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Unilateral-shift-subtracting confocal microscopy withnanoscale axial focusing precision

Yingbin Sun, Weiqian Zhao, Lirong Qiu, Yun Wang, and Rongji Li

Doc ID: 330955 Received 14 May 2018; Accepted 18 Sep 2018; Posted 18 Sep 2018  View: PDF

Abstract: A novel unilateral-shift-subtracting confocal microscopy (USSCM) method with nanoscale axial focusing precisionis proposed based on the optical arrangement of conventional confocal microscopy (CM). As the two segments ofdata on both sides of the confocal axial response curve are very sensitive to variations of the axial position, USSCMintroduces an axial shift of S for one segment, to intersect it with the other segment. It then separately interpolatesthe two segments of intersecting data, subtracts the corresponding interpolated data, and selects the data thatexhibit a good linearity from all of the subtracted data to fit a straight line. It calculates the zero-position of thefitting line and offsets it by S/2, to precisely reveal the focus position of the confocal system, and thereby achievinghigh-precision imaging of the three-dimensional sample’s structure. Theoretical analyses and preliminaryexperiments indicate that, for the excitation wavelength of λ = 405 nm, numerical aperture of NA = 0.95, andnormalized axial shift of S = 5.21, USSCM achieves an axial resolution of 3 nm and a repetitive focusing precision of1.5 nm, while it does not change the lateral resolution of CM. Furthermore, compared with the conventionalconfocal microscopy, under the same noise condition, USSCM is less affected by the system aberration, which leadsto the higher focusing precision. These findings demonstrate that USSCM is a very efficient method for imaging.

Binary Code DOE optimization for speckle suppression in laser display

Victor Yurlov, Anatoliy Lapchuk, Kyunghun Han, Seong-Jin Son, Bok Hyeon Kim, and NanEi Yu

Doc ID: 335535 Received 18 Jun 2018; Accepted 18 Sep 2018; Posted 18 Sep 2018  View: PDF

Abstract: Using laser light source in the imaging devices provides wide color gamut, high brightness, resolution and efficiency. At the same time it creates speckle pattern deteriorating the image quality. The article is related to the application of the moving binary code DOE for speckle suppression in the laser display. The analytical optimization of the DOE parameters is made in the article. The optimal DOE pitch is found analytically. The limitation of the DOE code length is shown and the highest possible code length is estimated. The application of the compound Barker code for DOE design is suggested. As an alternative the M-sequence and minimum peak sidelobe codes are considered. The expected residual speckle contrast ratio after application of those codes is estimated for the number of codes. The comparison of the different codes is done and the recommendations for speckle suppression DOE design are provided.

Transport-of-intensity holographic data storage basedon computer-generated hologram

Naru Yoneda, Yusuke Saita, Koshi Komuro, Teruyoshi Nobukawa, and Takanori Nomura

Doc ID: 341213 Received 02 Aug 2018; Accepted 18 Sep 2018; Posted 18 Sep 2018  View: PDF

Abstract: To increase the recording density of computer-generated-hologram-based holographic data storage (CGHHDS),a phase-datapage reconstruction method by the transport of intensity equation (TIE) is proposed.The TIE generally requires a scanning image sensor because the phase retrieval process needs at least twodefocused intensity distributions. Although the TIE is applied, the proposed method enables to detectthe distributions simultaneously by utilizing an extra conjugate component reconstructed from the CGH.Experimental results show that the proposed method allows reconstructing a phase-datapage without anyadditional elements, which keeps the optical setup simple and low cost.

Three-dimensional imaging system with bothimproved lateral resolution and depth of fieldconsidering non-uniform system parameters

Hui Yun, Anabel Llavador, Genaro Saavedra, and Myungjin Cho

Doc ID: 341465 Received 06 Aug 2018; Accepted 18 Sep 2018; Posted 18 Sep 2018  View: PDF

Abstract: In this paper, we propose a new 3D passive image sensing and visualization technique to improve lateral resolutionand depth of field of integral imaging simultaneously. There is a resolution tradeoff between lateral resolutionsand depth of field in integral imaging. For overcoming this issue, a large aperture and a small aperture can be usedto record the elemental images for reducing the diffraction effect and extending the depth of field, respectively.Therefore, in this paper, we utilize these two pickup concepts with non-uniform camera array. To show thefeasibility of our proposed method, we implement an optical experiment. For comparison in details, we calculatethe peak signal to noise ratio (PSNR) as the performance metric.

Polarization imaging using an anisotropic diffractiongrating and liquid crystal retarders

Kohei Noda, Ryusei Momosaki, Jou Matsubara, Moritsugu Sakamoto, Tomoyuki Sasaki, Nobuhiro Kawatsuki, Kohei Goto, and Hiroshi Ono

Doc ID: 335715 Received 21 Jun 2018; Accepted 17 Sep 2018; Posted 18 Sep 2018  View: PDF

Abstract: We present a simple yet versatile, and practical polarization camera, for imaging full Stokes parameters. Thedeveloped system consists of one anisotropic diffraction grating plate and two electro-switchable retarders, andobtains in nearly real time full Stokes images of the light scattered from the objects. The monochromatic S3 imageis obtained by physically separating the right and left circularly polarized components with the aid of theanisotropic grating, and S1 and S2 images by fast electro-switching the retardation of each retarder. The simplepolarization imaging system is possible to be applied to various types of imaging systems, and especially should beincorporated into the optical microscope as well as imaging camera in the future work.

Immunosensing platform with large detection rangeusing excessively tilted fiber grating coated withgraphene oxide

Bin-bin Luo, Huafeng Lu, Shenghui Shi, Jiao Lu, M Zhao, Shengxi Wu, Lingchen Li, Xin Wang, and Yajie Wang

Doc ID: 340005 Received 19 Jul 2018; Accepted 17 Sep 2018; Posted 18 Sep 2018  View: PDF

Abstract: We report an immunosensing platform with large detection range using excessively tilted fiber grating (ExTFG) coatedwith graphene oxide (GO). ExTFG was inscribed in standard single mode fiber, GO film was coated on the fiber surfacethrough hydrogen bond. The effectiveness and uniformity of GO deposited on ExTFG surface were investigated by fieldemission scanning electron microscopy and energy spectrum method. Bovine serum albumin (BSA) monoclonalantibodies (MAbs) were used as biometric unit to link on GO film through covalent bond for the specific detection of BSA,so as to evaluate the performances of the proposed biosensor. The whole dynamic immobilization process of BSA MAbsand BSA detection were observed by the spectral evolution of the sensor. Experimental results show that the fabricatedGO-coated ExTFG biosensor has a large detection range from 1.5 nM to 75 nM and fast response for BSA antigen, the limitof detection (LOD) is ~0.88 nM by using optical spectrum analyzer with a resolution of 0.03nm, and the dissociationconstant KD and the affinity constant KA is calculated to be ~6.66×10-9 M and ~1.5×108 M-1, respectively. The proposed GOcoatedExTFG immunosensing platform could lay a foundation for the specific detection of other biomolecules.

2 W single-frequency, low-noise 509 nm laser via single-pass frequency doubling of an Yb-doped fiber amplifier

Jiaping Qian, Lei Zhang, Huawei Jiang, Shenzhen Cui, Jiaqi Zhou, and Yan Feng

Doc ID: 340535 Received 23 Jul 2018; Accepted 17 Sep 2018; Posted 18 Sep 2018  View: PDF

Abstract: A single-frequency low-noise green laser at 509 nm is developed for the study of cesium Rydberg atoms. The laser is generated by single-pass second harmonic generation of an Yb-doped fiber amplifier at 1018 nm in a periodically poled MgO-doped lithium-niobate crystal. Up to 2.03 W 509 nm laser is obtained with 10.04 W incident 1018 nm laser with a conversion efficiency of 20.2%. The linewidth of the 509 nm laser is estimated to be 40 kHz according to the measured linewidth 20 kHz of the 1018 nm fundamental laser. The relative intensity noise is 0.038% rms integrated from 10 Hz to 10 MHz.

Identification of Huanglongbing-infected Navelorange Based on Laser-Induced BreakdownSpectroscopy combined with different chemometricmethods

gangfu rao, Lin Huang, Muhua Liu, tianbing chen, Jinyin Chen, ZIYI LUO, FANGHAO XU, Xuehong Xu, and Mingyin Yao

Doc ID: 342421 Received 16 Aug 2018; Accepted 17 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: In order to realize rapid identification of Gannan navel orange infected by Huanglongbing (HLB), a full opticaldiagnostic method of laser-induced breakdown spectroscopy (LIBS) was proposed. All navel oranges werecollected from Ganzhou, Jiangxi, China, and samples contain healthy and HLB-infected. The LIBS spectra of theplasma plume were collected directly from the epidermis of these navel oranges. The navel orange LIBS spectra inthe wavelength range of 200~1050 nm were pretreated with smoothing and multiple scatter correction (SM+MSC);on the basis of 10×10-fold cross validation, random forest (RF) model based on continuous wavelet transform(CWT) and principal component analysis (PCA) was analyzed to identify the navel orange of HLB. The resultsshowed that the PCA-RF and CWT-RF models coupled with suitable methods in preprocessing data can identifyHLB-infected navel oranges. The average accuracy obtained from the CWT-RF model was 96.86%% in training set,and 97.45%% in test set; the average accuracy by PCA-RF model was 97.64% in training set, and 97.89% in test set.The overall results demonstrate that LIBS combined with CWT-RF or PCA-RF, as a valuable analytical tool, could beused for HLB-infected navel orange identification.

Effective wind and temperature retrieval from Dopplerasymmetric spatial heterodyne (DASH) spectrometerinterferograms

Jilin Liu, Daikang Wei, Yajun Zhu, Martin Kaufmann, FRIEDHELM OLSCHEWSKI2, Klaus Mantel, Jiyao Xu, and Martin Riese

Doc ID: 341724 Received 06 Aug 2018; Accepted 17 Sep 2018; Posted 19 Sep 2018  View: PDF

Abstract: This paper presents a method for wind velocity andDoppler temperature retrieval from interferograms of aDoppler asymmetric spatial heterodyne (DASH) spectrometer.This method is based on the analytic representationof the signal and the subsequent algorithms.It turns out to be more robust than the conventionalFourier transform method at low SNR. The influenceof optical dispersion on the accuracy of the retrievedparameters is also characterized. The effective opticalpath difference is suggested for use in wind andtemperature retrieval routines. Computer simulationsare used to characterize the accuracy of the proposedmethod, in particular regarding the influence of opticaldispersion.

Efficient Points Cloud Lossless Data Compression Method based on EmbeddedGray-code Structured Light Pattern Sequence

Hossein Rashidizad, MohmmadMorad Sheikhi, and Gholamreza Akbarizadeh

Doc ID: 340230 Received 19 Jul 2018; Accepted 17 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: Despite the benefits derived from the development of three-dimensional techniques to improve the acceleration and accuracy of 3d scanningoperations over the past two decades and its wide range applications in the various industries (such as quality control and inspection, reverseengineering and robotics), there are restrictions on data transfer, data storage, or even the development of real-time scanning methods due to theenlarging data size (points cloud). According to the importance of maintaining all the output data of the scanner in instrumentation engineering, theneed to apply minimum loss or lossless data compression algorithms is more than ever evident. In this regard, the paper presents a novel method inpoints cloud lossless data compression, using a Gray code structured light pattern sequence and image-based compression. The empirical evaluationand results of the proposed method demonstrate that this idea is reliable and practical to achieve a distinct compression ratio among other losslesspoint cloud compression methods.

Suprathreshold gray scale is implied by thresholds

Robert Carter

Doc ID: 340766 Received 26 Jul 2018; Accepted 15 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: The inverse of the threshold JND (i.e., 1/JND) is proportional to the slope (derivative with respect tovisual stimulus luminance) of the suprathreshold gray scale at any stimulus and background luminances.Specifically, the inverse threshold and the gray-scale slope share 81% of their variance over six log units of targetluminance; in log-log coordinates 92% of their variance is shared. The strength of the connection improves whennegative or positive contrasts are considered separately. Scientific literature is cited, empirical evidence ispresented, results of theoretical calculations are discussed and applications are described. For instance,suprathreshold gray scale appearance is important in medical imaging, video rendering, industrial process displays,public information displays (e.g., at airports), military situation displays, multispectral and other abstract scientificimaging, artistic lighting design (e.g., equal-appearing steps of gray scale), and color coding of text, image segmentsor symbols for rapid reliable visual search.

Rotation-as-fast-axis scanning-probe X-ray tomography: the importance of angular diversity for fly-scan modes

Daniel Ching, Mert Hidayetoglu, Tekin Bicer, and Doga Gursoy

Doc ID: 341301 Received 31 Jul 2018; Accepted 15 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: We investigate the effects of angular diversity on image reconstruction quality of scanning-probe X-ray tomography for both fly- and step-mode data collection. We propose probe coverage maps as a tool for both visualizing and quantifying the distribution of probe interactions with the object. We show that data sampling with more angular diversity yields better tomographic image reconstruction as long as it does not come at the cost of not covering some voxels in the object. Therefore, for fly-mode data collection, rotation-as-fast-axis trajectories (RAFA) are superior to raster or other non-RAFA trajectories, because they allow increasing angular diversity without sacrificing spatial coverage uniformity. Whereas for step-mode data collection and a fixed measurement budget, increasing angular diversity can come at the cost of not covering some voxels, and may not be desired. This study has implications for how the scanning-probe microscopes should be collecting data in order to make the most of limited resources.

