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Accepted papers to appear in an upcoming issue

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Architecture and performance analysis of an optical metrology terminal for satellite-to-satellite laser ranging

Oliver Mandel, Alexander Sell, Michael Chwalla, Thilo Schuldt, Jasper Krauser, Dennis Weise, and Claus Braxmaier

DOI: 10.1364/AO.378658 Received 25 Sep 2019; Accepted 06 Dec 2019; Posted 06 Dec 2019  View: PDF

Abstract: Interferometric laser ranging is an enabling technology for high-precision satellite-to-satellite tracking within the context of earth observation, gravitational wave detection, or formation flying. In orbit, the measurement system is affected by environmental influences, particularly satellite attitude jitter and temperature fluctuations, imposing an instrument design with a high level of thermal stability and insensitivity to rotations around the spacecraft center of mass. The new design concept presented here combines different approaches for dynamic heterodyne laser ranging and features the inherent beam tracking capabilities of a retroreflector in a mono-axial configuration. It allows for a continuously adjustable distance between the optical bench and the location of its fiducial point, facilitating future inter-satellite tracking with nanometer accuracy, e.g., the next-generation gravity mission.

Optoelectronic Optimization of Graded-Bandgap Thin-Film AlGaAs Solar Cells

Faiz Ahmad, Akhlesh Lakhtakia, and Peter Monk

DOI: 10.1364/AO.381246 Received 22 Oct 2019; Accepted 06 Dec 2019; Posted 06 Dec 2019  View: PDF

Abstract: An optoelectronic optimization was carried out for an AlGaAs solar cell containing an n-AlGaAs absorber layer with a graded bandgap, a periodically corrugated Ag backreflector combined withlocalized ohmic Pd-Ge-Au backcontacts. The bandgap of the absorber layer was varied either sinusoidallyor linearly. An efficiency of 33.1% with the 2000-nm-thick n-AlGaAs absorber layer is predicted with linearlygraded bandgap along with silver backreflector and localized ohmic backcontacts, in comparisonto 27.4% efficiency obtained with homogeneous bandgap and a continuous ohmic backcontact. Sinusoidalgrading of the bandgap enhances the maximum efficiency to 34.5%. Thus, grading the bandgap ofthe absorber layer, along with a periodically corrugated Ag backreflector and localized ohmic Pd-Ge-Aubackcontacts can help realize ultrathin and high-efficient AlGaAs solar cells for terrestrial applications.© 2019 Optical Society of America

Micro-integrated high-power narrow-linewidth external-cavity tapered diode laser at 808 nm

Mingjun Chi, André Mueller, Anders Hansen, Ole Jensen, Paul Petersen, and Bernd Sumpf

DOI: 10.1364/AO.381439 Received 24 Oct 2019; Accepted 05 Dec 2019; Posted 06 Dec 2019  View: PDF

Abstract: A novel compact micro-integrated high-power narrow-linewidth external-cavity diode laser around 808 nm is demonstrated. The laser system contains a tapered amplifier consisting of a ridge-waveguide section and a tapered section with separated electrical contacts. Thus the injection currents to both sections can be controlled independently. An external volume Bragg grating is utilized for spectral narrowing and stabilization. The diode laser system is integrated on a 5 mm x 13 mm aluminum nitride micro-optical bench on a conduction cooled package mount with a footprint of 25 mm x 25 mm. The diode laser system is characterized by measuring the output power and spectrum with the injection currents to the ridge-waveguide section (IRW) and tapered amplifier section (ITA) changed in steps of 25 and 50 mA, respectively. At IRW = 200 mA and ITA = 6.0 A, 3.5 watts of output power is obtained with an emission spectral linewidth with an upper bound of 6 pm, and a beam propagation factor in the slow axis, M2, of 2.6 (1/e2). The characterization of the temperature stabilization of the laser system shows an increase of the wavelength at a rate of 6.5 pm/K, typical for the applied volume Bragg grating.

Extended cavity diode laser master-oscillator-power-amplifier for precision iodine spectroscopy in space

Christian Kürbis, Ahmad Bawamia, Mandy Krüger, Robert Smol, Achim Peters, Andreas Wicht, and Guenther Traenkle

DOI: 10.1364/AO.379955 Received 21 Oct 2019; Accepted 05 Dec 2019; Posted 06 Dec 2019  View: PDF

Abstract: We present a hybrid micro-integrated diode laser module developed for iodine spectroscopy on board a sounding rocket. The laser module is based on a master-oscillator-power-amplifier concept: an extended cavity diode laser serves as the master oscillator, and a ridge-waveguide semiconductor optical amplifier provides the power boost. The module’s form factor and mass correspond to 12.5 x 7.5 x 2.3 cm³ and 750 g, respectively. With an electrical power of 3.75 W supplied to the module, 570 mW of optical powerare provided out of a polarization maintaining optical fiber at 1064.490 nm with a technical linewidth of 20 kHz (75 kHz) at a 1 ms (10 ms) timescale. The laser module has successfully passed vibration tests at a level of 8.8 gRMS. A nominally identical module has recently been used to demonstrate, for the first time, precision iodine spectroscopy in space.

Decoupling and detecting the angular motion errors based on a line laser sensor for motion platforms

Cheng Chen, Hongru Zhang, Shaoxuan Chen, Bing Liu, Kai Zhang, and Hongwei Ji

DOI: 10.1364/AO.380551 Received 18 Oct 2019; Accepted 05 Dec 2019; Posted 06 Dec 2019  View: PDF

Abstract: Abstract: Efficient measurement of a line laser sensor can be achieved by combining with a multi-axis platform. However, the measuring results are significantly affected by the precision of the platform. To provide a criterion of verifying and compensating the geometric errors of a platform, a measuring method based on a line laser sensor for angular motion errors is proposed for the first time in this work. The principles of separating and simultaneously detecting the yaw, roll and pitch errors are elaborated. Based on this, the detection model is built for three-dimensional platform. Under such an experimental condition, the stability and accuracy of the line laser sensor is tested, and the experimental results revealed a small deviation of 3 μm and 10 μm in z-axis and x-axis, respectively. Ultimately, a series of experiments are performed to verify the feasibility and repeatability of the method. The yaw experimental results indicate that the trend and rule of error conform to the measured value by a laser interferometer, and the maximum variation value is 0.0075 mrad.

Comprehensive polychromatic integral diffraction efficiency sensitivity to tilt error for multilayer diffractive optical elements with oblique incidence

Liangliang Yang, CHENGLIN LIU, Renjia Guo, and Yongbing Zhao

DOI: 10.1364/AO.382110 Received 31 Oct 2019; Accepted 05 Dec 2019; Posted 05 Dec 2019  View: PDF

Abstract: Oblique incidence is the general working state for multilayer diffractive optical elements (MLDOEs) in imaging optical system. The polychromatic integral diffraction efficiency (PIDE) is very sensitive to the incident angle. Therefore, it is necessary to analyze the effect of tilt error on diffraction efficiency/ PIDE with oblique incidence. The theoretical model of the relationship between the diffraction efficiency and tilt error with oblique incidence is presented, and the effect of tilt error on diffraction efficiency/PIDE are analyzed. The analysis model of comprehensive PIDE for a certain range of incident angle and the tilt error for MLDOEs is established. The simulation results showed that the comprehensive PIDE is sensitive to tilt angle with oblique incidence, and the tolerance of the tilt error angle can be determined by the comprehensive PIDE. The tilt error tolerance is furthermore investigated with decenter error based on the maximum of comprehensive PIDE. The method and results can be used to guide the tolerance formulation of tilt error for MLDOEs in hybrid optical systems.

Elliptical-Spiral Elliptical-Hole Photonic Crystal Fiber with High Birefringence, Large Nonlinearity, and Two Zero Dispersion

Shanshan Zhang, Weiguang Shi, Cheng Zhang, Jia Shi, Jixuan Wu, Hongqiang Li, Yange Liu, and Bo Zhang

DOI: 10.1364/AO.378190 Received 26 Sep 2019; Accepted 04 Dec 2019; Posted 06 Dec 2019  View: PDF

Abstract: This paper presents a soft glass (SF-57) elliptical-spiral photonic crystal fiber with elliptical air holes for achieving high birefringence, large nonlinearity and tailoring two zero dispersion wavelengths (ZDWs) in the near infrared region. A full-vector finite-element method with perfectly matched boundary layer is used to characterize the properties of the PCF for different ellipticity ratios. The designed fiber has a birefringence 4 times higher than the circular spiral structure. There are two ZDWs at around 1.2μm and 2.8μm which can be finely tuned depending on the ellipticity ratios along with a large nonlinearity. Due to the superior guiding properties, the proposed structure can be used for polarization control and broadband supercontinuum generation (SCG).

Towards a Locally Adaptive Optical ProtectionFiltering for Human Eyes and Technical VisionSensors

Vasily Ezhov, Natalia Vasilieva, Ivashkin Ivashkin, and Alexander Galstian

Doc ID: 379454 Received 02 Oct 2019; Accepted 04 Dec 2019; Posted 04 Dec 2019  View: PDF

Abstract: In the presence of direct sunlight or super bright light from artificial optical sources, the distribution of lightintensity (brightness) over perceived scene objects typically has a dynamic range several orders of magnitudegreater than the dynamic range of the most optical sensors. In this paper, the locally adaptive optical protection(LAOP) filtering systems for technical vision sensors and human eyes (human visual system) are suggested. TheLAOP filtering provides the reliable perception of the perceived scene objects with normal brightnesssimultaneously with preventing saturation (“blinding”) of the optical sensors by light from the brightest objects.Characteristics of the key components of the LAOP filtering systems are discussed and tested experimentally.

In-situ synthesis of silver nanoparticles on periodic supports as highly active and flexible SERS substrates

Jiajie Zhang, Chaonan Wang, Tian Xu, and Meng Wang

DOI: 10.1364/AO.378734 Received 24 Sep 2019; Accepted 04 Dec 2019; Posted 05 Dec 2019  View: PDF

Abstract: As regard to Surface Enhanced Raman Scattering (SERS), the preparation of substrates with high homogeneity and low cost remains a challenge. In this paper, cheap commercial DVD-R plates were adopted as supports, whose 3D periodic structure was transferred onto the surface of flexible PDMS easily. Then, silver nanoparticles were grown both on DVD and PDMS substrates by in-situ reduction method, and the SERS performances of these two substrates were investigated. The results confirmed that the PDMS-based substrate exhibited better enhancement performance and higher uniformity (RSD = 4.16%). In addition, due to the flexibility and transparency of PDMS, it is not restricted by the surface shape of the object when applied in in-situ detection. This low-cost, simple method will be widely used in the in-situ detection of surfaces of objects of any shape.

All optical Fredkin gate using phtonic crystal based nonlinear cavities

hamed Alipour-Banaei, Mahdi Hassangholizadeh-kashtiban, MOHAMMAD BAGHER TAVAKOLI, and Reza Sabbaghi-Nadooshan

DOI: 10.1364/AO.379613 Received 07 Oct 2019; Accepted 04 Dec 2019; Posted 05 Dec 2019  View: PDF

Abstract: An all optical Fredkin gate was proposed and designed. The Fredkin gate is a reversible logic gate. For designing the proposed structure we used three different optical nonlinear resonators. The wide bandwidth resonators do not have switching functionality. However the proposed resonator was modified to act as an optical switch in horizontal direction. The final structure was designed using four wide band resonators, twelve sharp resonators and four nonlinear ring resonators. Simulation results show that the maximum rise time of the proposed structure is about 5 ps.

Glancing-angle–deposited silica films forultraviolet wave plates

Sara MacNally, Chris Smith, John Spaulding, Justin Foster, and James Oliver

Doc ID: 378079 Received 16 Sep 2019; Accepted 03 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: Birefringent silica films are formed by glancing-angle deposition to fabricatequarter- and half-wave plates at a wavelength of 351 nm. A multilayer design is implementedto achieve low-loss transmittance with a high 351-nm laser-induced–damage threshold.

Cross-Correlation Registration AlgorithmEnhancements for Multi-pixel ISAL

John Hennen and Matthew Dierking

Doc ID: 379506 Received 03 Oct 2019; Accepted 03 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: The accurate registration and re-alignment of complex signal volumes is critical for crossrangeaperture gain in 3D LiDAR aperture synthesis. For targets at long range, only a limitednumber of diffraction limited pixels will be projected on the target, resulting in low crossrange support. In addition, the signal to noise ratio (SNR) is typically low. This researchdescribes an enhanced cross-correlation registration algorithm for 3D ISAL data volumes thatimproves performance for low cross-range support, low SNRs and relatively large apertureshifts. The registration performance is improved through statistical removal of the crosscorrelationnoise pedestal and compensation for the reduced signal overlap caused by largershifts. The registration performance is characterized as a function of SNR, signal shift (targetrotation rate), and target pixel support. The algorithm’s improvements allow for registrationconvergence at 1-5 dB lower SNR than the baseline cross-correlation algorithm. In addition,the algorithm enhancements allow for registration convergence at 10-20% greater shifts.

Polarization imaging model considering thenon-ideality of polarizers

Jie Yang, Su Qiu, Weiqi Jin, Xia Wang, and Fuduo Xue

Doc ID: 380824 Received 18 Oct 2019; Accepted 03 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: Common polarization imaging models are mostly based on an ideal polarizerassumption. This paper proposes a polarization imaging non-ideal model considering the nonidealityof polarizers, and the corresponding correction formulas for degree of linearpolarization (DoLP) and angle of polarization are also provided. Experiments on linearlypolarized light and partially polarized light reflected by a glass plate suggest that when theextinction ratio of polarizers is 100:1, the DoLP relative error of linearly polarized light withthe non-ideal model is reduced by 1.87% compared to that with the ideal model; the DoLPrelative error of partially polarized light with the non-ideal model is reduced by 1.69%compared to that with the ideal model. Application of the non-ideal model can effectivelyimprove the precision of polarization measurement. In particular, this improvement is moreobvious with a low-extinction-ratio (less than 100:1) analyzer.

Integrated PCA denoising technique for Φ-OTDRvibration detection

Atubga Ibrahim, Shengtao Lin, Ji Xiong, Jialin Jiang, Yun Fu, and Zinan Wang

Doc ID: 377029 Received 05 Sep 2019; Accepted 03 Dec 2019; Posted 04 Dec 2019  View: PDF

Abstract: This paper presents an Integrated Principal Component Analysis (IPCA) technique in denoising phase sensi- tive optical time domain reflectometry (Φ-OTDR) sens- ing data for vibration detection. As one of the key distributed optical fiber sensing technologies, it has greatly attracted great attention due to its merits of high sensitivity, fast speed response, dynamic range and vi- bration detection abilities, among others. In order to enhance vibration detection along the sensing fiber, ap- propriate denoising method must be carefully selected. Hence, the PCA which can effectively reduce noise on signals while preserving significant details of the de- noised signal is identified. It was then applied on the said signal after digital down-conversion where the noise was greatly reduced. Then angle and phase un- wrapping was performed and the vibration was clearly detected with a significant enhancement of the Signal to Noise Ratio (SNR). As proof of concept, the theoret- ical analysis and an experimental demonstration of avibration sensing range of 800m is presented.

Modifications of ion beam sputtered tantala thin filmsby secondary argon and oxygen bombardment

Le Yang, Emmett Randel, Gabriele Vajente, Alena Ananyeva, Eric Gustafson, Ashot Markosyan, Riccardo Bassiri, Martin Fejer, and Carmen Menoni

Doc ID: 377788 Received 17 Sep 2019; Accepted 03 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: Amorphous tantala (Ta2O5) thin films were deposited by reactive ion beam sputtering with simultaneous lowenergy assist Ar+ or Ar+/O2+ bombardment. Under the conditions of the experiment, the as-deposited thin films areamorphous and stoichiometric. The refractive index and optical band gap of thin films remain unchanged by ionbombardment. Around 20% improvement in room temperature mechanical loss and 60% decrease in absorptionloss are found in samples bombarded with 100-eV Ar+. A detrimental influence from low energy O2+ bombardmenton absorption loss and mechanical loss is observed. Low energy Ar+ bombardment removes excess oxygen pointdefects, while O2+ bombardment introduces defects into the tantala films.

High temporal and spatial resolution single-shot digitalholography with Fresnel domain filtering by usingwitch’s hat illumination

Daichi KISHIWAKI, Kenichi Nisaka, and Takanori Nomura

Doc ID: 377843 Received 18 Sep 2019; Accepted 02 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: High-resolution single-shot on-axis digital holography is proposed. Generally, an on-axis configurationsamples carrier fringes with higher spatial resolution, compared to an off-axis configuration. However,the reconstructed image is obtained with unnecessary images of a conjugate image and a zero-order beam.The proposed method uses a phase modulated illumination beam and image processing to eliminatethese unnecessary images. Since time-division and parallel phase-shifting methods are not required, theproposed method has higher temporal and spatial resolutions. In the image processing, the conjugateimage is removed by filtering on the Fresnel domain while keeping most of the information of the objectimage intact. The usefulness of the proposed method is confirmed by a numerical simulation and anoptical experiment.

1/f noise analysis of 980 nm InGaAs/GaAs laser diodesbelow the lasing threshold

Xiaojuan Chen and Chang Qu

Doc ID: 377906 Received 17 Sep 2019; Accepted 02 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: We present a 1/f noise model of 980 nm InGaAs/GaAs laser diodes operated below the lasing threshold to study thecorrelation between 1/f noise and fluctuation of surface non-radiative recombination current nrI . In InGaAs/GaAslaser diodes, non-radiative recombination current components have been identified as being primarily related tosurface recombination, which depends on surface oxide traps and lattice dislocation. An analysis of the experimentalcomparison of nr I and 1/f noise spectral density with constant current and temperature aging tests further showsthe correlation and verify the 1/f noise model, which can be interpreted as a change in carriers and trap density of acertain surface. This model permits facet stability to be investigated.

Automatic method for segmenting leaves by combining 2D and 3D image-processing techniques

Kenta Itakura and Fumiki Hosoi

Doc ID: 378016 Received 16 Sep 2019; Accepted 02 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: In this study, a method to automatically segment plant leaves from 3-dimensional (3D) images using structure from motion is proposed. First, leaves in the 3D images are roughly segmented using a region-growing method in which near points with distances less than 0.2 cm are assigned to the same group. By repeating this process, the leaves not touching each other can be segmented. Then, each segmented leaf is projected onto 2-dimensional images, and the watershed algorithm is executed. This process successfully segments overlapping leaves.

