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Accepted papers to appear in an upcoming issue

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Composite Reflective/Absorptive IR-Blocking Filters Embedded in Metamaterial Antireflection Coated Silicon

Charles Munson, Steve Choi, Kevin Coughlin, Jeff McMahon, Kevin Miller, Lyman Page, and Edward Wollack

Doc ID: 287185 Received 22 Feb 2017; Accepted 26 May 2017; Posted 26 May 2017  View: PDF

Abstract: Infrared (IR) blocking filters are crucial for controlling the radiative loading on cryogenic systems and for optimizing the sensitivity of bolometric detectors in the far-IR. We present a new IR filter approach based on a combination of patterned frequency selective structures on silicon and a thin (50 μm thick) absorptive composite based on powdered reststrahlen absorbing materials. For a 300 K blackbody, this combination reflects ~50% of the incoming light and blocks > 99.8% of the total power with negligible thermal gradients and excellent low frequency transmission. This allows for a reduction in the IR thermal loading to negligible levels in a single cold filter. These composite filters are fabricated on silicon substrates which provide excellent thermal transport laterally through the filter and ensure that the entire area of the absorptive filter stays near the bath temperature. A metamaterial antireflection coating cut into these substrates reduces in-band reflections to below 1%, and the in-band absorption of the powder mix is below 1% for signal bands below 750 GHz. This type of filter can be directly incorporated into silicon refractive optical elements.

Minimum Variance Control for Mitigation of Vibrations in Adaptive Optics Systems

Pedro Escarate, Rodrigo Carvajal, Laird Close, Jared Males, Katie Morzinski, and Juan Agüero

Doc ID: 290177 Received 07 Mar 2017; Accepted 26 May 2017; Posted 26 May 2017  View: PDF

Abstract: In this paper we address the design of a Minimum Variance Controller (MVC) for the mitigation of vibrations in modern telescope’s Adaptive Optics (AO) systems. It is widely accepted that a main source of perturbations is the mechanical resonance induced by the wind or the instrumentation systems, such as fans and cooling pumps. In order to achieve an adequate vibrations mitigation, the application of fre- quency based controllers has been widely considered in the past decade in the literature. In this work, we express the system model in terms of the tracking of a zero-input signal via the MVC and we show that the MVC is an equivalent representation of the LQG controller for the AO system. We also show that by developing the MVC we can obtain different expressions, in terms of transfer functions, that give us insights about the behavior and expected performance of the controller in the frequency domain. In addition, we analyze the impact of the accuracy of the system and perturbations model on the mitigation of vibrations.

Terahertz bistability and multistability ingraphene/dielectric Fibonacci multilayer

Hadiseh Nasari and Mohammad Sadegh Abrishamian

Doc ID: 290244 Received 08 Mar 2017; Accepted 26 May 2017; Posted 26 May 2017  View: PDF

Abstract: Here, we benefit from the strong nonlinear response of graphene and the rich variety of resonances provided by agraphene/dielectric Fibonacci multilayer to realize bistability and multistability in the terahertz (THz) frequencyrange. Toward this pursuit, we employ the nonlinear transfer matrix method (NLTMM). We examine the suitability ofresonances in the Fibonacci multilayer for the bi/multistability purposes and determine the proper working point. Wereport various switching up/down manners via single or stepwise jumps between states of the same or differentcontrasts upon increasing followed by decreasing the intensity of the incident wave. We show that graphene samplesof high quality are preferred for bi/multistable switching in terms of reducing the switch-up/down thresholds andwidening the multistable region. We also explore the possibility of tuning the bi/multistable behavior via thefrequency and angle of the incident wave as well as the graphene Fermi level. We envision precious applications inTHz switching, realizing logic gates and so on for this system.

A calculation model of the Hyperion reflected lightscattering efficiency

jiang xu, weixian qian, Qian Chen, and Yingcheng Lu

Doc ID: 291810 Received 07 Apr 2017; Accepted 26 May 2017; Posted 26 May 2017  View: PDF

Abstract: Remote sensing satellites can provide valuable spatial image data, which plays an irreplaceable role in groundtarget observation. In this paper, we have derived a parameter called the scattering efficiency per unit area (SEA),which is used to describe the ability of different media to change the energy of incident field in the far zone. Overthe range of Hyperion wavelengths, the SEA are unequal, which can be used as the characteristic signal for targetclassification. In order to increase the accuracy of this model, we selected five groups of characteristic bandsunaffected by noise using principal component analysis (PCA). We then combined this with back propagationneural network (BPNN), the identification of five ground media was implemented, and the residuals were very low.These theoretical and experimental analyses verify that SEA can be used as the basis for studying the physicalcharacteristics of scattering of ground targets.

Experimental demonstration of nonlinear enhancement in a graphene-deposited microfiber

Zhihua Tu, Qiang Jin, Hangyu Bai, Xiaoyan Wang, and Shiming Gao

Doc ID: 291897 Received 03 Apr 2017; Accepted 26 May 2017; Posted 26 May 2017  View: PDF

Abstract: The nonlinear enhancement is experimentally demonstrated by depositing graphene scraps from graphene ethanol dispersion onto a tapered microfiber. The enhancement of the nonlinearity is verified by observing the four-wave mixing (FWM) effect in the home-made graphene-deposited microfiber (GDMF). When the incident pump power is 24.2 dBm, the FWM conversion efficiency in the GDMF reaches -57.1 dB. Compared to the bare microfiber with the same dimensions, the conversion efficiency is improved by more than 3 dB. Our fabricated GDMF provides a simple way to enhance the fiber nonlinearity and it will be suitable for nonlinear applications such as wavelength conversion and other optical signal processing operations.

THE COMPOSITE INFRARED SPECTROMETER (CIRS) ON CASSINI

Donald E. Jennings, F. Flasar, Virgil kunde, Conor Nixon, Marcia Segura, Paul Romani, Nicolas Gorius, Shane Albright, John Brasunas, Ronald Carlson, Andrei Mamoutkine, ever guandique, Monte Kaelberer, Shahid Aslam, Richard Achterberg, Gordon Bjoraker, Carrie Anderson, Valeria Cottini, John Pearl, Michael Smith, Brigette Hesman, Richard Barney, Simon Calcutt, Timothy Vellacott, Linda Spiller, Scott Edgington, Shawn Brooks, Peter Ade, Paul Schinder, Athena Coustenis, Regis Courtin, Guy Michel, Rainer Fettig, Stuart Pilorz, and Cecile Ferrari

Doc ID: 291945 Received 12 Apr 2017; Accepted 25 May 2017; Posted 26 May 2017  View: PDF

Abstract: The Cassini spacecraft orbiting Saturn carries the Composite Infrared Spectrometer (CIRS) designed to study thermal emission from Saturn, its rings and moons. CIRS, a Fourier transform spectrometer, is an indispensable part of the payload providing unique measurements and important synergies with the other instruments. It takes full advantage of Cassini’s 13-year-long mission and surpasses the capabilities of previous spectrometers on Voyager 1 and 2. The instrument, consisting of two interferometers sharing a telescope and a scan mechanism, covers over a factor of 100 in wavelength in the mid- and far-infrared. It is used to study temperature, composition, structure and dynamics of the atmospheres of Jupiter, Saturn and Titan, the rings of Saturn and surfaces of the icy moons. CIRS has returned a large volume of scientific results, the culmination of over thirty years of instrument development, operation, data calibration and analysis. As Cassini and CIRS reach the end of their mission in 2017 we expect that archived spectra will be used by scientists for many years to come.

Lp-norm-residual constrained regularization model for estimation of particle size distribution in dynamic light scattering

Xinjun Zhu, Jing Li, John Thomas, Limei Song, Qinghua Guo, and Jin Shen

Doc ID: 291485 Received 27 Mar 2017; Accepted 25 May 2017; Posted 26 May 2017  View: PDF

Abstract: In dynamic light scattering (DLS) particle sizing, noise makes the estimation of the particle size distribution (PSD) from autocorrelation function data unreliable, and a regularization technique is usually required to estimate a reasonable PSD. In this paper, we propose an Lp-norm-residual constrained regularization model for the estimation of the PSD from DLS data based on the Lp norm of the fitting residual. Our model is a generalization of the existing, commonly used L2-norm-residual-based regularization methods such as CONTIN and constrained Tikhonov regularization. The estimation of PSDs by the proposed model using different Lp norms of the fitting residual, including for p=1, 2, 10 and ∞, is studied and their performance is determined using simulated and experimental data. Results show that our proposed model with p=1 is less sensitive to noise and improves stability and accuracy in the estimation of PSDs for unimodal and bimodal systems. The model with p=1 is particularly applicable to the noisy or bimodal PSD cases.

Inversion of oceanographic profiling lidars by a perturbation to a linear regression

James Churnside and Richard Marchbanks

Doc ID: 291137 Received 22 Mar 2017; Accepted 24 May 2017; Posted 26 May 2017  View: PDF

Abstract: We present a simple, robust inversion for oceanographic lidar profiles. A linear regression to the logarithm of the return is followed by a perturbation to obtain a backscatter estimate. For typical thin plankton layer examples, errors are expected to be < 10% over 90% of the ocean. The inversion was applied to lidar data off the coast of Florida, where the correlation between lidar backscatter at 5 m and surface chlorophyll concentration from satellite ocean color measurements was 0.92.

Experimental power spectral density analysis for mid-to-high spatial frequency surface error control

Javier Hoyo, Heejoo Choi, James Burge, Geon-Hee Kim, and Dae Wook Kim

Doc ID: 287787 Received 02 Mar 2017; Accepted 24 May 2017; Posted 26 May 2017  View: PDF

Abstract: The control of surface errors as a function of spatial frequency is critical during the fabrication of modern optical systems. A large scale surface figure error is controlled by a guided removal process, such as computer-controlled optical surfacing. Smaller scale surface errors are controlled by polishing process parameters. Surface errors of only a few millimeters may degrade the performance of an optical system causing background noise from scattered light and reducing imaging contrast for large optical systems. Conventionally, the micro surface roughness is often given by the root mean square (RMS) at a high spatial frequency range, with errors within a 0.5 × 0.5 mm local surface map with 500 × 500 pixels. This surface specification is not adequate to fully describe the characteristics for advanced optical systems. The process for controlling and minimizing mid- to high-spatial frequency surface errors with periods of up to ~2–3 mm was investigated for many optical fabrication conditions using the measured surface power spectral density (PSD) of a finished Zerodur optical surface. Then, the surface PSD was systematically related to various fabrication process parameters such as the grinding methods, polishing interface materials, and polishing compounds. The retraceable experimental polishing conditions and processes used to produce an optimal optical surface PSD are presented.