Off-axis Eight-pass Neodymium glass laseramplifier with high efficiency and excellentenergy stability

Yao Ke, Song Gao, Tang Jun, Xudong Xie, Chen Fan, Zhenhua Lu, Xuejun Fu, Mengqiu Fan, Xiaocheng Tian, Bo Zhang, Xibo Sun, Dangpeng Xu, Kuixing Zheng, Lanqin Liu, Zhitao Peng, and Jingqin Su

Doc ID: 335791 Received 26 Jun 2018; Accepted 14 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: A new relay-imaged off-axial eight-pass laser amplifier with several joules energyand 1Hz repetition rate was demonstrated. The extraction efficiency and pulse-to-pulseenergy stability was greatly improved. Under the single-pass small-signal gain of 3.6, the netgain of 900 and the effective extraction efficiency of 42.4% in the beam aperture wererealized. The pulse-to-pulse energy stability of 0.83% (peak-valley) and 0.17% (root-meansquare)were achieved by the significant saturation of eight-pass amplification, to the best ofour knowledge which is the best energy stability at the several-joules-class amplifiers. The farfield quality was 2.52 times the diffraction limit and the near field modulation of 90% beamaperture is 1.28. No parasitic oscillations or pencil beams were observed. Moreover, anotherkey feature of the proposed amplifier was the ability of remarkably improving the pulsecontrast by a unique design.

Optimization method of multilayer diffractive opticalelements with consideration of ambient temperature

Mingxu Piao, Qingfeng Cui, Bo Zhang, and Chunzhu Zhao

Doc ID: 342051 Received 10 Aug 2018; Accepted 14 Sep 2018; Posted 18 Sep 2018  View: PDF

Abstract: A method for optimal design of multilayer diffractive optical elements (MLDOEs) with consideration of ambienttemperature is presented to improve the image quality over the entire temperature range. The relationship betweendiffraction efficiency and temperature is analyzed, and optimization process of surface relief height for the MLDOEsis given. A practical 3~5μm athermal hybrid optical system with a double-layer diffractive optical element is designedin temperature range from -20°C to 60°C, and the image quality of two hybrid optical systems with optimized MLDOEand original MLDOE is compared. The result shows that the comprehensive MTF is obviously improved in the wholeworking temperature range. This method can be used during the passive athermalization hybrid optical systemdesign with MLDOE.

Active lens for thermal aberration compensation inlithography lens

lei zhao, lijian dong, Yu Xinfeng, pengzhi li, and Yanfeng Qiao

Doc ID: 338258 Received 09 Jul 2018; Accepted 13 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: High laser absorption and strong resolution enhancement technology make thermal aberration control oflithography lens more challenging. We present an active lens that uses four bellows actuators to generateastigmatism (Z5) on the lens surface. The apparatus utilizes optical path difference (OPD) to compensate systemwavefront. In order to assess the specifications of the compensator, finite element method (FEM) and experimentalanalyses are carried out to obtain and validate the general properties of the apparatus. The results show that Z5deformation quantity of lens upper surface exceeds 600nm; Z5 coefficient accuracy is better than +/−1nm. Theapparatus can be an efficient compensator for thermal aberration compensation, especially aberration caused bythe dipole illumination.

Passive compensation of intensity and polarizationinducednoises by quadrature demodulationtechnique in resonator optic gyroscope

Ning Liu, Yanxiong Niu, Li Shuang Feng, Hongchen Jiao, and Xiao Wang

Doc ID: 340353 Received 20 Jul 2018; Accepted 13 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: Polarization-induced noise is a dominant noise, which seriously hinders the progress of resonator optic gyroscope(ROG). Many countermeasures have been developed but showed insufficient performance. In this paper, wepropose a quadrature demodulation technique (QDT), which adopts references of both sine and cosine todemodulate the signal. The theoretical analyses of polarization effect and QDT are showed and experimentalresults are listed and compared. The experimental results are consistent with theoretical analysis. The QDT showsgreat performance in suppressing the environment and polarization induced phase fluctuation of signal. And wewill also demodulate the intensity-dependent coefficient of 2Ωt term, which is demonstrated effective forcompensating the polarization-induced intensity noise together with the QDT. The scheme shows significantprogress in improving the long term stability.

Full Field Optical Coherence Tomography in a Balanced Detection Mode

Boris Buchroithner, Andrii Prylepa, Paul Wagner, Stefan Schausberger, David Stifter, and Bettina Heise

Doc ID: 318349 Received 05 Jul 2018; Accepted 13 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: We discuss balanced time-domain full field optical coherence tomography (FF-OCT) realized in a Mach- Zehnder configuration. The balanced detection scheme and spatial phase shifting allow single-shot acquisition and reconstruction in FF-OCT. Combined with a 2D quadrature signal-based demodulation technique applying the Riesz transform, previously illustrated for a dual-shot temporal phase shifting in FF-OCT, we demonstrate the concept for single-shot spatial phase shifting. The monitoring of dynamic processes by time-domain FF-OCT is enabled by this approach. However, it demands an accurate registration of both spatially shifted interferograms.

Assessing surface characteristics of eroded dentinewith optical coherence tomography: a preliminary invitro validation study

Madiha Habib, Kuan Ming Lee, Yih Miin Liew, Christian Zakian, Ngie Min Ung, and Hooi Pin Chew

Doc ID: 330811 Received 13 Jun 2018; Accepted 13 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: We conducted the first pilot study to investigate the use of attenuation coefficient from OCT backscattered signal asa measure of surface roughness changes in eroded dentine at an early stage of the erosion process. Ten humanpremolar root samples were subject to citric acid treatment before scanning by OCT. The extracted relativeattenuation coefficient (μR) from backscattered OCT signal was shown to increase with the duration of acidchallenge. Validated against roughness measurements (rSa) from scanning electron microscopy (SEM) scans, μR issignificantly correlated with rSa indicative of severity of erosion (p < 0.01, r = 0.9195). We conclude that OCTattenuation coefficient of the immediate sub-surface in eroded dentine is a potential surrogate measure for itssurface roughness. However further work should be performed to study how it relates to the surface andimmediate subsurface changes effected by other mechanical wear before it could unequivocally be used as asurrogate measurement for surface roughness.

New method for measurement of refractive indexprofile of waveguides using Defocusing Microscopy

Eduardo Lages, Wilder Cardoso, Gustavo Almeida, Livia Gomes, Oscar Mesquita, Cleber Mendonca, Ubirajara Agero, and Sebastiao de Padua

Doc ID: 323371 Received 15 Feb 2018; Accepted 13 Sep 2018; Posted 13 Sep 2018  View: PDF

Abstract: Defocusing Microscopy (DM) is a bright-field optical microscopy technique often used to obtain structuralparameters of objects with low difference in refractive index in relation to the surrounding medium(phase objects). We show an use of this technique to measure the refractive index (n) profile of waveguidesproduced by femtosecond laser micromachining inside the bulk of a sodalime glass. The resultsare used to analyse the influence of production parameters on n. The methodology requires only a brightfieldoptical microscope and has proved to be easily applied. Results provide important insights on thewaveguide microfabrication process, since translation speed, rather than intensity, has shown to be moreimportant for achieving greater variations in refractive indices. Index of refraction differences betweenthe waveguide and the substrate of the order of 10􀀀4 were measured for a series of straight waveguidesfabricated with different parameters. Low sample scan speeds and pulse energies near 1.20 mJ used forfabrication showed the highest values of refractive index change for waveguides in sodalime glasses.

The halo in the box: a macroscopic crystalarrangement to project mosaic halos

Markus Selmke and Sarah Selmke

Doc ID: 333036 Received 04 Jun 2018; Accepted 12 Sep 2018; Posted 12 Sep 2018  View: PDF

Abstract: We describe a three-dimensional (3D) halo demonstration experiment: A volumetric arrangement of crystalsis used to project a mosaic halo display upon illumination. The demonstration can be used to conveythe collective scattering aspect of the natural halo mechanism and at the same time to vividly portray theconcept of orientation classes in the context of halo theory.

A method for estimating the Stark splitting of rare-earth ions from the measured cross-section spectra

Xiaoyun Tang, Qun Han, Xueru Zhao, Huiling Song, Kun Ren, and T. Liu

Doc ID: 335034 Received 02 Jul 2018; Accepted 12 Sep 2018; Posted 12 Sep 2018  View: PDF

Abstract: In this paper, a method to estimate the Stark levels of the rare-earth(RE) ions of a RE-doped fiber from the measured emission and absorption cross-sections are proposed. The method is based on the McCumber theory, which can calculate the emission/absorption cross-sections from the given Stark levels. By fitting the calculated emission/absorption spectra to the measured ones through a numerical optimization process, the Stark levels of the RE can be determined. As examples, the Stark levels of related manifolds of Er3+ and Yb3+-ions in fibers and doped-glasses have been determined by the proposed method. Then the data were used to analyze the temperature-dependent population of theses Stark levels. This method avoids the difficulties in direct measurement of such parameters in a cryogenic temperature environment. It is important to the evaluation of the thermal load/distribution and design of the thermal management system of high-power fiber lasers and amplifiers.

Bandpass sampling-based heterodyne interferometersignal acquisition for vibration measurements inprimary vibration calibration

Ming Yang, Haijiang Zhu, CHENGUANG CAI, Ying Wang, and Zhihua Liu

Doc ID: 334580 Received 26 Jun 2018; Accepted 12 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: Heterodyne interferometers have been widely used for primary vibration calibration in recent years. Primaryvibration calibration performance depends on the precision and real-time nature of vibration measurements,factors determined by the acquisition and demodulation of the heterodyne interferometer signal. This signal iscommonly collected using the Nyquist sampling method, requiring the devices with high sampling rates and largememories, or a sampling method using a mixer and lowpass filter, the analog devices which may create time delays.This study proposes a novel bandpass sampling method, reducing sampling rate and storage capacity withoutgenerating time delays. To improve vibration measurement precision, an optimal sampling rate is designed tocollect the heterodyne interferometer signal, and the collected signal is demodulated using the phase unwrappingsine approximation method. The proposed method is compared with existing methods through simulated andexperimental data. Experimental results show the proposed method avoids time delays and high sampling rateswhile providing high-precision vibration measurements.

Non-linear wavefront reconstruction methodsfor pyramid sensors using Landweber andLandweber-Kaczmarz iteration

Victoria Hutterer and Ronny Ramlau

Doc ID: 338560 Received 17 Jul 2018; Accepted 12 Sep 2018; Posted 13 Sep 2018  View: PDF

Abstract: Accurate and robust wavefront reconstruction methods for pyramid wavefront sensorsare in high demand as these sensors are planned to be part of many instruments currently underdevelopment for ground based telescopes. The pyramid sensor relates the incoming wavefront andits measurements in a non-linear way. Nevertheless, almost all existing reconstruction algorithmsare based on a linearization of the model. The assumption of a linear pyramid sensor responseis justifiable in closed loop AO when the measured phase information is small but may not bereasonable in reality due to unpreventable errors depending on the system such as non commonpath aberrations. In order to solve the non-linear inverse problem of wavefront reconstructionfrom pyramid sensor data we introduce two new methods based on the non-linear Landweber andLandweber-Kaczmarz iteration. Using these algorithms we experience high-quality wavefrontestimation especially for the non-modulated sensor by still keeping the numerical effort feasiblefor large-scale AO systems.

Method to improve the resolution of a non-parallelFabry-Pérot Etalon

Xusheng Xia, Hong Yuan, Jinbo Liu, Baodong Gai, Xianglong Cai, jingwei Guo, Yuqi Jin, and Fengting Sang

Doc ID: 341285 Received 06 Aug 2018; Accepted 12 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: A new method to improve the resolution of a slightly non-parallel solid etalon is proposed. The methodis aimed to reduce the spectrum broadening caused by non-parallel surfaces; it contains a theoreticalformula for adjusting image distances, and an algorithm for processing the corresponding fringe patterns.Theoretical consideration, computer simulation, experimental results and application demonstration aregiven. The fringe patterns captured by CCD showed good agreement with the computer simulation, andthe resolution of a l/10-wave-front-error etalon was improved from 3.1 GHz to 0.51 GHz. In comparisonwith other methods, this new method is convenient and economical.

Easily-implemented approach for thecalibration of alignment and retardation errorsin a channeled spectropolarimeter

Xueping Ju, Bin Yang, Changxiang Yan, Junqiang Zhang, and Wenhe Xing

Doc ID: 340543 Received 24 Jul 2018; Accepted 11 Sep 2018; Posted 12 Sep 2018  View: PDF

Abstract: Calibration of the channeled spectropolarimeter is significant for the quantitativeapplication of this instrument. In current calibration methods for a channeledspectropolarimeter, an absolute angle between the coordinate system of an auxiliary polarizerand the global coordinate system of the instrument is usually indispensable. The effectivenessof calibration depends on the precision of the absolute angle, while it is usually difficult toachieve in practical calibration process. This paper presents an easily-implemented method tosimultaneously calibrate the alignment and retardation errors of high-order retarders for achanneled spectropolarimeter. In the presented method, the requirement of an absolute anglebetween the coordinate system of an auxiliary polarizer and the global coordinate system ofthe instrument is replaced by only rotating a relative angle in the coordinate system of theauxiliary polarizer itself. Firstly, we theoretically derive the modified reconstruction modelconsidering the alignment errors of high-order retarders. By analyzing and summarizing themodified reconstruction model, the calibration and compensation model of the alignment andretardation errors are further proposed. Then, two linearly polarized beams with a relativeangle of 45° between them are utilized to determine the alignment and retardation errors.Based on these results, the alignment and retardation errors can be compensated by a softwarecorrection algorithm without any precise mechanical adjustments. The effectiveness andfeasibility of the presented method is verified by numerical simulations and experiments. Theadvantage of easy implementation makes this calibration method more suitable to apply inlaboratory and on track for correcting the channeled spectropolarimeter.

Electro-optic phase modulation with a symmetrical metal-cladding waveguide

Xie He, Hailang Dai, Yuanlin Zheng, Yue Kong, and Xianfeng Chen

Doc ID: 336302 Received 27 Jun 2018; Accepted 11 Sep 2018; Posted 13 Sep 2018  View: PDF

Abstract: A bulk electro-optic (EO) modulator based on the ultrahigh-order guided modes (UOMs), which are excited in a symmetrical metal-cladding waveguide (SMCW), has been exploited. This kind of modes in SMCW has high sensitivity to phase shift by changing the refractive index of the guiding layer. Compared with phase modulation via the bulk EO modulator without waveguide, the applied half-wave voltage is reduced for one magnitude. This work may have the practical applications in optical information process.

