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Turning a conventional camera to a 3D camera with an add-on

Pauline Trouvé, Jacques Sabater, Anthelme Bernard-Brunel, Frederic Champagnat, Guy Le Besnerais, and Thierry Avignon

Doc ID: 309061 Received 09 Nov 2017; Accepted 23 Feb 2018; Posted 23 Feb 2018  View: PDF

Abstract: We propose to add an optical component in front of a conventional camera in order to improve depth estimation performance of Depth from Defocus (DFD), an approach based on the relation between defocus blur and depth. The add-on overcomes ambiguity and dead zone which are the fundamental limitations of DFD with a conventional camera. Indeed the optical component adds an optical aberration to the whole system which makes the blur unambiguous and measurable for each depth. We look into two optical components: the first one adds astigmatism and the other one chromatic aberration. In both cases we present the principle of the add-on and experimental validations on real prototypes.

Research on characteristics of symmetric optothermal microactuators

Yingda Wang, QingYang You, JiaJun Chen, and Zhang Haijun

Doc ID: 313572 Received 15 Nov 2017; Accepted 23 Feb 2018; Posted 23 Feb 2018  View: PDF

Abstract: This paper proposes and studies symmetric optothermal microactuators (OTMAs) directly controlled by laser beam. Based on the principle of thermal flux, a theoretical model is established describing the laser-induced temperature rises and optothermal expansions of the OTMAs' expansion arms. Temperature rise distributions of the arms with lengths of 590, 990 and 2260 μm are simulated, revealing that the local maximum temperature rises are less than 75.9°C under 2 mW laser irradiation. Simulations on optothermal expansions of the arms caused by laser irradiation are also made, showing that expansion increases considerably as the arm's length increases from 250~1000 μm, while insignificantly from 1250 to 2500 μm. Experiments have been further conducted on three microfabricated OTMAs under a laser beam of 2 mW power. It is shown that the OTMAs are capable of generating maximum deflections of 7.3, 11.3 and 13.6 μm, and that the growth of deflection is comparatively obvious when the total length changes from 750 to 1200 μm, while insignificant from 1200 to 80 μm. Both simulations and experiments prove that the OTMAs are capable of implementing direct laser-controlled microactuation in which only ~2 mW laser power is demanded. It is also proved that doubling of total length or arm length does not correspondingly result in the double increase of deflection or expansion. Therefore, total length/expansion arm’s length around or less than 1200/1000 μm will be more appropriate for obtaining satisfactory characteristics of OTMAs. The optothermal microactuators may be potentially applied in MEMS/MOEMS and micro/nano-technology.

Acquisition of full-resolution image and aliasingreduction for spatially-modulated imagingpolarimeter with two snapshots

Jing Zhang, CHANGAN yuan, Guohua Huang, YINJUN ZHAO, Wenyi Ren, qizhi cao, JIANYING LI, and Mingwu Jin

Doc ID: 314671 Received 18 Dec 2017; Accepted 22 Feb 2018; Posted 23 Feb 2018  View: PDF

Abstract: Snapshot imaging polarimeter using spatial modulation can encode four Stokes parameters allowinginstantaneous polarization measurement from a single interferogram. However, the reconstructed polarizationimages could suffer severe aliasing signal if the high-frequency component of the intensity image is prominent andoccurs in the polarization channels, and the reconstructed intensity image also suffers reduction of spatialresolution due to low-pass filtering. In this work, a method using two anti-phase snapshots is proposed to addressthe two problems simultaneously. The full-resolution target image and the pure interference fringes can beobtained from the sum and the difference of the two anti-phase interferograms, respectively. The polarizationinformation reconstructed from the pure interference fringes does not contain the aliasing signal from the highfrequencycomponent of the object intensity image. The principles of the method are derived and its feasibility istested by both computer simulation and a verification experiment. This work provides a novel method for spatiallymodulated imaging polarization technology with two snapshots to simultaneously reconstruct a full-resolutionobject intensity image and high-quality polarization components.

Extraction of interference phase in frequencyscanninginterferometry based on EMD and Hilberttransform

Wen Deng, Zhigang Liu, Zhongwen Deng, Xingyu Jia, and Zhiyong Wang

Doc ID: 315208 Received 07 Dec 2017; Accepted 22 Feb 2018; Posted 23 Feb 2018  View: PDF

Abstract: Nonlinear optical frequency scanning is inevitable in frequency scanning interferometry with tunable lasers andseriously reduces the accuracy of interference signal phase extraction. To address this, we propose a phaseextraction algorithm based on empirical mode decomposition and Hilbert transformation. The method caneffectively eliminate the influence of the optical frequency scanning nonlinearity. The validity and stability of themethod have been verified through simulations and experiments. Moreover, the single-cycle relative error of thephase between adjacent peaks and the standard deviation of the measurement system improved to 0.6% and 0.7μm, respectively, with a 5-MHz sampling rate.

Photonic Bandpass Filter Characteristics of Multimode SOI Waveguides Integrated with Submicron Gratings

Parimal Sah and Bijoy Krishna Das

Doc ID: 319579 Received 11 Jan 2018; Accepted 22 Feb 2018; Posted 23 Feb 2018  View: PDF

Abstract: It has been shown that adiabatically launched fundamental mode into a multimode SOI waveguide withsubmicron grating offers a well-defined flat-top bandpass filter characteristics in transmission. Transmittedspectral bandwidth is controlled by adjusting both waveguide and grating design parameters.The bandwidth is further narrowed down by cascading two gratings with detuned parameters. A semianalyticalmodel is used to analyze the filter characteristics (1500 nm l 1650 nm) of the deviceoperating in TE-polarization. The proposed devices were fabricated with an optimized set of design parametersin SOI substrate with a device layer thickness of 250 nm. The pass bandwidth of waveguidedevices integrated with a single-stage gratings are measured to be 24 nm, whereas for the device withtwo cascaded gratings with slightly detuned periods (DL = 2 nm) exhibit pass bandwidth down to 10nm.

Airlight-imposed errors for space-object polarimetricobservations from the ground

David Tyler and Casey Demars

Doc ID: 312719 Received 03 Nov 2017; Accepted 22 Feb 2018; Posted 22 Feb 2018  View: PDF

Abstract: We discuss and characterize how polarimetric sensing is contaminated by various "airlight" phenomena,as well as unpolarized light from the target, when space objects are observed with a ground-based telescope.Estimates of the polarization state are limited by unpolarized target light regardless of sensortechnology or estimator algorithm, and increased target brightness actually degrades estimation of the S1,S2, and S3 Stokes parameters if the added light is unpolarized. Unpolarized airlight in the field of viewhas an identical degrading effect. Atmospheric scattering can significantly polarize airlight, so airlightpolarization must be calibrated and subtracted from the estimated target polarization. We derive an expressionfor the mean-square Stokes estimation error when noisy, biased estimates for the airlight polarizationstate are subtracted from noisy, biased estimates of the target polarization state; this expressionshows that target and airlight Stokes estimation noise and bias generally sum in the ms estimation errorfor airlight-calibrated target Stokes. While SNR for the estimate of a given Stokes parameter increaseswith the magnitude of that parameter, estimation bias also appears to be correlated with magnitude. Wenote that when the linear Stokes reference is not arbitrary, requiring a rotational transformation of theestimated Stokes vector, the SNRs of the S1 and S2 estimates vary with the rotation angle. Finally, weshow that measured data can be used in numerical calculations described here to approximate the errorsassociated with Stokes estimation, with or without airlight calibration.

12W CW green output from a 200µm fiber coupled diode laser based on TO-Can packaged emitters

Pengfei Zhao, Wang Zhining, Haijuan Yu, and Xuechun Lin

Doc ID: 314397 Received 03 Jan 2018; Accepted 22 Feb 2018; Posted 22 Feb 2018  View: PDF

Abstract: A 12-W green laser diode module with fiber coupled output is developed. The high power fiber coupled output of green diode laser is realized by using technologies of beam collimation, spatial beam combining, beam shaping and fiber coupling based on TO-Can packaged emitters. According to the optical fiber parameter, the detailed beam combination method is described and the maximum quantity of single emitter in beam combination is calculated theoretically. In the experiment, as many as 16 green laser diode emitters with output power of 1W each were combined and coupled into a fiber with core diameter of 200µm and a numerical aperture of 0.22. A total of 12.2W continuous-wave output at wavelength of 520nm was achieved with a coupling efficiency of 86.5% and an electro-optical efficiency of 10.6%.

Spectral-differential-based unmixing for multispectral photoacoustic imaging

Takeshi Hirasawa, Ryu Iwatate, Mako Kamiya, Shinpei Okawa, Masanori Fujita, Yasuteru Urano, and Miya Ishihara

Doc ID: 314586 Received 29 Nov 2017; Accepted 21 Feb 2018; Posted 22 Feb 2018  View: PDF

Abstract: We propose the use of a spectral differential method (SDM) to emphasize the spectral peaks of multispectral photoacoustic (MS-PA) images. Because contrast agent signals have spectral peaks at the contrast agent absorption peak, SDM can selectively emphasize contrast agent signals. Unlike the conventional spectral fitting method (SFM), SDM does not require reference background spectra and, consequently, does not suffer from separation error caused by reference spectra deviation from the measured spectra. We performed MS-PA imaging of subcutaneous tumors of mice injected by small organic molecule based contrast agents. Contrast agent images obtained by SDM were clearer than those obtained by SFM.

Three-dimensional Facial Digitization Using Advanced Digital Image Correlation

Hieu Nguyen, Hien Kieu, Zhaoyang Wang, and Hanh Le

Doc ID: 312944 Received 08 Nov 2017; Accepted 21 Feb 2018; Posted 22 Feb 2018  View: PDF

Abstract: Presented in this paper is an effective technique to acquire the three-dimensional (3D) digital images of human face without the use of active lighting and artificial patterns. The technique is based on binocular stereo imaging and digital image correlation, and it includes two key steps: camera calibration and image matching. The camera calibration involves a pinhole model and a bundle-adjustment approach, and the governing equations of the 3D digitization process are described. For reliable pixel-to-pixel image matching, the skin pores and freckles or lentigines on the human face serve as the required pattern features to facilitate the process. It employs feature-matching-based initial guess, multiple subsets, iterative optimization algorithm, and reliability-guided computation path to achieve fast and accurate image matching. Experiments have been conducted to demonstrate the validity of the proposed technique. The simplicity of the approach together with the affordable cost of the implementation show its practicability in scientific and engineering applications.

Transparent surface orientation from polarizationimaging using vector operation

Jing Liu, xiaotian lu, Weiqi Jin, Xia Wang, Su Qiu, and renjie wen

Doc ID: 313271 Received 13 Nov 2017; Accepted 21 Feb 2018; Posted 22 Feb 2018  View: PDF

Abstract: The existing methods for shape from polarization of transparent objects are based on two assumptions: (1) theparaxial assumption, assuming that the reflected ray is parallel to the optical axis of the imaging system; (2) the scomponentapproximation assumption, which assumes that the s-component of the reflected light is predominantand the p-component is neglected. To overcome limitations posed by these two assumptions, this paper proposes amethod based on the polarization characteristics of reflection from transparent surface and vector operation. Toovercome the paraxial assumption, the normal vector of the transparent surface is deduced by vector operation,analyzing the relationships between the direction vector of reflection, normal vector of the reflection plane,intersection line of the reflection plane and imaging plane, and normal vector of the transparent surface. Toovercome limitations of the s-component approximation assumption, analyzed is the angle between the scomponentand the polarization direction of the reflected light, which yields improved measurement precision.Experiment is performed with transparent targets (flat glass positioned at different angles), the results of whichshow that the measurement error with this method is significantly less than those of existing methods. Thus, ourmethod overcomes the abovementioned limitations while affording improved measurement precision.

Phaseless computational ghost imaging at microwavefrequencies using a dynamic metasurface aperture

Aaron Diebold, Mohammadreza F. Imani, Timothy Sleasman, and David Smith

Doc ID: 309325 Received 17 Oct 2017; Accepted 21 Feb 2018; Posted 22 Feb 2018  View: PDF

Abstract: We demonstrate a dynamic metasurface aperture as aunique tool for computational ghost imaging at microwavefrequencies. The aperture consists of a microstripwaveguide loaded with an array of metamaterialelements, each of which couples energy from thewaveguide mode to the radiation field. With a tuningmechanism introduced into each independentlyaddressablemetamaterial element, the aperture canproduce diverse radiation patterns that vary as a functionof tuning state. Here, we show that the fields fromsuch an aperture approximately obey speckle statisticsin the radiative near field. Inspired by the analogywith optical correlation imaging, we use the dynamicaperture as a means of illuminating a scene with structuredmicrowave radiation, receiving the backscatteredintensity with a simple waveguide probe. By correlatingthe magnitude of the received signal with the structuredintensity patterns, we demonstrate high-fidelity,phaseless imaging of sparse targets. The dynamic metasurfaceaperture as a novel ghost imaging structurecan find application in security screening, through-wallimaging, as well as biomedical diagnostics.

Quantitative discrimination of pearls usingpolarization sensitive optical coherence tomography

Jae Hwi Lee, Jun Geun Shin, Hae Yeon Kim, and Byeong Ha Lee

Doc ID: 309479 Received 18 Oct 2017; Accepted 21 Feb 2018; Posted 22 Feb 2018  View: PDF

Abstract: We propose a robust method that can quantitatively discriminate genuine pearls from imitation ones by introducing theconcept of entropy in the polarization sensitive optical coherence tomography (PS-OCT). Qualitatively, by examining thebirefringence properties of the nacre region of pearls with PS-OCT, the genuine pearls can be easily discriminated. Toquantify the amount of birefringence formation, however, the concept of phase retardation entropy is introduced, which isexpected to have a higher value when a PS-OCT tomogram has more diverse phase retardation values in its histogram.Experimental confirmation demonstrated that the phase retardation entropy of a genuine pearl was always higher than animitated pearl. By experimenting with various genuine and imitation pearls, we can say that the phase retardation entropyis effective as a quantitative criterion for discriminating and evaluating pearls.

Optical configuration with fixed transversemagnification for self-interference incoherent digitalholography

Masatoshi Imbe

Doc ID: 319597 Received 11 Jan 2018; Accepted 21 Feb 2018; Posted 22 Feb 2018  View: PDF

Abstract: The optical configuration proposed in this paper consists of a 4-f optical setup with the wavefront modulationdevice on the Fourier plane such as a concave mirror and a Spatial light modulator. The transversemagnification of reconstructed images with the proposed configuration is independent of locations ofan object and an image sensor; therefore, reconstructed images of object(s) at different distances can bescaled with a fixed transverse magnification. It is yielded based on Fourier optics and mathematicallyverified with the optical matrix method. Numerical simulation results and experimental results are alsogiven to confirm the fixity of the reconstructed images.

An ultra-fast all optical decoder based on nonlinear photonic crystal ring resonators

Tina Daghooghi, Mohammad Soroosh, and Karim Ansari-Asl

Doc ID: 313732 Received 17 Nov 2017; Accepted 21 Feb 2018; Posted 21 Feb 2018  View: PDF

Abstract: In this paper, a 2-to-4 all optical decoder based on photonic crystal ring resonators is introduced. The photonic crystal structure has a 2D square chalcogenide rod lattice whose maximum response time is 2 ps. Three ring resonators including nonlinear rods with 9×10-17 W/μm2 for Kerr coefficient carry out switching operation at 1550nm wavelength. Switching speed of the device is 500 GHz that is more than previously presented works. Also, small size of the structure is sufficient for optical integrated circuits.