Three-dimensional Reconstruction MethodBased on Bionic Active Sensing in PrecisionAssembly

Zihao Ding, Guodong Chen, Zheng Wang, Wenzheng Chi, Hui Xu, Heng Zhang, Zhenhua Wang, Lining Sun, Guilin Yang, and Yifang Wen

Doc ID: 372309 Received 11 Jul 2019; Accepted 02 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: With the prevailing application of new materials and the higher requirements forthe quality and efficiency of production in the equipment manufacturing industry, traditionalassembly methods can hardly meet the needs of large-scale production, especially in the fieldof high-precision assembly. Robot assembly guided by visual perception has become the keyof the research in the field of engineering technology. It requires higher in the accuracy ofrobot visual perception and the control over force and position and so on. However, in 3Cassembly, most products are made of transparent materials such as glass. And because of thetransparency and specular reflection of the surface, 3D reconstruction of transparent objects isa very difficult problem in computer vision, in that the traditional visual perception methodscould not be accurate enough. The present research proposes a bionic active sensingalgorithm for 3D perception and reconstruction, and realizes high-precision 3D by applyingregistration algorithm. The purpose to solve the problems existing in the traditional visualperception method, such as difficulties in achieving active sensing, low accuracy of pointclouds registration and complex computation. The results of the experiments show that thepresent method is efficient and accurate in 3D reconstruction. It reduces the planarreconstruction error to 0.064 mm and the surface reconstruction error to 0.177 mm.

ABER performance investigation of LDPC-coded multihopparallel underwater wireless opticalcommunication system

Ang Li, Ping Wang, Weina Pang, Wenwen Chen, Sheng Liu, and Lixin Guo

Doc ID: 374039 Received 05 Aug 2019; Accepted 02 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: The average bit error rate (ABER) performance of a low-density parity-check (LDPC)-coded multi-hop parallelunderwater wireless optical communication (UWOC) system is investigated with the combined effects ofabsorption, scattering, the misalignment characterized by the beam spread function (BSF) and the oceanturbulence-induced fading modeled by log-normal distribution. With the max-min criterion as the best pathselection scheme, the cumulative distribution function (CDF) for identically and independently distributed (i.i.d)and non-identically and independently distributed (non-i.i.d) links are derived, respectively. Then,the analyticalABER expressions of binary phase shift keying (BPSK) and multiple phase shift keying (MPSK) subcarrier intensitymodulation (SIM) schemes are deduced with the help of the Gauss-Laguerre quadrature rule, and they are alsoconfirmed by Monte Carlo (MC) simulation. In addition, LDPC codes are applied in the simulation to improve thesystem performance.The results show that the combined degrading effects are mainly limited by the link length,especially under coastal ocean condition. And the multi-hop parallel transmission demonstrates good ABERperformance and can expand the communication range in ocean. Furthermore, LDPC codes can significantlyimprove the ABER performance of UWOC system, and the coding gain is strongly affected by channel conditions andthe corresponding parameters of LDPC codes. This work is beneficial for the UWOC system design.

Time-resolved visualization of high-repetitionultrashort pulse laser ablation

Sebastian Kraft, Jörg Schille, Stefan Mauersberger, Lutz Schneider, and Udo Löschner

Doc ID: 376497 Received 29 Aug 2019; Accepted 02 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: A pump-probe setup including a Robert cell type delaystage is calculated and build in the presented study.The goal is to visualize laser beam material interactionsupon highly-repetitive ultrashort pulse irradiations byshadowgraph imaging that makes a valuable contributionto clarify the occurring interaction phenomenain this field. Ultrashort laser pulses (l = 1030 nm;tH = 400 fs) are irradiated onto a bright-rolled stainlesssteel metal plate (AISI 316). The high-speed shadowgraphsequences are captured for the time-resolvedimaging of plasma and shock wave evolution duringmaterial ablation. The captured time frame ranges fromthe time just before the next pulse irradiates the interactionzone until 2 μs after pulse irradiation. The first partof the experimental study features with shock wave dynamicsand the evolution of the laser plasma/ablationplume as induced upon single pulse irradiations. It isshown, the expansion velocity of the shock wave decreasesfrom 10 km/s shortly after pulse irradiation to6.1 km/s at the time 41 ns after pulse irradiation. Thesecond part deals with laser pulse trains by irradiatingup to 10 pulses at 500 kHz pulse repetition frequency tothe substrate. For increasing pulse numbers, the shadowgraphsshow a steadily increase in height and widthof the laser plasma/ablation plume that were measuredof 2.4mm in height and 1.2mm in width after the tenthpulse.

Full-field analysis of wavefront Errors in pointdiffraction interferometer with misaligned GaussianIncidence

Fen Gao, THOMAS O’DONOGHUE, and Wei Wang

Doc ID: 378295 Received 19 Sep 2019; Accepted 02 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: The precision and accuracy of profile measurement achieved by a point diffraction interferometer (PDI) isdetermined by a spherical diffraction reference wavefront, whose quality is mainly controlled by pinhole’salignment. In consideration of a Gaussian beam incidence, different diffraction wavefront errors stemming frommisalignment of pinhole including lateral shift, defocus and tilt are analyzed with the help of a proposed systematicmodel and a new evaluation criterion established under spherical coordinates. The full-field distributions ofvarious diffraction wavefront errors are obtained through simulation. The predicted accuracy of an actual PDImakes a good agreement with the experiment results. The achieved results will be benefit to the accuracyevaluation of a PDI before and after its design.

A void-free bonding for large slab laser crystal

LIN Yan Yong, Hongwei Gao, Zhong-zheng Chen, JIA-LIN XU, Yuan Lei, Junwei Zuo, YI-TING XU, YA-DING GUO, BAO-SHAN WANG, JIAN XU, Bo Yong, qinjun peng, and Xu Zuyan

Doc ID: 378384 Received 24 Sep 2019; Accepted 02 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: A void-free bonding technique was demonstrated for a large slab Nd: YAG crystal with a bonding surface dimensionof ~160 mm × 70 mm. By using the novel fluxless oxide layer removed technology, the indium oxide barrier problem wasresolved. With the help of Electrochemical Polished (EP) indium solder and Plasma Cleaned (EP) heat sink, the solderability ofthe indium was enhanced, particularly, the contact angle of the solder was improved from 51 ° to 31 °. With the largest bondingsize slab, a single slab laser created a maximum output power of 7.3 kW under an absorbed pump power of 12.8 kW,corresponding to an optical to optical efficiency of 57 % and a slope conversion of 67.8%. By detecting the wavefront of theinterferometer before and after bonding, the RMS of wavefront was 0.192λ and 0.434λ (λ= 633nm), respectively. To thebest of our knowledge, this is the largest voids free bonding size for a laser slab and the highest output power achieved from asingle slab crystal laser oscillator.

A luminance calculation method accounting formesopic vision and fog penetration ability

li qin, xuhua SHI, and Arturo Leon

Doc ID: 379163 Received 30 Sep 2019; Accepted 02 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: A new luminance calculation method that accounts formesopic vision and fog penetration ability is presented,which aims to select the suitable light source for streetlighting. The method is obtained using the mesopicluminance calculation method and the transmittancecalculation method at each individual wavelength.Additionally, the new method was evaluated using sixLED light sources between 3500 and 6000K. Overall, thecalculation results indicate that suitable LEDs’ CCTdecreases with an increase of luminance for lowtransmittance rates. However, for high transmittancerates, high CCT LED lamps are the most suitable for streetlighting. The recommended CCT of LED light sources forstreet lighting under different visibility and luminanceconditions is presented.

Simple and effective tool for estimating treetrunk diameters and tree speciesclassification

Kenta Itakura and Fumiki Hosoi

Doc ID: 379196 Received 30 Sep 2019; Accepted 02 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: Tree trunk diameter and tree species are two of the most important parameters inanalyzing trees in urban areas and forests. Conventionally, diameters have been measuredmanually and the species were determined by sight. An automated tool for these assessmentswas developed. Tree trunks are automatically detected from captured stereo images. Then,tree trunk diameters are estimated, and the species are determined. The developed GUI(Graphical User Interface) tool enables fast and accurate estimation even while walking,which reduces the time spent in measuring trees.

An accurate angle estimation based onmoment for multi-rotation computationimaging

Qin Zuo, Yong Geng, Cheng Shen, Jiubin Tan, Shutian Liu, and Zhengjun Liu

Doc ID: 379231 Received 01 Oct 2019; Accepted 02 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: In a multi-rotation computation imaging system (MRCI), the fidelity ofreconstructed result is limited by the accuracy of estimated rotation angles. Here, an accurateangle detection method by using image moment was proposed to estimate angles ofdiffraction images. The second moment of a digital image is adopted as the rotational inertiain order to estimate angles of diffraction images. Compared with the previous ones based onRadon/Hough transform, it is higher accuracy and simultaneously time-saving, which isverified both in simulation and experiment. The angle error of moment method is narroweddown within 0.1 degree, even less and it also can perform well in sample-diversity or slightlyout of focus.

Nonlinear optical absorption properties ofzirconium selenide in generating dark solitonand dark-bright soliton pairs

yue zheng, Mengxiao wang, Rui zhao, Huanian Zhang, Danhua Liu, and Degnwang Li

DOI: 10.1364/AO.377776 Received 02 Oct 2019; Accepted 02 Dec 2019; Posted 05 Dec 2019  View: PDF

Abstract: Our work reports the preparation of zirconium selenide (ZrSe2)-polyvinyl alcohol(PVA) film type saturable absorber (SA) and its nonlinear absorption performance inobtaining dark soliton and dark-bright soliton pairs in Er-doped fiber (EDF) laser for the firsttime. The saturation intensity and modulation depth of the ZrSe2-PVA SA were ~12.72MW/cm2 and 2.3 %, respectively. Due to the modulation of the SA, under a pump power of525.2 mW, stable dark soliton operation with an average output power of 9.75 mW, a pulserepetition frequency of 20.84 MHz, a pulse width of 3.85 ns was attained successfully. Byadjusting the state of the polarization controllers (PCs), dark-bright soliton pairs were alsoobserved. To our knowledge, this was the first demonstration focusing on the nonlinearoptical absorption applications of ZrSe2 in obtaining dark soliton and dark-bright solitonpairs. Our results show that ZrSe2 is a good two-dimensional (2D) SA material for acting asultrafast optical devices due to its suitable nonlinear optical absorption properties.

An Evaluation Method for Optical Feedback Factorand Linewidth Enhancement Factor using PhaseDiscontinuities in Self-mixing Interferometry Signals

Chol-Yong Ri, Chol-Su Kim, Guk-Chol Ri, Jong-Chol Kang, Chol-Min Pak, and Jin-Myong O

Doc ID: 378283 Received 25 Sep 2019; Accepted 01 Dec 2019; Posted 03 Dec 2019  View: PDF

Abstract: Self-mixing interferometry (SMI) is a reliable method which has been applied to measuring displacements,absolute distances and velocities of remote targets. Evaluating the optical feedback factor C and the linewidthenhancement factor α is a vital step in calculating laser diode (LD) parameters and in processing SMI signals usingphase unwrapping. This paper proposes an evaluation method for the optical feedback factor and the linewidthenhancement factor of arbitrary waveforms by investigating the slopes of phase discontinuity distribution in theoptical feedback regime of 1C. First of all, the effects that the slope of phase discontinuity distribution has on theprediction of the optical feedback factor and the linewidth enhancement factor are clarified. Next, an algorithm isproposed to evaluate the optical feedback factor and the linewidth enhancement factor using the slope variation ofphase discontinuity distribution along with a method to select discontinuities in order to improve measurementaccuracy using cumulative effect of discontinuity distribution. The proposed method is verified throughsimulations as well as experiments with a low-cost semiconductor laser.

Passive optical device for nystagmuscorrection & ophthalmic resolutionenhancement

Dana Gotthilf Nezri, Alexander Zlotnik, and Zeev Zalevsky

Doc ID: 378109 Received 24 Sep 2019; Accepted 30 Nov 2019; Posted 02 Dec 2019  View: PDF

Abstract: In this research we present a novel device that solves the reduced visual acuity caused byinvoluntary movements of the retina in nystagmus. The proposed solution is composed of acontact lens, which moves together with the eyeball, and an ophthalmic lens (spectacles).Our work has three parts: numerical simulation of the proposed solution, an experimentaloptical bench procedure and a clinical experiment, with non-nystagmus subjects, in which wemimicked the uncontrolled eye movements in nystagmus. In the numerical and experimentalbench sections of this study we show that the proposed optics produces a clear and stableimage on a screen. In the clinical study, subjects with the device felt only small movements ofthe image when moved their eyes across the field of view. They described a magnificationresulting in narrowing the field of view, therefor had to move their head to see the space of theroom. This follows the theoretical expectation for the proposed concept.Thus, the proposed device may help nystagmus subjects fixate the image on the center ofthe retina, and thus enable improved visual acuity. The device may be used in young childrensuffering from nystagmus to prevent amblyopia.

Design and application of portable luminometer for bioluminescence detection

Youngkee Jung, Claudia Coronel-Aguilera, Iyll-joon Doh, Hyun Jung Min, Trevor Lim, Bruce Applegate, and Euiwon Bae

Doc ID: 378936 Received 27 Sep 2019; Accepted 30 Nov 2019; Posted 02 Dec 2019  View: PDF

Abstract: The silicon photomultiplier (SiPM) for low light detection has many advantages when compared to existing photon counting detectors, such as high sensitivity, low cost, robustness, and compact hardware. To facilitate the use of SiPM as a portable, field deployable device, an electrical circuit was designed consisting of an amplifier, comparator, and micro controller. In addition, a 3-D printing was used to create a portable cradle for housing the SiPM. To evaluate its detection ability, a laser experiment and bioluminescent experiments, including: Pseudomonas fluorescens M3A detection, E. coli O157:H7 PhiV10nluc lysogen detection, and a luminescence-based detection of E. coli O157:H7 in ground meat using the engineered luminescent based reporter phage PhiV10nluc, were conducted. In the same experimental setting, our previously developed smartphone based luminometer called Bioluminescent-based Analyte Quantitation by Smartphone (BAQS) and a conventional photomultiplier tube (PMT) based benchtop luminometer were used to compare detection levels and applicability for supporting luminescent phage-based pathogen detection. Results showed that the SiPM provides better performance in terms of time to detection and SNR and could be used as the light detection component of the PhiV10nluc phage-based detection format.

Comprehensive Defect Detection Method forSmall-sized Curved Optical Lens

Jinda Pan, ning yan, Linlin Zhu, Xiaodong Zhang, and Fengzhou Fang

Doc ID: 380414 Received 15 Oct 2019; Accepted 29 Nov 2019; Posted 02 Dec 2019  View: PDF

Abstract: During quality-assurance procedures in mass production of small-sized curvedoptical lenses, fine defects are usually detected via manual observation, which is notrecommended owing to associated drawbacks of high error rate, low efficiency, and nonamenabilityto quantitative analysis. To address this concern, this paper presents acomprehensive defect-detection system based on transmitted fringe deflectometry, dark-fieldillumination, and light transmission. Experimental results obtained in this study reveal that theproposed method demonstrates efficient and accurate detection of several micro defectsoccurring in small-sized optical lenses, thereby providing valuable insights with regard tooptimization of parameters concerning mass production of optical lenses. The proposedsystem can be applied to the actual mass production of small-sized curved optical lenses.

Digital halftoning method with simultaneouslyoptimized perceptual image quality and drive currentfor multi-tonal electrophoretic displays

Zong Qin, Hsin-I Wang, Zi-Yu Chen, Chunho Chen, Pei-Lin Tien, Mei-Hwa Liu, Shu-Cheng Liu, Chi-Mao Hung, Chuang-Chuang Tsai, and Yi-Pai Huang

Doc ID: 377635 Received 11 Sep 2019; Accepted 29 Nov 2019; Posted 03 Dec 2019  View: PDF

Abstract: While using digital halftoning to achieve multi-tones in a 1-bit electrophoretic display (EPD), e.g., a 3-pigmentchromatic EPD, the drive current is significantly increased because of frequently reversed pixel values. Aimed atthis issue, this study first establishes a model that can accurately predict the drive current from image content.Next, based on the direct binary search method, a new halftoning method is proposed by constructing a combinedmerit function that incorporates both the perceptual image quality and the drive current. As a result, inexperiments using a 13.5-inch 3-pigment EPD and several test images, compared with the well-developed errordiffusionmethod, the proposed method produces little image quality degradation, while the drive current increasewith respect to the minimum current of the EPD is reduced from 71.8 to 33.0 mA, for a significant reduction of54.0%.

Optical Method to Characterize and AssessSetting Evolution of Cement Pastes

Juan J. Soto-Bernal, Gloria Vazquez, Rosario Gonzalez-Mota, Iliana Rosales-Candelas, JOSE ORTIZ-LOZANO, and Hector De Leon-Martinez

Doc ID: 380930 Received 12 Nov 2019; Accepted 29 Nov 2019; Posted 03 Dec 2019  View: PDF

Abstract: In this work, a nondestructive and noninvasive technique based on laser technologyand the use of Kubelka-Munk model to calculate the dynamic behavior of the cement pastefrom the diffuse reflection properties of both cement components and hydration products, isproposed. Also, the Powers-Brunauer model is used to explain this behavior during the firstnine hours of the hydration process. This method allows to obtain the initial and final cementsetting times from the diffuse reflection measurements.

High-power mode-locked thulium-doped fiber laserwith tungsten ditelluride as saturable absorber

Zhijian Zheng, Jintao Wang, Jinde Yin, DEQIN OUYANG, Xikui Ren, Peiguang Yan, Jinzhang Wang, Jihong Pei, Qitao Lv, and Shuangchen Ruan

Doc ID: 381235 Received 22 Oct 2019; Accepted 28 Nov 2019; Posted 02 Dec 2019  View: PDF

Abstract: A passively mode-locked thulium-doped fiber laser using a tungsten ditelluride saturable absorber (WTe2-SA) isdemonstrated in this research. High-power mode-locked pulses with an average output power of 108.1 mW wereachieved by incorporating the WTe2-SA into a thulium-doped fiber oscillator. To the best of our knowledge, this isthe highest average power from a WTe2-SA-based fiber laser. We further amplified the output power to 5.60 W withan all-fiber thulium-doped double-cladding fiber amplifier (TDFA). Our result indicates that WTe2-SA could be anexcellent candidate for a high-power fiber laser system.