VCSEL mode and polarization control by an ellipticdielectric mode filter

Lei Xiang, Xing Zhang, Jianwei Zhang, youwen huang, Werner Hofmann, Yongqiang Ning, and Lijun Wang

Doc ID: 332700 Received 29 May 2018; Accepted 11 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: In this paper, we demonstrate the effectiveness of polarizationmode control in vertical-cavity surface-emittinglasers (VCSELs) with integrated elliptic dielectric modefilters. The single-mode single-polarization laser operationis obtained by an irregularly shaped oval dielectricmode filter, aiming at cost-effective mass production.The orthogonal polarization suppression ratiowas measured to be 16.7 dB and the side-mode suppressionratio (SMSR) exceeded 30 dB. A single fundamentalmode power of 0.55 mW was achieved at a bias currentof 4 mA. We compared the spectra and near-fieldintensities of the dielectric mode filter VCSEL with areference device. The comparison clearly indicates theeffectiveness of our dielectric mode filter in controllingthe transverse- and polarization-mode propertiesof VCSELs.

Temperature dependent terahertz spectroscopy and refractive indexmeasurements of aqua soluble and plastic explosives

Ganesh Damarla, Mottamchetty Venkatesh, and Anil Chaudhary

Doc ID: 335656 Received 09 Jul 2018; Accepted 11 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: The paper reports the time domain temperature dependent terahertzspectroscopy of some premium aqua soluble and plastic explosives such as NH4NO3,TNT and RDX between 0.1 to 2.2 THz range. Tunable terahertz radiation wasgenerated using ZnTe crystal as a source and photoconductive antenna was used as adetector. The temperature dependent study was carried between 30-200 oC range in aspecially designed oven. The signature peaks of RDX and TNT present at 0.82and1.60 THz show the strong red shift whereas Ammonium Nitrate molecule showscomparatively small shift. The high temperature based red shift phenomenon is justopposite to the blue shift recorded at low temperature. In addition, the temperaturedependent absorption coefficients data of these molecules support the change in theconcentration of NO2 molecule. We have also ascertained the temperature dependentrefractive indices of these molecules between 0.1- 2.0 THz range. This confirms therole of temperature on the refractive indices. Finally, the signature peak of RDX withrespect to reduction of weight concentration of RDX in PTFE (Teflon) matrix wasstudied at 0.82THz.

Quarter-mode spoof plasmonic resonator formicrofluidic chemical sensor

Rong Lin Shao, Yong Jin Zhou, and Liu Yang

Doc ID: 340331 Received 20 Jul 2018; Accepted 11 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: In this paper, we propose a microfluidic chemical sensor based on the quartermodespoof plasmonic resonators with more compact overall size and higher sensitivity. First,a microfluidic channel engraved on polydimethylsiloxane (PDMS) is aligned to the upper partof the spoof plasmonic metal-insulator-metal (MIM) ring resonator where the strongestelectric fields are observed at resonance. Although a resonant frequency shift of 270 MHz hasbeen observed when the microfluidic channel is filled with pure ethanol, there is no resonantfrequency shift when the ethanol concentration is changed from 40% to 60%. Then the spooflocalized surface plasmons (LSPs) modes on the quarter corrugated MIM ring are analyzedand a microfluidic sensor based on the quarter-mode spoof plasmonic resonator has beenproposed. The proposed microfluidic sensor requires a very small amount (3.9 μL) of liquidfor testing. After infilling the microfluidic channel with pure ethanol, the resonant frequencyshift of 940 MHz has been observed on account to the dielectric changes. It is observed thatthe resonant frequency of proposed sensor shifts from 5.07 GHz to 6.62 GHz when theethanol concentration is varied from 10% to 90%. It has been demonstrated that such quartermodespoof plasmonic resonator is well suitable for a highly sensitive and compactmicrofluidic chemical sensor.

High power sampled-grating based MOPA system with .5 nm wavelength tuning around 970 nm

Mahmoud Tawfieq, Hans Wenzel, Pietro Della Casa, Olaf Brox, Arnim Ginolas, Peter Ressel, David Feise, Andrea Knigge, Markus Weyers, Bernd Sumpf, and Guenther Traenkle

Doc ID: 332945 Received 26 Jun 2018; Accepted 11 Sep 2018; Posted 12 Sep 2018  View: PDF

Abstract: Tunable high power diode lasers are key components in various established and emerging applications. In thiswork, we present a compact hybrid master oscillator power amplifier (MOPA) laser system. The system utilizes atunable GaAs based sampled-grating (SG) distributed Bragg reflector (DBR) laser as MO, which emits around awavelength of 970 nm in a single longitudinal mode with a spectral width below 20 pm. The SG-DBR laser consistsof two SGs, which each can be tuned thermally with micro-heaters. By tuning one of the two SGs, a discretewavelength tuning of 21.1 nm can be obtained, with a Vernier mode spacing of about 2.3 nm. By tuning both SGs, .5 nm of quasi-continuous tuning is obtained, with a mode spacing of about 115 pm. The coupling of the beamemitted by the MO into a tapered power amplifier provides an amplified output power in the watt range having anearly diffraction limited beam with a propagation factor of M21/e2 = 1.6. The combination of high power and widewavelength tuning in a compact system makes this light source ideal for, among others, nonlinear frequencyconversion.

An optically reconfigurable gate array using a coloredconfiguration

Takumi Fujimori and Minoru Watanabe

Doc ID: 331835 Received 21 May 2018; Accepted 11 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: This paper presents a proposal of an optically reconfigurable gate array using a colored configuration. Theoptically reconfigurable gate array consists of a very large scale integration (VLSI), a holographic memory,and four lasers with different wavelengths. The optically reconfigurable gate array VLSI includes a finegrainedprogrammable gate array as well as field programmable gate arrays. Four configuration contextscan be stored on the holographic memory and can be programmed onto the programmable gate arrayVLSI addressed by the four lasers. This paper presents the demonstration of the optically reconfigurablegate array using a colored configuration.

Calibration of three-dimensional laser Dopplervelocimeter in land integrated navigation system

Qi Wang, Xiaoming Nie, Chunfeng Gao, Jian Zhou, Guo Wei, and Xingwu Long

Doc ID: 336338 Received 27 Jun 2018; Accepted 10 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: In land navigation field, a laser Doppler velocimeter (LDV) which is able to measure the speed of a carrier can becombined with a strapdown inertial navigation system (SINS) to form an integrated navigation system. To realizethe integrated navigation positioning of a free motion carrier on the ground accurately, this paper introduces asplit-reuse three-dimensional (3D) LDV. For the error parameters during application, a Kalman filteringcalibration method with the assistance of a differential global positioning system (DGPS) is put forward in thispaper. Two groups of integrated navigation experiments are designed to validate the effectiveness of this methodand the universality of the obtained parameters. The experimental results show that the calibration methodproposed in this paper is effective and the 3D LDV after compensation can greatly improve the positioning accuracyof the integrated navigation. The maximum horizontal position errors of the two experiments calculated by thedead reckoning of the 3D LDV and the gyroscopes are 4.2m and 2.9m, and the maximum altitude errors are 0.8mand 0.9m respectively.

High cost-efficient and computationalgigapixel video camera based on commerciallenses and CMOS chips

Heng Mao, Jie He, Jiazhi Zhang, Yuanchao Bai, Muyue Zhai, Haiwen Li, Xiange Wen, Rui Chen, Huizhu Jia, Louis Tao, and Ming Jiang

Doc ID: 332351 Received 25 May 2018; Accepted 10 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: The state-of-the-art commercial telephoto lens has already provided us almost onegiga space-bandwidth product (SBP). Since the single image sensor cannot take suchsampling capacity, we implement a four-parallel-boresight imaging system by using four suchlenses, and use 64 image sensors to complete full field of view (FOV) imaging, for achieving0.8 gigapixel over 15.6°×10.5°. Multiple sensors mosaicking can make most on-linecomputation and data transfer in parallel, and help us to realize a gigapixel video camera.Meanwhile, according to the four-parallel-boresight configuration, the flat image planesimplifies the image registration and image stitching, and allows to keep high imagingperformances in full frame following the geometric and optical calibration and correction.Furthermore, considering that working distance changing does bring additional x/y offsetsbetween sensor arrays, we propose a computation based method and introduce 8-axisautomatic motion mechanism into the system to perform the on-line active displacement. Ourprototype camera using 16 sensors has been validated in the 50m indoor condition and 145moutdoor condition experiments, respectively. The effective angular resolution under the 0.2giga 24Hz video output is 18 μrad, which is two times of lens instantaneous FOV (iFOV).Comparing with other gigapixel cameras, it has the superiority in terms of the optical systemsimplicity and cost-efficiency. That would potentially benefit numerous unmanned aerialvehicle photogrammetric applications, pursuing high angular resolution over moderate FOV.

The Design of an Acousto-optic Tunable Filter Basing on Momentum Mismatching Together with the Rotatory Property

Chunguang Zhang, hao wang, zhenfei sheng, xiaofa zhang, jiangwei yuan, lei shi, and Pengchong Wang

Doc ID: 334067 Received 13 Jun 2018; Accepted 10 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: Basing on the momentum mismatching together with the crystal rotatory property, we investigated the diffraction performance of an acousto-optic tunable filter (AOTF). The relationship between diffraction efficiency, momentum mismatching, incident optical wave vector and ultrasound wave vector was analyzed. The correlation between the frequency tuning relation and the incident angle of light was demonstrated, which was usually ignored in the AOTF design. The diffracted wavelength could be decided by a particular acoustic frequency only when the incident angle of light was fixed. Theoretical and experimental analysis indicated that, we could realize to acquire the narrow-band spectrum and big angular aperture with a proper incident angle.

Various large-energy soliton operations withinan Er-doped fiber laser with Bismuth Selenideas saturable absorber

nannan xu, Huanian Zhang, and B Man

Doc ID: 340333 Received 20 Jul 2018; Accepted 10 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: Different large-energy mode-locked operations were successfully obtained within aBi2Se3 based Er-doped fiber laser. Firstly, mode-locked operation with a maximum pulseenergy of 17.2 nJ and a pulse width of 187 ns under a pulse repetition rate of 537.6 kHz wasobtained under the pump power of 680 mW. In addition, the characteristics of dark solitonsand soliton rains, which also exhibit large pulse energies, have been investigatedexperimentally. Our results fully proved that Bi2Se3 was an excellent candidate forinvestigating various mode-locked operations with large pulse energy due to its highnonlinear effect and high damage threshold.

Transformation optics based on unitary vectors and Fermat’s principle for arbitrary spatial transformation design

Pasit Jarutatsanangkoon, Waleed Mohammed, and Wanchai Pijitrojana

Doc ID: 331370 Received 04 Jun 2018; Accepted 09 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: A methodology of designing an arbitrary transformation using transformation optics (TO) based on unitary vectors and Fermat's principle is presented. The TO equation is derived in terms of grid coordinates. The geometry of the transformed space is stored in the grid coordinates rather than the transformation functions. This allows the crafting of an arbitrary transformation by combining several transformation templates together. The touch interface is employed to intuitively apply the transformations. The resulting material parameters are calculated from the proposed method and verified using the anisotropic finite-difference frequency-domain (AFDFD) method. Four examples are presented to demonstrate the capability of this method.

Polarization properties of reflected light withnatural light incidence and elimination ofangle of incidence ambiguity

xiaotian lu, Jie Yang, Weiqi Jin, Li Li, Xia Wang, and Su Qiu

Doc ID: 335709 Received 21 Jun 2018; Accepted 09 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: Polarization imaging technology provides information about not only theirradiance of a target but also the degree of polarization and angle of polarization, whichindicate extensive application potential in the field of ocean remote sensing. Natural light canbe converted into partially polarized light by the reflection from an interface, and the Fresnelequations can describe the quantitative relationship between the angle of incidence and thedegree of polarization of the reflected light. However, the relationship between the angle ofpolarization and angle of incidence has rarely been studied. In this study, we investigate thepolarization state model of reflected light and establish the relationship between the angle ofpolarization and angle of incidence. This is verified using polarization imaging experimentson a glass plate and calm water surface. The results indicate that the theoretical model agreeswell with the experimental results. A method to eliminate the ambiguity of the angle ofincidence is proposed based on the model and its effectiveness and feasibility are verified. Itlays the theoretical foundation for imaging detection based on the polarization imaging oftransparent media surfaces and sea surface ripples.

Effect of submount thickness on near-field bowing oflaser diode arrays

Hongyou Zhang, Tianqi Chen, Pu Zhang, Chung-En Zah, and Xingsheng Liu

Doc ID: 337721 Received 05 Jul 2018; Accepted 09 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: Near-field bowing a laser diode bar (i.e., the “SMILE” effect) degrades the laser beam brightness, adversely affectingoptical coupling and beam shaping. Due to the thermal induced stress during the bonding process, the emitters in alaser diode array (LDA) are vertically displaced, which causes the SMILE effect. The mismatch between thecoefficients of thermal expansion (CTE) of an LDA (GaAs with 6.4ppm/K) and a heat-sink (Cu with 16.4ppm/K) is alarge obstacle in the LDA bonding process, because it provokes thermal stress and large SMILE value, resulting inlarger divergence angle, and a wider line after focusing and collimation. In this letter, the changes in stress andstrain (SMILE value) and their effects on the laser bar as a function of the CuW submount thickness weretheoretically and experimentally studied. The finite element modeling (FEM) simulations and experimental resultsshow that the compression stress on the laser bar decreases with increasing CuW submount thickness because theCuW submount works as a buffer layer and can absorb stress. However, the laser bar out-of-plane strain (SMILEvalue) is approximately zero when the LDA is directly bonded onto the heat-sink without a submount; the SMILEvalue is maximized when the CuW submount thickness is increased to approximately one half or 44% of the heatsink.Beyond that, the SMILE value decreases with increasing CuW submount thickness.

Nonparaxial propagation of abruptly autofocusingcircular Pearcey Gaussian beams

Xingyu Chen, Dongmei Deng, Jingli Zhuang, Xiangbo Yang, Hongzhan Liu, and Guanghui Wang

Doc ID: 339875 Received 18 Jul 2018; Accepted 09 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: We introduce a new class of abruptly autofocusingcircular Pearcey Gaussian beams (AAFCPGBs) whichtend to abruptly autofocusing circular Pearcey beamswith a small distribution factor, or Gaussian beamswith a larger distribution factor. The nonparaxial propagationof the AAFCPGBs is investigated by numericalcalculation. The radiation force of the AAFCPGBs exertedon a Rayleigh particle is analyzed in detail.

