detector size increases. When the detector sizes are 15μm, 20μm and 30μm, the target can be detected at spatial resolutions of 200m~700m, 300m~700m and 400m~600m, respectively.

Multi-octave supercontinuum from visible to mid-IR and Bend Effects on Ultrafast NonlinearDynamics in Gas-filled Hollow-core Fiber

Md Selim Habib, Christos Markos, Jose Antonio-Lopez, and Rodrigo Amezcua Correa

Doc ID: 351456 Received 26 Nov 2018; Accepted 26 Jan 2019; Posted 28 Jan 2019  View: PDF

Abstract: Broadband supercontinuum generation is numerically investigated in a Xe-filled nested hollow-core anti-resonantfiber pumped at 3 μm with pulses of 100 fs duration and 15 μJ energy. For a 25 cm long fiber, under 7 bar pressure,the supercontinuum spectrum spans multiple octaves from 400 nm to 5000 nm. Furthermore, the influence ofbending on the ultrafast nonlinear pulse propagation dynamics is investigated for two types of HC-AR fibers(nested and non-nested capillaries). Our results predict similar nonlinear dynamics for both fiber types and asignificant reduction of the spectral broadening under tight bending conditions.

Analytical study on the stimulated Ramanscattering threshold in distributed-pumpedfiber amplifiers

Heting Du, Jianqiu Cao, Heng Chen, Zhihe Huang, and Jinbao Chen

Doc ID: 355564 Received 17 Dec 2018; Accepted 26 Jan 2019; Posted 30 Jan 2019  View: PDF

Abstract: In this paper, the Stimulated Raman Scattering (SRS) threshold of thedistributed-pumped fiber amplifier consisting of multiple sub-amplifiers is analytically studiedbased on the rate-equation model. The SRS threshold formula is presented whose predictionsagree well with the numerical results. With the help of the formula, the effect of pumpingscheme on the SRS suppression of distributed-pumped fiber amplifier is systematicallyinvestigated. It is found that with a given number of pump injection ports, the SRSsuppression can be optimized by making only some of sub-amplifiers counter-pumped withthe others bi-directional pumped. It is also suggested that the first sub-amplifier should beadopted to be counter-pumped for suppressing SRS if only one sub-amplifier can besingle-directional pumped. The variation of SRS threshold with the number of sub-amplifiersis also discussed in detail. We believe that these results can provide significant guidance onunderstanding and designing of distributed-pumped fiber lasers and amplifiers

Parabolic-cylinder-like Long-Period Fiber GratingSensor Based on Refractive Index ModulationEnhancement Effect

Yun-Shan Zhang, Weigang Zhang, Yanxi Zhang, Lin Yu, Ling Xin Kong, Tieyi Yan, and LEI CHEN

Doc ID: 352294 Received 19 Nov 2018; Accepted 25 Jan 2019; Posted 30 Jan 2019  View: PDF

Abstract: A Parabolic-cylinder-like Long-Period Fiber Grating (PCL-LPFG) is designed and experimentally fabricatedsuccessfully by CO2 laser for the first time. The PCL-LPFG consists of an array of non-planar PCL-shaped grids. Thetheoretical model of PCL-LPFG shows that the PCL grid enables to enhance the refractive index (RI) modulationefficiency and changes the mode coupling characteristics. The experimental results show that the strain sensitivityis 1.6 pm/με in the range of 0 to 3010 με, which is fourfold compared to the conventional LPFG, and its RIsensitivity is as high as 1422.69 nm/RIU and 456.44 dB/RIU, respectively. The sensitivities of the PCL-LPFG can befurther improved by optimizing the characteristic parameters of the grating. What’s more, the resonantwavelength of the PCL-LPFG can be continuously tuned by temperature.