Optical color image encryption based onchaotic fingerprint phase mask in variousdomains and comparative analysis

yonggang su, Wenjun Xu, Jie Zhao, Lei Chen, and Xiaoyan Tian

Doc ID: 379723 Received 03 Oct 2019; Accepted 28 Nov 2019; Posted 02 Dec 2019  View: PDF

Abstract: Random phase masks are served as secret keys and play a vital role in doublerandom phase encoding architecture. In this paper, we propose a new method to generate therandom phase masks using the chaotic Henon map and fingerprint. We then extend thegenerated chaotic fingerprint phase masks to Fourier transform domain, fractional Fouriertransform domain, Fresnel transform domain and Gyrator transform domain to encrypt colorimages. In these four color image encryption schemes, the fingerprint and chaotic parametersare served as secret keys directly, and the chaotic fingerprint phase masks are just used asinterim variables and functions. If the sender and receiver share the fingerprint, only thechaotic parameters are needed to transmit over the network. Thus the management andtransmission of the secret keys in these four encryption schemes are convenient. In addition,the fingerprint keys which are strongly linked with the sender or receiver can enhance thesecurity of these four encryption schemes greatly. Extensive numerical simulations have beencarried out to verify the feasibility, security and robustness of these four color imageencryption schemes.

Effect of an Optical Coating on In-Band and Out-of-BandTransmitted and Reflected Wavefront ErrorMeasurements

Graham Carlow, Brian Sullivan, Claude Montcalm, and alexander miles

Doc ID: 378163 Received 17 Sep 2019; Accepted 28 Nov 2019; Posted 02 Dec 2019  View: PDF

Abstract: The Wavefront Error (WE) of a surface with an optical coating (‘filter’) is ideally measured at the in-bandwavelength of the filter. However, quite often this is not possible, requiring that the filter be measured at an out-ofbandwavelength (typically 633 nm), assuming that the filter transmits (for Transmitted WE or TWE) or reflects (forReflected WE or RWE) at this wavelength. This out-of-band TWE/RWE is generally assumed to provide a goodestimation of the desired in-band TWE/RWE. It will be shown in this paper that this is not the case for a large classof filters (i.e., bandpass) where the Group Delay (GD) is significantly different at the in-band and out-of-bandwavelengths and where the optical filter exhibits a thickness non-uniformity across the surface. A theoreticalexplanation will be given along with an approach to predict the in-band TWE/RWE based on the coating nonuniformity,the measured out-of-band TWE/RWE and the theoretical properties of the optical filter at the in-bandand out-of-band wavelengths. A reasonable agreement between theory and measurement was demonstrated bymeasuring the TWE of a 11 nm wide bandpass filter (centered at 1048 nm) at both in-band (λ=1048 nm) and out-ofband(λ=625 nm) wavelengths. A similar treatment is provided for RWE.

Large-scale range diffraction gratingdisplacement sensor based on polarizationphase-shifting

Mengwei Li, zhouxin liang, Rui Zhang, Qiannan Wu, Chenguang Xin, li jin, yang xie, and HONGBO ZHAO

Doc ID: 376480 Received 13 Sep 2019; Accepted 28 Nov 2019; Posted 02 Dec 2019  View: PDF

Abstract: A novel method is proposed and demonstrated to improve diffraction gratingdisplacement sensor to achieve nanometer-level resolution and extended range of operationsimultaneously. The method exploits polarization phase-shifting optical path to extract twosinusoidal signals with quadrature phase shift, the interpolation circuit is applied tononlinearly convert two sinusoidal signals into a standard incremental AB quadrature digitalsignal, implementing extended operation range with the magnitude of laser coherence length.This work enables displacement measurement operated at large-scale range, and provides asignificant guide for the design of high performance micro-displacement sensor.

Lossy wavefront sensing and correction of distortedlaser beams

Chensheng Wu, Jonathan Ko, and Christopher Davis

Doc ID: 377515 Received 10 Sep 2019; Accepted 28 Nov 2019; Posted 02 Dec 2019  View: PDF

Abstract: The art of rectifying a laser beam carrying amplitude and phase distortions has been demonstratedthrough several competing thoughts. Both wavefront sensor and wavefront senor-less approaches showthat the closed-loop correction of a laser beam can be done by exploiting high resolution sampling ofthe beam distortion in its spatial or time domains, respectively. Moreover, machine learning (ML) basedwavefront sensing emerges recently, which uses training data on an arbitrary sensing architecture to mapobserved data to reasonable wavefront reconstructions. This offers additional options to beam correctionand optical signal decoding in atmospheric or underwater propagation. Ideally, wavefront sensing canbe achieved through any resolution in spatial samples, provided that more frequent sampling in the timedomain can be achieved for reduced number of spatial samples. However, such trade-offs haven’t beencomprehensively studied and demonstrated experimentally. We present a fundamental study of lossywavefront sensing that reduces the number of effective spatial samples to the number of actuators in a deformablemirror (DM) for a balanced performance of dynamic wavefront corrections. As a result, we showthat lossy wavefront sensing can both simplify the design of wavefront sensors and remain effective forbeam correction. In application, such concept provides ultimate freedom of hardware choices from sensorto sensor-less approaches in wavefront reconstruction, which is beneficial to the frontier study in freespace optical communication, lidar and directed energy.

Hyperspectral polarimetric imaging of the watersurface and retrieval of water optical parametersfrom multi-angular polarimetric data

Alexander Gilerson, Carlos Carrizo, Amir Ibrahim, Robert Foster, Tristan Harmel, Ahmed El-Habashi, Zhongping Lee, Xiaolong Yu, Sherwin Ladner, and michael ondrusek

Doc ID: 380105 Received 10 Oct 2019; Accepted 27 Nov 2019; Posted 02 Dec 2019  View: PDF

Abstract: Total and polarized radiances from above the ocean surface are measured by astate-of-the-art snapshot hyperspectral imager. A computer-controlled filter wheel is installedin front of the imager allowing for recording of division-of-time Stokes vector images fromthe ocean surface. This system, to the best of our knowledge, for the first time provided acapability of hyperspectral polarimetric multi-angular measurements of radiances from abovethe water surface. Several sets of measurements used in the analysis were acquired fromocean platforms and from shipborne observations. Measurements made by the imager arecompared with simulations using a vector radiative transfer (VRT) code showing reasonableagreement. Analysis of pixel-to-pixel variability of the total and polarized above waterradiance for the viewing angles of 20°-60° in different wind conditions enable the estimationof uncertainties in measurements of these radiances in polarized mode for the spectral rangeof 450 – 750 nm, thus setting requirements for the quality of polarized measurements. It isshown that there is a noticeable increase of above water DoLP as a function of the viewingangle, which is due both to the larger DoLP of the light from the water body and the lightreflected from the ocean surface. Results of measurements and VRT simulations are appliedfor the multi-angular retrieval of the ratio of beam attenuation coefficient (ctot) to absorptioncoefficient (atot) in addition to the other parameters like absorption and backscatteringcoefficients retrieved from traditional un-polarized methods.

Fabrication of Graphene Oxide Coated Quartz FilterPaper for Enhanced Adsorption of Particulate Matter

Khan Alam, Nadia Khan, Humaira Seema, Ayesha Samreen, and bahadar zeb

Doc ID: 375181 Received 13 Aug 2019; Accepted 27 Nov 2019; Posted 27 Nov 2019  View: PDF

Abstract: Airborne particulate matter has become an emerging issue globally due to environmental degradation and healthrisk it causes. Volatilization of weakly adsorbed particles onto quartz filter paper limits its performance. Theadsorption of particulate matter (PM10) onto quartz filter paper coated with different concentration of grapheneoxide was investigated to enhance the adsorption potential. Hummer’s method was adopted to synthesize GrapheneOxide (GO). Quartz filter (QF) papers were coated with different concentrations of GO using spin coating technique tooptimize the result. The morphology and microstructure of Graphene Oxide coated Quartz Filter (GOQF) paper werecharacterized by various experimental technique like XRD, FTIR, EDX, and SEM. Graphene oxide showed considerableaffinity to aerosol particles for 5mg/ml weight GO coated QF, whereas adsorption of the coated samples before andafter was significantly reduced. The high affinity to aerosol particles was due to dominated π-π interactions and thegrooved regions formed on graphene oxide layer. It was considered that the high surface to volume ratio of grapheneoxide coated on quartz filter paper improves the adsorptive property of the QF and consequently enhances theperformance of the filter paper.

Diagnosis of electrically active defects in CH3NH3PbI3perovskite solar cells via admittance spectroscopymeasurements

Juanjuan Xue, Xiaobo Hu, yixin guo, Guoen Weng, Jinchun Jiang, Shaoqiang Chen, Ziqiang Zhu, and Junhao Chu

Doc ID: 382486 Received 05 Nov 2019; Accepted 27 Nov 2019; Posted 27 Nov 2019  View: PDF

Abstract: The defect properties of CH3NH3PbI3 solar cells with efficiencies ranging from 7.70% to 12.51% wereinvestigated using admittance spectroscopy measurements. Trap levels of the same kind with activationenergies varied in the range of 0.16~0. eV above the valence band were found for different samples andidentified as an interface-type defect. Moreover, the defect parameters, including the capture cross-section ofholes, capture lifetime of holes, and defect density, were extracted and their relationships with the cellefficiencies were investigated. The results indicated that, compared with other parameters, defect density isa critical factor for CH3NH3PbI3 solar cell performance.

The complex refractive index of volcanic ash aerosol inthe infrared, visible and ultraviolet

Alexandre Deguine, Denis Petitprez, Lieven Clarisse, Snaevarr Gudmundsson, Valeria Outes, Gustavo Villarosa, and Hervé Herbin

Doc ID: 378045 Received 18 Sep 2019; Accepted 26 Nov 2019; Posted 26 Nov 2019  View: PDF

Abstract: Very fine silicate-rich volcanic ash, generated by explosive volcanic eruptions, can efficiently be traceddownwind with infrared satellite sounders. Their measurements can also be used to derive physicalparameters, such as optical depths and effective radii. However, one of the key requirements for accurateretrievals is a good knowledge of the complex refractive index (CRI) of the ash under investigation. Inthe past, the vast majority of the studies used the CRIs from Pollack et al. (1973), which are based onmeasurements of thin slices of volcanic rock, and therefore are not representative for airborne volcanic ashparticles. Here, we report measurements of the CRI of volcanic ash in suspension, generated from samplescollected from recent high-impact eruptions in Chile (Puyehue-Cordón Caulle, Calbuco and Chaitén),Iceland (Eyjafjallajökull and Grímsvötn) and Italy (Etna). The samples cover a wide range of SiO2 content(46 to 76%) as confirmed by an X-ray fluorescence analysis. In the experimental setup, volcanic ash wassuspended in nitrogen through mechanical agitation. Extinction spectra were recorded in the infrared,visible and ultraviolet spectral regions. The particle size distribution within the airflow was recorded aswell. An iterative algorithm allowed to obtain fully consistent CRIs for the six samples, compatible withthe observed extinction spectra and the Kramers-König relations. While a good agreement is found withother recently reported CRIs in the UV/Vis, larger differences are found in the longwave infrared spectralregion.

High precision micro-displacement sensorbased on zeroth-order diffraction usingsingle-layer optical grating

HONGBO ZHAO, Mengwei Li, Rui Zhang, Zhi WANG, yang xie, Chenguang Xin, li jin, and zhouxin liang

Doc ID: 378151 Received 18 Sep 2019; Accepted 26 Nov 2019; Posted 26 Nov 2019  View: PDF

Abstract: This paper reported a high-precision micro-displacement sensor based on zerothorderdiffraction of single-layer optical grating. Laser grating interference occurs when part ofthe laser is reflected diffraction by the grating and another part is vertically reflected back bya mirror and diffracted again by the grating, thus generating optical interferometric detection.For the purpose of obtaining the optimal contrast of the optical interferometric detection, theduty cycle of the grating and the orders of diffraction were optimized by the diffraction scalartheory. The micro-displacement sensor demonstrates a sensitivity of 0.40%/nm, a resolutionof 0.6 nm, and a full scale range up to 100 μm. This work enables a high performancedisplacement sensor, and provides a theoretical and technical basis for the design ofdisplacement sensor with ultra-compact structure.

Light scattering characterization of single layernanoporous SiO2 antireflection coating in VIS

Yusuf Sekman, Nadja Felde, Lilit Ghazaryan, Adriana Szeghalmi, and Sven Schröder

Doc ID: 378168 Received 17 Sep 2019; Accepted 26 Nov 2019; Posted 26 Nov 2019  View: PDF

Abstract: Antireflective coatings are widely applied on transparent optical components to reduce reflections at surfaces.Nanoporous silica (NP SiO2) thin films with tailored refractive index properties are used as singlelayer antireflective coatings providing nearly zero reflectivity. In this work, light scattering properties ofnanoporous silica single layer antireflective coatings are investigated in order to determine their opticalquality by means of total scattering and detailed roughness analysis. Scattering and roughness characterizationof the samples coated with different film thicknesses were realized to distinguish the influences ofnanopores and surface roughness on scattering losses in the visible spectral range. No significant correlationof scattering losses with the film thickness is found, showing negligible influence of the nanopores tothe overall scattering properties compared to the dominating effect of interface roughness. Moreover, thescattering losses from coated fused silica glass were observed as low as 20 ppm (0.002%). It is confirmedthat NP SiO2 single layer antireflective coatings are suitable to be used in optics demanding extremelylow scattering characteristics.

Comparison of Continuous Wave versus PicosecondSRS and the Resonance SRS effect

Pavel Shumyatsky, Lingyan Shi, Laura Sordillo, yury budansky, and Robert Alfano

Doc ID: 379037 Received 26 Sep 2019; Accepted 25 Nov 2019; Posted 26 Nov 2019  View: PDF

Abstract: Stimulated Raman scattering (SRS) is a powerful optical technique for probing the vibrational states ofmolecules in biological tissues and provides greater signal intensities than when using spontaneous Ramanscattering. In this study, we examined the use of continuous wave (cw) and picosecond (ps) laserexcitations to generate SRS signals in pure methanol, a carotene-methanol solution, acetone and braintissue samples. The cw-SRS system, which utilized two cw lasers, produced better S/N than the conventionalps-SRS system, suggesting that the cw-SRS system is an efficient and cost-effective approachfor studying SRS in complex systems like the brain. The cw-SRS approach will reduce the size of SRSsystem, allowing for SRG/L microscopy. In addition, we showed that there exist a resonance stimulatedRaman (RSRS) effect from the carotene-methanol solution and brain tissue samples using cw laser excitations.The Resonance Stimulated Raman effect will further improve the S/N and may be utilized as anenhanced, label-free SRS microscopic tool for the study of biological tissues.

Bayesian Reconstruction Method forUnderwater 3D Range-Gated ImagingEnhancement

Xiaojun Yin, Hu Cheng, Kecheng Yang, and Xia Min

Doc ID: 367745 Received 17 May 2019; Accepted 25 Nov 2019; Posted 26 Nov 2019  View: PDF

Abstract: In this paper we investigate a systematic improvement for 3D range-gated imagingin scattering environments. Drawbacks including absorption, ambient light and scatteringeffect are studied. The former two are compensated through parameter estimation andpreprocessing. With regard to the scattering effect, we propose a new 3D reconfigurationalgorithm using a Bayesian approach that incorporates spatial constraints through a GeneralGaussian Markov Random Field (GGMRF). The model takes both scene depth and albedointo account, which provides more informative and accurate restoration result. Hyperparametersfor the statistical mechanism are evaluated adaptively in the procedure and anICM optimization algorithm is employed to find an optimum solution. The performance ofour method was assessed via conducting various experiments and the results also indicate thatthe proposed method is helpful for restoring the 2D image of scene with improved visibility.

Depixelation and Enhancement of Fiber BundleImages by Bundle Rotation

Carlos Renteria, Javier I. Suárez, Alyssa Licudine, and Stephen Boppart

Doc ID: 377181 Received 05 Sep 2019; Accepted 25 Nov 2019; Posted 26 Nov 2019  View: PDF

Abstract: Fiber bundles have become widely adopted for use in endoscopy, live-organism imaging, and other imagingapplications. An inherent consequence of imaging with these bundles is the introduction of a honeycomb-likeartifact that arises from the inter-fiber spacing, which obscures features of objects in the image. This artifactsubsequently limits applicability and can make interpretation of the image-based data difficult. This work presentsa method to reduce this artifact by on-axis rotation of the fiber bundle. Fiber bundle images were first low-pass andmedian filtered to improve image quality. Consecutive filtered images with rotated samples were then coregisteredand averaged to generate a final, reconstructed image. The results demonstrate removal of the artifacts,in addition to increased signal contrast and signal-to-noise ratio. This approach combines digital filtering andspatial resampling to reconstruct higher-quality images, enhancing the utility of images acquired using fiberbundles.

Efficient Computation of 2D Point-Spread Functionsfor Diffractive Lenses

Süleyman Ayazgök and Figen Oktem

Doc ID: 374299 Received 02 Aug 2019; Accepted 25 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: Diffractive lenses, such as Fresnel zone plates, photon sieves, and their modified versions, have beenof significant recent interest in high-resolution imaging applications. As the advent of diffractive lenssystems with different configurations expands, the fast and accurate simulation of these systems becomescrucial for both the design and image reconstruction tasks. Here we present a fast and accurate method forcomputing the 2D point-spread function (PSF) of an arbitrary diffractive lens. The method is based on therecently derived closed-form mathematical formula for the PSF and the transfer function of a diffractivelens. In the method, first, the samples of the transfer function are computed using the transmittance functionof the diffractive lens, and then the inverse Fourier transform of this transfer function is computed toobtain the PSF. For accurate computation, the selection of the sampling parameters is handled with care,and simple selection rules are provided for this purpose. The developed method requires a single fastFourier transform (FFT), and, therefore, has little computational complexity. Moreover, it is also applicableto any diffractive lens configuration with arbitrary shaped structures and modulation. As a result,this fast and accurate PSF computation method enables efficient simulation, analysis, and developmentof diffractive lens systems under both focused and defocused settings.