Characteristics of chiral long-period fiber gratings written in the twisted two-mode fiber by CO2 laser

Xibiao Cao, Yunqi Liu, Liang Zhang, Yunhe Zhao, and Tingyun Wang

Doc ID: 287484 Received 24 Feb 2017; Accepted 23 May 2017; Posted 24 May 2017  View: PDF

Abstract: We demonstrated the fabrication of chiral long-period grating (CLPG) by twisting a two-mode fiber (TMF) when CO2 laser beam was sweeping along the fiber axis. The torsion, temperature and surrounding refractive index characteristics of the fabricated TMF-CLPG were investigated experimentally. The fabricated TMF-CLPG has a high torsion sensitivity (0.7768 nm/(rad/m)), and can measure the twist rate and twist direction simultaneously. This kind of CLPG would have great potential applications in high sensitivity optical sensors.

Diffraction by gratings with random fill factor

Francisco Jose Torcal-Milla and Luis Miguel Sanchez-Brea

Doc ID: 290274 Received 20 Mar 2017; Accepted 23 May 2017; Posted 24 May 2017  View: PDF

Abstract: In this work, we analyze the diffraction produced by Ronchi gratings where the fill factor is not constant, but it presents random fluctuations around its nominal value. This effect can be produced during developing the grating with etchers since the process can be slightly unpredictable. We obtain the theoretical formalism to describe the intensity produced by the grating at near and far field showing that smoothing of the self-images is produced at the near field and, consequently, cancellation of higher diffraction orders is obtained at the far field. In addition, different nominal fill factors produce different diffraction behavior in terms of the randomness. We corroborate the analytical formalism by using a direct integration method based on the Rayleigh-Sommerfeld formula concluding that the numerical results are in high agreement with the theoretical predictions.

Beam modulation due to thermal deformation of grating in spectral beam combining system

Linxin Li, jin yunxia, Fanyu Kong, leilei wang, Junming Chen, and jianda Shao

Doc ID: 290570 Received 23 Mar 2017; Accepted 23 May 2017; Posted 24 May 2017  View: PDF

Abstract: As the combined power of a spectral beam combining (SBC) system increases, temperature of the multilayerdielectric grating (MDG) inevitably rises, under the influence of high-power continuous-wave (CW) laserirradiation. Hence, thermal deformation of the MDG occurs, along with degeneration of the combined beamproperties. In this study, we experimentally and theoretically investigate the influence of the MDG thermaldeformation on the combined beam properties. An experimental setup is first proposed, in which beam quality M2,beam profile, MDG wave-font deformation are investigated. The experimental results indicate that the beamquality clearly degrades and the MDG wave-front deformation becomes more significant with increasing pump-CWpower density. On this basis, a calculation model for MDG thermal deformation in SBC systems is proposed. Theresults indicate that MDG wave-front deformation becomes more significant, combined beam profile deformed andbeam quality of the combined beam degrades with increasing power density. Further, thermal expansion of thesubstrate is a crucial factor that induces MDG wave-front deformation and far-field intensity modulation.

Zonal reconstruction in quadrilateral geometry for phase measuring deflectometry

Lei Huang, Junpeng Xue, Bo Gao, Chao Zuo, and Mourad Idir

Doc ID: 290957 Received 21 Mar 2017; Accepted 23 May 2017; Posted 24 May 2017  View: PDF

Abstract: There are wide applications for zonal reconstruction in slope-based metrology due to its good capability of reconstructing the local details on surface profile. It was noticed in literature that large reconstruction errors occur when using zonal reconstruction methods to process slopes in a quadrilateral geometry, which is a general geometry of slope measured with phase measuring deflectometry. In this work, we present a new idea for the zonal methods used in quadrilateral geometry. Instead of employing the intermediate slopes to set up height-slope equations, we consider the height increment as a more general connector to establish the height-slope equations for least squares regression. Results of both simulation and experiment demonstrate the effectiveness of the proposed idea. In implementation, the modification on the existing zonal methods is addressed. The new methods preserve many good aspects of the existing ones, such as the ability to handle large incomplete slope dataset in an arbitrary aperture, and the low computational complexity comparable with the existing zonal method. Of course, the accuracy of the new methods is much higher when integrating the slopes in quadrilateral geometry.

Grating interferometer for light-efficient spatial coherence measurement of arbitrary sources

Matias Koivurova, Henri Partanen, Jari Turunen, and Ari Tapio Friberg

Doc ID: 291098 Received 21 Mar 2017; Accepted 23 May 2017; Posted 24 May 2017  View: PDF

Abstract: We present a theoretical analysis and experimental verification of a z-scanning double-grating interferometer for spatial coherence measurements in space-frequency and space-time domains. This interferometer permits the measurement of spatial coherence between an arbitrary pair of points along a one-dimensional line, and it has a high light efficiency compared to the classical Young's two-pinhole experiment. The scheme is applicable to both quasimonochromatic and broadband sources that need not obey the Schell model. We first provide experimental results with several narrow-band primary and secondary sources, and then apply the technique to broadband sources with discrete and continuous spectra. In the latter case the complex degree of (time-domain) spatial coherence is retrieved from spectrally resolved measurements using the Friberg-Wolf theorem [Opt. Lett. 20, 6 (1995)]. We compare all results to those obtained with Young's interferometer realized using a digital micromirror device.

Modeling of LED wavefronts for the optimization of transmission holograms

Daniela Karthaus, Markus Giehl, Oliver Sandfuchs, and Stefan Sinzinger

Doc ID: 291121 Received 22 Mar 2017; Accepted 23 May 2017; Posted 24 May 2017  View: PDF

Abstract: The objective of applying transmission holograms in automotive headlamp systems requires the adaptation of holograms to divergent and polychromatic light sources like LEDs. In this paper, four different options to describe the scalar light waves emitted by a typical automotive LED are regarded, including a new approach to determine the LEDs wavefront from interferometric measurements. Computer-generated holograms are designed considering the different LED approximations and recorded into a photopolymer. The holograms are reconstructed with the LED and the resulting images are analyzed to evaluate the quality of the wave descriptions. In this paper we show, that our presented new approach leads to better results with respect to the correlation of the reconstructed to the ideal image in comparison to other wave descriptions. In contrast to the next best approximation, a spherical wave, the correlation coefficient increased by 0.18% at 532nm, 1.69% at 590nm and 0.75% at 620nm.

Lateral Mode Constrictions for Broad-Ridge Quantum Cascade Lasers

Gregory Dente and Michael Tilton

Doc ID: 286708 Received 15 Feb 2017; Accepted 22 May 2017; Posted 23 May 2017  View: PDF

Abstract: We develop a method for analyzing the lateral modes of broad-ridge quantum cascade lasers that incorporate an intra-cavity lateral constriction. The calculations provide results that are in good agreement with the recent data taken on broad-ridge QCLs that incorporate such lateral constrictions. We conclude by providing design principles for broad-ridge quantum cascade lasers that implement an intra-cavity lateral constriction.

Temporal evolution of low-coherence reflectrometry signals in photoacoustic remote sensing microscopy

Kevan Bell, Parsin Haji Reza, Wei Shi, and Roger Zemp

Doc ID: 286888 Received 21 Feb 2017; Accepted 22 May 2017; Posted 23 May 2017  View: PDF

Abstract: Recently a new non-contact reflection-mode imaging modality called photoacoustic remote sensing (PARS) microscopy was introduced providing optical absorption contrast. Unlike previous modalities which rely on interferometric detection of a probe beam to measure surface oscillations, the PARS technique detects photoacoustic initial pressures induced by a pulsed laser at their origin by monitoring intensity-modulations of a reflected probe beam. In this paper a model describing the temporal evolution from a finite excitation pulse is developed with consideration given to the coherence length of the interrogation beam. Analytical models are compared with approximations, finite difference time domain (FDTD) simulations, and experiments with good agreement.

Microscanning in Hadamard spectroscopy

Cristian Damian, Adrian Sima, Tiberius Vasile, and Daniela Coltuc

Doc ID: 288014 Received 03 Mar 2017; Accepted 22 May 2017; Posted 23 May 2017  View: PDF

Abstract: Hadamard spectroscopy is a method of taking spectroscopic measurements suited to domains such as far infrared where sensor noise is dominant. Unfortunately, the signal-to-noise ratio (SNR) of such a system scales poorly with the resolution. In this paper we analyze a technique called microsanning that attempts to solve this problem by combining several lower resolution ``preview' spectra to form a higher resolution spectrum. We provide a theoretical analysis of the method concerning the noise reduction and distortions, we conducted simulations based on the measured far infrared spectra of minerals in order to determine if the noise reduction can outweigh the loss in accuracy caused by a blurring effect and we demonstrate the microscanning method in experimental conditions. We conclude that the microscanning method provides a noise reduction by a factor proportional to the number of ``previews' and that it can prove to be advantageous in far infrared spectroscopy.

On the validity of the integral localized approximation for Bessel beams and associated radiation pressure forces

Leonardo Ambrosio, Jiajie Wang, and Gerard Gouesbet

Doc ID: 288048 Received 03 Mar 2017; Accepted 22 May 2017; Posted 23 May 2017  View: PDF

Abstract: In this paper we investigate the integral version of the localized approximation (ILA) – a powerful technique for evaluating the beam shape coefficients in the framework of the generalized Lorenz-Mie theory (GLMT) – as applied to ideal scalar Bessel beams (BBs). Originally conceived for arbitrary shaped beams with a propagating factor exp(±ikz), it has recently been shown that care must be taken when applying the ILA for the case of ideal scalar BBs, since they carry a propagating factor exp(±ikzcosα), with α being the axicon angle, which cannot be smoothly accommodated into its mathematical formalism. Comparisons are established between the beam shape coefficients calculated from both ILA and exact approaches, assuming paraxial approximation and both on- and off-axis beams. Particular simulations of radiation pressure forces are provided based on the existing data in the literature. This work helps us in elucidating that ILA provides adequate beam shape coefficients and descriptions of ideal scalar BBs up to certain limits and, even when it fails to do so, reliable information on the physical optical properties of interest can still be inferred, depending on specific geometric and electromagnetic aspects of the scatterer

Characterisation and modelling of Fabry-Perot ultrasound sensors with hard dielectric mirrors for photoacoustic imaging

Jens Buchmann, James Guggenheim, Edward Zhang, Chris Scharfenorth, Bastian Spannekrebs, Claus Villringer, and Jan Laufer

Doc ID: 290498 Received 13 Mar 2017; Accepted 22 May 2017; Posted 23 May 2017  View: PDF

Abstract: A Fabry-Perot ultrasound sensor with non-hygroscopic dielectric mirrors made out of Ta2O5 and SiO2 for use in photoacoustic tomography is described. The sensor offers flat frequency response up to 36 MHz, low noise-equivalent pressure (70 Pa) and near-omnidirectional response up to 20 MHz as well as optical transparency for near-infrared illumination. A numerical model was developed to predict its frequency response and the results were validated experimentally. An image of the human palm was acquired to demonstrate in vivo imaging capabilities.