Coupling Efficiency of Light Intensity from theBlackbody Cavity into a Cone-shaped OpticalFiber

Xiaohua Lei, Lei Xie, Lianshan Qi, and Weimin Chen

Doc ID: 348691 Received 22 Oct 2018; Accepted 25 Jan 2019; Posted 28 Jan 2019  View: PDF

Abstract: High temperature blackbody radiation can provide the light source for broad-bandfiber sensing systems. To improve coupling efficiency, a coupling model of light intensityfrom the blackbody cavity into a cone-shaped optical fiber was proposed. Influence ofparameters of cone-shaped fiber and blackbody cavity on coupling efficiency of lightintensity was analyzed. Results show that coupling efficiency firstly decreases and thenincreases with the increase of the angle of cone-shaped fiber. When angle of cone is around30°, coupling efficiency reaches the maximum. Cone-shaped fibers with angles around 8.8°,19.4° and 27.4° were fabricated by chemical etching. Experiments were carried out withcone-shaped fibers and a fiber with flat end face. Results show that compared with the fiberwith flat end face., coupling efficiency of cone-shaped fiber with angle around 8.8° is lower,cone-shaped fiber with angle around 19.4° is almost the same, cone-shaped fiber with angle27.4° is much stronger and efficiency is improved by approximately 38%. The experimentalresults are consistent with the theoretical analysis.

High-repetition-rate burst-mode-laser diagnostics of an unconfined lean premixed swirling flame under external acoustic excitation

Sirui Wang, Xunchen Liu, Guoqing Wang, LiangLiang Xu, Lei Li, yingzheng liu, Zheng Huang, and Fei Qi

Doc ID: 352289 Received 19 Nov 2018; Accepted 25 Jan 2019; Posted 25 Jan 2019  View: PDF

Abstract: Lean premixed, swirling flames are important in practical combustors but a commonly encountered problem of practical swirl combustors is thermo-acoustic instability which may cause internal structure damages of combustors. In this research, high repetition rate burst mode laser is used for simultaneous particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) measurement in an unconfined acoustically excited swirl burner. The time-resolved flow field and transient flame response to the acoustic perturbation are visualized at 20 kHz, offering insight into the heat release rate oscillation. The premixed mixture flow rate and acoustic modulation were varied to study the effects of Reynolds number, Strouhal number, and modulation amplitude on the swirling flame. The results suggest that Strouhal number has a notable effect on the periodic movements of inner recirculation zone and swirling flame configuration.

Polarization dependence of graphene-optical fiberhybrid Mach-Zehnder interferometer

Lijun Li, Weikang Jia, Yilin Liu, Yinming Liu, Lin Xu, Fei Yu, Tianzong Xu, Fengjuan Wei, and Xingchen Gu

Doc ID: 351981 Received 14 Nov 2018; Accepted 25 Jan 2019; Posted 28 Jan 2019  View: PDF

Abstract: Graphene exhibits particularly optical polarization dependence property, which is shown as that supportingoptical polarization states of the graphene can be readily altered through tuning the polarity of the imaginary partof its conductivity. In-fiber Mach-Zehnder interferometer (MZI) possesses extremely high sensitivity to thesurrounding refractive index through cladding modes. Combining graphene and in-fiber interferometer, agraphene-optical fiber hybrid MZI is constructed. Depending on the graphene polarization dependence property,the interference wavelength of the graphene-optical fiber hybrid MZI expresses periodic drift with the in-fiber lightlinear polarization angle adjusting within 180°. Meanwhile, drift periods corresponding to different interferencewavelengths are slightly different, which is primarily due to the superposition of polarization dependencebehaviors of different cladding modes. For different light polarization state, with the in-fiber optical powerincrease, interference wavelengths and contrast intensities of the hybrid MZI transmission spectrum showspolarization independently linearly blue-shift and nonlinearly decrease, respectively.