Monte Carlo Ray-Trace Diffraction Based On the Huygens-Fresnel Principle

James Mahan, Nguyen Vinh, Vinh Ho, and Nazia Munir

Doc ID: 314895 Received 08 Dec 2017; Accepted 20 Feb 2018; Posted 21 Feb 2018  View: PDF

Abstract: The goal of this effort is to establish the conditions and limits under which the Huygens-Fresnel principle accurately describes diffraction in the Monte Carlo ray-trace environment. This goal is achieved by systematic intercomparison of dedicated experimental, theoretical, and numerical results. We evaluate the success of the Huygens-Fresnel principle by predicting and carefully measuring the diffraction fringes produced by both slit and circular apertures. We then compare the results from the analytical and numerical approaches with each other and with dedicated experimental results. We conclude that use of the MCRT method to accurately describe diffraction requires that careful attention be paid to the interplay among the number of aperture points, the number of rays traced per aperture point, and the number of bins on the screen. This conclusion is supported by standard statistical analysis, including the adjusted coefficient of determination, R_"adj" ^2, the root-mean-square deviation, RMSD, and the reduced chi-square statistics, χ_v^2.

Active Underwater Detection with an Array of Atomic Magnetometers

Cameron Deans, Luca Marmugi, and Ferruccio Renzoni

Doc ID: 315173 Received 07 Dec 2017; Accepted 20 Feb 2018; Posted 21 Feb 2018  View: PDF

Abstract: We report on a 2×2 array of radio-frequency atomic magnetometers in magnetic induction tomography configuration. Active detection, localization, and real-time tracking of conductive, non-magnetic targets are demonstrated in air and saline water. Penetration in different media and detection are achieved thanks to the sensitivity and tunability of the sensors, and to the active nature of magnetic induction probing. We obtained a 100% success rate for automatic detection and 93% success rate for automatic localization in air and water, up to 190 mm away from the sensors’ plane (100 mm underwater). We anticipate magnetic induction tomography with arrays of atomic magnetometers finding applications in civil engineering and maintenance, oil&gas industry, geological surveys, marine science, archeology, search and rescue, and security and surveillance.

Effect of anisotropy on bit-error-rate for asymmetricalGaussian beam in turbulent ocean

Yalçın Ata and Yahya Baykal

Doc ID: 317926 Received 18 Dec 2017; Accepted 20 Feb 2018; Posted 21 Feb 2018  View: PDF

Abstract: Effect of anisotropy on the average bit-error-rate (BER) is investigated when asymmetrical Gaussian beam ispropagated in anisotropic turbulent ocean. BER is found to decrease in response to an increase in the anisotropylevel in both x and y-directions. Higher average signal-to-noise ratio (SNR), wavelength and microscale length yieldsmaller BER values. BER starts to raise with an increase in the asymmetrical beam source size in both x and ydirections,source size ratio in x and y directions, salinity and temperature contribution factor, the dissipation ofthe mean squared temperature and the propagation distance. At the fixed source size ratio in x and y directions ofthe asymmetrical beam source size, larger source sizes increase BER. Anisotropic turbulent ocean seems to exhibitbetter BER values as compared to isotropic turbulent ocean.

14 GHz broadband and continuously frequency-tuned Nd:YVO4 laser with an RTP etalon

Xinrui Xu, Rongwei Fan, XuDong Li, Yufei Ma, Renpeng Yan, xing wang, Zhaodong Chen, Zhigang Zhou, and deying chen

Doc ID: 318923 Received 04 Jan 2018; Accepted 20 Feb 2018; Posted 21 Feb 2018  View: PDF

Abstract: An LD-pumped broadband and continuously frequency-tuned all-solid-state Nd:YVO4 laser at 1064 nm with an output power of 200 mW is demonstrated. A RbTiOPO4 (RTP) etalon and a piezoelectric-transducer (PZT) are utilized for coarse and fine frequency tuning, respectively. Dependence of the frequency excursion on the applied voltage to the RTP etalon and the displacement of the PZT is theoretically and experimentally investigated. A continuous frequency tuning of 14 GHz is conducted by synchronous adjustment of the RTP etalon and the PZT. The tuning covers more than 6 times longitudinal mode spacing of the laser resonator without any mode hops.

Beam quality improvement by controlling thermallens spherical aberration in an end-pumpedNd:YVO4 laser

Qiangqiang Yao, Yuan Dong, qihan wang, and guang yong jin

Doc ID: 319074 Received 08 Jan 2018; Accepted 20 Feb 2018; Posted 22 Feb 2018  View: PDF

Abstract: We present for the first time the influence of spherical aberration on the beam quality of a single-stage laseramplifier. We set up an amplifier with a special structure to measure the spherical aberration distribution inthe cavity. The output power of the oscillator was controlled and the pump power of the amplifier wasadjusted to improve the beam quality. The results show that there is an optimal amplifier pump power, whichmaximizes the output laser beam quality. In the presented experiment, an optimal laser beam was achievedwith an output power of 10.54W and beam quality of M2x=1.54, M2y=1.39 for a pump power of 9.33W, oscillatoroutput power of 9.2W, and a beam quality of M2x=2.10, M2y=2.03.

Three-mirror anastigmat for cosmic microwave background observations

Stephen Padin

Doc ID: 320108 Received 18 Jan 2018; Accepted 19 Feb 2018; Posted 22 Feb 2018  View: PDF

Abstract: An off-axis three-mirror anastigmat is proposed for future cosmic microwave background observations. The telescope has a 5 m diameter primary, giving 1.5' angular resolution at λ=2 mm, which is adequate for measurements of gravitational lensing and for galaxy cluster surveys. The design includes several key features, not previously combined in a large telescope, that are important for sensitive measurements, especially on large angular scales: (1) high throughput (8° diameter diffraction-limited field of view at λ=1 mm, and 12×8° at λ=3 mm, so a single telescope could support all the detectors for an optimistic, future experiment); (2) low scattering (all the mirrors are small enough to be monolithic, so there are no segment gaps); (3) full boresight rotation, over the full elevation range, for measuring polarization errors; and (4) a comoving shield or baffle around the entire telescope to control pickup.

Ultra-long magnetization needle induced by focusing azimuthally polarized beams with spherical mirrors

Li Hang, Kai Luo, Jian Fu, Yizhe Chang, Ying Wang, and Peifeng Chen

Doc ID: 311242 Received 20 Dec 2017; Accepted 19 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: Based on extended Richards-Wolf theory for axisymmetric surfaces and the inverse Faraday effect, we propose the generation of a purely longitudinal magnetization needle by focusing Gaussian annular azimuthally polarized beams with a spherical mirror. The needle obtained has a longitudinal length varying hundreds to thousands of wavelengths and the corresponding aspect ratio can easily more than 2000. It may be the first time that a magnetization needle of which the aspect ratio is over 500 is achieved. The analytical expression is given and the longitudinal length is tunable by changing the value of the angular thickness and position of the annular beams.

Quantitative evaluation of active thermography usingcontrast to noise ratio

Michal Svantner, Lukáš Muzika, Tomáš Chmelík, and Jiri Skala

Doc ID: 318796 Received 03 Jan 2018; Accepted 19 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: Active thermography is an infrared based technique for material non-destructive testing. It often uses advancedevaluation techniques based on temperature spatial and temporal changes. Results of the active thermography are contrastdifferences, which indicate possible defects in an inspected material. These differences cannot be quantified by temperature. Thiscontribution is focused on active thermography results evaluation parameters and contrast to noise ratio (CNR) method, which canbe used for quantitative evaluation of the results. Different results interpretation procedures are introduced. An influence ofselection method for indication and reference regions and an effect of image scaling on inspection results are discussed.

Novel Methods Based on 1D Homography for Camera Calibration with 1D Objects

yaowen lv, liu wei, and Xiping Xu

Doc ID: 319608 Received 11 Jan 2018; Accepted 19 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: This paper focuses on camera calibration with 1D objects and novel methods are proposed in this paper. Differentfrom the known 1D object-based camera calibration algorithms which define the camera coordinate system as theworld coordinate system, we assume that the 1D calibration object is located along the X-axis of the worldcoordinate system. And based on this new model, a 3×2 1D homography is defined to relate the points in the 1Dobjects to the perspective image points thereof. Then the basic constraint for camera calibration using 1D objectsfrom a single image is derived. Subsequently, two existing motions, namely rotating around a fixed point andmoving on a plane, are discussed and new algorithms are proposed. In our methods, if the number of points in the1D objects is more than 3, more compact constraints can be obtained when the 1D objects rotating around a fixedpoint. In the case of planar motion, the estimation of vanishing points is not needed and the calibration accuracy issignificantly improved. Finally, both computer simulations and experiments are performed to validate theeffectiveness and robustness of our algorithms.

The influence investigation on ranging performance for range-gated Gm-APD ladar

Xin ZHOU, Jian-Feng Sun, Peng JIANG, Di Liu, and Qi Wang

Doc ID: 315384 Received 11 Dec 2017; Accepted 19 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: The ranging performance for Gm-APD Ladar is mainly evaluated by range accuracy and precision, although, they can evaluate the ranging performance of the exact position, it’s helpless to comprehensively evaluate the influence on the ranging of each parameter in the whole gate. In the actual detection, due to target echo’s triggering stochastically, which makes the delay adjustment inaccurate, the position of the echo in the gate is stochastic, so the theoretical calculation may not be able to make ladar ranging performance clear. As to this question, in this paper, based on central limit theorem, assuming that the position of the target in the gate obeys Gaussian distribution, and combining Gm-APD triggering probability model, we propose the mean ranging accuracy and precision theory, which can objectively evaluate the ranging performance, at the same time, we combine the theory with ladar ranging equation to investigate the effect of the parameter such as laser transmitting energy, pulse width, gate width, target range and noise intensity, on the ranging performance. The result shows, high transmitting energy, narrow gate width, short target range and low noise intensity makes mean ranging accuracy and precision low, and narrow pulse width will result in lower mean ranging accuracy and high mean ranging precision, wide pulse width has the opposite result, through comprehensive comparison, 10~ 30ns pulse width is more reasonable. According to the theoretical analysis results, to achieve ladar’s high ranging performance, we put forward concrete improvement measures, reducing the gate width, enhancing laser energy, using narrowband filter to reduce false alarm of noise, etc. The research content in this paper has reference significance for the Gm-APD ladar experimental parameter selection.

Analysis of composite/difference field scatteringproperties between a slightly rough optical surfaceand multi-body defects

Lei Gong, Zhen-Sen Wu, Ming Gao, and Tan Qu

Doc ID: 315437 Received 11 Dec 2017; Accepted 19 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: The effective extraction of optical surface roughness and defect characteristic provide important realistic values toimprove optical system efficiency. Based on finite difference time domain/multi-resolution time domain(FDTD/MRTD) mixed approach, composite scattering between a slightly rough optical surface and multi-bodydefect particles with different positions is investigated. The scattering contribution of defect particles or theslightly rough optical surface is presented. Our study provides a theoretical and technological basis for thenondestructive examination and optical performance design of nanometer structures.

Anti-Reflective Coating with Conductive Indium TinOxide Layer on Flexible Glass Substrates

Paul Sung, Robert Malay, Xin Wen, Christian Bezama, Varun Soman, Ming-Huang Huang, Sean Garner, Mark Poliks, and David Klotzkin

Doc ID: 317907 Received 11 Jan 2018; Accepted 19 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: Flexible glass has many applications including photovoltaics, OLED lightning, and displays. Its ability to beprocessed in a roll-to-roll facility enables high-throughput continuous manufacturing compared to conventionalglass processing. For photovoltaic, OLED lighting, and display applications, transparent conductors are required,with minimal optical reflection losses. Here, we demonstrate an anti-reflective coating (ARC) which incorporates auseful transparent conductor that is realizable on flexible substrates. This reduces the average reflectivity to lessthan 6% over the visible band from normal incidence to incident angles up to 60◦. This ARC is designed by theAverage Uniform Algorithm method. The coating materials consist of a multilayer stack of an electrically functionalconductive indium tin oxide (ITO) with conductivity 2.95 × 105 Siemens/m (31 Ω/), and AlSiO2. The coatingsshowed modest changes in reflectivity and no delamination after 10,000 bending cycles. This demonstrates thateffective conductive layers can be integrated into ARCs and can be realized on flexible glass substrates with properdesign and process control.

GaN microring waveguide resonators bonded tosilicon substrate by two-step polymer process

Ryohei Hashida, Takashi Sasaki, and Kazuhiro Hane

Doc ID: 318146 Received 20 Dec 2017; Accepted 18 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: Using a polymer bonding technique, GaN microring waveguide resonators were fabricated on Si substrate forfuture hybrid integration of GaN and Si photonic devices. The designed GaN microring consisted of a rib waveguidehaving a core of 510 nm in thickness and 1000 nm in width and a clad of 240 nm in thickness. A GaN crystallinelayer of 1000 nm in thickness was grown on a Si(111) substrate by metal organic chemical vapor deposition using abuffer layer of 300 nm in thickness for the compensation of lattice constant mismatch between GaN and Si crystals.The GaN/Si wafer was bonded to a Si(100) wafer by a two-step polymer process to prevent from trapping airbubbles. The bonded GaN layer was thinned from the backside by a fast atom beam etching to remove the bufferlayer and to generate the rib waveguides. The transmission characteristics of the GaN microring waveguideresonators were measured. The losses of the straight waveguides were measured to be 4.0±1.7dB/mm around awavelength of 1.55 μm. The microring radii were ranged from 30 μm to 60 μm, where the measured free-spectralranges varied from 2.58 nm to 5.30 nm. The quality factors of the microring waveguide resonators were from 1710to 2820.

Induction thermography of steel coupons with crack

Marc Genest and Gang Li

Doc ID: 318304 Received 22 Dec 2017; Accepted 18 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: Induction thermography technique was assessed experimentally and numerically on notched steel coupons usingtwo coil configurations: straight line and loop conditions. The coupons had different lengths of fatigue crackvarying from zero to 3 mm. The numerical predictions showed that the peak temperature was always located atthe crack tip or the notch tip position. The loop coil resulted in higher temperatures than those of the straight linecoil. Results showed that the numerical methods effectively supported the application assessment of this nondestructiveevaluation (NDE) technique for the steel material, but crack geometry remains a challenge as the exactshape of a natural crack is typically unknown. It is shown that induction thermography can detect crack as small as1 mm in the notched steel coupons. Commentary on the application of the NDE technique with the numericalmodelling support was provided.