Spherical aberration of optical system and its influence on depth of focus

Antonin Miks and Petr Pokorny

Doc ID: 291653 Received 29 Mar 2017; Accepted 22 May 2017; Posted 23 May 2017  View: PDF

Abstract: The paper analyses the influence of spherical aberration on the depth of focus of symmetrical optical systems for imaging of axial points. A calculation of beam's caustics is discussed using ray equations in the image plane and considering longitudinal spherical aberration as well. Concurrently, the influence of aberration coefficients on extremes of such a curve is presented. Afterwards, conditions for aberration coefficients are derived if the Strehl definition should be the same in two symmetrically placed planes with respect to the paraxial image plane. Such conditions for optical systems with large aberrations are derived with the use of geometric-optical approximation where the gyration diameter of the beam in given planes of the optical system is evaluated. Therefore, one can calculate aberration coefficients in such a way that the optical system generates a beam of rays which has the gyration radius in a given interval smaller than defined limit value. Moreover, one can calculate the maximal depth of focus of the optical system respecting the aforementioned conditions.

A Highly Concentrated, Ring-shaped Phase Conversion LIBS Technology for Liquid Sample Analysis

Lin Qingyu, Zhimei Wei, Hongli Guo, Shuai Wang, Guangmeng Guo, Zhi Zhang, and Yixiang Duan

Doc ID: 281908 Received 15 Dec 2016; Accepted 22 May 2017; Posted 22 May 2017  View: PDF

Abstract: A highly concentrated, ring-shaped phase conversion (RSPC) method was developed for liquid sample analysis using the LIBS technique. In this work, liquid target samples were intensively mixed with polyvinyl alcohol (PVA) solution in its liquid phase, which can be distinguished from other traditional liquid-to-solid conversed methods through the use of a solid supporter. In order to improve the homogeneity of the target elements, the conversion of liquid-to-solid occurs at the same time that the target elements are mixed with the liquid same using the PVA supporter. Meanwhile, a modified glass petri dish was used for the ring-shaped concentration. Due to the specially designed circular groove at the bottom of the glass petri dish, the PVA solution and liquid samples accumulated in the circular groove. The distribution of the target elements was more concentrated, which is beneficial for enhancing the plasma signals and stabilizing the plasma signals compared with a direct liquid sample analysis using LIBS. The limits of detection for Ag, Cu, Cr and Ba obtained with the RSPC-LIBS technology were 0.098 µg•mL-1, 0.18 µg•mL-1, 0.83 µg•mL-1 and 0.046 µg•mL-1, respectively, which were all greatly improved compared to direct bulk liquid analysis using LIBS.

Application of Mobile Laser Induced Breakdown Spectroscopy (LIBS)System to Detect Heavy Metal Elements in Soil

Deshuo Meng, NAN ZHAO, Mingjun Ma, Li Fang, Yanhong Gu, Yao Jia, Jianguo Liu, and Liu Wenqing

Doc ID: 282778 Received 15 Dec 2016; Accepted 22 May 2017; Posted 22 May 2017  View: PDF

Abstract: In this work, a mobile laser induced breakdown spectroscopy (LIBS) system had been successfully applied to in-situ analysis of heavymetals in soil samples. The LIBS system had two working method including fixed measuring and handheld method. For fixed measuringmethod, simple sample pretreatment was needed to reduce soil matrix effect generated by moisture and porosity. Experiments proved thatthis method could be used to semi-quantitative of heavy metals combined traditional calibration curve method. The LODs of copper, leadand zinc were all below 10mg/kg,which satisfied the need of heavy metal detection in soil. Principal Component Analysis (PCA) wasused for soil classification which helped to build appropriate calibration curves. On the basis of soil classification, accurate and rapiddetection of heavy metals in soil is feasible. For handheld method, spectrum intensity and stability decreased significantly compared withthe fixed measuring method. But by using internal standard method, the stability of LIBS data was improved significantly to 6%. And forsoil samples with serious heavy metal pollution, the measurement errors were less than 12% which indicated that handheld LIBS waseffective to monitor heavy metal pollution in soil. The research results provided application supports for rapid and on-site monitoring ofheavy metals in soil.

CHARM-F – a new airborne integrated-path differential-absorption lidar for carbon dioxide and methane observations: measurement performance and methodology to quantify strong point source emission

Axel Amediek, Gerhard Ehret, Andreas Fix, Martin Wirth, Christian Büdenbender, Mathieu Quatrevalet, Christoph Kiemle, and Christoph Gerbig

Doc ID: 284640 Received 11 Jan 2017; Accepted 22 May 2017; Posted 22 May 2017  View: PDF

Abstract: The integrated-path differential-absorption (IPDA) lidar CHARM-F was developed for the simultaneous measurement of the greenhouse gases CO₂ and CH₄ onboard the German research aircraft HALO. The purpose is to derive the weighted, column-averaged dry air mixing ratios of the two gases with high precision and accuracy between aircraft and ground or cloud tops. The paper presents first measurements, performed in spring 2015, and shows performance analyses as well as the methodology for the quantification of strong point sources applied on example cases. A measurement precision of below 0.5% for 20 km averages was found. The detailed analysis of the methane point source emission rate yields plausible results (26 ± 3 m3/min or 9.2 ± 1.15 kt CH4 yr-1), which is in good agreement with reported numbers. In respect of CO₂, a power plant emission could be identified and analysed.

Polarization property changes of optical beam transmission in atmospheric turbulent channels

Jiankun Zhang, Shengli Ding, and Anhong Dang

Doc ID: 291903 Received 03 Apr 2017; Accepted 21 May 2017; Posted 22 May 2017  View: PDF

Abstract: We theoretically analyze and experimentally verify the performance of multiple polarization parameters in the presence of atmospheric turbulence for a terrestrial optical transmission. Firstly, both the first- and second-moment characteristic of polarization parameters are derived based on the extended Huygens-Fresnel principle. Then, numerical simulations are presented for different propagating distances, optical source properties and turbulent strengths. Finally, a series of well-designed experiments are carried out to verify the theory with turbulence-controlled conditions, where the polarization states are measured at two wavelengths respectively. As a result, the theoretical predictions conform closely to the experimental data, and both show that with the increasing turbulent strength, the first-order moment of polarization parameters varies in different trends, while their second-order moment increases. The proposed approach is promising for building a comprehensive statistical model of polarization and improving the performance of free-space optical communication link.

Color aberration improvement depending on the focal length of the lens for automotive headlamps

Hyun Soo Lee, Hyun Jung Park, and Joon Seop Kwak

Doc ID: 292191 Received 05 Apr 2017; Accepted 21 May 2017; Posted 22 May 2017  View: PDF

Abstract: Light emitting diodes (LEDs) are causing big changes in the automotive lighting field. Optical systems with LEDs can use a plastic lens, which means almost all shapes can be made through plastic injection molding. Already, some car manufacturers are adopting this technology in their designs to express their own identities to customers. However, to use this technology, an important defect has to be overcome, which is color aberration near the cut-off line of the low-beam. In this paper, the criteria for measuring the color coordinates are established and simulations for color aberration in the plastic lens are carried out.

Influence of periodic texture profile and parameters for enhanced light absorption in amorphous silicon ultra-thin solar cells

Shereena Joseph and Joby Joseph

Doc ID: 292747 Received 12 Apr 2017; Accepted 20 May 2017; Posted 22 May 2017  View: PDF

Abstract: We have investigated the antireflection and light trapping properties of two-dimensional grating arrays in the hexagonal symmetry with various texture morphologies. Optical simulation based on FDTD analysis is carried out to understand the role of structure profile for different periodicities and heights to achieve enhanced light trapping. The considered active medium of interest is 200 nm thick hydrogenated amorphous silicon. Although the considered texture profiles possesse an incremental change of refractive index from incident medium to active medium, a parabolic shaped front side texture provides better antireflection effects owing to their high diffraction efficiencies in the higher order modes as compared to other pattern morphologies. In the backside texture also, the parabolic shaped pattern dominates with better light trapping efficiencies due to their ability to distribute a major amount of diffracted energy in the higher order modes. The average reflection calculations in the wavelength range of 300-800 nm confirm that in both side texture, a periodicity of 500 nm with height 200 nm can preferentially recommend for less reflection loss and improved scattering in oblique angles. The quantum efficiency calculation verifies that a device designed with these optimised parameters can offer improved efficiency for ultra-thin solar cell.

Infrared optical constants of liquid palm oil and palmoil biodiesel determined by the combinedellipsometry-transmission method

Wang Chengchao, Jianyu Tan, Yunqian Ma, and Lin Hua Liu

Doc ID: 293050 Received 18 Apr 2017; Accepted 20 May 2017; Posted 22 May 2017  View: PDF

Abstract: The optical constants of vegetable oils and biodiesels are the basic input parameters in the study of the thermalradiation transfer, and monitoring the productivity of vegetable oils converting to biodiesels. In this work, acombined ellipsometry-transmission method is presented to obtain the optical constants of palm oil and palm oilbiodiesel between 20 °C and 150 °C in the spectral range 600−4100 cm−1, and study the temperature effect on theoptical constants. In the combined method, a modified ellipsometry method is used to measure the opticalconstants of palm oil and palm oil biodiesel for the whole researched wavebands. For the weak absorption regionsin which the ellipsometry method cannot give precise absorption indices, the transmission method is conducted toget the absorption indices using the refractive indices obtained by the proposed ellipsometry method. Deionizedwater and methanol are taken as examples to verify the combined ellipsometry-transmission method. It is shownthat the combined method can overcome the deficiencies of the traditional ellipsometry and transmission method,which can be used for the measurements of both strong and weak absorption wavebands. The experimentalanalyses indicate that temperature exerts a noticeable influence on the infrared optical constants of palm oil andpalm oil biodiesel. With the increase of temperature, the refractive indices at certain wavenumbers decreasenearly linearly, and the amplitudes of dominant absorption peaks show a decreasing trend. The absorption peakslocated around 3550 cm–1 show blue shift trends as temperature increases. Comparing these two kinds of oils, palmoil presents larger values in refractive indices and dominant absorption peaks.