Enhanced left/right asymmetry in reflection andtransmission due to a periodic multilayer of atopological insulator and an anisotropic dielectricmaterial

Francesco Chiadini, Vincenzo Fiumara, Akhlesh Lakhtakia, and Antonio Scaglione

Doc ID: 354707 Received 05 Dec 2018; Accepted 25 Jan 2019; Posted 28 Jan 2019  View: PDF

Abstract: Very weak left/right asymmetry in reflection and transmission is offered by a layer of a topological insulatoron top of a layer of an anisotropic dielectric material, but it can be enhanced very significantly byusing a periodic multilayer of both types of materials. This is an attractive prospect for realizing one-wayterahertz devices, because both types of materials can be grown using standard physical-vapor-depositiontechniques.

Surface plasmon resonance biosensor based ongraphene and grating excitation

kai tong, Yunxuan Wang, Fucheng Wang, jiaru sun, and Xiaogang Wu

Doc ID: 354840 Received 13 Dec 2018; Accepted 25 Jan 2019; Posted 28 Jan 2019  View: PDF

Abstract: A surface plasmon resonance biosensor based on graphene-decorated grating excitation structure is proposed in this paper. Thebiosensor consists of a three-layer structure, including a graphene layer, a grating layer, and a high refractive index layer. The materialof the grating layer is silica. The graphene is physically deposited on the grating ridges. An incident light with transverse magnetic(TM)polarized is used to excite surface plasmon in the mid-infrared spectral region, which is highly localized at both ends of the graphenelayer. The property of the sensor is improved by the high refractive index dielectric layer, which enhances the absorption of incidentlight and increases the depth of the spectra. The finite-difference time-domain (FDTD) method is used to simulate the property of thesensor. The structure of the sensor could be optimized by changing the structural parameters and comparing the simulation results.The effective refractive index(RI)on the surface and the wavelength of reflective resonance absorption peak will be changed when thesurface of graphene adsorbs the surrounding analyte. The results show that the relationship between the analyte RI and the resonancewavelength is linear. The measurement range of analyte RI is 1-1.8, the sensitivity is 2780 nm/RIU.

Turbine blade temperature error as measured with optical pyrometer under different wavelengths and blade TBCs thickness

Dong Li, Chi Feng, Ketui Daniel, Shan Gao, Liwei Chen, and Ziyang Kang

Doc ID: 355039 Received 11 Dec 2018; Accepted 25 Jan 2019; Posted 28 Jan 2019  View: PDF

Abstract: Optical pyrometer is a widely used instrument for measuring temperature of gas turbine blade targets. However, one of the limitations of this instrument is the measurement error caused by reflected radiations from high temperature surrounding environment. This paper presents an analysis of such measurement error with consideration of wavelength detection range of 2.5 μm to 22 μm with blade thermal barrier coatings (TBCs) ranging from 18 μm to 279 μm. Surface temperature distributions were simulated using software ANSYS CFX. Radiation heat transfer was calculated based on discretized triangular surface elements. The variation characteristics of relative temperature error under different wavelengths and TBCs thickness were obtained. The results obtained are well suited to providing theoretical guidance for choosing the wavelength of pyrometer when measuring blade temperature with different TBCs thickness, and can also be used to provide a method for estimating and correcting the temperature error.

Dual-Channel Inline Coherent Imaging

Faleh Altal, Troy Allen, Stephen Nestor, Tristan Fleming, and James Fraser

Doc ID: 349527 Received 19 Nov 2018; Accepted 24 Jan 2019; Posted 24 Jan 2019  View: PDF

Abstract: We present dual-channel inline coherent imaging system for laser machining monitoring using a single spectrometer. Dual-channel detection sensitivity equivalent to the added sensitivity of the two input channels was demonstrated with maximum sensitivity of 99 dB at 73 kHz acquisition rate. We also treat, theoretically and experimentally, dual-channel detection in the case of signal saturation. A method to mitigate saturation artifacts while maintaining high signal to noise ratio is shown.