Geometric Calibration Method Based on Two-dimensionalTurntable for Directional Polarimetric Camera

Chan Huang, Binghuan Meng, YuYang Chang, Feinan Chen, Miaomiao zhang, Lin Han, guangfeng xiang, Bihai Tu, and Hong Jin

Doc ID: 378414 Received 20 Sep 2019; Accepted 25 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: The Directional Polarimetric Camera is a polarization sensor with the character of ultra-wide-angle and low-distortion imaging.Geometric calibration is usually the first essential step before remote sensing satellites launched. In this paper, a geometriccalibration method based on a two-dimensional turntable and the rotation matrix with high precision, simple operation and wideapplication range is proposed for the Directional Polarimetric Camera. Instead of precisely adjusting the position of the sensor onthe turntable, the method effectively eliminates the errors caused by the mechanical axis of the turntable and the optical axis of thesensor not being adjusted to the same direction through the rotation transformation of the coordinate system. The geometriccalibration experiments of Directional Polarimetric Camera were carried out with the method of Chen and the proposed method.The experimental results showed the calibration residual of the proposed method was less than 0.1 pixel while the method of Chenwas 0.3 pixel. The mean reprojection error and root mean squared error of the proposed method were reduced to 0.06352 pixel and0.06961 pixel respectively. The geometric calibration parameters obtained by the proposed method were used for geometriccorrection of the in-orbit images of DPC, the results also prove the effectiveness and superiority of the proposed method.

A miniature high-speed, low-pulse energypicosecond Raman spectrometer foridentification of minerals and organics inplanetary science

Jordana Blacksberg, Erik Alerstam, Corey Cochrane, Yuki Maruyama, and Jack Farmer

Doc ID: 373843 Received 26 Jul 2019; Accepted 25 Nov 2019; Posted 03 Dec 2019  View: PDF

Abstract: The motivation behind time-resolved Raman spectroscopy for planetary surfaceexploration is (1) to provide comprehensive identification of minerals (nearly all rockformingminerals and weathering products) and many organics of prime importance includingfossilized carbonaceous materials; (2) to do so ensuring that it is possible to characterize eventhe most sensitive materials that would be altered by current state of the art pulsed lasers (e.g.dark minerals, organics). These goals are accomplished here using a lightweight, high speed(MHz) pulsed (< 100 ps) Raman spectrometer based on a High-speed MicroChip (HMC)laser combined with a Single Photon Avalanche Diode (SPAD) detector array. Using a Marsanalogsample set and an automated grid sampling technique, we demonstrate consistentidentification of major minerals and kerogen detection at ~≥1% by volume, without lossestypically associated with the two biggest problems: fluorescence interference and sampledamage. Despite improvements, we find that time-resolved Raman spectroscopy is stilllimited by the availability of a suitable laser and detector. As technology advances and suchdevices become available, we expect that this technique will hold an important place inRaman spectroscopy for both commercial and planetary science applications. We alsodiscuss the utility of Raman point mapping for planetary science (e.g. in comparison to othercommon techniques like infrared reflectance spectroscopy) and conclude that the choice oftechnique must be planetary mission specific; one must consider whether incurring the time tomap single microscopic points is worthwhile, and how many points would be sufficient togain the required information to characterize the surface.

LED irradiance pattern at short distances

Ivan Moreno

Doc ID: 377614 Received 11 Sep 2019; Accepted 25 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: Many emerging light-emitting diode (LED) applications require short-distanceillumination. For that, we derive an exact formula of the illumination profile produced byLambertian LEDs, in which all parameters are fundamental constants. Moreover, we proposea general, simple but accurate mathematical model of the irradiance pattern, valid forLambertian and non-Lambertian LEDs at short distances. This model provides the irradianceprofile in function of both the LED-target distance and the coordinates of every point on theirradiated surface. The model is formulated in terms of simple sigmoid functions, in whichLED size and light flux are fundamental parameters. The accuracy of the irradiance patternmodel is tested both with theory and with experimental measurements.

Laser-Induced Breakdown Spectroscopy forRapid Accurate Analysis of Mg, Ca, and K inEdible Sea Salts

Hyang Kim, Van Ngo, Sandeep Kumar, Won Lee, Jeong Park, Song-Hee Han, Sang-Ho Nam, Kyung-Sik Ham, and Lee Hoon

Doc ID: 377656 Received 13 Sep 2019; Accepted 25 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: A compact laser-induced breakdown spectroscopy (LIBS) instrument and a simplesample preparation method were developed for rapid on-site analysis of Mg, Ca, and K inedible sea salt products. The LIBS instrument was assembled using a small diode-pumpedsolid-state laser and a handheld spectrometer. Aqueous solutions of salts were prepared andsampled by using pieces of filter papers. The dried filter paper was attached to the flat surfaceof silicon wafer and analyzed by LIBS. Calibration curves were obtained using binarymixtures of NaCl−MgSO4, NaCl−CaCl2, and NaCl−KCl, and used to estimate theconcentrations of Mg, Ca, and K in thirteen edible sea salt products. Matrix effects on theresults from LIBS were identified in comparison with those from inductively-coupled plasmaoptical emission spectroscopy. This indicates that the matrix of sea salt samples issignificantly different from that of the binary mixture standards. The sea salts with knownconcentrations of Mg, Ca, and K were employed to match the matrices of samples andstandards. This improved analysis accuracy remarkably. Furthermore, an alternative indirectmethod for estimating the concentration of K was suggested on the basis of the strongpositive correlations observed between the concentrations of Mg and K in the sea saltsamples.

Temperature Accuracy and Resolution Improvementfor Raman Distributed Fiber-optics Sensor by UsingRayleigh Noise Suppression Method

Baoqiang Yan, Li Jian, Mingjiang Zhang, Yang Xu, Tao Yu, Jianzhong Zhang, Lijun Qiao, and Tao Wang

Doc ID: 377967 Received 17 Sep 2019; Accepted 24 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: A novel Rayleigh noise suppression method is proposed to improve temperature accuracy and resolution forRaman distributed fiber-optics sensor. The proposed temperature demodulation method can eliminatetemperature measurement inaccuracy caused by Rayleigh noise. The experimental result indicates that thetemperature accuracy is optimized from 6.2 °C to 1.7 °C at the sensing distance of 9.1 km by using theproposed method, and the temperature resolution leading to about 1.5 °C improvement compared with thetradition demodulation method at the sensing distance of 10.0 km. The proposed method provides a robustand reliable high performance for long sensing ranges.

Short-range remote sensing of water qualityby a handheld fluorosensor system

Junchen Lu, Ye Yuan, Zheng Duan, Guangyu Zhao, and Sune Svanberg

Doc ID: 378287 Received 19 Sep 2019; Accepted 24 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: Laser-induced fluorescence (LIF) is a powerful measurement method fordetermining the concentration of organic pollutants as well as the amount of algae in water. Itcan be applied in remote sensing of natural waters and has the advantages of high speed andsensitivity. In this paper, we present a compact handheld fluorosensor system for waterquality assessment. The power of the technique is demonstrated in measurements at a riversystem in South China.

Wideband multiwavelength Brillouin fiber laser based on dual-mode AlGaInAs/InP microcavity lasers

Ji-Liang Wu, Yali Huang, Yue-De Yang, Jin-Long Xiao, Guanshi Qin, and Yong-Zhen Huang

Doc ID: 378672 Received 24 Sep 2019; Accepted 23 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: A multiwavelength Brillouin fiber laser (BFL) is demonstrated using a 1.55 µm AlGaInAs/InP microcavity laser as a seed source. The combination of a nonlinear fiber cavity and a feedback loop leads to multiwavelength generation with a channel spacing of double-Brillouin-frequency assisted by cavity-enhanced four-wave mixing (FWM). A dual-mode lasing square microcavity laser with a wavelength interval of 1.5 nm is applied as the pump source for the broadband multiwavelength generation. A wideband multiwavelength BFL covering from 1480 nm to 1600 nm is successfully generated at optimized pump power of 25 dBm and feedback power of -17.2 dBm. The power stability of 0.82 dB over 60 minutes duration of the multiwavelength BFL can satisfy the demands for optical fiber sensing and microwave photonic systems.

Bi-directional tuning of whispering gallery modes in asilica microbubble infiltrated with magnetic fluids

Yilun Liu, Hao Zhang, Miaosen Fan, Congzhou Liang, and Jie Lei

Doc ID: 379320 Received 01 Oct 2019; Accepted 23 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: Bi-directional tuning mechanism of whispering gallery modes (WGMs) in a capillary-based microbubblemicroresonator infiltrated with magnetic fluids (MFs) is investigated. Due to distinct refractive index responsesof MFs dependent on the applied magnetic field direction with respect to the capillary axis, the refractive index ofMFs shows different variation trends when external magnetic field is parallel or perpendicular to the capillaryaxis. Experimental results indicate that WGM resonance dips exhibit wavelength shift in inverse directions forthe above two cases, which is in accordance with our theoretical analysis on different refractive variationbehaviors of MFs. As the applied magnetic field is perpendicular or parallel to the capillary axis, the WGMresonance wavelength tuning sensitivities tend to be -15.01 pm/mT and 6.3 pm/mT, respectively. Our proposedWGM tuning scheme has several desirable advantages, including bi-directional tunability, high Q-factor, ease offabrication, and good compatibility with functional materials, which make it a promising candidate in the fieldof magnetic field vector sensing and magnetically manipulated micro-optic devices.

Attenuation Calibration Method Based on Sensitivity Correction in Raman Distributed Temperature System

Jianchun Xia, Li Xia, zhao yang, and Panli Huang

Doc ID: 373828 Received 26 Jul 2019; Accepted 23 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: A novel algorithm for attenuation calibration in distributed temperature sensors (DTS) based on Raman scattering is firstly presented and experimentally demonstrated. Numerical simulation is implemented to explore the signal distribution of Stokes and anti-Stokes lights along sensing fiber with the traditional DTS configuration. The proposed attenuation calibration method is to process the directly detected signal related to the temperature profile, and calculate the calibration coefficient to keep the linearity of temperature measurement and its uniformity along the whole fiber. The experimental results indicate that the attenuation issue of the signal along sensing fiber is solved simply and efficiently. Simultaneously, a good linearity of the temperature measurement is achieved and the sensitivity remains uniformity in the measuring range. The enhanced DTS system reduces the maximal error in temperature measurement from 18.01 °C to 1.56 °C along an approximate 10 km sensing fiber. The simplicity, validity and reliability of the proposed method make the DTS system a better candidate in practical applications without the extra requirement of the existed system configuration.

Dynamic phase measuring profilometry for Rigidobject based on Simulated Annealing

Mingyou Dai, Kuang Peng, Man Luo, Jiang Zhao, Wenfeng Wang, and Yiping Cao

Doc ID: 373267 Received 19 Jul 2019; Accepted 22 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: This paper presents a dynamic phase measurement profilometry (PMP) method based on the simulated annealingalgorithm. In dynamic PMP for rigid objects, pixel matching is an effective method to make pixel one-to-onecorresponding in each captured pattern. However, pixel matching by the global traversing algorithm takes up most ofthe time in the whole reconstructed process. For the purpose of optimizing pixel matching and enhance performancein dynamic PMP, the simulated annealing algorithm is introduced. By generating a random path based on thesimulated annealing algorithm, it is sufficient to locate the approximate area of the measured object. Then theaccurate position can be calculated combing with a partial traversing algorithm. The proposed method can reducepixel matching time by 63 percent and increase reconstructed efficiency by 58 percent. Simulations and experimentsprove feasibility and precision.

Linear variable optical attenuators (VOAs) withshaped-finger comb-drive actuators

Dooyoung Hah

Doc ID: 379942 Received 08 Oct 2019; Accepted 22 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: A design method is proposed for variable optical attenuators (VOAs), aiming atlinear attenuation-voltage characteristics, and verified by finite element analysis. Devices ofinterest are planar VOAs based on microelectromechanical systems (MEMS) technology, eitherwith a knife-edge shutter or with a reflector. The proposed method calculates the shape of thefingers of the comb-drive actuators which are used to move the optical component (shutter orreflector) to change the attenuation level. The calculation, in effect, tantamounts to solving adifferential equation that encompasses optical model of the device, electromechanical behaviourof the actuators, and the objective of the design, i.e. linear attenuation-voltage characteristics.The design method is almost all-analytical with minimum usage of numerical analysis. Theobtained designs are further examined by three-dimensional finite element analysis to understandits effectiveness and to probe the validity of the approximations used. The best linearity factor(defined as%deviation from the ideal case) obtained is 1.34% for both shutter- and reflection-typedevices when the conditions are set as 1-dB insertion loss and 50-dB maximum attenuation.

Study of Autofocusing and Image Fusion for Multi-Focus Plankton Imaging by Digital HolographicMicroscopy

Ming Tang, CHAO LIU, and Xiaoping Wang

Doc ID: 370814 Received 24 Jun 2019; Accepted 22 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: Digital holographic microscopy is becoming increasingly useful for the analysis of marine plankton. In this study,we investigate autofocusing and image fusion in digital holographic microscopy. We propose an area metricautofocusing method and an improved wavelet-based image fusion method. In the area metric autofocusingmethod, a hologram image is initially segmented into several plankton regions for focus plane detection, and anarea metric is then applied to these regions. In the improved wavelet-based image fusion method, a marked map isintroduced for labeling each plankton region with the order of refocus plane images that accounts for the mostpixels. The results indicate that the area metric autofocusing method applied to each plankton region provides ahigher depth resolution accuracy than a number of general autofocusing methods, and the mean accuracyincreases by approximately 33%. The improved wavelet-based image fusion method can fuse more than 9reconstructed plane images at a time and effectively eliminate fringes and speckle noise, and the fused image ismuch clearer than that of a general wavelet-based method, a sparse decomposition method and a pulse-coupledneural networks method. This work has practical value for plankton imaging using digital holographic microscopy.

Robust multidepth object encryption based on acomputer-generated hologram with a cascadedstructure

Mei-Lan Piao, Shigang Wang, Yan Zhao, Jian Wei, Yu Zhao, and Nam Kim

Doc ID: 376532 Received 03 Sep 2019; Accepted 22 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: A robust, asymmetric, multidepth, three-dimensional object encryption scheme based on a computer-generatedFresnel hologram in the cascaded fractional Fourier domain is proposed in this paper. A layer-based Fresneltransform is used to generate a computer-generated hologram, which is then decomposed into two phase-onlymasks with a random phase distribution using matrix composition and decomposition methods. Encryption isimplemented by using the created phase-only masks in two cascaded fractional Fourier transform domains, and apair of private keys is generated in the encryption process. The cryptosystem is asymmetric and possesses highresistance against various potential attacks, such as brute-force, chosen-plaintext, known-plaintext, andciphertext-only attacks. The simulation results and cryptanalysis confirmed the feasibility and effectiveness of theproposed encryption scheme.

PGC modulated laser interferometer formeasurement of ground vibration on AbsoluteGravimeter

Zhenyu Xiong, Guo wei, xudong yu, xingwu long, and Youguang Guo

Doc ID: 379337 Received 01 Oct 2019; Accepted 22 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: This paper presents an innovative interferometer based on phase generated carrier (PGC) method to meet therequirement of micro vibration detection on Absolute Gravimeter (AG). Our results, both simulation and experimentsincluded, verified the feasibility of the interferometer. Based on this interferometer, continuous micro vibration areobtained and compared with detected results by 991B seismometer synchronously. The interferometer accuracyreaches 10-8m and the detected vibration frequency is less than 100Hz. These findings can help broaden the applicationof interferometer and provide new guideline for vibration measurement.

Single-shot optical multiple-image encryption byjointly using wavelength multiplexing and positionmultiplexing

Xiaoliang He, Hua Tao, Zhilong Jiang, Yan Kong, Shouyu Wang, and Liu Cheng

Doc ID: 380167 Received 16 Oct 2019; Accepted 22 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: In this study, a single shot large-capacity optical multiple-image encryption method based on wavelengthmultiplexing and position multiplexing is proposed. In the encryption process of the proposed method, multipleplane waves of different wavelengths are adopted to illuminate secret images which are placed at differentpositions along the optical axis. All the secret images are encoded into a single grayscale intensity-only imagewhich is recorded by a monochromic camera by applying a diffractive-imaging based double random phaseencoding (DRPE) system. In the decryption process, high accuracy images are decrypted without crosstalk from theintensity image through multi-mode phase retrieval algorithm and two step iterative shrinkage/thresholding(TwIST) algorithm. The feasibility of the proposed method is demonstrated by numerical simulations.

Experimental Research on Raman-based DistributedTemperature Sensor Assisted by PCA for Locating theTemperature Abnormal Event of the Nuclear WasteDrums

Honghui Wang, Xiang Wang, Xianguo Tuo, Tong Liu, Lingyu Meng, and Pan Zhong

Doc ID: 377554 Received 10 Sep 2019; Accepted 21 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: Aiming at the application for the location of the temperature abnormal event of the nuclear waste drums in thenuclear waste temporary storage repository by Raman-based distributed temperature sensor, we proposed aprincipal component analysis (PCA) based method for locating the temperature abnormal event of the nuclearwaste drums. The effectiveness of the proposed method is verified in the physical simulation device of the nuclearwaste drums. Firstly, some samples of the temperature abnormal event with known location are taken as thereference samples, and their features are extracted by PCA. Then, the features of the test sample data to be locatedare also extracted by PCA. The Euclidean distance is used to measure the similarity between the features of the testsample and the feature of each reference sample. Finally, we find the reference sample that is most similar to a testsample, the location of which is considered the location of the temperature anomaly event for the test sample. Theexperimental results show that the proposed method can accurately locate the temperature abnormal event of thenuclear waste drums, and the accuracy rate can reach 96.00%. The method that is proposed in this paper canreliably locate the temperature abnormal event generated by the nuclear waste temporary storage repositoryinduced by external factors such as landslides or earthquakes, and provide technical support for nuclear safety.

Analysis of highly sensitive side polishedhollow fiber plasmonic sensor and itsapplication as a magnetometer

TULIKA KHANIKAR and Vinod Kumar Singh

Doc ID: 376525 Received 03 Sep 2019; Accepted 21 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: In this article, a highly sensitive hollow fiber (HF) sensor based on surfaceplasmon resonance (SPR) is proposed and analyzed numerically. The sensor design involvesa side polished HF with a nanoscale gold film deposited over the polished surface and ananalyte filled core. The hollow portion of the fiber serves simultaneously as analyte channeland core, when filled with high refractive index (RI) liquid. By analyzing the modalcharacteristics of the sensor using finite element method (FEM), it is found that thewavelength sensitivity of the HF sensor varies from 25,642 nm/RIU (refractive index unit) to60,000 nm/RIU in the range 1.45 to 1.47 RIU along with highest amplitude sensitivity of4 1.7 RIU-1. The minimum measurable alteration by the sensor lies in the order of 10-6 RIU.The sensor also exhibits high value of FOM (figure of merit) upto 976 RIU-1 representing avery good overall performance. Moreover, due to the feasibility of design, the specificapplication of the sensor to magnetic field sensing is also demonstrated in this article andachieved maximum sensitivity of 1361 pm/Oe.

