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Label-free color staining of quantitative phase imagesof biological cells by simulated Rheinberg illumination

Xin Fan, John Healy, Kevin Dwyer, and Bryan Hennelly

Doc ID: 352599 Received 21 Nov 2018; Accepted 18 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: Modern microscopes are designed with functionalitiesthat are tailored to enhance image contrast. Darkfieldimaging, phase contrast, differential interferencecontrast, and other optical techniques enable biologicalcells and other phase-only objects to be visualised.Quantitative phase imaging refers to an emerging setof techniques that allow for the complex transmissionfunction of the sample to be measured. With this quantitativephase image available, any optical techniquecan then be simulated; it is trivial to generate a phasecontrast image or a DIC image. Rheinberg illumination,proposed almost a century ago, is an optical techniquethat applies color contrast to images of phase only objectsby introducing a type of optical staining via anamplitude filter placed in the illumination path thatconsists of two or more colors. In this paper, the completetheory of Rheinberg illumination is derived, fromwhich an algorithm is proposed that can digitally simulatethe technique. Results are shown for a numberof quantitative phase images of diatom cells obtainedvia digital holographic microscopy. The results clearlydemonstrate the potential of the technique for labelfreecolor staining of sub cellular features.

A low-index-mode photonic crystal nanobeam cavityfor refractive index sensing at 2 μm wavelength band

Penghui Dong, Daoxin Dai, and Yaocheng Shi

Doc ID: 356820 Received 04 Jan 2019; Accepted 18 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: We present the design, fabrication, and characterization of one-dimensional photonic crystal (1D-PhC) low-index- mode nanobeam cavity on the silicon-on-insulator platform for refractive index sensing at 2 μm wavelength band. A Q-factor of 4. 35 × 105 and an effective mode volume of Veff ~1. 95(1/nSi)3 is theoretically achieved. The measured he device immersed in NaCl solutions with different mass concentrations demonstratesa sensitivity of 326.1 nm/RIU and a Q-factor of ~1144.

Efficient Tm:YAG and Tm:LuAG lasers pumped by 681-nm tapered diodes

ERSEN BEYATLI, Bernd Sumpf, Goetz Erbert, and Umit Demirbas

Doc ID: 360774 Received 25 Feb 2019; Accepted 18 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: In this paper, we present highly-efficient continuous-wave (cw) laser operation of Tm:YAG and Tm:LuAG lasers pumpedby high-brightness red tapered diodes. The single-emitter tapered diode lasers (TDLs) provide up to 1-W of pumppower around 680 nm. By adjusting the operation temperature of the TDL, the pump central wavelength could bematched to the strong absorption peak of Tm3+ ions in this region (3H63F3 excitation). This absorption peak is around3-fold stronger than the usually employed 785 nm transition (3H63H4) . In the cw laser experiments, we have achievedslope efficiencies exceeding 55% at room temperature, which is far above the stokes limited slope efficiency (34%),indicating presence of strong two-for-one cross-relaxation process. Pumping with high-brightness tapered diode lasersfurther facilitated usage of smaller pump spots (enabling quite low lasing thresholds) and generation of near-diffractionlimited output beam profiles from standard z-type cavities. To the best of our knowledge, this is the first report of diodepumping of Tm-doped solid-state lasers around 680 nm, as well as the first usage of TDLs as pump sources in Tm-dopedlaser systems.

Band Selection Method for Sub-pixel Target DetectionUsing Only the Target Reflectance Signature

Sanghui Han, John Kerekes, Shawn Higbee, Lawrence Siegel, and Alex Pertica

Doc ID: 356680 Received 03 Jan 2019; Accepted 17 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: While offering powerful capabilities, the high dimensionality of hyperspectral images can make informationextraction a challenge. For that reason, dimension reduction is a common data processing step. Forthe purpose of sub-pixel target detection, band selection is a dimension reduction method that can optimizeresults as well as reduce computation costs. However, existing band selection methods that are usedfor sub-pixel target detection require background spectral reflectance signatures to compare with the targetsignatures. These methods work well and offer a distinct advantage over other dimension reductionmethods such as PCA or NMF, but only when the background information is available. In this study, wedeveloped a method that selected bands using only the the target spectral reflectance signature. We testedthis method using a utility prediction model, validated the results with real images, then cross-validatedthe results with simulated images that were associated with perfect truth data. We studied the detectionstatistics for a range of bands selected using this method and compared it to the results obtained fromthree other band selection methods. The motivation for developing this method was to be able to reducethe number of bands prior to collection when background information was not available. For an adaptivespectral imaging system with a tunable sensor, we would be able to optimize detection for a specifictarget, and save data handling costs associated with transmitting, storing and disseminating the data forinformation extraction. This method was also simple enough to be computed using a small on-boardCPU, and modify the bands selection criteria as the target changed.

Sensitive Determination of DNA Based onPhosphate-Dye Interaction Using PhotothermalLens Technique

Nader Shokoufi, Behnaz Abbasgholi Nejad Asbaghi, and Shafigh Nouri

Doc ID: 356138 Received 07 Jan 2019; Accepted 16 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: Photothermal lens spectrometry is a powerful optical detection technique that can be used to investigatebiomolecules. In this work, for the first time, photothermal lens spectrometry was used for determination of nanomolarconcentrations of three distinct DNAs using methylene blue as a labeling dye. Methylene blue interacts withphosphate groups of the DNA in lower DNA concentrations. It was observed that phosphate- methylene blueinteraction had no obvious effect on methylene blue absorption and fluorescence spectra, however photothermallens spectrometry signal of methylene blue increased with DNA concentration. For this purpose, to evaluate theperformance of the presented method, Herring Sperm DNA, Escherichia coli bacteria DNA, and partial 16S rRNAgene were examined. Under optimum conditions, photothermal lens spectrometry intensity of methylene blueincreased linearly with DNA concentration when herring sperm DNA, Escherichia coli DNA and 16S rRNA geneconcentrations increased in the ranges of 0.1–250, 1–700, and 1-800 nmol L−1, respectively. The correspondingdetection limits were found to be 0.07, 0.71, and 0.56 nmol L−1, respectively, and relative standard deviations for 50nmol L−1 of the tested samples were 2.59, 4.95, and 4.57%, respectively.

Grating couplers fabricated by e-beam lithography forlong-range surface plasmon waveguides embedded ina fluoropolymer

Zohreh Hirbodvash, Maryam Khodami, Norman R.Fong, Ewa Lisicka-skrzek, Anthony Olivieri, Howard Northfield, R.Niall Tait, and Pierre Berini

Doc ID: 356550 Received 08 Jan 2019; Accepted 15 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: Long-range surface plasmon polariton waveguides consisting of Au stripes integrated with input andoutput grating couplers embedded in thick Cytop claddings are proposed and demonstrated experimentally.Under the right conditions, grating couplers enable broadside (top) coupling with good efficiencywhile producing a low level of background light. The scheme does not require high-quality input andoutput edge facets, and simplifies optical alignments. We demonstrate coupling using a cleaved bow-tiefiber and a lensed fiber, and determine the grating coupling efficiencies in both cases over a broad operatingwavelength range. The lensed fiber produces a better overlap with the long-range surface plasmonmode of interest and thus results in a better coupling efficiency with essentially no background light asobserved on an infrared camera. The measurements are compared with theoretical results obtained usinga realistic model of the structures, including out-of-plane curvature in the grating profile resulting fromour fabrication process. The coupling scheme along with the surface plasmon waveguides hold strongpotential for biosensing applications.

Gain manipulation of a slotted sphere using generalbi-isotropic coating

zeeshan awan

Doc ID: 352613 Received 21 Nov 2018; Accepted 15 Mar 2019; Posted 15 Mar 2019  View: PDF

Abstract: The gain characteristics of a general bi-isotropic coated slotted sphere has been studied using numericalcalculations. An eigen-function expansion method has been used to derive analytical expressions forthe radiated electric and magnetic fields. The effects of various bi-isotropic and Tellegen coatings uponthe gain pattern are investigated. It is proven that chirality and Tellegen parameters of the coating cansignificantly modify the gain. It is found that a lossless bi-isotropic coating has the highest gain in theforward direction as compared to lossless dielectric, Tellegen and chiral coatings. Such type of enhancedgains in the forward direction are desirable for point to point communication. It is further shown that theTellegen coating guides most of the radiated field from the slot towards polar directions and reduces thegain in the forward direction provided that the Tellegen parameter is not close to unity. For a Tellegencoating whose Tellegen parameter is close to unity, the maximum gain in the forward direction is found.The proposed theory is also extended to realistic bi-isotropic and low-loss dielectric coatings. It is investigatedthat using proper selection of coating thickness, the forward direction gain of realistic bi-isotropiccoating can be enhanced or diminished as compared to low loss dielectric coating.

Combinatorial approach towards optimization of thelight emission intensity of AlOxNy:Yb3+ thin films

Karem Tucto, Wilson Aponte, Jorge Dulanto, Jan Amaru Tofflinger, Jorge Guerra Torres, and Rolf Grieseler

Doc ID: 356568 Received 02 Jan 2019; Accepted 15 Mar 2019; Posted 15 Mar 2019  View: PDF

Abstract: To obtain an adequate luminescent emission, commonly a significant effort must be made to find asuitable host material. An interesting and highly efficient method is a combinatorial approach, whichallows a high velocity screening of a wider range of properties. In the present work a compositionalgradient based thin film library of a-AlOxNy:Yb3+ has been prepared by radio frequency co-sputteringfrom two targets. The ytterbium concentration range spreads from 0.9 to 4.2 at.% and the oxygen tonitrogen ratio from 0.6 to 3.6. Using different annealing temperatures the activation energy of the rareearth ions and activation mechanisms can be evaluated. Finally, optimal elemental compositions in theinvestigated range are proposed.

Comparative study of one-step and two-stepquantitative fluorescence photoacoustictomography

prabodh pandey, Omprakash Gottam, Naren Naik, and Asima Pradhan

Doc ID: 352460 Received 20 Nov 2018; Accepted 15 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: Fluorescence optical tomography (FOT) is a well known imaging technique, wherefluorescent biological markers are injected to tag targeted tissues (tumors, proteins) and theabsorption coefficient of fluorophore is reconstructed to provide contrast enhanced images.Conventional FOT is known to have lack of stability to noise and shallow imaging depth dueto strong optical scattering in biological tissue. Photoacoustic tomography (PAT) has beenpreviously proposed to combine with FOT to resolve this issue. We propose a fully nonlinear onestepreconstruction in a diffuse-approximation modelled fluorescence photoacoustic tomographic(FPAT) setting, where the absorption coefficient of exogenous fluorophore is recovered directlyfrom the photoacoustic data. Computational validations in two-dimensions in single and dual-gridreconstruction settings using full as well as partial data have been provided in support of theproposed algorithm. One-step schemes are particularly useful with respect to dual-representationsof field (optical and pressure) variables and optical parameters, especially in the limited datasettings, that effectively helps constraining the optimization search space. We have comparedthe results of one and two-step FPAT schemes and concluded that the one-step reconstructionsare superior as compared to the corresponding two-step reconstructions. To the best of ourknowledge these are the first comparisons of one-step and two-step reconstructions in FPAT.

Wavefront shaping optical elements recordedin photo-thermo-refractive glass

Ivan Divliansky, Fedor Kompan, Evan Hale, Marc SeGall, Axel Schulzgen, and Leonid Glebov

Doc ID: 355481 Received 17 Dec 2018; Accepted 14 Mar 2019; Posted 14 Mar 2019  View: PDF

Abstract: The paper presents an overview of the benefits of recording phase masks into thebulk of photo-thermo-refractive glass. We demonstrate that both binary and greyscale phasemasks can be encoded into the medium, and that such masks can be used for mode conversionand beam shaping with near-theoretical efficiency. We further demonstrate that by encodingthe phase mask profile into a transmitting volume Bragg grating, it is possible to createtunable and achromatic phase masks without requiring a complex phase pattern.

