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Accepted papers to appear in an upcoming issue

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Retrieval of phytoplankton cell size from chlorophyll aspecific absorption and scattering spectra ofphytoplankton

Wen Zhou, Guifen wang, li cai, zhantang xu, Wenxi Cao, and fang shen

Doc ID: 298204 Received 16 Jun 2017; Accepted 20 Sep 2017; Posted 20 Sep 2017  View: PDF

Abstract: Phytoplankton cell size is an important property that affects diverse ecological and biogeochemical processes, and analysis of the absorption andscattering spectra of phytoplankton can provide important information about phytoplankton size. In this study an inversion method for extractingquantitative phytoplankton cell size data from these spectra was developed. This inversion method requires two inputs: chlorophyll a specificabsorption and scattering spectra of phytoplankton. The average Equivalent-volume Spherical Diameter (ESDv) was calculated as the single sizeapproximation for the log-normal particle size distribution (PSD) of the algal suspension. The performance of this method for retrieving cell size wasassessed using the datasets from cultures of 12 phytoplankton species. The estimations of 􀜽(λ) and b(λ) for the phytoplankton population usingaverage ESDv have mean error values of 5.8~6.9%, and 7.0~10.6%, respectively, when compared to the a(λ) and b(λ) for the phytoplanktonpopulations using the log-normal PSD. The estimated values of CiESDv were in good agreement with the measurements, with R2 = 0.88 and relativeroot mean square error (NRMSE) = 25.3%., and relatively good performances were also found for the retrieval of ESDv with R2 = 0.78 and NRMSE= .9%.

Methods of polarimetric calibration and reconstruction for a fieldable channeled dispersive imaging spectropolarimeter

Bin Yang, Jq zhang, cx yan, and Xping Ju

Doc ID: 301649 Received 05 Jul 2017; Accepted 19 Sep 2017; Posted 20 Sep 2017  View: PDF

Abstract: Polarimetric calibration and reconstruction methods for a fieldable channeled dispersive imaging spectropolarimeter (CDISP) are presented. A theoretical model for the polarimetric calibration is derived firstly. In the polarimetric calibration for the CDISP, the alignment errors of the polarimetric spectral intensity modulation (PSIM) module, and the polarization effects of the optical system and phase factors of the high-order retarders at different viewing angles, are considered and determined independently. Based on the results of the polarimetric calibration, the Stokes vector of the target is reconstructed through the derived reconstruction model. By using the presented polarimetric calibration and reconstruction methods, the measurement accuracy at each viewing angle of the fieldable CDISP can be improved effectively. Results of simulation experiments with a fieldable CDISP designed for airborne remote sensing are summarized and analyzed to demonstrate the effectiveness of the presented methods.

Effect of tissue frozen on quantitative optical properties using optical coherence tomography

Jianghua Li, J. Chen J. Chen, X.J. Mu X.J. Mu, Q.L Shao Q.L Shao, and L.J. Yan L.J. Yan

Doc ID: 301873 Received 21 Jul 2017; Accepted 19 Sep 2017; Posted 20 Sep 2017  View: PDF

Abstract: The purpose is to demonstrate the optical charactering concerning Nasopharyngeal tissue of pig by fresh sections and frozen correlating sections with optical coherence tomography (OCT). After OCT imaging is performed on fresh specimen, samples are then stored at low temperature refrigerators (-800C) for one year for the second OCT measurement. The OCT structure of the epithelium, lamina propria and the basement membrane are still resolvable; The median scattering coefficients and anisotropy factors fitting from OCT images based on the multiple scattering effects for epithelium are 27.6 mm−1 (IQR .6 to 29.3 mm−1) versus 22.5 mm−1 (IQR 20.5 to 24.4 mm−1), 0.86 (IQR 0.81 to 0.9) versus 0.88 (IQR 0.87 to 0.9) for fresh and frozen tissue, respectively; and 10.2 mm−1 (IQR 8.1 to 13.6 mm−1) versus 9.6 mm−1 (IQR 8.1 to 13.8 mm−1), 0.96 (IQR 0.93 to 0.98) versus 0.92 (IQR 0.9 to 0.98) for lamina propria, respectively. The results show that the frozen storage method can be used for OCT research.

Oblique-incidence reflectivity difference application for morphology detection

Zhan Honglei, KUN ZHAO, HB Lu, Kui-Juan Jin, Guo-Zhen Yang, and Xiaohong Chen

Doc ID: 304637 Received 10 Aug 2017; Accepted 19 Sep 2017; Posted 20 Sep 2017  View: PDF

Abstract: In analogy with scanning electron microscopy (SEM) we use an oblique-incidence reflectivity difference (OIRD) approach for morphology detection. By scanning the active carbon clusters with one-dimensional way and the reservoir rocks with two-dimension, the morphology of samples’ surface can be revealed in OIRD signal images. High OIRD signals of active carbon samples refer to the centralized distribution areas of carbon, and the fluctuations are caused by the uneven distribution carbon pellets. OIRD intensity is proportional to the thickness of materials. In terms of rocks, the troughs areas with smaller values refer to the low lying fields. The areas with relatively large OIRD intensities correspond to the protuberances areas of rocks. Consequently, OIRD is a sensitive yet rapid measure of surface detection in material and petro-geology science.

Automatic and Rapid Whole-body 3D Shape Measurement Based on Multi-Node 3D Sensing Speckle Projection

Jiping Guo, Xiang Peng, Ameng Li, Xiaoli Liu, and Jiping Yu

Doc ID: 304142 Received 07 Aug 2017; Accepted 19 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: Automatic and rapid whole-body 3D shape measurement has attracted extensive attentions in recent years, and been widely used in many fields. Rapid 3D reconstruction, automatic 3D registration and dedicated system layout are critical factors to enable an excellent 3D measurement system. In this paper, we present an automatic and rapid whole body 3D measurement system that is based on multi-node 3D sensors using speckle projection. A rapid algorithm for searching homologous point pairs is suggested, which takes advantage of the optimized projective rectification and simplified sub-pixel matching techniques, leading to an improved time efficiency of 3D reconstruction. Meanwhile, a low cost automatic system with a flexible setup and an improved calibration strategy are proposed, where system parameters of each node sensor can be simultaneously estimated with the assistant of a cubic and a planar target. Furthermore, an automatic range data registration strategy by employing two aided-cameras is investigated. Experiment results show that the presented approach can realize automatic whole body 3D shape measurement with high efficiency and accuracy.

Glucose Sensing In Oral Mucosa Simulating PhantomUsing Differential Absorption Based Frequency DomainLow-Coherence Interferometry

Pauline John, Nilesh Vasa, Sujatha Narayanan Unni, and Suresh Rao

Doc ID: 295501 Received 09 May 2017; Accepted 19 Sep 2017; Posted 20 Sep 2017  View: PDF

Abstract: Superluminescent diode based differential absorption frequency domain low-coherence interferometry (FD-DALCI)technique is proposed and demonstrated for sensing physiological concentrations of glucose (0-250 mg/dl) in oralmucosa simulating phantoms (intralipid of concentrations 0.25%-0.50%) with wavelengths at 1589 nm and 1310 nm.This novel technique allows simultaneous measurements of refractive index based spectral shift and estimation ofphysiological concentration of glucose in intralipid with scattering characteristics using differential absorptionapproach. The sensitivity of glucose concentration obtained by spectral shift measurement was ≈ 0.016 nm/(mg/dl),irrespective of the intralipid concentration. The resolution of glucose level was estimated to be ≈ 15 mg/dl in 0.25%intralipid and ≈ 19 mg/dl in 0.5% intralipid using FD-DALCI technique.

Non-contact Control of Two Photon Absorption

Ayan Ray, Waseem Raja, Md. Farroque Mir, and Alok Chakrabarti

Doc ID: 297762 Received 12 Jun 2017; Accepted 19 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: AbstractIn this experimental work we address the issue of control of two photon absorption in a Doppler broadened medium of 85Rb atoms under the ladder level coupling 5S1/25P3/25D3/2. Here suppression and enhancement of two photon absorption are executed by application of an auxiliary laser beam, which is not physically propagating in the same line of pump-probe combination. Instead the auxiliary beam, which is in resonance with 85Rb D2 transition, is at a finite distance from the line of propagation of pump-probe combination. The resonant auxiliary beam produces an atomic beam in the vapour cell, which when reaches the pump-probe path creates an asymmetry in the population at the ground state hyperfine components. This asymmetry is responsible for controlling the two photon absorption. We present here results obtained by us alongwith a qualitative explanation of the physical principle lying behind the control mechanism.

Laterally coupled distributed feedback type-I quantum well cascade diode lasers emitting near 3.22 µm

Tao Feng, Takashi Hosoda, Leon Shterengas, GELA KIPSHIDZE, Aaron Stein, Ming Lu, and Gregory Belenky

Doc ID: 300735 Received 23 Jun 2017; Accepted 19 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: The laterally coupled distributed feedback (LC-DFB) GaSb-based type-I quantum well cascade diode lasers using the 2nd and the 6th order gratings to stabilize the output spectrum near 3.22 µm were designed and fabricated. The laser heterostructure contained three cascades. The devices were manufactured using single dry etching step defining the ~5- µm-wide ridge with ~5-µm-wide gratings sections adjacent to the ridge sides. The grating coupling coefficients were estimated to be about 1 cm 1. The stability of the single frequency operation was ensured by alignment of the DFB mode to the relatively wide gain peak. The 2-mm-long 2nd order LC-DFB lasers generated above 10 mW of continuous wave (CW) output power at 20 °C in epi-side-up configuration and demonstrated power conversion efficiency above 2%. The 6th order LC-DFB lasers showed lower efficiency but still generated several milliwatts of CW output power. The devices demonstrated CW current tuning range of about 3.5 nm at the temperature of 20 °C.

Two-photon absorption measurements of deep UV transmissible materials at 213nm

Siddharth Patankar, Steven Yang, John Moody, George Swadling, Alvin Erlandson, Andy Bayramian, David Barker, Philip Datte, Robert Acree, Brian Pepmeier, Robert Madden, Michael Borden, and James Ross

Doc ID: 303127 Received 24 Jul 2017; Accepted 18 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: We report on two photon absorption measurements at 213nm of deep UV transmissible media including LiF, MgF2, CaF2, BaF2, Sapphire (Al2O3) and high purity grades of fused-silica (SiO2). A high stability 24ps Nd:YAG laser operating at the 5th harmonic (213nm) was used to generate a high intensity, long Rayleigh length Gaussian focus inside the samples. The measurements of the Fluoride crystals and Sapphire indicate two photon absorption coefficients between 0.004 and 0.82 cm/GW. We find that different grades of fused silica performed near identically for two photon absorption, however, there are differences in linear losses associated with purity. A low two photon absorption cross section is measured for MgF2 making it an ideal material for the propagation of high intensity deep UV lasers.