Optimizing Laser Crater Enhanced Raman Spectroscopy

Vasily Lednev, Pavel Sdvizhenskii, Mikhail Grishin, Vera Filichkina, Alexander Shchegolikhin, and Sergey Pershin

Doc ID: 313900 Received 20 Nov 2017; Accepted 18 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: Raman signal enhancement by laser crater production was systematically studied for 785 nm continuous wavelaser pumping. Laser craters were produced in L-aspartic acid powder by nanosecond pulsed solid state Nd:YAGlaser (532 nm, 8 ns, 1 mJ/pulse), while Raman spectra were acquired then by using a commercial spectrometerwith 785 nm laser beam pumping. Raman signal enhancement effect was studied in terms of the number ofablating pulses used, the lens-to-sample distance and the crater-center-laser-spot offset. Influence of theexperiment parameters on Raman signal enhancement was studied for different powder materials . MaximumRaman signal enhancement reached 11-fold for loose powders but decreased twice for pressed tablets. Ramansignal enhancement was demonstrated for several diverse powder materials like gypsum or ammonium nitratewith better results achieved for the samples tending to give narrow and deep craters upon laser ablation stage.Alternative ways of cavity production (steel needle tapping and hole drilling) were compared with laser crateringtechnique in terms of Raman signal enhancement. Drilling was found to give the poorest enhancement of theRaman signal while both laser ablation and steel needle tapping provided comparable results. Here, we havedemonstrated for the first time that Raman signal can be enhanced 10-fold with the aid of simple cavity productionby steel needle tapping in rough highly reflective materials. Though LCERS requires additional pulsed laser, thistechnique is more appropriate for automatization compared to “needle tapping” approach.

Highly directive switchable nanoantenna array based on dielectric omega particles at terahertz frequencies

raana sabri, Ali Pourziad, and Saeid Nikmehr

Doc ID: 309681 Received 02 Nov 2017; Accepted 17 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: High refractive index dielectric nanoparticle with the ability of supporting both electric and magnetic resonances, operating at 1-2 terahertz (THz) is proposed. The suggested omega-shaped nanoparticle is able to control its resonance frequencies independently by adjusting its dimension. Moreover, if the length of cubical arms is adjusted asymmetrically, the omega particle exhibits switchable radiation beam in range of depending on the incident frequency. Here, the usage of the designed nanoparticle in directivity enhancement is considered, so nanoparticles are arranged in an array. Their employment for directivity enhancement has led to the maximum directivity of 11.1dB. Side lobe level has the minimum amount of -15.3dB. Total size of the structure is 400μm×400μm≅2.6λ×2.6λ in the x-y plane and it does not exceed from a quarter of wavelength in height.

Green’s Function for a Sharpened and Metal-Coated Dielectric Probe

Vineet Khullar, Gong Gu, Ali Passian, and Thomas Ferrell

Doc ID: 313051 Received 20 Nov 2017; Accepted 17 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: In apertureless scanning-probe optical microscopy and in the case of more traditional scanned optical probes coated with a metal that is thin near the probe tip (in lieu of an aperture) samples are probed via interaction between the probe and surface. In the nanometer-scale region between the tip and the sample the field can be approximated by quasi-electrostatic analytics. Hence, the coated probe can be modeled as in the present case as a hyperboloid of revolution without the need for hyperboloidal wave functions in the near zone. The solutions to Laplace’s equation and in general Green’s function with the application of the boundary conditions therefore yield an appropriate approximation and allow a completely analytical solution for the resonance effects upon the probe tip to be obtained. The large field enhancements due to the sharpness of the tip and to surface plasmon fields are thus analytically examined.

Laser investigation of Yb:YLF crystals fabricated with micro-pulling-down technique

Francesca Lelii, Shu Jun, Federico Pirzio, Giuliano Piccinno, Mauro Tonelli, and Antonio Agnesi

Doc ID: 313176 Received 10 Nov 2017; Accepted 16 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: Fiber rods of 10%-doped Yb:YLF were fabricated with the micro-pulling-down technique and characterized. The crystal a-axis was oriented along the rod length, allowing polarized emission with the largest cross section available in c direction. Laser experiments showed that these fiber samples perform very similarly to crystals grown by the standard Czochralski method. Intrinsic slope efficiency of about 50% was measured in both cases, with small comparable intracavity losses proving the good quality of the fiber material.

The optimal wavelength selection strategy in temporal phase unwrapping with projection distance minimization

Hui Li, Yan Hu, Tianyang Tao, Shijie Feng, Minliang Zhang, Yuzheng Zhang, and Chao Zuo

Doc ID: 297746 Received 07 Nov 2017; Accepted 16 Feb 2018; Posted 22 Feb 2018  View: PDF

Abstract: Micro Fourier Transform Profilometry(μFTP) is a recently developed computational framework for highspeed dynamic 3D shape measurement of transient scenes based on fringe projection. It has been demonstrated that by using high-frame-rate fringe projection hardware, μFTP can achieve accurate, denser, unambiguous, and motion-artifact-free 3D reconstruction at a speed up to 10,000Hz. μFTP utilizes a temporal phase unwrapping algorithm so-called projection distance minimization (PDM), in which multiple wavelengths are used to solve the phase ambiguity optimally in the maximum-likelihood sense. However, it has been found that the choice of the wavelengths is essential to the unambiguous measurement rangeas well as the unwrapping reliability in the presence of noise. In this work, the relations between the wavelength combination and the noise resistance ability of PDM are analyzed and investigated in detail by analytical, emulational, and experimental means. This leads to a qualitative conclusion that the noise resistance ability of PDM is fundamentally determined by the value of each item in wavelength ratio: smaller value of each item in wavelength ratio means better noise resistance ability in phase unwrapping. Our result provides a guideline for optimal wavelengths selection in order to improve the noise resistance ability of a practical fringe projection system. Simulations and experiments based on a microscopic fringe projection system are demonstrated to validate the correctness of our conclusion.

Manipulation of group-velocity-locked-vectordissipative-solitons and properties of the generatedhigh-order vector soliton structure

Shengnan Zhu, Wu Zhichao, Songnian Fu, and Luming Zhao

Doc ID: 321084 Received 30 Jan 2018; Accepted 16 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: Details of various composites of the projections originated from a fundamental group-velocity-locked-vectordissipative-soliton (GVLVDS) are both experimentally and numerically explored. By combining the projectionsfrom the orthogonal polarization components of the GVLVDS, a high-order vector soliton structure with a doublehumpedpulse profile along one polarization while a single-humped pulse profile along the orthogonal polarizationcan be observed. Moreover, by de-chirping the composite double-humped pulse, the time separation between thetwo humps is reduced from 15.36 ps to 1.28 ps, indicating that the frequency chirp of the GVLVDS contributessignificantly to the shaping of double-humped pulse profile.

Design of discrete and continuous super-resolving Toraldo pupils in the microwave range

Luca Olmi, Pietro Bolli, and Daniela Mugnai

Doc ID: 307768 Received 22 Sep 2017; Accepted 15 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: The concept of super-resolution refers to various methods for improving the angular resolution of an optical imaging system beyond the classical diffraction limit. In optical microscopy several techniques have been successfully developed with the aim of narrowing the central lobe of the illumination Point Spread Function. In Astronomy, however, no similar techniques can be used. A feasible method to design antennas and telescopes with angular resolution better than the diffraction limit consists of using variable transmittance pupils. In particular, discrete binary phase masks (0 or 180deg) with finite phase-jump positions, known as Toraldo Pupils, have the advantage of being easy to fabricate but offer relatively little flexibility in terms of achieving specific trade-offs betweendesign parameters, such as the angular width of the main lobe and the intensity of sidelobes. In this paper we show that a complex transmittance filter (equivalent to a continuous Toraldo pupil, i.e., consisting of infinitely narrow concentric rings) can achieve more easily the desired trade-off between design parameters. We also show how the super-resolution effect can be generated with both amplitude- and phase-only masksand confirm the expected performance with electromagnetic numerical simulations in the microwave range.

Robust digital holography design for flexible recording and precise reconstruction

Xianfeng Xu, Zhiwei Zhang, Zecheng Wang, Jing Wang, Kaiyun Zhan, Yulei Jia, and Zhiyong Jiao

Doc ID: 308406 Received 03 Oct 2017; Accepted 15 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: A robust digital holography recording design is presented to complete the work of switching between in-line and off-axis recording methods, precisely supervising the off-axis angle in off-axis holography so that the original image can be separated by minimum off-axis angle, and monitoring and removing the negative effects of the reference tilt error in phase-shifting digital holography. Comparing to the conventional digital holographic recording configuration, a supervising unit is introduced to control and to monitor the angle between reference beam and object beam. By the Fourier analysis on the interferograms recorded by the supervising unit and using the corresponding equations, the off-axis angle, which is crucial to reset the object image in holographic reconstruction can be calculated accurately and then chosen to the best recording angle. For in-line holography, the error effects from the slight tilt of the reference beam on the retrieved object wave-front can be eliminated more completely because the tilt angle is detected by another independent device. Furthermore, by using this advanced design, the experiment arrangement can be transformed from the in-line recording state to the off-axis state or from the latter one to the former one on line flexibly without rebuilding the experiment setup. The availability and effectiveness of this design is verified by our series of experiments.

Absolute frequency measurement of the molecular iodine hyperfine transitions at 647 nm

YAO-CHIN HUANG, YU-CHAN GUAN, TE-HWEI SUEN, Jow-Tsong Shy, and Li-Bang Wang

Doc ID: 314254 Received 24 Nov 2017; Accepted 15 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: We report absolute frequency measurements of the molecular iodine P(46) 5-4 a₁, a₁₀, and a₁₅ hyperfine transitions at 647 nm with a fiber-based frequency comb. The light source is based on a Littrow-type external-cavity diode laser. A frequency stability of 5×10¯¹² at a 200 s integration time when the light source is stabilized to the P(46) 5-4 a₁₅ line. The effect of pressure shift with -8.3(7) kHz/Pa is discussed. Our determination of the line centers reached a precision of 20 kHz. The light source can serve as a reference laser for lithium spectroscopy (2S-3P).

Improving Performance of Underwater Wireless Optical Communication Links by Channel Coding

Ferdaouss Mattoussi, Mohammad Khalighi, and Salah Bourennane

Doc ID: 315098 Received 08 Dec 2017; Accepted 15 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: We investigate the efficacy of error correcting codes in improving the performance of underwater wireless optical communication systems. For this purpose, the effectiveness of several coding schemes, i.e., the classical Reed-Solomon and a recent family of low-density parity check codes, is studied in the physical (PHY) and the upper layers assuming negligible water turbulence. The presented numerical results testify the interest of using efficient codes both at PHY and upper protocol layers although we are concerned by a non-fading channel. Furthermore, we discuss the choice of coding schemes and the appropriate degree of data protection in PHY and upper layers.

A comparative study between linear and non-linearfrequency modulated pulse-compressionthermography

Stefano Laureti, Giuseppe Silipigni, Luca Senni, Riccardo Tomasello, Pietro Burrascano, and Marco Ricci

Doc ID: 318212 Received 20 Dec 2017; Accepted 15 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: Pulse Compression Thermography is an emerging Non-Destructive technique whose effectiveness strictly dependson the choice of the coded excitations used to modulate the heating stimulus. In this paper, the features offrequency-modulated coded signals, i.e. chirps, have been tested for imaging thin Teflon defects embedded within acarbon fiber composite specimen. With the aim of maximizing the heat transferred within the sample, the use ofseveral optimized non-linear chirp signals has been also investigated and their defect detection capabilitycompared in terms of the maximum achievable Signal-to-Noise ratio.

Using turbulence scintillation to assist object ranging from a single camera viewpoint

Chensheng Wu, Jonathan Ko, JOSEPH COFFARO, Daniel Paulson, John Rzasa, Larry Andrews, Ronald Phillips, ROBERT CRABBS, and Christopher Davis

Doc ID: 318727 Received 03 Jan 2018; Accepted 15 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: Image distortions caused by atmospheric turbulence are often treated as unwanted noise or errors in many image processing studies. Our study, however, shows that in certain scenarios the turbulence distortion can be very helpful in enhancing image processing results. This manuscript describes a novel approach to use the scintillation traits recorded on a video clip to perform object ranging with reasonable accuracy from a single camera viewpoint. Conventionally, a single camera would be confused by the perspective viewing problem where a large object far away looks the same as a small object close by. When the atmospheric turbulence phenomenon is considered, the edge or texture pixels of an object tend to scintillate and vary more with increased distance. This turbulence-induced signature can be quantitatively analyzed to achieve object ranging with reasonable accuracy. Despite the inevitable fact that turbulence will cause random blurring and deformation of imaging results, it also offers convenient solutions to some remote sensing and machine vision problems which would be otherwise difficult.

Tunable Bragg defect mode in one-dimensional photonic crystal containing graphene-embedded defect layer

Behrooz Rezaei and Hossein Mahmoodzadeh

Doc ID: 320402 Received 22 Jan 2018; Accepted 14 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: Using the transfer matrix method, the transmission properties of defective one-dimensional photonic crystal is analyzed in the terahertz region. The defect layer is composed of graphene-embedded dielectric layer. We investigate the variation of defect mode's frequency as a function of graphene chemical potential for different values of incident angles. The numerical results show that the frequency of defect mode can be tuned effectively as the chemical potential of graphene nanolayers changes using an applied gate voltage. The present results can be useful in designing tunable graphene-based photonic devices such as filters and sensors in terahertz regions.

Optical Characterization of Porcine Articular Cartilage Using Polarimetry Technique with Differential Mueller Matrix Formulism

Ching-Min Chang, Yu-Lung Lo, Nghia-Khanh Tran, and Yu-Jen Chang

Doc ID: 315131 Received 06 Dec 2017; Accepted 14 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: A method is proposed for characterizing the optical properties of articular cartilage sliced from a pig’s thighbone using a Stokes-Mueller polarimetry technique. The principal axis angle (α), phase retardance (β), optical rotation angle (γ), circular diattenuation (R), diattenuation axis angle (θ), linear diattenuation (D), and depolarization index (∆) properties of the cartilage sample are all decoupled in the proposed analytical model. Consequently, the accuracy and robustness of the extracted results are improved. The glucose concentration, collagen distribution and scattering properties of samples from various depths of the articular cartilage are systematically explored via an inspection of the related parameters. The results show that the glucose concentration and scattering effect are both enhanced in the superficial region of the cartilage. By contrast, the collagen density increases with an increasing sample depth.

Switchable phase/intensity sensor made with ring-shaped and hexagonal ferroelectric domains

Luis Joel Mávita Granillo, Luis Rios, Citlali Minor, and Roger Cudney

Doc ID: 315819 Received 15 Dec 2017; Accepted 14 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: We present a device similar to a Shack-Hartmann sensor that can detect both the intensity distribution and wavefront of an incident wave. Its operation is based on the use of an array of electrically controllable Fresnel zone plates made in a ferroelectric crystal, lithium niobate. This sensor, which requires only one camera, can be quickly switched between intensity and phase detecting modes. Two kinds of arrays are shown: Fresnel zone plates with a few ring-shaped ferroelectric domains and plates made with nested hexagonal domains. Both arrays are suitable to be used in a Shack-Hartmann wavefront sensor; however, since in lithium niobate domains naturally tend to form hexagons it is easier to make hexagonal rather than ring-shaped domains, and consequently smaller zone plates can be produced. This allows to increase the number of zone plates and to reduce their focal length, which improves the fidelity of the reconstructed wavefront.

Multiresonance response in hyperbolic metamaterials

Bartosz Janaszek, Marcin Kieliszczyk, Anna Tyszka-Zawadzka, and Pawel Szczepanski

Doc ID: 315340 Received 11 Dec 2017; Accepted 13 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: In this paper we demonstrate a new class of anisotropic 1D hyperbolic metamaterials (HMMs) possessing multiresonant dispersion characteristics. With the help of an EMT-based model we analyze HMMs with unit cells composed of layers characterized by various plasma frequencies, revealing multiple resonance transitions corresponding to the critical absorptions points. In particular, we show that relative location of plasma frequencies of constituent materials and unit cell’s geometry determine the type of dispersion characteristics as well as spectral location of critical absorption points. Particularly, it is shown that a multispectral highly dispersive medium is achieved in a structure comprising layers where plasma resonances are closely located. Moreover, we present that pure metallic multilayer structure can exhibit hyperbolic dispersion. The obtained results possess a significant potential in applications where multispectral character is required, including phase-matching, multiple-point perfect absorption, as well as diffractionless imaging and focusing.