Analysis of unidirectional broadbandabsorption in one-dimensionalsuperconductor photonic crystal with anasymmetric multiple-layered structure

Caixing Hu, HaiFeng Zhang, and Guo-Biao Liu

Doc ID: 362081 Received 11 Mar 2019; Accepted 14 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: In this paper, the unidirectional absorption characteristics of one-dimensional(1D) superconducting photonic crystals (SPCs) with defect layers in the terahertz (THz)frequency region are theoretically analyzed by the transfer matrix method. The arrangementof such SPCs is an asymmetric multiple-layered structure (AB)ND(BA)M (N≠M). N,M are thestack numbers, respectively. The calculated results demonstrate that, in comparison with theconventional 1D binary PCs, the unidirectional absorption region (UAR) of the proposed 1DSPCs can be significantly improved, whose relative bandwidth can approximately reach over20%. The effects of the parameters for the proposed SPCs on the UAR also are investigated.The computed results illustrate that the tailored and optimized UAR can be obtained in THzregime by tuning those parameters, as well as show us possible means to realize the THzunidirectional broadband absorber based on the SPCs.

Solar Spectrum Matching by LEDs Based onthe Influence of Driving Current on PeakWavelength

Qianbing Gong, Luyao Tang, and Muqing Liu

Doc ID: 356829 Received 03 Jan 2019; Accepted 13 Mar 2019; Posted 13 Mar 2019  View: PDF

Abstract: The technique of using monochromatic LEDs (Light-emitting diode) to simulatesunlight has developed rapidly in the past decades. In this research, we proposed a method toimprove the simulating performance based on the influence of driving current (70mA to700mA) on peak wavelength of monochromatic LEDs. The largest shift of the peakwavelength was observed in the green-light LED with 9nm (nanometer) deviation. Amodified Gaussian Formula with an additional variable, driving current I, was used tosimulate LED power spectrum, and was further employed in an optimizing algorithm toachieve solar spectrum matching by 14 types of LEDs in different peak wavelength.

Focus-free head-mounted display based onMaxwellian view using retroreflector film

Hyeongkyu Do, Young Min Kim, and Sung-Wook Min

Doc ID: 345956 Received 17 Sep 2018; Accepted 12 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: In this study, a focus-free retinal projection display based on the Maxwellian view was implemented. The displaywas constructed using simple and cost-effective passive components such as a retroreflector film, beam splitter,and a pinhole. As a part of the system, the pinhole and display serve as a pinhole projector, which projects imagesthrough a small exit pupil. The retroreflector film and the beam splitter form the conjugate image of the pinholenear an observer. By locating the center of the crystalline lens of an eye at the conjugate pinhole, the projectedimages are focused on the retina and are seldomly changed by the accommodative response of the lens. For thepractical implementation of the system, a collimating lens was used as an imaging lens combined with a pinhole.The point spread function of the system was derived to theoretically demonstrate that the system exhibits focusfreefeatures at accommodation distances of 0.25 m, 0.5 m, and 1 m. The experiments conducted to demonstratethe feasibility of the system are presented under the same accommodation condition as the analysis.

Probing complex dynamics withspatiotemporal coherence-gated DLS

Aristide Dogariu and Jose Guzman-Sepulveda

Doc ID: 355210 Received 11 Dec 2018; Accepted 12 Mar 2019; Posted 13 Mar 2019  View: PDF

Abstract: We discuss the specific features of fiber-based implementations of optical sensingtechniques based on spatio-temporal coherence-gated dynamic light scattering. This sensingapproach has a number of unique capabilities such as an effective isolation of singlescattering, a large sensitivity and high collection efficiency, and it can also operate over awide range of optical regimes while providing means for proper ensemble averaging. Wereview a number of applications in which these specific characteristics permit recoveringinformation beyond the capabilities of traditional light scattering-based techniques.

Accelerating Wavefront Sensing basedAutofocusing Using Pixel Reduction in Spatialand Frequency Domains

Jing Xu, Yan Kong, Zhilong Jiang, Shumei Gao, Liang Xue, Fei Liu, Cheng Liu, and Shouyu Wang

Doc ID: 355741 Received 18 Dec 2018; Accepted 12 Mar 2019; Posted 13 Mar 2019  View: PDF

Abstract: Wavefront sensing based autofocus method can precisely determine the focal planeonly with few captured images; however, the required phase retrieval, numerical wavefrontpropagation and in-focus determination are often time-consuming, inevitably limiting its highspeed applications. To accelerate its processing speed, the pixel reduced wavefront sensingbased autofocus (PRWSA) method is proposed: with field of interest selection as pixelreduction in spatial domain and image compression as pixel reduction in frequency domain,wavefront with less pixels can be used for autofocusing, significantly decreasing theprocessing time. With simulations, pixel reduction criteria in both spatial and frequencydomains are first determined and tested; next certificated by experiments, the PRWSAmethod is proved to be well implemented for different specimens. Considering it canprecisely locate the focal plane with simple setup, and accelerate the processing speed, thisPRWSA method can be a potential tool for high-speed autofocusing.

Passive alignment stability and auto-alignment ofmultipass amplifiers based on Fourier transforms

Karsten Schuhmann, Klaus Kirch, Andreas Knecht, Miroslaw Marszalek, Francois Nez, Jonas Nuber, Randolf Pohl, Ivo Schulthess, Laura Sinkunaite, Manuel Zeyen, and Aldo Antognini

Doc ID: 356097 Received 21 Dec 2018; Accepted 12 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: This study investigates the stability to tilts (misalignments) of Fourier-based multi-pass amplifiers, i.e.,amplifiers where a Fourier transform is used to transport the beam from pass to pass. Here, the stabilityproperties of these amplifiers to misalignments (tilts) of their optical components has been investigated.For this purpose, a method to quantify the sensitivity to tilts based on the amplifier small-signal gain hasbeen elaborated and compared with measurements. To improve on the tilt stability by more than an orderof magnitude a simple auto-alignment system has been proposed and tested. This study, combined withother investigations devoted to the stability of the output beam to variations of aperture and thermal lenseffects of the active medium, qualifies the Fourier-based amplifier for the high-energy and the high-powersector.

Rapid wide-field imaging through scattering media by digital holographic wavefront correction

Runze Li, Tong Peng, Meiling Zhou, Xianghua Yu, Peng Gao, Junwei Min, Yan long Yang, Ming Lei, Baoli Yao, Chunmin Zhang, and Tong Ye

Doc ID: 356421 Received 11 Jan 2019; Accepted 12 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: Image through scattering media has been a long standing challenge in many disciplines. One of the promising solutions to address the challenge is the wavefront shaping technique, in which the phase distortion due to a scattering medium is corrected by a phase modulation device such as a spatial light modulator (SLM). However, the wide-field imaging speed is limited either by the feedback-based optimization to search the correction phase or by the update rate of SLMs. In this report, we introduce a new method called digital holographic wavefront correction, in which the correction phase is determined by a single-shot off-axis holography. The correction phase establishes the so-called “scattering lens” which allows any objects to be imaged through scattering media; in our case, the “scattering lens” is a digital one established through computational methods. As no SLM is involved in the imaging process, the imaging speed is significantly improved. We have demonstrated that moving objects behind scattering media can be recorded at the speed of 2.8 fps with each frame corrected by the updated correction phase while the image contrast is maintained as high as 0.9. The image speed can potentially reach the video rate if the computing power is sufficiently high. We have also demonstrated that the digital wavefront correction method also works when the light intensity is low, which implicates its potential usefulness in imaging dynamic processes in biological tissues.

On-chip magnetic-free optical multi-port circulatorbased on locally linear parity-time symmetric system

fakhroddin nazari, shahab abdollahi, and Farid Samsami-Khodadad

Doc ID: 356615 Received 02 Jan 2019; Accepted 12 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: This article introduces a new type of magnetic-free optical circulator without utilizing Faraday rotator, polarizationbeamsplitter, and magneto-optic material for the first time to the best of our knowledge. The designed circulatoroperates linearly and relies on the parity-time symmetric (PTS) system. The property of the non-Hermitian system(the linear PTS system) plays the key role in the suggested optical circulator so that it can simultaneously support Nports.The proposed device is integrated, broadband, and operates in the optical telecommunication frequency band.A great value of isolation rate of 47 dB is achieved. The proposed circulator can pave the way for optical integratedcircuits and optical networks.

The application of three-dimensional confocalX-ray fluorescence equipment in surfacetopography and depth contour scanning

Zhaoying Meng, Zhujun Xiang, Zhiguo Liu, Man Chen, Kai Pan, peng Zhou, and xiaoyan lin

Doc ID: 357395 Received 10 Jan 2019; Accepted 12 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: Three-dimensional microfocus X-ray fluorescence (3D-MXRF) technology hasbeen used to determine surface topography. The surface scanning technique initiallyfacilitated surface topography reconstruction of the sample. This paper demonstrates theimproved performance of its infrastructure, including a higher-precision translationplatform, an ultrabright microfocus X-ray source and a rewritten scanning algorithm,leading to a new scanning technology that can depict the surface topography of sampleswith complex internal structures. The improved scanning technology can analyse themetal element information of layers at different depths. This paper presents studies of thesurface and depth of coins and porcelain bottles from ancient times using this technique.

Fast compensation for arbitrary focusingthrough scattering media

li zhan, Dean Liu, Aihua Yang, Jie Miao, and Jianqiang Zhu

Doc ID: 358789 Received 28 Jan 2019; Accepted 11 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: We introduce a fast compensation scheme to realize arbitrary focusing afterpropagation through a scattering sample. Theoretical analysis of the effect of cross-term onmulti-point focusing is conducted based on the transmission matrix theory. The result showsthat the cross-term influence is very significant, which needs to be considered. MultipopulationGenetic Algorithm (MPGA) is adopted to retrieve the input mode for thesuppression of the effect of cross-term. In order to realize the fast compensation and reducemeasurement noise, the off-axis holographic method is used to measure the large transmissionmatrix, which reduces the number of measurements compared with the traditional method. Inthe experiment, after retrieving the input phase, we obtain a high quality focal output and theSignal to Noise Ratio (SNR) is increased by 13.6dB.

Tunable metasurface refractive index plasmonic nanosensorutilizing ITO thin layer in near-infrared region

Fatemeh Baranzadeh and Najmeh Nozhat

Doc ID: 359424 Received 01 Feb 2019; Accepted 11 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: In this paper, a refractive index plasmonic nano-sensor with an array of metallic nano-rods has been designed innear-infrared region. The tunable sensor is based on a perfect absorber and the ITO layer has been utilized as anactive metasurface to improve the sensor performance. By applying the voltage to the ITO layer, a perfectabsorption has been obtained. Also, the sensitivity rises from 625 nm/RIU to 1125 nm/RIU (refractive index unit)and the figure of merit (FOM) is 10 times higher. Moreover, the sensor application in the field of medicine andhematology has been shown. The proposed sensor can be used to diagnose and determine anemia and malariaparasite.

Optical improvement for modulating a high flux solarsimulator designed for solar thermal andthermochemical research

Leopoldo Martínez-Manuel, Manuel Peña-Cruz, Carlos A. Pineda-Arellano, J. Gonzalo Carrillo-Baeza, and Daniel May-Arrioja

Doc ID: 359695 Received 06 Feb 2019; Accepted 11 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: his study presents the optical improvement of a High Flux Solar Simulator (HFSS) with controllableflux-spot capabilities developed for researching solar thermal and thermochemical processes. The HFSS is comprised of: seven 2.5 kWel Xenon arc lamps coupled with ellipsoidal reflectors, a servo-controlled attenuator curtain and 3-axes linear test bench. Different attenuators were designed and tested in order to identify the best curtain geometry to improve the HFSS modulation with the lowest possible radiative losses. The optical design improvement was performed with the aid of TracePro®, a Monte Carlo ray tracing software. From simulation results, radiative peak flux from 1700 to 480 kWm-2 from the focal plane to 300 mm further back was estimated without curtains. By using the attenuators, flux levels from 1570 to 92 kWm-2 at the focal plane were also estimated. An experimental validation was achieved with a single lamp-reflector unit obtaining peak flux distributions from 200 kWm-2 ± 20 kWm-2 to 97 kWm-2 ± 9.7 kWm-2 from the focal plane to 300 mm behind. Flux modulation from 170 to 1.5 kWm-2 was also measured at the focal plane using a servo-controlled curtain from full-open slats (0°) to partially close (60°). With this attenuator, introduced as the shutter of the system, the lamps or electronic rectifiers is avoided and the radiative flux is modulated with high resolution inan optomechatronical form.