An image-guided vibrometry systemintegrated with spectral and time domainoptical coherence tomography

Cuixia Guo, Xiaojie Yang, Jianping Wu, Xiaorui Guo, Yonghong He, Zhiyuan Shen, Zhan Sun, Tian Guan, and Fangyi Chen

Doc ID: 351447 Received 07 Nov 2018; Accepted 24 Jan 2019; Posted 24 Jan 2019  View: PDF

Abstract: Vibrometry using optical coherence tomography (OCT) can provide valuableinformation for investigating either the mechanical properties or the physiological function ofbiological tissues, especially the hearing organs. Real-time imaging of the measured tissuesprovides structure imaging and spatial guidance for and thus highly demanded by suchvibrometry. However, the traditional time domain OCT (TD-OCT) systems, although capableof subnanometric vibrometry at big ranges of frequencies, are unable to offer an imagingspeed that is high enough to acquire depth-resolved images for guidance. The spectral domainOCT (SD-OCT) systems, although allowing image-guided vibrometry, are challenged inmeasuring vibration at high frequencies, particularly for scattering tissue specimens thatrequire longer exposure time to ensure imaging and vibrometry performance. This is becauseof their limit in the line-scan rate of the CCD, in which the maximum resolvable frequencymeasured by the SDOCT is about 1/4 of the CCD line-scan rate in practice. In the presentstudy, we have developed a dual-mode OCT system combining both SD-OCT and TD-OCTmodalities for image-guided vibrometry, as the SD-OCT can provide guiding structuralimages in real time and, moreover, the TD-OCT can guarantee vibrometry at big ranges offrequencies, including high frequencies. The efficacy of the developed system in imageguidedvibrometry has been experimentally demonstrated using both piezoelectric ceramictransducer (PZT) and ex vivo middle-ear samples from guinea pigs. For the vibrometry ofPZT, the minimum detectable vibration amplitude was able to reach ~0.01 nm. For thevibrometry of the sound-evoked biological samples, both real-time two-dimensional imagingand subnanometric vibrometry were performed at the frequency ranging from 1 to 40 kHz.These results indicate that our dual-mode OCT system is able to act as an excellentvibrometer enabling image-guided high-frequency measurement.

Dual-wavelength Terahertz sensing based onanisotropic fano resonances metamaterials

Yuying Lu, Maosheng Yang, Zhang Zhang, Lanju Liang, Jining Li, and Jian-Quan Yao

Doc ID: 351582 Received 13 Nov 2018; Accepted 22 Jan 2019; Posted 24 Jan 2019  View: PDF

Abstract: Higher-order Fano resonance metamaterials provide a desirable platform for biosensing applications. In this workwe exhibit higher-order Fano modes by designing elliptical metallic ring. The simulation results show that for Fanoresonant metamaterials, the higher-order modes lead to improved sensitivity to the refractive index change andlarger frequency shifts. Numerically, the sensitivity of dip A (quadrupole mode) is 112 GHz/ RIU, whereas thesensitivity of dip B (octupole mode) is 4 GHz/RIU, over 2 times than that of dip A. According to our experimentalresults, the Fano resonant frequencies of dip A and dip B exhibit redshift as the concentration of the anti-cancerdrug, methotrexate, decreases from 120 to 90 μM, with the cell analyte concentration of A549 cells at 5×105cell/ml. For dip A (quadrupole mode), there is a frequency shift of 0.84 GHz for the drug concentration of 120 μMand a frequency shift of 22 GHz for 90 μM drug-treated sample. For dip B (octupole mode), there is a frequency shiftof 6.767 GHz for the drug concentration of 120 μM treated sample and a frequency shift of 51.815 GHz for the drugconcentration of 90 μM treated sample. Furthermore, the frequency shift of dip A is always smaller than that of dipB for both 90 μM and 120 μM drug concentrations. Such phenomena indicate that dip B is much more sensitive thandip A. The enhanced sensitivity of higher-order Fano metamaterials makes it possible to realize high-performanceterahertz sensing for biomedical applications.