Graphene Based Metasurface for Tunable Broadband Terahertz Cross Polarization Converter over Wide Angle of Incidence

Vinit Singh Yadav, Sambit Kumar Ghosh, Somak Bhattacharyya, and Santanu Das

Doc ID: 331919 Received 16 May 2018; Accepted 09 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: In this report, using graphene-based metasurface, we demonstrate a unique design to develop a highly efficient, broadband, mid-infrared cross polarization converter. The proposed graphene–based metasurface structure comprises of periodical ϕ-shaped graphene on the top surface of a noble-metal backed dielectric silicon dioxide (SiO2). The reported structure converts the incident linearly polarized wave into cross-polarized components with peak polarization conversion ratio (PCR) of more than 0.9 over a large band. Furthermore, the metasurface structure exhibits the fullwidth at half maximum (FWHM) bandwidth of 41.98% with respect to its center frequency of 5.98 THz. The physical insights behind electromagnetic polarization conversion are supported by field distributions and retrieved electromagnetic parameters. The structure works as broadband cross polarization converter up to 40º incident angle for both TE and TM polarizations. In addition, the structure is found to be as thin as ~λ/6 with respect to lowermost frequency of the polarization conversion. The period of the unit cell is ~λ/24 to support the fact that the structure can be treated as metasurface.

Optical interconnects based on high-contrast alldielectricnano-post arrays

Shulang Lin, Huarong Gu, and Cardinal Warde

Doc ID: 334593 Received 07 Jun 2018; Accepted 08 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: In this paper, we present a compact solution for optical interconnects in optoelectronic integrated neural networksusing high-contrast all-dielectric nano-post arrays. The nano-post arrays are made of amorphous silicon which hasa high refractive index and high transmittance in the near infrared. The radius of each post is changed to generatedifferent phase delay. Deflection and convergence of the light are realized by proper design of the phase profile ofthe nano-post array. The connection efficiencies are calculated by numerical simulations and compared with thoseof zone plate interconnects. Simulation results show that the proposed nano-post arrays can have superiorperformance over zone plates in applications which require short focal length and high efficiency.

Angular Resolved Power Spectral Density Analysis for Improving Mirror Manufacturing

Tom Pertermann, Johannes Hartung, Matthias Beier, Marcus Trost, Sven Schröder, Stefan Risse, Ramona Eberhardt, Andreas Tünnermann, and Herbert Gross

Doc ID: 338180 Received 10 Jul 2018; Accepted 08 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: Ultra-precise diamond turning is the means of choice for manufacturing optical freeforms. Analyzing surface errors in different spatial frequency ranges has mainly been performed in a one-dimensional representation of the power spectral density function. However, the advanced machine dynamics at the fabrication of freeform mirrors result in highly anisotropic surfaces with regular ripples in different orientations. To properly analyze the entire surface in the frequency regime, a new way of representing the two-dimensional power spectral density is introduced in this article. This novel tool is utilized for the evaluation of an exemplaric freeform mirror.

An analytical procedure to assess theperformance characteristics of a nonspectroscopicinfrared optical sensor fordiscrimination of chemical vapors

Kevin Major, Menelaos Poutous, Ishwar Aggarwal, Jasbinder Sanghera, and Ken Ewing

Doc ID: 335006 Received 12 Jun 2018; Accepted 08 Sep 2018; Posted 19 Sep 2018  View: PDF

Abstract: An optical-filter based sensor that was designed to mimic human color vision wasrecently developed. This sensor uses three mid-infrared optical filters to discriminate betweenchemicals with similar, strongly overlapping mid-infrared absorption bands. This nonspectroscopictechnique requires no spectral scanning. This paper defines the selectivity andspecificity of this biomimetic sensor. Receiver operating characteristic (ROC) curves arepresented for each target chemical. These results demonstrate that the sensor is highlyselective and can provide discrimination with no false positives for three similar targetchemicals, acetone, hexane, and fuel oil, while rejecting potential interferents.

Ultralong photonic nanojet formed by dielectricmicrotoroid structure

Baifu Zhang, Jingjing Hao, Zhe Shen, Heng Wu, Kang Zhu, Ji Xu, and Jianping Ding

Doc ID: 339870 Received 16 Jul 2018; Accepted 07 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: Photonic nanojet (PNJ) is a highly confined light beam formed by a transparent particle under a light wave illumination. Here we propose and numerically investigate the PNJ formed by a dielectric circular toroid with micro dimensions and homogenous refractive index. Three-dimensional finite-difference time-domain (FDTD) simulations are conducted and demonstrate that ultralong PNJ can be formed by the doughnut-like structure. Besides, microtoroid structure can allow high-index material (n=3.5) for PNJ generation. Various PNJ properties, including the focal distance, PNJ length, full width at half-maximum (FWHM) and maximum intensity, can be flexibly tuned by modifying the geometry of the proposed structure.

Sensitivity improvement by optimized opticalswitching and curve fitting in a cavity ringdownspectrometer

Weipeng Zhang, Haoyun Wei, Xinyi Chen, and Yan Li

Doc ID: 340443 Received 23 Jul 2018; Accepted 07 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: We presented methods for the improvement of the sensitivity of a cavity ringdownspectrometer other than modifying the cavity length and the mirrors. As for the lightswitching, a fast driving scheme was proposed to address the slow switching speed of theboost optical amplifier which makes it have only half of the switching time than the commonacoustic-optical modulators and electro-optical modulators as well as higher extinction ratios.This effectively suppressed the distortions of the ring-down signals. We further adopted arealistic non-exponential curve-fitting method, taking into account the switching speed andthe delayed triggering of the optical switch. These methods help accurately determine thering-down time constants, which in turn reduced the Allan variance of the measurementresults and increased the sensitivity. We performed tests at different repetition rates and all ofthem revealed more than 30 % sensitivity improvement. At a rate of 16 kHz, we increased theminimal detectable absorption of 9.1×10-11 cm-1 to 5.7×10-11 cm-1. The effectiveness of theseupgrades could benefit many spectroscopic applications of the cavity ring-downspectroscopy, especially for the frontier researches that require sensitive measurement andhigh-quality spectral data.

LIBS assisted chemometric methods for ricegeographic origin classification

Ping Yang, Ran Zhou, Zhang Wen, Shisong Tang, Zhong Qi Hao, Xiangyou LI, Yongfeng Lu, and Xiaoyan Zeng

Doc ID: 340213 Received 19 Jul 2018; Accepted 07 Sep 2018; Posted 07 Sep 2018  View: PDF

Abstract: The problems of adulteration and mislabelling are very common in food industry. Laser-induced breakdownspectroscopy (LIBS) coupled with chemometric methods has many intrinsic advantages on adulteration analysis ofvarious materials. In this work, several chemometric algorithms, i.e., principal component analysis (PCA), decisiontree (DT), random forest (RF), partial least squares discriminant analysis (PLS-DA), linear discriminant analysis(LDA) and support vector machine (SVM), were carried out assisted with LIBS technology to study the classificationperformances on rice geographic origins. A series of samples including 20 kinds of rice samples from differentgeographic origins were detected using LIBS with no any pretreatment processes. For data analysis, PCA wasemployed to reduce the input variables, and to reduce the collinearity of LIBS spectral results as well. The resultsshowed the classification accuracies of the mentioned chemometric algorithms of DT, RF, PLS-DA, LDA, and SVMwith 89 input variables were 86.80%, 96.30%, 96.80%, 98.60% and 99.20%, respectively. At the same time, theoperation time of these algorithms were 3.81, 54.64, 3.63, 2.09, and 531.01 s, respectively. On the other hand, 30principal components of input variables were also tested under the same conditions. The classification accuraciesfor the above algorithms were 81.60%, 98.00%, 95.70%, 98.40%, and 99.20%, respectively. The operation timewere 2.01, 4.88, 3.67, 0.36, and 308.55 s, respectively. In addition, the 5-fold cross-validation classificationaccuracies with 30 input variables for DT, RF, PLS-DA, LDA, and SVM were 83.75%, 97.95%, 94.75%, 98.35%, and99.25%, respectively. As a result, LDA was demonstrated to be the best and most efficient tool for rice geographicorigin classification assisted with LIBS with high accuracy and analytical speed, which has a great potential forrapid identification of adulterate products in agriculture without use of any chemical reagent.

Trade Study of Aperture Size, Adaptive Optics andMultiple Spatial Modes for a Polarization EntanglementQKD System over a 30 km Maritime Channel

John Gariano and Ivan Djordjevic

Doc ID: 340299 Received 20 Jul 2018; Accepted 07 Sep 2018; Posted 07 Sep 2018  View: PDF

Abstract: Transmitting a beam through the atmosphere over long distances can be a challenging problem. Factorsfrom the channel, such as atmospheric turbulence causing beam wander and distortions to the wavefront,or the optical design can change the loss induced in the channel. This work simulates a quantum keydistribution system implementing the BB84 protocol with entangled photons operating over a 30 kmmaritime channel using one, four, and nine spatial modes. For the cases of multiple spatial modes, atmosphericturbulence increases the channel cross talk, resulting in an increase in the noise for each channel.To compensate for distortions in the wavefront, adaptive optics at the transmitter or receiver are used topre- or post-correct the wavefront.

Design of uniformly collimating LED lens of multiplefreeform and Fresnel surfaces with different intersurfacemapping orders

Hui Xiong, zhang jian, jia gao, and Haobo Lin

Doc ID: 328035 Received 12 Apr 2018; Accepted 07 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: In this work, we propose a design method of composite freeform collimating lenses, which integrates freeform reflection,refraction and Fresnel surfaces to realize highly collimated and uniformed light output in a single lens element. Thealgorithm is designed in considerations for consistent combination of different surfaces, so the light rays reaching theFresnel surface through refraction and reflection should generate the same luminous intensity. The Fresnel rings can bedesigned in two different ways, depending on the sequence of light rays propagating between the reflection and the Fresnelsurfaces. The lighting effects of the lenses are analyzed in 3-dimension simulation, and the light output of both schemesreaches a high level of collimation and uniformity, agreeing well with design expectations. The obtained lenses have theadvantages of compact volume, high light extraction efficiency, and variable geometry via changing the combination form ofthe freeform surfaces.

Parallel superposition of phase holograms for multiple parameters identification

Mona Mihailescu and Eugen Scarlat

Doc ID: 332596 Received 30 May 2018; Accepted 07 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: A method to identify the azimuthal index of vortices and radial parameter of axicons as well as their associated spatial frequencies is presented. These constructive parameters are employed to design parallel superimposed computer generated holograms (PSCGH). The diffraction patterns are studied in correspondence with the constructive parameters of the PSCGH. Another diffractive structure serving as identification key (IK) is inserted in the whole beam emerging from the PSCGH. The method identifies the parameters set in first and second diffraction orders. The robustness and the sensitivity of the method were checked against parameters mismatches. It can be exploited as authentication tool for holographic stamps incorporating PSCGHs.

Highly Sensitive Electro-optic Probe Incorporating anUltra-high Q-factor LiNbO3 Etalon

Woo-Bin Lee, Seon-U Baek, and Sang-Shin Lee

Doc ID: 334940 Received 12 Jun 2018; Accepted 07 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: A highly sensitive electro-optic (EO) probe has been proposed and realized by tethering an ultra-high quality (Q-)factor LiNbO3 etalon to a single-mode fiber operating at around a 1550-nm wavelength. For the adopted EO etalon,the electric field-induced refractive index modification is deemed to shift its own spectral response. An electricalmodulation signal is anticipated to be produced when a probe light beam with a fixed bias wavelength is impingingupon the EO etalon. The EO etalon is particularly required to exhibit a remarkably steep spectral response and thusfacilitate the modulation efficiency. In aiming to scrutinize the performance in terms of sensitivity, two EO probesinvolving profoundly different Q-factors were prepared and applied to detect the electric field emitted from amicrostrip device. It was confirmed that the sensitivity could be efficiently enhanced by as much as 28 dB byboosting the Q-factor 18 times when a probe light beam operating at = ~1550 nm is properly collimated andpolarized. Accordingly, the minimum detectable signal was successfully diminished.

Integrated all-optical wavelength and polarization conversion of orbital angular momentum carrying modes

S. Faezeh Mousavi and Rahman Nouroozi

Doc ID: 335501 Received 18 Jun 2018; Accepted 07 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: Wavelength Division Multiplexing (WDM) technique using higher order spatial modes such as OrbitalAngular Momentum (OAM) through a channelized bandwidth provides enhanced capacity communicationsystems. All-optical wavelength converter is a key function in implemented WDM networks toovercome the wavelength contentions. In addition, polarization converter provides efficient control onthe state of polarization for encoded data channels in the optical networks. This paper proposes a novelversatile-designed integrated optical device with Ycut ridge Lithium Niobate (LN) photonic wire configurationwhich acts as wavelength or polarization converter for data modulated on OAM. It is schemedin such a way that generates decomposed guided modes with new wavelength and polarization viacSHG/DFG and type-II DFG nonlinear interactions, respectively, where their desired relative phase isachieved by linear electro-optical effect in the successive phase shifter part. The low-loss (6 0.09 dB/cm),high-purity (> 94%), and low-voltage (6 4 V) of the high-speed proposed modulator enables its compatibleoperation in commercial wireless and fiber based polarization-multiplexed WDM communicationsystems.

Intensity enhancement in Off-Axis Integrated CavityOutput spectroscopy

Faisal Nadeem, Julien Mandon, Simona Cristescu, and Frans J. Harren

Doc ID: 336439 Received 28 Jun 2018; Accepted 07 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: In the field of laser-based absorption spectroscopy, off-axis integrated cavity output spectroscopy is considered to be a sensitiveand robust method, employing a simple optical design. However, one of the major drawbacks of non-mode-matched cavitiescombined with highly reflective mirrors (> 99.98%) is its low output intensity. Here, we systematically investigate the increase incavity output intensity, using a third, re-injection mirror before the absorption cavity. The presented design not only enables hightransmission power but also retains a long effective path length. To investigate the intensity enhancement, we used a CO2absorption line in the near infrared wavelength region at 6240.10 cm-1. In agreement with our simulation model, we achieved anintensity enhancement factor of 38. We achieved a noise equivalent absorption sensitivity to 1.6 ×10-8 cm-1 Hz-1/2 which is nolonger limited by the detectivity of the detector.

