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Deep Learning enhancement of infarerd face images using Generative Adversarial Networks

Axel Guei and Moulay Akhloufi

Doc ID: 318283 Received 21 Dec 2017; Accepted 16 Mar 2018; Posted 16 Mar 2018  View: PDF

Abstract: This work presents a deep learning framework based on the use of Deep Convolutional Generative Adversarial Networks (DCGAN) for infrared face image super-resolution. We use DCGAN for upscaling the images by a factor of 4x4, starting at a size of 16x16 and obtaining a 64x64 face image. Tests are conducted using different infrared face datasets operating in the near infrared (NIR) and the long wave infrared (LWIR) spectrum. We can see that the proposed framework performs well and preserves important details of the face. This kind of approach can be very useful in security applications where we can scan faces in the crowd or detect faces at a distance and upscale them for further recognition through an infrared or a multispectral face recognition systems.

The Double Donut Schmidt Camera, a wide field, largeaperture and light weight space telescope for thedetection of ultra-high energy cosmic rays

Paolo Sandri, Piero Mazzinghi, and Vania Da Deppo

Doc ID: 320049 Received 18 Jan 2018; Accepted 16 Mar 2018; Posted 16 Mar 2018  View: PDF

Abstract: A wide field, large aperture and lightweight Schmidt configuration has been studied for a space mission proposalnamed Extreme Universe Space Observatory Free Flyer (EUSO-FF). EUSO-FF will be devoted to the study of ultrahighenergy cosmic rays, i.e. with energy > 5×1019 eV, through the detection of UV fluorescence light emitted by airshowers in the Earth’s atmosphere. The proposed telescope has a field of view of about 50° and an entrance pupildiameter of 4.2 m. The mirror is deployable and segmented to fit the diameter of the launcher fairing; the correctoris a lightweight annular corona.

Silicon Microsphere Whispering Gallery Modes excitedby Femtosecond Laser Inscribed Glass Waveguides

Huseyin Cirkinoglu, Mustafa Bayer, Ulas Gokay, Ali Serpenguzel, Belen Sotillo, Vibhav Bharadwaj, Roberta Ramponi, and Shane Eaton

Doc ID: 319727 Received 17 Jan 2018; Accepted 15 Mar 2018; Posted 16 Mar 2018  View: PDF

Abstract: We report on coupling to the 500 μm radius silicon microsphere whispering gallery modes by a femtosecond laserinscribed glass optical waveguide. The shallow glass waveguide with a large mode field diameter in the nearinfraredis written at a depth of 25 μm below the glass surface, resulting in a high excitation impact parameter of525 μm for the microsphere. The excited whispering gallery modes of the silicon microsphere have quality factorsof approximately 105 in the 90° elastic scattering and the 0° transmission. The integration of such spherical siliconmicroresonators on femtosecond-laser inscribed glass waveguides is promising for photonic communication,computation, and sensing applications.

Spectral Monte Carlo Simulation of Collimated SolarIrradiation Transfer in A Water-Filled Prismatic Louver

Zhixiong Guo and Yaomin Cai

Doc ID: 322830 Received 09 Feb 2018; Accepted 15 Mar 2018; Posted 16 Mar 2018  View: PDF

Abstract: A Monte Carlo model was developed to simulate collimated solar irradiation transfer and energy harvest in ahollow louver made of silica glass and filled with water. The full solar spectrum of air mass 1.5 database wasadopted and divided into various discrete bands for spectral calculations. The band-averaged spectral propertiesfor the silica glass and water were obtained. Ray tracing was employed to find the solar energy harvested by thelouver. Computational efficiency and accuracy were examined through intensive comparisons of different bandpartition approaches, various photon numbers and element divisions. The influence of irradiation direction onsolar energy harvest efficiency was scrutinized. It was found that within 15°polar angle of incidence the harvestedsolar energy in the louver was high, and the total absorption efficiency reached to 61.2% under normal incidencefor the current louver geometry.