Wide-field fluorescence tomography with composited epi-illumination of multi-frequency sinusoidal patterns

Tongxin Li, Zhuanping Qin, Weiting Chen, Huijuan Zhao, Panpan Yan, Kuanxin Zhao, and Feng Gao

Doc ID: 304011 Received 03 Aug 2017; Accepted 18 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: We present a spatial-frequency-domain (SFD) fluorescence tomography (FT) for acquiring three-dimensional fluorophore distribution in turbid media. The approach uses a composited epi-illumination of multi-frequency sinusoidal patterns on a sample of semi-infinite geometry, and demodulates the measured data with a generalized phase-shifting scheme to calculate obtain the modulation transfer function (MTF) at each frequency. This method results in a significantly reduced number of the optical field measurements as compared to those with separate illumination of single-frequency sinusoidal patterns, and thereby achieves a fast data acquisition that is desired for a dynamic imaging application. Fluorescence yield images are recovered with the normalized-Born formulated inversion of the diffusion model, by simultaneously using the multi-frequency MTFs. Simulative and experimental reconstructions are performed in comparison with the single-frequency scheme, to validate the proposed algorithm. The results suggest that adoption of the multi-frequency strategy to the SFD-FT can substantially enhance the real-time performance of imaging, and greatly improve the spatial resolution and quantitative accuracy of reconstruction.

High Brightness Laser-driven White Emitter for Etendue-Limited Applications

Yi Yang, Songlin Zhuang, and beichao kai

Doc ID: 298212 Received 16 Jun 2017; Accepted 17 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: Laser-phosphor lighting has great potential because laser diode (LD) could keep high efficiency under high current. Remote phosphor configuration has been studied, but phosphor-covered laser diode has not been reported due to several difficulties. In the present work, we develop a novel laser-driven white emitter. Without remote phosphor configuration, the white emitter has a very simple structure, making it is easy for mass production and standardization. Under CW driving current of 3A, it emits 850 lm with correlated color temperature of 6990K. The wall-plug efficacy is 70 lm/W for maximum. The laser-driven white emitter is very suitable for Etendue-limited application due to its very small emitting size of 0.45x0.2mm².

A general error model for analysis of laser-induced incandescence signals

Timothy Sipkens, Paul Hadwin, Samuel Grauer, and Kyle Daun

Doc ID: 304677 Received 14 Aug 2017; Accepted 17 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: Time-resolved laser-induced incandescence (TiRe-LII) is a method for inferring key properties of aerosolized nanoparticles. Measurements of incandescence are combined with physical models of the process to infer nanoparticle properties. This paper presents a novel error model for TiRe-LII signals and illustrates how the model can be used to diagnose a detection system, quantify uncertainties in TiRe-LII, and characterize fluctuations in the measured process. Noise in a single TiRe-LII measurement shot obeys a Poisson-Gaussian noise model. Variation in the aerosol results in shot-to-shot fluctuations in the measured signals. This paper shows that, in the presence of these fluctuations, a quadratic relationship exists between the mean and variance of a set of signals. The quadratic coefficients correspond directly to sources of noise in the LII system and variation in the process. We show how this model can elucidate aspects of the measurement system and fundamental properties of the aerosol, by comparing the noise model to four sets of experimental data.

Photonic Crystal bandedge membrane Lasers on Silicon

Shih-Chia Liu, Deyin Zhao, Yonghao Liu, Hongiun yang, Yuze Sun, Zhenqiang Ma, Carl Reuterskiöld Hedlund, Mattias Hammar, and Weidong Zhou

Doc ID: 303773 Received 07 Aug 2017; Accepted 16 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: We report here the design and experimental demonstration of optically pumped photonic crystal bandedge membrane lasers on SOI and on bulk Si substrates, based on heterogeneously integrated InGaAsP MQW membrane layers transfer printed onto patterned photonic crystal cavities. Single mode lasing under room temperature operation was observed at 1,542 nm, with excellent SMSR greater than 31.5 dB, for the laser built on SOI substrate. For the laser built on bulk Si substrate, single mode lasing was also achieved at 1,452 nm with much lower thermal resistance, as compared to that of the laser built on SOI substrates. Such improved thermal characteristics is favorable for lasers operating potentially at higher temperatures and higher power.

Nanoantenna Arrays Combining Enhancement and Beam Control for Fluorescence Based Sensing Applications

Neciah Dorh, Andrei Sarua, Tahmmina Ajmal, Julius Okache, Carlos Rega, Georg Müller, and Martin Cryan

Doc ID: 296824 Received 05 Jun 2017; Accepted 15 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: This paper presents measured fluorescence enhancement results for ~250 x 250 element aluminium nanoantenna arrays fabricated using electron beam lithography. The arrays have been designed to use diffractive coupling to enhance and control the direction of fluorescent emission. Highly directional emission is obtained at the designed angles with beamwidths simulated to be in the range of 4-6°. Angle resolved spectroscopy measurements of dye-coated nanoantenna arrays were in good agreement with FDTD modelling. Critically, these results were obtained for near UV wavelengths (~360nm) which is relevant to a number of biosensing applications.

Towards a unified model for predicting color quality oflight sources

Haisong Xu, Fuzheng Zhang, and Heng Feng

Doc ID: 303000 Received 20 Jul 2017; Accepted 15 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: Considering that the existing color quality (CQ) metrics for light sources cannot correlate well with the subjectiveevaluation, in an immersive environment equipped with a multi-channel LED light source, a psychophysicalexperiment by categorical judgment method was carried out to assess the three perception-related CQ attributes oflight sources in terms of naturalness, colorfulness, and preference. The experiment collected the subjectiveresponses to these attributes of up to 41 metameric spectra at each of four test correlated color temperatures(CCTs) ranging from 2800 to 6500 K, which covers the usual white-light range for general lighting. The resultsindicate that preference exhibits relatively high correlation with naturalness and colorfulness, and naturalness isweakly related to colorfulness. Besides, 20 typical CQ metrics were adopted to examine their validity incharacterizing the subjective data, confirming their limited performance. Meanwhile, the underlying relationshipof these metrics and the subjective data was also analyzed by the multidimensional scaling, revealing that almostall metrics can correspond to one attribute of naturalness, colorfulness, and preference, and that the saturationlevel is identified as a critical factor affecting these attributes. Based on these results, a unified CQ model wasdeveloped with a multiple nonlinear regression equation combining the Illuminating Engineering Society of NorthAmerica color rendition method. The model accords satisfactorily with the subjective evaluation, while beingapplicable to a wide range of CCTs.

Ultraviolet polarizer with Ge subwavelength grating

Yuusuke Takashima, Masato Tanabe, Masanobu Haraguchi, and Yoshiki Naoi

Doc ID: 296069 Received 15 May 2017; Accepted 15 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: A polarizer with high extinction (ER) ratio was developed in the ultraviolet wavelength region using a germanium subwavelength grating (Ge-SWG). By utilizing an eigenmode with the Ge-SWG, a high ER was numerically predicted to exist without requiring a high structural aspect ratio. After using lithography to fabricate the proposed Ge-SWG, an experimental high ER value of 17.4 dB was reached at a wavelength of 360 nm in the developed Ge-SWG, which had a very low structural aspect ratio of 1.67.

Submicron sized non-spherical particles separation by laser beam

Jaromir Petrzala, MIROSLAV KOCIFAJ, Ladislav Komar, and Alexandre Simoneau

Doc ID: 300476 Received 20 Jun 2017; Accepted 14 Sep 2017; Posted 15 Sep 2017  View: PDF

Abstract: The radiation pressure exerted on a sub-micrometer sized particle is shown to be an important factor predetermining the impact coordinates of the particles after being illuminated by a laser beam. Unlike spherical particles, the non-spherical ones can be deflected perpendicularly of the beam direction if the momentum transfer from the laser beam to a particle is large enough. This kind of optical sorting is a useful technology that can be used to isolate spherules of a specific size from a system of randomly sized and shaped particle populations. The system of ideally spherical particles has wide range of applications in industry and also in development of targeted optical devices, so the methods for fast contact-less particle separation are expected to lead to a considerable progress in the field. The theoretical model we have developed is demonstrated in a set of numerical experiments on metallic and non-metallic particles.

Full Reference Quality Assessment of StereoscopicImages by Learning Binocular Visual Properties

Jian Ma, Ping An, Liquan Shen, and Kai Li

Doc ID: 302400 Received 14 Jul 2017; Accepted 14 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: Stereoscopic imaging technology has been growingly prevalent driven by both the entertainment industry andscientific applications in today’s world. But objective quality assessment of stereoscopic images is a challengingtask. In this paper, we propose a novel stereoscopic image quality assessment (SIQA) method by jointly consideringmonocular perception and binocular interaction. As the most significant contribution of this study, binocularperceptual properties of simple and complex cells are considered for FR SIQA. Specifically, the proposed schemefirst simulates the receptive fields of simple cells (one class of V1 neurons) using a push-pull CORF (combination ofreceptive fields) response, which is used to represent monocular cue. Further, the receptive fields of complex cells(the other class of V1 neurons) are simulated by using binocular energy response and binocular rivalry response,which are used to represent binocular cue. Subsequently, various quality-aware features are extracted from theresponse of area V1, by calculating the self-weighted histogram of local binary pattern (LBP) on four types offeature maps of similarity measurement, which will change in the presence of distortions. Finally, kernel ridgeregression (KRR) is used to simulate nonlinear relationship between the quality-aware features and objectivequality scores. The performance of our method is evaluated over popular stereoscopic image databases and shownto be competitive with the state-of-the-art FR SIQA algorithms.

Independence between intensity and phase noise ofsuperluminescent diodes in low frenquency domain

Pengwei Zhou, Hekuo Peng, Yongchao Chen, Hang Xu, Bo Jia, and Qian Xiao

Doc ID: 303977 Received 03 Aug 2017; Accepted 14 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: We theoretically and experimentally demonstrate a method for measuring the phase and intensity noise and theircorrelation in Superluminescent Laser Diodes. A Michelson Interferometer containing strongly unbalanced pathshas been developed to measure the noise. By the spectral analysis of the photocurrents in detectors, the intensitynoise is about twice the value of the phase noise in the Superluminescent Laser Diode. The more interesting resultwe obtained is the experimental evidence that the intensity noise and the phase noise are mutually independent.The correlation coefficient of the intensity noise and the phase noise fluctuates between -0.08 and 0, which showsscarcely any sign of amplitude-phase noise correlation. The results offer a basic premise for the analysis ofbroadband light sources.

Quick pre-correction of grating fringe for phase measuring profilometry

Qian Huang, Zeyong Wang, and Jinlong Li

Doc ID: 302627 Received 18 Jul 2017; Accepted 13 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: In this paper, for Phase Measuring Profilometry (PMP) system based on digital light projector, a novel method of grating fringe quick pre-correction is proposed. In the actual engineering conditions, it is impractical to strictly limit the geometry of the system. So grating fringes on the reference plane often appear distortions of keystone and period broadening, which are difficult to completely eliminate in the traditional calibration process. A pre-correction method based on analytic spatial transform is designed to solve these problems individually. The correction process occurs before the Digital Micromirror Device (DMD) image is generated, and theoretically, it can be compatible with most existing PMP correction and calibration methods. The correction is simple and completely implicit, and does not require a special calibration target. The correction is quick, only need to project and shoot a fringe image and a corner image, and can be completed within a few seconds. A simulation and several experiments were carried out to verify the effectiveness of this method.