CEP stable, 5.4 µ J, broadband, mid-infrared pulsegeneration from a 1-ps, Yb:YAG thin-disk laser

Ayman Alismail, Haochuan Wang, Najd Altwaijry, and Hanieh Fattahi

Doc ID: 292848 Received 14 Apr 2017; Accepted 19 May 2017; Posted 19 May 2017  View: PDF

Abstract: We report on a simple scheme to generate broadband, µJ, pulses centered at 2.1µm with an intrinsiccarrier-envelope phase (CEP) stability from the output of a Yb:YAG regenerative amplifier delivering 1-ps pulses with randomly varying CEP. To the best of our knowledge, the reported system has the highestoptical-to-optical efficiency for converting 1-ps, 1µm pulses to CEP stable, broadband, 2.1µm pulses. Thegenerated coherent light carries an energy of 5.4µJ, which can be scaled to higher energy or power byusing a suitable front end, if required. The system is ideally suited for seeding broadband parametricamplifiers and multi-channel synthesizers pumped by picosecond Yb-doped amplifiers, obviating theneed for active timing synchronization. Alternatively, this scheme can be combined with high-poweroscillators with tens of µJ energy in order to generate CEP stable, multioctave supercontinua, suitable forfield-resolved and time-resolved spectroscopy

Optical function of the finite-thickness corrugated pellicle of Euglenoids

Marina Inchaussandague, Diana Skigin, and Andrés Dolinko

Doc ID: 292375 Received 07 Apr 2017; Accepted 19 May 2017; Posted 22 May 2017  View: PDF

Abstract: We explore the electromagnetic response of the pellicle of selected species of Euglenoids. Thesemicroorganisms are bounded by a typical surface pellicle formed by S-shaped overlapping bands whichresemble a corrugated film. We investigate the role played by this structure in the protection of the cellagainst UV radiation. By considering the pellicle as a periodically corrugated film of finite thickness, weapplied the C-method to compute the reflectance spectra. The far field results revealed reflectance peaks witha Q-factor larger than 103 in the UV region for all the illumination conditions investigated. The resonantbehaviour responsible for this enhancement has also been illustrated by near field computations performedby a photonic simulation method. These results confirm that the corrugated pellicle of Euglenoids shieldsthe cell from harmful UV radiation and open up new possibilities for the design of highly UV reflectivesurfaces.

Three-dimensional shape profiling by out of focus projection of colored PWM fringe patterns

Adriana Silva Mejía, Jorge Flores, ANTONIO MUÑOZ, Gastón Ayubi, and Jose Ferrari

Doc ID: 287291 Received 22 Feb 2017; Accepted 19 May 2017; Posted 22 May 2017  View: PDF

Abstract: Three-dimensional shape profiling by sinusoidal phase-shifting methods are affected by the non-linearity of the projector. To overcome this problem, the defocusing technique has become an important alternative to generate sinusoidal fringe patterns. The precision of this method depends on the binary pattern used and on the defocusing applied. To improve the defocusing technique, we propose the implementation of a color-based binary fringe patterns. The proposed technique involves the generation of colored pulse width modulation (PWM) fringe patterns, which are generated with different frequencies at the carrier signal. From an adequate selection of these frequencies, the colored PWM fringe patterns will lead to amplitude harmonics lower than the conventional PWM fringe patterns. Hence, the defocusing can decrease, and the 3D shape profiling can be more accurate. Numerical simulations and experimental results are presented as validation.

Formation of silver nanoparticles in Li₂B₄O₇-Ag₂O and Li₂B₄O₇-Gd₂O₃-Ag₂O borate glasses

Volodymyr Adamiv, Roman Gamernyk, and Ihor Teslyuk

Doc ID: 291099 Received 21 Mar 2017; Accepted 19 May 2017; Posted 22 May 2017  View: PDF

Abstract: Results of investigations of 98.0Li₂B₄O₇–2.0Ag₂O and 97.0Li₂B₄O₇–2.0Ag₂O–1.0Gd₂O₃ glasses with Ag nanoparticles (Ag NPs), formed by thermal treatment in vacuum and in air, are presented. Intensive plasmon absorption bands, connected with Ag NPs, were observed in their optical transmission spectra. It is ascertained that in volumes of both glasses there is formed a small number of Ag NPs, whereas their main mass is concentrated near the surface of samples. Mechanism of Ag NPs formation is proposed. A conclusion is drawn that annealing in vacuum does not necessarily requires the presence of reducing ions, whereas formation of nanoparticles at annealing in air is impossible without reducing agents. Structural defects play decisive role in the Ag NPs nucleation process. Radii of formed Ag NPs are estimated by half-width of plasmon bands, and by means of small-angle X-ray scattering.

Comparison of III-V/Si On-chip Lasers with Etched Facet Reflectors

Chee-Wei Lee, Doris Ng, Min Ren, Yuan Hsing Fu, Yew Seng Kay, Vivek Krishnamurthy, Jing Pu, Ai Ling Tan, Choo Soo Bin, and Qian Wang

Doc ID: 291819 Received 31 Mar 2017; Accepted 18 May 2017; Posted 19 May 2017  View: PDF

Abstract: Electrically-pumped heterogeneously integrated III-V/SiO2 semiconductor on-chip lasers with different types of etched facet reflectors are designed, fabricated and their lasing performance is characterized and compared. The III-V quantum-well based epitaxial layers are bonded on silica-on-silicon substrate and fabricated to form Fabry-Perot (FP) lasers with dry-etched rear facets. Three types of reflectors are demonstrated, which are etched facets terminated by air, Benzocyclobutene (BCB) and metal with a thin layer of SiO2 insulator in-between. The laser devices are characterized and compared including lasing threshold, external quantum efficiency and output power, which shows the impact of different types of etched facet reflectors on lasing performance.

Sol-gel zirconia diffraction grating using a soft imprinting process

Itsunari Yamada and Yusuke Ikeda

Doc ID: 283555 Received 24 Feb 2017; Accepted 18 May 2017; Posted 18 May 2017  View: PDF

Abstract: A zirconia diffraction grating with high diffraction efficiency was fabricated using a soft imprinting technique and a sol-gel method. The imprinting process involved dropping zirconia nanoparticle dispersion onto a silicone (polydimethylsiloxane) mold, which was transferred from the patterned photoresist grating through the molding process. The first-order diffraction transmittance of the fabricated grating with a 1.0-μm-pitch and a depth of 0.58 µm reached 29.4% at a wavelength of 632.8 nm (zeroth-order transmittance: 13.8%). This high aspect ratio grating can be fabricated in a simpler manner and at lower cost compared with conventional gratings.

High power, cladding-pumped all-fiber laser with selective transverse mode generation property

Lei Li, meng wang, Tong Liu, Jinyong Leng, Pu Zhou, and Jinbao Chen

Doc ID: 285470 Received 23 Jan 2017; Accepted 18 May 2017; Posted 18 May 2017  View: PDF

Abstract: We demonstrate the first cladding pumped all-fiber oscillator configuration with selective transverse mode generation based on a mode-selective fiber Bragg grating pair. Operating in the second order (LP11) mode, the slope efficiency is about 38% with maximum output power of 4.2 W. To the best of our knowledge, this is the highest reported output power of single higher-order transverse mode generation in all-fiber configuration. The intensity distribution profile and spectral evolution also have been investigated in this paper. Our work suggests the potential of realizing higher power with selective transverse mode operation based on a mode-selective fiber Bragg grating pair.

High-order mode conversion based on adiabatical mode evolution for mode division multiplexing applications

Ming-Yang Chen, Guo Cao, Yan-Qun Tong, and Ling Wang

Doc ID: 294883 Received 01 May 2017; Accepted 17 May 2017; Posted 18 May 2017  View: PDF

Abstract: Mode conversion based on adiabatical mode evolution in a two-core configuration is investigated. In addition to the mode conversion between the fundamental mode and high-order mode, mode conversion can also be achieved between two high-order modes. Mode conversion between the two degenerated high-order modes is also demonstrated numerically. The mode conversion feature is only dependent on the relationship between the effective mode indexes of the two cores in the configuration, which shows the high flexible characteristics of the configuration and large fabrication tolerance.

Impact of a Counter-Rotating Planetary Rotation System on Thin-Film Thickness and Uniformity

James Oliver

Doc ID: 287872 Received 02 Mar 2017; Accepted 17 May 2017; Posted 17 May 2017  View: PDF

Abstract: Planetary rotation systems incorporating forward- and counter-rotating planets are used as a means of increasing coating-system capacity for large oblong substrates. Comparisons of planetary motion for the two types of rotating systems are presented based on point tracking for multiple revolutions, as well as comparisons of quantitative thickness and uniformity. Counter-rotation system geometry is shown to result in differences in thin-film thickness relative to standard planetary rotation for precision optical coatings. This systematic error in thin-film thickness will reduce deposition yields for sensitive coating designs.

A novel full-duplex Radio over Fiber system with tunable millimeter-wave signal generation and wavelength reuse for upstream signal

yiqun wang, Li Pei, Jing Li, and Yueqin Li

Doc ID: 291256 Received 27 Mar 2017; Accepted 17 May 2017; Posted 17 May 2017  View: PDF

Abstract: A full-duplex Radio-over-Fiber system is proposed, which provides both the generation of millimeter-wave (mmwave)signal with tunable frequency multiplication factors (FMFs) and the wavelength reuse for uplink data. ADual-driving Mach-Zehnder Modulator and a phase modulator are cascaded to form an optical frequency comb. Anacousto-optic tunable filter based on uniform fiber Bragg grating (FBG-AOTF) is employed to select three targetoptical sidebands. Two symmetrical sidebands are chosen to generate mm-waves with tunable FMFs up to 16,which can be adjusted by changing frequency of the applied acoustic wave. The optical carrier is reused at the basestation for uplink connection. FBG-AOTFs driven by two AW signals are experimentally fabricated and furtherapplicated in the proposed scheme. Results of the research indicate that the 2-Gbit/s data can be successfullytransmitted over 25km single mode fiber for bidirectional full-duplex channels with power penalty of less than2.6dB. The feasibility of the proposed scheme is verified by detailed simulations and partial experiments.