Lock-in and pulsed thermography for solar cells testing

Lukáš Muzika, Michal Svantner, and Martin Kučera

Doc ID: 319849 Received 17 Jan 2018; Accepted 15 Mar 2018; Posted 15 Mar 2018  View: PDF

Abstract: Inspection of solar cells is an important part of their production process, because even their small defects can cause a significant drop of a whole photo-voltaic module performance. LED illuminated lock-in (LEDILIT) and flash-pulse (FPT) thermographic techniques were compared in this study. Lock-in methods are more commonly used for solar cells inspection. The aim of the study was to find out if the FPT is appropriate for an inspection of defects of multicrystalline solar cells. Experimental setup, inspection results and advantages/disadvantages of both methods are presented. It was confirmed that the LEDILIT produced more clear indications. The FPT was not so efficient, but it was much faster and could detect many of defects also indicated by LEDILIT. FPT also indicated inhomogeneities at a bottom layer of a cell, which were not connected with a photo-voltaic effect and which were not revealed by LEDILIT.

Thin films based optical fiber Fabry-Perot interferometer used for humidity sensing

Jiankun Peng, Yapeng Qu, Weijia Wang, Tengpeng Sun, and Minghong Yang

Doc ID: 320579 Received 26 Jan 2018; Accepted 15 Mar 2018; Posted 15 Mar 2018  View: PDF

Abstract: Thin films based optical fiber Fabry-Perot interferometer which consists of ZrO2 and SiO2 porous thin films is designed and fabricated by electron beam physical vapor deposition. Since the SiO2 porous thin film has the capability of water adsorption, the proposed Fabry-Perot interferometer is appropriate to detect humidity. Experimental results show the prepared sensor has a humidity detection range from 0.06%RH to 70%RH. Cycling test shows that the humidity sensor has a sensing or recover time of 4 s and good repeatability between different humidity environments. Especially, the proposed humidity sensor is suitable for the detection of low relative humidity.

Temperature-dependent optical constants of liquid isopropanol, n-butanol and n-decane

Wang Chengchao, Jianyu Tan, chaoyu jing, and Lin Hua Liu

Doc ID: 321201 Received 31 Jan 2018; Accepted 14 Mar 2018; Posted 15 Mar 2018  View: PDF

Abstract: Liquid isopropanol, n-butanol and n-decane are combustible organic compounds that are frequently used intheoretical and experimental researches on fuel combustion. In this work, the temperature-dependent opticalconstants of liquid isopropanol, n-butanol and n-decane in the region 500-5500 cm−1 at ambient pressure aremeasured using the combined ellipsometry-transmission method. In the combined method, the optical constantsare firstly measured by a modified ellipsometry method, and then the absorption indices for weak absorptionregions are obtained by the transmission method using the refractive indices measured by the modifiedellipsometry method. The refractive indices of liquid isopropanol, n-butanol and n-decane are within the rangefrom 1.3 to 1.45 in the studied wavelength and temperature region. The absorption indices of these liquids rangefrom 10–5 to 10–1. In the temperature range studied, the refractive indices decrease with increasing temperature inan approximately linear manner, but the effects of the temperature on the absorption indices are much smaller.The characteristic wavenumbers of the main absorption peaks are consistent with the vibrational frequencies ofmajor functional groups.

Optimised robotic set-up for automated activethermography using advanced path planning andvisibility study

Jeroen Peeters, Boris Bogaerts, Seppe Sels, Bart Ribbens, Joris Dirckx, and Gunther Steenackers

Doc ID: 318171 Received 20 Dec 2017; Accepted 14 Mar 2018; Posted 15 Mar 2018  View: PDF

Abstract: In-line inspection of advanced components remains a challenging task in industry. The authors will describean automated methodology which uses numerical simulations to automatically determine the bestset of experimental parameters to inspect the structure on defects using active thermography. The inspectionis performed using a robotic arm and advanced path planning tools to determine the optimal positionsof the measurement points and excitation points. During the path planning, the directional emissivityis considered for the complex surface and a minimisation of the amount of measurement points isperformed. The numerical simulation optimisation used a genetic algorithm and spline regression modelto optimise the heat power, robot speed, camera frame rate and excitation timing to fulfil the automaticinspection.