Ultra-smooth TiO2 thin film based optical humiditysensor with a fast response and recovery

Xiaoqing Wang, Min Lai, Ruijie Gao, Xixi Huang, Ziming Zhao, Yang Yang, Gaige Zheng, and Yan Ma

Doc ID: 378613 Received 24 Sep 2019; Accepted 21 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: An ultra-smooth TiO2 thin film based optical humidity sensor was fabricated via a modified dip coatingprocess. The TiO2 film possessed a root mean square (RMS) roughness of 2.6±0.3 nm. Measurement ofrelative humidity (RH) was performed by modulation in the intensity of laser transmitted at roomtemperature. The optical humidity sensor based on TiO2 film exhibited two-segmented linearity in thewhole RH range. The response time and recovery time were determined to be 27 s and s,respectively. To our knowledge, the optical humidity sensor achieved the fastest recovery to dateamong those modulated in optical power. The fast response and recovery is attributed to the smoothsurface of sensing film which allows the rapid equilibrium between adsorption and desorption of watermolecules on film surface. In addition, this optical humidity sensor possessed an excellentreproducibility and long-term stability after aging. The sensing mechanism is based on thechemisorption of water molecules in low RH range and formation of water droplet in high RH range onthe surface of TiO2 film.

Camera calibration for anamorphic lenses with 3Dtargets

Zhang Jinkai, Xue Wang, Mengmeng Ma, Fajia Li, Haining Liu, and Huanyong Cui

Doc ID: 378841 Received 03 Oct 2019; Accepted 21 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: Anamorphic lenses, with different optical powers along the tangential plane and the sagittalplane, is calibrated in this paper. The imaging model for anamorphic lenses is introduced. Comparingwith the pinhole model, it has two more intrinsic parameters: the anamorphic distance and theanamorphic angle. The anamorphic lens has two optical centers: one is in the tangential plane and theother is in the sagittal plane. The distance between the two optical centers is the anamorphic distance.The anamorphic angle refers to the angle between the camera coordinates and the pixel coordinates inthe CCD plane. Formulas determining the initial value of the anamorphic distance are provided. Twoexperiments are conducted for the anamorphic lens calibration. As a comparison, the anamorphic lensis calibrated using the anamorphic imaging model and the pinhole model respectively. The calibrationaccuracy can be improved remarkably if the anamorphic imaging model is applied. And calibratedresults for the anamorphic distance and the anamorphic angle are very stable for different positions ofthe calibration target, which shows the validity and effectiveness of the anamorphic imaging model foranamorphic lens calibration.

High harmonic generation wave frontdependence on driving infrared wave front

Thomas Wodzinski, Swen Künzel, Jayanath C.P. Koliyadu, Mukhtar Hussain, Barbara Keitel, Gareth Williams, Philippe Zeitoun, Elke Plönjes, and Marta Fajardo

Doc ID: 378843 Received 25 Sep 2019; Accepted 21 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: With high harmonic generation (HHG) spatially and temporally coherent XUV to softx-ray (100 nm to 10 nm) table-top sources can be realized by focusing a driving infrared (IR) laseron a gas target. For applications like coherent diffraction imaging, holography, plasma diagnosticsor pump-prope experiments it is desirable to have control over the wave front (WF) of the HHsto maximize the number of XUV photons on target or to tailor the WF. Here, we demonstratecontrol of the XUV WF by tailoring the driving IR WF with a deformable mirror. The WF ofboth IR and XUV beam are monitored with WF sensors. We present a systematic study of thedependence of the aberrations of the HHs on the aberrations of the driving IR laser and explainthe observations with propagation simulations. We show that we can control the astigmatismof the HHs by changing the astigmatism of the driving IR laser without compromising the HHgeneration efficiency with a WF quality from 8 to 13:3. This allows us to shape the XUVbeam without changing any XUV optical element.

Very simple and compact optical half-subtractor based onphotonic crystal resonant cavities in Si rods

Reza Talebzadeh and Nima Namdari

Doc ID: 378882 Received 26 Sep 2019; Accepted 21 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: In this paper, we propose a very simple and compact structure to realize the subtractingoperation using resonant cavities in a photonic crystal structure. The cross-section of thestructure is 103 μm2 and is desirable for integration based on popular planar technology. Inthe designed subtractor, the cavity was responsible for selecting the wavelength. By changingthe boundary rods' condition of the cavity, the mode could resonate at the desiredfrequencies. To have resonant cavities, we introduce four defect rods between the input andthe output waveguides. The results exhibit the true performance of the device. We just usedsilicon rods in the proposed device and hence is very simple to be fabricated. Finitedifference time domain method used for analyzing the proposed structure. The simulationresults show that the contrast ratio of the device is 5 dB. The maximum rise and fall times are1.5 ps and 0.5 ps respectively.

Characterization of optofluidic devices for the sorting of sub-micron particles

james white, cyril Laplane, Reece Roberts, Louise Brown, Thomas Volz, and David Inglis

Doc ID: 379109 Received 30 Sep 2019; Accepted 21 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: In this work, we investigate methods of fabricating a device for the optical actuation of nanoparticles. To create the microfluidic channel we pursued three fabrication methods: SU-8 to PDMS soft lithography, laser etching of glass, and deep reactive ion etching of fused silica.We measured the surface roughness of the etched side-walls, and the laser power transmission through each device. We then measured the radiation pressure on 0.5μm particles in the best performing fabricated device and in a square glass capillary.

Enhanced high slope-efficiency and high power LDside-pumped Er:YSGG laser

XIanlin Ye, Xiafei Xu, Huaijin Ren, Bin Zhang, Yanhua Lu, Xiaoming Chen, Lei Zhang, Xing Wei, Min Wan, and Tao He

Doc ID: 380388 Received 16 Oct 2019; Accepted 21 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: We designed a high-slope-efficiency and high-power Laser Diode (LD) side-pump Er:YSGG laser based on theanalysis for the effect of the crystal dimension and the LD distribution on the temperature and energy distributionsin laser crystal. A maximum output power of 34.9W for 2.8μm mid-infrared laser was achieved at 200A, 120Hz and500μs pulse width, corresponding to the slope efficiency of 13.7% and optical–optical efficiency of 12.7%.Moreover, the beam quality M2x/M2y factors of the laser were measured to be 5.15/5.19 and the far-fielddivergences Θx/Θy were 9.52/9.75 mrad

The influence of dry etching on the propertiesof SiO2 and HfO2 single layers

Lingyun Xie, Huasong Liu, Jun Zhao, Hongfei Jiao, Jinlong Zhang, Zhanshan Wang, and Xinbin Cheng

Doc ID: 377797 Received 16 Sep 2019; Accepted 21 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: A comparative study was performed to investigate how the etching methods andparameters affect the properties of SiO2 and HfO2 coatings. SiO2 and HfO2 single layers wereprepared by electron-beam evaporation (EBE), ion-beam assisted deposition (IAD) and ionbeam sputtering (IBS) respectively. Then, ion beam etching (IBE), reactive ion etching (RIE)and inductively coupled plasma etching (ICPE), were used to study the influence of ionbombardment energy and chemical reaction on the etching rates and properties of theprepared SiO2 and HfO2 single layers. For SiO2 coatings, chemical reaction plays a dominantrole in determining the etching rates, so ICPE that has the strongest CHF3 plasma shows thehighest etching rate. Moreover, all three etching methods barely have no influence on theproperties of SiO2 coatings. For HfO2 coatings, the etching rates are more dependent on theion bombardment energy although the chemical reaction using CHF3 plasma also helps toincrease the etching rates to some extent. To our surprise, the ion bombardment with energyas high as 900V does not change the amorphous microstructure or crystalline states ofprepared HfO2 coatings. However, the high energy ion bombardment in IBE significantlyincreases the absorption of the HfO2 coatings prepared by all deposition techniques anddecreases their laser damage resistance to different extent.

Coordinate calculation for direct shape measurementbased on optical flow

Sun Ping, Qing Dai, Yuxin Tang, and zhifang lei

Doc ID: 374627 Received 13 Aug 2019; Accepted 21 Nov 2019; Posted 21 Nov 2019  View: PDF

Abstract: A quite novel surface profilometry is proposed, which adopts a single optical grating projection setup with a smallprojection angle. The height distribution of the measured surface is retrieved by calculating the coordinates of theintersection between projecting ray and observing sight line. While the position of the observing point in deformedfringe pattern can be detected by fringe optical flow. The relationship between optical flow and the heightdistribution of the tested surface is established. Simulations and some primary experiment results are completedto prove that the proposed method is feasible to measure complex surface. The main advantage of the proposedmethod is obviously that the height distribution of the measured surface can be obtained directly without phase-toheighttransformation.

Polarimetric Imaging Detection Using a ConvolutionalNeural Network with 3-D and 2-D ConvolutionalLayers

Rui Sun, Xiaobing Sun, Feinan Chen, Qiang Song, and Hao Pan

Doc ID: 375823 Received 19 Aug 2019; Accepted 20 Nov 2019; Posted 21 Nov 2019  View: PDF

Abstract: Polarimetric imaging detection is a relatively new and largely undeveloped field. Although convolutional neuralnetworks (CNN) have achieved great success in two-dimensional (2-D) normal intensity images in the field of targetdetection, traditional CNN methods have not been widely applied to optical polarimetric images, and they cannot takefull advantage of the connection between different polarimetric images. To solve this problem, three-dimensional (3-D)convolutions are adopted to consider the relationship between S0, S1, and S2 images as a third dimension. Based on the3-D convolutions, a CNN with 3-D and 2-D convolutional layers is introduced to further improve the success rate oftarget detection with limited polarimetric images. The evaluations in different natural backgrounds reveal that theproposed method achieves higher detection accuracy than that of two traditional methods for comparison.

Optical crosstalk and off-axis modeling of anintrinsic coincident polarimeter

Ruonan Yang, Pratik Sen, Brendan O'Connor, and Michael Kudenov

Doc ID: 380526 Received 18 Oct 2019; Accepted 20 Nov 2019; Posted 21 Nov 2019  View: PDF

Abstract: Polarimeters have broad applications in remote sensing, astronomy, andbiomedical imaging to measure the emitted, reflected, or transmitted state of polarization. AnIntrinsic Coincident (IC) full-Stokes polarimeter was previously demonstrated by our group,in a free space configuration, by using stain-aligned polymer-based organic photovoltaics. Tominimize the model’s complexity, these were tilted to avoid cross-talk from back-reflections.In this paper, we present a theoretical model of a monolithic IC polarimeter which considersthe back-reflection’s influence for on-axis light. The model was validated using a monolithicfour-detector polarimeter, which achieved an error of less than 3%. Additionally, an off-axismodel was produced and validated for a simpler two detector polarimeter, demonstrating anerror between the TM and TE polarized components of less than 3% for angles spanning an18° incidence cone.

Arrays of spatially structured non-diffracting opticalbeams

Joel Mendonça, Michel Zamboni-Rached, Leonardo Ambrosio, and Carlos Santos

Doc ID: 373417 Received 29 Jul 2019; Accepted 20 Nov 2019; Posted 21 Nov 2019  View: PDF

Abstract: Non-diffracting optical beams and their structured versionshave been extensively studied, theoretically andexperimentally, over the last two decades, rending importantapplications in fields like imaging, microscopy,remote sensing, optical manipulation, free space optics,etc.. In this paper, we theoretically construct arraysof non-coaxial structured non-diffracting beamsby using the so called Frozen Wave method. We alsodevelop techniques based on polarization allocationsand apodizations to mitigate undesirable interferencesamong neighboring beams. Our results can find interestingapplications in all fields that benefit from the useof non-diffracting beams.

Residual Stress Birefringence of Highly ReflectiveMirrors with Different Number of Layers

Shilei Xiao, Bincheng Li, and Jing Wang

Doc ID: 377910 Received 13 Sep 2019; Accepted 20 Nov 2019; Posted 25 Nov 2019  View: PDF

Abstract: Residual stress birefringence of highly reflective mirrors is a challenging problem due to its dubious origin andintricate nature. In this paper, birefringences of highly reflective mirrors manufactured under same depositionparameters but structured with different number of high and low refractive-index (HL) layer pairs are measuredwith cavity ring-down technique by mirror rotation method together with a differential loss approximation model.Experimental results show that birefringence retardation increases with the increasing number of the HL layerpairs. Further measurements across the mirror surface indicate a non-uniform birefringence distribution, whilecurvature analysis of stress-deformed surface gives more clues to the origins of birefringence.

Squint-looking differential synthetic aperture ladar:signal processing and experimental demonstration

DanYang Li, Jin Wu, Lei Wan, DeBin Wang, Wu Tong, and Ke ChangJun

Doc ID: 376890 Received 02 Sep 2019; Accepted 19 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: Squint-looking differential synthetic aperture ladar(DSAL) is reported with detailed signal processingmathematics and high resolution experimental demonstrations. Based on DSAL principle and standardsquint-looking SAR theory, the data processing procedures on squint-looking DSAL image formation are obtained.The experimental DSAL setup, operating in “step-stop” strip map mode, adopts a frequency chirped laser with awavelength of 1550nm as illuminating source and a specially designed random phase generator to introduce largecommon mode random phase error (RPE) into the phase history data (PHD) of both receiving sub-apertures. Highresolution DSAL images of a cooperative target at distance of 1.85m and squint-looking angle of -10° or +10° aredemonstrated. The DSAL images, with or without large RPE, are all well focused by straightforwardly following thegiven data processing steps. The result illustrates that DSAL technique is robust in removing common mode phaseerrors in squint-looking configuration.

Broadband Phase-Shifting Mirrors forUltrafast Lasers

Michael Trubetskov, Tatiana Amotchkina, Lukas LEHNERT, Jordi Sancho-Parramon, Keyhan GOLYARI, Vesna Janicki, Marcus Ossiander, Martin Schultze, and Vladimir Pervak

Doc ID: 377746 Received 12 Sep 2019; Accepted 19 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: Metal dielectric phase-shifting multilayer optical elements have been developedproviding broadband, virtually dispersion-free polarization manipulation down to the fewcyclelevel. These optical elements are Ag/Al2O3 mirrors that operate in the spectral rangefrom 500 nm to 100 nm, exhibit reflectance higher than 95% and a differential phase shiftbetween the s-and p-polarization about 90° distributed over four bounces. The mirrors havebeen designed, produced and reliably characterized based on spectral photometric andellipsometric data using non-parametric approach as well as multi-oscillator model. Theoptical elements have been implemented into a few-cycle laser systemwhere they transformedlinearly polarized few-cycle light pulses to circular polarization.

Ground-based measurements of total ozonecolumn amount with a multi-channelmoderate-bandwidth filter instrument at the TrollResearch Station, Antarctica

Milos Sztipanov, Lubna Tumeh, Wei Li, Tove Svendby, Arve Kylling, Arne Dahlback, Jakob Stamnes, Georg Hansen, and Knut Stamnes

Doc ID: 378368 Received 18 Sep 2019; Accepted 19 Nov 2019; Posted 19 Nov 2019  View: PDF

Abstract: Combining information from several channels of the NILU-UV irradiance meter,one may determine the total ozone column (TOC) amount. A NILU-UV instrument has beendeployed and operated on two locations at Troll research station in Jutulsessen, Queen MaudLand Antarctica for several years. The method used to determine the TOC amount is presentedand the derived TOC values are compared with those obtained from the Ozone MonitoringInstrument (OMI) located on NASA’s AURA satellite. The findings show that the NILU-UVTOC amounts correlate well with the results of the OMI and that the NILU-UV instruments aresuitable for monitoring the long-term change and development of the ozone hole. Because of thelarge footprint of OMI, NILU-UV is a more suitable instrument for local measurements.

Comparison of the optical performance of differentstructural space solar power stations

Xianlong Meng, Cunliang Liu, Kun Du, and Xiaohui Bai

Doc ID: 375926 Received 28 Aug 2019; Accepted 19 Nov 2019; Posted 20 Nov 2019  View: PDF

Abstract: Solar power satellite(SPS) concept is an elegant solution to the challenge of providing large-scale energy forhumanity: a large platform, positioned in space in a high Earth orbit continuously collects and converts solarenergy into electricity. SPS-ALPHA is composed of a large number of small modules which enables the modularityand lower cost of machining/space transport. Until now two options of SPS-ALPHA have been proposed, Mark-Iversion (sigmoid curve-based shape) and Mark-Ⅱ version (conical shape). The current study aims to find theoptimal design parameters of reflecting modules for above two versions when high optical efficiencies and stableirradiance distribution are both achieved for effective PV layout design. To meet this target, Ant ColonyOptimization (ACO) algorithm combined with dynamic source-target mapping was adopted to find the optimalaiming vectors of reflectors. The optical transmission characteristics under different incident degrees wereinvestigated using a two-step Monte-Carlo ray tracing (MCRT) method. Receiving heat flux distribution and erroranalysis of two structural versions would be compared as well. The article can provide basic data and reference forengineering constructions of SPS-ALPHA in next step.

Design of InP/ZnO core-shell nanocone array solar cellwith efficient broadband light absorptionenhancement

Zongyi Zhang, Yonggang Wu, Xuefei Qin, Zihuan Xia, and Jian Zhou

Doc ID: 376910 Received 03 Sep 2019; Accepted 19 Nov 2019; Posted 20 Nov 2019  View: PDF

Abstract: We design a standing semiconductor-dielectric core-shell nanocone array (CSNCA) which can not only concentratethe incident light into the structure, but also confine most of the concentrated light to the semiconductor (InP) coreregion, which enhances remarkably the light absorption of the more material-saving semiconductor core. We findguided resonance features along the radial and FP-resonant features along the axial direction by analyzing theelectric field patterns at the absorption spectrum peaks. The CSNCA can support multiple higher-order HE modes,in comparison to the bare nanocone array (BNCA). Results based on detailed balance analysis demonstrate that thecore-shell design gives rise to higher short-circuit current and open-circuit voltage, and thus higher powerconversion efficiency. Detailed research is focused on the 1 μm high CSNCAs, and a remarkable power conversionefficiency enhancement (42.2%) is gained compared with the BNCAs.