Efficient generation of vector beams by calibrating the phase response of spatial light modulator

yi zhang, Peng Li, Chaojie Ma, Sheng Liu, Lei han, huachao cheng, and Jianlin Zhao

Doc ID: 291495 Received 28 Mar 2017; Accepted 16 May 2017; Posted 17 May 2017  View: PDF

Abstract: The spatial light modulator (SLM) is considered as an effective device to create beams with inhomogenous phases and polarizations, such as vortex beams, vector beams and so on. However, the nonlinear responses of SLM severely reduce the generation efficiency of these beams. In this paper, by calibrating the SLM to present linear phase response in the scope of 0-2π, we propose a convenient and efficient method of creating vector beams with arbitrary polarizations based on phase encoding. Compared with the common methods of generating vector beams, our approach can distinctly enhance the generation efficiency.

Monitoring stress changes in carbon fiber reinforced polymer composites with GHz radiation

Peter Schemmel and Andrew Moore

Doc ID: 292340 Received 12 Apr 2017; Accepted 16 May 2017; Posted 17 May 2017  View: PDF

Abstract: We performed proof of principle experiments to demonstrate that the reflected power of GHz illumination from the surface of carbon fiber reinforced polymer (CFRP) composites is linearly related to the stress in the material. We introduce a stress coefficient to describe the change in normalized power with applied stress, because the effect is attributed partially to changes in the refractive index of the effective medium comprising the carbon fibers in the polymer matrix. The stress coefficient was -0.549 ± 0.134 /GPa for 3 mm thick samples, and -0.154 ± 0.024 /GPa for 1 mm thick samples, both linear up to the measurement limits of 40 MPa and 100 MPA respectively. This technique opens up the possibility of non-destructive evaluation of stresses in CFRP components for quality assurance in manufacturing settings as well as structural health monitoring of in-service aerospace and automotive parts.

Optical design and fabrication of palm/fingerprintuniform illumination system with a high power nearinfrared LED

Lei Jing, wang yao, Huifu Zhao, Hong-Liang Ke, Xiaoxun Wang, and Qun Gao

Doc ID: 292760 Received 12 Apr 2017; Accepted 16 May 2017; Posted 17 May 2017  View: PDF

Abstract: In order to meet the requirements of uniform illumination for optical palm/fingerprint instrument and overcome the shortcomings of the poor uniform illumination on the working plane of optical palm/fingerprint prism, a novel secondary optical lens with high power near infrared LED, compact structure and high uniformity is presented in this paper. The design of secondary optical lens is based on emission property of the near infrared LED and basic principles of non-imaging optics, especially considering the impact of the thickness of the prism in the design. Through the numerical solution of the Snell's Law in geometric optics, we obtain the profile of the free-form surface of lens. Using the optical software TracePro, we trace and simulate the illumination system. The results show that the uniformity is 89.8% on the working plane of the prism. And the test results show that the actual uniformity reaches 85.7% in experiment, which provides an effective way for realizing high uniform illumination system with high power near infrared LED.

Bicontinuity Analysis of Multi-Beam InterferenceThree-Dimensional Periodic Structures:Volume Fractions and Interface Areas

Shruthi Kumara Vadivel, Matthieu Leibovici, and Thomas Gaylord

Doc ID: 290722 Received 20 Mar 2017; Accepted 16 May 2017; Posted 17 May 2017  View: PDF

Abstract: Bicontinuous structures are an important subset of three-dimensional periodic structures. In multi-beaminterference structures, the conditions for bicontinuity depend on the beam parameters and the exposure dose. Asdescribed in the present work, these conditions can be applied to establish the range of bicontinuity for any multibeam-interference-produced structure. In addition to the bicontinuity range, the analysis yields the volumefraction of the constituent materials and the normalized interface areas. This analysis has been performed forrhombohedral and woodpile lattices as well as their cubic structure limiting cases. A sphere-at-each-lattice-sitemodel for each of the cubic cases has also been developed for comparison. The multi-beam interference structureswere investigated for representative media and for various incident polarizations.

Optical electric field sensor sensitivity direction rerouting and enhancement using a passive integrated dipole antenna

Frederick Seng, Zhenchao Yang, Rex King, LeGrand Shumway, Nikola Stan, Alec Hammond, Karl Warnick, and Stephen Schultz

Doc ID: 288058 Received 07 Mar 2017; Accepted 16 May 2017; Posted 16 May 2017  View: PDF

Abstract: This work introduces a passive dipole antenna integrated into the packaging of a slab coupled optical sensor in order to enhance the directional sensitivity of electro-optic electric field measurements parallel to the fiber axis. Using the passive integrated dipole antenna described in this work, a sensor that typically can only sense fields transverse to the fiber direction is able to sense a 1.25 kV/m field along the fiber direction with a gain of 17.5. This is verified through simulation and experiment.

Internal stray radiation measurement for cryogenic infrared imaging systems using a spherical mirror

Qijie Tian, Songtao Chang, Feng-Yun He, Li Zhou, and Yanfeng Qiao

Doc ID: 290633 Received 14 Mar 2017; Accepted 15 May 2017; Posted 16 May 2017  View: PDF

Abstract: Internal stray radiation is a key factor that influences infrared imaging systems and its suppression level is an important criterion to evaluate the system performance, especially for cryogenic infrared imaging systems which are highly sensitive to thermal sources. In order to achieve the accurate measurement for internal stray radiation, an approach, which is based on radiometric calibration, is proposed using a spherical mirror. First of all, the theory of spherical mirror design is introduced. Then, the calibration formula considering the integration time is presented. Following this, the details regarding the measurement method is presented. By placing a spherical mirror in front of the infrared detector, the influence of internal factors of detector on system output can be obtained. According to the calibration results of the infrared imaging system, the output caused by internal stray radiation can be acquired. Finally, several experiments are performed in a chamber with controllable inside temperatures to validate the theories proposed in this paper. Experimental results show that the measurement results are in great accordance with the theoretical analysis, and demonstrate that the proposed theories are valid and can be employed in practical applications. The proposed method can achieve accurate measurement for internal stray radiation at arbitrary integration times and ambient temperatures, and the measurement result can be used to evaluate whether the suppression level meets the system requirement.

Large visual field with low cost pyroelectric infrared linear device

yu yang and Yuanqing Wang

Doc ID: 283525 Received 22 Dec 2016; Accepted 15 May 2017; Posted 16 May 2017  View: PDF

Abstract: In this paper, the large visual field with low cost pyroelectric infrared linear device that fabricated using multi-sensor was reported. The multi-sensor has been fabricated by connecting five unit-sensor to flexible circuit whose substrate is polyethylene terephthalate (PET) film. The fabrication process of pyroelectric sensor, microstructure, sensor electric properties, and device performance were studied. In order to obtain a larger visual field, the multi-sensor has been bent a specific angle, the visual field angle( more than 180°)of the device can much larger than traditional linear device(132°) and it made the detection capability of the pyroelectric infrared linear device improved greatly with lower cost than the other ways.

Dual square-wave pulse passively mode-locked fiberlaser

Qingchao Su, Tianshu Wang, Jing Zhang, Wanzhuo Ma, Peng Liu, Yuwei Su, and Qingsong Jia

Doc ID: 291621 Received 04 Apr 2017; Accepted 15 May 2017; Posted 15 May 2017  View: PDF

Abstract: We study a passively mode-locked square-wave pulse (SWP) fiber laser with a nonlinear amplifying loop mirror(NALM) in the cavity. The net dispersion of the cavity is about 0.68ps2 and SWP mode-locked fiber laser can berealized. The peak power of SWP hardly varies and the pulse duration gets expanded with the increasing pumppower. SWPs breaking in the low nonlinear cavity can be observed and the stable dual SWP can be achieved inthe experiment. When the total pump power stays at 800mW, the interval of dual pulses is 41 ns. The widths ofdual SWPs are both 1.5 ns. The output power rises linearly with the increasing of the pump power, while theinterval of dual SWPs is almost constant. Then, the physical mechanism of the SWP breaking and vector nature ofthe pulse are analyzed.

Mode properties in metallic and non-metallic plasmonic waveguides

Wanwan Liu, Yifu Chen, Hu xin, Long Wen, Lin Jin, qiang Su, and Qin Chen

Doc ID: 292405 Received 11 Apr 2017; Accepted 14 May 2017; Posted 15 May 2017  View: PDF

Abstract: Non-metallic plasmonic materials have recently attracted research interests due to the adjustable plasmonicmaterial properties and the potential low loss, which is important to plasmonic waveguides with ultrahigh modeconfinement. In this paper, the mode properties of four types of plasmonic waveguides based on noble metals,aluminum-zinc-oxide (AZO) and TiN were analyzed, where the propagation length and the mode size are chosen tocompare the figure of merits. It is found that AZO has the smallest imaginary part of the permittivity in the nearinfrared region, while the AZO waveguides have comparable propagation length as Cu ones but shorter than Auand Ag ones. Furthermore, due to the larger real part of permittivities the mode sizes of the AZO and TiNwaveguides are smaller than the metal ones, in particular for insulator-metal-insulator waveguide and dielectricloaded plasmonic waveguide. AZO/ZnO films were grown by pulsed laser deposition with tunable carrier densitybetween 1.8×1017/cm3 and 8.6×1020/cm3. Metal-like property, i.e. negative real part of the permittivity around1550 nm were observed, predicting an interesting candidate in plasmonic optical interconnect.

Analytical model of Amplified Spontaneous Emission with different thickness anti-ASE cap for thin disk lasers

Yu Qiao, Xiao Zhu, Guangzhi Zhu, Yongqian Chen, Wenguang Zhao, and Hailin Wang

Doc ID: 287927 Received 02 Mar 2017; Accepted 13 May 2017; Posted 15 May 2017  View: PDF

Abstract: The Amplified Spontaneous Emission (ASE) effect is a major factor affecting large size, high gain Yb:YAG thin disk lasers. In this paper, the analytical model is built to estimate the ASE photon flux density of thin disk crystal with different thickness of anti-ASE cap. Theoretical analysis shows that it is unnecessary to use critical thickness anti-ASE cap to suppress ASE effect. At the same time, adjusting the coupler reflectivity of the resonator is an effective way to decrease the ASE effect and decrease the thickness of anti-ASE cap to suppress ASE effect effectively. It will be better to reveal the function of anti-ASE cap for suppressing ASE effect.