Real-time layer-based Computer-Generated Hologram calculation for the Fourier Transform Optical System

Antonin Gilles and Patrick Gioia

Doc ID: 341178 Received 31 Jul 2018; Accepted 06 Sep 2018; Posted 07 Sep 2018  View: PDF

Abstract: With the growing interest for Augmented Reality devices, holography is often considered as a promising technology to overcome the focus issues of conventional stereoscopic displays. To enlarge the field-of-view of holographic Head-Mounted Displays, a Fourier Transform Optical System (FTOS) has been proposed. However, since the scene geometry is distorted by the FTOS, it is necessary to compensate the position of each scene point during the hologram computation, resulting in long calculation times. In this paper, we propose a real-time Computer-Generated Hologram (CGH) calculation method for the FTOS. Whereas previously proposed methods used a ray-tracing approach to compensate the distortion induced by the FTOS, our proposed method relies on a layer-based approach. Experimental results show that our method is able to compute holograms of resolution (3840 x 2160) in real-time at 24 frames per second, enabling its use in Augmented Reality applications.

Study on the backscattering disturbance in duplex underwater wireless optical communication system

Biao Han, Wei Zhao, Jiaocheng Meng, Yunqiang Zheng, and Qian Yang

Doc ID: 335257 Received 15 Jun 2018; Accepted 06 Sep 2018; Posted 07 Sep 2018  View: PDF

Abstract: Backscattering affects the performance of receiver in duplex underwater wireless optical communication (UWOC) system. In this paper, firstly we establish a theoretical model to study the backscattering disturbance based on Monte Carlo method. Then, we investigate this issue with different divergence angles of transmitter, field angles of receiver, and separated distances between transmitter and receiver in each terminal. The results show that, at receiver, with the increase of divergence angle, backscattering light power reduces a little, communication signal attenuates dramatically, and optical signal-to-noise ratio (OSNR) reduces tremendously. With the increase of field angle, backscattering light power increases, communication signal nearly has no change, and OSNR reduces. With the increase of the separated distance, backscattering light power is reduced, communication signal has no change, and OSNR increases. In order to reduce the impact of backscattering disturbance, transmitter and receiver in each terminal should be separated with a longer distance, and field angle of receiver should be smaller. If the transmitting optical power or receiving sensitivity is too high in duplex UWOC, backscattering might be difficult to suppress effectively. Then system should work in half-duplex mode. These results are useful to duplex UWOC system design.

Enhanced and broadened fluorescence of ZnSe quantum dotsenabled by the fluorescence energy transfer system of ZnSe quantumdots and the gold nanoparticles

Bai zhongchen, man Peng, Zhengping Zhang, and Shuijie Qin

Doc ID: 337747 Received 02 Jul 2018; Accepted 06 Sep 2018; Posted 07 Sep 2018  View: PDF

Abstract: The Enhanced and broadened fluorescence of ZnSe quantum dots (QDs) were studiedby using a fluorescence energy transfer system (FETS) of ZnSe QDs and the gold nanoparticles(NPs). The FETS was prepared via dispersing uniformly the gold nanoparticles into ZnSe QDssolution in the condition of magnetic stirring. The enhanced and broadened fluorescence wasobserved on the film of FETS due to the transfer of photo-generated carries between ZnSe QDsand the gold NPs, instead of the surface plasma resonance effect. The excitonic and enhancedfluorescence on the FETS film depended on the competition of electron-hole recombination andelectron transfer from ZnSe QDs to the gold NPs. In addition, because of the excitonicfluorescence of ZnSe QDs absorbed by the gold NPs, the electrons of s-p band of gold NPs werefurther increased to facilitate its energy level shift toward the conduction band of ZnSe QDs forresulting in the blue-shift of enhanced fluorescence. This enhanced and broadened fluorescencemethod can be applied for controlling fluorescence in photoelectric detection, photodiode,lightshow and sensor devices.

Experimental ray-tracing with point diffraction interferometry and its application in focal length measurement

Lingfeng Chen, Xiaojie Meng, He Xiao, Lei Yu, and Yufei Xue

Doc ID: 338265 Received 10 Jul 2018; Accepted 06 Sep 2018; Posted 07 Sep 2018  View: PDF

Abstract: A novel method that could experimentally trace the ray propagation of an optical system based on point diffraction interferometry (PDI) is presented. The ray represented by the line connecting two point light sources (PLS) intersects with two parallel photographic planes, which are separated at a distinct distance. The intersections locate at which the optical path differences (OPD) to the two PLSs reach its maximum, thus can be derived from the interferograms on the photographic planes. The ray is positioned by connecting the two intersections. Using fibers as the PLSs and CCD arrays as the photographic planes, we demonstrate its principle and its application in focal length measurement through experiments.

Error Characteristic Analysis and Experimental Research on a Fiber Optic Current Transformer

yansong li, Xinying Liu, Weiwei Zhang, and Jun Liu

Doc ID: 338494 Received 10 Jul 2018; Accepted 06 Sep 2018; Posted 07 Sep 2018  View: PDF

Abstract: To solve the operation precision problem of a fiber optic current transformer (FOCT), we have established models of the polarization error based on the Jones matrix and a model of the temperature drift error considering the bending characteristics. The polarization study shows that the greater extinction ratio of polarization devices and a smaller polarization direction deviation will lead to less output error. The temperature analysis suggests that greater intrinsic linear birefringence, a smaller bending radius, and more winding turns of the sensing fiber should exacerbate temperature drift. Furthermore, the experimental results verify the effectiveness of the theoretical expressions.

Rapid identification of Huanlongbing-infected citrusplants using laser-induced breakdown spectroscopy ofphloem samples

Luis Ponce, Ed Etxeberria, Pedro Gonzalez Blanco, Alejandro Ponce Flores, and TERESA FLORES

Doc ID: 330296 Received 25 Apr 2018; Accepted 05 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: Huanglongbing (HLB) is the most destructive disease of citrus worldwide. The disease is caused by the protobacteriaCantidatus Liberibacter asiaticus and transmitted by the Asian citrus psyllid Diaphorina citri. HLBsymptoms are slow to appear while the tree continues to be a source of inoculum. Monitoring tree health and rapiddetection of HLB is critical for sustainable citrus production. Nowadays, scientists are working on developing newtechniques pre-symptomatic detection of HLB, as there is no available method for real-time assessment of treehealth. In this study we demonstrate the rapid and efficient discrimination between healthy and HLB-affected ofcitrus by laser-induced breakdown spectroscopy (LIBS) combined with chemometric analysis. Healthy and HLBaffectedtrees were differentiated with high degree of precision. The novelty of this method lies in thefingerprinting of healthy and diseased plants based on their organic and inorganic constituents, and the use of amulti-pulse laser coupled with a microscope to take spectra of the plant phloem.

Optical modeling of the emission zone profile andoptimal emitter position based on the internal fieldprofile of the air mode in organic light-emitting diodes

Jiyong Kim, Kyoung-Youm Kim, and Jung Ho Kim

Doc ID: 330371 Received 27 Apr 2018; Accepted 05 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: We propose a theoretical formulation to calculate the internal profile of the air mode in the organic light-emittingdiode (OLED) on the combination of the transfer matrix method and source-term method. The spatial distributionsof the air mode are calculated in a top-emitting OLED with respect to the light polarization, extraction angle, dipoleorientation, and dipole position. Air modes are also calculated on the basis of the previously-used external sourcemodel, where the input optical wave is injected from the air into the OLED multilayer. Comparison of the calculatedair modes between two models checks the validity of the external source model. In addition, we propose animproved formula to determine the optimal emitter positions that maximize the two-beam interference of themicro-cavity effect. In the improved formula, a non-ideal reflection phase shift at a reflective metal anode is treatedas the skin depth of the air mode. Finally, the effect of the dipole orientation on the air mode is investigated.Compared with the air mode emitted by the horizontally-oriented dipole, the air mode generated by the verticallyorienteddipole has relatively small intensity and shows the opposite dependence of the emitter position variation.The calculation results of the internal profile of the air mode within the emission layer are matched with the profileof the emission zone obtained by output radiant flux on the basis of the currently-used point dipole model.

Theoretical study of multilayer coatings reflectiontaking into account third order optical nonlinearities

Steffen Wilbrandt and Olaf Stenzel

Doc ID: 335719 Received 21 Jun 2018; Accepted 05 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: A theoretical approach is presented that allows calculating the reflectance of dielectric multilayer coatings takingthird order optical nonlinearities into account. The description is based on the third-order optical susceptibility, sothat nonlinear refraction as well as two-photon absorption processes are automatically considered in terms of thereal and imaginary parts of the susceptibility. Two model systems are calculated in order to demonstrate thephysical validity of the approach: a mirror that is optimized for maximum reflectance at a given wavelength and agiven incident intensity, and a mirror that provides a rather flat dependence of the reflected intensity on theincident one. Model calculations are performed for the laser wavelength values of 1064nm, 800nm, and 532nm.

Direct binary search for improved coherent beamshaping and optical differentiation wavefront sensing

Christophe Dorrer and Jie Qiao

Doc ID: 335783 Received 21 Jun 2018; Accepted 05 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: Spatially dithered distributions of binary amplitude pixels are optimized using a full direct binary search takinginto account the experimental configuration for amplitude modulation of coherent waves. This design process isshown to yield a significant reduction of the noise induced by binarization and pixelation over the region ofinterest. We demonstrate this approach for beam shaping and optical differentiation wavefront sensing, where theregion of interest is in an image plane of the pixel distribution and in the far field of the pixel distribution,respectively. The observed reduction in error compared to a standard error diffusion algorithm is significant forboth applications because it improves performance without the tighter fabrication tolerance and cost associatedwith smaller pixels.

Multiscale modeling of fiber optical gyroscopetemperature drift based on improved EEMD

Wei Wang and xiyuan chen

Doc ID: 337828 Received 04 Jul 2018; Accepted 05 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: Temperature drift is a major error source of Fiber Optical Gyroscope (FOG), and the method of modeling is animportant method to eliminate it. A method of multiscale modeling based on improved Ensemble Empirical ModeDecomposition (EEMD) is proposed in this paper. First, in order to improve the ability of eliminating the modemixing, the influence of frequency of masking signal on the mode mixing is analyzed. Then we get a conclusion thatthe frequency of masking signal should be higher than that of the signal, and an improved EEMD (IEEMD) isproposed based on the conclusion. Second, the temperature drift of FOG is filtered by applying the permutationentropy to the Intrinsic Mode Functions (IMF). Third, the IMFs are divided into several scales according to the meanvalue and the distribution of instantaneous frequency of IMFs. Finally, the algorithm of Support Vector Machine(SVM) is used to model each scale, and the models are accumulated into a total model. The regression error aftercompensation of proposed method (in the case of MSE indicator) increased by more than two orders of magnitudecompared to the original temperature drift.

A microwave photonic approach for simultaneous interrogation of multiple fiber Bragg grating temperature sensors

Maria Iulia Comanici, Jingjing Hu, Parisa Moslemi, and Lawrence Chen

Doc ID: 341563 Received 03 Aug 2018; Accepted 05 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: We demonstrate a microwave photonic (MWP) approach for interrogating multiple linearly chirped fiber Bragg grating (LCFBG) temperature sensors. The MWP interrogation system is based on an arrayed waveguide grating Sagnac interferometer incorporating multiple LCFBG sensors that is used to generate multiple chirped microwave waveforms whose characteristics are uniquely related to those of the LCFBGs. Compressing the generated microwave signals allows monitoring simultaneously and independently the shifts associated with applying temperature changes to each LCFBG in real-time.

Study on extended depth of field for planar flow cytometric microimaging system

hongfeng qu, Shoufeng Tong, and Baoxue Bo

Doc ID: 342250 Received 13 Aug 2018; Accepted 05 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: The planar flow cytometric microimaging system is mainly used for cell recognition and classification in urinary sediment and gynecological secretion analysis. The depth of field of the microscope seriously restricts the imaging range of the microscope in the direction of the optical axis, so that it can't image all the cells in the whole laminar thickness of the planar flow cytometric microimaging system. In this paper, the depth of field (DOF) is extended by the way of dual sensors common light path, and the large DOF imaging of high-speed moving cells is realized, which solves the difficulty that the multi focus super depth technique can only be used in static observation sample. The fusion algorithm based on saliency detection and multi-scale image decomposition is developed to fuse the two-depth-of-field images. The multi-scale image decomposition uses L0 smoothing for multi-scale image decomposition. L0 smoothing is particularly effective for sharpening major edges by increasing the steepness of transition while eliminating a manageable degree of low-amplitude structures. It can globally control how many non-zero gradients are resulted in to approximate prominent structure in a sparsity-control manner, which does not depend on local features, but instead globally locates important edges. Experimental results show that our approach can enlarge the depth of field by 1.89 times, and the dual depth-of-field fusion algorithm can fuse two images with different depth of field into one image with clear multiple targets.

Optimization of Spatial Light Modulator driven by Digital Video Interface Graphics to generate Holographic Optical Traps

Deepak Gupta, B V R Tata, and T R Ravindran

Doc ID: 331587 Received 14 May 2018; Accepted 04 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: We propose a method to optimize spatial light modulators driven by digital video interface (DVI) graphics in a holographic optical tweezers (HOTs) system. A method analogous to that used to optimize LCD televisions is used to optimize the properties of the graphics card through a diffraction based experiment and develop a look-up table for the SLM. The optimization allows the SLM to function with its full phase modulation depth with improved diffraction efficiency. Further, we propose a simple and robust method to correct for the spatially varying phase response of the SLM to enhance its diffraction efficiency. The optimization results in an improvement of uniformity in the intensity of the trap spots.