Performance analysis of triple asymmetrical opticalmultiple ring resonator with 1x3 input-outputwaveguide for application as optical filter

SUMAN RANJAN and SANJOY MANDAL

Doc ID: 313710 Received 17 Nov 2017; Accepted 13 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: Modelling of triple asymmetrical optical multiple ring resonator (TAOMRR) with 1x3 input-output waveguide hasbeen carried out in the present article and its performance as optical filter is analysed. The mathematicalmodelling of the proposed configuration is carried out in z-domain using delay line signal processing technique.Free spectral range (FSR), group delay and dispersion characteristic of the proposed TAOMRR is evaluated fromthe frequency response plot obtained in MATLAB from all the possible input-output port configuration. The fieldanalysis of the proposed configuration is realized using finite difference time domain (FDTD) method. The optimalcoupling coefficient obtained from the MATLAB simulation is used to design the various optical couplers in FDTDanalysis. The proposed configuration offers three outputs with different FSRs for single input port which greatlyenhances the data handling capabilities in communication network.

AOTF spectrometers in space missions

Oleg Korablev, Denis Belyaev, Yury Dobrolenskiy, Alexandr Trokhimovskiy, and Yuri Kalinnikov

Doc ID: 313083 Received 07 Dec 2017; Accepted 13 Feb 2018; Posted 14 Feb 2018  View: PDF

Abstract: Spectrometers employing acousto-optic tunable filters (AOTFs) rapidly gain popularity in space, and in particular on interplanetary missions. They allow for reducing volume, mass and complexity of the instrumentation. To date, space operations of eleven AOTF spectrometers are reported in the literature. They were used for analyzing ocean color, greenhouse gases, atmospheres of Mars and Venus, and for lunar mineralogy. More instruments for Moon, Mars and asteroid mineralogy, are in flight, awaiting launch, or in the state of advanced development. The AOTF are used in point (pencil-beam) spectrometers, for selecting échelle diffraction orders, or in hyper-spectral imagers and microscopes. We review the AOTF-employing devices flown in space or ready to set-off. The paper considers basic principles of the AOTF, science applications of the AOTF spectrometers, and describes developed instruments in some detail. We also address some advanced developments for future missions, and plans. In addition, we discuss lessons learned during instrument design, build, calibration and exploitation, advantages and limitations in implementing the AOTF-based systems in space instrumentation.

A cost-effective way to improve the optical properties of PMMA/PET light scattering materials: drop coalescence

Xiao LIu, Ziru Zhao, ying xiong, Ping Yi, and Shaoyun Guo

Doc ID: 315302 Received 11 Dec 2017; Accepted 13 Feb 2018; Posted 14 Feb 2018  View: PDF

Abstract: Herein, the dependence of the dispersed phase diameter on the shear history during melt processing is verified experimentally. We fabricated different kinds of Poly(methyl methacrylate)(PMMA)/Poly(ethylene terephthalate) (PET) blends by modifying the shear rate and shear time in a Torque Rhometer. Light scattering sheets (LSSs) were then prepared by compression molding with above blends. The transmittance of the light scattering sheet with a shear history of 8 minutes at 30rpm and then 20 minutes at 5rpm achieves 84.8% due to the drops coalescence and larger diameters of the PET scatterers in PMMA matrix, while the transmittance of a sheet with a shear history only at 30rpm is just 70.8%. In addition to high transmittance, the sheet also features high haze (beyond 92.5%) and tiny direct transmittance(less than 5%), which is vital for uniform illumination and glare protection from lasers and LEDs.

Study on Vibration Sensing Performance of Equal Strength Cantilever Beam Based on Excessively Tilted Fiber Grating

Bin-bin Luo, Wanmeng Yang, Xinyu Hu, Huafeng Lu, Shenghui Shi, M Zhao, Lu Ye, Lang Xie, Zhongyuan Sun, and Lin Zhang

Doc ID: 318366 Received 28 Dec 2017; Accepted 13 Feb 2018; Posted 14 Feb 2018  View: PDF

Abstract: An equal strength cantilever beam vibration sensor based on excessively tilted fiber grating (Ex-TFG) with light intensity demodulation is proposed. The basic principles and sensing characteristics of vibration sensing of equal strength cantilever beam and Ex-TFG, the combination of which is applied into vibration sensing, are analyzed. Ex-TFG is attached to the middle axis of an equal strength cantilever beam. As the vibration of a piezoelectric ceramic (PZT) causes equal strength cantilever beam to deform, the same and uniform deformation also occurs on Ex-TFG. Experimental results show that when the thickness of equal strength cantilever beam is 0.3mm and Ex-TFG is at TE polarization state, the sensing performance is the best, with the maximum acceleration sensitivity reaching 81.065mv•m-1•s2, and the FFT transformation main frequency components of the sensing signal accounting for more than 80%; besides, this sensor is stable in sensing performance, easy in demodulation, simple in structure, high in sensitivity, and easy in manufacture, applicable for the sensing and on-line monitoring of low-frequency vibration signals.

A light intensity and FOV controlled adaptive fluidiciris

chao liu and Di Wang

Doc ID: 318886 Received 04 Jan 2018; Accepted 13 Feb 2018; Posted 14 Feb 2018  View: PDF

Abstract: In this paper, we propose a light intensity and field of view (FOV) both controlled adaptive fluidic iris. A 90°twisted-nematic liquid crystal (TNLC) cell and two orthogonal polarizers are attached on the substrate. Whenapplied a voltage to TNLC, it can change phase of the incident light, leading to the light intensity changed. A blackmask was placed in the middle part of the chamber. When changing the hydraulic pressure from inlet and outlet,the black mask can move within the chamber. It is equivalent to changing the iris position along the optical axis. Sothe iris can control FOV in an optical system. The experiments show that the device can control the light intensityfrom 100% to 0% by applying the voltage of 9V on the TNLC cell. The proposed device can be applied in imagingsystems and optical attenuators.

Detection with Polychromatic X-ray Pencil Beam Illumination: Information-Theoretic Bounds

Vicha Treeaporn and Mark Allen Neifeld

Doc ID: 307108 Received 03 Oct 2017; Accepted 13 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: Non-destructive testing (NDT) by x-ray imaging is commonly used for finding manufacturing defects, cargo inspection or security screening. These tasks can be regarded as examples of a detection problem where a target is either present or not. Task Specific Information (TSI) (Neifeld, Ashok, and Baheti. J. Opt. Soc. Am. A, 24(12):B25, 2007; Ashok, Baheti, and Neifeld. Appl. Opt., 47 (25):4457, 2008) bounds, an information-theoretic based metric, are presented for a threat detection task. A system using poly-chromatic X-ray pencil beam object illumination and energy-resolving detectors for both absorption and diffraction measurements is employed for this task. Water and diesel are two liquids chosen as non-threat and threat materials, respectively, for this study. Three different threat class configurations are examined: a homogeneous object with fixed thickness, a homogeneous object with stochastic thickness, and a dual-material object (i.e. representing a target and clutter) with stochastic thickness where the threat material has a fixed thickness. We find for the threat class composed of a dual-material object that a minimum threat thickness of 4.5 cm is needed to achieve a desired TSI ≥ 0.7 using a joint absorption and diffraction measurement.

A Mach-Zehnder interferometric magnetic field sensor base on Photonic crystal fiber and Magnetic Fluid

ding zi, Hang-Zhou Yang, Xue-Guang Qiao, Pan Zhang, Qin Tian, Qiangzhou Rong, Nurul Nazal, Kok-Sing Lim, and Harith Ahmad

Doc ID: 314433 Received 29 Nov 2017; Accepted 12 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: A Mach-Zehnder interferometric magnetic field sensor based on photonic crystal fiber (PCF) and magnetic fluid(MF) was designed and experimentally demonstrated. The sensing probe consists of a single-mode-multimode (MM)-photonic crystal fiber (PCF)-single-mode (SM-MM-PCF-SM) fiber structure through arc fusion splicing. It was then laser engrave notch with the femtosecond laser so that the PCF cladding was selectively infilled MF. A well-defined interference pattern was obtained on account of the tunable refractive index of the MF in-filled PCF cladding. The transmission spectra of the proposed sensor under different magnetic field intensities have been measured and theoretically analyzed. The results show that the sensitivity of the proposed sensor can reach -0.13 dB∕mT in the magnetic field intensity between 1mT and 20 mT.

A continuously tunable optical Notch filter and Band Pass filtersystem that covers the VIS to NIR spectral range

Mi-Yun Jeong and Jin Yeob Mang

Doc ID: 314629 Received 29 Nov 2017; Accepted 12 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: Spatially continuous tunable optical Notch and Band Pass filter systems that cover the VIS and NIR spectral rangefrom ~460 nm to ~1,000 nm, are realized by combining left- and right-handed circular cholesteric liquid crystal wedgecells with continuous pitch gradient. The Notch filter system is polarization independent in all of the spectral range.The Band pass filter system case, when the left- and right-handed CLCs were arranged in a row, is polarizationindependent,while when they were arranged at right angles, they are polarization-dependent; furthermore, the fullwidthat half-maximum of the band pass filter can be changed reversibly from original band width 36 nm to 15 nm.Depending on the CLC materials, this strategy could be applied to the UV, VIS, and IR spectral range. Due to the highperformance in the broad spectral range, cost-effective facile fabrication process, simple mechanical control, and smallsize, it is expected that our optical tunable filter strategies could become one of the key parts of Laser-based Ramanspectroscopy, Fluorescence, Life science devices, Optical communication systems, astronomical telescopes, and soforth.

Fiber birefringence measurement by an external applied strain method and a polarimetric fiber laser sensor

Xiujuan Yu, Yuxiu Hu, xuefeng chen, Jintao Zhang, shengchun liu, and Yachen Gao

Doc ID: 314968 Received 05 Dec 2017; Accepted 12 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: In this work, a high-sensitivity and low-cost sensing scheme for measuring intrinsic and induced fiberbirefringence change is reported based on a polarimetric fiber laser sensor interrogated by beat frequencytechnique. The fiber birefringence measurement is achieved by an external applied strain method. A detailedtheoretical analysis of the principle for fiber birefringence measurement is carried out. Two alternative equationsare given for determining the change of fiber birefringence, which are very convenient for users to choose differentorder beat signals. To verify the performance of the sensing system, the external applied strain-induced fiberbirefringence change is measured experimentally. The experiment result shows that the fiber birefringenceexperiences a linear increase with the increase of applied strain. A strain response coefficient of 4.646×10-11/με isobtained. Furthermore, the repeatability and stability performances of the polarimetric fiber laser sensor are alsoinvestigated.

Analysis of freeform mirror systems based on thedecomposition of the total wave aberration into Zernikesurface contributions

Mateusz Oleszko and Herbert Gross

Doc ID: 318119 Received 19 Dec 2017; Accepted 12 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: The application of freeform elements in optical systemsincreases the number of variables available for correction.This creates the potential to design compact systemswith excellent imaging performance. However itis non-trivial to determine which configuration of thesystem to choose and where to place the freeform element,to obtain the best design. The knowledge ofaberration distribution in the system is very helpfulin answering these questions. In the following paper,we analyze Zernike surface contributions to thetotal wave aberration in non-symmetric freeform mirrorsystems using the method introduced in [Oleszkoet al., JOSAA Vol. 34(10), 1856-1864 (2017)]. We demonstratethe benefits of the proposed method in determiningeffective location of the freeform element and infinding critical differences between possible configurations.By analyzing surface contributions to the totalwave aberration characterized by Zernike fringe coefficients,it is possible to find solutions corrected for aberrationsof order higher than the order of coefficientsused for freeform sag contibution described with thesame Zernike polynomial set.

Effect of temperature on surface error and laser damage threshold for self-healing BK7 glass

Chu Wang, Hongxiang Wang, Lu Shen, Hou Jing, Qiao Xu, Jian Wang, Chen Xianhua, and Zhichao Liu

Doc ID: 313409 Received 14 Nov 2017; Accepted 12 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: Cracks caused during lapping and polishing process can decrease the laser-induced damage threshold (LIDT) of the BK7 glass optical elements, which would shorten the lifetime and limit the output power of the high-energy laser system. When BK7 glass is heated under appropriate conditions, the surface cracks can produce self-healing phenomena. In this paper, based on thermodynamics and viscous fluid mechanics theory, the mechanisms of crack self-healing were explained. The heat healing experiment was carried out, and the effect of humidity was analyzed. The multi-spatial-frequency analysis was used to investigate the effect of temperature on surface error for self-healing BK7 glass, and the lapped BK7 glass specimens before and after heat healing was detected by interferometer and atom force microscopy. The low spatial frequency error was analyzed by peak to valley (P-V) and root mean square (RMS), the mid spatial frequency error was analyzed by power spectral density (PSD), and the high spatial frequency error was analyzed by surface roughness. The results showed the optimal heating temperature for BK7 was 450°C, and when heating temperature was higher than the glass transition temperature (555°C), the surface quality decreased a lot. The laser damage test was carried out, and the specimen heated at 450°C showed an improvement in LIDT.

Automatic Cell Identification and Visualization usingDigital Holographic Microscopy with Head MountedAugmented Reality Devices

Timothy O'Connor, SIDDHARTH RAWAT, Adam Markman, and Bahram Javidi

Doc ID: 314327 Received 28 Nov 2017; Accepted 10 Feb 2018; Posted 12 Feb 2018  View: PDF

Abstract: We propose a compact imaging system that integrates augmented reality head mounted devices with digitalholographic microscopy for automated cell identification and visualization. A shearing-interferometer is used torecord holograms of biological cells using customized smart glasses containing an external camera. After imageacquisition, segmentation is performed to isolate regions of interest containing biological cells in the field-of-viewfollowed by digital reconstruction of the cells, which is used to generate a 3D pseudocolor optical path lengthprofile. Morphological features are extracted from the cell’s optical path length map including mean optical pathlength, coefficient of variation, optical volume, projected area, projected area to optical volume ratio, cell skewnessand cell kurtosis. Classification is performed using the random forest classifier, support vector machines, and Knearestneighbor and the results are compared. Finally, the augmented reality device displays the cell’spseudocolor 3D rendering of its optical path length profile, extracted features, and the identified cell’s type or class.The proposed system could allow a healthcare worker to quickly visualize cells using augmented reality smartglasses and extract the relevant information for rapid diagnosis. To the best of our knowledge, this is the firstreport on the integration of digital holographic microscopy with augmented reality devices for automated cellidentification and visualization.

Physical optics based diffraction coefficient for a wedge with different face impedances

Yusuf Umul

Doc ID: 318854 Received 03 Jan 2018; Accepted 09 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: A new diffraction field expression is introduced with the aid of the modified theory of physical optics for a wedge with different face impedances. First of all the scattered geometrical optics fields are determined when both faces of the wedge is illuminated by the incident wave. The geometrical optics waves are expressed in terms of the sum of two different fields that occur for different impedance wedges. The diffracted fields are determined for the two cases separately and the total diffracted field is obtained as a sum of these waves. The uniform field expressions are obtained and the resultant fields are compared with the solution of Maliuzhinets numerically.