Characterization of aerosol optical properties usingmultiple clustering techniques over Zanjan, Iran,during 2010-2013

Maryam Gharibzadeh, Khan Alam, Yousefali Abedini, Abbasali Aliakbari Bidokhti, Amir Masoumi, and Humera Bibi

Doc ID: 319161 Received 08 Jan 2018; Accepted 14 Mar 2018; Posted 15 Mar 2018  View: PDF

Abstract: Discrimination of aerosol types is very important because different aerosols are created from diverse sources whichare having different chemical, physical and optical properties. In the present study, we have analyzed seasonalclassification of aerosol types by multiple clustering techniques, using AERosol Robotic NETwork (AERONET) dataduring 2010-2013 over Zanjan, Iran. We found that Aerosol Optical Depth (AOD) showed pronounced seasonalvariations of summer high and winter low. Conversely, the values of Angstrom Exponent (AE) in winter and fall werehigher than spring and summer, which confirmed the presence of fine particles, while the low value of AE in the summerand spring representing the existence of coarse particles. Single Scattering Albedo (SSA) variations revealed thepresence of scattering aerosols like dust in spring, summer and fall while the dominance of absorbing type aerosols inwinter were also observed. The influence of local anthropogenic activities has caused higher concentration of fineaerosols and higher Fine Mode Fraction (FMF) of AOD in winter was recorded. Classification of aerosol types wascarried out by analyzing different aerosol properties such as AOD versus AE, Extinction Angstrom Exponent (EAE)versus SSA, EAE versus Absorption Angstrom Exponent (AAE), FMF AOD versus EAE, and SSA versus FMF AOD. Theanalysis revealed the presence of dust and polluted dust in spring, summer and fall in the atmosphere of Zanjan.Urban/Industrial aerosols were available in all seasons, especially in fall and winter. The mixed aerosols existed in allseasons over the study location, however, no biomass burning aerosols were found. The Cloud-Aerosol Lidar andInfrared Pathfinder Satellite Observations (CALIPSO) aerosol subtype profiles showed the dominance of dust andpolluted dust in spring and summer. However, the presence of polluted dust and industrial smoke during fall and winterwere also noted over the study site.

KW-level 1030 nm polarization maintained fiber laserwith narrow linewidth and near-diffraction-limited beamquality

Chu Chu, Pengfei Zhao, Yu Liu, Chengyu Li, Bopeng Wang, Chao Guo, Honghuan Lin, Xuan Tang, Chuanxiang Tang, and Feng Jing

Doc ID: 319427 Received 09 Jan 2018; Accepted 13 Mar 2018; Posted 15 Mar 2018  View: PDF

Abstract: KW-level 1030-nm polarization maintained fiber laser with narrow linewidth and near-diffraction-limitedbeam quality is demonstrated. Theoretical simulations based on power balanced equation are first performedto optimize the system parameters of 1030 nm ytterbium-doped fiber laser for the maximum suppressionof amplified spontaneous emission (ASE). With the optimized parameters, both of co-pumpedand counter-pumped MOPA lasers are implemented to obtain output power >1 kW. In both cases, theASE suppression ratio reaches 40 dB with 3 dB linewidth about 0.14 nm, and the polarization extinctionratio (PER) is about 12 dB at 1 kW of output power. The beam quality starts degrading at 900Wof outputpower in the co-pumped structure, but maintains nearly single mode (M2x,M2y) = (1.07,1.12) till power over1 kW in the counter-pumped structure.