Optimized design method for inner surface of conformal dome based on ray tracing approach

Fanyang Dang, Shouqian Chen, Wang Zhang, HUI WANG, and Fan Zhigang

Doc ID: 301645 Received 05 Jul 2017; Accepted 13 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: Traditional optical domes are spherical, which introduce constant aberrations with look angle. However, spherical domes are not optimum for reducing aerodynamic drag. Conformal domes deviate from spherical to reduce drag but they generate dynamic aberrations varying significantly with look angle in the field of regard (FOR). Thus, conformal domes require unique challenges for aberration correction. This paper presented a method to reduce the dynamic aberrations through designing the inner surface of conformal domes. This method follows the principle that the optical axis ray (OAR) of the imaging system maintains the same direction after refraction through the conformal dome for different look angles. Based on this principle, equations that the inner surface should satisfy are established and a numerical solution method is introduced. Eventually, Zernike polynomial coefficients of Z4, Z5 and Z8 which represent defocus, astigmatism and coma respectively are analyzed for quadratic domes with different inner surfaces. Compared with constant thickness quadratic domes, quadratic domes with the inner surfaces calculated by this method have smaller Zernike aberrations. In conclusion, this design method for the inner surface can effectively reduce dynamic aberrations.

Dual-grating dielectric accelerators driven by a pulse-front-tilted laser

Yelong Wei, Mark Ibison, Guoxing Xia, Jonathan Smith, and Carsten Welsch

Doc ID: 301819 Received 06 Jul 2017; Accepted 13 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: This paper investigates numerically dual-grating dielectric laser-driven accelerators driven by a pulse-front-tilted (PFT) laser, which extends the interaction length and boosts the electrons’ energy gain. The optical system necessary to generate PFT laser beams with an ultrashort pulse duration of 100 fs is also studied in detail. Through two-dimensional (2D) particle-in-cell simulations, we show that such a PFT laser effectively increases the energy gain by (91 ± 32) % compared to that of a normally-incident laser with a waist radius of 50 μm for a 100-period dual-grating structure.

Measurement of pile-up around spherical indentation by image-plane digital holography

Matias Viotti and Armando Albertazzi

Doc ID: 301823 Received 06 Jul 2017; Accepted 12 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: Instrumented indentation has been used to measure mechanical properties, residual stresses, hardness and viscoelastic properties among others due to its fast and nondestructive procedure. The accurate determination of the contact area between the indenter and the material is important for material property measurements and usually is masked by the pile-up or sink-in phenomenon. This paper presents the application of dual-wavelength image-plane digital holography in order to achieve a full-field determination of the topography around the indentation mark. The optical configuration was able to identify pile-up with magnitudes close to 25m. Measurement results were compared with the references performed by a commercial focus-variation device showing positive agreement between the obtained profiles. Additionally, most of the points presented differences between measurements lower than 3 micrometers.

Ultraviolet optical vortex generation using a pair of β-BaB₂O₄ crystals with inverted orientations

Yuta Sasaki, Koki Yamaguchi, Jun Shibakawa, Katsuhiko Miyamoto, and Takashige Omatsu

Doc ID: 303068 Received 21 Jul 2017; Accepted 12 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: Picosecond pulsed frequency-doubled optical vortices were generated using a pair of β-BaB₂O₄ crystals with their c-axes inverted. This arrangement produced high-quality ultraviolet vortex output with low spatial separation of the phase singularity at a conversion efficiency of ~40%. We also discuss the theoretical spatial form and beam propagation of the ultraviolet vortex output.

Angular dependent light scattering from cancer cells in different phases of cell cycle

Xiaogang Lin, Nan Wan, Lingdong Weng, and Yong Zhou

Doc ID: 296979 Received 01 Jun 2017; Accepted 12 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: Cancer cells in different phases of cell cycle result in significant differences in light scatteringproperties. In order to harvest cancer cells in some particular phases of cell cycle, we culturedcancer cells through the process of synchronization. Flow cytometric analysis was applied to checkthe results of cell synchronization and make preparation for light scattering measurements.Angular dependent light scattering measurements of cancer cells arrested in G1, S, G2 phase havebeen performed. Based on the calculation of integral for scattering intensity from 5° to 10° andfrom 110° to 150°, conclusions have been reached. Clearly, the size of the cancer cells in differentphases of cell cycle dominated the forward scatter. Accompanying the increasing of cell size withthe progression of cell cycle, the forward scattering intensity has also increased. Meanwhile, theDNA content of cancer cells in every phase of cell cycle is responsible for the light scattering atlarge scatter angles. The more the DNA content of cancer cells was, the greater the positive effectson high-scattering intensity. As expected, understanding the relationships between the lightscattering from cancer cells and cell cycle will aid in the development of cancer diagnoses. Also, itmay assist for the guidance of antineoplastic drug clinically.

Distance determination based on the delay time-intensity profile analysis in range-gated imaging

Vitaly Kabashnikov and Boris Kuntsevich

Doc ID: 297250 Received 01 Jun 2017; Accepted 12 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: A method for distance determination with the help of range-gated viewing systems is proposed for an arbitrary shape of the illumination pulse. The method is based on fixing maximum of the reflected pulse energy as a function of the delay time. At the equal pulse and gate durations, there is a strict maximum, which turns into a plateau when the pulse is shorter than the gate duration. The delay times corresponding to the strict maximum or the far boundary of the plateau are directly related to the distance to an object. These results are confirmed by the numerical study of the dependence of the detected energy on the delay time for the different pulse shapes. Experimental verification of the proposed method showed accuracy 1-2 m in measuring range of 15-120 m. The obtained results can be useful in the development of 3-D vision systems.

Heterodyne high spectral resolution lidar

Fernando Chouza, Benjamin Witschas, and Oliver Reitebuch

Doc ID: 300575 Received 20 Jun 2017; Accepted 12 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: In this work, a novel lidar technique to perform high spectral resolution measurements of the atmospheric backscatter is discussed and first results are presented. The proposed method, which relies on a heterodyne detection receiver, allows not only to separate the molecular and the aerosol component of the atmospheric backscatter, but also to investigate the spectral shape of the Rayleigh-Brillouin line. As in the case of the direct-detection high spectral resolution lidars, the separation of the different scattering processes would allow an independent system calibration and aerosol extinction measurements. The proposed retrieval technique was successfully tested on the DLR airborne Doppler wind lidar system with measurements conducted during different measurement campaigns and under different atmospheric conditions. In light of these results, further ideas for the implementation of a dedicated heterodyne high spectral resolution lidar are discussed.

Droplet sizing and mixture fraction measurement in liquid–liquid flows with rainbow-angle diffractometry

Mariam Ouattara, Fabrice Lamadie, Matthias Sentis, and Fabrice Onofri

Doc ID: 304639 Received 10 Aug 2017; Accepted 12 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: The capabilities and resolution of the rainbow technique to estimate the size distribution and composition of droplets in liquid–liquid systems were investigated. For these droplets essentially characterized by a low relative refractive index (m=1.001–1.20), the first rainbow is localized in the near-forward to sideways region. It exhibits an unusually higher contrast in the parallel polarization due to the vicinity of the rainbow and the Brewster angles. A numerical study revealed that a few thousands to ten thousands of droplets were necessary to get reliable estimations of the first moments of typical droplet size distributions when the diffractometer is operated as an ensemble averaging technique. The importance of the accuracy of the light scattering model and the inverse methods used is also documented. Experimental results performed on free-rising submillimeter to millimeter droplets of various compositions showed that a global resolution of 1 to 5% of their mean diameter and about 1.6 10-4 of the dispersion on the their refractive index (i.e., 3% in the mixture fraction of oily droplets in water) could be achieved, which enhances the perspectives on mixing and extraction studies in liquid–liquid systems.

Broadband 2×2 lithium niobate electro-optic switchbased on Mach-Zehnder interferometer with countertapereddirectional couplers

Hang Li Wang, Peng Xue Li, Mengruo Zhang, and Kaixin Chen

Doc ID: 305402 Received 22 Aug 2017; Accepted 12 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: We demonstrate a broadband 2×2 electro-optic switch based on Mach-Zehnder interferometer (MZI) with countertapereddirectional couplers (DCs). The counter-tapered DC is introduced here to replace the conventional oneformed with uniform waveguides so that a splitting ratio of 50% : 50% is much easier to be realized over a widewavelength range, and hence increase bandwidth of the switch. The proposed switch is fabricated with x-cutlithium niobate by the annealed proton exchange process. A comparison of several experimental devices,fabricated on the same chip with the conventional and different counter-tapered DC, respectively, confirms theincrease of the bandwidth and the improvement of the fabrication tolerance by using the counter-tapered DC. Ourfabricated best device, which has a length of ~22 mm, exhibits a ~85 nm bandwidth for an extinction ratio higherthan 15 dB and a maximum ER of ~35 dB at 1563 nm at a driving voltage of 6.0 V. The insertion losses are less than8.5 dB for all channels. Our proposed optical switch could find applications in wavelength-division-multiplexingoptical communication systems.

Low driving voltage ITO dropped polymer-dispersed liquid crystal film and reverse voltage pulse driving method

Wu Qinqin and Wang Yuanqing

Doc ID: 297756 Received 08 Jun 2017; Accepted 11 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: This article investigates the effects of indium tin oxide (ITO) on the driving voltages of the polymer dispersed liquid crystal (PDLC). The threshold voltage (Vth) and driving voltage (Vd) can be reduced with dropping the ITO powers. Especially the Vd is 5.8V when the ratio of ITO is 1.5 wt%. The relationship between the applied voltage and off-time of PDLC has been investigated; the lower applied voltage, the shorter off-time; on this basis, the reverse voltage pulse driving method was proposed, this driving method using driving signal to reduce the off-time of PDLC.

Improved cumulative probabilities and range accuracyof a pulsed Gm-APD laser ranging system withturbulence effects

Hanjun Luo, Zhengbiao Ouyang, Qiang Liu, Zhenli Lu, and Bin Li

Doc ID: 297621 Received 08 Jun 2017; Accepted 11 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: There exists a performance limitation in a pulsed Gm-APD laser ranging system because of the echo intensityrandom fluctuation caused by the turbulence effects. To suppress the influence of turbulence effects, we present acumulative pulses detection technique with the ability to achieve improved cumulative probabilities and rangeaccuracy. Based on the modulated Poisson model, the cumulative probabilities, range accuracy and theirinfluencing factors are investigated for a cumulative Q-switched laser pulse train. The results show that theimproved cumulative probabilities and range accuracy can be obtained by utilizing the cumulative pulses detection,with the condition that the echo intensity is 10, the echo pulse width is 10 ns, and the turbulence degree is 3, thetarget detection probability increases by 0.4, the false alarm probability decreases by 0.08, and the accuracy andprecision increase by 46 cm and 27 cm, respectively.

Development of a Compact Underwater LIBS System and the Preliminary Results in the Sea Trials

Jinjia Guo, Yuan Lu, Kai Cheng, Jiaojian Song, Wangquan Ye, Nan Li, and Ronger Zheng

Doc ID: 303639 Received 28 Jul 2017; Accepted 11 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: The exploitation and research of deep-sea hydrothermal vent is a hot issue of ocean research in recent years. Laserinduced breakdown spectroscopy (LIBS) has great potential for ocean application due to the capabilities of standoff,multi-phase and multi-element analysis. In this work, a newly developed compact 4000 m rated LIBS system(LIBSea) is introduced with preliminary results of Sea Trials. The underwater system consists of an Nd: YAG singlepulsed laser operating at 1064nm, an optical fiber spectrometer, an optics module and an electronic controllermodule. The whole system is housed in an L800mm×Φ258mm pressure housing with an optical window on theend cap. It was deployed on the remote operated vehicle (ROV) Faxian on research vessel Kexue, and in June 2015was successfully applied for hydrothermal field measurements at Manus area. The obtained results are shown thatthe LIBS system is capable of detecting elements Li, Na, K, Ca and Mg in the hydrothermal area. Profiles of LIBSsignals of elements K and Ca have also been obtained during sea trial. The results show that the K emission line isgradually broadened with depth from sea surface to seafloor (1800m or so); the K intensity shows a hump shapewith maximum value at about 1050m. The Ca emission line is rapidly broadened below 400 m and slowlynarrowed to the seafloor; the Ca intensity shows no obvious change below 400m and increases continuously toseafloor. A very interesting finding is that the small fluctuations of intensity profile curve of Ca show a degree ofcorrelation with seawater temperature change. The sea trial results prove the performance of LIBSea. Afterfurther optimization, it is hoped to apply the LIBS system to the in-situ mineral deposits and hydrothermal ventfluid detection in deep-sea.