Demodulation of moire fringes in digital holographic interferometry using extended Kalman filter

Jagadesh Ramaiah, Pramod Rastogi, and G Rajshekhar

Doc ID: 310218 Received 27 Oct 2017; Accepted 09 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: The article presents a method for extracting multiple phases from a single moire fringe pattern in digital holographic interferometry. The method relies on component separation using singular value decomposition and extended Kalman filter for demodulating moire fringes.The Kalman filter is applied by modeling the interference field locally as a multi-component polynomial phase signal, and extracting the associated multiple polynomial coefficients using state space approach. In addition to phase, the corresponding multiple phase derivatives can also be simultaneously extracted using the proposed method.The applicability of the proposed method is demonstrated using simulation and experimental results.

A Novel Multi-Objective Optimization Framework forDesigning Photonic Crystal Sensors

Mohammd Javad Safdari, Seyed Mohammad Mirjalili, Pablo Bianucci, and Xiupu Zhang

Doc ID: 314319 Received 27 Nov 2017; Accepted 09 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: In this paper, a novel framework for designing optimized photonic crystal (PhC) sensors has been proposed. Thecomplexity of such structures have resulted in the lack of an analytical method to design the structures. Therefore,this framework aims to provide a comprehensive and automatic method to find the best values for the structuralparameters without human involvement. The framework is explained with an example of designing a PhC liquidsensor. In the framework, an optimizer called Multi-Objective Gray Wolf Optimizer is utilized. However, a diverserange of multi-objective optimizer algorithms could be utilized. The results show that the proposed framework candesign any kind of PhC sensor. Simplicity, being straightforward, and no human involvements are the advantages ofthe proposed framework. In addition, a significantly wide range of optimal designs will be found which are suitablefor general and specific applications.

Intensity, Phase and Polarization of Vector Bessel Vortex Beam Through Multilayered Isotropic Media

Haiying Li, Farideh Honary, Jiajie Wang, Zhen-Sen Wu, and Lu Bai

Doc ID: 308836 Received 09 Oct 2017; Accepted 09 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: This paper investigates the characteristics of reflected and transmitted fields of a vector Bessel vortex beamthrough multilayered isotropic media on the basis of the vector angular spectrum expansion, and presents theeffects of media on intensity, phase and polarization. The method is verified by studying the reflection andtransmission on a single interface at the vertical incidence. For both paraxial and non-paraxial incident beam cases,numerical simulations of the field components and the time-averaged Poynting vector power density of thereflected and the transmitted beams for the three-layered media are presented and discussed in detail. It is shownthat as the incident angle increases, the magnitude distribution of the reflected beams illustrates significantdistortions and no longer represents similar patterns to that of incident beam, whereas the magnitude distributionof the transmitted beams can maintain similar profiles to the incident beam, apart from the notable distortion ofthe central ring. For the same incident angle, the effects of media on the magnitude distribution for the nonparaxialcase are more evident than those for the paraxial case. The results of phase distribution and polarizationof the reflected and transmitted fields show that as the incident angle increases, the distortion of the phasedistribution and polarization for the reflected fields are more significant, and the topological charge cannotpreserve.

Extended focus depth for Gaussian beam using binaryphase diffractive optical elements

Bencheikh Abdelhalim, Michael Fromager, and Kamel Ait-Ameur

Doc ID: 312319 Received 30 Oct 2017; Accepted 09 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: A novel technique to improve the focus depth of a Gaussian beam is presented in this paper. The improvement is based on twosteps beam shaping using a cascade of binary phase diffractive optical elements (BPDOE). The first BPDOE transforms the incidentGaussian beam into a high-order radial Laguerre-Gaussian beam LGp0. Then the second BPDOE rectifies the obtained LGp0 beamand gives rise to a quasi-Gaussian one in the focal plane of a converging lens. This resulting quasi-Gaussian beam exhibits a lowerdivergence and larger focus depth compared to the pure Gaussian beam having the same beam-waist. These results open newpossibilities in laser beam manufacturing and micromachining, and applications which needs an extended focus depth.

Automated exploitation of sky polarization imagery

firooz sadjadi and Cornell Chun

Doc ID: 313219 Received 13 Nov 2017; Accepted 09 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: We propose an automated method for detecting neutral points in the sun lit sky. Up to now detectingthese singularities has been done manually. Results are presented of the application of this method ona limited number of polarimetric images of the sky captured with a camera and rotating polarizer. Theresults are significant because determining the neutral points may aid in the determination of the solarposition when the sun is obscured that is useful in a number of applications such as meteorology andpollution detection and characterization.

Investigation of impact and spreading of molten nanosized gold droplet on solid surfaces

Daozhi Shen, Guisheng Zou, Lei Liu, Aiping Wu, Walter Duley, and Yunhong Zhou

Doc ID: 318713 Received 03 Jan 2018; Accepted 09 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: Understanding the impact dynamics and spreading of molten nanosized droplets on a solid surface is a crucial step towards the design and control of nano-fabrication in many novel applications of nanotechnology. In this context, molecular dynamic (MD) simulations have been conducted to compute temperature and dynamic contact angles of nano-droplets during impact. The evolution of the morphology of a molten metallic nano-droplet impacting on a substrate has been studied using a combination of experimental and simulation techniques. Femtosecond laser has been used to transfer nanosized gold droplet. Droplet morphology calculated in MD simulations is found to be in good agreement with that seen in Scanning Electron Microscopy (SEM) images. It is found that the spreading of nanoscale molten gold droplets upon impact is enhanced by increasing the droplet impact energy. As in micron and sub-micron systems, heat transfer between the droplet and the solid substrate is found to be the primary factor in determining the morphology of the subsequent deposit. However, the process is also strongly affected by the wettability of the substrate, unlike that occurring in the impact of larger particles. As observed in experimental data, MD simulation results show that a high droplet-substrate heat transfer rate together with increased wettability of the substrate facilitates spreading and results in a thinner metal deposit after solidification.

Passively Q-switched solid-state Tm:YAG laserusing topological insulator Bi2Te3 as saturableabsorber

Pan Gao, Haizhou Huang, xihu wang, huagang liu, Huang Jianhong, wen weng, shutao dai, jinhui li, and Wenxiong Lin

Doc ID: 313852 Received 22 Nov 2017; Accepted 09 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: We demonstrated a passively Q-switched solid-state Tm:YAG laser using topological insulator (TI) Bi2Te3 as thesaturable absorber (SA) for the first time, to the best of our knowledge. The Q-switched laser pulses were obtainedwith the minimum pulse width of 382 ns, the maximum pulse energy of 4.8μJ , the maximum average output powerof 272 mW and a pulse repetition rate of 57.67 kHz. The results indicate that Bi2Te3 can be a promising kind ofsaturable absorber in the 2 μm wavelength region.

Multiplanar imaging properties of Theon sieves

Shouying Xu, Junyong Zhang, shenlei zhou, Yayao Ma, Songxian Wang, li Zhang, Jing Xie, and Jianqiang Zhu

Doc ID: 315585 Received 12 Dec 2017; Accepted 08 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: Greek ladders with diffraction-limited array foci provide a probability to realize array imaging with equal intensity.Here taking the ancient Theon sequence as an example, we design the optical structure and have measured thefocusing properties by digital holography. Then verify the multiplanar imaging with different magnification byexperiment. The experimental results agree well with the theoretical analysis. In addition, bi-Fourier planesfiltering technology is proposed to solve the problem of crosstalk between different imaging planes to furtherimprove the imaging resolution. Therefore, we can freely design the focal length of the bifocal lens to achieve highqualityimaging at different resolutions. As a kind of amplitude-only diffractive lens, multifocal imaging provides apossibility of application in array biological imaging, ophthalmology and optical zoom system.

Holographic Waveguide Heads-Up Display for Longitudinal Image Magnification and Pupil Expansion

Colton Bigler, Pierre-Alexandre Blanche, and Kalluri Sarma

Doc ID: 312726 Received 06 Nov 2017; Accepted 08 Feb 2018; Posted 08 Feb 2018  View: PDF

Abstract: The field of view of traditional heads-up display systems is limited by the size of the projection optics. Our research is focused on overcoming this limitation by coupling image bearing light into a waveguide using holographic elements, propagating the light through that waveguide, and extracting the light several times with additional holographic optical elements. With this configuration, we demonstrated both longitudinal magnification and pupil expansion of the heads-up display. We created a ray trace model of the optical system to optimize the component parameters and implemented the solution in a prototype that demonstrates the merit of our approach. Longitudinal magnification is achieved by encoding optical power into the hologram injecting the light into the waveguide, while pupil expansion is obtained by expanding the size of the hologram extracting the light from the waveguide element. To ensure uniform intensity of the image, the diffraction efficiency of the extracting hologram is modulated according to the position. Our design has a 12° x 8° Field of View at a viewing distance of 10", with infinite longitudinal magnification and a 1.7x lateral pupil expansion.

Molecular vibrations of Bisphenol ‘S’ revealed byFTIR spectroscopy and their correlation withBisphenol ‘A’ disclosed by Principal ComponentAnalysis

Ramzan Ullah and Xiangzhao Wang

Doc ID: 318751 Received 08 Jan 2018; Accepted 08 Feb 2018; Posted 08 Feb 2018  View: PDF

Abstract: Bisphenol ‘S’ (BPS), a common replacement for Bisphenol ‘A’ (BPA) after it’s ban in food contact applications, isstudied by FTIR spectroscopy (400 cm-1 to 6800 cm-1). Identified molecular vibrations are assigned based onDensity Functional Theory (DFT) calculations. Suspected to be as toxic as BPA, Principal Component Analysis isused to find the possible correlation among their molecular vibrations. We have found frequencies showing aconnection between these two materials by molecular vibrations helping not only to categorize such materials butalso to find the origin of their toxicity.

Performance of heterodyne DPSK underwater wireless optical communication systems in Gamma-Gamma-distributed turbulence

Yuqing Fu and Yongzhao Du

Doc ID: 305555 Received 24 Aug 2017; Accepted 08 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: The analytical expressions for the average bit error rate and the outage probability of a heterodyne differentialphase shift keying (DPSK) underwater wireless optical communication (UWOC) system are derived with properconsideration of all of the channel degrading effects, including absorption, scattering, and turbulence-inducedfading. And the scintillation index of spherical wave is evaluated in order to quantify the underwater systemperformance in strong turbulence regime. The spherical wave propagates through the strong underwaterturbulence environment is modeled as Gamma-Gamma distribution. Then the system performance is simulatedfor various variations of the underwater turbulence, i.e., the rate of dissipation of kinetic energy per unit mass offluid, the ratio of temperature to salinity contributions to the refractive index spectrum, and the UWOC system linklength. The results show that the analytical expressions for describing the system performance are valid.

Performance prediction of p-i-n HgCdTe longwavelength infrared HOT photodiodes

Antoni Rogalski, Małgorzata Kopytko, and Piotr MARTYNIUK

Doc ID: 320488 Received 23 Jan 2018; Accepted 07 Feb 2018; Posted 08 Feb 2018  View: PDF

Abstract: Recently, An enhanced computer program has been applied to explain in detail the influence of different recombinationmechanisms (Auger, radiative and Shockley-Read-Hall) on the performance of high operation temperature long wavelengthinfrared p-i-n HgCdTe heterojunction photodiodes. It is shown that photon recycling effect drastically limits the influence ofradiative recombination on the performance of small pixel HgCdTe photodiodes. The computer program is based on a solutionof the carrier transport equations, as well as the photon transport equations for semiconductor heterostructures. Both thedistribution of thermal carrier generation and recombination rates and spatial photon density distribution in photodiodestructures have been obtained. In comparison with two previously published papers in Journal of Electronics Materials (Lee etal., DOI: 10.1007/s11664-016-4566-6 and Schuster et al., DOI: 10.1007/s11664-017-5736-x) our paper indicates an additionalinsight on ultimate performance of LWIR HOT HgCdTe arrays with pixel densities that are fully consistent with background- anddiffraction-limited performance due to system optics.

Low-density point eating algorithm for surface reconstruction from dense scans

Bao-Quan Shi, Xiao-Yuan Feng, Li-Kun Zhang, Chen-Song Yao, and JunJie Ye

Doc ID: 312741 Received 03 Nov 2017; Accepted 07 Feb 2018; Posted 08 Feb 2018  View: PDF

Abstract: We present a low-density point eating algorithm for surface reconstruction from dense scans. Firstly, the density map for each scan is estimated and the boundary densities are down-weighted. Subsequently, the poorly scanned low-density overlapping points are eaten up based on an user-defined threshold. Finally, the overlapping areas are thinned by using the MLS operator and the homogeneous points are weighted averaged. The new algorithm can extract smooth and detailed point set surfaces that as close as possible to the ground truth. The good performance of the new algorithm is demonstrated by comparison with several advanced surface reconstruction algorithms.

Quantitative birefringence microscopy with collinearly propagatingorthogonally polarized beams

Sonali Chakraborty, Kallol Bhattacharya, and S. Sarkar

Doc ID: 314054 Received 22 Nov 2017; Accepted 07 Feb 2018; Posted 08 Feb 2018  View: PDF

Abstract: Full-field evaluation of spatially varying birefringence is realized by allowing two mutually orthogonallypolarized collinearly propagating laser beams to be incident on a birefringent sample. This is achieved by use of amodified Sagnac Interferometer. A half wave plate is placed at the exit path of the interferometer to rotate theorientations of the orthogonally polarized light beams as required. Amplitude components of the light emerged fromthe birefringent object is then selected and/or combined by a polarizer and intensities for required orientation of thehalf wave plate and the analyzer are digitally recorded. It is shown that a maximum of four frames of intensity dataare sufficient for complete evaluation of birefringence. The proposed technique is aimed towards birefringencemeasurements in microscopic biological specimens where the magnitude of retardation lies in the range of 0 to πradians. Simulated and experimental results are presented.

Cross sectional TEM study of subsurface damage inSPDT machining of Ge optics

Dusan Korytar, Zdenko Zápražný, Claudio Ferrari, Cesare Frigeri, Matej Jergel, Igor Maťko, and Jozef Kečkeš

Doc ID: 315613 Received 22 Dec 2017; Accepted 07 Feb 2018; Posted 08 Feb 2018  View: PDF

Abstract: In addition to surface roughness and shape precision the subsurface damage (SSD) generated by single pointdiamond turning (SPDT) of Ge and Si crystal optics is of increasing importance with decreasing the wavelengthfrom infrared through visible, UV, to X-ray. There are various components of SSD, e.g. microcracks, dislocations,strain, and a near surface amorphous layer and there are also several techniques to evaluate various componentsof SSD. Cross sectional transmission electron microscopy (XTEM) is expensive and not often directly used in opticslaboratory. However, because of its very high sensitivity to SSD and down to atomic resolution, it is often used asexternal service for developing SPDT technology and other surface processing techniques. It is shown in the paperthat improper sample preparation can generate near surface amorphization. Measures to avoid this artifact anda test of reliability of XTEM sample preparation are proposed.