Wavelength-dependent excess permittivity as indicator ofkerosene in diesel oil

Boniphace Kanyathare and Kai Peiponen

Doc ID: 321102 Received 30 Jan 2018; Accepted 13 Mar 2018; Posted 15 Mar 2018  View: PDF

Abstract: Adulteration of diesel oil by kerosene is a serious problem because of air pollution resulting from car exhaustgases. The objective of this study was to develop a relatively simple optical measurement and data analysismethod to screen low adulterated diesel oils. For this purpose, we introduce the utilization of refractive indexmeasurement with a refractometer, scanning of Vis- NIR transmittance, transmittance data inversion usingsingly-subtractive Kramers-Kronig relation, and exploitation of so-called wavelength-dependent relative excesspermittivity. It is shown for three different diesel oil grades, adulterated with kerosene, that the excesspermittivity is a powerful measure for screening fake diesel oils. The excess relative permittivity of such binarymixtures also reveals hidden spectral fingerprints which are neither visible in dispersion data alone nor inspectral transmittance measurements alone. We believe that the excess permittivity data is useful in case ofscreening adulteration of diesel oil by kerosene and can further be explored for practical sensing solutions, forinstance in quality inspection of diesel oils in refineries.

Frequency stability of pulsed optically pumped atomicclock with narrow Ramsey linewidth

Haixiao Lin, Jianliao Deng, Jinda Lin, Song Zhang, and Yu-zhu Wang

Doc ID: 315232 Received 08 Dec 2017; Accepted 13 Mar 2018; Posted 14 Mar 2018  View: PDF

Abstract: In general, the linewidth of the Ramsey central fringe (RCF) is equal to 1/(2T), where T is the Ramsey freeevolutiontime. We demonstrate that the RCF linewidth of a pulsed optically pumped (POP) atomic clock withorthogonal polarization detection based on the magneto-optical rotation effect can be narrowed down to 1/(4T).The Allan deviation of the POP atomic clock decreases from 2.4 × 10−13 τ-1/2 to 1.4 × 10−13 τ-1/2. This corresponds toan improvement in the frequency stability by about 60%. We also estimate the main noise sources that limit theshort-term frequency stability of the POP atomic clock.

Analysis of the influence of Installation Tilt Error on the Tool Setting Accuracy by Laser Diffraction

Guangfeng Shi, Yushi Zhang, Hua Zhang, Jinyu Wang, and Guoquan Shi

Doc ID: 319475 Received 11 Jan 2018; Accepted 13 Mar 2018; Posted 14 Mar 2018  View: PDF

Abstract: In the ultra-precision machining process, it is an important way to detect the tool-workpiece distance by laser diffraction effect. However, there is no absolute ideal situation for the tool setting of laser diffraction. It is necessary to consider the influence of installation tilt error on the tool setting accuracy and compensation. In this paper, refer to the ideal optical axis, the influences of the incident laser tilt, CCD tilt and rectangular orifice tilt on the peak position of the diffraction fringes in the CCD phase are modeled and analyzed to determine the relative effects on the tool setting accuracy for tool-workpiece distance detection. The tilt angle of the incident laser is measured by extracting the CCD pixel position where the central peak point is located. The CCD tilt angle is detected by extracting the CCD pixel position where the first-degree peak point is located. The inclination direction and the inclination angle of the rectangular orifice are detected by extracting the bending direction and the bending degree of the fringes in the horizontal direction, and the error compensation is performed according to the inclination angle. This paper establishes a compensation method for the installing tilt error, and the optimized installation process parameters can be obtained under certain experimental conditions according to the experimental data to ensure the result accuracy.

Pedestal-free 25-GHz subpicosecond optical pulsesource for 16 × 25-Gb/s OTDM based on phasemodulation and dual-stage nonlinear compression

Dong Wang, Li Huo, YUNBO LI, dechao zhang, lei wang, han li, Xiangyu Jiang, and Caiyun Lou

Doc ID: 321234 Received 01 Feb 2018; Accepted 13 Mar 2018; Posted 14 Mar 2018  View: PDF

Abstract: Optical pulse generation scheme based on an ultra-short chirped seed pulse generator followed by a dual-stagefiber-based nonlinear pulse processing stage is proposed and demonstrated experimentally. After phasemodulation and linear-chirp compensation, optical seed pulse with a duty cycle of 9.8 % and an obvious pedestal isobtained. By soliton compression and Mamyshev reshaping, pedestal-free optical pulse with a duty cycle of 2 % andan extinction ratio of 27 dB is achieved. The optical pulse source is further applied in a 16 × 25-Gb/s on-off keyingoptical time-division multiplexing (OTDM) transmitter.