Dependence of the Plasmon Coupling on the CurvedInterfaces

Yuan Ni, Caixia Kan, Juan Xu, Yang Liu, Haiying Xu, and Changshun Wang

Doc ID: 302145 Received 11 Jul 2017; Accepted 11 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: The optical properties of coupled plasmon systems can be tuned by individual material and geometry, gapdistance, and surrounding dielectric. This paper reports a dramatic effect of curved interface in the nanoparticlesdimer on the optical responses. Compared with gold nanorod (AuNR) monomer, AuNRs dimers with differentassembly types (such as end-to-end and side-by-side) can manipulate the longitudinal surface plasmon resonance(SPRL) to red/blue-shift. And the electromagnetic field of dimer is further enhanced in the interactive region.Under the incident polarization along the gap, a new resonance mode will be excited when AuNRs dimers touchwith each other, and SPR mode turns to blue-shift from red-shift due to the formation of the conductive coupling.It can been obtained that when one of the interactive surfaces is curved, an additional plasmon resonance can bestimulated under the polarization of incident light along the gap. The particular phenomenon can be explained bythe plamon hybridization theory. Silver (Ag) nanocube dimer (with sharp or smooth corners and edges) alsopossess the same property. Supported by finite-different time-domain (FDTD) solutions, the coupled plasmonresonance mode represents high sensitivity to structural geometry.

A novel surface recovery algorithm in white lightinterferometry based on combined white light phaseshiftingand fast Fourier transform algorithms

Vo Sang, Fengzhou Fang, Xiaodong Zhang, and Huimin Gao

Doc ID: 303931 Received 02 Aug 2017; Accepted 11 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: Quality control of micro–nano structured and freeform surfaces is becoming increasingly important, which leads to challenging requirements in the measurement and characterization of rough and highly reflective surfaces. As an important measurement technique, white light scanning interferometry (WLSI) is a fast non-contact method to measure three-dimensional (3D) surface profiles. Nevertheless, the existing WLSI 3D surface reconstruction algorithms are prone to environmental vibrations and phase changes caused by reflections on the tested surface. A novel peak detecting algorithm that combines the white light phase-shifting interferometry (WLPSI) method and fast Fourier transform (FFT) coherence-peak-sensing technique is proposed in this paper, which can accurately determine the local fringe peak and improve the vertical resolution of the measurement. A micro-component (10μm standard step height) and a spherical surface were used as test specimens to evaluate the proposed method. Both simulated and experimental results show that the proposed algorithm improves the precision and anti-interference ability of the WLPSI and FFT methods, which can effectively reduce the batwing effects at the edges and solve the problem of positioning error in the maximum modulation.

Analysis of beam propagation characteristics in gainguided, index anti-guided fibers with beampropagation method

Fei Ai, Jianqiang Qian, Junfeng Shi, and Machi Zhang

Doc ID: 304006 Received 04 Aug 2017; Accepted 11 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: The transmission properties of beams in gain fibers is studied with complex refractive index beam propagationmethod (CRI-BPM). The method is checked by compared with an analytic method. The behavior of a gain guided,index anti-guided (GG-IAG) fiber with different gain coefficients is studied. The simulation results show that thesignal can transfer in the fiber with almost no loss when the gain coefficient reaches the threshold of thefundamental mode, and the shape of output spot will have no major changes when the gain coefficient is over thethresholds of high-order modes, even when the mode competition is not obvious. The CRI-BPM can predict thechanges in light power and light mode at the same time, and will be very useful in the designing of fiber amplifiersand lasers with complex structures. More factors will be considered in this method to provide reference forpractical application in our further research.

Polarization smoothing for single beam by nematicliquid crystal scrambler

YuanCheng Wang, Fang Wang, Ying Zhang, xiaoxia huang, Dongxia Hu, wanguo zheng, Rihong Zhu, and Xuewei Deng

Doc ID: 304196 Received 04 Aug 2017; Accepted 11 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: Polarization smoothing (PS) is a key approach to suppress laser plasma instabilities (LPI) in inertial confinementfusion (ICF) experiment. We propose a liquid crystal (LC) PS element here to realize single beam smoothing anddemonstrate its smoothing effect in principle with a 2×2 LC polarization checkerboard, by using which, the laserintensity variation in focal spot is reduced to 78.4%. LC PS elements have many advantages, because they are easyto fabricate, cost-effective, flexible, and large size, which has potential applications in high-power ICF laser drivers.

Effects of a nonideal half-wave plate on the gain ratio calibration measurements in polarization lidars

jing luo, Dong Liu, binyu wang, Lei Bi, Kejun Zhang, Yuling Lui, chunao wen, lingying jiang, Liming Yang, and lin su

Doc ID: 304373 Received 07 Aug 2017; Accepted 10 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: A half-wave plate (HWP) is a critical component for calibrating the gain ratio in polarization lidars. In this paper, the effects of a nonideal HWP on the gain ratio calibration measurements are analyzed. We focus on the method and the multi-rotation HWP method, which are the two main approaches for calibrating the gain ratio. Specifically, we discuss the influences of a nonideal HWP from two aspects: an HWP with nonideal polarization properties and an ideal HWP under nonideal external conditions. The allowable ranges of relevant parameters for the nonideal polarization properties of HWPs are obtained, which can help to determine qualified HWPs in polarization lidars. Several external conditions including ambient temperature variations, wavelength differences and the tilt angles of HWPs are also analyzed in detail. To the best of our knowledge, this paper represents the first comprehensive study on the effects of nonideal HWPs on the gain ratio calibration measurements, offering some guidelines on choosing a qualified HWP for proper use in polarization lidars.

High spatial resolution zonal reconstruction withmodified multi-shear method in frequency domain

Dede Zhai, Shanyong chen, and Feng Shi

Doc ID: 302628 Received 18 Jul 2017; Accepted 10 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: An exact multi-shear zonal algorithm is proposed to reconstruct two-dimensional wavefronts in frequency domain.The algorithm maintains the advantage of fast Fourier transform and looses the ‘natural extension’ requirementthat the shear amounts must be divisors of sampling points N, therefore, it can be rapidly executed for large dataarrays. The effect of tilt errors in multi-shear interferometry is analyzed and compensated in our method. Thepresented algorithm is applicable for general aperture shape by using an iterative method. Application of largeshears is allowed, and high resolution of the reconstructed wavefront can be achieved. Results of numericalsimulations demonstrate the capability of our method.

Fiber-based tools; material removal and mid spatial frequency error reduction

Hossein Shahinian, Mohammed Hassan, Harish Cherukuri, and Brigid Mullany

Doc ID: 302390 Received 20 Jul 2017; Accepted 09 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: This paper details the feasibility of using fiber-based tools in a CNC environment to process optical materials, and their ability to reduce the amplitude of pre-existing mid spatial frequency (MSF) surface errors. The work is motivated by earlier research conducted by the group exploring the ability of polymeric fiber based tools to remove material from BK7 glass substrates. To evaluate these tools in a CNC environment three tasks are explored. Firstly, the ability of the tools to maintain their form and material removal profile while operating under translational conditions. Secondly, the ability of the tools to disengage and reengage with the workpiece edge and how this affects the tool’s material removal profile. Finite element (FE) modelling of the fiber-workpiece edge interaction was conducted to support the experimental work. And thirdly, to verify the deterministic behavior of the tool under full raster conditions. Testing on a 3-axis CNC machine tool demonstrated that the tooling is sufficiently robust and stable to operate under translational and rotational speeds of 30 mm/s and 1000 rpm respectively. Both the FE modeling and experimental testing confirmed the truncation of a fiber’s material removal profile as a fiber extends beyond the workpiece edge. While higher than predicted material removal rates were obtained during translation tests, the shape of the material removal profile agrees with that predicted by convolution. Completion of a full raster tests on BK7 produced negligible form errors and no unexpected mid spatial frequency (MSF) errors. The ability of fiber based tools to reduce MSF errors was explored both through FE modeling and experimental testing on germanium samples. The samples were patterned with concentric sinusoidal features to represent MSF errors with a wavelength = 1 mm and a peak to valley (PV) of 200 nm. An FE model created to assess the deformation of a nylon 6/6 fiber between 1 mm spaced points predicted low level of deformation (~10nm), suggesting that more material will be removed from the higher than the lower regions of the surface features. Polishing tests conducted on the aforementioned germanium sample confirm that this is the case and that fiber based tools can reduce pre-existing MSF errors.

Dynamic wavefront measurement with a pinhole linear polarizer point-diffraction interferometer

Xiang Zhou, Renhui Guo, Wenhua Zhu, Donghui Zheng, and Lei Chen

Doc ID: 302789 Received 20 Jul 2017; Accepted 08 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We propose a pinhole linear polarizer point-diffraction interferometer (PLP-PDI) for dynamic wavefront measurements. The proposed interferometer uses a metallic wire grid linear polarizer that acts as a point-diffraction plate to generate an ideal spherical wave, from which we can obtain orthogonally polarized reference and test beams. The special polarization phase-shifting configuration allows four phase-shifted interferograms to be captured in a single shot with high precision and stability. The wavefront can then be reconstructed using a phase unwrapping algorithm. In this paper, we describe the theory of the PLP-PDI and analyze the possible errors introduced by the device. The feasibility of the proposed PLP-PDI was verified by direct measurements of a wavefront. The experimental results show that the proposed PLP-PDI is an effective and efficient tool for the dynamic measurement of wavefronts.

Dual-sensitivity profilometry with defocused projection of binary fringes

Msc Garnica, Moises Padilla, and Manuel Servin

Doc ID: 302378 Received 13 Jul 2017; Accepted 08 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: A dual-sensitivity profilometry technique based on defocused projection of binary fringes is presented. Two sets of fringe patterns with sinusoidal profile are produced for the proposed technique by applying the same analog low-pass filter (projector defocusing) to binary fringes with high and low-frequency spatial carrier. The high-frequency fringes have a binary square-wave profile, while the low-frequency fringes are produced with error diffusion dithering. The binary nature of the modified fringe patterns removes the need for calibration of the projector’s non-linear gamma. Working with high-frequency carrier fringes, we obtain a high-quality wrapped estimation. On the other hand, working with low-frequency carrier fringes we found a low-quality but non-wrapped phase map. The non-wrapped estimation is used as stepping stone for dual-sensitivity temporal phase-unwrapping of the high-quality measurement. This maximizes the applicability of the binary-fringes defocused-projection profilometry technique: previous approaches were restricted to either low or high frequency, but our approach produces high-quality results and it is applicable to discontinuous (piecewise continuous) surfaces. The proposed technique is validated with experimental results.