Experimental investigation on acousticallyforced flame with simultaneous high-speed LIIand Stereo-PIV at 20 kHz

chen fu, Xiaoyuan Yang, Zhongqiu Li, Haodong Zhang, Yifan Yang, and Yi Gao

Doc ID: 352293 Received 19 Nov 2018; Accepted 11 Mar 2019; Posted 13 Mar 2019  View: PDF

Abstract: An ethylene-air diffusion flame was acoustically forced with frequency of 100 Hzat four amplitudes ranging from 40% to 140%. The average bulk velocity of the fuel was 0.6m/s. The soot distribution and velocity fields were measured by simultaneous twodimensionallaser-induced incandescence and stereo particle image velocimetry at 20 kHzlaser repetition rate. The LII signal was calibrated by the pulse-to-pulse laser energy variationand it has been observed that the soot regions extend along the central axis of the flame andshrink radially under acoustic forcing compared with the steady flame. And the volumefraction of soot in the acoustic forced flame decreases with increased acoustic driving. Inaddition, the PIV results reveal that the resident time is strongly associated with the formationof oval-shaped soot region which is induced by the external acoustic forcing.

Large-energy mode-locked ytterbium-dopedlinear-cavity fiber laser based on CVD-Bi2Se3as saturable absorber

Xile Han, Huanian Zhang, C Zhang, Chonghui Li, Quanxin Guo, Jinjuan Gao, Shouzhen Jiang, and yuan man

Doc ID: 356993 Received 08 Jan 2019; Accepted 11 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: We reported on the generations of pulse bunch and large-energy dark pulses in amode-locked ytterbium-doped linear-cavity fiber laser based on Bi2Se3 as saturable absorber(SA). Bi2Se3 nanosheets were successfully synthesized by chemical vapor deposition (CVD)method and transferred to the end-facet of fiber connector for proposing SA. Its saturationintensity and modulation depth were measured to be 52 MW/cm2 and 14.5%, respectively. Byinserting the Bi2Se3-based SA into the Yb-doped all fiber linear-cavity, stable pulse buncheswere observed. In addition, dark soliton operation with a maximum average output power of32.6 mW and a pulse energy of 61.8 nJ were also achieved. To the best of our knowledge, thisis the first demonstration of a dark soliton within a linear-cavity with much larger pulseenergy than previous works. Our study fully indicated that CVD- Bi2Se3 could be an excellentSA for achieving large energy pulse operations.

Design, fabrication and analysis of double layerantireflection coatings (ARC) for industrial bifacial ntypecrystalline silicon solar cells

Xia Yan, Ning CHEN, Firdaus Bin Suhaimi, Lin Zhang, Xinxin Gong, Xinyu Zhang, and Shubham Duttagupta

Doc ID: 357110 Received 08 Jan 2019; Accepted 11 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: Nowadays, monocrystalline silicon based, n-type front and back contact (nFAB) solar cells are gradually attractingmore interest from the photovoltaic (PV) industry, due to their good bifaciality and high efficiency potentials. Tofurther improve the conversion efficiency, nFAB solar cells need to make better use of solar spectrum.Conventional single layer SiNx antireflection coating (ARC) tends to have a high reflection loss for ultra-violet (UV)photons. Thus in this work, we prepare a double layer ARC structure made of SiNx/SiOx stack, deposited by plasmaenhancedchemical vapor deposition (PECVD) method. We investigate the effects of double layer ARC throughsimulation and experimental studies by fabricating bifacial nFAB cells. The results show that the implementation ofa double layer ARC helps to greatly reduce front reflection in short wavelength, and thus allow for improvement ofphotocurrent by up to 0.3 mA/cm2. As a result, the average cell efficiency of nFAB solar cells increases by absolute~0.2%.

Theoretical assessment of the OTDR detector noise onplasma current measurement in tokamaks

Rastislav Motuz, Williem Leysen, Phillippe-Jacques Moreau, Andrei Gusarov, Petr Drexler, and Marc Wuilpart

Doc ID: 356864 Received 08 Jan 2019; Accepted 11 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: In this paper, we propose a theoretical study dedicated to the assessment of plasma current measurementin magnetic confinement fusion reactors using a Polarization Optical Time-Domain Reflectometer(POTDR) setup with a low-birefringent fibre is used as the sensing fibre. We consider the general case ofa non-uniform magnetic field distribution along the sensing fibre. The numerical simulations, based onJones formalism with taking into account the OTDR noise, provide the measurement error as a functionof the plasma current. The measurement performance is evaluated for an ITER-relevant sensor configuration.We demonstrate that a signal-to-noise ratio of 6 dB, achievable in modern POTDRs, allows tocomply with the ITER requirements for plasma currents from 0 to 1 MA, while for the 1 to 20 MA rangethe level is relaxed to 4 dB.

Locally Adaptive Super-resolution Through SpatiallyVariant Interpolation

Colm Lynch, Martin Devaney, and Christopher Dainty

Doc ID: 355704 Received 18 Dec 2018; Accepted 11 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: Systems that do not meet the requirements of the sampling theorem produce images corrupted by aliasing.Higher resolution images are attainable by unfolding aliased spatial frequencies. Multiple imagesuper-resolution has seen much attention in the literature though with no clear optimum algorithm formany real-world applications. We propose a method of multi-frame super-resolution using a set of convolutionalSinc kernels, tailored to the specific shifts between images, capable of resolving up to thediffraction limit. We demonstrate our method for the case of global shifts before we treat a pixel-levelsuper-resolution.

Temporal frequency spread of optical wavespropagating in anisotropic maritime atmosphericturbulence

bing guan and Jaeho Choi

Doc ID: 355714 Received 18 Dec 2018; Accepted 11 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: Recently, the analytic expressions of the atmospheric induced frequency spreads of the optical wavespropagating in the anisotropic atmosphere turbulence have been derived in our previous work. Meanwhile,more research attentions are also drawing on the theoretical survey in the maritime atmosphericturbulence. In this paper, the new expressions of the temporal frequency spreads of the plane and thespherical waves propagating in the anisotropic maritime atmospheric turbulence are derived. Based onthose new expressions obtained, the combined effects of power law exponent, turbulence strength, turbulencescales, and the anisotropic parameter are evaluated. The analytical simulation results show thatthe turbulence strength and the anisotropic parameter significantly affect the curves of the temporal frequencyspread. Furthermore, it is important to note that the temporal frequency spreads of optical wavesin the anisotropic maritime turbulence and that of the terrestrial turbulence become almost identical asthe value of the anisotropic parameter goes beyond five.

Fabrication and characterization of short acetylenefilledphotonic microcells

sajed hosseini zavareh, Ryan Luder, Manasadevi Priyamvadha Thirugnanasambandam, Kushan Weerasinghe, Brian Washburn, and Kristan Corwin

Doc ID: 356675 Received 11 Jan 2019; Accepted 10 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: We have developed short (6-10 cm), connectorized acetylene-filled photonic microcells (PMCs) from photonicbandgap fibers that may replace near infrared frequency references for certain applications based on gas-filledglass cells. By using a tapering technique to seal the microcells, we were able to achieve high transmissionefficiency of 80% and moderate line center accuracy of 10 MHz (1σ). This approaches the NIST SRM 2517a 10 MHz(2σ) accuracy. Using an earlier Q-tipping technique, 37% off-resonant transmission and 5 MHz accuracy wereachieved in finding the line center, but a large 13% etalon-like effect appears on the wings of the optical depth. Theetalon-like effect is reduced to less than 1% by using the tapering method. In both cases, the microcells could beconnectorized, albeit with reduction in off-resonant transmission efficiency, for integration into multimode fibersor free-space optical systems. Although contamination is introduced during both fabrication techniques, the P13PMC line center shifts are small with respect to sub-Doppler line center. This shows that the PMC can be used formoderate accuracy frequency measurements. Finally, repeatable measurements show that PMCs are stable interms of total pressure over approximately one year.

Comparison of the spectral excitation behavior ofmethane according to InP, GaSb, IC and QC Lasers asexcitation source by sensor applications

Tobias Milde, Morten Hoppe, Herve Tatenguem Fankem, Christian Assmann, Wolfgang Schade, and Joachim Sacher

Doc ID: 349594 Received 01 Nov 2018; Accepted 10 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: The MIR wavelength regime promises better gas detection possibilities than the NIR or the visible region becauseof the higher absorbencies simulated by HITRAN. In the MIR region are many important absorption lines ofsignificant gases, which are relevant in healthcare, production supervision, safety and environmental monitoring.One of those gases is Methane. CH4 shows significant variations in absorbance with a maxima at 3.3 μm, whichresults into low detection limits in the range of low ppm. Interband cascade (IC) and quantum cascade (QC) basedlasers emit at higher wavelengths, where the absorbencies of methane are higher. The comparison is done byanalyzing the performance of two spectroscopy applications: Tunable Diode Laser Absorption Spectroscopy(TDLAS) and Quartz Enhanced PhotoAcoustic Spectroscopy (QEPAS).

Tunable broadband circular polarizer based on ultrahigh ordersurface plasmonic resonance

xuewen yan, Mingdi Zhang, Kaili Ren, jihong liu, wenwen zhang, and jun dong

Doc ID: 354977 Received 10 Dec 2018; Accepted 10 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: Circular polarizers have potential applications in optical communication andliquid crystal display. In this paper, a multi-layer twisted nanoring-rod nanostructureis designed. The finite element method is used to explore the surface plasmon of thestructure under the excitation of left-handed circularly polarized light andright-handed circularly polarized light. The results show that the structure can be usedas a polarizer in the tunable operating bandwidth of 400 nm-1290 nm and thetunability is achieved by changing the filling medium near the structure instead of thegeometric parameters of the nanostructures. We qualitatively reveal the physicalmechanism of this phenomenon from the perspective of plasmon resonance couplingby plotting the charge distribution at several specific wavelengths.

High-power edge-emitting laser based on parity-timestructuredBragg reflection waveguide

ruihong peng, Yu Li, and Wei Ping Huang

Doc ID: 355718 Received 18 Dec 2018; Accepted 09 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: A parity-time structured Bragg reflection waveguide (PT-BRW) is proposed and analyzed for realizing high powerlaser. Single transverse mode with optical field confined mainly in the low-index core is discussed to improve thecatastrophic optical damage (COD) threshold for high output power. The designed scheme can potentially mitigatethe heat built-up by moving injection from the central narrow core to the outer large-area claddings, whilesuppressing the coupler-mode transversely. The structure can achieve high output power with short cavity length,low lasing threshold and high PCE.

Parameters Influence of Laser Cleaning Soil Rust Layeron the Surface of Ceramic Artifacts

Jiawei Xu, Chenwei Wu, Xiang Zhang, Gao Fan, Tiancheng Yu, and Xiao Yuan

Doc ID: 358042 Received 17 Jan 2019; Accepted 09 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: The laser cleaning effect can be affected by many parameters, including laser power, scanning speed, laserrepetition rate and pulse duration, and the cleaning effect with these parameters is investigated. It is found that thecleaning effect is negligible for infrared high repetition nanosecond pulsed laser with repetition rate from 100 kHzto 400 kHz and pulse duration from 58 ns to 240 ns, and is significantly related to the laser power and scanningspeed. Moreover, the cleaning thresholds related to laser power and scanning speed for soil rust layer on theceramic artifacts are measured under the step distance of 281.3 μm. The heat conduction equation and thermalstress equation are used to simulate the cleaning effect with the influence of these parameters, which is in goodagreement with the experimental data.