Measurement accuracy of FBG used as surface-bondedstrain sensor installed by adhesive

Guangzhe Xue, Xinqiu Fang, Xiukun Hu, and Libin Gong

Doc ID: 315171 Received 08 Dec 2017; Accepted 12 Mar 2018; Posted 15 Mar 2018  View: PDF

Abstract: Material and dimensional properties of surface-bonded FBGs can distort strain measurement, thereby lowering themeasurement accuracy. To accurately assess measurement precision and correct obtained strain, a new model,considering reinforcement effects on adhesive and measured object, is proposed in this study, which is verified tobe accurate enough by numerical method. Meanwhile, a theoretical strain correction factor is obtained, which isdemonstrated to be significantly sensitive to recoating material and bonding length as suggested by numerical andexperimental results. It is also concluded that short grating length as well as thin but large-area (preferablycovering the whole FBG) adhesive can enhance the correction precision.

High-Speed Flame Chemiluminescence Imaging UsingTime-Multiplexed Structured Detection

Mark GRAGSTON, Cary Smith, and zhili zhang

Doc ID: 315200 Received 07 Dec 2017; Accepted 12 Mar 2018; Posted 15 Mar 2018  View: PDF

Abstract: In this work, high-speed flame chemiluminescence has been obtained by using Time Multiplexed StructuredDetection (TMSD) imaging method from a single snapshot. TMSD sheers the time lapse into the spatial frequencyshifts, which allows multiple high-speed images to be frequency upshifted into distinct spatial frequency regionsfrom the original image. A cumulative exposure captured in a single snapshot image contains distinct timeevolution. Each distinct image is demultiplexed and recovered by hyperdyne mixing with the modulationfrequency. TMSD is an optical frequency domain analog to carrier frequency modulation in radio and microwavedetections. Specifically, a Digital Micromirror Device (DMD) spatially modulates flame chemiluminescence justprior to the camera. Spatial frequency of each distinct image is mixed between the original spatial frequencycomponents and DMD modulation pattern frequency, resulting in a coded snapshot. The high-speed flamechemiluminescence image is recovered by demodulation. TMSD is similar to Structured Illumination (SI) used insuper resolution microscopy, but offers more advantages for it does not alternate incident illumination light. SinceDMDs are available with speeds up to 40 kHz, this technique shows promise as a cost-effective means of high-speedimaging and diagnostics of combustion phenomena.

Evaluation of sea-surface Photosynthetically Available Radiation (PAR) algorithms under various sky conditions and solar elevations

Ayyala Somayajula Srikanth, Emmanuel Devred, Simon Belanger, David Antoine, Vincenzo Vellucci, and Marcel Babin

Doc ID: 320247 Received 19 Jan 2018; Accepted 12 Mar 2018; Posted 14 Mar 2018  View: PDF

Abstract: In this study, we report on the performance of satellite-based PAR algorithms used in published oceanic primaryproduction models. The performance of these algorithms was evaluated using buoy observations under clear andcloudy skies, and for the particular case of low sun angles typically encountered at high latitudes or at moderatelatitudes in winter. The PAR models consisted of i) the standard one from the NASA-Ocean Biology ProcessingGroup (OBPG), ii) Gregg and Carder (GC) semi-analytical clear sky model and iii) look-up-tables based on the SantaBarbara DISORT Atmospheric Radiative Transfer (SBDART) model. Various combinations of atmospheric inputs,empirical cloud corrections and semi-analytical irradiance models yielded a total of 13 (11 + 2 developed in thisstudy) different PAR products, which were compared with in situ measurements collected at high frequency (15min) at a buoy site in the Mediterranean Sea (BOUSSOLE site). An objective ranking method applied to thealgorithm results indicated that seven PAR products out of thirteen were well in agreement with the in situmeasurements. Specifically, the OBPG method showed the best overall performance with a root mean squaredifference (bias) of 19.7% (6.6%) and 10% (6.3%) followed by the look-up-table method with RMSD (bias) of25.5% (6.8%) and 9.6% (2.6 %) at daily and monthly scales, respectively. Among the four methods based on clearskyPAR empirically corrected for cloud cover, Dobson and Smith method consistently underestimated daily PARwhile the Budyko formulation overestimated daily PAR. Empirically cloud corrected methods using CF performedbetter under quasi-clear skies (Cloud Fraction, CF, < 0.3) with a RMSD (bias) of 9.7-14.8% (3.6 to 11.3%) thanunder partially clear to cloudy skies (0.3 < CF <0.7) with 16.1 to 21.2% (-2.2 to 8.8%). Under complete overcastconditions (CF > 0.7), however, all methods showed larger RMS differences (biases) ranging between 32 and 80.6%(-54.5 to 8.7%). Finally, three methods tested for low sun elevations revealed systematic overestimation and onemethod showed a systematic underestimation of daily PAR under, with relative RMSDs as large as 50% under allsky conditions. Under partially clear to overcast conditions all the methods underestimated PAR. Modeluncertainties predominantly depend on which cloud products were used.