Dispersion engineering of a microsphere via multi-layer coating

Xueying Jin, Jing Wang, MengYu Wang, Yongchao Dong, Fei Li, and Wang Wang

Doc ID: 301927 Received 10 Jul 2017; Accepted 08 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: Controlling dispersion of a whispering gallery mode resonator (WGMR) is of critical importance for many nonlinear applications. Here, we show by numerical and theoretical modeling that dispersion can be strongly engineered in a three-layer-coated microsphere of high, low, and high refractive indices (RIs). We investigated the impact of the coating thickness, the gap between the two high-RI layers, the surrounding medium, and the coating materials on the group velocity dispersion (GVD) and discovered that, the dispersion is highly controllable over a very broad range in both normal and anomalous dispersion regime. Our approach provides a great dispersion engineering flexibility in any axisymmetric resonator with a three-layer coating structure.

Optimal defocus selection based on normed Fouriertransform for digital fringe pattern profilometry.

abel kamagara, Xiangzhao Wang, and Si Li

Doc ID: 291829 Received 03 Apr 2017; Accepted 07 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: Owing to gamma-effect robustness and high-speed imaging capabilities, projector defocusing of binary-coded fringepattern is by far the most widely used and effective technique in generating sinusoidal fringe patterns for threedimensionaloptical topography measurement with digital fringe projection techniques. However, this technique is nottrouble-free. It is borne with uncertainty and challenges mainly because it remains somewhat difficult to quantify andascertain the level of defocus required for desired fidelity in sinuousness of projected fringe pattern. Too much or too littledefocusing will affect sinuosity accuracy of fringe patterns and subsequently jeopardize the quality of the measurementresults. In this paper, by combining intrinsic phase spectral sensitivities and normed Fourier transform, a method toquantify the amount of defocus and subsequently select optimal degree of sinuosity for generating digital sinusoidal fringepattern with projector defocusing for fringe pattern optical three-dimensional profilometry is proposed. Numericalsimulations plus experiments give evidence of the feasibility and validity of proposed method in enabling an improveddigital binary defocusing technique for optical phase shift profilometry using digital fringe projection technique.

Simultaneous Analysis of Cr and Pb in Contaminated Pork by Laser Induced Breakdown Spectroscopy

Mingyin Yao, gangfu rao, Lin Huang, Muhua Liu, hui yang, and tianbing chen

Doc ID: 297197 Received 01 Jun 2017; Accepted 07 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: Laser-induced breakdown spectroscopy (LIBS) as a rapid and green method was focused on the detection of heavy metals Cr and Pb in pork contaminated in lab. The laser induced plasma was generated by a Q-switched Nd:YAG laser, the LIBS signal was collected by spectrometer with charge-coupled device (CCD) detector. The traditional calibration curves (CC) and multivariate partial least squares (PLS) algorithm were applied and compared to validate the accuracy in predicting the content of heavy metals in samples. The results demonstrated that the correlation coefficient of CC is poor by the classical univariate calibration method. So the univariate calibration analysis cannot effectively serve the quantitative purpose in analyzing heavy metals residue in pork with complex matrix. The analysis accuracy was improved effectively by PLS method, the correlation coefficient is 0.9894 for Cr and 0.9908 for Pb. The concentration of Cr and Pb in samples from prediction set was obtained using PLS calibration method, and the average relative errors for the 21 samples in prediction set are lower than 6.53% and 7.82% for Cr and Pb, respectively. The investigated results display that the matrix effect would be reduced effectively during the quantitative analysis of pork by LIBS combined PLS model, and the predictive accuracy would be improved greatly comparing traditional univariate analysis.

Nondestructive determination of optical properties of pear using spatial frequency domain imaging combined with phase-measuring profilometry

Xueming He, Xiaping Fu, Xiuqin Rao, and Feng Fu

Doc ID: 301421 Received 30 Jun 2017; Accepted 07 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: Spatial frequency domain imaging (SFDI), as a rapid, noncontact and scan-free method, can realize wide-field, quantitative optical property mapping and tomographic imaging for biological sample. And phase-measuring profilometry (PMP) is one of surface profile characterization methods. Since the projection of structured light onto an object is the basis for both PMP and SFDI, the SFDI system is capable of performing both techniques. In this work, we presented the results of a feasibility study with the developed SFDI system to realize acquisition of both the optical property information and the surface profile information. And the surface profile information was used to correct the absorption (μa) maps and reduced scattering (μ’s) maps. The evaluation of correction effect of the PMP, the calibration and the calculation of detection accuracy of SFDI system were realized by using a series of self-made hemispheric and homogeneous solid phantoms covering a wide range of absorption and reduced scattering coefficients. The results showed that the μa and μ’s maps become more uniform after using profilometry correction. The maximum relative errors of the system after profilometry correction and calibration were 8.74% for μa and 4.97% for μ’s at the wavelength of 527 nm respectively. A case study was carried on pear to verify the application prospect of the method in the field of agricultural products quality inspection. Results indicated that the μa and μ’s maps of pear after profilometry correction and calibration were more uniform, and were more comparable to the reported values.

Optical beam deflection sensor: design and experiments

João Marcos Salvi Sakamoto, Renan Marques, Cláudio Kitano, Nicolau Rodrigues, and Rudimar Riva

Doc ID: 303504 Received 28 Jul 2017; Accepted 07 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: In this work we present a double pass optical beam deflection sensor and its optical design method. To accomplish that, a mathematical model was proposed and computational simulations were performed, in order to obtain the sensor's characteristic curves and to analyze its behavior as function of design parameters. The mathematical model was validated by comparison with the characteristic curves acquired experimentally. The sensor was employed to detect acoustic pulses generated by a pulsed laser in a sample surface, in order to show its potential for monitoring applications handling high energy input as laser welding or laser ablation.

Experimental demonstration of 12.5 GHz wideband chaos in symmetric dual port EDFRL

Shubham Mirg, Ankita Jain, Akash Pandey, Pradeep Kumar Krishnamurthy, and Pascal Landais

Doc ID: 303752 Received 01 Aug 2017; Accepted 06 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: We study dynamics of chaos in dual port erbium-doped fiber ring laser (EDFRL). The laser consists of two erbium-doped fibers, intracavity filters at 1549.30 nm, isolators, and couplers. At both ports, the laser transitions into the chaotic regime for pump currents greater than 100 mA via period doubling route. We calculate the largest Lyapunov exponent using Rosenstein’s algorithm. We obtain positive values for the largest Lyapunov exponent (≈ 0.2) for embedding dimensions 5, 7, 9 and 11 indicating chaos. We compute the power spectral density of the photocurrents at the output ports of the laser. We observe a bandwidth of ≈ 12.5 GHz at both ports. This ultra wideband nature of chaos obtained has potential applications in high speed random number generation and communication.

An adaptive measurement method for miniature spectrometers used in cold environments

Hangzhou Wang, Liwen Nan, Hui Huang, Ping Yang, Hong Song, Jiwan Han, Yuanqian Wu, Tingting Yan, Zhuoli Yuan, and Ying Chen

Doc ID: 294673 Received 05 May 2017; Accepted 06 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: Adaptive measurement is a major concern when using miniature spectrometers in extreme environments, especially when the ambient temperatures and incident light intensities vary greatly. In this study, parameters, including the signal output and the relevant noise and signal-to-noise ratio (SNR) of a fiber optic spectrometry system composed of a photodiode array miniature spectrometer and external driver electronics were examined at multiple integration times from -50°C to 30°C, well below the specified operating temperature of this spectrometer. The relationships between those parameters and incident light level were also examined, at a single temperature of 0°C. Based on these examinations, temperature-induced biases in the linear operating range of the spectrometer were identified. Signal output and the relevant noise and SNR in response to different integration times, temperatures and incident light levels were assessed separately. These assessments were then used to develop an adaptive measurement method for setting up an appropriate integration time for this spectrometer, while autonomously adapting the variation in the ambient temperature and incident light level during the field application. This approach provides a general framework for developing adaptive measurement algorithm for miniature spectrometers which will face with tremendous variations in the ambient temperature and incident light level.

An image decomposition fusion method based on sparse representation and neural network

Lihong Chang, Xiangchu Feng, Rui Zhang, Hua Huang, Weiwei Wang, and Chen Xu

Doc ID: 298076 Received 20 Jun 2017; Accepted 06 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: For noisy images, most existing sparse representation-based models fusion and denoising proceed simultaneously using thecoefficients of a universal dictionary. This paper proposes an image fusion method based on a cartoon + texture dictionary paircombined with deep neural network combination (DNNC). In our model, denoising and fusion are carried out alternately. Theproposed method is divided into three main steps: denoising + fusion + network denoising. More specifically (1)denoise thesource images using external/internal methods separately. (2) fuse these preliminary denoised results with external/internalcartoon and texture dictionary pair to obtain the E-CTSR (using external denoising and external dictionary pair) and I-CTSR(using internal denoising and internal dictionary pair) images; and (3)combine E-CTSR and I-CTSR using DNNC to obtain the finalresult of EI-CTSR. Experimental results demonstrate that EI-CTSR outperforms not only the stand-alone E-CTSR and I-CTSRmethods but also the state-of-the-art methods such as sparse representation (SR) and adaptive sparse representation (ASR) forisomorphic images, and E-CTSR outperforms SR and ASR for heterogeneous multi-mode images.

Selective photo-oxidation induced bi-periodic plasmonic structures for high-density data storage

Xiuxiu Han, Shencheng Fu, Xintong Zhang, Shuang Lu, Shuangyan Liu, Xinnong Wang, Ruiya Ji, Xiuli Wang, Yichun Liu, and Jinhuan Li

Doc ID: 300800 Received 26 Jun 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: Stable and controllable optical memory is necessary for the development of current information technology. Ag/TiO2 films have got much attention for their photo-sensitivity in wavelength and polarization, which can be applied to high-density optical storage. Here, we carried out dual-wavelength holographic recording using 403.4 nm and 532 nm lasers, and obtained mixed micro-fringes based on selective photo-dissolution of Ag nanoparticles with various sizes in TiO2 nanoporous films. Two recording methods of simultaneous and sequential multiplexing were investigated. It was found that the simultaneous irradiation is easier to obtain the equivalent efficiency in both spectral hole-burning and multiplexed gratings diffraction, compared with that of the sequential one. The results can be explained by Time-accumulation Effect during Ag+ ion diffusion and migration in holographic recordings. Based on such properties, multiplexed-holographic fringes with uniform contrast were reserved by the simultaneous recording in Ag/TiO2 films. This work provides a new strategy for fabrication of photonic devices with complex microstructures.

Utilizing Electromagnetically Induced Transparency in InAs Quanum Dots for All-Optical Transistor Design

Rana Asgari Sabet, Mostafa Sahrai, and Hamed Sattari

Doc ID: 302015 Received 10 Jul 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: We propose a multilayer medium with semiconductor quantum dot nano-structures as a defect layer for all-optical control of the1.55μm probe beam. The effect of the coupling field and incoherent pump on absorption and dispersion properties of the quantum dot defect layer is investigated. Depending on the intensity of coupling field and rate of the incoherent pump field, the possibility of the absorption cancellation and even amplification are demonstrated. The optimum values of the coupling field intensity and incoherent pump field for completely transmission or amplification are obtained. The dynamical behavior of the structure is investigated and the estimated switching time scales are about tens picoseconds.