Research on surface damage induced by combined millisecond and nanosecond laser

Xueming Lv, Yunxiang Pan, ZhiChao Jia, Li Zewen, and Xiaowu Ni

Doc ID: 287565 Received 27 Feb 2017; Accepted 13 May 2017; Posted 16 May 2017  View: PDF

Abstract: The surface damage morphologies of single crystal silicon induced by combined pulse laser (CPL) andsingle millisecond laser are investigated, respectively. CPL includes a millisecond (ms) laser superposed bya nanosecond (ns) laser. Inspected by an optical microscope (OM), it was found that the surface damagewas more serious when the sample was irradiated by CPL than by a single ms laser with the same incidentlaser energy. Besides surface cleavage, obvious ablation and fold areas were discovered by CPL irradiation.A two-dimensional spatial axisymmetric model was established to assess the difference between single mslaser and CPL irradiation and explain the generation mechanism of the different surface damage. Thatwas attributed to the pre-heating effect by the ms laser and the surface damage caused by the ns laser.

Time-domain measurements reveal spatial aberrations in a sub-surface two-photon microscope

Marius Rutkauskas, Derryck Reid, Jesus Garduno-Mejia, and Martha Rosete-Aguilar

Doc ID: 282428 Received 17 Feb 2017; Accepted 13 May 2017; Posted 15 May 2017  View: PDF

Abstract: We show that in a nonlinear microscopy system the effects of chromatic and spherical aberrations are revealed by a difference in the focal positions corresponding to the shortest pulse duration and the minimum lateral resolution. By comparing experimental results from a high-numerical-aperture two-photon microscope with a spatio-temporal simulation, we conclude that the two-photon autocorrelation of the pulses at the focal plane can be used to minimize both the chromatic and spherical aberrations of the system. Based on these results, a possible optimization strategy is proposed whereby the objective lens is first adjusted for minimum autocorrelation duration, then the wavefront before the objective is modified to maximize the autocorrelation intensity

Absolute detector-based spectrally tunable radiantsource using DMD and supercontinuum fiber laser

Futian Li and Zhigang Li

Doc ID: 285610 Received 31 Jan 2017; Accepted 12 May 2017; Posted 15 May 2017  View: PDF

Abstract: High accuracy absolute detector-based spectroradiometric calibration techniques traceable to cryogenic absoluteradiometers make progress rapidly in recent decades under the impetus of atmospheric quantitative spectral remotesensing. A high brightness spectrally tunable radiant source using supercontinuum fiber laser and digital micromirrordevice (DMD) has been developed in order to meet demands of spectroradiometric calibrations for ground-based,aeronautics-based, and aerospace-based remote sensing instruments and spectral simulations of natural scenes such as thesun and atmosphere, etc. Due to supercontinuum fiber laser used as radiant source, the spectral radiance of the spectrallytunable radiant source is 20 times higher than the spectrally tunable radiant source using conventional radiant sources suchas tungsten halogen lamps, Xenon lamps or LED lamps and the stability is better than±0.3%/h. Due to the use of DMD, thespectrally tunable radiant source possesses two working modes. In narrow-band modes, it is calibrated by an absolutedetector and in broad-band modes, it can calibrate for remote sensing instrument. The uncertainty of the spectral radianceof the spectrally tunable radiant source is estimated less than 1.87% at 350nm to 0.85% at 750nm and compared with onlystandard lamp-based calibration, a greater improvement is gained.

Atmospheric Optics in the Near Infrared

Michael Vollmer and Joseph Shaw

Doc ID: 286561 Received 13 Feb 2017; Accepted 12 May 2017; Posted 15 May 2017  View: PDF

Abstract: Digital near infrared photography opens up new observation possibilities and applications for atmospheric optics. We discuss necessary conditions and requirements for observing a variety of atmospheric optical phenomena in the infrared spectral range and report for the first time near infrared photographs of 22° ring halos and inferior mirages. Our emphasis is on optical phenomena observable in the troposphere, excluding the large body of work addressing near infrared airglow and aurora.

Multiple spontaneously generated coherence and phase control of optical bistability and mutilstability in tripod four-level atomic medium

Huijing Li, Hongjun Zhang, Sun Hui, Xionghui Hu, Dong Sun, and Ximei Li

Doc ID: 287054 Received 21 Feb 2017; Accepted 12 May 2017; Posted 15 May 2017  View: PDF

Abstract: Optical bistability (OB) and optical mutilstability (OM) behavior induced by multiple spontaneously generated coherence (SGC) are investigated theoretically in a tripod four-level atomic scheme. It is found that, OB or OM is sensitive to the SGC effects, and the thresholds of OB can be controlled via changing the strength of multiple SGC or the relative phases of the applied fields. In addition, we can switch OB to OM by adjusting the twofold relative phase of the applied fields or vice versa.

Interferometric synthetic aperture ladar using code division multiple access apertures

Andrew Stokes, Matthew Dierking, and David Rabb

Doc ID: 290662 Received 14 Mar 2017; Accepted 12 May 2017; Posted 15 May 2017  View: PDF

Abstract: This paper describes a multi-static interferometric synthetic aperture ladar (IFSAL) for high resolution, high precision 3D imaging. Code division multiple access apertures with periodic, pseudorandom noise waveforms are used to create aperture diversity and overcome the ambiguity associated with the aperture separation requirements for interferometric synthetic aperture ladar. The basic theory for mapping relative aperture phase to a high precision elevation profile is derived for a multi-static IFSAL system and subsequent processing steps are presented. An analytic model and computer simulation are developed to demonstrate the 3D imaging capability of an IFSAL system.

Interfaces with fractional optical constants and linearreflectance versus angle of incidence for incidentunpolarized or circularly polarized light

Rasheed Azzam

Doc ID: 290879 Received 17 Mar 2017; Accepted 11 May 2017; Posted 11 May 2017  View: PDF

Abstract: For unpolarized or circularly polarized light incident at a dielectric-conductor interface, the intensityreflectance Ru (φ ) can be made an essentially linear function of the angle of incidence φ over a significantrange of φ at specific values of the normal-incidence intensity reflectance R0 ( ≈ 1/ 3 ) and the associatednormal-incidence reflection phase shift δ 0 ( ≈ 40 ). This places the complex refractive index n ̶ jk of theinterface in the domain of fractional optical constants. As demonstrated by specific examples, this isrealizable in external reflection at vacuum-metal interfaces in the UV, and in internal reflection in the IR atinterfaces between a transparent high-index substrate and an optically opaque thin film of the proper n andk. Fractional optical constants are also achievable for light reflection in air at planar surfaces ofappropriately designed, nanostructured, metamaterial substrates.

A general filtering method for ESPI fringe images with various densities baesed on variational image decomposition

Biyuan Li, Chen Tang, Guannan Gao, Mingming Chen, Shuwei Tang, and Zhenkun Lei

Doc ID: 285919 Received 31 Jan 2017; Accepted 10 May 2017; Posted 10 May 2017  View: PDF

Abstract: Filtering off speckle noise from a fringe image is one of the key tasks in electronic speckle pattern interferometry (ESPI). In general, ESPI fringe images can be divided into three categories: low-density fringe images, high-density fringe images and variable density fringe images. In this paper, we firstly present a general filtering method based on variational image decomposition (VID) that is able to filter speckle noise for ESPI fringe images with various densities. In our method, a variable density ESPI fringe image is decomposed into low-density fringe, high-density fringe and noise. The low-density and high-density ESPI fringe images can be regarded as the special cases of variable density ESPI fringe image. We give some suitable function spaces to describe low-density fringe, high-density fringe and noise, respectively. Then we construct several models and numerical algorithms for ESPI fringe images with various densities. And we investigate the performance of these models via our extensive experiments. Finally, we compare our proposed models with windowed Fourier transform method (WFT) and coherence enhancing diffusion partial differential equation filter (CEDPDE). These two methods may be the most effective filtering methods at present. Furthermore, we use the proposed method to filter a collection of the experimentally obtained ESPI fringe images with poor quality. The experimental results demonstrate the performance of our proposed method.

An upconversion photoluminescence of coreshellstructured SiO2@YVO4:Yb3+,Er3+,Eu3+nanospheres

Yuan Cheng and Kangning Sun

Doc ID: 286733 Received 17 Feb 2017; Accepted 10 May 2017; Posted 10 May 2017  View: PDF

Abstract: Core-shell structured SiO2@YVO4:Yb3+,Er3+,Eu3+ nanospheres were prepared by a simple sol-gelmethod followed by a subsequent heat treatment.The as-prepared composites were characterized byscanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM),X-raydiffraction(XRD) and photo luminescent spectra(PL spectra).Besides,the influences of different coatingnumbers were also studied.To sum up,the composites are spherical shape with an average diameter of200nm,and the YVO4:Yb3+,Er3+,Eu3+ luminescent particles are successfully coated on the surface of SiO2nanospheres.Under the NIR irradiation at 980nm, the composites can emit strong green lights(at525nm,550nm) attributed to the 2H11/2→4I15/2,4S3/2→4I15/2 transitions of Er3+ ions,and slight red lights(at590nm, 620nm) attributed to the 5D0→7F1,5D0→7F2 transitions of Eu3+ ions.Given the above,due to the regularcore-shell structure,the uniform distribution of nanoparticles and the colorful emissions,theSiO2@YVO4:Yb3+,Er3+,Eu3+ nanospheres may have great potential for some biological applications,such asbiological tracer, bio-labeling and so on.