Photothermoplastic recording media and its application in the holographic method of determination of refractive index of liquid and gaseous objects

Nicolay Davidenko, Irina Davidenko, Valeriy Pavlov, Nicolay Chuprina, Kravchenko Victor, Nicolay Kuranda, Elena Mokrinskaya, and Sergey Studzinsky

Doc ID: 313280 Received 13 Nov 2017; Accepted 06 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: The photothermoplastic medium based on the films of photosensitive polymeric composites with semiconductor properties is developed for application in optical information recording and storage, in holographic interferometry as well as for medical purposes. This medium was used in the modified holographic device for determination of the refractive index of homogeneous and inhomogeneous liquid and gaseous objects. The technique and holographic equipment were modified by employing the specially developed and produced transparent cuvette of special shape. Method of “phase steps” was used for the interferograms processing. Experimentally demonstrated precision of the measurements is not less than 10-5.

Binary wavefront optimization using simulated annealing algorithm

Longjie Fang, Haoyi Zuo, Zuogang Yang, Xicheng Zhang, Jinglei Du, and Lin Pang

Doc ID: 315772 Received 14 Dec 2017; Accepted 06 Feb 2018; Posted 07 Feb 2018  View: PDF

Abstract: We propose an idea using simulated annealing algorithm for amplitude modulation to focus light through disordered media. Using 4096 independently controlled segments of incident wavefront, the intensity of the target signal is 73 times enhanced over the original intensity of the same output channel. The simulated annealing algorithm and existing amplitude control algorithms for focusing through scattering media are compared by the experiment. It is found that simulated annealing algorithm achieves the highest enhancement when the number of iterations required for optimization is the same.

A LED Light Design Method for High Contrast andUniform Illumination Imaging in Machine Vision

Xiaojun Wu and Guangming Gao

Doc ID: 319341 Received 09 Jan 2018; Accepted 06 Feb 2018; Posted 07 Feb 2018  View: PDF

Abstract: In machine vision, illumination is very critical to determinethe complexity of the inspection algorithms.Proper lights can obtain clear and sharp images withthe highest contrast and low noise between the interestedobject and the background, which is conducive tothe target being located, measured, or inspected. Contraryto the empirically based trial and error conventionto select the off-the-shelf LED light in machine vision,an optimization algorithm for LED light design is proposedin this paper. It composes of the contrast optimizationmodeling and the uniform illumination technologyfor non-normal incidence(UINI). The contrastoptimization model is built based on the surface reflectioncharacteristics, e.g. the roughness, the reflective index,and light direction, etc. to maximize the contrastbetween the features of interest and the background.The UINI can keep the uniformity of the optimizedlighting by the contrast optimization model. The simulationand experimental results demonstrate that optimizationalgorithm is effective and suitable to produceimages with the highest contrast and uniformity, whichis very inspirational to the design of LED illuminationsystem in machine vision.

Evaluating an Image Based Multi-angle BRDF Measurement Setup

Aditya Sole, Ivar Farup, Peter Nussbaum, and Shoji Tominaga

Doc ID: 307297 Received 27 Sep 2017; Accepted 05 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: We evaluate an image based multi-angle BRDF measurement setup by comparing it against measurements from two commercially available table top gonio-spectrophotometers. The image based setup uses an RGB camera to perform bidirectional measurements of the sample material. We use a conversion matrix to calculate luminance from the captured data. The matrix is calculated using camera spectral sensitivities that are measured with a monochromator. Radiance factor of the sample material is measured using commercially available tabletop gonio-spectrophotometer and compared against measurements made using the image based setup in the colorimetric domain. The measurement setup is validated by comparing the measurements performed using a gonio-spectrophotometer. Uncertainty and error propagation is calculated and taken into account for validation. The sample material measured is wax based ink printed on packaging paper substrate commonly used in print and packaging industry. Results obtained show that the image based setup can perform bidirectional luminance measurements with a known uncertainty. The gonio-spectrophotometer measurements lie within the uncertainty of the measurements performed by the image based measurement setup. The setup can be used to perform bi directional luminance measurements on samples with properties similar to the samples used in this article.

Randomizing Phase to Remove Acousto-Optic Device Wiggle Errors for High-Resolution Optical Tweezers

Andrew Baker, Cho-Ying Chuang, Miles Whitmore, and Matthew Comstock

Doc ID: 314565 Received 29 Nov 2017; Accepted 05 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: Acousto-optic (AO) devices have been used extensively in optical tweezers because of their flexibility and speed, however these devices have trap positioning inaccuracies that limit their usefulness especially for high-resolution applications. We show that these inaccuracies are due to interference patterns within the AO device sound fields. We have devised a method that removes these inaccuracies by reducing the coherence of the sound fields by directly controlling and randomizing the phase of the radio frequency (RF) voltage input signal. We demonstrate that the trapping inaccuracies are eliminated, for both constant trap position and force-ramp measurements and that no additional noise is added. We show that this random phase method is applicable to both acousto-optic modulator and deflector type devices and can be easily integrated via software upgrade into existing instruments.

LIBS-based detection of metal particles releasedinto air during combustion of solid propellants

Morgan O'Neil, NICHOLAS NIEMIEC, ANDREW Demko, Eric Petersen, and Waruna Kulatilaka

Doc ID: 309323 Received 17 Oct 2017; Accepted 04 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: Numerous metals and metal compounds are often added to propellants and explosives to tailor their propertiessuch as heat release rate and specific impulse. When these materials combust, these metals can be released into theair, causing adverse health effects such as pulmonary and cardiovascular disease, particulate-matter-inducedallergies, and cancer. Hence, robust, field-deployable methods are needed to detect and quantify these suspendedmetallic particles in air, thereby identify their sources, and develop mitigation strategies. Laser-inducedbreakdown spectroscopy (LIBS) is a technique for elemental detection, commonly used on solids and liquids. Inthis study, we explored nanosecond-duration LIBS for detecting airborne metals during reactions of solidpropellant strands, resulting from additives of aluminum, copper, lead, lead stearate, and mercury chloride. Usingthe second harmonic of a 10-ns-duration 10-Hz, Nd:YAG laser, plasma was generated in the gas-phase exhaustplume of burning propellant strands containing the target metals. Under the current experimental conditions, thens-LIBS scheme was capable of detecting aluminum at concentrations of 5%, 10%, and 16% by weight in thepropellant strand. As the weight percentage increased, the LIBS signal was detected by more laser shots, up to apoint where the system transition from being non-homogeneous to a more-uniform distribution of particles.Further measurements and increased understanding of the reacting flow field are necessary to quantify the effectsof other metal additives besides aluminum.

Generalized curved beam back projection method for near-infrared imaging using Banana Function

Tapan Das, B P V Dileep, and Pranab Dutta

Doc ID: 312749 Received 03 Nov 2017; Accepted 04 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: Near-infrared Imaging (NIRI) is a sub-surface imaging having tradeoff in recovery accuracy whereas Diffuse Optical Tomography (DOT) images tissue up-to several centimetres. However, DOT reconstruction has stability issue due to inverse problem. This paper proposes a generalized continuous wave technique to image objects of dimension (4-6) cm comparable to DOT. A semi-analytic banana function is fitted for approximating photon path and fit parameter thus obtained give penetration depth of each channel. This serves as imaging operator for reconstruction by back projecting calculated absorption changes along these curved channels without solving inverse problem. Here TOAST++ simulations, wax phantom experiments, finger joint imaging are carried out. The method is efficient, reliable, and suitable for practical applications.

One lens optical correlation: application to facerecognition

Maher Jridi, thibault Napoleon, and Ayman Alfalou

Doc ID: 312381 Received 31 Oct 2017; Accepted 04 Feb 2018; Posted 08 Feb 2018  View: PDF

Abstract: Despite its extensive use, the traditional 4f VLC optical setup can be further simplified. We propose a lightweightcorrelation scheme where the decision is taken in the Fourier plane. For this purpose, the Fourier plane isadapted and used as a decision plane. Then, the offline phase and the decision metric are re-examined in order tokeep a reasonable recognition rate. The benefits of the proposed approach are numerous: (1) it overcomes theconstraints related to the use of a second lens; (2) the optical correlation setup is simplified; (3) themultiplication with the correlation filter can be done digitally, which offers a higher adaptability according to theapplication. Moreover, the digital counterpart of the correlation scheme is lighten since with the proposedscheme we get rid of the IFT calculation. To assess the performance of the proposed approach, an insight intodigital hardware resources saving is provided. It is found that the proposed method involves nearly 100 timesless arithmetic operators. Moreover, from experimental results in the context of face verification-basedcorrelation, we demonstrate that the proposed scheme provides comparable or better accuracy than thetraditional method. One interesting feature of the proposed scheme is that it could greatly outperforms thetraditional scheme for face identification application in terms of sensitivity to face orientation. The proposedmethod is found to be digital/optical implementation-friendly which facilitates its integration on a very broadrange of scenarios.

Simultaneous polarimeter retrievals of microphysicalaerosol and ocean color parameters from the “MAPP”algorithm with comparison to high spectral resolutionlidar aerosol and ocean products

Snorre Stamnes, Chris Hostetler, Richard Ferrare, Sharon Burton, Xu Liu, Johnathan Hair, Yongxiang Hu, Andrzej Wasilewski, William Martin, Bastiaan van Diedenhoven, Jacek Chowdhary, Ivona Cetinic, Larry Berg, Knut Stamnes, and Brian Cairns

Doc ID: 315368 Received 11 Dec 2017; Accepted 04 Feb 2018; Posted 22 Feb 2018  View: PDF

Abstract: We present an optimal estimation based retrieval framework, the Microphysical Aerosol Properties fromPolarimetry (MAPP) algorithm, designed for simultaneous retrieval of aerosol microphysical propertiesand ocean color bio-optical parameters using multi-angular total and polarized radiances. Polarimetricmeasurements from the airborne NASA Research Scanning Polarimeter (RSP) were inverted by MAPPto produce atmosphere and ocean products. The RSP MAPP results are compared with co-incident lidarmeasurements made by the NASA High Spectral Resolution Lidar HSRL-1 and HSRL-2 instruments.Comparisons are made of the aerosol optical depth (AOD) at 355 and 532 nm, lidar column-averaged measurementsof the aerosol lidar ratio and Ångstrøm exponent, and lidar ocean measurements of the particulatehemispherical backscatter coefficient and the diffuse attenuation coefficient. The measurements werecollected during the 2012 Two-Column Aerosol Project (TCAP) campaign and the 2014 Ship-Aircraft BioOpticalResearch (SABOR) campaign. For the SABOR campaign, 73% RSP MAPP retrievals fall within± 0.04 AOD at 532 nm as measured by HSRL-1, with an R value of 0.933 and root-mean-square deviationof 0.0372. For the TCAP campaign, 53% of RSP MAPP retrievals are within 0.04 AOD as measured byHSRL-2, with an R value of 0.927 and root-mean-square deviation of 0.0673. Comparisons with HSRL-2AOD at 355 nm during TCAP result in an R value of 0.959 and a root-mean-square deviation of also 0.0694.The RSP retrievals using the MAPP optimal estimation framework represent a key milestone on the pathto a combined lidar+polarimeter retrieval using both HSRL and RSP measurements.

A method to measure 3-D deformation using defocusimages of objects with artificial speckle features

Jiong Qian, Qin-Zhi Fang, QinWei Hu, and Li Jin

Doc ID: 308858 Received 09 Oct 2017; Accepted 03 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: A novel method to measure three dimensional deformation based on defocus images of an object has been presentedin the paper. To do this, the images of an object with artificial speckle features are taken by a camera.The in-plane coordinates of the points on specimen surface are obtained according to the camera setup parametersand the defocused distance. The blur band width on the edges of surface textures is used as a parameterto evaluate the blur degree of an image. The depth dimension is obtained by the relationship of the defocuseddistance and the blur degree. The relationship has been given theoretically and experimentally. Digital imagecorrelation (DIC) method is used to trace each point on the specimen surface before and after deformation.Then three dimensional deformation can be obtained according to the displacement of each point. The reliabilityof the method is validated by two experiments.

In-depth photoluminescence spectra of pure CIGS thin-films

Jacopo Parravicini, Maurizio Acciarri, Matteo Murabito, Alessia Le Donne, Andrea Gasparotto, and Simona Binetti

Doc ID: 313982 Received 23 Nov 2017; Accepted 02 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: Photoluminescence spectra of pure CIGS thin films with different Ga in-depth gradients are systematically investigated. Pure Na-free films are prepared with an innovative hybrid deposition technique, whose optical luminescence emission is analyzed as a function of the depth and is correlated to the radiative intrinsic defects of the material. Finally, the highlighted features are correlated with the performances of test solar cells prepared with the same growths.

Spike Encoding and Storage Properties in Mutually-Coupled VCSELs Subject to Optical Pulse Injection

Yahui Zhang, Shuiying Xiang, Junkai Gong, Xingxing Guo, Aijun Wen, and Yue Hao

Doc ID: 313541 Received 15 Nov 2017; Accepted 01 Feb 2018; Posted 01 Feb 2018  View: PDF

Abstract: The generation and storage properties of different spike codes in vertical-cavity surface-emitting lasers with anembedded saturable absorber (VCSELs-SA) are investigated numerically. The results show that different spikecodes are generated by injecting an optical pulse into one single VCSEL-SA, and can be stored in two mutuallycoupledVCSELs-SA. In particular, in the case of the generation of spike codes, the effects of the input strength andthe temporal duration of the input optical pulse are studied; in the case of the storage of spike codes, the roles ofthe coupling weight and the coupling delay between the two mutually-coupled VCSELs-SA are examined.Simulations uncover that spikes can be triggered if the input strength and the temporal duration are exceeded thethreshold values, and larger values of the input strength and the temporal duration are beneficial for generatingmore spikes. Moreover, successful storage of a perfectly formed train of spike codes in two mutually-coupledVCSELs-SA can also be realized provided that the coupling weight and the coupling delay are larger than thecorresponding threshold values.

High sensitivity birefringent and single layer coatingphotonic crystal fiber biosensor based on surfaceplasmon resonance

Min Liu, Xu Yang, Ping Shum, and Hongtao Yuan

Doc ID: 314039 Received 22 Nov 2017; Accepted 01 Feb 2018; Posted 02 Feb 2018  View: PDF

Abstract: A birefringent single layer coating photonic crystal fiber (PCF) biosensor based on the surface plasmon resonance(SPR) is proposed to realize high sensitivity, which is easy to implement in that only Au is deposited externally. Thebirefringent nature of the structure provides the sensor with high sensitivity. The results show that the biosensorcan obtain the wavelength sensitivity of 15180 nm/RIU and high linearity with the analyte RI range of 1.40–1.43,corresponding to the resolution of 5.6818 × 10–6 RIU. Owing to the high sensitivity and simple structure, theproposed sensor can find important applications in biochemical and biological analyte detection.

Comprehensive design and calibration of an evenaspheric quarter-wave plate for polarization pointdiffraction interferometry

Yao Li, Yongying Yang, Chen Wang, Yuankai Chen, Yihui Zhang, and Jian Bai

Doc ID: 314913 Received 04 Dec 2017; Accepted 01 Feb 2018; Posted 02 Feb 2018  View: PDF

Abstract: A polarization point diffraction interferometry (PPDI) system, adopting a specially designed even aspheric quarterwaveplate (EAQWP) in the test path, is proposed for low-reflectivity and high-numerical-aperture sphericalsurface testing. In terms of the low-reflectivity mirror measurement, the obtained poor fringes contrast, which cansignificantly affect the measurement accuracy, can be improved by the polarization characteristic of the EAQWP.Simultaneously, the wavefront distortion, especially larger in high-NA measurement, can be greatly reduced due tothe even aspheric surface design instead of plane. In addition, the pose error introduced by EAQWP isdemonstrated in detail and a difference restoration model is built to calibrate it. Consequently, the location of theEAQWP is fixed in the test path after calibrating the pose error, having no need to be adjusted with the change ofthe spherical mirror under test, which facilitates the system alignment in practical optical shop testing. Ultimately,the surface error of a spherical mirror with a low-reflectivity of 0.04 and a high-NA of 0.5 is measured with PPDI.Experimental results are validated to be in a good agreement with that of ZYGO interferometer.