Measuring optical constants of ultrathin layers using SPR-based imaging ellipsometry

Yao Shan, Guohang Hu, liyuan Gu, Hongbo He, Aijun Zeng, Yuanan Zhao, and Anna Sytchkova

Doc ID: 302365 Received 17 Jul 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: A setup for surface plasmon resonance (SPR)-based imaging ellipsometry (SPRIE) was developed which gains from sensitivity of both SPR and ellipsometry to ultrathin film parameters. It is based on Otto’s configuration for prism-sample coupling and a wide-beam imaging ellipsometry. A set of ultrathin gold and silver films was measured to determine their optical constants and thickness. Coupling the sample using a prism having convex surface enables capturing the images of generated SPR elliptical fringes, which correspond to different SPR absorptance values. The analysis of the images acquired at different air gap thickness and at different polarizer and analyzer angles provides the ellipsometric functions Ψ and Δ versus thickness of air gap and hence the extraction of the optical constants of ultrathin metal films. The measured film thickness is in agreement with the results of X-ray reflectivity measurements.

Development and accuracy of a multi-point method for measuring visibility

Hongda Tai, zhuang zibo, and Dongsong Sun

Doc ID: 302497 Received 19 Jul 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: Accurate measurements of visibility are of great importance in many fields. This article reports a multi-point visibility measurement (MVM) method to measure and calculate the atmospheric transmittance, extinction coefficient and meteorological optical range (MOR). The relative errors measured by the MVM system are analyzed and compared. An experiment was conducted indoor and the data were simultaneously processed using the MVM and transmissometer method. The results revealed that the MVM can effectively improve the accuracy under different visibility conditions. The greatest improvement of accuracy was 27%. MVM can be used to calibrate and evaluate visibility meters.

Signal detection algorithms for interferometric sensors with harmonic phase modulation: distortion analysis and suppression

Leonid Liokumovich, Andrey Medvedev, Konstantin Muravyov, Philipp Skliarov, and Nikolai Ushakov

Doc ID: 297164 Received 31 May 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: In current paper, distortions in digital demodulation schemes with harmonic phase modulation for interferometric optical sensors are considered. In particular, the influence of target signal variations on phase demodulation errors is theoretically evaluated. An analytical expression, describing the phase error magnitude dependence on first derivative and mean value of measured signal and amplitude of the phase modulation in case of simple 4-point demodulation algorithm is derived. After that, an approach for synthesizing algorithms with suppressed sensitivity to target signal variations is developed. Based on this approach, a novel 4+1 demodulation algorithm is proposed. It is shown analytically that the demodulation error of new 4+1 algorithm is proportional to the second derivative of target signal, and therefore, is typically several orders of magnitude smaller than in case of 4-point algorithm. The correspondence between analytical expressions and real phase errors, induced by target signal variations is verified by means of numeric simulation.

Design of a compact device to generate and test beams with orbital angular momentum in the EUV.

Dudbil Pabon Riaño, Silvia Ledesma, Guillermo Quinteiro, and Maria Gabriela Capeluto

Doc ID: 298013 Received 16 Jun 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: We present a compact design to generate and test optical- vortex beams with possible applications in the Extreme Ultraviolet (EUV) region of the electromagnetic spectrum. The device consists of a diffractive mask where both, the beam with orbital angular momentum and the reference wavefront to test its phase are generated. In order to show that the proposal would work in the EUV, simulations and proof-of-principle experiments were performed, using typical parameters for EUV holography scaled to visible wavelengths. As the simplest case, we consider the well-known Laguerre-Gaussian like (LG) beams, which have a single vortex in the propagation axis. To further test the versatility of the device, we consider Mathieu beams, a more complex structured beam, that may contain several vortices. In the experiment a spatial light modulator (SLM) was used to display the mask. As examples, we show the results for a LG-like beam with topological charge l=1 and Mathieu beams with topological charge l=2 and ellipticity q=2. These results show the potential of the device to generate a variety of beam shapes at EUV wavelengths.

A tuneable and switchable liquid crystal laser protection system

Ethan Jull and Helen Gleeson

Doc ID: 303832 Received 01 Aug 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: The use of a liquid crystal Lyot filter as a simple and compact switchable laser protection system is demonstrated. The system OFF state exhibits a wavelength independent transmission and switches to an ON state, which rejects a selected wavelength. The response time of the switchable system is < 110 ms, depending on the rejected wavelength, with the ability for faster switching of < 5ms when using a lower order rejection band. A rejection tuning range between 480 and 640 nm is demonstrated and the potential to operate outside of the visible spectrum is discussed. In the ON state the transmission at the rejected wavelength was found to be effectively limited by the polariser extinction ratio, whilst transmission at other wavelengths allows for partial observations through the system even when in protection mode.

Integrated Reconfigurable Photonic Filters based on Interferometric Fractional Hilbert Transforms

Chaotan Sima, Binchen Cai, Liu Bolan, Yuan Gao, Yu YU, James Gates, Michalis Zervas, Peter Smith, and Deming Liu

Doc ID: 305170 Received 21 Aug 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: In this paper, we present integrated reconfigurable photonic filters using fractional Hilbert transformers (FrHTs) and optical phase tuning structure within the silica-on-silicon platform. The proposed structure, including grating based FrHTs, an X-coupler and a pair of thermal tuning filaments, is fabricated through the direct UV grating writing technique. The thermal tuning effect is realized by the controllable micro heaters located on the two arms of the X-coupler. We investigate the 200GHz maximum bandwidth photonic FrHTs based on apodized planar Bragg gratings, and analyze the reflection spectrum responses. Through the device integration and thermally modulation, the device could operate as photonic notch filters with 5GHz linewidth and controllable single sideband (SSB) suppression filters with measured 12dB suppression ratio. A 50GHz instantaneous frequency measuring system using this device is also schematically proposed and analyzed with potential 3dB measurement improvement. The device could be configured with these multiple functions according to needs. The proposed structure has great potential in ultrafast all-optical signal processing fields。

Frequency Dependent Noise Figure Analysis of Continuous Photonic Time-Stretch System

Boyu Xu, Changqiao Liu, Xiaofeng Jin, Xiangdong Jin, Xianbin Yu, Hao Chi, Shilie Zheng, and Xianmin Zhang

Doc ID: 297911 Received 12 Jun 2017; Accepted 05 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: In this paper, the frequency dependent noise figure of a continuous photonic time-stretch system is theoretically analyzed and experimentally demonstrated. Mathematic analysis discloses that the frequency dependent noise figure in the continuous photonic time-stretch system is mainly owing to the dispersion induced phase shift in the link. In the experiment, a completely-continuous signal is reconstructed with time-interleaved jointing of 4 sections of time-stretched signals from optical wavelength-division de-multiplexing channels. The result of frequency dependent noise figure property agrees well with that of theoretical analysis.

Thermally stable multi-color phosphor-in-glassbonded on flip-chip UV-LEDs for chromaticity-tunableWLEDs

Pengqiang Jiang, Yang Peng, Yun Mou, Hao Cheng, and Mingxiang Chen

Doc ID: 297366 Received 05 Jun 2017; Accepted 04 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: In this paper, we proposed a thermally stable multi-color phosphor-in-glass (PiG) for chromaticity-tunable whitelight-emitting diodes (WLEDs). The multi-color PiG has a red, green, and blue (RGB) phosphors glass layer, whichwas screen-printed and co-sintered on a glass plate with a low temperature of 600°C. The WLED with ultra-compactstructure was fabricated by the RGB-PiG directly bonded on a flip-chip ultraviolet (UV) LED. By controlling theweight ratio of R:G:B phosphors, the thickness of RGB layer, and the weight ratio of phosphors to glass powders(PtG), the chromaticity of RGB-PiG based WLEDs can be effectively tuned with high color quality. As the R:G:B ratioof 2:3:2, the RGB thickness of 75 μm, and the PtG ratio of 2:1, the RGB-PiG based WLED achieves a natural whitelight with a luminous efficacy (LE) of 27.8 lm/W, a correlated color temperature (CCT) of 4245 K, and a colorrendering index (CRI) of 92.6 at the current of 350 mA. The LE losses of the RGB-PiG based and RGB phosphor-insilicone(PiS) based WLEDs are 4.7% and 14.6% after the aging tests of 1000 h at 100°C, respectively. The resultsdemonstrate that the multi-color PiG is a promising converter for UV-excited WLEDs.

Reflection characterization of anisotropic dielectric function of two-dimensional materials on semiconductor or metallic substrates

Peep Adamson

Doc ID: 297742 Received 08 Jun 2017; Accepted 04 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: A new optical method for determining anisotropic dielectric constants of graphene-like two-dimensional materials on semiconductor or metal substrates is developed. The method is based on the surface differential reflectance measurements at three different incident angles. The inversion problem is resolved analytically in a long-wavelength approximation where graphene is discussed within the framework of macroscopic electrodynamics as an uniaxially anisotropic film with the optical axis perpendicular to the film surface. The method is fast and has no need for the initial guesses of the desired parameters. It also offers an interest as an effective technique to get good start points for iterative numerical methods to improve the preliminary results. The method is unique in its simplicity and, therefore, important for graphene research.

Passive ranging using filter-based non-imaging method based on oxygen absorption

Hao Yu, Bingqi Liu, Zongqun Yan, and Yu Zhang

Doc ID: 298136 Received 14 Jun 2017; Accepted 04 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: In order to solve the problem of poor real-time measurement caused by the hyperspectral imaging system and to simplify the design in passive ranging technology based on oxygen absorption spectrum, a filter-based non-imaging ranging method is proposed. In this method, three band pass filters are used to obtain the source radiation intensities which are located in the oxygen absorption band near 762nm and the band’s left and right non-absorption shoulders, and a photomultiplier tube is used as the non-imaging sensor of the passive ranging system. Range is estimated by comparing the calculated values of band-average transmission due to oxygen absorption, , against predicted curve of versus range. The method is tested under short-range conditions. Accuracy of 6.5% is achieved with the designed experimental ranging system at the range of 400m.

Analysis on Multifocal Contact Lens Design Based on Optical Power Distribution with NURBS

Lien Vu, Chao-Chang Chen, and Patrick Joi-Tsang Shum

Doc ID: 301949 Received 07 Jul 2017; Accepted 03 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: This paper aims to analyze the design method of multifocal contact lens to obtain smooth optical surfaces with high additional (Add) powers by using Non Uniform Rational B-Spline (NURBS) curve. The proposed method develops mathematic formulas to generate optical power distribution in which power continuously changes from either near or distant center to the opposite focal length in the periphery of optical region with different change rates and Add power values. To adapt for these given power profiles, three parameters including control points, weight and knots of the NURBS are optimized to be anterior optical lens surface profiles. The result shows that the proposed contact lens not only achieve smooth and continuous anterior optical surfaces but also satisfy various optical power distributions with high Add power values for different pupil diameters. These designs can be easily transferred to CAD format for analysis or manufacture. The applicability of this method is proven when the power distributions of the simulation lenses and the real samples match with the original required powers.