Intrinsic Decomposition From A Single Spectral Image

Xi Chen, Weixin Zhu, Yang Zhao, Yao Yu, Tao Yue, Sidan Du, Xun Cao, and yu zhou

Doc ID: 290223 Received 07 Mar 2017; Accepted 10 May 2017; Posted 10 May 2017  View: PDF

Abstract: In this paper, we present a Spectral Intrinsic Image Decomposition (SIID) model, which is dedicated to resolve a natural scene into its purely independent intrinsic components: illumination, shading and reflectance. By introducing spectral information, our work can solve many challenging cases such as scenes with metameric effects which are hard to tackle for trichromatic intrinsic image decomposition (IID), and thus offers potential benefits to many higher-level vision tasks, e.g., materials classification and recognition, shape-from-shading, and spectral image relighting. A both effective and efficient algorithm is presented to decompose a spectral image into its independent intrinsic components. To facilitate future SIID researches, we present a public dataset with ground-truth illumination, shading, reflectance and specularity and a meaningful error metric, so that the quantitative comparison becomes achieveable. The experiments on this dataset and other images demonstrate the accuracy and robustness of proposed method on diverse scenes, and reveal that more spectral channels indeed facilitate the vision task (i.e., segmentation and recognition)

Compact polarization rotator for silicon-based cross-slot waveguides using subwavelength gratings

Jinbiao Xiao and Shengbao Wu

Doc ID: 291254 Received 23 Mar 2017; Accepted 10 May 2017; Posted 10 May 2017  View: PDF

Abstract: A compact and broadband polarization rotator (PR) for silicon-based cross-slot waveguides using subwavelength gratings (SWGs) is proposed and analyzed. To significantly break the symmetry of the waveguide structure, the diagonal regular Si wires of the cross-slot waveguides are replaced with the full etching SWGs. Moreover, the dramatic properties of the SWGs whose effective index is adjustable can effectively enhance the modal birefringence between the two lowest-order hybrid modes, resulting more compact device footprint. By utilizing the interference effect of hybrid modes, both TE-to-TM and TM-to-TE conversion can be efficiently realized. Numerical results show that a PR with a length of 12.6μm at the wavelength of 1.55μm is achieved, where the polarization conversion efficiency (PCE) and insertion loss (IL) are, respectively, 97.2% and 0.71 dB, and the reflection loss is below -20.5dB for both cases. Moreover, a wide bandwidth of ∼260 nm for both polarizations is obtained for keeping the PCE over 90% and IL lower than 1dB. In addition, fabrication tolerances to the structural parameters are investigated, and field evolution along the propagation distance is also presented.

Tolerance of holographic polymer-dispersed liquidcrystal memory for gamma-ray irradiation

Akifumi Ogiwara, Minoru Watanabe, and Yoshizumi Ito

Doc ID: 286384 Received 08 Feb 2017; Accepted 10 May 2017; Posted 11 May 2017  View: PDF

Abstract: The radiation-hardened characteristics of holographic polymer-dispersed liquid crystal (HPDLC) memory arediscussed in the application for an optically reconfigurable gate array. The radiation experiments are conductedusing a cobalt 60 gamma radiation source to examine the tolerance of 100 Mrad total-ionizing-dose for the HPDLCmemory. The optical properties are compared in the conditions before and after the irradiation of gamma-ray forthe fabricated HPDLC gratings. The effects of irradiation of gamma-ray on the internal grating structure are alsoinvestigated by the polarization optical microscopy (POM) and scanning electron microscopy (SEM) observations.The HPDLC memory irradiated by 100 Mrad total ionizing dose demonstrates the implementation of the opticalreconfiguration in the gate-array VLSI.

Extended shift-rotation method for absoluteinterferometric testing of spherical surface with pixellevelspatial resolution

Yu Liu, Liang Miao, Wenlong Zhang, Chun-shui Jin, and Haitao Zhang

Doc ID: 290379 Received 14 Mar 2017; Accepted 10 May 2017; Posted 11 May 2017  View: PDF

Abstract: An improved shift-rotation method for the absolute testing of spherical surfaces is developed to obtain pixel-level spatial resolution and lownoise propagation ratio. The absolute testing process includes multiple rotational tests and two lateral shifting tests with large shifts. Awavefront reconstruction algorithm based on sub-aperture division and least square fitting is proposed to reconstruct the surface figure of thetest optics. Numerical simulation results show that the method reveals high-frequency figures missed in the traditional Zernike-based shiftrotationmethod. The algorithm error is lower than 0.4%, and the noise propagation ratio can be reduced by 70% using large shifts. Theabsolute testing of spherical optics is carried out to verify this method. One spherical surface was tested with the presented absolute testingmethod and the method of point diffraction interferometer (PDI). The difference of the measurement results based on the two methodsshowed that the testing uncertainty reached 0.19 nm RMS, which indicated that the presented method has potential sub-nanometer testinguncertainty.

Slip-free processing of (001) silicon wafers under 1064 nm laser ablation

ZhiChao Jia, zewen li, Xueming Lv, and Xiaowu Ni

Doc ID: 284009 Received 04 Jan 2017; Accepted 09 May 2017; Posted 09 May 2017  View: PDF

Abstract: Slip phenomenon on (001) silicon surface under 1064 nm laser ablation was studied by experiments and simulations. The surface morphologies of the silicon wafers after laser irradiation were observed using an optical microscope. The slip patterns showed that slip occurred before melting were responsible for low-quality ablation surface. The slip damage was predicted by a three-dimension finite element model based on heat transfer and thermoelasticity theory. The judging criterion of slip was explained in detail. The numerical results gave a better understanding of slip phenomenon in experiments. It is shown that low laser irradiances cause slip and high laser irradiances are helpful in preventing slip. The threshold irradiance is ~1 MW/cm2. Lasers with higher irradiance are essential to get a slip-free ablation on (001) silicon surface.

Diffuse back-illumination setup for high temporally resolved extinction imaging

Fredrik Westlye, Keith Penney, Anders Ivarsson, Lyle Pickett, Julien Manin, and Scott Skeen

Doc ID: 293025 Received 18 Apr 2017; Accepted 09 May 2017; Posted 15 May 2017  View: PDF

Abstract: This work presents the development of an optical setup for quantitative, high temporal resolution line of sight extinction imaging in harsh optical environments. The application specifically targets measurements of automotive fuel sprays at high ambient temperature and pressure conditions where time scales are short and perceived attenuation by refractive index gradients along the optical path (i.e., beam-steering) can be significant. The illumination and collection optics are optimized to abate beam-steering and the design criteria are supported by well-established theoretical relationships. The general effects of refractive steering are explained conceptually using simple raytracing. Three isolated scenarios are analyzed to establish the lighting characteristics required to render the observed radiant flux unaffected by the steering effect. These criteria are used to optimize light throughput in the optical system enabling minimal exposure times and high temporal resolution capabilities.. The setup uses a customized engineered diffuser to transmit a constant radiance within a limited angular range such that radiant intensity is maximized while fulfilling the lighting criteria for optimal beam-steering suppression. Methods for complete characterization of the optical system are detailed. Measurements of the liquid-vapor boundary and the soot volume fraction in an automotive spray are presented to demonstrate the resulting improved contrast and reduced uncertainty. The current optical setup reduces attenuation caused by refractive index gradients by an order of magnitude compared to previous high temporal resolution setups.

Towards industrial ultrafast laser microwelding:SiO2 and BK7 to aluminum alloy

Richard Carter, Michael Troughton, Jianyong Chen, Ian Elder, Robert Thomson, M J Daniel Esser, Robert Lamb, and Duncan Hand

Doc ID: 287698 Received 01 Mar 2017; Accepted 09 May 2017; Posted 09 May 2017  View: PDF

Abstract: We report systematic analysis and comparison of ps-laser microwelding of industry relevant Al6082 parts to SiO2and BK7. Parameter mapping of pulse energy and focal depth on the weld strength is presented. The weldingprocess was found to be strongly dependent on the focal plane but has a large tolerance to variation in pulseenergy. Accelerated lifetime tests by thermal cycling from -50 to +90 °C are presented. Welds in Al6082-BK7 partssurvive over the full temperature range where the ratio of thermal expansion coefficients is 3.4:1. Welds inAl6082-SiO2 parts (ratio 47.1:1) survive only a limited temperature range.

Flux Density Measurement of Radial Magnetic Bearing with A Rotating Rotor Based on Fiber Bragg Grating-Giant Magnetostrictive Material Sensors

Guoping Ding, SONGCHAO ZHANG, HAO CAO, BIN GAO, and BIYUN ZHANG

Doc ID: 294523 Received 24 Apr 2017; Accepted 08 May 2017; Posted 11 May 2017  View: PDF

Abstract: The rotational magnetic field of radial magnetic bearings characterizes remarkable time and spatial nonlinearity due to the eddy current and induced electromagnetic field. It is significant to experimentally obtain the features of the rotational magnetic field of the radial magnetic bearings to validate the theoretical analysis and reveal the discipline of rotational magnetic field. This paper developed thin-slice fiber Bragg grating-Giant Magnetostrictive Material (FBG-GMM) magnetic sensors to measure air-gap flux density of a radial magnetic bearing with a rotating rotor; a radial magnetic bearing test rig was constructed and the rotational magnetic field with different rotation speed was measured, moreover, finite element method was used to simulate the rotational magnetic field, the measurement results and FEM results were investigated and it was concluded that the FBG-GMM sensors were capable of measuring the radial magnetic bearing’s air gap flux density with a rotating rotor and the measurement results showed a certain degree of accuracy.

Aero-Optical Investigation of Shock-Related Effects on Hemisphere-On-Cylinder Turrets at Transonic Speeds

Jacob Morrida, Stanislav Gordeyev, Nicholas De Lucca, and Eric Jumper

Doc ID: 285093 Received 19 Jan 2017; Accepted 06 May 2017; Posted 08 May 2017  View: PDF

Abstract: Aero-optical environment around a hemisphere-on-cylinder turret with both flat- and conformal windows was studied experimentally in-flight using the Airborne Aero-Optical Laboratory (AAOL) for a range of subsonic and transonic Mach numbers between 0.5 and 0.8. Above M = 0.6, the local shock appeared near the top of the turret, causing additional aero-optical distortions at side-looking angles. Using time-resolved wavefronts, instantaneous shock locations were extracted and analyzed. The mean shock location was found to be near a viewing angle, α = 80 degrees for both window types at M = 0.7 and 0.8. For M = 0.8, the shock has a single frequency peak at StD = 0.15, the same as for the unsteady separation line, indicating a lock-in mechanism between the shock and the separated wake region. Analysis of aero-optical distortions in the wake indicated that the wake dynamics were beginning to be affected by the shock only at high transonic speed of M = 0.8 for the conformal-window turret.

A Novel Cassegrain Antenna with a Semi-transparent Secondary mirror

Wei Caiyang, Yang Huajun, Ping Jiang, Wensen He, Yu Tian, and Xue Chen

Doc ID: 286926 Received 22 Feb 2017; Accepted 05 May 2017; Posted 05 May 2017  View: PDF

Abstract: With the help of the vector theory of reflection and refraction, a novel emitting Cassegrain antenna with a semitransparentsecondary mirror has been proposed and analyzed for a distant point source. Based on the absorbtivity valued3.00% and the reflectivity valued 0.10% , this new emitting antenna can increase the transmission efficiency from 63.65%to93.85%. Besides, an off-axis parabolic receiving antenna corresponding to the emitting antenna is designed and the 3-D raytrace simulation result is given. According to the simulation result, this receiving antenna can nicely converge the rays from theemitting antenna.