Bismuth quantum dots as an optical saturable absorber for 1.3 μm Q-switched solid-state laser

Xian-cui Su, Yiran Wang, Baitao Zhang, Han Zhang, Kejian Yang, ruihua Wang, and Jingliang He

Doc ID: 353137 Received 29 Nov 2018; Accepted 22 Jan 2019; Posted 24 Jan 2019  View: PDF

Abstract: Two-dimensional (2D) bitmusth has attracted extensive attention for its unique properties such as, moderate bandgap, high carrier mobility and high stability. In this work, uniformly bismuth quantum dots saturable absorber (BiQDs-SA) was successfully fabricated by liquid phase exfoliation method. It was successfully employed in a passively Q-switched bulk lasers operating at the telecommunication wavelength of 1.3 μm. The as-fabricated BiQDs-SA based 1.3 μm Q-switched laser not only exhibits low timing jitter but also shows long-term stability for several days. The maximum average output power of 125 mW was obtained with the shortest pulse width of 510 ns and the repetition rate of 135 kHz, corresponding to the single pulse energy and pulse peak power of 0.9 µJ and 1.8 W, respectively. The results indicate that BiQDs has the potential to be used for passive Q-switching laser generation at 1.3 μm wavelength.

Enhancement of electric and magnetic dipole transition of rare-earth doped thin filmstailored by high-index dielectric nanostructures

Peter Wiecha, Clément Majorel, Christian Girard, Arnaud Arbouet, Bruno Masenelli, Olivier Boisron, Aurélie Lecestre, Guilhem Larrieu, Vincent Paillard, and Aurélien Cuche

Doc ID: 349399 Received 26 Oct 2018; Accepted 22 Jan 2019; Posted 24 Jan 2019  View: PDF

Abstract: We propose a simple experimental technique to separately map the emission from electric andmagnetic dipole transitions close to single dielectric nanostructures, using a few nanometer thinfilm of rare-earth ion doped clusters. Rare-earth ions provide electric and magnetic dipole transitionsof similar magnitude. By recording the photoluminescence from the deposited layer excitedby a focused laser beam, we are able to simultaneously map the electric and magnetic emissionenhancement on individual nanostructures. In spite of being a diffraction-limited far-field methodwith a spatial resolution of a few hundred nanometers, our approach appeals by its simplicity andhigh signal-to-noise ratio. We demonstrate our technique at the example of single silicon nanorodsand dimers, in which we find a significant separation of electric and magnetic near-field contributions.Our method paves the way towards the efficient and rapid characterization of the electric andmagnetic optical response of complex photonic nanostructures.

Design of a head-up display based on freeform reflective systems for automotive applications

ShiLi Wei, Zichao Fan, Zhengbo Zhu, and Donglin Ma

Doc ID: 349452 Received 29 Oct 2018; Accepted 22 Jan 2019; Posted 24 Jan 2019  View: PDF

Abstract: Automotive head-up display (HUD), a typical application in augmented reality (AR), has gained popularity in recent years. In this paper, we propose a novel design configuration of freeform off-axis three-mirror systems for automotive head-up display (HUD) application. In the configuration, the image source, the flat mirror and the freeform mirror are allocated on the same horizontal level to guarantee a compact structure as well as to make the optical elements easy to be assembled. The whole design philosophy and procedure including analytic method to determine initial structure, structure constraints and optimization strategy are demonstrated in details. Superior optical performance is achieved regardless of the pupil located at any position inside a rectangular eye box.