Transient dynamic distributed strain sensing using photonic crystal waveguides

Hosangadi Sagar, Vignesh Mahalingam, Debiprosad Roy Mahapatra, Gopal Hegde, Sathyanarayana Hanagud, and Mohammad Rahman

Doc ID: 302142 Received 10 Jul 2017; Accepted 01 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: This paper presents a new type one-dimensional photonic crystal (PC) waveguide sensor and a technique for prediction of transient strain response accurately. The photonic crystal waveguide is integrated on a silicon substrate. We investigate the effect of non-uniform strain localization on the optical signal and use that information to capture the transient strain. Wavelength shift due to distributed strain field is modeled by incorporating the mechanically deformed geometry and photo-acoustic coupling through Pockels effect in a finite element formulation. We demonstrate the advantages of using our proposed method, where multiple spectral peak-shift is used instead of single peak shift in order to improve sensing output accuracy and also to estimate the sensor parameter regressively, where the signal’s bandwidth is limited. The maximum sensitivity of the waveguide sensor in terms of wavelength shift is estimated to be 0.36 pm/μstrain in single peak based sensing, whereas, the proposed adaptive multi-spectral estimation scheme shows an enhanced sensitivity of 4.029 pm/μstrain.

Laser absorption precursor research: microstructuresin the subsurface of mono-crystalline silicon substrate

Ye Tian, Shi Feng, Yifan Dai, Xiaoqiang Peng, and Yaoyu Zhong

Doc ID: 297846 Received 09 Jun 2017; Accepted 01 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: In high-energy laser systems, the energy absorption coefficient of silicon optical elements is one of the most criticalserve indicators. The absorption coefficient of substrate limits the absorption of the overall elements. Since monocrystallinesilicon is transparent in working wavelength range, the subsurface absorption precursors also influencethe entire absorption dramatically. In this paper, the subsurface of a super-polished silicon substrate is exposed byion beam etching (IBE) as deep as 4.6μm. In different depth layers, morphology and energy absorption aremeasured with atom force microscope and photothermal instrument, respectively. In 100nm layer,microstructures are found and their heights decrease while widths increase with IBE. Finally, structures arediminished below the 1.12μm layer. Absorption increases with structures appearance. When the structures arefully exposed, absorption reaches the peak value, 327.5% of the unremoved surface. Once structures are removed,the absorption value falls down to the lowest point, 67.5%, which verifies that structures influence the absorptionsignificantly. According to the structure depth and Energy Dispersive Spectrometer (EDS) results, the structuresare most likely the densificated micro zones, generated by fabrication processes. In practical fabrication,subsurface layer of 1.12μm thick needs to be removed by stress-less processes, to obtain a low-absorption element.

Angled-MMI based wavelength splitters on siliconnitride waveguide platforms for fluorescence sensing

Jeong Hwan Song, Tangla Kongnyuy, Naser Hosseini, Pieter Neutens, Federico Buja, Roelof Jansen, and Xavier Rottenberg

Doc ID: 302520 Received 19 Jul 2017; Accepted 01 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: Compact wavelength splitters based on angled-multimode interferometers (AMMIs) on silicon nitride platformsworking in visible lights are reported for fluorescence sensing applications. A diplexer and triplexer with differentfootprints are designed and experimentally demonstrated. The diplexer and triplexer have the insertion loss of~1.7 and ~2.7dB/channel with crosstalks of less than –22dB and –17dB on target wavelengths, respectively. Thesesplitters are used to distinguish the signals collected from two fluorescent dyes that give different emission spectrawhen excited with an excitation source, due to their different Stokes’s shifts. In the case of the triplexer, a third portis to collect the excitation light, both to monitor the remaining excitation power and to reduce in interference at thesignal ports. A termination structure at the end of AMMIs and in- and output tapering waveguides as a part of thewavelength splitters are designed and their performances are presented.

Feasibility study of high spatial resolution multimodality fluorescence tomography in ex vivo biological tissue

Tiffany Kwong, Farouk Nouizi, Jaedu Cho, Yuting Lin, Uma Sampathkumaran, and Gultekin Gulsen

Doc ID: 296768 Received 26 May 2017; Accepted 31 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: Previously, we demonstrated that temperature modulated fluorescence tomography (TM-FT) could provide fluorescence images with high quantitative accuracy and the spatial resolution of focused ultrasound. TM-FT is based on scanning the focused ultrasound across the medium to activate temperature-reversible fluorescent nanoprobes (ThermoDots). This technique can resolve small fluorescent targets located several centimeters deep in turbid media with millimeter resolution. Our past studies with this multimodality technique used agar phantoms, which could not represent the true heterogeneous nature of the acoustic and optical properties of biological tissue. In this work, we report the results of the first TM-FT study performed on ex vivo chicken breast tissue. In order to improve the spatial resolution of this technique, diffuse optical tomography (DOT) is also used to better estimate the optical property maps of the tissue, which is utilized as functional a priori for the TM-FT reconstruction algorithm. These ex vivo results show that TM-FT can accurately recover the concentration and position of a 1.5 mm x 5 mm inclusion filled with ThermoDots. Since the inclusion is embedded 2 cm deep in the chicken breast sample, these results demonstrate the great potential of TM-FT for future in vivo small animal imaging.

Stereo Line-Scan Sensor Calibration for 3D ShapeMeasurement

Bo Sun, jigui zhu, Yang Linghui, yin Guo, and Lin Jia-Rui

Doc ID: 297411 Received 05 Jun 2017; Accepted 31 Aug 2017; Posted 06 Sep 2017  View: PDF

Abstract: Stereo line-scan sensor opens up new potentialities for 3D measurement owing to the ultra-high resolution andacquisition rate. Calibration is a crucial key technology for a stereo line-scan sensor. This paper presents a precisecalibration method for the stereo line-scan sensor. Several reference points are installed onto the sensor’s body asan intermediary. The calibration turns into a two-step process: calibrating the cameras in laboratory prior tomeasurement and locating the sensor in an actual measurement field. A mobile apparatus that comprises a planarpattern and extra reference points is designed. By incorporating the apparatus in combination with auxiliaryinstrument, an optimal calibration configuration is created by placing the apparatus into multiple positions. Arobust algorithm is proposed to enhance the stability of the parameter estimation. The quality of calibrationmethod is experimentally tested and the performance is further investigated. Experimental results demonstratethat the proposed method offers a practical solution to calibrate a stereo line-scan sensor for 3D shapemeasurement.

Low-cost dynamic real-time foveated imager

Yajun Niu, Jun Chang, fengxian lv, benlan shen, and weilin chen

Doc ID: 296089 Received 17 May 2017; Accepted 31 Aug 2017; Posted 06 Sep 2017  View: PDF

Abstract: Foveated imaging system has the ability to capture local high resolution or high magnification images in a wide field-of-view (FOV), thus, it has great potential applications in the field of monitoring and remote sensing of unmanned aerial vehicles. If so, there will be a great demand for the foveated optical system. However, the existing foveated imaging system either is equipped with expensive modulators or fixes the local high resolution imaging field, which is not suitable for mass production or object tracking in industrial applications. We propose a low-cost dynamic real-time foveated imaging system to carry out its wide use in the above applications. Specially, we place a micro lens behind the first intermediary image plane to modulate the local focal length, constructing a local high magnification imaging channel; one two-axis translation stage will drive the micro lens to scan in the plane perpendicular to the optical axis, resulting in dynamic local high magnifying imaging. Furthermore, the peripheral imaging channel and the foveated imaging channel focus on the same detector and the post image fusion is inexistent; the system consists of only common aspherical lens and thus very cheap. The experimental system has a focal length of 25 mm, a full FOV of 30°, an entrance pupil diameter of 5 mm, while the local high magnifying imaging channel has a focal length of 35 mm and a FOV of 15°. Experiment results show that the low-cost dynamic real-time foveated imaging system performs very well.

Astigmatism-corrected echelle spectrometer using off-the-shelf cylindrical lens

Fajie Duan, Xiao Fu, Jiajia Jiang, Tingting Huang, Ling Ma, and Dexter Lv

Doc ID: 296264 Received 18 May 2017; Accepted 31 Aug 2017; Posted 06 Sep 2017  View: PDF

Abstract: As a special kind of spectrometers with Czerny-Turner structure, the echelle spectrometer features two-dimensional dispersion, which leads to complex astigmatic condition. In this work, we propose an optical design of astigmatism-corrected echelle spectrometer using off-the-shelf cylindrical lens. The mathematical model considering astigmatism introduced by the off-axis mirrors, the echelle grating and the prism is established. Our solution features simplified calculation and low-cost construction, which is capable of overall compensating the astigmatism in a wide spectral range (200-600nm). Optical simulation utilizing ZEMAX software, astigmatism assessment based on Zernike polynomials and instrument experiment are implemented to validate the effect of astigmatism correction. The results demonstrated that astigmatism of the echelle spectrometer was corrected to a large extent and high spectral resolution better than 0.1nm was achieved.

Performance of photomultipliers in the context oflaser-induced incandescence

Raphael Mansmann, Thomas Dreier, and Christof Schulz

Doc ID: 301100 Received 05 Jul 2017; Accepted 30 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: Photomultiplier tubes (PMTs) are widely used as detectors for laser-induced incandescence (LII), a diagnosticsmethod for gas-borne particles that requires signal detection over a large dynamic range with nanosecond timeresolution around the signal peak. Especially when more than one PMT is used (i.e., for pyrometric temperaturemeasurements) even small deviations from linear detector response can lead to significant errors. Reasons fornon-linearity observed in other PMT measurement techniques are summarized and strategies to identify nonlinearPMT operation in LII are outlined. To quantify the influence of the non-linear behavior, experiments atsimilar light levels as encountered in LII measurements are carried out and errors propagated in two-colorpyrometry-derived temperatures are determined. As light sources, a calibrated broadband light source and lightemittingdiodes (LED), centered at the bandpass filter wavelengths of the LII detectors, were used. The LEDs wereoperated in continuous and pulsed (< 300 ns) mode, respectively, to simulate DC background radiation (e.g., fromsooting flames) and similar pulsed signal traces as in typical LII measurements. A measured linearity deviation ofup to 10% could bias the temperature determination by several hundred Kelvin. Guidelines are given for thedesign and the operation of LII setups, which allow users to identify and prevent errors.

Surface topography measurement by frequency sweeping digitalholography

Vit Ledl, Pavel Psota, Frantisek Kavan, Ondrej Matousek, and Pavel Mokry

Doc ID: 301647 Received 05 Jul 2017; Accepted 30 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: High precision measurements of surface topography of mechanical parts represent an essential task in manysectors of industry. Examples of such tasks are e.g. precise alignments of opto-mechanical systems, large objectdeformation measurements, evaluation of object shape, and many others. Today, the standard methodused for such a type of measurements is based on use of Coordinate Measuring Machines (CMMs). Unfortunately,the CMMs have severe shortcomings: low measurement point density, long measurement time,risk of surface damage, etc. Indeed, the measurement time increases rapidly with the object complexity andwith the density of measurement points. In this paper, we have developed a method for surface topographymeasurements called Frequency Sweeping Digital Holography (FSDH). Our developed FSDH method isbased on the principles of Wavelength Scanning Interferometry. It allows surface topography measurementsof objects with diameter of several hundred of mms with a high axial accuracy reaching 10 m. The greatestadvantage of the presented FSDH is the fact that the surface topology data are captured in motionlessmanner by means of a relatively simple setup. This makes the FSDH method a suitable technique fortopography measurements of objects with complex geometries made of common materials (such as metals,plastics, etc.) as well as for the characterization of complex composite structures such as acoustic metamaterials,active acoustic metasurfaces, etc. Measurement method principles, setup details, lateral resolution,and axial accuracy are discussed.