Minimum length modulator design With Graphene-based plasmonic waveguide

MuhammadReza Ghahri and rahim faez

Doc ID: 287429 Received 23 Feb 2017; Accepted 03 May 2017; Posted 03 May 2017  View: PDF

Abstract: In this study, we simulated and analyzed a plasmonic waveguide modulator based on single layer Graphene. It Includes a Graphene sheet, which sandwiches between two layers of silicon dioxide. Then, some gates are arranged on either side of the waveguide on a periodic structure. When an electric field is applied perpendicular to the waveguide plate, the Fermi level of Graphene under the gates, changes. Detailed analysis is performed by the method of lines based on Maxwell equations along the propagation direction of the waveguide. Computation of the multi-gate device starts by examining the effect of Fermi level. Transmission coefficient of the magnetic-field norms of the modulator is calculated by varying the parameters such as Fermi level, length, gates number and distance between the gates to achieve optimized design of the modulator device with very small dimension. The results show that at higher Fermi levels, where the imaginary part of the effective index of the waveguide is close to zero, the reflection is dominant and absorption is low. Therefore, the modulator length becomes so long that is more than one hundred nanometers. At lower Fermi level, where the amount of imaginary part of the effective index is significant, the absorption is dominant. At this range, one-gate device is sufficient for modulation. Consequently, the designed minimum device length becomes equal to six nanometers for the ten-micron wavelength. Furthermore, the design is carried out in other wavelengths.

Structural evolution of axial intensity distribution during hot imageformation

Kewei You, li Zhang, Xuejie Zhang, Mingying Sun, and Jianqiang Zhu

Doc ID: 290325 Received 09 Mar 2017; Accepted 03 May 2017; Posted 08 May 2017  View: PDF

Abstract: The structural evolution of the axial intensity distribution during hot image formation perturbed bya small circular optical obscuration is investigated in detail under different conditions. An analyticexpression is derived for the axial intensity distribution around the conjugate plane by assumingthe thickness of the nonlinear medium to be infinitely small. In view of the analysis of the axialintensity oscillation, the expression can be extensively utilized to characterize the intensitymaxima for a nonlinear medium with a finite thickness. The nonlinear medium thickness andobscuration size both have great influences on the magnitudes and distributed features of theintensity maxima, which vary from initially multiple ones with comparable intensities toeventually only one obvious maximum remaining. The reason for this phenomenon is that thenonlinear medium acts like a low-pass filter to the scattering field and optical interference existsbetween the scattering and background field. Furthermore, a fixed expression of nonlinearmedium thickness and obscuration size is obtained to determine the dividing point of thealterations of the hot image intensity distribution.

Characterizing ice particles using two -dimensional reflections of a lidar beam

Marissa Goerke, Zbigniew Ulanowski, Georg Ritter, Evelyn Hesse, Ryan Neely, Laurence Taylor, Robert Stillwell, and Paul Kaye

Doc ID: 286882 Received 16 Feb 2017; Accepted 30 Apr 2017; Posted 01 May 2017  View: PDF

Abstract: We report a phenomenon manifesting itself as brief flashes of light on the snow surface near a lidar beam. The flashes are imaged and interpreted as specular reflection patterns from individual ice particles. Such patterns have two-dimensional structure, and are similar to those previously observed in forward scattering. Patterns are easiest to capture from particles with well-defined horizontal facets, such as near-horizontally aligned plates. The patterns and their position can be used to determine properties such as ice particle shape, size, roughness, alignment and altitude. Data obtained at Summit in Greenland shows the presence of regular hexagonal and scalene plates, columns and rounded plates of various sizes, among others.

Antitwilight I: Structure and Optics

David Lynch, David Dearborn, and Steven Richtsmeier

Doc ID: 285631 Received 16 Mar 2017; Accepted 28 Apr 2017; Posted 09 May 2017  View: PDF

Abstract: Time-lapse videos, still photos, visual observations and theoretical studies were used to investigate the antitwilight, i.e., twilight opposite the sun. Colors, brightnesses and twilight feature elevations as a function of solar elevation were measured. Four roughly horizontal bands are identified and explained physically in terms of atmospheric geometry, the observer’s line-of-sight (LOS), optical depth, refraction and multiple scattering. Particular emphasis is placed on (1) the origin of the dark segment, (2) the rapid rise of the Belt of Venus with solar altitude and (3) ray tracing the low atmosphere to understand refractive effects. New names are suggested for three of the four previously named bands and the terminology is reconciled with earlier papers.

Passively Q-switched Yb-doped All-fiber ring laser based on the SBS feedback

Zhongwei Xu, Luo Xing, Luyun Yang, Jinggang Peng, Haiqing Li, and Jinyan Li

Doc ID: 286640 Received 17 Feb 2017; Accepted 26 Apr 2017; Posted 26 Apr 2017  View: PDF

Abstract: We report on a passively Q-switched Yb-doped all-fiber ring laser based on the stimulated Brillouin scattering(SBS) feedback in a 20m single mode fiber (SMF). The Q-switched pulses is generated from the Stokes pulses of SBSand amplified in the YDF. The tens nanoseconds self-Q-switched pulses with ~1kW maximum peak power isobtained. The repetition frequency of pulses train is tuned from 4kHz to 12.6kHz by changing the pump power inexperiment. A bandpass filter inserted in the laser cavity was used to suppress time jitter of Q-switched pulses.

Detecting the topological charge of optical vortex beams using a sectorial screen

Chen Ruishan, z xq, Yong Zhou, Hai Ming, Anting Wang, and Qiwen Zhan

Doc ID: 286793 Received 17 Feb 2017; Accepted 24 Apr 2017; Posted 26 Apr 2017  View: PDF

Abstract: We demonstrate a new method to detect the vortex beams carrying orbital angular momentum (OAM) by a sectorial screen. When the sectorial screen is illuminated by optical vortex beams, the far-field diffraction pattern can be used to visually determine the modulus and sign of topological charges. We also prove that center alignment in not strictly required. The experimental results agree well with the simulated results.

Adaptive Reconstruction for Coded Aperture Temporal Compressive Imaging

Yueting Chen, Chaoying Tang, Zhihai Xu, Qi Li, Min Cen, and Huajun Feng

Doc ID: 286818 Received 15 Feb 2017; Accepted 13 Apr 2017; Posted 14 Apr 2017  View: PDF

Abstract: This paper presents an adaptive reconstruction method for coded aperture temporal compressive imaging. A pixel-wise equal-exposure coding strategy is firstly designed, which brings regional motion objects within the captured coded image a shot-noise-like speckle feature. By taking advantage of this phenomenon, a motion area detecting method is proposed. Then the adaptively segmented motion areas will be reconstructed to a series of video frames and filled back into the static clear background. Both simulation and real experiment results demonstrate that the proposed method significantly reduces the time consumption of video reconstruction and maintains high image quality.

Bow-shaped Caustics from Conical Prisms: a 13th Century Account of Rainbow Formation from Robert Grosseteste's De iride

Joshua Harvey, Hannah Smithson, Clive Siviour, Giles Gasper, Sigbjorn Sonnesyn, Brian Tanner, and Tom McLeish

Doc ID: 287109 Received 28 Feb 2017; Accepted 11 Apr 2017; Posted 20 Apr 2017  View: PDF

Abstract: The rainbow has been the subject of discussion across a variety of historical periods and cultures, and numerous optical explanations have been suggested. Here, we further explore the scientific treatise De iride [On the Rainbow] written by Robert Grosseteste in the thirteenth century. Attempting to account for the shape of the rainbow, Grosseteste bases his explanation on the optical properties of transparent cones, which he claims can give rise to arc-shaped projections through refraction, i.e. caustics. By stating that atmospheric phenomena are reducible to the geometric optics of a conical prism, the De iride lays out a coherent and testable hypothesis. Through both physical experiment and physics-based simulation we present a novel characterization of cone-light interactions, demonstrating that transparent cones do indeed give rise to bow-shaped caustics; a nonintuitive phenomenon that suggests Grosseteste's theory of the rainbow is likely to have been grounded in observation.

Antitwilight II: Monte Carlo Simulations

Steven Richtsmeier, David Lynch, and David Dearborn

Doc ID: 287554 Received 27 Feb 2017; Accepted 07 Apr 2017; Posted 10 Apr 2017  View: PDF

Abstract: For this paper, we employ the Monte Carlo Scene (MCScene) radiative transfer code to elucidate the underlying physics giving rise to the structure and colors of the antitwilight, i.e., twilight opposite the sun. MCScene calculations successfully reproduce colors and spatial features observed in videos and still photos of the antitwilight taken under clear, aerosol-free sky conditions. We examine the effects of solar elevation angle, Rayleigh scattering, molecular absorption, aerosol scattering, multiple scattering, and surface reflectance on the appearance of the antitwilight. We also compare MCScene calculations with predictions made by the MODTRAN radiative transfer code for a solar elevation angle of +1°.

Tropospheric haze and colors of the clear twilight sky

Raymond Lee and Duncan Mollner

Doc ID: 285879 Received 31 Jan 2017; Accepted 23 Mar 2017; Posted 24 Mar 2017  View: PDF

Abstract: At the earth’s surface, clear-sky colors during civil twilights depend on the combined spectral effects of molecular scattering, extinction by tropospheric aerosols, and absorption by ozone. Molecular scattering alone cannot produce the most vivid twilight colors near the solar horizon, for which aerosol scattering and absorption are also required. However, less well known are haze aerosols’ effects on twilight sky colors at larger scattering angles, including near the antisolar horizon. To analyze this range of colors, we compare 3D Monte Carlo simulations of skylight spectra with hyperspectral measurements of clear twilight skies over a wide range of aerosol optical depths. Our combined measurements and simulations indicate that: (a) the purest antisolar twilight colors would occur in a purely molecular, multiple-scattering atmosphere, whereas (b) the most vivid solar-sky colors require at least some turbidity. Taken together, these results suggest that multiple scattering plays an important role in determining the redness of the antitwilight arch.

Dependence of depth of focus on spherical aberration of optical systems

Antonin Miks and Jiri Novak

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

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

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