INFLUENCE OF TOOL EDGE WAVINESS ON THEDIFFRACTION EFFECT OF DIAMOND TURNED OPTICS:THEORETICAL SIMULATION AND EXPERIMENTALVALIDATION

Chunlei He, Sujuan Wang, W.J. Zong, and site zhang

Doc ID: 352652 Received 26 Nov 2018; Accepted 21 Jan 2019; Posted 25 Jan 2019  View: PDF

Abstract: In this work, the influence of tool edge waviness on the diffraction effect ofdiamond turned optics is simulated theoretically and further validated experimentally. Insimulation, a 3D surface topography model with consideration of the influence of tool edgewaviness is established, in which the variation of tool edge profile is estimated by a linearmodel in relation to the cutting distance. The results show that the diffraction effectrepresented in simulation is consistent with the experimental observation. With thedeterioration of tool edge waviness, the diffraction efficiency of the specular light decreases,but the high-order diffracted light intensively distributes in the horizontal direction on thereceiving screen. Such observation can be attributed to the sub-grating effect induced by theperiodic duplication of tool edge profile on the machined surface, which heavily depends onthe deterioration of tool edge waviness. Finally, a waviness-controlled diamond tool isrecommended to finish a diffraction-free optics by the diamond turning process. Moreover,the diffraction effect can also be employed to monitor the dynamic wear of the cutting tool indiamond turning.

Numerical investigations of synchronization andcommunication based on electrooptical phase chaossystem with the concealment of time-delay

Qiliang Li, DeWang Chen, Qi Bao, Ran Zeng, and Miao Hu

Doc ID: 355130 Received 13 Dec 2018; Accepted 20 Jan 2019; Posted 23 Jan 2019  View: PDF

Abstract: A modified electrooptical phase chaos system, which can conceal the time-delay and allows for unidirectionaltransmission of message, is numerically investigated. The configuration includes two cascaded delay loops, theparallel-coupled microresonators (PCMRs) in one of two loops result in a frequency-dependent group delay. Thelargest Lyapunov exponent (LLE), Lempel-Ziv complexity (LZC) and permutation entropy (PE) are used todistinguish the chaotic behavior and the complexity degree of a time series, and the autocorrelation function (ACF)and the delayed mutual information (DMI) are plotted to extract the time delay (TD). From the correspondingdiagrams we find that in the novel electrooptical system not only the phase chaos with high complexity can occurwithin a certain range of feedback strength, but also at a fixed feedback strength the effect of the time-delayconcealment becomes quite good with the increase of the numbers of PCMRs. The Numerical simulation alsoreveals that the delayed chaotic dynamics can be identically synchronized and the synchronization solution isrobust. Moreover, basing on the coherence of Mach-Zehnder interferometers, we convert the phase variations ofthe outputs of the transmitter and the receiver into the corresponding intensity variations, as a result thesynchronization error of two phase chaotic series can be monitored. At last, we can successfully decipher themessage introduced on the transmitting end of a link. In this scheme, the feedback time delay has been concealedto prevent eavesdropper from listening in it, so the proposed chaotic communication system is secure.

Tm3+ doped silica glass fiber for ~2μm fiber laser

Yu Lu, Gaofeng Feng, Meng Wang, Lei Zhang, Junyong Yang, and Junjie Zhang

Doc ID: 356301 Received 28 Dec 2018; Accepted 20 Jan 2019; Posted 23 Jan 2019  View: PDF

Abstract: Tm3+ doped silica glass preforms were fabricated by MCVD process combined with the solution doping technique. Its spectroscopic properties were evaluated according to the detected absorption and fluorescence spectra. The calculated maximum emission cross-section of Tm3+ ions in this core glass is 5.66×10-21 cm2 and tested fluorescence lifetime is 544 μs at 1816 nm. According to the theory of Dexter and Forster, the cross-relaxation rate was calculated by the integral overlap of absorption and emission cross-sections. Double cladding fiber with core NA of 0.14 was prepared by high temperature drawing. Maximum 14.5 W fiber laser output center slope efficiency of50.6% was obtained from a 4.5-m-length double cladding fiber.