Phase-mismatch dependence of four-wave mixingeffect in semiconductor optical amplifiers

Osayd Kharraz, Michael Connelly, ABU SAHMAH SUPA’AT, Ahmad Abas, Mohammed Alresheedi, and Mohd Adzir Mahdi

Doc ID: 377491 Received 19 Sep 2019; Accepted 19 Nov 2019; Posted 20 Nov 2019  View: PDF

Abstract: Phase-mismatch effect due to polarization-dependent mode confinement factor has been shown to be no crucialproblem in semiconductor optical amplifiers (SOAs) and is usually not accounted for. In this work, phase-mismatchfour-wave mixing (FWM) process in SOA devices is experimentally reported. The results reveal a sinc-like behaviorin the intensity of FWM conjugate as a function of wavelength separation between transverse electric(TE)/transverse magnetic (TM) pumps due to induced confinement factors difference. Efficient FWM occurred for adetuning shift of about 500 GHz, limited by phase-mismatch conditions and determined by coherence lengthrequired for low and high frequencies to complete a full phase-match cycle. Phase-match FWM with an infinitycoherence length can be fulfilled by proper alignments of co-polarized TE/TM modes of input waves with respect tothe birefringent axes of the device structure.

Effect of Different Regression Algorithms on the EstimatingLeaf Parameters based on the Selected CharacteristicsWavelengths by Using PROSPECT Mode

Yangyang Zhang, jian Yang, Xiuguo Liu, Lin Du, Shuo Shi, Jia Sun, and Biwu Chen

Doc ID: 377986 Received 13 Sep 2019; Accepted 19 Nov 2019; Posted 20 Nov 2019  View: PDF

Abstract: In this study, the characteristic wavelengths of leaf biochemical parameters (including carotenoid content, chlorophyll a + b content, dry mattercontent, equivalent water thickness, and leaf structure parameter) were obtained through a sensitivity analysis based on a physical model. Then,performance of the selected characteristic wavelengths for monitoring Leaf biochemical contents (LBC) was analyzed by using the following sixpopular regression algorithms, random forest, back-propagation neural network, support vector regression, radial basic function neural network,partial least-square regression, and Gaussian processes regression of different parameter values/kernel functions/training functions. In addition,the optimal parameters of each regression algorithm for estimating LBC were determined. Lastly, the effect of different regression algorithms onthe accuracy of LBC estimation using four different datasets was also discussed. The results demonstrated that the selected 10 characteristicwavelengths combined with the Gaussian Process Regression model can be efficiently applied in estimating LBC.

A Self-Aligned Micro-Optic Integrated PhotonicPlatform

Aleksandar Jovic, Nuria Sanchez Losilla, Juan Sancho-Durá, Kirill Zinoviev, Jose Rubio, Eduardo Margallo Balbas, Massimo Mastrangeli, gregory pandraud, and Lina (P.M.) Sarro

Doc ID: 378272 Received 01 Oct 2019; Accepted 19 Nov 2019; Posted 20 Nov 2019  View: PDF

Abstract: In this work we present the fabrication technology of a monolithically integrated photonic platform combiningkey components for Optical Coherence Tomography (OCT) imaging, thereby including a photonicinterferometer, a collimating lens and a 45 reflecting mirror which directs the light from the interferometerto the collimator. The proposed integration process simplifies the fabrication of an interferometricsystem and inherently overcomes the complexity of costly alignment procedures while complying withthe necessarily stringent optical constraints. Fabricated waveguides characterisation showed total opticallosses as low as 3 dB, and less than 1 dB of additional loss due to the Si 45 mirror facet. The alignmentstandard deviation of all components is within 15 nm. The integrated lens profile achieves a divergenceangle smaller than 0.7° which is close to that of a collimator. The proposed photonic platform providesthe premise for low cost and small footprint single-chip OCT systems.

Separation of misalignment aberrations ininterferometric testing for the surface measurementof frustum of a cone

Wei Liu, Peng Wu, Guangyu Wei, Qingjie Lu, Minghui Yu, Quanzhao Wang, and Sen Han

Doc ID: 376168 Received 23 Aug 2019; Accepted 19 Nov 2019; Posted 19 Nov 2019  View: PDF

Abstract: The separation of misalignment aberrations is a crucial step in interferometric testing for the acquisitionof the real surface. In this paper, a Fizeau interference system and a conical mirror (CM) with a certain angle wereused to achieve the shape measurement of the inner surface of frustum of a cone (FC). Based on the ray-tracingmethod, the relationship between the adjustment errors and misalignment aberrations was established, and themisalignment aberrations could be removed by using the error separation model which is according to the leastsquarealgorithm theory. The simulation and practical measurement results indicate that the approach proposed isvalid and feasible.

Random phase shifting shadow moiré usingone-dimensional minimizer

Hubing Du, Ruiqing Guo, Zhouxuan He, and PU MA

Doc ID: 377699 Received 12 Sep 2019; Accepted 18 Nov 2019; Posted 19 Nov 2019  View: PDF

Abstract: The introduction of a random phase-shifting technique into a shadow moirésystem, where an equal and known (or unknown) phase step is used to demodulate the phaseof interest, is beneficial for the improvement of measurement accuracy. However, in spite ofrecent advances in optical metrology phase-shifting techniques, simultaneously estimatingunequal and unknown phase shifts from three random phase-shifting fringe patterns remains asignificant challenge.This paper presents a one-dimensional minimizer based technique to address this ill-posedproblem of phase demodulation from random phase-shifting patterns. In this method, two newsets of connected fringe patterns, without background illumination, are constructed throughnormalizing the secondary fringe patterns. Then, a generalized phase-shifting algorithm isdeveloped by utilizing the character of the modulation factor’s standard deviation distribution.Both numerical simulations and optical experiments are performed to demonstrate the highaccuracy and robustness of the proposed method.

Passively Q-switched erbium-doped fiber laser utilizing tungsten oxide as asaturable absorber

Ahmed Nady and Sulaiman Wadi Harun

Doc ID: 379025 Received 26 Sep 2019; Accepted 18 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: We demonstrated a passively Q-switched fiber laser utilizing tungsten oxide (WO3) thin film as asaturable absorber (SA). WO3-SA was sandwiched as a polymer composite film between fiberferrules in an erbium-doped fiber cavity. WO3 exhibits high nonlinear optical responsecharacterized by appropriate modulation depth of 10% and saturation intensity of 100 MW/cm2.The fiber cavity starts to generate a stable pulse train whereby as the pump power increases from45 to 165 mw, the repetition rate increases from 16.75 to 56.3 kHz, while the pulse widthdecreases from 13.8 to 4.3 μs. The Q-switched laser generated maximum pulse energy of 6.6 nJobtained at 165 mW, which was the maximum pump power available by the used laser diode.This is the first demonstration of Q-switched fiber laser based on WO3-SA which couldcontribute as a new potential saturable absorber material in the field of pulsed fiber lasers.

Single step 3D printed integrated optical system and itsimplementation for sensing application using Digital LightProcessing technology

Kankan Swargiary, Pasit Jarutatsanangkoon, Pimpakan Suwanich, Romuald Jolivot, and Waleed Mohammed

Doc ID: 377938 Received 13 Sep 2019; Accepted 18 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: This study proposes a single step integrated optical fabrication scheme utilizing 3D printer using Digital LightProcessing (DLP) technology. Strong light confinement in the fabricated structure is realized through theintroduction of elevated (tower shaped) waveguide in a transparent photosensitive resin (PX-8880). The fabrication isoptimized to maximize light confinement through varying the dimensions of the guiding region and the towerstructure. Benefiting of the surface roughness produced by the slicing process in the 3D printing (50 μm resolution),the fabricated structure was tested for vapor sensing. Obvious intensity dynamics have been reported due to thechange of the optical scattering due to the presence of vapor as well as polymer vapor interaction. Though thereported response time is long, further optimization can lead to practical operation time.

An optical OCDMA coding and 3D Imaging techniquefor non-scanning full-waveform LiDAR system

Xingyu Yang, jinshan su, Liting Hao, and yuanqing wang

Doc ID: 374824 Received 07 Aug 2019; Accepted 18 Nov 2019; Posted 19 Nov 2019  View: PDF

Abstract: Full-waveform LiDAR system has been developed owing to its superiority of high precision and highresolution. However, how to further improve the imaging speed and resolution continues to be a problem. In thisstudy, we propose an optical orthogonal code division multiple access (OCDMA) coding and 3D imaging techniqueand a non-scanning full-waveform LiDAR system is first demonstrated. Encoding, multiplexing and decoding arethe essential modules of the OCDMA lidar system which use M detectors and N-bits code to achieve high accuracydecomposition for M×N pixels. In this paper, the complete 3D imaging LiDAR system is introduced and theimplementation of encoding and decoding is also illustrated. To prove that the technology is scientific and effective,an imaging experiment has been carried out. The experimental result indicates that the system with only 4 APDscan achieve 256 pixels. Moreover, the vertical resolution is about 1.8cm and the range resolution is 15cm at thedistance of 40m.

Calibration Free-Laser Induced Breakdown SpectroscopicAnalysis of Copper-Rich Mineral Collected from Gilgit-Baltistan Region of Pakistan

Muhammad Hafeez, Shahab Abbasi, Muhammad Rafique, Rizwan Hayder, Muhammad Sajid, Javed Iqbal, Nasar Ahmed, and Shabnum Shahida

Doc ID: 371641 Received 02 Jul 2019; Accepted 18 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: In this article, we present the results of compositional analysis of a Copper-rich mineral known as Malachite,collected from Gilgit-Baltistan region of Pakistan. Calibration Free-Laser-induced breakdown spectroscopy (CFLIBS)technique has been employed for determination of elemental composition of the sample. The study aims atthe investigation of the presence of precious elements, if any, in minerals of local origin. . Laser beam of 1064 nmwavelength from a nanosecond pulsed Q-switched Nd:YAG laser was focused on the surface of the sample andemission spectrum was obtained with the help of LIBS2000 Spectrometer covering the spectral range between 200to 700 nm. Results obtained through analyzing the characteristic emission lines of different elements have confirmedthe presence of sixteen (16) elements in investigated sample viz. Cu, Si, Al, K, Fe, Mn, Ag, Ti, Ba, Sr, Ca, Mg, Na,Li, C and H. For quantification of detected elements in the sample, Calibration Free (CF) method, which is based onlocal thermodynamic equilibrium (LTE) and optically thin plasma model, was employed. Plasma parameters, suchas electron number density and temperature, were calculated for the purpose of subsequent calculations. Sevenelements viz. Cu, Fe, Si, Ca, Mg, Mn and Al, were quantified out of initially detected 16 elements and theirconcentration in terms of weight percentage was 43.15, 20.13, 18.31, 9.46, 3.28, 3.16 and 2.51% respectively.Presence of all seven elements which were quantified by CF-LIBS was confirmed by X-Ray Fluorescence (XRF)analysis.

An algorithm to overcome atmospheric phase errors inSAL data

Randy Depoy and Arnab Shaw

Doc ID: 375590 Received 16 Aug 2019; Accepted 18 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: Synthetic aperture ladar is an emerging sensor technologyproviding high-resolution imagery of targetsfrom long standoff ranges. Atmospheric turbulence corruptsthe collected phase history data with spatiallyvariantphase perturbations impacting resolution andcontrast of reconstructed imagery. We explore the efficacyof model-based reconstruction algorithms withmodel error corrections to mitigate the deleterious effectsof atmospheric turbulence and restore image quality.We present results from model error correction techniquesutilizing spatially-invariant, spatially-variant,and a model-based atmospheric phase error correction.We quantify the performance of all algorithms using anatmospheric ray trace simulation.

Modal instabilities suppression in high average powerand high finesse Fabry-Perot Cavity

LoÏc Amoudry, Huan Wang, Kevin Cassou, ronic chiche, Kevin Dupraz, Aurelien Martens, Daniele Nutarelli, Viktor Soskov, and Fabian Zomer

Doc ID: 377255 Received 06 Sep 2019; Accepted 18 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: An experimental method to remove modal instabilities induced by thermoelastic deformation in opticalhigh finesse resonators is presented and experimentally investigated. The method is found suitable formulti-mirror folded monolithic and compact cavities as those used in particle accelerator environment.It is also suitable for very large stacked average power. Stable operation at 200 kW intracavity averagepower is experimentally demonstrated.

Innovative Fiber Bragg Grating Filter based onGraphene Photonic Crystal microcavity

Forough Bozorgzadeh, Davood Ahmadi, and Mostafa Sahrai

Doc ID: 378117 Received 18 Sep 2019; Accepted 17 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: We propose a new model for Fiber Bragg grating (FBG) filter based on one-dimensional defective photonicbandgap (PBG) structures, which operates within the Telecom windows. The device is realized inan asymmetric SiO2/TiO2 photonic crystal (PC) microcavity with the defect layer of graphene disk placedin the center of the structure. The theoretical analysis of the optical properties of the narrow-band FBGfilter is given based on the combination of density matrix approach with transfer matrix method (TMM).The effect of the incident angle and the polarization of the probe field on the transmittance spectra is calculated.Also, tuning the filtering wavelength and the number of guided modes is performed by changingthe properties of PC’s defect layer. It is shown that depending on the ratio of the coupling fields’ intensity,the probe field absorption can be minimized and even be amplified in l0 = 1550nm. The results showvery promising potential for fabrication of FBG filters operating in near-infrared regime for light-wavecommunications.

Deep search methods for multilayer coatingsdesign

Michael Trubetskov

Doc ID: 378150 Received 17 Sep 2019; Accepted 16 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: Many existing well-known multilayer design methods are based on so-called greedyalgorithms. New deep search algorithms developed for needle optimization, gradualevolution, and design cleaner methods, are presented. The algorithms possess machinelearning features. The advantages of the deep search methods are demonstrated on a set ofexamples including OIC Design Contest 2019..

Thin-film interference filters illuminated by tiltedapertures

Thomas Goossens and Chris Van Hoof

Doc ID: 377396 Received 13 Sep 2019; Accepted 16 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: Thin-film interference filters can be illuminated by a circular aperture at differentangles. Each situation produces a different transmittance spectrum. We present an analyticalmodel that, for small tilt angles, predicts the change in transmittance for an arbitrary position ofthe filter in three dimensional space. The model is extended to take into account higher-orderharmonics. We also derive a formula to predict the change in central wavelength and we validateour results by comparison with thin-film transfer-matrix calculations. A key property of ourapproach is that the model can be combined with empirical data to predict the transmittancewithout knowing the filter design.

Analysis and optimization of the Glass patternrealized by a microlens array

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

Doc ID: 374630 Received 05 Aug 2019; Accepted 16 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: It is well known that the superposition of two identical random dot patterns may give rise to a particular form of moiréeffect known as a Glass pattern. Integrating a microlens array and a micropattern array, and applying a smallgeometrical transformation, it is possible to show the parallactic or the orthoparallactic motion effect when varying theviewing angle. In this paper, we study the effect of the structural parameters of Glass pattern optical system on its imagequality. The position of each elemental pattern in micropattern array are derived based on a revised model whichconsiders the finite observation distance. The image quality is evaluated by the ray analysis on the observation planeand the reconstructed image plane. Rays from different pixels of the micropattern array is evaluated by the spot size.Besides, the depth of the Glass pattern in image space is analyzed. In addition, Glass pattern optical system is simulatedand optimized by ZEMAX software. An optimal result is obtained which validates the theoretical analysis. Our study canfind potential application for designing Glass pattern optical system or optimization of those imaging systems based onmicrolens array.

Wide-angle MEMS-based imaging lidar bydecoupled scan axes

Brandon Hellman, Adley Gin, Braden Smith, Youngsik Kim, Guanghao Chen, Paul Winkler, Phillip McCann, and Yuzuru Takashima

Doc ID: 376149 Received 23 Aug 2019; Accepted 15 Nov 2019; Posted 15 Nov 2019  View: PDF

Abstract: An optical architecture for a scanning lidar in which a Digital Micromirror Device(DMD) is placed at an intermediate image plane in a receiver to decouple the trade-offsbetween scan angle, scan speed, and aperture size of the lidar’s transmitter and receiver. Inthe architecture, the transmitter with a galvo mirror and the receiver with a DMD scan thehorizontal and vertical fields of view, respectively, to enable an increased field of view of50°, centimeter transmitter beam diameter, and video frame rate range finding captures. Wepresent our optimized system and discuss the adjustable parameter tradeoffs.

Multi-plane, Multi-band image projection viaBroadband Diffractive Optics

Monjurul Meem, Apratim Majumder, and Rajesh Menon

Doc ID: 376076 Received 23 Aug 2019; Accepted 15 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: We demonstrate visible and near-IR image projection via non-absorbing, multilevelBroadband Diffractive-Optical Elements (BDOEs) in 1 or more planes. By appropriatedesign of the BDOE topography, we experimentally demonstrate: (1) different images indifferent spectral bands; (2) different images in different image planes; (3) imagemagnification by changing the distance between the illumination source and the BDOE; (4)completely flat BDOE via an index-contrast top-coating; and (5) reflective BDOEs. All ofthese are accomplished with broadband illumination. Furthermore, the BDOEs are highlyefficient, versatile and can be inexpensively mass manufactured using imprint-basedreplication techniques.

A magneto-optic rotation detection scheme forminiaturized CPT atomic clock

Qu suping, Yi Yin, Cai Dehuan, and Hao gong

Doc ID: 378968 Received 27 Sep 2019; Accepted 15 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: In order to suppress the effects of carrier and high-order sidebands on coherent populationtrapping (CPT) signal, a scheme of an elliptically polarized beam interaction with alkali atoms usingthe magneto-optic rotation detection is studied. With canceling of spin-polarized dark state in CPT statepreparation, a CPT resonance signal with a contrast of 32.5% is obtained. Our scheme requires minormodifications on the optical path in prevalent scheme, and the short-term frequency stability of ourscheme will be 5 times better than that of the prevalent scheme, making it ideal for miniaturization andpocket of CPT atomic clock applications.

Growth and characterization of Sc₂O₃ doped Ta₂O₅ thin films

Mariana Fazio, Le Yang, Ashot Markosyan, Riccardo Bassiri, Martin Fejer, and Carmen Menoni

Doc ID: 378076 Received 18 Sep 2019; Accepted 15 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: We present the optical and structural characterization of films of Ta2O5, Sc2O3 and Sc2O3 doped Ta2O5with a cation ratio around 0.1 grown by reactive sputtering. The addition of Sc2O3 as a dopant inducesthe formation of tantalum suboxide due to the "oxygen getter" property of scandium. The presence oftantalum suboxide greatly affects the optical properties of the coating resulting in higher absorption lossat l = 1064 nm. The refractive index and optical band gap of the mixed film do not correspond to that ofa mixture of Ta2O5 and Sc2O3 given the profound structural modifications induced by the dopant.