Passively Q-switched Yb-doped dual-wavelength fiberlaser based on gold nanocages saturable absorber

Qiongyu Hu, Ping Li, Baitao Zhang, Binghai Liu, Lili Wang, and Xiaohan Chen

Doc ID: 332300 Received 17 Jul 2018; Accepted 04 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: In this letter, we demonstrate a passively Q-switched Yb-doped dual-wavelength fiber laser using GNCs (goldnanocages) as saturable absorber. The GNCs are prepared by the seed-mediated method with the modulationdepth of 5.3% and saturable intensity of 0.16 MW/cm2. A simultaneous dual-wavelength operation is achieved at1059.9 and 1060.5 nm with 3 dB bandwidth of 0.05 and 0.04 nm, respectively. A maximum average output power of6.03 mW with minimum pulse width of 2.06 μs and maximum repetition rate of 134.9 kHz is obtained at a pumppower of 385 mW, corresponding to the optical-to-optical conversion efficiency of 1.57% and the slope efficiency of2.75%.

Optical properties of a Cr/4H-SiC photodetector in the spectral range from UV to EUV

Alexander Gottwald, Udo Kroth, Evgenia Kalinina, and Vladimir Zabrodskii

Doc ID: 338472 Received 10 Jul 2018; Accepted 04 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: This work examines the electrical and radiometric characteristics of a photodiode based on a 4H-SiC semiconductor material with a semitransparent Cr Schottky barrier of about 7 nm thickness. The device had a photosensitive area of 10 mm in diameter. In the spectral range from 40 nm to 400 nm, the photodiode showed a maximum quantum efficiency of 50 % at 253 nm with a relative uniformity of 4 % in the photosensitivity over its surface. The linearity of the photoresponse was measured at wavelengths of 70 nm and 265 nm for incident radiant powers from 2 nW to 800 nW, and no significant deviation from linearity was found. Regarding its electrical characteristics, the photodiode showed less than 10-13 A dark current at a reverse voltage of 10 V.

Quantum efficiency measurement of an x-ray CCD by means of an x-ray generator monochromatized over the 0.1-1.5 keV spectral region

Sébastien Hubert and Franck Boubault

Doc ID: 338675 Received 13 Jul 2018; Accepted 04 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: Abstract: The CEA-CESTA has been developing an x-ray calibration laboratory for several years close to the Laser MégaJoule’s Facility to mainly calibrate x-ray cameras. Based on x-ray generators, a great effort is carrying out to get x-ray monochromatic sources over the 0.1-10 keV spectral range. Moreover, their routine availability is a prerequisite while getting reduced uncertainties. To achieve this purpose, two x-ray monochromators have been recently developed, the former running below 1.5 keV the latter in the hard x-ray region. The work presented in this paper constitutes the first radiometric calibration of an x-ray camera in the soft x-ray region, namely a charge-coupled-device (CCD). The CCD is thinned and back illuminated with a 1300  1340 format and 20 µm  20 µm pixels. It has been calibrated by means of our soft x-ray monochromator based on a Rowland circle geometry. This apparatus is able to take on board simultaneously two detectors under vacuum: the CDD to be calibrated and a silicon drift spectrometer (SDD) which acts as a reference detector to get the x-ray monochromatic intensity. An internal specific vacuum manipulator allows putting successively each detector in front of the scanning exit slit. Quantum efficiency (QE) of the CCD has thus been measured over the 0.1-1.2 keV region thanks to the reference SDD. This latter was previously calibrated on the same monochromator by cross-calibration with an other SDD calibrated at the PTB. QE measurements are then compared to the CCD manufacturer’s model and with previous ones performed on the same camera by means of our hard x-ray monochromator (2-10 keV). Comparison of these results with a farther PTB’s efficiency calibration of the reference SDD used to calibrate the CCD is discussed and allows concluding definitively about the validity of measurements performed by our x-ray monochromators.

A highly sensitive dual-core photonic crystal fiber based onsurface plasmon resonance sensor with silver nano continuousgrating

Jiao Shengxi, Sanfeng Gu, Han-Rui Yang, Hairui fang, and Shibo Xu

Doc ID: 340510 Received 23 Jul 2018; Accepted 04 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: Two kinds of photonic crystal fiber (PCF) sensors based on surface plasmon resonance (SPR) with silver nano continuousgrating (i) and (ii) are designed. The coupling characteristics and sensing properties are analyzed numerically byfinite element method (FEM). The results show that the proposed sensor based on silver nano continuous grating (i)can achieve better performance than that of the sensors based on silver nano continuous grating (ii) and plane silverfilm structures. When the segmented number is 50 and segmented angle is 0.5°, a wavelength sensitivity of theproposed sensor with silver nano continuous grating (i) is obtained as high as 13600 nm/RIU in the refractive index(RI) range from 1.330 to 1.365, corresponding to a maximum RI resolution of 7.35×10-6 RIU, which can have promisingapplications in medical, environmental monitoring and biochemical detection.

Vision Solution for an Assisted Puncture Robotics System Postioning

Guanwu Jiang, Minzhou Luo, Lijuan Lu, Keqiang Bai, Saixuan Chen, and Omar Abdelaziz

Doc ID: 334094 Received 04 Jun 2018; Accepted 04 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: Medical robotics and computer-assisted surgery are hotspots in the field of robotics and medicine, changing the essence of traditional surgery using a combination of robotic, image processing, and computer technologies. The present paper aimed to study the auxiliary puncture procedure using a robot based on binocular vision optical positioning technology that can be used in minimally invasive surgery for skin marker coordinate precision. ZED binocular cameras were selected for image acquisition and a model was established based on Zhang’s calibration. Moreover, a Hough Circle detection algorithm was proposed for binocular stereo image feature extraction to obtain the marker points in three-dimensional space coordinates. Accurate marker coordinate information for a human 3D bone model was obtained, laying the foundation for further research regarding robot-assisted precise positioning technology for use in puncture surgery.

Plasmonic topological edge states in ring-structure gate graphene

Zidong Song, Hongjun Liu, Nan Huang, and Zhaolu Wang

Doc ID: 335664 Received 02 Jul 2018; Accepted 04 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: Topological photonic states exhibit unique robustness against defects, facilitating fault-tolerant photonic device applications. However, existing proposals either involve sophisticated and bulky structure or can only operate in the microwave regime. We show a theoretical demonstration for highly confined topologically protected plasmonic states to be realized at infrared frequencies in monolayer graphene with ring-structure gate. With a suitable bias voltage, the combined gate-graphene structure is shown to produce sufficiently strong Bragg scattering of graphene surface plasmons and to impart it with nontrivial topological properties. Our design is compact and could pave the way for dynamically reconfigurable, robust, nanoscale, integrated photonic devices.

Properties of dynamic image displacements based onmicrostructure

Peng Huang, Chuanwang He, fan bin, and xiaochun dong

Doc ID: 338311 Received 10 Jul 2018; Accepted 03 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: The superposition structure of dynamic moiré images contains a layer of micropattern array and a correspondinglayer of microlens array. Dynamic moiré images can be observed without special eyeglasses and will shift with theviewing angle varying. In this work, it is described as a presentation of a variety of the moiré. We chiefly investigatethe motion effects of dynamic moiré images. Analytical models to describe the structures and methods to evaluatethe displacement of dynamic moiré images are proposed. Experiments are conducted to validate the formula of thedisplacement. The results of this study are helpful to design dynamic moiré images, which can be applied forpotential applications in anti-counterfeiting films, packaging and authentication.

High power picosecond parametric mid-IR source tunable between 1.7 and 2.6 µm

Michal Vyvlecka, Ondrej Novak, Martin Smrz, and Tomas Mocek

Doc ID: 338354 Received 10 Jul 2018; Accepted 03 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: High average power wavelength tunable picosecond mid-IR source based on parametric down-conversion has been developed. The conversion system consists of two stages, optical parametric generator (OPG) and optical parametric amplifier (OPA), which are pumped by an Yb:YAG thin-disk laser operated at 77 kHz repetition rate, 1030 nm wavelength, and pulse width down to 1.3 ps. The signal beam is amplified up to 9 W and the idler up to 5 W at OPA pumping of 43 W. Tunability between 1.70 - 1.95 μm for signal and between 2.2 - 2.6 μm for idler has been achieved. The system is rather simple and power scalable.

Determination of Pb in soils by double pulse laser-induced breakdown spectroscopy assisted by continuum wave-diode laser induced fluorescence

Gustavo Nicolodelli, Paulino Villas-Boas, Carlos Menegatti, Giorgio Senesi, Daniel Magalhaes, Daniele Souza, Debora Milori, and Bruno Marangoni

Doc ID: 330962 Received 08 May 2018; Accepted 03 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: Laser-induced breakdown spectroscopy (LIBS) has attracted a lot of attention due to its potential to rapidly identify and quantify any chemical element with minimal sample preparation, but, despite continuous improvements, the sensitivity of this technique still remains a challenge. In order to increase LIBS intensity a laser induced fluorescence (LIF) system can be coupled with LIBS to re-excite a transition of the element in the plasma by employing very expensive Optical Parametric Oscillators (OPO). In this work, a homemade tunable continuum wave-diode laser (CW-DL) has been developed and coupled to a double pulse (DP) LIBS system to enhance the sensitivity of Pb detection in a soil sample at the transition 6s26p2-3P2 ⟶ 6s26p7s-3P1, 405.78 nm. Before sample analysis, the production of no scattered light by the plasma was ascertained, and the optimal temperature of 10000 K was measured for this transition, which was feasible to be achieved in DP-LIBS systems. An increase of approximately 100% for the Pb I transition at 405.58 nm was obtained by DPLIBS-CWDL-LIF with respect to the DPLIBS system alone. This result opens a new promising line of research to improve LIBS sensitivity using the CW-DL approach.

Optofluidic Variable Optical AttenuatorControlled by Electricity

Jing Wan, Fenglan Xue, Chengjie Liu, Shaoqiang Huang, Shuzheng Fan, and Fangren Hu

Doc ID: 337630 Received 19 Jul 2018; Accepted 03 Sep 2018; Posted 04 Sep 2018  View: PDF

Abstract: An optofluidic variable optical attenuator (VOA) is proposed, where themicrofluidic driving technology adopts the electrically controlled way with the piezoelectricceramics. The proposed driving technology solves some problems of the existing microfluidicdriving technologies and brings the VOA simple structure, small volume, high precision andquick response speed. This VOA has some advantages over other VOAs, such as the widewavelength band (from visible light to near infrared), wide adjustable attenuation range, lowwavelength dependent loss and quick response speed. The experiment results indicate that theattenuation range of this VOA is more than 80 dB and the wavelength dependent loss is 0.09dB at 20 dB attenuation in the C-band. Most VOAs have ms-scale response time, while theresponse time here is about 155-180 μs. Our work gives a new way to gain miniaturizedVOAs with good performances and can also promote optofluidics.

The effect of deviation from purely transverse andlongitudinal polarization states of acoustic waves onthe anisotropy of acousto-optic figure of merit: thecase of Tl3AsS4 crystals

Oksana Mys, Dmitro Adamenko, Oleh Krupych, and Rostyslav Vlokh

Doc ID: 332946 Received 30 May 2018; Accepted 03 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: We analyze the effect of acoustic wave (AW) polarization states deviation from purely longitudinal and transverseon the anisotropy of acousto-optic (AO) figure of merit for the case of AO interactions occurring in the principalcrystallographic planes. In particular, we obtain phenomenological relations that describe the effective elasto-opticcoefficient for the six types of AO interactions, which exhaust all of the possible isotropic AO diffractions. Theserelations are compared for the alternative cases when the deviations of polarization of the AWs from purelylongitudinal and transverse ones are either taken into consideration or completely neglected. Our analysis carriedout on the example of Tl3AsS4 crystals reveals that the deviation of AW polarization from its pure states influencesthe anisotropy of AO figure of merit only when the AO interactions with quasi-transverse AWs are dealt with. Thisfact is caused by peculiar acoustic and elasto-optic properties of Tl3AsS4. On the other hand, the situation canbecome different for other crystalline materials, where the angular dependences of the AO figure of merit can differsignificantly in the cases when the deviation angle increases. This holds true for the AO interactions with bothquasi-transverse and quasi-longitudinal AWs. Under these conditions non-orthogonality of the AWs (or deviationfrom their longitudinal polarization states) affects essentially the AO characteristics. Finally, we determine thegeometries of AO interactions for which the highest AO figures of merit are reached for the Tl3AsS4 crystals.

Polarization Evolution in Single Ring Antiresonant Hollow Core Fibers

NIKHIL JAYAKUMAR, Rudrakant Sollapur, Andreas Hoffmann, Teodora Grigorova, Alexander Hartung, Anka Schwuchow, Joerg Bierlich, Jens Kobelke, Markus Schmidt, and Christian Spielmann

Doc ID: 336557 Received 10 Jul 2018; Accepted 01 Sep 2018; Posted 04 Sep 2018  View: PDF

Abstract: Understanding polarization in waveguides is of fundamental importance for any photonic device and is particularly relevant within the scope of fiber optics. Here we investigate the dependence of the geometry-induced polarization behavior of single-ring anti-resonant hollow core fibers on various parameters from the experimental perspective, showing that structural deviations from an ideal polygonal shape impose birefringence and polarization-dependent loss, confirmed by a toy-model. The minimal output ellipticity was found at the wavelength of lowest loss near the center of the transmission band, whereas birefringence substantially increases towards the resonances. The analysis showed that maximizing the amount of linearly polarized light at the fiber output demands both operating at the wavelength of lowest loss as well as carefully choosing the relative orientation of input polarization. Due to their practical relevance we expect our findings to be very important in fields such as nonlinear photonics or metrology.