Deep Learning Control Model for Adaptive OpticsSystems

zhenxing xu, ping yang, Ke Hu, Bing Xu, and HE-PING LI

Doc ID: 345676 Received 13 Sep 2018; Accepted 20 Jan 2019; Posted 24 Jan 2019  View: PDF

Abstract: To correct wavefront aberrations, commonly employing proportional-integral (PI) control in adaptive optics(AO) systems, the control process depends strictly on the response matrix of the deformable mirror. Thealignment error between the Hartmann-Shack (HS) wavefront sensor and the deformable mirror is caused byvarious factors in AO systems. In the conventional control method, the response matrix can be recalibrated toreduce the impact of alignment error, but the impact cannot be eliminated. This paper proposes a controlmethod based on a deep learning control model (DLCM) to compensate for wavefront aberrations, eliminatingthe dependence on the deformable mirror response matrix. Based on the wavefront slope data, the costfunctions of the model network and the actor network are defined, and the gradient optimization algorithmimproves the efficiency of the network training. The model network guarantees the stability and convergencespeed, while the actor network improves the control accuracy, realizing an online identification and selfadaptivecontrol of the system. A parameter-sharing mechanism is adopted between the model network andthe actor network to control the system gain. Simulation results show that the DLCM has good adaptability andstability. Through self-learning, it improves the convergence accuracy and iterations, as well as the adjustmenttolerance of the system.

Self-Beating Resonant Optical Gyroscopewith ‘Reflector’: Possibility of HighSensitivities at Reduced Costs

SUMUKH NANDAN RAGHUNANDAN, SAROJ POUDYAL, Shailesh Srivastava, and Gowrishankar Ramadurai

Doc ID: 345589 Received 11 Sep 2018; Accepted 19 Jan 2019; Posted 23 Jan 2019  View: PDF

Abstract: Using simulations and theoretical analysis, we present an innovative readouttechnique, which uses the change in a beat frequency signal, for sensing rotation in theresonant fiber gyroscope with “reflector”. Unlike traditional fiber optic gyros, thisgyroscope uses an embedded reflecting element that deliberately couples the clockwiseand counter clockwise propagating waves, for sensing rotation. Our analytical resultspredict increased immunity to the degrading effects of backscattering, Kerr-nonlinearitiesand ambient variations at an optimum non reciprocal bias. Using just a few meters offiber and without requiring a very narrow linewidth source, sensitivities below 1 deg/h,along with a dynamic range greater than 106 deg/h are predicted. The technique has thepotential to provide a cost effective solution in the tactical grade.

Rapid identification of rice species by Laser-inducedBreakdown Spectroscopy combined with pattern recognition

ZIYI LUO, LINYING zhang, Tianbing Chen, Muhua Liu, Jinyin Chen, Huamao Zhou, and Mingyin Yao

Doc ID: 348730 Received 22 Oct 2018; Accepted 19 Jan 2019; Posted 23 Jan 2019  View: PDF

Abstract: Laser-induced breakdown spectroscopy (LIBS) combined with pattern recognition was proposed to discriminate ricespecies. The LIBS spectra at the range of 210-480 nm wavelength from 11 different rice species were collected andpreprocessed. Principal component analysis (PCA) was applied to extract the characteristic variables from LIBS spectral data.Three pattern recognition methods including discriminant analysis (DA), radial basis function neural network (RBF), and multilayerperceptron neural network (MLP) were performed to compare the precision in identifying rice species. The results showedthat the performance of MLP model was better. The average identification rate of rice species reached 100% and 97.9% in thetraining and test sets, respectively by MLP. And the highest and lowest percentage for correct identification were 100% forEarly indica rice, Huai rice 5, Yan japonica 6, Lian japonica 8, Xuhan1, Lvhan 1, Sheng rice16, Yang japonic687, Fenghan 30,and 77.8% for Wuyu Japonica rice respectively in test set. The overall results demonstrate that LIBS combined with MLP couldbe utilized to rapidly discriminate rice species.