Fast design method of smooth freeform lenswith an arbitrary aperture for collimated beamshaping

mao xianglong, jinpeng li, fengbiao wang, rong gao, xing li, and yongjun xie

Doc ID: 358967 Received 28 Jan 2019; Accepted 09 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: A method is presented for the fast design of a smooth freeform lens to tailor acollimated light beam with an arbitrary contour. This method begins by calculating an initialsurface based on a simplified ray mapping. Then the surface is fitted by a system of Zernikepolynomials, whose weights are treated as the optimization variables for further optimization.In the optimization, the objective function is analytically calculated using a partial differentialequation based approach. To validate the effectiveness of the proposed method, a freeformlens is designed for a collimated Gaussian beam with a spline contour to form a uniformillumination distribution with another spline contour, which takes only 26s. A freeform lens isalso fabricated and experimented, and its practical performance approaches the design.

Optical Bistability and Multistability Induced by Quantum Coherence inDiamond Germanium-Vacancy Color Centers

Hongjun Zhang, Gaiying Wang, Dong Sun, Xiaowei Li, and Sun Hui

Doc ID: 359064 Received 29 Jan 2019; Accepted 08 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: Optical bistability (OB) and optical multistability (OM) behaviors are investigatedtheoretically in a four-level N-type diamond Germanium-Vacancy (GeV) color center schemeimmersed in a unidirectional ring cavity based on electromagnetically induced transparency (EIT).It is found that OB behavior is very sensitive to the system parameters, such as the detunings ofprobe and coupling fields, and the intensities of coupling fields as well as the density of GeVcenters, and the thresholds of OB can be controlled via changing these parameters. In addition, wecan switch OB to OM by adjusting the intensity of control field and the density of GeV centers orvice versa. Our results may provide some guidance for an all-optical switching, opticalcommunications and optical logic devices in a solid-state system.

Photoluminescence Studies on Nanocomposite GrapheneDecorated with Tantalum Oxide

Sheeba Britto, Velavan Ramasamy, and Priya Murugasen

Doc ID: 356652 Received 09 Jan 2019; Accepted 08 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: The graphene – tantalum oxide (Ta2O5) hybrid material is synthesized using a simple hydrothermal method toelucidate its optical properties. The prepared sample is characterized by X-ray diffraction (XRD), Scanning ElectronMicroscope (SEM), High Resolution –Transmission Electron Microscope (HR-TEM), Thermo Gravimetric and DifferentialThermal Analysis (TG-DTA), Fourier Transform – Raman Spectra (FT-Raman) and Photoluminescence (PL) studies. SEM andHR-TEM analysis revealed that the Ta2O5particles are embedded on the surface of thin sheets of well defined graphenestructure. The TGA has provided substantial evidence for the thermal stability of the material with minimal percentage ofweight loss at 700 °C. Further, the excitation of the nanocomposite at wavelength 280 nm leading to emission spectra at 567 nmusing PL studies, which clearly indicates the emission of light, occurs in the visible green region.

Experimental Investigation of Aero-Optics Induced bySupersonic Film Based on Near-Field Background-Oriented Schlieren

Haolin Ding, Shihe Yi, and Xinhai Zhao

Doc ID: 356053 Received 21 Dec 2018; Accepted 08 Mar 2019; Posted 08 Mar 2019  View: PDF

Abstract: Supersonic film is a common active cooling device for imaging window of high-speed infrared imaging guidedmissile. It is important to study its aero-optics to reduce the aero-optics of missile window and improve guidanceaccuracy. Wavefront measurement accuracy based on background-oriented schlieren (BOS) was improved byconsidering the thickness change of refractive index field, introducing near-field correction and constructingdouble telecentric configuration. A standard plano-convex lens was utilized to quantitatively evaluate theimproved results, and the effectiveness of the improvement was verified. Determination methods of spatialresolution, sensitivity and dynamic measurement range of wavefront measurement under double telecentricconfiguration were studied. The influences of cross-correlation interrogation window size and step length on thewavefront reconstruction accuracy of the system were investigated. The step length should be less than the size ofthe interrogation window to make the reconstructed results had a satisfactory accuracy. Based on the wavefrontmeasurement platform of supersonic film, wavefront results of supersonic film wavefront at different positionsand cases were obtained. The quantitative relationship between aero-optical distortion and density wasconstructed. The large aperture approximation (LAA) had proven to be accurate for a wide variety of aero-opticalaberrations.

Measurement of the Ultrashort Pulse SpectralPhase based on Dispersive FourierTransformation

Minas Suqiasyan, Narek Karapetyan, Hrach Toneyan, Aghavni Kutuzyan, and Levon Mouradian

Doc ID: 356598 Received 09 Jan 2019; Accepted 08 Mar 2019; Posted 08 Mar 2019  View: PDF

Abstract: A novel technique to measure the spectral phase of an ultrashort pulse is developedbased on the dispersive Fourier transformation method, alternatively to spectralinterferometric methods. The pulse spectral phase is measured by transferring the informationfrom the spectral to the temporal domain by stretching the pulse to reach the far field ofdispersion. We have implemented the technique through sum-frequency generation by usingthe laser pulse as a reference and have experimentally demonstrated the direct spectral phasemeasurement of various amplitude-modulated pulses.

Scan angle error measurement based on phasestepping algorithms in scanning beam interferencelithography

Minkang Li, xiansong Xiang, Changhe Zhou, and Chunlong Wei

Doc ID: 358087 Received 23 Jan 2019; Accepted 08 Mar 2019; Posted 08 Mar 2019  View: PDF

Abstract: In this paper, a Doubled-Period Grating (DPG) method is proposed to measure the scan angle error in scanningbeam interference lithography (SBIL), together with high-resolution two-dimensional stage and the phase steppingalgorithms. A reference grating, which was the doubled period of the interference field, is adopted to diffract theincident left and right beams to form an interferogram captured by a CCD camera. The phase stepping algorithmwas applied to calculate the phase of the interferogram. First of all, by translating the stage, the reference gratinglines were adjusted parallel to the scan direction by comparing the phase of the interferogram between the startingpoint and the ending point. Next, by rotating the stage step by step, the phase of the interferogram was obtained ateach step as well as the phase slope. The scan angle error was considered to be the least when the slope wasminimum. Finally, a grating mask with a size of 100 x 100 mm2 was fabricated to verify the feasibility of themethod. The scan angle error was measured with a precision of less than 12.65 μrad which indicts the effectivenessof the proposed method to fabricate high quality gratings in the future.

A Path to High-Quality Imaging throughDisordered Optical Fibers: A Review

Jian Zhao, Jose Antonio-Lopez, Yangyang Sun, Behnam Abaie, Arash Mafi, Rodrigo Amezcua Correa, Shuo Pang, Axel Schulzgen, and Mostafa Peysokhan

Doc ID: 353360 Received 03 Dec 2018; Accepted 07 Mar 2019; Posted 07 Mar 2019  View: PDF

Abstract: In this paper, we review recent progress in disordered optical fiber featuringtransverse Anderson localization and its application for imaging. Anderson localizing opticalfiber has a transversely random but longitudinally uniform refractive index profile. The strongscattering from the transversely disordered refractive index profiles generates thousands ofguiding modes which are spatially isolated and mainly demonstrate single-mode properties.By making use of these beam transmission channels, robust and high-fidelity imagingtransport can be realized. The first disordered optical fiber of this type, the polymer Andersonlocalizing optical fiber, has been utilized to demonstrate better imaging performance thansome of the commercial multicore fibers within a few centimeters transmission distance. Toobtain longer transmission lengths and better imaging qualities, glass-air disordered opticalfibers are desirable due to lower loss and larger refractive index contrast. Recently developedhigh air-filling fraction glass-air disordered fiber can provide bending-independent and highqualityimage transport through a meter-long transmission distance. By integrating deeplearning algorithm with glass-air disordered fiber, a fully-flexible, artifact-free and lenslessfiber imaging system is demonstrated, with potential benefits for biomedical and clinicalapplications. Future research will focus on optimizing structural parameters of disorderedoptical fiber as well as develop more efficient deep learning algorithm to further improve theimaging performance.

Long-range in situ picometer measurement of the period of an interference field

xiansong Xiang, Jia Wei, Changcheng Xiang, Minkang Li, fantao Bu, shiyao zhu, Changhe Zhou, and Chunlong Wei

Doc ID: 354965 Received 10 Dec 2018; Accepted 07 Mar 2019; Posted 08 Mar 2019  View: PDF

Abstract: A high-precision in situ method of measuring and controlling the period of long-range interference field is proposed. With this method, before the exposure process of the holographic grating fabrication, the period and the period uniformity of the holographic grating can be evaluated directly from the interference field, then optical adjustment can be applied until the grating period is tuned to any certain desired value. Experiments of measurement and adjustment are conducted and an interference field with period value of 833.335nm±10pm in 60mm range is reached. The proposed method gives an efficient way to fabricate large gratings of an accurate period, furthermore it provides a reliable tool that may lead us to picometer level optical metrology and fabrication for the most advanced lithographic equipment and other scientific fields.

High-sensitivity quasiperiodic photonic crystal biosensor based on multiple defective modes

xiaoqing wang, Xing Liu, Tingting Zhao, shuai feng, xiao Chen, Honglian Guo, Chuanbo li, and Yiquan Wang

Doc ID: 353255 Received 30 Nov 2018; Accepted 07 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: The sensitivities of the octagonal quasiperiodic photonic crystal (QPC) defective modes to the variation of environmental refractive index are systematically studied. The octagonal QPC biosensors are composed of silicon columns arranged in liquid background. By designing defect structure, a variety of defect modes with different spatial symmetries and field profiles are obtained, and their refractive index sensitivities can be quite different from each other, where a maximum value of 800nm/RIU is achieved. The liquid can flow freely among the rods through the entire structure, so it is convenient to monitor the concentration of protein in the liquid environment dynamically. Through antibody-antigen binding or DNA aptamer-protein binding, the biological protein can be specifically attached around the defect body. The influence of the protein layer’s thickness to the shift of the resonant wavelength is studied, where a minimum protein’s thickness of less than 10 nm can be detected, and the spatial field profiles of different defect modes are analyzed to explain the corresponding sensitivity values. Compared to the conventional periodic photonic crystals, QPC structures have higher spatial symmetry and less dependence on the propagating direction of incident light beam, and it provides an important direction for the practical application of photonic crystal biosensor devices in the future.

Gas phase Raman spectroscopy of non-reactingflows : comparison between free space andcavity based spontaneous Raman emission

Lee Weller, Maxim Kuvshinov, and Simone Hochgreb

Doc ID: 352184 Received 19 Nov 2018; Accepted 06 Mar 2019; Posted 06 Mar 2019  View: PDF

Abstract: We report on a comparison of free space and Cavity-Enhanced Raman Spectroscopy(CERS) for gas phase measurements of nitrogen and oxygen in ambient air. Real time analysiscapabilities, and continuous Raman signals with low power diodes, make the technique noninvasive,affordable, compact and applicable for usage in non-reacting flows. We derive acomprehensive model for estimation of photon emission for both free space and cavity basedsignals and discuss trade-offs in how to organize the cavity geometry for maximum gain relativeto free space. Measurements in both free and cavity configurations are compared to the expectedsignals, demonstrating the usefulness of the model in predicting amplification. The presentresults can serve as a quick guide on how to use low power continuous wave lasers in a cavitysetup to obtain enhanced laser induced spontaneous Raman scattering.

Terahertz image super-resolution based on deepconvolutional neural network

Zhenyu Long, Tianyi Wang, chengwu you, Zhenggang Yang, Kejia Wang, and Jinsong Liu

Doc ID: 356928 Received 09 Jan 2019; Accepted 06 Mar 2019; Posted 07 Mar 2019  View: PDF

Abstract: We propose an effective and robust method for terahertz (THz) image super-resolution based ondeep convolutional neural network (CNN). A deep CNN model is designed. It learns an end-to-end mappingbetween the low and high-resolution images. Blur kernels with multiple width and noise with multiple levelsare taken into the training set, so that the network can handle THz images very well. Quantitative comparisonof the proposed method and other super-resolution methods on the synthetic THz images indicates that theproposed method performs better than other methods in accuracy and visual improvements. Experimentalresults on real THz images show that the proposed method significantly improves the quality of THz imageswith increased resolution and decreased noise, which prove the practicability and exactitude of the proposedmethod.