Delay-disorder FBG recognition and calibration method for FDML wavelength-swept laser based interrogation system

Xiao Liang, Zhengying Li, YiMing Wang, Yarong Hou, and Peng Shen

Doc ID: 334303 Received 04 Jun 2018; Accepted 01 Sep 2018; Posted 04 Sep 2018  View: PDF

Abstract: Fourier domain mode-locked (FDML) has been used in fiber Bragg grating (FBG) interrogation for a high-speed and long-distance measurement. But the delays induced by long fiber between multi-sensors and interrogation system result in non-neglected wavelength error in this high-speed wavelength-swept system. More seriously, the cross-sweep-cycle and different distance delays may cause the delay-disorder problem which brings on the system unable to determine the order of the delayed peaks and unable to address the location of sensors with corresponding wavelength-encoding characteristic. This letter proposes a novel delayed peak recognition and calibration method in which the laser works at 4 different scanning rates. Confirm the relationship between delayed peaks and sensors with recognition parameters at two low rates and eliminate wavelength error at two high rates. Experimentally results show that this method recognizes the delayed peaks correctly and calibrates wavelength accurately with error below 10 pm.

All-in-Fiber Method of Generating Orbital Angular Momentum with Helically-Symmetric Fibers

Li Li, Shicheng Zhu, Li yan, Shao Xinyu, Almantas Galvanauskas, and Xiuquan Ma

Doc ID: 337725 Received 10 Jul 2018; Accepted 01 Sep 2018; Posted 04 Sep 2018  View: PDF

Abstract: An all-in-fiber method of generating orbital angular momentum is proposed. A simple device composed with a section of helically-symmetric fiber and another section of regular fiber is designed to convert input light to optical vortices. FEM (Finite Element Method) calculation based on coordinates transformation technique is taken to show that the eigenmodes of the helically-symmetric fiber structures carry orbital and spin angular momentum. Simulation using self-developed BPM (Beam Propagation Method) algorithm is also performed to verify the orbital angular momentum generation and evaluate the performance of the OAM generator.

Variable step size adaptive cuckoo search optimizationalgorithm for phase diversity

DEQUAN Li, Shuyan Xu, XIN QI, Dong Wang, and XIAOTAO CAO

Doc ID: 341910 Received 09 Aug 2018; Accepted 31 Aug 2018; Posted 04 Sep 2018  View: PDF

Abstract: Phase diversity (PD) algorithm will eventually be converted into a large-scale nonlinear numerical optimizationproblem, so the selection of numerical optimization algorithm will directly determine the accuracy and speed ofthe algorithm settlement. In this paper, we introduce the cuckoo Search optimization algorithm, which has theadvantages of simple model, few parameters and easy implementation, to the phase diversity algorithm. Byimproving the step size control factor in the original cuckoo Search algorithm, we can make it have fasteroptimization speed for PD. In the simulation experiments, we further proved and gave a simple explanation intheory that in the case of large-scale wavefront sensing, compared to the traditional particle swarm algorithm, thisimproved algorithm has higher accuracy and faster convergence speed. Finally, we set up a simple experimentalsystem, and proved the effectiveness of the improved cuckoo search algorithm for PD.

Fast Decoding Algorithms for Gourlay-Young Coded Apertures

Kevin Byard

Doc ID: 336301 Received 27 Jun 2018; Accepted 31 Aug 2018; Posted 31 Aug 2018  View: PDF

Abstract: A fast decoding algorithm is described for the class offlexible coded aperture design introduced by Gourlayand Young [Appl. Opt. , 4111 (1984)]. The algorithmsignificantly reduces the number of mathematicaloperations required to perform the decoding of imagesproduced using these apertures compared to currentlyknown methods, such as direct decoding, andhence speeds up the image reconstruction. Experimentaltests confirm the efficacy of the fast decoding algorithm,which offers a speed up enabling a typical120 120 element aperture to be decoded in around 1%of the time required for direct decoding.

The properties of unidirectional absorption inthe one-dimensional plasma photonic crystalswith ultra-wideband

Yu Ma, Hao Zhang, HaiFeng Zhang, Ting Liu, and Wenyu Li

Doc ID: 337731 Received 02 Jul 2018; Accepted 31 Aug 2018; Posted 31 Aug 2018  View: PDF

Abstract: In this paper, the properties of tunable unidirectional absorption in theone-dimensional (1D) plasma photonic crystals (PPCs) are theoretically investigated by thetransfer matrix method, which are composed of the dielectric layers, the non-magnetized andmagnetized plasma layers. The simulated results show that an unidirectional ultra-widebandabsorption region (absorption rate is larger than 0.9) whose relative bandwidth is 36.2% canbe obtained in the proposed 1D PPCs. The effects of the parameters of such PPCs on thefeatures of unidirectional absorption region (UAR) also are studied. The computed resultsillustrate that the obtained UARs can be tuned by those parameters as mentioned above, andalso show us another alternative away to realize the reconfigurable unidirectional applicationsin the 1D PPCs.

Modeling method of LADAR scene projector based onphysically based rendering (PBR) technology

YANZE GAO, Xin Wang, yanyan li, Lang Zhou, Qingfeng Shi, and Zhuo Li

Doc ID: 340166 Received 19 Jul 2018; Accepted 30 Aug 2018; Posted 31 Aug 2018  View: PDF

Abstract: LADAR scene projector is a key device in the hardware-in-the-loop (HWIL) simulation system. LADAR scenemodeling is a fundamental work of developing LADAR scene projector. A modeling method based on PBRtechnology and OpenGL is proposed in this paper. This modeling method can quickly generate delay, amplitude,and pulse width data for all return signals in a large array-scale LADAR scene. A 100×100 array size LADAR scenemodel with distance range of 0~3km is simulated. The average data generation time is only 5.31 ms. The distanceresolution is 1.5 m and the peak-valley error is less than 0.15 m. This method achieves efficient modeling and fasthardware update rates, which greatly improves the real-time performance of the LADAR scene projector. It hasstrong practicality and can be directly applied in the HWIL simulation system.

Controlling Goss-Hänchen shifts due to surface plasmon effect in hybrid system

Ghahraman Solookinejad, Masoud Jabbari, Mahdi Nafar, Elnaz Ahmadi, and seyyed Hossein Asadpour

Doc ID: 332398 Received 29 May 2018; Accepted 30 Aug 2018; Posted 30 Aug 2018  View: PDF

Abstract: We have theoretically studied the Goos-Hänchen (GH) shifts of both reflected and transmitted probebeams from a cavity consists of coupled quantum dot (QD) nanostructure and metallic nanoparticle(MNP) hybrid system. It is realized that the GH shifts in transmitted and reflected light beams can beenhanced due to surface plasmon effect in MNP. Also, it is shown that by adjusting the distance betweenQD and MNP, polarization control between probe field and major axis of the hybrid system, thesimultaneous negative and positive GH shifts in reflected and transmitted light beams can be occurred.Moreover, the intensity and detuning effects of coupling light have been discussed on GH shifts propertiesof reflected and transmitted lights, respectively. We have found that due to different parametric conditionsof hybrid system, the GH shifts of reflected and transmitted light beams can be adjusted by tuning theintensity and detuning control of coupling field. The results show that our proposed model may be usedfor future optical sensor devices based on MNP hybrid systems.

SHADOWS: A spectro-gonio radiometer forbidirectional reflectance studies of dark meteorites andterrestrial analogues. Design, calibrations andperformances on challenging surfaces.

Sandra Potin, Olivier Brissaud, Pierre Beck, Bernard Schmitt, Yves Magnard, Jean-Jacques Correia, Patrick Rabou, and Laurent Jocou

Doc ID: 332966 Received 01 Jun 2018; Accepted 30 Aug 2018; Posted 30 Aug 2018  View: PDF

Abstract: We have developed a new spectro-gonio radiometer, SHADOWS, to study in the laboratory the bidirectionalreflectance distribution function of dark and precious samples. The instrument operates over awide spectral range from the visible to the near-infrared (350-5000nm) and is installed in a cold room tooperate at a temperature as low as -20°C. The high flux monochromatic beam is focused on the sample,resulting in an illumination spot of about 5.2mm in diameter. The reflected light is measured by twodetectors with high sensitivity (down to 0.005% in reflectance) and absolute accuracy of 1%. The illuminationand observations angles, including azimuth, can be varied over wide ranges. This paper presents thescientific and technical constraints of the spectro-gonio radiometer, its design and additional capabilities,as well as the performances and limitations of the instrument.

Experimental study of turbulence effect on underwater optical wireless communications

Zahra Vali, Asghar Gholami, Zabih Ghassemlooy, Masood Omoomi, and David Michelson

Doc ID: 335297 Received 15 Jun 2018; Accepted 30 Aug 2018; Posted 31 Aug 2018  View: PDF

Abstract: Underwater optical wireless communications (UOWC) performance is affected by turbulence. However, not much research has been carried out to estimate the probability density function (PDF) of the received optical power. In this paper, we investigate the turbulence effect on UOWC using a new experimental setup with a variable link span in a water pool. Different turbulence levels are created by changing the temperature and the rate of an injected water flow in the pool in order to obtain the PDF. Results show that lognormal distribution fits well with the measured PDF up to the scintillation index value of 0.07. In UOWC systems the link span is one of the main factor influencing fluctuations of the received optical power, which has not been investigated. In this work, we obtain the scintillation index and turbulence induced power loss for a range of turbulence strengths and for a transmission link span of up to 12 m. Finally, we show that there is a good agreement between the experimental and simulated results.

Deep Learning-based object classificationthrough multi-mode fiber via a CNNarchitectureSpeckleNet

Ping Wang and Jianglei Di

Doc ID: 336160 Received 26 Jun 2018; Accepted 30 Aug 2018; Posted 31 Aug 2018  View: PDF

Abstract: With fast development of deep learning, its performing on image classification andobject recognition has presented dramatical improvements. These promising results couldalso be applied for better understanding of the speckle patterns in scattering media imaging.In this paper, a multi-mode fiber is used as the scattering media and 4000 face and non-faceoriginal images go through it generating speckle patterns. A SpeckleNet is proposed andtrained with these 3600 speckle patterns based on convolutional neural network and its outputlayer are activated for support vector machine (SVM) classifier. The binary classificationaccuracy of proposed CNN-architecture SpeckleNet for face and non-face speckle patternsclassification tested on another 400 speckle patterns is about 96%, which has been improvedcompared with the accuracy of pure SVM method. The promising results confirm thecombination with deep learning could lead to less optical and computation costs in opticalsensing that could contribute applications of optics using in practice.

CIOMP- Rapid fabrication strategy for ø1.5m OAP using CCOS method

Haixiang Hu, Er Qi, Xiao Luo, Xuejun Zhang, and Xue Donglin

Doc ID: 336256 Received 03 Jul 2018; Accepted 30 Aug 2018; Posted 31 Aug 2018  View: PDF

Abstract: Off-axis parabolic parts (OAP) or quasi-OAPs are mostly frequently used in large optical telescopes. Compared with the stressed mirror polishing, computer-controlled optical surfacing (CCOS) method or other computer-controlled sub-aperture tools provide more flexibility. However, it is the very need to promote its fabrication efficiency in tactic ways. In the paper, we present a large aperture CCOS lap equipped with a compound motion unit, and go through the grinding and pre-polishing with its figure errors. CCOS-based heterocercal tool is first used in large optics to restrain the edge effects. In fine polishing stage, corrective polishing, smoothing, and ion beam figuring (IBF) are applied in combination to finish. We experimentally test this strategy on an ø1.5m OAP, as a part of Giant Steerable Science Mirror (GSSM) in the Thirty Meter Telescope (TMT). Finally, the surface error of ø1.5m OAP is better than 1/50 λ RMS (full aperture), and the mid-spatial frequency part is as better as 0.64μrad in slope RMS (effective aperture). The effective fabrication duration is reduced to 2 month.

Design of a Sensitive Uncooled Thermal ImagerBased on a Liquid Crystal Fabry-PerotInterferometer

COLIN MCGINTY, Robert Reich, Harry Clark, Valerie Finnemeyer, Shaun Berry, and Philip Bos

Doc ID: 336277 Received 26 Jun 2018; Accepted 30 Aug 2018; Posted 31 Aug 2018  View: PDF

Abstract: Microbolometers are the dominant technology for uncooled thermal imaging, however, devices based on a directretardation measurement of a liquid crystal (LC) transducer pixel have been shown to have comparable sensitivity.In this paper, an approach for increasing LC transducer sensitivity utilizing an etalon structure is considered. Adetailed design for an LC resonant cavity between dielectric mirrors is proposed and the performance is evaluatednumerically. The measured quantity is the transmission of a visible wavelength through the etalon which requiresno thermal contact with the IR sensor. Numerical and analytical calculations which consider a 470 nm-thick LCpixel demonstrate that the change in transmitted intensity with temperature is 26 times greater in the devicebased on a resonant structure than in a device based on a direct retardation measurement. Finally, the paperdiscusses how the dielectric mirror materials, dimensions of the resonant cavity structure, and expected processtolerances affect the sensitivity of the device.

Design of retina-like transmitting system based oncurved lens array

Qun Hao, LINGTONG MENG, yang cheng, jie CAO, Sihui Li, and Saad Rizvi

Doc ID: 331854 Received 16 May 2018; Accepted 30 Aug 2018; Posted 07 Sep 2018  View: PDF

Abstract: In order to reduce data redundancy and improve scanning efficiency in three-dimensional (3D)imaging, a retina-like transmitting optical system based on curved lens array (CLA) is proposed. Themathematical model for the transmitting system is developed, and associated parameters for the space-variantCLA are studied. Model testing validates that the transmitting system bears flexible scanning field of view andachieves scanning efficiency upto 80%. Imaging simulations show that the proposed scanning method utilizingthe logarithmic polar imaging characteristics efficiently detects secondary targets. Furthermore, simulationresults show that the parameters of the single lens in the lens array are not fixed, but flexible, which facilitatesthe corresponding structural design.

Adaptive correction of retardations with immunity to alignment errors for a channeled spectropolarimeter

Xueping Ju, Changxiang Yan, Junqiang Zhang, Bin Yang, and Wenhe Xing

Doc ID: 337916 Received 04 Jul 2018; Accepted 29 Aug 2018; Posted 30 Aug 2018  View: PDF

Abstract: Retardation errors of high-order retarders will decrease the accuracy of a channeled spectropolarimeter. Taniguchi et al. have proposed a self-calibration method to calibrate the retardations [Opt. Lett 31, 3279 (2006)], however, they do not take into account the influences of inevitable alignment errors of high-order retarders. In this paper, an adaptive correction method with immunity to alignment errors is proposed to reduce the effects of temperature variation on retardations. By separating and analyzing the amplitude terms and phase terms contained in measurement data, the phase terms are utilized to correct the retardations, which makes the effectiveness of this adaptive correction method is immune to the inevitable alignment errors of high-order retarders. The adaptive correction process can be accomplished in parallel to the measurement process without any auxiliary resources. The effectiveness and feasibility of this method is verified by simulations and experiments. The convenience and simplicity of the presented method make it extremely suitable for application on track.