Numerical-experimental study on polishing of siliconwafer using Coupled FE-SPH

mohammad mosavat and Abdolreza rahimi

Doc ID: 348922 Received 22 Oct 2018; Accepted 18 Jan 2019; Posted 23 Jan 2019  View: PDF

Abstract: The quality and surface roughness of silicon wafers significantly affects the efficiency and quality of follow-upprocessing. Smoothed particle hydrodynamics (SPH) is a robust meshless method with good self-adaptability thatcan be used in the simulation of polishing process which has high speed deformation characteristics. In this study,the coupled algorithm of Finite Element (FE) and SPH has been used to simulate the surface polishing ofmonocrystalline silicon wafers with Magnetic Abrasive Finishing (MAF) process. The effects of machining gap,abrasive particle size, and rotational speed on surface roughness are comprehensively analyzed. In addition,several experiments are carried out on a 3-inch-diameter circular silicon wafer and the results are compared withthe simulation results. Our findings show that the decreases in abrasive particle size and also increases inrotational speed significantly decline the surface roughness of the silicon wafer. The obtained results revealed thatthe machining gap has an optimum condition in which the minimum surface roughness is achieved. According toour results, the best surface roughness value achieved is 63nm.

Advances and Challenges of Soft Contact Lens Design for MyopiaControl

Qing Li and Fengzhou Fang

Doc ID: 352617 Received 21 Nov 2018; Accepted 18 Jan 2019; Posted 23 Jan 2019  View: PDF

Abstract: Myopia has shown a rapid increase during the past decades around world, posing great threatto ocular health. Myopia is mostly attributed to an overgrowth of the axial length of the eye,which is an abnormal growth of the sclera that is attributed to a series of environmental andgenetic factors and their interactions. Soft contact lenses have the potential to be an idealmethod of correction for slowing myopic progression. This paper serves as a comprehensivereview of the state-of-the-art in the field of soft contact lens design for myopia control. Theknowledge gaps are identified in designing the contact lenses and the challenges are alsopresented that would be faced in the future development.

Characterization of cyclical Spatial HeterodyneSpectrometers for astrophysical and planetary studies

Sona Hosseini

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

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

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

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

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

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

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

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

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

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

Shifting Colored Coded Apertures Design for SpectralImaging

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

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

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

Photoanisotropic-copies-based pattern recognition system

Barbara Kilosanidze, George Kakauridze, and Irine Kobulashvili

Doc ID: 349989 Received 02 Nov 2018; Accepted 04 Jan 2019; Posted 30 Jan 2019  View: PDF

Abstract: A method of pattern recognition is presented which is based on obtaining photoanisotropic copies of the object images. Such a copy is induced on the dynamic polarization-sensitive material when the amplitude image of the object formed by SLM is transilluminated by a linearly polarized light with a wavelength actinic for the used material. In this case the distribution of the intensities over the amplitude image is converted into the distribution of photoanisotropy over the sample of the polarization-sensitive material. In recognition process, this copy is illuminated by parallel circularly polarized nonactinic light. The distribution of elliptical polarization occurs directly behind a photoanisotropic copy and it reduces to a summary ellipse in the Fraunhofer diffraction region. It is shown that the parameters of this ellipse are related to the characteristics of the object and uniquely identify the initial object. The polarization-holographic diffraction element developed by us enables to determine the polarization state of a summary ellipse - to obtain all the Stokes parameters in real time. The obtained results have been compared with the Stokes parameters of the recognizable object in database. The method invariance to position, scale and rotation of pattern were investigated. The resolution and sensitivity of this method were determined. The polarization-sensitive materials used to obtain copies are reversible, with practically unlimited number of recording-deleting cycles. To obtain a photoanisotropic copy of another object on the same material, the previous copy should be deleted with a pulse of circularly polarized actinic light, and then a next copy can be recorded. A laboratory model of the recognition device and the appropriate software were created. A theoretical model was developed. Databases have been obtained for the various objects images.

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

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

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

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

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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