Effects of substrate temperature on material andphotovoltaic properties of magnetron-sputteredSb2Se3 thin films

Shiming Chen, Xiaobo Hu, Jiahua Tao, Juanjuan Xue, Guo-En Weng, Jinchun Jiang, Xiuxiu Shen, and Shaoqiang Chen

Doc ID: 356508 Received 02 Jan 2019; Accepted 05 Mar 2019; Posted 06 Mar 2019  View: PDF

Abstract: We studied the material and photovoltaic properties of Sb2Se3 thin films fabricated by a magnetron-sputteringmethod at different substrate temperatures. The films had good crystallinity at substrate temperatures of over300°C. The band-gap energies between 1.1 and 1.5 eV of the films, which were obtained by transmittancemeasurements, initially decreased and then increased slowly with increasing temperature. Solar cells based on thefilms with a structure of ITO/CdS/Sb2Se3/Au were fabricated and the substrate temperature had significant effectson the device performance. Low crystal quality at low temperature resulted in low short-circuit current (Jsc), whilehigh temperature caused Se deficiency due to evaporation, which decreased the open-circuit voltage (Voc). The bestsolar cell performance achieved an efficiency of 0.84% with a Voc of 0.27 V and Jsc of 9.47 mA/cm2 when thesubstrate temperature was 325°C.

Optimization and analysis of infrared multilayerdiffractive optical elements with finite feature sizes

Yang Chao, yang hongfang, Chuang Li, and Changxi Xue

Doc ID: 354602 Received 04 Dec 2018; Accepted 05 Mar 2019; Posted 05 Mar 2019  View: PDF

Abstract: The infrared multilayer diffractive optical elements (MLDOEs) usually own microstructureheights of a few hundred micrometers. The design and fabrication of those elements is more difficultthan MLDOEs working in the visible waveband, especially for MLDOEs with high numerical apertureand finite feature sizes. Based on scalar diffraction theory and manufacturing errors, the effective areamethod for improving diffraction efficiency of infrared MLDOEs is developed. Closed-form analyticalrelations between diffraction efficiency, microstructure heights, microstructure periods and incidentangles are derived and verified in the infrared waveband. Then optimized microstructure heights ofinfrared MLDOEs with different microstructure zone widths in the infrared wavelength 3-5μm and8-12μm at normal incidence can be obtained. The results indicate that the microstructure heights ofinfrared MLDOEs determined by the method have higher diffraction efficiency than former designmethod. And the method is verified by the rigorous electromagnetic method. Finally, the influence ofincident angles on infrared MLDOEs is investigated. Our results show that the suggestedmicrostructure parameters of MLDOEs both produce higher diffraction efficiencies than that ofstructure designed by scalar diffraction theory and may lead to more efficient hybriddiffractive-diffractive optical systems based on MLDOEs.

3D Tomography Reconstruction Improved by Integrating View Registration

Ning Liu, qingchun lei, Yue Wu, and Lin Ma

Doc ID: 355308 Received 13 Dec 2018; Accepted 05 Mar 2019; Posted 05 Mar 2019  View: PDF

Abstract: Tomographic measurements involve two steps: view registration (VR) to determine the orientation of the projections and the subsequent tomography reconstruction. Therefore, the practical error in both steps impacts the overall accuracy of the final tomographic measurements. Past work treated these two steps separately. This work shows that the overall tomography accuracy can be enhanced substantially if these two steps are considered holistically. Because there is an opportunity for each step to leverage the information in the other step to improve the overall accuracy if they are considered holistically. Based on this recognition, this work developed a new method (code named the RIVR method) to implement such a holistic scheme. The key of this implementation involved the use of the Metropolis criterion to adjust the initial orientation provided by traditional VR process dynamically. Both controlled experiments and accompanying numerical analyses were conducted to validate the RIVR method. Two sets of controlled experiments, one representing a static uniform distribution and the other a turbulent distribution, were conducted and analyzed. And in both sets of experiments, the RIVR technique was demonstrated to significantly reduce the overall reconstruction error (by ~37%) compared to past methods that treated VR and tomography separately.

Development of a Compact Deep-sea RamanSpectroscopy System and Direct BicarbonateDetection in Sea Trials

Jinjia Guo, Wangquan Ye, Qingsheng Liu, Fujun Qi, Kai Cheng, dewang Yang, and Ronger Zheng

Doc ID: 356294 Received 02 Jan 2019; Accepted 05 Mar 2019; Posted 05 Mar 2019  View: PDF

Abstract: In recent years, Raman spectroscopy techniques have been successfully applied tothe area of deep sea exploration. However, there are still some problems impeding the furtherapplication of Raman systems. For example, the big sizes of underwater Raman systemsmake it difficult to deploy on the delivery platforms. Meanwhile, the sensitivity is often adisadvantage requiring improvement of detection more trace components. To solve theseproblems mentioned above, a new compact deep-sea in-situ Raman spectroscopy system ispresented in this paper. The whole system weights 60 kg and is housed in an800mm×Φ258mm pressure vessel with an optical window on the front end cap. The maincomponents include a 532nm Nd:YAG laser, an optics module, a high throughoutspectrograph with 0~4900cm-1 spectral range and 8 cm-1 spectral resolution, a TEC cooled2000×256 pixels CCD detector, a PC104 embedded computer, and electronics module. Toevaluate the performance of the newly developed Raman system, systematic experimentshave been carried out with solutions in laboratory, and the results have shown that the systemlimit of detection (LOD) of SO42- is 0.4 mmol/L. The Raman system has been successfullydeployed on a remote operated vehicle (ROV) on “Kexue” research vessel in June 2015.Thetypical in-situ detection results are presented in this paper, and it is shown that the Ramansystem is capable of detecting the Raman signal of SO42- and fluorescence of chl-a andCDOM in seawater. With500 spectra accumulation and some data processing, the Ramansignal of HCO3- is obtained. This is the first report of direct measurement of HCO3- by Ramansystem in in-situ experiments. After further optimization, it is hoped to apply the Ramansystem in seafloor observation network for long-time carbon cycling research.

High-beam-quality operation of a 2 μmpassively Q-switched solid-state laser basedon boron nitride saturable absorber

yingjie shen, Linjun Li, Xiaoming Duan, ruijun lan, Long Zhou, Wenqiang Xie, and xining yang

Doc ID: 357572 Received 14 Jan 2019; Accepted 04 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: Boron nitride (BN) nanosheets were used as the material sources which werecoated on a calcium fluoride (CaF2) mirror to achieve saturable absorber (SA). A passively Qswitched(PQS) solid-state laser at 2000.5 nm was demonstrated with a Tm,Ho:YAlO3(Tm,Ho:YAP) crystal and a SA based on BN. An average output power of 650 mW wasobtained with a minimum pulse width of 6.3 μs at the pulsed repetition frequency (PRF) of41.7 kHz, corresponding to a per pulse energy of 13 μJ. The beam quality factor wasmeasured to be 􀜯􀯫􀬶 = 1.06 and 􀜯􀯬􀬶 = 1.07 at the maximum output power.

Edge detection for optical synthetic aperture based onconditional generative adversarial networks

Mei Hui, Yong Wu, Wenjie Tan, Ming Liu, Liquan Dong, Lingqin Kong, and Yuejin Zhao

Doc ID: 357690 Received 14 Jan 2019; Accepted 04 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: Detecting the interference fringes of the optical synthetic aperture is core of preventing the misalignments ofthe sub-mirrors in piston, tip and tilt. These fringes are characterized as follows: (1) the edge information ofsub-mirrors is accompanied by complex shapes and large gaps; (2) the traditional edge detection algorithmshave different optimal thresholds under different interference fringes and they may lose boundaryinformation. To address these problems, a novel method for detecting the edge of the synthetic aperturefringe images is proposed. Because Conditional Generation Adversarial Networks avoids the difficulty ofdesigning the loss function for specific task, it is suitable for our project. We trained over 8,000 images basedon real images and simulated images. Experiments prove that the proposed method can reduce the falsedetection rate to 0.2, compared with 0.56 by Canny algorithm. This method can also directly detect the fringeedge of the optical synthetic aperture systems which are accompanied by varied shapes and growing numberof sub-mirrors. And when the input images lose boundary information, the traditional algorithm does notrestore the boundary. But the proposed method makes decision globally, thus it guesses and then fills theboundary. The maximum error of the generated boundary and the actual boundary is two pixels.

Phase-matched nonlinear wave-mixingprocesses in XUV region with multicolor lasers

Khoa Anh Tran, Khuong Dinh, Peter Hannaford, and Lap Dao

Doc ID: 358446 Received 23 Jan 2019; Accepted 04 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: We report here experimental results of perturbative nonlinear optical wave-mixingprocesses in the extreme ultraviolet region by using two-color and three-color laser fields. Besidesthe usual odd-harmonic spectrum of high harmonic generation, new spectral components areobserved when multiple incommensurate lasers (one driving plus one or two control field)interact with neutral krypton gas. To demonstrate the wave-mixing process underlying suchan observation, we firstly couple the driving field with either the signal or the idler field of anoptical parametric amplifier in the gaseous ensemble to generate certain mixing frequencies. Thetwo control fields are then simultaneously combined with the driving field to produce broad anddistinguishable mixing peaks that clearly reveal the contribution of each control laser. Finally,the variation of the intensity of the mixing waves with the intensity of each control field, the gasdensity, and the relative focus position is examined for signatures of phase-matched generation ofthe mixing fields in this spectral region.

Tunable plasmonics effects arising from the metal-dielectric nanorods

Yuan-Fong Chau, Chung-Ting Chou Chao, Hung Ji Huang, Ren Chong Lim, and Hai-Pang Chiang

Doc ID: 356441 Received 02 Jan 2019; Accepted 04 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: We have investigated the plasmonic effects in a two-dimensional periodic array ofmetallodielectric nanorods with and without rotational angle which the integration of thelocalized surface plasmon resonance (SPR) and hollow plasmon resonance (HPR) properties isperformed. Four patterns of nanostructures are investigated. We make use of the threedimensionalfinite element method to obtain the simulation results which demonstrate that thelocalized SPR and HPR in metallodielectric nanorods enhance the near field intensity andincrease the depth of transmittance dip, providing an additional degree of freedom in the controlof light wave at the nanoscale. Numerical results show that the depth of transmittance dip andsensitivity of the case 1 and case 2 can be elevated to a value of 83.21% and 6.7 times, respectively, whenthe rotational angle of metal/dielectric nanorods varies from 00 to 900. The sensitivity of the case 3and case 4 can be raised to the magnitude of 700~1091 nm/RIU (where RIU is the refractiveindex unit), and the characteristics enable the extensive applications for nanophotonic deviceswith high performance in a predictable manner.

Fast measurement of laser beam quality factor basedon phase retrieval with liquid lens

Kunhao Ji, Junbo Li, Lingqiang Meng, Zhigang Han, and Rihong Zhu

Doc ID: 357337 Received 10 Jan 2019; Accepted 04 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: In this paper, a new method for measuring the beam quality (M2) of lasers based on phase retrieval with liquid lensis proposed. With intensity profiles obtained under different focal lengths in a certain position, a Variable-FocusIterative Retrieval Algorithm (VFIRA) is established for the reconstruction of the complex amplitude. Then, the M2can be calculated with the angular spectrum theory. The feasibility of the proposed method is demonstrated bysingle- and multi-mode lasers both in simulations and experiments. Compared with the traditional liquid lensmethod, the M2 of the lasers can be measured faster with the proposed method.