Selective amplification of spoof localizedsurface plasmons

Qiao Yu Li, Xia Zhao, hongzhou zhao, and Yong Jin Zhou

Doc ID: 379214 Received 30 Sep 2019; Accepted 15 Nov 2019; Posted 18 Nov 2019  View: PDF

Abstract: Here selective amplification of spoof localized surface plasmons (LSPs) has beendemonstrated, where two coupling stubs gathering energies from the spoof LSPs resonator aredesigned on the back of the corrugated metal-insulator-metal (MIM) ring resonator. Thequadrupole mode is selected and amplified through the coupling stubs and the incorporatedamplifier chip, and the measured transmission intensity has been increased from -6.46 dB to10.74 dB by adjusting the bias voltage. The amplification mechanism is fully investigated byusing the circuit simulation and the full wave simulation. The numerical simulations andexperimental measurement agree well with each other. The active amplified resonator can bewidely used in chemical and biological sensing in microwave frequency.

Alignment precision of polarization components

Nathan Hagen, Prathan Buranasiri, and Yukitoshi Otani

Doc ID: 379897 Received 08 Oct 2019; Accepted 14 Nov 2019; Posted 15 Nov 2019  View: PDF

Abstract: Recent research publications in the polarization literature have discussed methods for correcting for azimuthalalignment errors of optical elements in post-processing. However, we show that high angularprecision is not difficult to achieve during system alignment, so that post-processing correction shouldbe unnecessary. We estimate the alignment precision achievable for linear polarizers and waveplates inpolarization systems, showing that using an optical signal model for alignment allows a precision limitedby the quality of the optics and detectors rather than the quality of the mechanics, rendering millidegreealignment precision possible with ordinary rotational mounts.

Investigation of null reconstruction effect oforthogonal elliptically-polarization hologramat large recording angle

long shao, Jinliang Zang, fan lan, Ying Liu, and Xiaodi Tan

Doc ID: 374880 Received 26 Aug 2019; Accepted 14 Nov 2019; Posted 14 Nov 2019  View: PDF

Abstract: We report on the null reconstruction effect (NRE) of elliptically polarizationvolume hologram with orthogonal elliptically, circularly, linearly polarized waves,respectively. The NRE is a special phenomenon in polarization holography which means thediffraction efficiency declines to zero when the hologram is reconstructed by an orthogonallypolarized reading wave. In our previous work [14-16], the NRE of polarization holographyrecorded by linear and circular polarization waves have been investigated. Compared withlinear and circular polarization holography, elliptical polarization holography represents amore general and unified recording hologram. However, no work on the NRE of ellipticalpolarization holography, as far as we know, has been reported until now. In this paper, theNRE of elliptical polarization holography is investigated and demonstrated theoretically andexperimentally. First, the conditions of achieving NRE in elliptical polarization holographyare studied based on vector holography theory. The results indicate that the NRE is a commonphenomenon in polarization holography written by linear, circular and elliptical polarizationwaves. Then, a series of experiments of NRE in polarization hologram written by orthogonalelliptically, circularly, linearly polarized waves are carried out. The NRE of ellipticalpolarization holography are experimentally observed and the results are in nice agreementwith the theoretical analysis. The NRE of elliptical polarization holography is expected to beapplied in high density optical data storage and polarization controlled holographic elements.

Optical method to determine the composition oflithium niobate crystals by digital holography

Yanan Zhi, yongjian zhu, Pan Weiqing, and Kehan Tian

Doc ID: 372189 Received 11 Jul 2019; Accepted 14 Nov 2019; Posted 15 Nov 2019  View: PDF

Abstract: Because the physical properties of lithium niobate (LiNbO3) strongly depend on the composition, the accurate andconvenient methods for the determination of the composition are of great significance. Although several opticalmethods, including the measurement of UV absorption edge, the birefringence and the second harmonicgeneration, have been proved be convenient for an accurate and fast standard determination of composition inLiNbO3 single crystals, their research and commercial applications are limited by the doping component and thecomplex non-linear relationships. Based on the preliminary work, a novel optical method to determine thecomposition of LiNbO3 crystals by the digital holography is proposed. This method is based on the static internalfield, which is obtained by means of the three-dimensional (3-D) static measurement of the phase differencebetween antiparallel poling states without applying external voltage by the digital holography. In order toinvestigate the influences of composition and doping on the static internal field in LiNbO3 crystals, the measuredstatic internal field from various LiNbO3 samples with different stoichiometry, doping type and doping level aresummarized and compared. Excluding the influence of dopant, the composition has been proved to be a unique keyinfluencing factor on the static internal field in LiNbO3 crystals. A systematic measurement based on static internalfield from various sources with compositions ranging from 48.5 to 49.9 mol% (Li/[Li+Nb] ratio) has been carriedout. The approximate linear fit between static internal field and composition can provide an easy, reliable andsensitive determination of the composition in undoped and doped LiNbO3 samples.

Measurement method by inferring the thrust from thestress of the cantilever beam based on thephotoelasticity theory

Yang Ou, Yu Zhang, Jianjun Wu, Sheng Tan, and Xinru Du

Doc ID: 379819 Received 18 Oct 2019; Accepted 13 Nov 2019; Posted 14 Nov 2019  View: PDF

Abstract: A new thrust measurement system based on the photoelasticity theory has been developed to infer the thrust fromthe stress of the cantilever beam. In this method, the cantilever beam is employed as the loading element to convertthe low thrust into the high stress, and the modified dynamic photoelasticity is utilized to infer the stress value ofthe cantilever beam from the Stokes parameters of the emergent light. The experimental results validated that thethrust stand could be capable of measuring the thrust in the range of milli-Newton or millisecond, and thethickness of the beam was negatively correlated with the measurement accuracy. The average errors of theexperimental measurements for ampere forces higher than 25mN and pulse ampere forces whose width longerthan 45ms were less than ±5%. As for the real plasma discharges, the errors of the measured thrust were less than±10%.

Calibration and measurement analysis of acloud particle detection system based onpolarization detection

Fuyuan Jiang, Yang Zhang, lingbing bu, and Chenxi Chu

Doc ID: 379871 Received 07 Oct 2019; Accepted 13 Nov 2019; Posted 14 Nov 2019  View: PDF

Abstract: The phase state information of cloud water is important for the airbornemeasurement of the micro-physical properties of a cloud. A cloud particle detection systembased on polarization detection, which can be used to detect the size and phase state of cloudparticles for particle diameters of less than 50 μm, was developed by detecting the energy ofthe forward scattering and the depolarization of backscattered light. The sensitive area wascalculated though the width and depth of the field of view of the laser beam. The system wascalibrated using standard particles. The response curve of the system to the cloud particleswas obtained by calculating the relationship between the standard particles and the clouddroplets. Finally, the liquid droplets and typical non-spherical particles were measured, andthe results compared with a simulation. The comparison results indicated that the systemcould detect spherical and non-spherical cloud particles and can discriminate between nonsphericalcloud particles and liquid droplets.

Quantitative Calculation of Substrate BendingCaused by Multilayer Coating Stresses

Muneo Sugiura, Koichi TAMURA, and Mitsunobu Kobiyama

Doc ID: 378065 Received 17 Sep 2019; Accepted 13 Nov 2019; Posted 13 Nov 2019  View: PDF

Abstract: A framework to quantitatively calculate substrate bending after coating has beenproposed. By introducing fitting parameters to modified Stoney’s formula, the amount of thebending has been calculated to accuracies of less than λ 10 at 633nm, for ion-beamsputtering and ion-beam assisted deposition processes.

Multimode Fiber Coupled Superconducting Nanowire Single Photon Detectors with High Detection Efficiency and Time Resolution

Jin Chang, Iman Esmaeil Zadeh, Johannes .W.N Los, Julien Zichi, Andreas Fognini, Monique Gevers, Sander Dorenbos, Silvania Pereira, H. Urbach, and Val Zwiller

Doc ID: 379683 Received 03 Oct 2019; Accepted 12 Nov 2019; Posted 13 Nov 2019  View: PDF

Abstract: In the past decade superconducting nanowire single photon detectors (SNSPDs) have gradually become an indispensable part of any demanding quantum optics experiment. Until now, most SNSPDs are coupled to single-mode fibers. SNSPDs coupled to multimode fibers have shown promising efficiencies but are yet to achieve high time resolution. For a number of applications ranging from quantum nano-photonics to bio-optics, high efficiency and high time-resolution are desired at the same time. In this paper, we demonstrate the role of polarization on the efficiency of multi-mode fiber coupled detectors and fabricated high performance 20, 25 and 50 μm diameter detectors targeted for visible, near infrared, and telecom wavelengths. A custom-built setup was used to simulate realistic experiments with randomized modes in the fiber. We achieved over 80% system efficiency and <20 ps timing jitter for 20 μm SNSPDs. Also, we realized 70% system efficiency and <20 ps timing jitter for 50 μm SNSPDs. The high efficiency multimode fiber coupled SNSPDs with unparalleled time resolution will benefit various of quantum optics experiments and applications in the future.

Analysis of underwater wireless optical communication system performance

Yi Yang, Fengtao HE, Qiuping Guo, min wang, Jianlei ZHANG, and Zuoliang Duan

Doc ID: 376655 Received 29 Aug 2019; Accepted 11 Nov 2019; Posted 11 Nov 2019  View: PDF

Abstract: Because the underwater channel environment is complicated, it is difficult to do field experiment for analyzing the performance of underwater wireless optical communication (UWOC) systems. In this study, the spot-expansion characteristics and time-domain broadening characteristics of underwater wireless optical signals are simulated and analyzed by a Monte Carlo statistical method. Thus, an improved underwater channel transmission-attenuation model and time-domain broadening model based on UWOC are proposed, so the transmission distance characteristics of the UWOC system are obtained by combining the system parameters, and the transmission-rate characteristics can be analyzed by using Shannon-Hartley theorem. The results show that the transmission distance is linear with the receiver sensitivity and the transmission rate decays exponentially with transmission distance and is limited by the receiver sensitivity in the UWOC system.

Particle size distribution from extinction andabsorption data of metallic nanoparticles

Gabriela Calvillo, Hugo Guillen-Ramirez, Melissa DiazDuarte Rodriguez, Angel Licea Claverie, and Eugenio Mendez

Doc ID: 376977 Received 04 Sep 2019; Accepted 11 Nov 2019; Posted 11 Nov 2019  View: PDF

Abstract: We describe a method for inverting spectroscopic data of the absorption and extinction properties ofcolloidal samples of resonant particles. We show that, with some prior knowledge, the genetic algorithmemployed is able to estimate the probability density function of particle sizes. Since the data is sensitiveto the shape and material of the particles, some information about these properties can also be retrieved.The viability of the method is illustrated by inverting numerically generated data, as well as experimentaldata obtained with specially prepared samples of metallic nanoparticles in aqueous suspension.

Periodic nanostructure induced change ofdirector profiles and variable stop bands ofphotonic crystals infiltrated by nematic liquidcrystals

sibo chen, xuan zhou, Wenjiang Ye, and zhidong zhang

Doc ID: 377032 Received 03 Sep 2019; Accepted 11 Nov 2019; Posted 11 Nov 2019  View: PDF

Abstract: Photonic crystals with periodic nanostructures infiltrated by nematic liquid crystalswere investigated based on Landau-de Gennes theory. We studied the fine structures of thesystem within different amplitudes on the sinusoidal boundaries. When modulating theamplitude, the location of the defects will change. Two new director profiles occurred and thestate observed in Appl. Phys. Lett., 87(24): 241108 (2005) also appeared. The transmittancecurves show a redshift of ~0.1 μm in the mid-infrared spectra when increasing the amplitude.The location change of defect rings will induce a shift of ~22.4 nm. Variations in sinusoidalboundaries will have an effect on the transmittance spectrum. Elastic anisotropic will alsoinduce a small shift when the structure is fixed. Results could be useful in designing newtypes of photonic crystals devices or sensors.

Investigation of subsurface damage density andmorphology impact on laser-induced damagethreshold of fused silica

Hongxiang Wang, Chu Wang, Mingzhuang Zhang, Ermeng Zheng, Hou Jing, and Chen Xianhua

Doc ID: 377052 Received 05 Sep 2019; Accepted 11 Nov 2019; Posted 11 Nov 2019  View: PDF

Abstract: The laser-induced damage threshold (LIDT) of fused silica is affected by laser field intensitymodulation and laser energy absorption. In this paper, the subsurface damage (SSD) density andmorphology are detected by the small-angle taper polishing method. The modulation effect of SSDmorphology on the incident laser/electric field is analyzed by the finite difference time domain (FDTD)simulation. Finally, the LIDT of taper polished surface is tested to analyze the relationship amongLIDT, SSD density, and SSD morphology, and the results show a high correlation. A reliableregression model is obtained based on the results, which shows LIDT is inversely proportional to SSDdensity and the light intensity enhancement factor (LIEF).

Photon number measurement usingheterodyne method for detector’s quantumefficiency SPDC-based determination

Aleksey Samoylenko and Gennady Levin

Doc ID: 378794 Received 26 Sep 2019; Accepted 11 Nov 2019; Posted 12 Nov 2019  View: PDF

Abstract: Active development of such a quantum informational components as quantumcomputers and quantum key distribution (QKD) systems requires a parameterscharacterization of single photon detectors. Key property of the single photon detectors is thedetection efficiency. One of the methods of the detection efficiency measurement, listed inthe international standard ETSI, is the reference-free twin photon based Klyshko method. Thesignal to noise ratio (SNR) of this method depends on the combination of the pumpwavelength, the nonlinear crystal’s axis angle and the type of detector’s sensitive element.When the combination is difficult, one has to deal with the low SNR of the detector countsmeasurement. To gain the high SNR one has to average the long record complicated with the“random telegraph signal” noise. This type of noise exhibits high spectral density at a zerofrequency, where simple averaging works. The heterodyne based method we have proposed isto perform averaging at the higher frequency of the modulation introduced to the standardKlyshko measurement scheme. The method was numerically simulated and experimentallytested. The 14 times improvement in SNR for the proposed method relative to the simpleaveraging was demonstrated by the numerical simulation and confirmed experimentally.

Theoretical investigation of a photonicassistedinstantaneous frequencymeasurement with tunable measurementrange and resolution by adjusting chirpparameter of an optical intensity modulator

Mohsen Ganjali, S.Esmail Hosseini, Kambiz Jamshidi, and Dirk Plettemeier

Doc ID: 378833 Received 25 Sep 2019; Accepted 11 Nov 2019; Posted 12 Nov 2019  View: PDF

Abstract: Chromatic dispersion-based frequency-to-power mapping approach is often used inmicrowave photonic (MWP) instantaneous frequency measurement (IFM) receivers. In thispaper, a novel mechanism to tune the measurement range and resolution of these MWP IFMreceivers by adjusting the chirp parameter of their optical intensity modulators is proposedand demonstrated. In particular, an MWP IFM receiver with tunable measurement range andresolution based on a chirp-adjustable dual-drive Mach-Zehnder modulator (DDMZM) andtwo dispersive mediums is proposed and theoretically investigated. In the proposed MWPIFM receiver, a radio frequency (RF) signal whose unknown frequency is intended to bemeasured is applied to the two arms of a DDMZM with appropriate power ratio. By adjustingthe ratio of the two applied RF signals, the chirp parameter of the DDMZM and consequentlythe measurement range and resolution of the MWP IFM receiver can be tuned. The analyticalresults are verified by simulation results using a commercial software. The proposed methodcan also be used in most of the previously reported MWP IFM receivers based on chromaticdispersion and frequency-to-power mapping approach to tune their measurement ranges andresolutions.

Combined frequency-locking technology ofdigital integrated resonator optic gyroscopewith a phase-modulated feedback loop

Jiangbo Zhu, Wenyao Liu, ziwen pan, Yu Tao, Shihao Yin, Jun Tang, and Jun Liu

Doc ID: 373298 Received 23 Jul 2019; Accepted 10 Nov 2019; Posted 11 Nov 2019  View: PDF

Abstract: In the resonator fiber optic gyroscope (RFOG), the conventional laser feedbackloop is realized by adjusting the laser central frequency to tracking the resonance point of theresonator. This method generally relies on laser tuning coefficient and digital-to-analogconverter (D/A), which inevitably produces quantization error and limits frequency-lockingaccuracy and gyro resolution. In addition, the output drift caused by low-frequency noise alsois a problem with long-term lock-in test. In this paper, a novel and simple combinedfrequency-locking technology based on a phase-modulated feedback loop and a laserfeedback loop are proposed. By using the high precision tuning of phase modulator (PM) toimprove the resolution and suppress the low-frequency drift. Furthermore, it has been provedby experiments that the resolution is increased by 10 times, while the frequency-lockingaccuracy is improved from 10°/s to 0.5°/s, by using the combined frequency-locking mode. Inaddition, the low-frequency drift is eliminated with the long-term lock-in of RFOG, and thesystem resolution from 1°/s to 0.1°/s is accurately displayed.

Reusable polymer optical fiber strain sensor withmemory capability based on ABS crazing

Thiago Cabral, Luiz da Silva, Eric Fujiwara, Alson Ng, Heike Ebendorff-Heidepriem, and Cristiano Cordeiro

Doc ID: 376147 Received 23 Aug 2019; Accepted 10 Nov 2019; Posted 11 Nov 2019  View: PDF

Abstract: A reusable memory capable polymer optical fiber (POF) strain sensor is reported. The fiber consists of an ABS coreand PMMA cladding. The memory capability is derived from stress whitening due to crazing of the ABS core, whichcan be reversed by heating the fiber close to the ABS glass transition temperature. The probe was characterizedunder transverse compressive load, macrobending, and tensile loading. Testing shows that the optical propertiesof the fiber can be reversed to near pristine ABS conditions after thermal recovery, and that the POF can be used onthe accurate assessment of indentation, flexural and tensile loading, static or cyclical, even after removal of theload. The reusability of the proposed sensor combined with a deeper understanding of the memory mechanisms inPOFs are of great interest for the development of new large-strain sensors for modern applications.