Polarization-maintaining Yb-doped large-modearea fully-aperiodic large-pitch fibers

Rémi du Jeu, Romain Dauliat, Baptiste Leconte, Marie-Alicia Malleville, Raphael Jamier, joerg bierlich, Anka Schwuchow, Kay Schuster, and Philippe ROY

Doc ID: 338685 Received 17 Jul 2018; Accepted 29 Aug 2018; Posted 30 Aug 2018  View: PDF

Abstract: Based on a special large-pitch architecture which already proved its single-modesingle-polarization behavior in a passive configuration, two ytterbium-doped versions of suchlarge-mode area fibers have been fabricated and tested in both laser and amplificationconfigurations for high power laser source applications. Due to the high sensitivity of LPFdesign to the active core to passive cladding index mismatch, the realization of a singlepolarizationstructure is highly challenging. However, we report on the preservation of apolarization-maintaining feature. A linear polarization with an extinction ratio of 17 dB isdemonstrated for mode field diameters reaching up to 58 μm as long as the singlemodeness ofthe emitted signal is preserved.

Using Spherical Harmonics to Describe Large-AngleFreeform Lenses

Caleb Gannon and Rongguang Liang

Doc ID: 334744 Received 11 Jun 2018; Accepted 28 Aug 2018; Posted 04 Sep 2018  View: PDF

Abstract: We propose the use of spherical harmonics for large-angle freeform lenses as a dramatic improvementover polynomials set on the disk and plane such as Zernike and X-Y polynomials. This new representationenables fitting of surfaces designed in spherical coordinates, such as freeform illumination lensesthat would be impossible to describe with respect to a plane. The proposed representation is validatedthrough an extremely compact, high performance design.

Tunable temperature dependent THz photonic bandgaps and localization modes engineering in 1-D periodic and quasi-periodic structures with graded index materials and InSb

Bipin Singh and Praveen C Pandey

Doc ID: 332394 Received 30 May 2018; Accepted 28 Aug 2018; Posted 29 Aug 2018  View: PDF

Abstract: We present the tunability of terahertz photonic bandgaps and localization modes in one-dimensional periodic and quasi-periodic structures based on alternated layers of graded index materials and InSb. These configurations show that operation frequencies of photonic bands and localization modes can be tuned by controlling temperature, structural and grading parameters, grading profiles and different quasi-periodic arrangements. Numbers of photonic bands and localization modes can also modulate with layer thickness and quasi-periodic arrangements. The change in the grouping of considered materials also modulate the operation frequencies of photonic bands and localization modes in quasi-periodic structures. Results can be implemented to design thermo-tunable THz filters, reflectors and sensors, etc.

Measurement investigation of off-axis asphericsurface via hybrid compensation method

Shijie Li, Jin Zhang, Weiguo Liu, Zhongda Guo, Hong Li, Yang zhi-qiang, Bingcai Liu, Ailing Tian, and Xiaoqin Li

Doc ID: 337674 Received 04 Jul 2018; Accepted 28 Aug 2018; Posted 04 Sep 2018  View: PDF

Abstract: To measure the profile of off-axis aspheric surface with large asphericity or lateraldisplacement, a hybrid compensation method is employed to realize null test. Firstly, the hybridcompensation method is simulated in MATLAB by using fold sphere mirror and computer-generated hologram (CGH) for compensating primary aberration and residual high orderaberration, respectively. As a contrast, the hybrid compensation method is also simulatedin Zemax by using dummy glass. Through comparing the simulation results of MATLAB andZemax, the test CGH fringe positions from the two results are well matched. Then, the foldsphere mirror and CGH optical elements are designed and fabricated for actual hybrid compensationtesting, and the auto-collimation method is also used to detect the same off-axisaspheric surface. To ensure the correctness of the experiment, the result of actual hybrid compensationtesting is contrasted with that of auto-collimation method. Experiments show thatthe results obtained by the two methods are consistent, which indicates that this kind of hybridcompensation is an effective and accuracy method for measurement of off-axis asphericsurfaces.

Multiple off-axis fiber Bragg gratings for 3D shapesensing

Christian Waltermann, Konrad Bethmann, Alexander Doering, Yi Jjang, Anna Baumann, Martin Angelmahr, and Wolfgang Schade

Doc ID: 335364 Received 15 Jun 2018; Accepted 27 Aug 2018; Posted 27 Aug 2018  View: PDF

Abstract: Point-by-point femtosecond laser processed fiber Bragg gratings are arranged around the edge of a standardsingle-mode optical fiber core. The relative amplitudes of at least three such fiber Bragg gratings are utilized todetect the central position of the mode field within the fiber core and calculate the local curvature of the fiber. Ananalytical approximation is given and an experimental validation is performed.

Narrowband wavelength selective waveguide for see-through glasses

XUE XIAO, Lin Zhang, Xiao Lin, Jinliang Zang, and Xiaodi Tan

Doc ID: 335883 Received 22 Jun 2018; Accepted 25 Aug 2018; Posted 27 Aug 2018  View: PDF

Abstract: See-through glasses are a new type of portable mobile device; however, mostexisting designs cannot balance the requirements of field-of-view (FOV), optical efficiencyand system volume at the same time. Here we propose a design for ultra-compact see-throughglasses by using a waveguide with embedded narrowband minus filters as the opticalcombiner. The optical combiner demonstrates wavelength-selectivity and optionalnarrowband(s), and is based on inorganic materials. Compelling advantages of our approachare high light efficiency, stray ray suppression, full-color capacity, good stability and lowcost. A detailed calculation model is provided for analysis of the optical properties of thewaveguide, and a proof-of-concept prototype is demonstrated that can convey a horizontalFOV of 31.4°. The FOV can be further enlarged by parameter adjustments.

Transient processes under excitation of ultrashortlaser pulses in colloidal solutions of CdSe/ZnSquantum dots

Vladimir Danilov, Anastasia Panfutova, and Nickolay Sibirev

Doc ID: 334240 Received 01 Jun 2018; Accepted 25 Aug 2018; Posted 27 Aug 2018  View: PDF

Abstract: We present, that in the case of picosecond durations, the limitation efficiency of laser radiation and absorptionkinetics in CdSe/ZnS colloidal solutions are determined by the Auger relaxation through the 1S(e) states. In theobserved kinetics of a probe-pulse transmission “delayed limitation” effect has been detected. Numerical modelinghas made it possible to identify the competition between the next two relaxation processes of highly excited states:relaxation through size quantization levels and phononless relaxation through traps states.

Potential use of surface-assisted LIBS fordetermination of Sr in wines

Jana Bocková, Alicia Marin-Roldan, Jin Yu, and Pavel Veis

Doc ID: 331397 Received 10 May 2018; Accepted 18 Aug 2018; Posted 05 Sep 2018  View: PDF

Abstract: Laser Induced Breakdown Spectroscopy (LIBS) is well-established technique for the elemental analysis and hasbeen widely used for qualitative and quantitative analysis of different solid samples. LIBS is also well-known fornot requiring sample preparation, but the analysis of liquids is actually a great challenge. In the present work, anovel approach of elemental analysis of liquids with organic matrix has been performed, making a liquid-to-solidmatrix conversion by drying wine samples on aluminum and silicon wafers, which have demonstrated an increasein LIBS analytical performance. A red wine from Slovakia (not blended with any other variety or wine from otherregions or adulterants) was prepared according to the procedure consisting in drying 2 ml of wine dropped on asolid wafer having a flat surface area of about 25 cm2. Surface-assisted LIBS in combination with conversion ofliquid into solid avoids the difficulties and limitations of working with liquid samples by LIBS, improving the limitof detection, repeatability and sensitivity. The quantification of Sr has been realized by addition of knownconcentration of SrCl2·6H2O in wine before the drying process. Sr is an important element among those usually usedas markers for the identification of the soils on which the vines grow. Two ionic (407.771 nm and 421.552 nm) andtwo neutral (460.733 nm and 481.188 nm) Sr lines were used to plot the calibration curves in order to study thelimits of detection (LODs) and the matrix effects for the analysis of Sr in the tested wines and for the different wafermaterials. This direct surface-assisted LIBS measuring method has been successfully applied for the determinationof Sr in red wine sample from Slovakia and the obtained results with two kinds of substrate (Al and Si) werecompared. Finally, a validation sample has been employed to test the accuracy of the established calibrationcurves.

Lidar algorithms in 3D scanning for atmosphericlayering and planetary boundary layer heightretrieval. Comparison with other techniques

Alexandros Pantazis, Alexandros Papayannis, and Georgios Georgoussis

Doc ID: 334549 Received 08 Jun 2018; Accepted 14 Aug 2018; Posted 15 Aug 2018  View: PDF

Abstract: The Planetary Boundary Layer Height (PBLH), of great importance in meteorology andatmospheric physics, is strongly correlated with the geographical location, the solar irradiance, theseasonal variations and the variability of the weather phenomena. So far, several lidar techniqueshave been developed to detect the PBLH, beside the radiosoundings, sodars or other techniques. Inthis work we propose new algorithms to provide PBLH in near real time using a 3 dimensional (3D)lidar in vertical or slant pointing. We show that the proposed Variable SPAce Time (VASPAT) andVERtical DEcision (VERDE) algorithms are able to estimate the PBLH under various meteorologicalconditions of more than 80% of the cases studied. Furthermore, these algorithms are user friendly(user adjustable), they work automatically at any location and period of the year for any vertically/slant pointing lidar system. These algorithms are extremely helpful for meteorologists, airporttower controllers, atmospheric scientists and in general for the remote sensing community.

Passive Q-switching of Yb:CNGS lasers by Cr4+:YAGand V3+:YAG saturable absorbers

Xuzhao Zhang, Pavel Loiko, Josep Maria Serres, Venkatesan Jambunathan, zhengping wang, Yi Guo, Anatol Yasukevich, Antonio Lucianetti, Tomas Mocek, Uwe Griebner, Valentin Petrov, Xin-guang Xu, Magdalena Aguilo, Francesc Diaz, and Xavier Mateos

Doc ID: 334212 Received 07 Jun 2018; Accepted 13 Aug 2018; Posted 15 Aug 2018  View: PDF

Abstract: Trigonal langasite-type ordered silicate crystal Yb:Ca3NbGa3Si2O14 (Yb:CNGS) is a promising material for efficient~1 μm lasers. We report on the first passively Q-switched Yb:CNGS laser using Cr4+:YAG and V3+:YAG saturableabsorbers (SAs) with a 976 nm Volume Bragg Grating (VBG)-stabilized diode as a pump source. The laser crystalwas a c-cut 3 at.% Yb:CNGS grown by the Czochralski method. It was placed in a compact microchip-type lasercavity. With a Cr4+:YAG SA, very stable 62.2 μJ / 4.4 ns pulses were achieved at a repetition rate of 22.5 kHz. Theaverage output power was 1.40 W at 1015.3 nm corresponding to a Q-switching conversion efficiency of 90%. Withthe V3+:YAG SA, the pulse characteristics were 13.3 μJ / 11.1 ns at a higher repetition rate of 68.4 kHz. Theperformance of the Yb:CNGS/Cr4+:YAG was numerically modelled showing a good agreement with the experiment.

Fast and Precise 6D Pose Estimation of Texture-lessObjects Using the Point Cloud and Gray Image

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

Doc ID: 328945 Received 20 Apr 2018; Accepted 07 Aug 2018; Posted 09 Aug 2018  View: PDF

Abstract: Pose estimation for texture-less objects is a challenging task in robotics, due to the scanty information of surfaces.In this paper, we design a vision system for fast and precise position and orientation measurement of texture-lessobjects with a depth camera and a CCD camera. The corresponding process includes two parts: object segmentationin the point cloud and pose measurement in the gray image. Considering the relation between the object and itsfixed panel, we first extract the panel in the point cloud by combining the RANSAC algorithm with local surfacenormal. And then coarsely segment the possible area of the object based on oriented bounding box. Finally,transform the point cloud coordinates into the image coordinate system, and measure the precise pose of theobject with a view-based matching method. Two types of cameras are brought together to make their respectiveadvantages play well. Downscale method and coarse to fine strategy are utilized sufficiently to increase efficiency.Experiments show that our vision system achieves high pose measurement precision and enough efficiency. Theaverage error is less than 2 mm for x, y, less than 4 mm for z and 1° in orientation, meeting the requirements forour robotic grasping task.

Multicore optical fiber based vibration sensors for biomedical applications

Md Rejvi Kaysir and Md Jahirul Islam

Doc ID: 331662 Received 16 May 2018; Accepted 28 Jul 2018; Posted 30 Jul 2018  View: PDF

Abstract: Vibration is one of the key parameters for extracting information from surrounding environments, and optical fiber-based sensors show great promise for achieving such information. In this work, an intensity-based multicore fiber (MCF) based vibration sensor is designed, fabricated and characterized for biomedical applications. The fabricated MCF has seven cores, in which the middle core is used for launching light and the surrounding cores are used for collecting lights from any reflective substances. The working principle of the MCF sensor is based on the intensity modulation of reflected light from vibrating substances that is coupled to the collecting cores (i.e. side cores) of the MCF. Here, light from a 532 nm laser was launched into the middle core of the MCF and the reflected light from a mirror, situated at the output face of MCF, was collected from a single side core. To characterize the sensor and demonstrate the sensing activities of MCF, two experimental approaches were taken: (i) static sensitivity and (ii) dynamic measurements. The static measurement demonstrated the region of maximum sensitivity and helped to find out the optimal design parameters of MCF for any desired applications. A simple ray tracing model also included getting the maximum sensitive regions of the designed sensor that verifies our experimental results. Dynamic measurement demonstrates the vibration sensing activities of the sensor. This information provides pathways to design MCF based vibration sensors for the specific applications.

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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