Linearized Fiber Optic Link with High SFDR Over WideFrequency Range

Ruiqi Zheng, Erwin Chan, Xudong Wang, Xinhuan Feng, and Bai-Ou Guan

Doc ID: 357018 Received 08 Jan 2019; Accepted 03 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: An all-optical linearized fiber optic link is presented. It solves the problem in most reported structures where ahigh spurious free dynamic range (SFDR) can only be obtained in a limited frequency range. The link only involvesa laser, an optical modulator and a photodetector. The novel design in the modulator bias setting enables the thirdorder intermodulation distortion to be suppressed by controlling only one bias voltage of a dual-parallel MachZehnder modulator (DPMZM) while the other two bias voltages are set to bias the sub MZM and the main MZM ofthe DPMZM at the standard peak and null point respectively. The link has a very simple structure and does notrequire any electrical component, and hence a high SFDR can be obtained over a wide frequency range. Techniquesare proposed using off-the-shelf components for stabilizing the modulator bias setting to maintain high SFDRperformance when the link is operated in practice. Measured results demonstrate a high SFDR of 120.5 dB∙Hz4/5 ±1.6 dB over 2 - 20 GHz frequency range in an unamplified linearized fiber optic link. To our knowledge, this is thefirst report of a linearized fiber optic link with around 120 dB∙Hz4/5 over such a wide frequency range.

Influence of lateral misalignment on opticalrotational Doppler effect

song qiu, Tong Liu, zhimeng li, Chen Wang, yuan ren, qiongling shao, and chaoyang xing

Doc ID: 353047 Received 14 Dec 2018; Accepted 02 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: The discovery of optical rotational Doppler effect associated with orbital angularmomentum of light paves a new way to detect the rotational speed of spinning objects. In thispaper, we investigate the influence of lateral misalignment, i.e. the distance between the beamaxis of probe light and the rotation axis of spinning object, on the rotational Doppler effect.First, we analyze the mechanism of rotational Doppler effect of optical vortices based onlinear Doppler effect. Specifically, we considered the general case where the center of theoptical vortex does not coincide with the rotation axis, and deduced the generalized formulaof rotational Doppler shift based on a local scattering model. It is found that the bandwidth ofthe rotational Doppler signal depends proportionally on the amount of lateral misalignmentwhereas the value of rotational Doppler shift remains constant. A proof-of-conceptexperiment is performed and the measured results agree well with theoretical predications.These findings may be useful for the practical application of optical rotational Doppler effectin remote sensing and metrology.

Various soliton molecules in fiber systems

Lei Li, Haitao Huang, Lei Su, Deyuan SHEN, Dingyuan Tang, Mariusz Klimczak, and Luming Zhao

Doc ID: 355560 Received 02 Jan 2019; Accepted 01 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: Generation and propagation of various soliton molecules (SMs) in fiber system arereviewed. SMs can survive either in fibers or fiber lasers. Dispersion-managed (DM) fiberlink is the only platform for SMs demonstration while various fiber lasers can supportdifferent SMs. The fundamental unit of SMs can be conventional solitons generated inanomalous dispersion regime, stretched pulses in DM fiber lasers, parabolic pulses or gainguidedsolitons in normal dispersion regime. SMs with typically close soliton separation arepresented. In addition, we demonstrate a new kind of SMs with nanosecond solitonseparation. The narrow spectral filtering is required for the generation of SMs with such longdistance interaction.

Dear Dr. Sun,We require confirmation of Yao Zhang removal. Please have Yao Zhang email us confirming their removal from this submission.

Sin Hyuk Yim, Sang-Bum Lee, Taeg Yong Kwon, Ku-min Shim, and Sang Eon Park

Doc ID: 356025 Received 02 Jan 2019; Accepted 01 Mar 2019; Posted 01 Mar 2019  View: PDF

Abstract: We report the optical phase-locking of two extended-cavity diode lasers with afrequency difference of 6.9 GHz by serrodyne modulation. The bandwidth of the phaselockingloop is extended up to 9.5 MHz. The residual phase noise of the two phase-lockedlasers reaches -130 dBrad2/Hz in the offset frequency range of 1.5 kHz to 9 kHz and below -120 dBrad2/Hz in the range of 150 Hz to 350 kHz, respectively. It is expected that thesensitivity limit of atom interferometers will be enhanced when the phase-locked lasers areused.

Reducing shadowing losses in silicon solarcells using cellulose nanocrystal:polymerhybrid diffusers

Qi Wei Xu, lingju meng, and Xihua Wang

Doc ID: 357451 Received 17 Jan 2019; Accepted 01 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: Gridline shadowing is one of the main factors affecting the performance of siliconsolar cells. In this demonstration, a straightforward, scalable approach is reported to reduceshadowing losses from metallic contacts on silicon solar cells by employing cellulosenanocrystals (CNC) mixed in a polymer - polydimethylsiloxane (PDMS). The method ishighly compatible with current solar cell module manufacturing. The CNC:polymer (CNP)hybrid diffusers, offering highly efficient broadband light diffusion, are applied atop themetallization areas to deflect the light impinging on metallic gridlines toward uncoveredactive areas on the solar cell. Simulations showed that the CNP diffuser is an excellentcandidate for reducing shadowing losses within a wide range of incident angles, as it canreduce more than 30% of shadowing losses at normal incidence and nearly 50% of the lostlight can be recycled at the incident angle of 60°. Taking advantage of reduced shadowinglosses, a new 6-busbar technology based on the CNP diffusers is proposed with lowermanufacturing complexity and higher overall efficiency.

Study on the fabrication of high precisionreflective volume Bragg gratings

Peng Chen, jin yunxia, Dongbing He, Junming Chen, Jiao Xu, huifang dai, Jingyin Zhao, Fanyu Kong, and Hongbo He

Doc ID: 359085 Received 30 Jan 2019; Accepted 01 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: Reflecting Bragg gratings (RBGs) recorded in photo-thermo-refractive (PTR)glasses have been widely used in narrowing and stabilization of the laser emission spectrum. As the center wavelength of RBGs determines the final output wavelength of lasers, it is necessary to carefully control the center wavelength of RBGs during the fabrication process. In this paper, the fabrication process of high precision RBGs was investigated. We developed a two-step method and demonstrated both theoretically and experimentally that it is effective and can be used to guide the fabrication process of high precision RBGs. The experimental results show that the center deviates from the target centerwavelength within ±10 pm.

An optically pumped gas THz fiber laser basedon gold-coating quartz hollow-core fiber

Shuai Sun, Guo Zhang, Wei Shi, Zhaoshuo Tian, Quan Sheng, Yao Zhang, Haiwei Zhang, and Jian-Quan Yao

Doc ID: 353223 Received 30 Nov 2018; Accepted 01 Mar 2019; Posted 06 Mar 2019  View: PDF

Abstract: An optically pumped gas Terahertz fiber laser based on gold-coating quartzhollow-core fiber is demonstrated. When the Terahertz fiber laser is filled with methanol gasand pumped by a piezoelectric ceramic transducer adjusted transversely excited atmosphericpressure carbon dioxide laser, a continuous 2.52THz laser with the output power of 110mW isobtained. Attributing to the adjustment of piezoelectric ceramic transducer in carbon dioxidelaser, the fluctuation of Terahertz fiber laser output power is controlled within ±5%. Theresult confirms the possibility of compact flexible optically pumped gas Terahertz fiber laser.

Free Space Transmission System in a TunableSimulated Atmospheric Turbulence Channelusing a High Repetition-rate Broadband FiberLaser

Junda Chen, Tianshu Wang, Xinmeng Zhang, zhiwen sun, Ziqi Jiang, Haifeng Yao, Peidi Chen, Yiwu Zhao, and Huilin Jiang

Doc ID: 357403 Received 10 Jan 2019; Accepted 28 Feb 2019; Posted 05 Mar 2019  View: PDF

Abstract: We demonstrated a free space transmission based on a broadband fiber laser at16Gbit/s over a simulated atmospheric turbulence channel. The broadband laser pulse is partof a supercontinuum generated by a homemade picosecond laser based on the Raman gainsoliton compression pumping a segment of highly nonlinear fiber. The scintillation indexes,eye patterns and bit error rates of transmission based on the broadband laser and a narrowlinewidth laser were compared. The results show a 29.5% reduction in the scintillation indexand a sensitivity of -28.6dBm at the forward error correction limit, which has a 2.9dBimprovement compared with the narrow-linewidth system. It is feasible to use broadbandlaser as carriers combining optical time division multiplexing as a multiplexing method toimprove the communication performance under weak atmospheric turbulent conditions.

Study on continuous wave laser damagemechanism of spectral combining grating

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

Doc ID: 357489 Received 11 Jan 2019; Accepted 28 Feb 2019; Posted 01 Mar 2019  View: PDF

Abstract: With increased power of the spectral beam combination, surface heat distortion ofthe multilayer dielectric gratings (MDGs) could occur. In this study, the damage morphologyof MDGs was initially analyzed under a continuous wave (CW) laser irradiation.Subsequently, the surface distortion and temperature rise of different MDGs were testedexperimentally. The experimental results showed that the initial damage of MDGs was causedby the thermal stress. Further, the thermal stress of the multilayer dielectric films on the MDGsurface was analyzed theoretically. The calculated results were in good agreement with theexperimental results. The conclusions indicated that with the increase of the MDG surfacetemperature, the stress in the HfO2 layers reached initially the stress damage threshold of thedielectric films and, therefore, the damage occurred.

Vector optical fiber magnetometer based on capillary filled with magnetic fluid

jingang cui, dawei qi, He Tian, and Hanyang Li

Doc ID: 354967 Received 02 Jan 2019; Accepted 28 Feb 2019; Posted 28 Feb 2019  View: PDF

Abstract: A novel and practical magnetic field sensor based on optical fiber optics was proposed in ours work. We first demonstrated the magnetic sensing with the structure that single-mode optical fibers are fused with capillaries in parallel in experiment. In the first place, we clearly shown the aggregation and arrangement variation with magnetic field of magnetic nanoparticles in capillaries. Based on the tunable of ERI of optical modes in waveguide structure of sensor, the he optical properties and sensing mechanism in the sensing structure were simulated and further analyzed. We achieved the detection of space magnetic field including intensity and its direction. We obtained sensitivity of sensor is 112 pm/mT, which present well performance in the same kind of optical fiber magnetic field sensor.

Dispersive Wave and Four-Wave Mixing Generation inNon-instantaneous Nonlinear Fiber Solitons

sebastian vergara palacio and Rodrigo Acuna Herrera

Doc ID: 355802 Received 19 Dec 2018; Accepted 28 Feb 2019; Posted 28 Feb 2019  View: PDF

Abstract: This paper presents a detailed analysis regarding thegeneration of a dispersive wave (DW) and four-wavemixing (FWM) in the non-instantaneous, nonlinear responseof solvents using a commercial photonic crystalfiber (PCF) filled with carbon disulfide (CS2) where thebeam is pumped in the anomalous dispersion domain.The main finding is the fact that the output spectrumchange from coherentDWto incoherent modulation instabilitiesjust by changing from constant to variablenonlinear parameters. This study can be extended toothers solvents including ethanol, methanol, and butanol.

High speed amplitude modulator with high modulation indexbased on plasmonic resonant tunable metasurface

Luigi Bibbo', Qiang Liu, Karim Khan, ashish yadav, Sayed Elshahat, Zi-Lan Deng, and Zhengbiao Ouyang

Doc ID: 349175 Received 25 Oct 2018; Accepted 28 Feb 2019; Posted 01 Mar 2019  View: PDF

Abstract: High-speed optical amplitude modulation is important for optical communication systems andsensors. Moreover, nano optical modulators are important for developing optical-communicationaided high-speed parallel-operation processors and micro biomedical sensors for inside-bloodcapillaryexaminations or microsurgery operations. In this paper, it´s designed a plasmonicresonant tunable metasurface with Barium Titanate (BTO) as a nanoscale optical modulator withhigh modulation index and high speed. The BTO operated well in the VIS and near IR range,enables tunable optical devices with zero dispersion and high speed. The results obtained byrigorous finite-element method simulations have shown that the hypothesized device has a goodpotential for fast modulation in related applications, e.g., modulators in nano optical systems,nano optical switches and nano sensors.