Elimination of spatial hole burning in solid-statelasers using nanostructured thin films

Jean-Francois Bisson and Koffi Amouzou

Doc ID: 376615 Received 28 Aug 2019; Accepted 09 Nov 2019; Posted 11 Nov 2019  View: PDF

Abstract: Multimode laser emission generally takes place in homogeneously-broadened gain media placed inside a standing-waveresonator due to spatial hole burning. Solutions proposed to eliminate this phenomenon have so far involved the use ofintracavity elements, such as an etalon, waveplates or saturable absorbers. We propose a monolithic solution, whereinbirefringent layers of TiO2 are deposited on both laser mirrors. This solution enables one to control the contrast of theinterference pattern of the standing wave inside the resonator, and thus the strength of the spatial hole burning, by rotatingone mirror around the optical axis. A monochromatic laser emission is demonstrated in a quasi-continuous wave laserdiode-pumped Yb3+: YAG laser experiment.

Lidar remote sensing of the aquatic environment

James Churnside and Joseph Shaw

Doc ID: 379597 Received 08 Oct 2019; Accepted 07 Nov 2019; Posted 07 Nov 2019  View: PDF

Abstract: This paper is a review of lidar remote sensing of the aquatic environment. The optical properties of seawater relevant to lidar remote sensing are described. The three main theoretical approaches to understanding the performance of lidar are considered (time-dependent radiative transfer equation, Monte Carlo simulations, and quasi-single scattering assumption). Basic lidar instrument design considerations are presented, and examples of lidar studies from surface vessels, aircraft, and satellite are given.

MPSK-based SIMO-FSO communication system over gaamma-gamma fading channel and with pointing errors

Suman Malik and Prasant Sahu

Doc ID: 376422 Received 28 Aug 2019; Accepted 07 Nov 2019; Posted 08 Nov 2019  View: PDF

Abstract: The performance of free space optical (FSO) communication system is severely affected due to a number of reason such as atmospheric impairments, fading due to turbulence as well as due to misalignment between transmitter-receiver sections. In this paper, we have analysed the atmospheric turbulence and pointing error effect on M-ary phase shift keying modulation (M-PSK) based FSO system link performance over Gamma-Gamma (G-G) fading channel. In our analysis the effect of weak to strong atmospheric turbulence channel condition and pointing errors are taken into consideration. To deal with the performance degradation, single-input-multiple-output (SIMO) link along with maximal ratio combining (MRC) diversity scheme is employed. The closed-form expressions for the estimation of average bit error rate (BER), outage probability and spectral efficiency (SE) are derived in terms of MeijerG function. The analytical results are presented to show the impact of turbulence and pointing errors on BER. The outage probability and spectral efficiency of the proposed SIMO-FSO system with MRC technique improved significantly

Crosstalk and optical efficiency of an energyharvestingcolor projector utilizing ceramic phosphors

Kohei Yunoki, Ryo Matsumura, TAKAMASA KOHMOTO, masamichi oota, Yasuhiro Tsutsumi, and Ichiro Fujieda

Doc ID: 376878 Received 03 Sep 2019; Accepted 07 Nov 2019; Posted 08 Nov 2019  View: PDF

Abstract: A color projector screen was fabricated by filling three kinds of ceramic phosphor powders in the periodic hollowcolumns formed in a 50 x 50 x 10 mm3 acrylic waveguide. When a blue laser beam excited a single spot on thescreen, a disk-shaped crosstalk pattern appeared. Its intensity was five orders of magnitude lower than that of theexcited spot. The solar cells attached to the waveguide edge harvested less than 0.8 % of the incident opticalpower. The photons scattered by the phosphors are responsible for these characteristics and the use of nonscatteringluminescent materials is desired for improving them.

Comparative Long Time VIS/SWIR Night Illumination Measurements

Jürgen Krieg and Uwe Adomeit

Doc ID: 374829 Received 07 Aug 2019; Accepted 07 Nov 2019; Posted 07 Nov 2019  View: PDF

Abstract: Last decade saw the SWIR spectral range becoming a contender for night vision applications. For this application SWIR sensor performance has to be compared with visual one and knowledge on the illumination in the two ranges becomes necessary. Fraunhofer IOSB started comparative long time assessment of visual and SWIR illumination in 2019. To support this weather data and cloud coverage are additionally measured. A first analysis based on three months of operation is presented. It shows preliminary results of the VIS/SWIR comparison and highlights the problems of artificial light influence and connecting the illumination to environmental effects.

Selective retinex enhancement based on theclustering algorithm and BM3D for OCT images

Yibing Hu, Chen Tang, Min Xu, and Zhenkun Lei

Doc ID: 375626 Received 19 Aug 2019; Accepted 07 Nov 2019; Posted 07 Nov 2019  View: PDF

Abstract: It is important to enhance the contrast and remove the speckle noise for optical coherence tomography (OCT)images. In this paper, we propose a selective retinex enhancement method based on the fuzzy c-means (FCM)clustering algorithm to enhance only the structure part in OCT images, and combines with block-matching 3D(BM3D) algorithm for filtering. In the proposed selective retinex enhancement method, we firstly calculate thefeature image of the original image, which include the mean value and standard deviation of each pixel in theoriginal image and its correlation image. Secondly, by applying the FCM clustering algorithm to the feature image, amask is generated which can distinguish the structure part from the background part in OCT image. Then, the maskis applied to the multi-scale retinex algorithm (MSR), only the structure part in OCT image is enhanced. Moreover,BM3D method is applied to filter the enhanced image. Experimental results demonstrate that the proposed methodperforms impressively in improving the contrast and removing the speckle noise of OCT images, and it providesbetter quantitatively performance in terms of signal-to-noise (SNR), contrast to noise ratio (CNR), equivalentnumber of looks (ENL) and the edge preservation parameter β .

Bubble optics

Markus Selmke

Doc ID: 377762 Received 12 Sep 2019; Accepted 07 Nov 2019; Posted 07 Nov 2019  View: PDF

Abstract: Starting from a peculiar image observed below a bubble floating at a water-air interface, this article analyzes several optical properties of these special types of refracting objects (coined bubble axicons). Using mainly geometrical optics, their relation to common axicons, the shadow sausage effect and elementary optical catastrophes (caustics) are discussed.

Two-Point, Parallel-Beam Focused LaserDifferential Interferometry with a NomarskiPrism

Brett Bathel, Joshua Weisberger, Greg Herring, Rudolph King, Stephen Jones, Richard Kennedy, and Stuart Laurence

Doc ID: 378464 Received 23 Sep 2019; Accepted 07 Nov 2019; Posted 20 Nov 2019  View: PDF

Abstract: A Nomarski polarizing prism has been used in conjunction with a focused laserdifferential interferometer to measure the phase velocity of a density disturbance at samplingfrequencies 10 MHz. Use of this prism enables the simultaneous measurement of densitydisturbances at two closely-spaced points that can be arbitrarily oriented about the instrument’soptical axis. The orientation is prescribed by rotating the prism about this axis. Since all fourbeams (one beam pair at each measurement point) propagate parallel to one another within thetest volume, any bias imparted by density fluctuations away from the measurement plane onthe disturbance phase velocity is minimized. A laboratory measurement of a spark-generatedshockwave and a wind tunnel measurement of a second-mode instability wave on a cone modelin a Mach 6 flow are presented to demonstrate the performance of the instrument. High-speedschlieren imaging is used in both cases to verify the results obtained with the instrument.

Analysis of errors in the polarimetry using rotating waveplate

Yu Liang, Zhong Qu, Yue Zhong, Zhi Song, and Shao Li

Doc ID: 378019 Received 16 Sep 2019; Accepted 06 Nov 2019; Posted 07 Nov 2019  View: PDF

Abstract: Modulation using rotating waveplate is the most popular way in astronomy to obtain the radiation polarization states and thus the physical condition of the celestial bodies. Modulation error analysis of the rotating quater-waveplate polarimeter is presented in this paper. In terms of geometric dimensions, three modulation error sources are analyzed: the waveplate axial error, waveplate rotation axis tip-tilt error(zenith error) and position error of the waveplate fast axis(azimuth error). In theory, two factors will affect the accuracy of polarization measurement using a waveplate polarmetry. One is the retardence δ, the other is the fast axis positon θ. Thetemperature and wavelength properties of the waveplate which represent the axial error, and the waveplate mounting tip-tilt error which represent the zenith error belong to the retardence error δ. The motorized rotary stage home position error and the random sample rotating position error which represent the azimuth error belongs to the fast axis positon θ. These three factors will be analyzed in detail in this paper. Based on these analyses, the maximum allowable upper limits for each error source under 1× 10¯⁴ polarization measurement accuracy are presented. Besides, some feasible solutions are given to deal with these errors.

Implementation and Uncertainty Evaluation ofSpectral Stray Light Correction by Zong's Method

Carsten Schinke, Maximilian Franke, Karsten Bothe, and Saulius Nevas

Doc ID: 375518 Received 16 Aug 2019; Accepted 05 Nov 2019; Posted 05 Nov 2019  View: PDF

Abstract: We present a guide to the implementation and uncertainty evaluation for spectral straylight corrections according to the widely used method as proposed by Zong et al. (Appl. Opt.45, 2006). The uncertainty analysis is based on the Monte-Carlo approach in accordance withthe Guide to the expression of uncertainty in measurement (JCGM, Paris, 2008). We show thatsignificant uncertainty contributions result from drifts of the spectrometer’s dark signal and thewidth of the in-band region selected for shaping stray light distribution functions. Additionally, asimplified method for estimating these uncertainty contributions is presented, which does notrequire a complex Monte-Carlo analysis. We also show that stray light correction may introducecorrelations with respect to wavelength.

Adaptive Spatial-Layout Selection for MassiveMulti-Color Visible Light Communications

Yumeng Zhang, Zhu Yi-Jun, zhang Yan-yu, and Chao Wang

Doc ID: 376020 Received 21 Aug 2019; Accepted 05 Nov 2019; Posted 05 Nov 2019  View: PDF

Abstract: Massive multi-color visible light communications (mMC-VLC) sufficiently utilizing space and color domainresource is proposed to satisfy high spectral-efficiency, high-speed and high density-coverage requirementsof next generation indoor data connection. However, the gap between the number of LEDsand PDs, as well as high correlation among different channels limit the multiplexing of mMC-VLC. Besides,mobility of the receiver is the bottleneck of mMC-VLC. So adaptive spatial-layout selection (ASLS)is proposed to settle the above problems, which selects N sets n-color LEDs from the transmitter to formapproximate optimal circle closed layout adapting to the receiver position. Firstly, the optimal parameterproblems to minimize the ill-condition of activated system under layout constraints of the circle closedand linear are formulated for a fixed receiver position. Secondly, to achieve adaptivity, the fitting curvesof optimal layout parameter and Dv under both constraints are researched, Dv is the vertical distancebetween the transmitter and receiver plane. Finally, the closest layout-selected principle (CLSP) is proposedto solve the problem that the LEDs may not perfectly form optimal parameter layout for mMC-VLC.The bit error ratio (BER) performances and application scopes of ASLS under both layout constraints arecompared to determine that the constraint layout is circle closed, meanwhile the available maximal Ncorresponding to the receiver position is obtained. The optimal parameter of ASLS linearly related to thereceiver position and not related to N. The ASLS always achieves better BER performance than opticalmulti-stream spatial modulation (OMS-SM).

Ellipsometry-based study of glass refractiveindex depth profiles obtained by applyingdifferent poling conditions

Ivana Fabijanić, Petar Pervan, Boris Okorn, Jordi Sancho-Parramon, and Vesna Janicki

Doc ID: 376907 Received 03 Sep 2019; Accepted 05 Nov 2019; Posted 05 Nov 2019  View: PDF

Abstract: Application of electric field and moderately elevated temperature is depleting theside facing anode from alkali present in glasses. The change of composition of the treatedglass results in variation of refractive index depth profile within the treated glass.Spectroscopic ellipsometry is employed for characterization of optical properties of glasstreated in different conditions. The results of optical characterization are verified bysecondary ion mass spectroscopy. It is found that the refractive index profile obtained fromellipsometry has maximum value higher than the one of untreated glass. Obtained refractiveindex profiles are in very good agreement with concentration profiles.

Accurate, Non-differential, Curve-fitted, Self-referenced optical rotation polarimeter

Zeev Weissman and Doron Goldberg

Doc ID: 376956 Received 03 Sep 2019; Accepted 05 Nov 2019; Posted 05 Nov 2019  View: PDF

Abstract: We describe a new method for the accurate measurement of optical rotation. It is based on curve-fitting the signal of a new optical rotation polarimeter that we have recently developed. The calculated accuracy (~80 micro-degrees), and precision (~220 micro-degrees) are potentially useful for various applications in the fields of biomedical devices and analytical chemistry.

High-Extinction Ratio and Ultra-Compact Two-Bit Comparator based on Graphene-PlasmonicWaveguides

Mir Hamid Rezaei and Abbas Zarifkar

Doc ID: 377222 Received 11 Sep 2019; Accepted 05 Nov 2019; Posted 05 Nov 2019  View: PDF

Abstract: Electro-optical one-bit and two-bit comparators based on graphene plasmonicwaveguides are proposed. Surface plasmon polaritons (SPPs) are stimulated by radiation of aTM-polarized light with a wavelength of 15 μm and their propagation is controlled byapplying electrical signals which represent the binary numbers that need to be compared. Theresults of comparing two numbers are obtained in the form of light at the output ports. Finitedifference time domain (FDTD) simulation results show that the minimum extinction ratios(ERs) for one-bit and two-bit comparators are 9.69 dB and 6.13 dB, respectively. Also, theone-bit and two-bit structures have footprints of 0.42 μm2 and 0.9 μm2, respectively. Ourstudies show that the optical comparators with these ultra-compact dimensions have not beenreported so far. The presented structures benefit from high ER and ultra-compact footprintwhich make them suitable for use in optical signal processing and photonic computing.

Dual responsive ‘smart’ window and visuallyattractive coating based on a diarylethenephotochromic dye.

Gilles Timmermans, Barttholomus Saes, and Michael Debije

Doc ID: 378027 Received 15 Sep 2019; Accepted 04 Nov 2019; Posted 06 Nov 2019  View: PDF

Abstract: Controlling the intensity and manipulating the spectral composition of sunlight is critical for many devicesincluding ‘smart’ windows, greenhouses and photomicroreactors, but also important in more decorativeapplications. Here, we use a diarylethene dye incorporated in a liquid crystal host to create a dual-responsive‘smart’ window regulated both by an electrical trigger and by specific wavelengths of light. By incorporating thesame diarylethene dye in a polymerizable host and using inkjet printing, coatings can be made with completefreedom in the applied pattern design, although the electrical response is lost. The color change of the diarylethenedye can be controlled in simulated sunlight by concurrent light exposure from a LED source, allowing a manualoverride for outdoor use. Photoluminescence of the closed isomer of the diarylethene from the lightguide edgescould be used for lighting or electricity generation in a luminescent solar concentrator architecture.

Fuzzy control algorithm for adaptive opticalsystem

Xi-Zheng Ke and DANYU ZHANG

Doc ID: 373914 Received 26 Jul 2019; Accepted 03 Nov 2019; Posted 04 Nov 2019  View: PDF

Abstract: In this study, the direct wavefront gradient algorithm is used to calculate thecontrol voltage of the deflection mirror. Considering the control voltage as the input of thefuzzy controller, the fuzzy rule base is established and the three parameters of theproportional-integral-derivative controller are obtained using double fuzzy control. Inaddition, a weight factor and threshold judgment are included for correcting the controlvoltage and realizing parameter self-tuning. Simulation and experiments demonstrate that thismethod can effectively correct the wavefront distortion signal and improve the systemresponse speed. Moreover, it can reduce the difficulty of parameter adjustment and meet therequirements of laser communication for wavefront correction.

Hybrid Two-Level MPPM-MDPSK Modulation for High Speed Optical Communication Networks

Haitham khallaf, Ahmed Morra, Abdulaziz El-Fiqi, Hossam Shalaby, and Steve Hranilovic

Doc ID: 375073 Received 15 Aug 2019; Accepted 30 Oct 2019; Posted 31 Oct 2019  View: PDF

Abstract: A hybrid optical modulation approach is described, which layers a continuous wave M-ary differential phase shift keying (MDPSK) and a two-level (2L) multipulse pulse-position modulation (MPPM) intensity modulated (IM) signal for improved spectral efficiency. These 2L techniques are a generalization of earlier hybrid MPPM-MDPSK techniques and have the added advantage of reducing transmitter and detector complexities over previous hybrid modulation approaches. The spectral and power efficiencies for the proposed 2L-MPPM-MDPSK modulation techniques are formulated and shown to have the highest spectral efficiency in comparison with otherhybrid techniques with lower implementation complexity. The performance of proposed 2L hybrid techniques is quantified over free-space optical (FSO) networks as well as fiber networks and verified using Monte Carlo (MC)simulation. For FSO channels, the proposed 2L-MPPM–MDPSK technique outperforms traditional MPPM–MDPSK scheme by approximately 2 dB at a BER of 10¨⁴ and a spectral efficiency of 2.5 bit/s/Hz. Similarly, in optical fiber, the proposed scheme relaxes the impact of nonlinearity in comparison to traditional MPPM–MDPSK. Specifically, at a BER = 10¨³ , the 2L-MPPM–DPSK technique outreaches the MPPM–MDPSK by 2000km at a spectral efficiency of 2.5 bit/s/Hz and an average transmit power of -3 dBm.

Analysis of a high sensitive flat fiber plasmonic refractiveindex sensor

Moutusi De and Vinod Kumar Singh

Doc ID: 377466 Received 11 Sep 2019; Accepted 23 Oct 2019; Posted 25 Oct 2019  View: PDF

Abstract: In this report we proposed an efficient double layered flat fiber (DLFF) plasmonic refractive index sensorhaving high resolution and linearity. A thin gold film is used as surface plasmon resonance (SPR) active materialprotected by a titanium dioxide layer, both deposited on the upper flat surface of DLFF. The sensor consists of ananalyte channel in the central core hole as well as on the top of the fiber. Structural parameters of DLFF andthickness of gold and titanium dioxide layer are analyzed based on finite element method (FEM). The optimizedstructure is studied based on wavelength and amplitude interrogation techniques in near infrared region. Numericalresults show average wavelength sensitivity of 12172nm/RIU with resolution 8.21×10-6 RIU (refractive index unit)in the high refractive index (RI) range from 1.445 to 1.490. Also, amplitude sensitivity of this probe is found to be2910 RIU-1 with resolution 3.44×10-6 RIU which is the highest among all reported PCF SPR sensors as per authors’best of the knowledge. Compared to traditional photonic crystal fiber (PCF), the designed DLFF makes the sensorconfiguration simple to fabricate as well as a potential candidate for developing bio-chemical sensors and portabledevices.

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