On-chip membrane-based GaInAs/InP waveguide-type p-i-n photodiode fabricated on silicon substrate

Zhichen Gu, Tatsuya Uryu, Nagisa Nakamura, Daisuke Inoue, Tomo Amemiya, Nobu Nishiyama, and Shigehisa Arai

Doc ID: 302766 Received 18 Jul 2017; Accepted 30 Aug 2017; Posted 05 Sep 2017  View: PDF

Abstract: Toward the realization of ultralow-power-consumption on-chip optical interconnection, two types of membrane-based GaInAs/InP p-i-n photodiodes were fabricated on Si host substrates by using benzocyclobutene bonding. A responsivity of 0.95 A/W was estimated with a conventional waveguide-type photodiode with an ~30-μm-long absorption region. The fitting curves based on the experimental data indicated that an absorption efficiency above 90% could be achieved with a length of 10 μm. In addition, increased absorption per length of a photonic crystal waveguide-type photodiode was obtained because of the enhanced lateral optical confinement or the slow-light effect, enabling a further reduction in the device length.

Measurement Of Optical Waveguides Refractive Index Profile By Moiré Deflectometry Technique

Mohammad Ahmadi, Khosro Madanipour, and Soheila Javadian Varjovi

Doc ID: 292506 Received 01 May 2017; Accepted 29 Aug 2017; Posted 29 Aug 2017  View: PDF

Abstract: Measurement of refractive index profile in optical waveguides is an important issue for controlling manufacture procedure and determination of some important characteristics of waveguides. In this paper optical waveguide is considered as a phase object, when collimated laser beams are illuminated on waveguides, refractive index gradient distort plane waves then distortion is determined by use of moiré deflectometry method. Dimensions of the under study waveguides are in order of 10 micron so the Moiré deflectometry set-up was change and optimized for measuring in the micrometer dimension. This modified and generalized moiré deflectometry technique helps to intensify plane wave distortion thousands of times and expand it to be measurable. Finally by analysis of moiré fringes we succeed to determine refractive index profile of an optical waveguide by approximation of semi-cylindrical symmetry.

Off-surface optic axis birefringent filters for smoothtuning of broadband lasers

Umit Demirbas

Doc ID: 300603 Received 20 Jun 2017; Accepted 29 Aug 2017; Posted 29 Aug 2017  View: PDF

Abstract: Transition metal-doped gain media such as Ce:LiCAF, Ti:Sapphire, Cr:ZnSe and Fe:ZnSe possesses wide gainbandwidths that could provide ultra broadly tunable laser output with the usage of adequate intracavity tuningelements. Birefringent filters (BRFs) are a low-cost and easy to use solution for tuning. However, for ultrabroadgain media, regular on-surface optic axis BRFs could not provide smooth tuning of laser wavelength in the wholeemission range. Basically, regular BRFs could not accommodate a large enough free spectral range with acceptablemodulation depth variation while tuning due to their slow tuning rates. Motivated by this, in this study we havenumerically investigated the effect of optic axis orientation on filter parameters for magnesium fluoridebirefringent tuning plates. We have shown that, a magnesium fluoride BRF with an optic axis diving by 30° into theplate could provide smooth tuning of ultra-broad laser gain media. A similar analysis has shown that forbroadband tuning applications the optimum optic axis diving angle lies around 25° for crystal quartz BRFs. Theproposed filters have the potential to be useful in tuning of broadband lasers in continuous-wave, long-pulsed andfemtosecond operation regimes.

Pseudo-Random Masks for Angular Alignment

Cristina Gomez-Sarabia, Luis Ledesma-Carrillo, 3. Cipriano Guzmán-Cano, Miguel Torres-Cisneros, Rafael Guzman, and Jorge Ojeda-Castaneda

Doc ID: 298170 Received 16 Jun 2017; Accepted 29 Aug 2017; Posted 30 Aug 2017  View: PDF

Abstract: We design an alignment technique that employs a pair of masks, with angular segments encoding pseudo random sequences. The pair is used for implementing an angular correlator, which generates high on-axis irradiance values, if the elements of the pair are aligned. Otherwise, the on-axis irradiance decreases to a minimum value. The angular correlator is independent of the lateral magnification. Then, it is useful for testing that zoom systems do not introduce rotations or geometrical distortions, when changing magnification. A merit function describes the sensitivity of the technique, and its tolerance to focus errors. We use linearly polarized films for showing that the technique works well with broad band light.

Variations in the water vapor distribution and the associated effects on fog and haze eventsover Xi’an based on Raman lidar data and back trajectories

yufeng wang, Qiang Fu, Yuehui Song, Huige Di, and Dengxin Hua

Doc ID: 301959 Received 10 Jul 2017; Accepted 25 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: A combination of more than 2 years of water vapor lidar data with back trajectory analysisusing the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model was used tostudy the long-range transport of air masses and the water vapor distribution characteristics andvariations over Xi’an, China (34. 3° N, 108.911° E), which is a typical city in Northwest China.High-quality profiles of the water vapor density were derived from a multifunction Raman lidarsystem built in Xi’an, and more than 2000 sets of profiles with >400 nighttime observations fromOctober 2013 to July 2016 were collected and used for statistical and quantitative analyses.The vertical variations in the water vapor content were discussed. A mutation height of thewater vapor exists at 2-4 km with a high occurrence rate of ~60% during the autumn and winterseasons. This height reflects a distinct stratification in the water vapor content. Additionally, theatmospheric water vapor content was mainly concentrated in the lower troposphere, and theproportion of the water vapor content at 0.5-5 km accounted for 80~90% of the total water vaporbelow 10 km. Obvious seasonal variations were observed, including large water vapor contentsduring the spring and summer and small contents during the autumn and winter. Combined withback trajectory analysis, the results showed that markedly different water vapor transport pathwayscontribute to seasonal variations in the water vapor content. South and southeast airflows dominatedduring the summer with 30% of the 84 trajectories originating from these areas; however, the airmasses during the winter originated from the north and local regions (64.3%) and from thenorthwest (27%).In addition, we discussed variations in the water vapor during fog and haze weather conditionsduring the winter. A considerable enhancement in the mean water vapor density at 0.5-3 kmexhibited a clear positive correlation (correlation coefficient >0.8) with the PM2.5 and PM10concentrations. The results indicate that local airflow trajectories mainly affect water vaportransport below the boundary layer and that these flows are closely related to the formation of fogand haze events in the Xi’an area.

Wavelength and ambient luminance dependence of laser eye dazzle

Craig Williamson, Leon McLin, John Rickman, Michael Manka, Paul Garcia, Wesley Kinerk, and Peter Smith

Doc ID: 301097 Received 20 Jul 2017; Accepted 24 Aug 2017; Posted 08 Sep 2017  View: PDF

Abstract: A series of experiments has been conducted to quantify the effects of laser wavelength and ambient luminance on the severity of laser eye dazzle experienced by human subjects. Eight laser wavelengths in the visible spectrum were used (458 – 647 nm) across a wide range of ambient luminance conditions (0.1 – 10,000 cd·m^-2). Subjects were exposed to laser irradiance levels up to 600 µW·cm^-2 and were asked to recognize the orientation of optotypes at varying eccentricities up to 31.6 degrees of visual angle from the laser axis. More than 40,000 data points were collected from 14 subjects (ages – 64), and these were consolidated into a series of obscuration angles for comparison to a theoretical model of laser eye dazzle. Scaling functions were derived to allow the model to predict the effects of laser dazzle on vision more accurately by including the effects of ambient luminance and laser wavelength. The updated model provides an improved match to observed laser eye dazzle effects across the full range of conditions assessed. The resulting model will find use in a variety of laser safety applications, including the estimation of Maximum Dazzle Exposure (MDE) and Nominal Ocular Dazzle Distance (NODD) values.

Geometrical optical transfer function: Is it worthcalculating?

Jose Antonio Diaz-Navas and Virendra Mahajan

Doc ID: 303582 Received 28 Jul 2017; Accepted 23 Aug 2017; Posted 06 Sep 2017  View: PDF

Abstract: In this paper, we explore the merit of calculating the geometrical optical transfer function (GOTF) in optical designby comparing the time to calculate it with the time to calculate the diffraction optical transfer function (DOTF). Wedetermine the DOTF by numerical integration of the pupil function autocorrelation (that reduces to an integrationof a complex exponential of the aberration difference function), 2D digital autocorrelation of the pupil function,and by the Fourier transform (FT) of the point-spread function (PSF); and the GOTF by the FT of the geometricalPSF (that reduces to an integration over the pupil plane of a complex exponential that is a scalar product of thespatial frequency and transverse ray aberration vectors), and by a FT of the spot diagram. Our starting point forcalculating the DOTF is the wave aberrations of the system in its pupil plane, and the transvers ray aberrations inthe image plane for the GOTF. Numerical results for primary aberrations and some typical imaging systems showthat the direct numerical integrations are slow, but the GOTF calculation by a FT of the spot diagram is two or eventhree times slower than the DOTF calculation by a FT of the PSF, depending on the aberration. We conclude that thecalculation of GOTF, that is at best an approximation of the DOTF and that too for only large aberrations, does notoffer any advantage in the optical design process, and hence negates its utility.

Suomi NPP VIIRS solar diffuser screen transmittance model and its applications

Ning Lei, Xiaoxiong Xiong, and Jeff McIntire

Doc ID: 296116 Received 16 May 2017; Accepted 17 Aug 2017; Posted 17 Aug 2017  View: PDF

Abstract: The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership satellitecalibrates its reflective solar bands through observations of a sunlit solar diffuser (SD) panel. Sunlight passesthrough a perforated plate, referred to as the SD screen, before reaching the SD. It is critical to know whether theSD screen transmittance measured prelaunch is accurate. Several factors such as misalignments of the SD paneland the measurement apparatus could lead to errors in the measured transmittance and thus adversely impact onorbitcalibration quality through the SD. We develop a mathematical model to describe the transmittance as afunction of the angles that incident light makes with the SD screen, and apply the model to fit the prelaunchmeasured transmittance. The results reveal that the model does not reproduce the measured transmittance unlessthe size of the apertures in the SD screen is quite different from the design value. We attribute the difference to theorientation alignment errors for the SD panel and the measurement apparatus. We model the alignment errors andapply our transmittance model to fit the prelaunch transmittance to retrieve the “true” transmittance. To use thismodel correctly, we also examine the finite source size effect on the transmittance. Furthermore, we compare theproduct of the retrieved “true” transmittance and the prelaunch SD BRDF value to the value derived from on-orbitdata to determine whether the prelaunch SD BRDF value is relatively accurate. The model is significant in that itcan evaluate whether the SD screen transmittance measured prelaunch is accurate and help retrieve the truetransmittance from the transmittance with measurement errors, consequently resulting a more accurate sensordata product by the same amount.

Three-dimensional image acquisition and reconstruction system on mobile device based on computer-generated integral imaging

Munkh-Uchral Erdenebat, Byeong-Jun Kim, Yan-Ling Piao, Seo-Yeon Park, Ki-Chul Kwon, Mei-Lan Piao, Kwan-Hee Yoo, and Nam Kim

Doc ID: 301032 Received 27 Jun 2017; Accepted 09 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: A mobile three-dimensional image acquisition and reconstruction system using computer-generated integral imaging technique is proposed. A depth camera connected to the mobile device acquires the color and depth data of a real object simultaneously, and an elemental image array is generated based on the original three-dimensional information for the object, with lens array specifications input into the mobile device. The three-dimensional visualization of the real object is reconstructed on the mobile display through optical or digital reconstruction methods. The proposed system is implemented successfully and the experimental results certify that the system is an effective and interesting method of displaying real three-dimensional content on a mobile device.

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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