Retaining 3D shape of picosecond laser pulsesduring optical harmonics generation

Igor Kuzmin, Sergey Mironov, Ekaterina Gacheva, Anatoly Poteomkin, and Efim Khazanov

Doc ID: 352131 Received 15 Nov 2018; Accepted 27 Feb 2019; Posted 28 Feb 2019  View: PDF

Abstract: Collinear and noncollinear sum frequency generation of broad-band laser pulses with angular and frequency chirpis considered. The conditions of minimal distortions of 3D ellipsoidal intensity distribution of triangular chirpedfemtosecond pulses during generation of the second, third and fourth harmonic of a Ti-Sa laser in LBO, BBO andKBBF crystals were found using numerical methods. The efficiency of conversion from the fundamental to thefourth harmonic (45%) is higher than to the third harmonic (20%), and the distortions of intensity distribution areless.

Tilted Light Coupling Structure for theThickness Reduction of Liquid Crystal DisplayBacklight

Sheng Xu, Tao Yang, Huanghui Miu, Yuzhen Xu, Qiongxin Shen, Tailiang Guo, Zhengxing Cui, Enguo Chen, and Yun Ye

Doc ID: 347109 Received 01 Oct 2018; Accepted 27 Feb 2019; Posted 27 Feb 2019  View: PDF

Abstract: Traditional edge-lit light guide plate (LGP) is hard to achieve ultrathin structure,because the LGP thickness will be limited by the luminescence regional width of the LEDsource. In this paper, a novel tilted light coupling structure (TLCS) for liquid crystal display(LCD) backlight is proposed, which allows inclined layout of edge LED array to significantlyreduce the LGP thickness. The design process and optical conditions of the TLCS are firstdiscussed, and the effect of structural parameters on the coupling efficiency is also analyzed.After that, a fundamental model and an improved model are designed respectively, namelythe planar TLCS and the curved TLCS. Design results show that the light coupling efficiencyof the proposed TLCS can reach 95% while the LGP thickness is reduced to 7% thinner thanluminescence regional width of the LED source. The proposed TLCS will have broadapplications in light guiding devices.

Modeling the remote-sensing reflectance ofhighly turbid waters

Joel Wong, Soo Chin Liew, Elizabeth Wong, and Zhongping Lee

Doc ID: 352476 Received 20 Nov 2018; Accepted 27 Feb 2019; Posted 27 Feb 2019  View: PDF

Abstract: Abstract: In ocean colour remote sensing, subsurface remote-sensing reflectance (rrs) of optically deep waters can be linked to its absorption (a) and backscattering coefficients (bb) by various models. The use of such models allow for quick calculations rrs from such coefficients, eliminating the need to solve the radiative transfer equation. In particular, rrs can be expressed as a function of bb/(a + bb). HydroLight and Monte Carlo simulations showed that the commonly used models underestimate rrs in waters with high suspended sediment load. Monte Carlo simulations confirmed that this is due to a sharp increase in multiple scattering events at high turbidity levels. A quartic polynomial model is derived relating rrs and IOPs for waters of any turbidity, in order toavoid significant errors in waters of high turbidity.

Temperature Perturbation Related to the Invisible InkVibrationally Excited Nitric Oxide Monitoring (VENOM)Technique: A Simulation Study

Joshua Winner, Feng Pan, Madison Mcllvoy, Rodney Bowersox, and Simon North

Doc ID: 355289 Received 12 Dec 2018; Accepted 27 Feb 2019; Posted 27 Feb 2019  View: PDF

Abstract: The limits of applicability of the invisible ink variant of the vibrationally excited nitric oxidemonitoring (VENOM) technique for three distinct flow fields is reported in this work. This technique involves the generation of a grid of vibrationally excited NO (X, 2Π) by exciting the NO A-X electronic transition at 226 nm, which subsequently relaxes via fluorescence and collisional quenching to produce vibrationally excited NO (X, 2Π). This grid is then probed by two laser sheets tuned to distinct rotational states. The resulting images allow for the simultaneous measurement of temperature and velocity. The flow fields presented in this work provide a range of NO concentrations, vibrational lifetimes, pressures, temperatures, and collisional quenching, which explore the applicability of the invisible ink variant to a wide range of conditions. We have modelled the initial NO, O2, and N2 vibrational and rotational energy distribution resulting from the combination of fluorescence and quenching of electronically excited NO. The subsequent rethermalization of the sample, in particular the long-time vibrational relaxation, has been modelled using a forced harmonic oscillator model. The time dependent temperature perturbation due to the invisible ink technique is evaluated for two distinct timescales; a short timescale temperature rise resulting from collisional quenching and rotational/translational thermalization and a long timescale temperature rise caused by vibrational thermalization. Under low pressures where fluorescence dominates quenching, there is minimal temperature perturbation of the flow field on the timescale of a VENOM measurement, and the short timescale temperature perturbation only becomes significant at high NO seed concentrations. The predicted signal- to-noise of the invisible ink method is unaffected for low pressure, low temperature flow fields. However, preserving signal-to-noise for a high temperature, high pressure flow field could prove challenging due to the impact of quenching and self-absorption. Overall, we find that the invisible ink method is predicted to be a viable laser-based diagnostic for velocimetry and thermometry over a wide range of experimental conditions.

Supercontinuum-laser diffuse reflectancespectroscopy in conjunction with an extendedKubelka-Munk model—a methodology fordetermination of temperature-dependent quantumefficiency in highly scattering and fluorescent media

Michael Brupbacher, Dajie Zhang, William Buchta, Marc Airola, David Brown, Michael Thomas, and James Spicer

Doc ID: 356112 Received 27 Dec 2018; Accepted 26 Feb 2019; Posted 27 Feb 2019  View: PDF

Abstract: Temperature-dependent diffuse reflectance measurements on Cr-doped α-alumina monoliths have beenperformed using supercontinuum-laser illumination and CO2-laser heating. These measurements have beeninterpreted using an extended Kubelka-Munk (K-M) model describing diffuse-light propagation in highly scatteringand fluorescent media to assess the temperature dependence of fluorescence quantum efficiency. Analysis ofexperimental results has provided a qualitative understanding of the temperature-dependent conditions for modelapplicability and also suggests methods for using supercontinuum-laser diffuse reflectance spectroscopy fordetection of unknown fluorescent dopants.

Application of neutral-density filters to nonuniformitycorrection

Songtao Chang and Yaoyu Zhang

Doc ID: 356855 Received 04 Jan 2019; Accepted 26 Feb 2019; Posted 27 Feb 2019  View: PDF

Abstract: Two-point nonuniformity correction (NUC) is the most effective and commonly-used algorithm forscientific and commercial infrared imagers. However, conventional two-point NUC requires tworeferences at different levels of flux, which are sometimes difficult to obtain. To overcome this drawback,a neutral-density filter based solution for two-point NUC of cooled infrared focal plane arrays isproposed in this paper. Benefited from the specially designed filters and an additional concave mirror,NUC can be conducted by using a single reference at ambient temperature. Several experiments wereconducted to validate performance of the proposed NUC method. The results indicate that it yieldsexcellent performance compared with conventional NUC methods, moreover it is more economical andconvenient in various applications.

Improved methodology for performing the inverse Abeltransform of flame images for colour ratio pyrometry

Jochen Dreyer, Radomir Slavchov, Eric Rees, Jethro Akroyd, Maurin Salamanca, Sebastian Mosbach, and Markus Kraft

Doc ID: 352238 Received 27 Nov 2018; Accepted 25 Feb 2019; Posted 25 Feb 2019  View: PDF

Abstract: A new method is presented for performing the Abel inversion by fitting the line-of-sight projection ofa predefined intensity distribution (FLiPPID) to the recorded 2D projections. The aim is to develop amethodology that is less prone to experimental noise when analysing the projection of antisymmetricobjects, in this case co-flow diffusion flame images for colour ratio pyrometry. A regression model ischosen for the light emission intensity distribution of the flame cross-section as a function of the radialdistance from the flame centre-line. The forward Abel transform of this model function is fitted to theprojected light intensity recorded by a colour camera. For each of the three colour channels, the modelfunction requires three fitting parameters to match the radial intensity profile at each height above theburner. This results in a very smooth Abel inversion with no artifacts such as oscillations or negativevalues of the light source intensity, as is commonly observed for alternative Abel inversion techniques,such as the basis-set expansion (BASEX) or onion-peeling. The advantages of the new FLiPPID methodare illustrated by calculating the soot temperature and volume fraction profiles inside a co-flow diffusionflame, both being significantly smoother than those produced by the alternative inversion methods. Thedeveloped FLiPPID methodology can be applied to numerous other optical techniques for which smoothinverse Abel transforms are required.

Orthographic projection images based photon counted integral Fourier holography

Min Wan, Inbarasan Muniraj, Ra'ed Malallah, Ni Chen, John Healy, James Ryle, and John Sheridan

Doc ID: 352790 Received 26 Nov 2018; Accepted 25 Feb 2019; Posted 25 Feb 2019  View: PDF

Abstract: Unlike coherent imaging techniques, light field imaging uses incoherent (white light) illumination to generate a digital hologram of three-dimensional (3D) objects in real-time. Multiple projections (or elemental images) of a 3D object are captured using a micro lens array attached to a digital camera. Orthographic projection images (OPIs) can be synthesized from the recorded elemental images. The synthesized intensity-based OPIs are then multiplied by the corresponding phase functions and combined to form a digital hologram (also known as integral hologram) of a 3D object under illumination. In this study, we analyze the performance of a synthesized integral hologram under low light imaging (photon-counting) conditions. The feasibility of this technique is verified experimentally by capturing the elemental images and subsequently generating orthographic projection images and by varying photon counts to reconstruct the digital holograms.

On the possibility of simultaneous temperature,species, and electric field measurements by coupledhybrid fs/ps coherent anti-Stokes Raman scatteringand electric field induced second harmonic generation

Jonathan Retter and Gregory Elliot

Doc ID: 347898 Received 16 Oct 2018; Accepted 25 Feb 2019; Posted 25 Feb 2019  View: PDF

Abstract: Optical signals of gas temperature, species concentration, and electric field are monitored in simple mixturesat room temperature and in the fuel rich region of a hydrogen diffusion flame. A two-beam purerotational CARS approach was utilized for the temperature and species detection, where the combinedpump/Stokes pulse doubled as the EFISHG pump for the electric field detection. Time-averaged EFISHGsignals in environments with argon, nitrogen, oxygen, hydrogen, and air were found to match the relativehyperpolarizabilities of the molecules tabulated in literature. Measurements in a dynamic H2-airenvironment represented the ability to monitor the signal dependence of species on a single-shot basis.Time-averaged EFISHG signals in different thermal environments showed the expected µ 1T2 EFISHG signaldependence when also correcting for relative H2/N2 concentrations. Finally, measurements in a flameshowed the ability to monitor the EFISHG signal dependence on the gas temperature on a single-shotbasis in a plasma discharge environment.

Multicomponent gas detection based onconcise CW-cavity ring-down spectroscopywith a bow-tie design

Jinduo Wang, Jin Yu, Ze Mo, Jianguo He, dai shoujun, Jing Meng, Yang Liu, xue zhang, and Hong Yi

Doc ID: 351299 Received 09 Nov 2018; Accepted 25 Feb 2019; Posted 07 Mar 2019  View: PDF

Abstract: A concise open-path CW-CRDS with a bow-tie cavity structure is demonstrated inthe single and dual optical paths experiments for multicomponent gas detection, e.g.greenhouse gases concentration evaluation in ambient air. Owing to its features of opticalfeedback suppression and small free spectral range (FSR), the bow-tie configuration shows itsspecial advantages in the realization of both a compact arrangement and two counterpropagatingnon-interference optical paths. The minimum of the Allan deviation reaches 1.6× 10-10 cm-1 for an integration time of 100 seconds, corresponding to the noise equivalentabsorption coefficient of 1.6 × 10-9 cm-1 Hz-1/2. The detection sensitivity of methane isdeduced to be 0.9 ppbv with its absorption cross section of 1.48 × 10-20 cm2/molecule in the512 decays averaging mode. A wavelength-correction method is proposed to reduce by about30% of the uncertainty in the measurements caused by the deviation in the wavelengthresonance between incident laser and ring-down cavity. The concentrations of greenhousegases in ambient air are measured by the open-path CW-CRDS with the uncertainties of 0.02,100 and 10 ppmv for CH4, H2O, and CO2, respectively.