Carbon-based Fresnel optics for hard X-ray astronomy

Christoph Braig and Ivo Zizak

Doc ID: 309772 Received 23 Oct 2017; Accepted 31 Jan 2018; Posted 05 Feb 2018  View: PDF

Abstract: We investigate the potential of large-scale diffractive-refractive normal-incidence transmission lenses for the development of space-based hard X-ray telescopes with an angular resolution in the range of micro- to milli-arcseconds over a field of view which is restricted by the available detector size. Coherently stepped achromatic lenses with diameters up to 5 m for compact apertures and 13 m in the case of segmentation provide an access to spectrally resolved imaging within keV-wide bands around the design energy between 10 keV and 30 keV. Within an integration time of 10⁶ s, a photon-limited 5σ sensitivity down to 1/10⁹ -1/10⁷ per (s cm² keV) can be achieved, depending on the specific design. An appropriate fabrication strategy, feasible with nowadays micro-optical technologies, is considered and relies on the availability of high-purity Carbon or polymer membranes. X-ray fluorescence measurements of various commercially available Carbon-based materials prove for most of them a virtually negligible contamination by critical trace elements such as transition metals on the ppm level.

Registration for Images in the Presence of Additive and Multiplicative Fixed-Pattern Noise

Colm Lynch and Martin Devaney

Doc ID: 306473 Received 07 Sep 2017; Accepted 31 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: Image registration under conditions of fixed-pattern noise is a difficult problem which has not been solved in the literature. While traditional registration methods are adequate for additive random noise, these are not suited to spatially invariant noise that is additive or multiplicative. We present a method for image registration using a difference operation in the frequency domain. Shift values are then computed by dividing by the object Fourier transform and inverse transforming. The method described is valid for both additive and multiplicative noise and determines shifts with sub pixel accuracy. Additionally, minimal prior knowledge of the corrupting pattern is required. We compare our method with previous registration methods for varying amounts of noise. Results are presented for both simulated images and images recorded from a thermal camera with significant fixed-pattern noise.

1200 nm pumped Tm3+:Lu2O3 ceramic lasers

Isinsu Baylam, Sarper Ozharar, and Alphan Sennaroglu

Doc ID: 307276 Received 15 Sep 2017; Accepted 31 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: We report on an experimental demonstration of a 1200-nm pumped Tm3+:Lu2O3 ceramic laser. By using a gain-switched,tunable Cr4+:forsterite laser, the excitation spectrum was measured, with optimum pumping bands centered near 1198,1204, and 1211 nm. The highest slope efficiency of 21.5% was obtained at the pump wavelength of 1204 nm.Comparative energy efficiency measurements performed near 1200-nm and 800-nm pumping further showed thatnearly 40% improvement was obtained in slope efficiency measured with respect to the incident pump energy for 1200-nm pumping. A transition was further observed from single-wavelength operation at 2066 nm to dual-wavelengthoperation near 2066 and 1967 nm for absorbed pump energies above 50 μJ. In this regime, two consecutive outputpulses were observed in the time domain. The shortest temporal duration of the first pulse was 1.1 μs at the incidentpulse energy of 105 μJ. The duration and build-up time of the second pulse remained around 5.9 μs and 18.5 μs. Webelieve that the improved energy efficiency demonstrated for the 1.5% Tm3+:Lu2O3 ceramic with 1200-nm pumping canbe used as an alternative scheme for the excitation of Tm3+:Lu2O3 ceramic lasers.

Extreme ultraviolet mask roughness effects in highnumerical aperture lithography

Patrick Naulleau, Yow-Gwo Wang, and tom pistor

Doc ID: 313130 Received 09 Nov 2017; Accepted 31 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: Given the reflective nature of extreme ultraviolet (EUV) lithography and its extremely short operationalwavelength, roughness of the optical surfaces is of significant concern. In particular, roughness in the maskmultilayer leads to image plane speckle and ultimately patterned line-edge or line-width variability in the imagingprocess. Here we consider the implications of this effect for future high numerical aperture (NA) systems which areassumed to require anamorphic magnification projection optics. The results show significant anisotropic behaviorat high NA as well as a substantial increase in relative patterned line variability in the shadowed direction whencomparing 0.55 NA to 0.33 NA, despite the assumption of an anamorphic magnification system. The shadoweddirectionpatterned line variability is 2x larger than for un-shadowed lines and the majority of the increase invariability occurs in the low frequency regime.

Microbubble-Based Fiber-optic Fabry-Perot PressureSensor for High Temperature Application

Zhe Li, pinggang jia, guocheng fang, Hao Liang, Ting Liang, Wenyi Liu, and Jijun Xiong

Doc ID: 314522 Received 05 Dec 2017; Accepted 30 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: Using the arc discharge technology, we fabricated a fiber-optic Fabry–Perot (FP) pressure sensor with very lowtemperature coefficient based on a microbubble which can be applied in high-temperature environment. The thinwallmicrobubble can be fabricated by heating the gas-pressurized hollow silica tube (HST) using a commercialfusion splicer. Then the well-cut single mode fiber (SMF) was inserted into the microbubble and fused with ittogether. Thus the Fabry-Perot cavity can be formed between the end of the SMF and the inner surface of themicrobubble. The diameter of the microbubble can be up to 360μm with the thickness of the wall beingapproximately 0.5μm. Experimental results show that such a sensor has a linear sensitivity of approximately−6.382nm/MPa, −5.912nm/MPa at 20℃, 600℃ within the pressure range of 1 MPa. Due to the thermal expansioncoefficient of the SMF is slightly larger than that of silica, we can fuse the SMF and the HST with different length,thus the sensor has a very low temperature coefficient approximately 0.17pm/℃.

Design and analysis of worm gear turntable off-axis assembly method in three-grating monochromator

JIANJUN CHEN, Cui Jicheng, Xuefeng Yao, jianan liu, and ci sun

Doc ID: 308375 Received 09 Oct 2017; Accepted 30 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: To solve the problem where the actual grating aperture decreases with increasing scanning angle during scanning of a three-grating monochromator, we propose an off-axis assembly method for the worm gear turntable that makes it possible to suppress this aperture reduction. We simulated and compared the traditional assembly method with the off-axis assembly method in the three-grating monochromator. Results show that the actual grating aperture can be improved by the off-axis assembly method, and for any one of the three gratings, when the monochromator outputs the longest wavelength in the corresponding wavelength band, the actual grating aperture increases by 45.93%. Over the entire monochromator output band, the actual grating aperture increased by an average of 32.56% and can thus improve the monochromator’s output energy. Improvement of the actual grating aperture can also reduce the stray light intensity in the monochromator and improve its output signal-to-noise ratio.

all-metal frequency-selective absorber/emitter forlaser stealth and infrared stealth

Lei Zhao, Han Liu, Zhi-Hong He, and Shi-Kui Dong

Doc ID: 314135 Received 23 Nov 2017; Accepted 30 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: In this paper, an all-metal nanostructure is designed with large frequency ratio (~6) and large bandwidth ratio(~32), which consisting of period slit-box cavities and nanodisk clusters. It’s a nearly perfect absorber at 1.064 μmto achieve laser stealth, a frequency-selective emitter with low emissivity in wavelength ranges 3-5 and 8-14 μm toachieve infrared stealth, also an emitter with nearly unity emissivity at 2.709 μm and 6.107 μm to compensate thedecrease of radiation heat transfer owing to the low emissivity. The absorption/emission peaks are all theLorentzian shape and the bandwidths, defined as the full width at half maximum, are 35, 408, and 1124 nm at 1.064,2.709, and 6.107 μm, respectively. The electric and magnetic field distribution shows that the slit behaves like acapacitor and the box behaves like an inductance, and the nanodisk clusters can excite electric dipole (ED)resonance. Considering the solar’s irradiation, the nanostructure maintains MWIR signal reduction rates greaterthan 80% from 450 to 1000 K, and LWIR signal reduction rates greater than 90% from room temperature to 1000K. The laser and infrared stealth performance of our nanostructure at 473 K are also studied with differentincident angles and polarization angles.

Low-order aberration correction of TMT tertiarymirror prototype based on warping harness

Han Linchu, Cheng-Zhi Liu, Cun-Bo Fan, Li Zhenwei, zhang jingxu, and Yin Xiaolin

Doc ID: 314943 Received 04 Dec 2017; Accepted 29 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: Warping harness is proposed to simply and efficiently correct low-order aberrations that occur duringmanufacturing and operation of a telescope. For the Thirty Meter Telescope (TMT) tertiary mirror, the issue to besolved by the warping harness is particularly challenging due to its complicated load conditions and limitedmounting space. In this study, first, a new type of whiffletree-based warping harness configuration applied to a ¼-prototype TMT tertiary mirror is presented and optimized using finite element analysis (FEA) to improve theoutput precision of the moment actuator. Next, based on the new configuration, a simulation method for acorrection process is proposed. The results show that the root mean square value of the mirror-surface errorconverged from 64.9 to 25.4 nm after correction, which satisfied the requirement document of TMT. Finally,combined with the analysis and calculation results, the moment actuator testing system with high-precisiondisplacement–force–strain is established to assess the system errors. The tests of the moment actuatordisplacement, stress, strain-output precision, linearity, and repeatability are completed, and all errors were foundto be within a controllable range. The results show the validity and feasibility of the designed warping harnesswhich can prove its applicability in more complicated conditions, and to a certain degree broaden the applicationscope of warping harness.

Reducing defocus aberration of compound and humanhybrid eye using liquid lens

yang cheng, jie CAO, LINGTONG MENG, ZIHAN WANG, kaiyu zhang, Yan Ning, and Qun Hao

Doc ID: 306764 Received 08 Sep 2017; Accepted 29 Jan 2018; Posted 29 Jan 2018  View: PDF

Abstract: We proposed a self-adaption focal length adjustment method of compound and human hybrid eye with nonuniformmicrolens array model (NUMLA) to reduce defocus aberration by using the liquid lens. The models arededuced and verified through simulations. The method can self-adaptively adjust the focal length according toobject distance and image distance. The results show that (1) The RMS spot radii of the traditional uniformmicrolens array at different rings are 21μm, 187μm, 304μm, 526μm, and 803μm. However, that of the NUMLA are21μm, 47μm, 98μm, 178μm, and 287μm, which indicates that the NUMLA can reduce the defocus aberration. (2)When the object distance and the image distance vary, the defocus aberration can be significantly reduced throughthe adjustment of the focal length, which validates the effectiveness of the proposed method. (3) The volumes of theliquid lens in the cavity at the peripheral rings are larger than that at the central rings. The results are beneficialfor providing a simple solution to reduce the defocus aberration of the compound and human hybrid eye.

Comparison of image reconstruction techniques for optical projection tomography

Anna Trull, Jelle van der Horst, Lucas Van Vliet, and Jeroen Kalkman

Doc ID: 309822 Received 14 Nov 2017; Accepted 29 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: We present a comparison of image reconstruction techniques for optical projection tomography. We compare conventional filtered back projection, sinogram filtering using the frequency-distance relationship (FDR), image deconvolution, and 2D point spread function (PSF) based iterative reconstruction. The latter three methods aim to remove the spatial blurring in the reconstructed image originating from the limited depth of field caused by the PSF of the imaging system. The methods are compared based on simulated data, experimental optical projection tomography data of single fluorescent beads, and high-resolution optical projection tomography imaging of an entire zebrafish larva. We demonstrate that the FDR method performs poorly on data acquired with high numerical aperture optical imaging systems. We show that the deconvolution technique performs best performance on highly sparse data with low signal-to-noise ratio. The PSF-based reconstruction method is superior for non-sparse objects and data of high signal-to-noise ratio.

Evaluation of a flow cytometry method to determine size and real refractive index distributions in natural marine particle populations

Jacopo Agagliate, Rüdiger Röttgers, Michael Twardowski, and David McKee

Doc ID: 313450 Received 14 Nov 2017; Accepted 29 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: A flow cytometric (FC) method was developed to retrieve particle size distributions (PSDs) and real refractiveindex (nr) information in natural waters. Geometry and signal response of the sensors within the flow cytometer(CytoSense, CytoBuoy b.v., Netherlands) were characterized to form a scattering inversion model based on Mietheory. The procedure produced a mesh of diameter and nr isolines where each particle is assigned the diameterand nr values of the closest node, producing PSDs and particle real refractive index distributions (PRIDs). Themethod was validated using polystyrene bead standards of known diameter and polydisperse suspensions of oilwith known nr, and subsequently applied to natural samples collected across a broad range of UK shelf seas. FCPSDs were compared with independent PSDs produced from data of two LISST-100X instruments (type B and typeC). PSD slopes and features were found to be consistent between the FC and the two LISST-100X instruments, butLISST concentrations were found in disagreement with FC concentrations and with each other. FC nr values werefound to agree with expected refractive index values of typical marine particle components across all samplesconsidered. The determination of particle size and refractive index distributions enabled by the FC method haspotential to facilitate identification of the contribution of individual subpopulations to the bulk inherent opticalproperties (IOPs) and biogeochemical properties of the particle population.

Forward modelling of inherent optical properties fromflow cytometry estimates of particle size andrefractive index

Jacopo Agagliate, Ina Lefering, and David McKee

Doc ID: 313456 Received 16 Nov 2017; Accepted 29 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: A Mie-based forward modelling procedure was developed to reconstruct bulk inherent optical properties (IOPs)from particle size distributions (PSDs) and real refractive index distributions (PRIDs) obtained using a previouslydeveloped flow cytometric (FC) method [1]. Given the available PSDs, extrapolations for the particle fractionoutside the detection limits of the method and a complex refractive index input (with real part nr directly estimatedand imaginary part ni adapted from literature separately for organic and inorganic components), the modelproduces volume scattering functions which are integrated to produce scattering and backscattering coefficients,and absorption efficiencies which are used to calculate absorption coefficients. The procedure was applied to PSDsand PRIDs derived from natural samples retrieved in UK coastal waters and analysed using a CytoSense flowcytometer (CytoBuoy b.v., Netherlands). Optical closure analysis was carried out between reconstructed IOPs andin situ IOPs measured using an ac-9 spectrophotometer and a BB9 backscattering meter (WET Labs Inc., OR) in thesame waters. The procedure is shown to achieve broad agreement with particulate scattering (bp) andbackscattering (bbp) (RMS%E: 35.3% and 44.5% respectively) and to a lesser degree with backscattering ratio (􀢈 􀷩􀢈􀢖)(RMS%E: 77%). The procedure however generally overestimated particulate absorption (ap) (RMS%E: 202.3%).This degree of closure was dependent on applying recently developed scattering error corrections to bothabsorption and attenuation in situ measurements. Not only do these results indirectly validate the FC method as auseful tool for PSD and PRID determination in natural particle populations, they also suggest that Mie theory maybe a sufficient model for bulk IOP determination, with previously reported difficulties potentially being caused byinadequately corrected IOP measurements. Finally, in a feature unique to the FC method, the concurrent size andrefractive index retrieval enabled assessment of the relative contributions that organic vs. inorganic, fluorescentvs. non-fluorescent fractions of the particle populations had on the IOPs, and identified which size classes had thelargest influence on each of these properties.