Glucose sensing by absorption spectroscopyusing lensed optical fibers

Silje Fuglerud, Karolina Milenko, Reinold Ellingsen, Astrid Aksnes, and Dag Hjelme

Doc ID: 351345 Received 08 Nov 2018; Accepted 23 Feb 2019; Posted 25 Feb 2019  View: PDF

Abstract: The bulkiness of common transmission spectroscopy probes prevents applicabilityat remote locations such as within the body. We present the fabrication and characterizationof lensed fibers for transmission spectroscopy in the near infrared. Eigenmode simulationsand measurements of the coupling efficiency are presented and applied to design the setupcorresponding to the sample absorption. Sensing capabilities are demonstrated on aqueousglucose samples ranged 80 to 500mm obtaining a mean absolute percentage error of calibrationof 4:3%. With increased flexibility, transmission spectroscopic sensors at remote locations maybe achievable, for example applied to in vivo continuous glucose monitoring.

Optomechanical transistor: Controlling theoptical bistability in a photonic molecule

Huajun Chen, jian-yong yang, de-ming zhao, and hong-wei wu

Doc ID: 356340 Received 09 Jan 2019; Accepted 23 Feb 2019; Posted 25 Feb 2019  View: PDF

Abstract: We theoretically investigate the optical bistability in a composite photonicmolecule cavity optomechanical system consisting of two whispering-gallery-modemicrocavities, where one of the optical cavity is optomechanical with high quality factor andthe other optical cavity is an auxiliary cavity with high cavity dissipation. With controllingthe coupling strength J between the two cavities determined by their distance, the decay rateratio δ of the two cavities, and the pump power P , the optical bistability can be controlled.Further, the transmission spectrum of the signal field can be efficiently attenuated oramplified, depending on the power of a second ‘gating’ (pump) field P , and otherparameters. Our study for photonic-molecule optomechanics systems may be a promisingcandidate for single-photon transistors and pave the way for potential applications in quantuminformation technologies.

Design of bottle beam based on dual-beam fortrapping particles in air

Zhikun Yang, Xinglei Lin, He Zhang, Xiaohui Ma, Yonggang Zou, Xu Li, Yingtian Xu, and Liang Jin

Doc ID: 356487 Received 02 Jan 2019; Accepted 22 Feb 2019; Posted 22 Feb 2019  View: PDF

Abstract: An optical system structure of a tunable bottle beam was designed to capturemicron absorbing particles in air. Using 670 nm semiconductor laser as a light source, bottlebeam was formed by beam shaping elements, double-axicon lens, and parabolic annularmirrors. Taking carbon nanoclusters particle as an example, the capturing effect of bottlebeam on particle was analyzed. By adjusting the size of the bottle beam, the captureperformance of particles with different diameters could be optimized. When the optical powerof the conical doughnut hollow beam was P=0.05W, the composite bottle beam could capturecarbon nanoclusters particle under 7μm.

Towards predicting removal rate & surfaceroughness during grinding of optical materials

Tayyab Suratwala, William Steele, Lana Wong, Philip Miller, Eyal Feigenbaum, Nan Shen, Nathan Ray, and Michael Feit

Doc ID: 351288 Received 19 Nov 2018; Accepted 22 Feb 2019; Posted 01 Mar 2019  View: PDF

Abstract: A series of controlled grinding experiments, utilizing loose or fixed abrasives of either alumina or diamond atvarious particle sizes, were performed on a wide range of optical workpiece materials [single crystals of Al2O3(sapphire), SiC, Y3Al5O12 (YAG), CaF2, and LiB3O5 (LBO); a SiO2-Al2O3-P2O5-Li2O glass ceramic (Zerodur); and glassesof SiO2:TiO2 (ULE), SiO2 (fused silica), and P2O5-Al2O3-K2O-BaO (Phosphate)]. The material removal rate, surfaceroughness, and the morphology of surface fractures were measured. Separately, Vickers indentation wasperformed on the workpieces, and the depths of various crack types as a function of applied load was measured.Single pass grinding experiments showed distinct differences in the spatial pattern of surface fracturing betweenthe loose alumina abrasive (isolated indent-type lateral cracking) and the loose or fixed diamond abrasive(scratch-type elongated lateral cracking). Each of the grinding methods had a removal rate and roughness thatscaled with the lateral crack slope, sℓ (i.e. the rate of increase in lateral crack depth with the applied load) of theworkpiece material. A grinding model (based on the volumetric removal of lateral cracks accounting forneighboring lateral crack removal efficiency and the fraction of abrasive particles leading to fracture initiation)and a roughness model (based on the depth of lateral cracks or the interface gap between the workpiece and lap)are shown to quantitatively describe the material removal rate and roughness as a function of workpiece material,abrasive size, applied pressure and relative velocity. This broad, multi-process variable grinding model can serveas a predictive tool for estimating grinding rates and surface roughness for various grinding processes on differentworkpiece materials.

Performance of zoom homogenizer to controlsize of illumination field

Taeshin Kim, Seungjin Hwang, DaeWoong Park, and Tae Jun Yu

Doc ID: 356506 Received 02 Jan 2019; Accepted 21 Feb 2019; Posted 22 Feb 2019  View: PDF

Abstract: We have performed the numerical simulation and the experiment of the zoomhomogenizer and the conventional beam homogenizer. The numerical simulation was performedfor each lenslet using the shifted angular spectrum method for effective memory use. In theexperiment, parameters of zoom homogenizer and beam homogenizer at all zoom positions wereset using system matrix. The uniformity and the peak effect of the beam homogenizer were16.57%, and 16.63%, respectively, but those of the zoom homogenizer were 7.15% and 1.46%,respectively. The illumination field generated by the zoom homogenizer had higher uniformityand lower peak effect at all zoom positions than conventional one.

Design and Simulation of a Target Scene Generator withTelecentric Structure in the Image Space

Shuqing Zhang, Zhou Luyang, lu min, and Yefei Wang

Doc ID: 354480 Received 03 Dec 2018; Accepted 21 Feb 2019; Posted 21 Feb 2019  View: PDF

Abstract: Due to the high reflectivity of the resistor array in the target scene generator (TSG), the narcissus effect caused bythe resistor array is notorious. Based on the paraxial analysis of resistor array, the telecentric structure in theimage space is proposed to reduce the narcissus effect induced by the resistor array. A TSG with the telecentricstructure in the image space and a TSG with the nontelecentric structure in the image space, which have samesystem parameters, are designed and optimized. The nonsequential ray tracing technique is used for both TSGs toevaluate the narcissus effect induced by the resistor array. The simulation results show that using telecentricstructure in the imaging space is an effective method to suppress the narcissus signal caused by the resistor array.

Tolerance analysis on decenter error of multi-layerdiffractive optical elements based on polychromaticintegral diffraction efficiency

Shan Mao and Jianlin Zhao

Doc ID: 347862 Received 17 Oct 2018; Accepted 19 Feb 2019; Posted 20 Feb 2019  View: PDF

Abstract: The decenter error can determine the polychromatic integral diffraction efficiency (PIDE) over broad waveband ofhybrid optical systems and further the imaging quality. Mathematical model of the relationship between thedecenter error and the PIDE of multi-layer diffractive optical elements (MLDOEs) is presented and the expressionsare derived based on phase delay of diffractive optical elements (DOEs) for both normal and oblique incidentsituations. Finally, the sensitivity of PIDE to the decenter error for MLDOEs used in long-infrared waveband withmaterial combination of ZNS-ZNSE is analyzed and then the decenter error tolerance is proposed to ensure highPIDE over broad waveband as well as diffraction efficiency at the designed wavelengths. The analysis methods andresults could be useful for guiding the decenter error of MLDOEs in hybrid optical systems for optical engineers.

Exploring the Limits of Semiconductor Laser-basedOptical Frequency Combs

Peter Delfyett, Anthony Klee, Kristina Bagnell, Paul Juodawlkis, Jason Plant, and a zaman

Doc ID: 355096 Received 12 Dec 2018; Accepted 19 Feb 2019; Posted 20 Feb 2019  View: PDF

Abstract: We report a study on the performance limits of stabilized optical frequency combs from semiconductor modelocked diode lasers. Operating characteristics such as the number of comb lines, comb tooth linewidth, the physicalparameters that affect the independent control of pulse repetition rate and offset frequency, and the potential forself-stabilization are explored.

Experimentally measuring a detectability index of acomputational imaging system

Bradley Preece, David Haefner, and George Nehmetallah

Doc ID: 352837 Received 10 Dec 2018; Accepted 15 Feb 2019; Posted 26 Feb 2019  View: PDF

Abstract: Computational imaging (CI) systems is an enabling technology for multifunctional cameras capable of performing awide variety of imaging tasks. However, given the complexity of CI systems it is often difficult to characterize theirperformance. In this research, a novel measurement technique is proposed and tested to evaluate the performanceof complex non-shift invariant linear CI systems performing a detection task at the system level. The performanceis characterized using detectability indexes, such as an average Hotelling’s statistic (t2). The proposedmeasurement technique relies on a previously developed general CI system framework. The detectability predictsthe upper bounded signal to noise ratio of a linear algorithm through evaluation of a matched filter. Theexperimental results are compared with theoretical expected values through the Night Vision IntegratedPerformance Model (NV-IPM) and Monte-Carlo simulations. We demonstrate the experimental results for a varietyof target sizes, colors, and brightness on different colored flat backgrounds. Our results demonstrate how thedetectability indexes can provide valuable insight into the final system performance. Finally, the measurementtechnique is used to compare the detection performance between two different cameras.

Performance evaluation of continuous-wave midinfraredwavelength conversion in silicon waveguides

Qiang Jin, Taoce Yin, Zhihua Tu, Daru Chen, Yaocheng Shi, Daoxin Dai, and Shiming Gao

Doc ID: 352348 Received 19 Nov 2018; Accepted 15 Feb 2019; Posted 04 Mar 2019  View: PDF

Abstract: Continuous-wave (CW) mid-infrared (MIR) wavelength conversion is experimentally demonstrated usingdegenerate four-wave-mixing (FWM) between two thulium-doped fiber (TDF) lasers in a silicon waveguide. OneTDF laser is home-made with high power and tunable wavelength, and the other one is commercial. The conversionefficiency is measured with respect to the pump power and the signal wavelength detuning. In the 2-μm MIR band,the measured 3-dB conversion bandwidth is 52 nm. It verifies the feasibility of FWM-based wavelength conversionbased on silicon waveguides in future MIR optical communication systems.

Verification of integral figure of merit for mid-IR nonlinear crystals

Andrey Ionin, Igor Kinyaevskiy, Adilya Sagitova, and Yury Andreev

Doc ID: 355958 Received 28 Dec 2018; Accepted 13 Feb 2019; Posted 22 Feb 2019  View: PDF

Abstract: Examination and verification of a simple integral figure of merit for nonlinearcrystals taking into account different crystal properties were performed. The examination wascarried out on the basis of experimental data on the broadband sum frequency generation ofCO laser radiation in ZnGeP2, BaGa2GeSe6, AgGaSe2, GaSe and PbIn6Te10 mid-IR nonlinearcrystals. The figure of merit taking into account spectral and angular phase-matchingbandwidths provides the best agreement with the experiment and can be applied forqualitative and even for quantitative comparison of the nonlinear crystals..

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.

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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