Coherent mid-infrared supercontinuum generationusing rib waveguide pumped with 200 fs laser pulsesat 2.8 μm

Than Singh Saini, Hoa Nguyen, Kenshiro Nagasaka, Luo Xing, Hoang Tuan Tong, Takenobu Suzuki, and Yasutake Ohishi

Doc ID: 319562 Received 11 Jan 2018; Accepted 29 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: A rib waveguide structures in As2Se3 chalcogenide glass has been designed and numerically analyzed for on-chipcoherent supercontinuum generation in the mid-infrared region. The waveguide structure possesses all-normaldispersion profile with dispersion value of -13.22 ps/nm.km at the pump wavelength. Coherent mid-infraredsupercontinuum spectrum spanning 1.2 to 7.2 μm has been obtained using a 2.5 mm long rib waveguide when itwas pumped with 200 fs laser pulses of a peak power of 2.5 kW and a repetition rate of 1 kHz at 2.8 μm. Such highlynonlinear sub-wavelength size rib waveguide structures are highly applicable for the power efficient on-chip midinfraredcoherent supercontinuum sources. Coherent mid-infrared supercontinuum sources are very important infrequency metrology, nonlinear microscopy, non-destructive testing, molecular spectroscopy and opticalcoherence tomography.

Simultaneous directional curvature and temperaturesensor based on a tilted few-mode fiber Bragg grating

Yunhe Zhao, Changle Wang, Guolu Yin, Biqiang Jiang, Kaiming Zhou, Chengbo Mou, Yunqi Liu, Lin Zhang, and Tingyun Wang

Doc ID: 313066 Received 09 Nov 2017; Accepted 28 Jan 2018; Posted 29 Jan 2018  View: PDF

Abstract: We demonstrate a directional curvature sensor based on tilted few-mode fiber Bragg gratings (FM-FBG) inscribedby UV-laser. The eigenmodes of LP01 and LP11 mode groups are simulated along with the fiber bending. Thedirectional curvature sensor is based on the LP11 mode resonance in the tilted FM-FBG. For curvature from 4.883 to7.625 m-1, the curvature sensitivities at direction of 0° and 90° are measured to be -2.67 and 0.128 dB/m-1,respectively. The temperature variation barely affects the resonance depth of LP11 mode. The proposed curvaturesensor clearly demonstrates the potential to simultaneous directional curvature and temperature measurementwith the resolutions of 􀫢. 􀫚􀫞 × 􀫚􀫙􀬿􀫝 m-1 and 0.952 °C, respectively.

Polymer Optical Fiber Based Sensor System forSimultaneous Measurement of Angle andTemperature

Arnaldo Leal Junior, Anselmo Frizera-Neto, Carlos Marques, and Maria Pontes

Doc ID: 318195 Received 20 Dec 2017; Accepted 28 Jan 2018; Posted 29 Jan 2018  View: PDF

Abstract: This paper presents a polymer optical fiber (POF) based sensor system for simultaneous measurement of angleand temperature. The main contribution is obtaining a sensor with higher temperature sensitivity and lowerhysteresis on the angle measurements. The annealing was made on the fibers under the conditions of low relativehumidity and under water, and a third set of samples without any heat treatment was applied for comparison withthe annealed ones. Results of temperature and angle characterization show that the fibers annealed under waterpresented higher temperature sensitivity and lower errors when compared with the fibers annealed with lowhumidity or the fibers without annealing. Furthermore, the fibers annealed under water also presented lowerhysteresis on the angle characterization. For these reasons, such fibers were employed for the temperature andangle measurements, which results on a sensor system capable of simultaneously measuring the angle andtemperature with root mean squared error (RMSE) of 0.82°C for temperature and 2.20° for angle, which is furtherreduced to 1.20° after the application of a dynamic compensation technique for POF curvature sensors.

Analysis on the characteristic of the optical axisperturbation in a total reflection prisms ring resonator

Dong Li, Chao Bi, Yajun Jiang, and Jianlin Zhao

Doc ID: 315446 Received 11 Dec 2017; Accepted 28 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: The deduction of the augmented 5×5 matrix describing all the possible angular and decentration misalignmentperturbation sources on a spherical prism plane during the refraction is presented in detail for the first time.Combining the augmented matrices and the condition of eigenmode self-consistency, the optical-axis perturbationproperties (descripted with the optical-axis perturbation sensitivity factor SD1, ST1, SD2 and ST2) in a totalreflection prism ring resonator are also analyzed. The singular points of the optical-axis perturbation sensitivityfactor are found at L/R=0.417 for the cases that the misalignments may originate from distinguished type of prismsP1 and P4 in the resonator, respectively. It is shown that the small errors of the prism can cause large optical-axisdisturbance in the position of the perturbed singular point and its nearby area, and the disturbance for the casethat the misalignments originate from prism P1 is more violently than that of prism P4. With some upgrades to findand avoid the singularity of the optical-axis in the TRPRR structure successfully, we expect this work will havegreat potential for designing and optimizing the structure of super high precision ring laser gyroscopes.

A lensless LED matrix ptychographic microscope:problems and solutions

Peng Li and Andrew Maiden

Doc ID: 315554 Received 13 Dec 2017; Accepted 25 Jan 2018; Posted 26 Jan 2018  View: PDF

Abstract: In this paper, a lensless microscope based on ptychography is presented. It disposes of the mechanicmovement necessary for conventional ptychography, instead using an LED matrix to obtain a diverse setof diffraction data. This data is subject to multiple experimental factors that deviate from the standardversion of ptychography: namely imprecise knowledge of the LED positions, partial temporal and spatialcoherence, and varying brightness and illumination distribution between individual LEDs. Despite thesedifficulties, we show here that the diversity in the ptychographic data allows an iterative phase retrievalalgorithm to recover excellent, high resolution images of a resolution test target and a biological sample.

Improvement of the fringe analysis algorithm forwavelength scanning interferometry based on filterparameter optimization

Tao Zhang, Feng Gao, Hussam Muhamedsalih, Shan Lou, Haydn Martin, and Xiangqian Jiang

Doc ID: 313281 Received 14 Nov 2017; Accepted 23 Jan 2018; Posted 23 Jan 2018  View: PDF

Abstract: Phase slope method which estimates height through fringe pattern frequency and the algorithm which estimatesheight through fringe phase are the fringe analysis algorithms widely used in interferometry. Generally they bothextract the phase information by filtering the signal in frequency domain after Fourier transform. Among thenumerous literature about these algorithms, it is found that the design of the filter, which plays an important role,has never been discussed in detail. This paper focuses on the filter design in these algorithms for wavelengthscanning interferometry (WSI), trying to optimize the parameters in order to acquire the optimal results. Thespectral characteristics of the interference signal are analyzed firstly. The effective signal is found to be narrowband(near single frequency) and the central frequency is calculated theoretically. Therefore, the position of thefilter pass-band is determined. The width of the filter window is optimized with the simulation to balance theelimination of the noise and the ringing of the filter. Experimental validation of the approach is provided and theresults agree with the simulation very well. The experiment shows the accuracy can be improved by optimizing thefilter design, especially when the signal quality, i.e. the signal noise ratio (SNR) is low. The proposed method alsoshows the potential of improving the immunity to the environmental noise by adapting to the signal to acquire theoptimal results through designing an adaptive filter once the signal SNR can be estimated accurately.

First Decadal Lunar Results from the Moon and EarthRadiation Budget Experiment (MERBE)

Grant Matthews

Doc ID: 301994 Received 10 Jul 2017; Accepted 05 Jan 2018; Posted 08 Jan 2018  View: PDF

Abstract: A need to gain more confidence in computer model predictions of coming climate change has resulted ingreater analysis of the quality of orbital Earth Radiation Budget (ERB) measurements, being used todayto constrain, validate and hence improve such simulations. These studies conclude from time series analysisthat for around a quarter of a century, no existing satellite ERB climate data record is of a sufficientstandard to partition changes to the Earth from those of un-tracked and changing artificial instrumentationeffects. This led to the creation of the Moon and Earth Radiation Budget Experiment (MERBE),which instead takes existing decades old climate data to a higher calibration standard using thousands ofscans of Earth’s Moon. The Terra and Aqua satellite ERB climate records have been completely regeneratedusing signal processing improvements, combined with a substantial increase in precision from morecomprehensive in-flight spectral characterization techniques. This study now builds on previous OSAwork by describing new Moon measurements derived using accurate analytical mapping of telescopespatial response. That then allows a factor of three reduction in measurement noise along with an orderof magnitude increase in the number of retrieved independent lunar results. Given decadal length devicelongevity and the use of solar and thermal lunar radiance models to normalize the improved ERB resultsto the SI traceable radiance scale of the ‘MERBE Watt’, the same established environmental time seriesanalysis techniques are applied to MERBE data. They evaluate it to perhaps be of sufficient quality toimmediately begin narrowing the largest of climate prediction uncertainties. It also shows that if suchTerra/Aqua ERB devices can operate into the 2020’s it could become possible to halve these same uncertainties,decades sooner than would be possible with existing or even planned new observing systems.

IMPROVED IDENTIFICATION OF THE SOLUTION SPACEOF AEROSOL MICROPHYSICAL PROPERTIES DERIVEDFROM THE INVERSION OF PROFILES OF LIDAR OPTICALDATA, PART 3: CASE STUDIES

Alexei Kolgotin, Detlef Mueller, Eduard Chemyakin, Anton Romanov, and Valentin Alehnovich

Doc ID: 312384 Received 09 Nov 2017; Accepted 31 Dec 2017; Posted 05 Jan 2018  View: PDF

Abstract: We conclude our series of publications on the development of thegradient correlation method (GCM) which can be used for an improvedstabilization of the solution space of particle microphysical parametersderived from measurements with multiwavelength Raman and High-Spectral-Resolution Lidar (3 backscatter + 2 extinction coefficients).We show results of three cases studies. The data were taken with aground-based multiwavelength Raman lidar during the Saharan MineralDust Experiment (SAMUM) in the Cape Verde Islands (North Atlantic).These cases describe mixtures of dust with smoke. For our dataanalysis we separated the contribution of smoke to the total signal andonly used these optical profiles for the test of GCM. The results show asignificant stabilization of the solution space of the particle microphysicalparameter retrieval on the particle radius domain from 0.03 μm to10 μm, the real part of the complex refractive index domain from 1.3 to1.8 and the imaginary part from 0 to 0.1. This new method will be includedin TiARA (Tikhonov Advanced Regularization Algorithm)which is a fully automated, unsupervised algorithm that is used for theanalysis of the world-wide first airborne 3 backscatter + 2 extinctionhigh-spectral-resolution lidar developed by NASA Langley ResearchCenter.

360 deg large-scale multi-projection light-field 3D display system

Lixia Ni, Zhenxing Li, Haifeng Li, and Xu Liu

Doc ID: 308843 Received 09 Oct 2017; Accepted 31 Dec 2017; Posted 01 Feb 2018  View: PDF

Abstract: This paper proposed a 360 deg large-scale multi-projection light-field 3D display system, which can reconstruct light-field of models in real space. The reconstructed contents can be observed by multiple viewers from different angles and positions simultaneously. In this system, 360 projectors project images onto a cylindrical light-field diffusion screen whose height is 1.8m and diameter is 3m. When moving around the system, viewers can see 3D scenes with smooth motion parallax and the frame rate can reach 30 fps and above. To achieve large scale display, we design a wide-field lens with cylindrical lenses to enlarge projection image. To promote efficiency of data transmission and render 3D contents in real time, we apply computers equipped with multiple graphic cards and display data are divided by FPGA. Finally, a 360 deg light-field auto-calibration method based on CCD and multi-view sampling is proposed, whose calibration effect is strongly confirmed by experiment results.

The giant Goos–Hӓnchen shift in two different enantiomers chiral molecules via quantum coherence

Rajab Nasehi and Mohammad Mahmoudi

Doc ID: 302077 Received 18 Jul 2017; Accepted 25 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: The GH shifts in the reflected and transmitted probe light through a cavity mixture of left-handed and right-handedchiral molecules into two enantiomer states are investigated. Due to broken mirror symmetric of the left- andright- handed chiral molecules in presence of cyclic population transfer, such the quantum systems can beselectively excited because of the coexistence of one- and two-photon transitions. With the help of coupling Rabifrequencyand damping effects due to scattering processes, the generated GH shifts accompany by simultaneouslynegative and positive lateral shift in reflected and transmitted probe lights are realized to be greatly enhanced. It isfound that the large negative and positive GH shifts are available in the presence of multi-photon resonance andoff-resonance conditions for two different enantiomers chiral molecules. Moreover, the switching betweensuperluminal and subluminal light propagation are extremely dependence to choose the left- and right-handedchiral molecules. Furthermore, the effects of pulse shape and mode of Laguerre-Gaussian probe light on the GHshifts leads to switch between negative and positive shift are also studied. The negative and positive GH shifts inreflected and transmitted probe beam for an incident Gaussian and different mode of Laguerre-Gaussian shapedbeam are also discussed with various widths by use of two different enantiomer chiral molecules.

Passively Q-switched Yb:YAG laser base on MoSe2 saturable absorber

Jiasai Ma, wenguagn jiang, chuanhe shen, and shanfu yuan

Doc ID: 313803 Received 17 Nov 2017; Accepted 19 Dec 2017; Posted 19 Dec 2017  View: PDF

Abstract: MoSe2 nanosheets based saturable absorber (SA) was fabricated successfully by liquid-phase exfoliation (LPE) method. A passively Q-switched crystalline Yb:YAG laser was realized with the MoSe2-SA inserted inside the cavity. The shortest pulses at a wavelength of 1049 nm with a duration of 250 ns, maximum repetition rate of 181 kHz and an average output power of 158 mW were emitted, corresponding to a maximum pulse energy of 0.87 μJ. To the best of our knowledge, this is the first experimental demonstration of nonlinear absorption property of MoSe2 nanoplatlets in a crystalline Yb-doped solid-state laser, which also proves the great potential of MoSe2-SA as optical modulator in 1 μm spectral region.

Single-Pulse Ablation of Multi-Depth Structures via Spatially Filtered Binary Intensity Masks

Daniel Heath, James Grant-Jacob, Robert Eason, and Benjamin Mills

Doc ID: 307609 Received 21 Sep 2017; Accepted 31 Oct 2017; Posted 12 Jan 2018  View: PDF

Abstract: Digital Micromirror Devices (DMDs) show great promise for use as intensity spatial light modulators. When used in conjunction with pulsed lasers of a timescale below the DMD pixel switching time, DMDs are generally only used as binary intensity masks (i.e. ‘on’ or ‘off’ intensity for each mask pixel). In this work, we show that by exploiting the numerical aperture of an optical system during the design of binary masks, near-continuous intensity control can be accessed, whilst still maintaining high-precision laser machining resolution. Complex features with ablation depths up to ~60 nm, corresponding to grayscale values in bitmap images, are produced in single pulses via ablation with 150 fs laser pulses on nickel substrates, with lateral resolutions of ~2.5 µm.

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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