Development of an inverse distance weighted active IR stealth scheme using the RPSO algorithm

Kuk-Il Han, Do-Hwi Kim, Jun-Hyuk Choi, and Tea-Kuk Kim

Doc ID: 309209 Received 30 Oct 2017; Accepted 12 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: Treats for the detection by infrared signals are higher than other signals such as radar or sonar because an object detected by the infrared sensor cannot easily recognize its detection status. Recently, research for actively reducing infrared signal has been conducted to control the infrared signal by adjusting the surface temperature of the object. In this paper, we propose an active IR stealth algorithm to synchronize IR signals from the object and the background around the object. The proposed method includes the RPSO statistical optimization algorithm to estimate the infrared stealth surface temperature which will result in a synchronization between the IR signals from the object and the surrounding background by setting the inverse distance weighted CRI equal to zero. We tested the IR stealth performance in MWIR and LWIR bands for a test plate located at three different positions on a forest scene to verify the proposed method. Our results show that the inverse distance weighted active IR stealth technique proposed in this study is proved to be an effective method for reducing the contrast radiant intensity between the object and background up to 32% as compared to the previous method using the CRI determined as the simple signal difference between the object and the background.

A hybrid method to estimate two-layered superficial tissue optical properties from simulated data of diffuse reflectance spectroscopy

Hong-Po Hsieh, Fan-Hua Ko, and Kung-Bin Sung

Doc ID: 313973 Received 27 Nov 2017; Accepted 12 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: An iterative curve fitting method has been applied in both simulation (doi: 10.1117/1.JBO.17.10.107003) and phantom (doi: 10.1117/1.JBO.19.7.077002) studies to accurately extract optical properties and the top layer thickness of a two-layered superficial tissue model from diffuse reflectance spectroscopy (DRS) data. This manuscript describes a hybrid two-step parameter estimation procedure to address two main issues of the previous method, including 1) high computational intensity and 2) converging to local minima. The parameter estimation procedure contained a novel initial estimation step to obtain an initial guess which was used by a subsequent iterative fitting step to optimize the parameter estimation. A look-up table was used in both steps to quickly obtain reflectance spectra and reduce computational intensity. On simulated DRS data the proposed parameter estimation procedure achieved high estimation accuracy and a 95% reduction of computational time compared to previous studies. Furthermore, the proposed initial estimation step led to better convergence of the following fitting step. Strategies used in the proposed procedure could benefit both the modeling and experimental data processing of not only DRS but also related approaches such as near-infrared spectroscopy.

Emissivity determination using the photoacoustic effect

Yaqi Zhang and Gerald Diebold

Doc ID: 315718 Received 15 Dec 2017; Accepted 12 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: We show that emissivities in the near infrared canbe determined relative to a reference surface employingthe photoacoustic effect. The photoacoustic cellis equipped with two windows and a pair of synchronouslymoving chopping wheels so that the cellviews alternately the test and the reference surface. Theacoustic signals produced in the cell are detected witha microphone whose output is fed to a lock-in amplifier.The temperature of the test surface is varied toproduce a null in the lock-in amplifier, which permitsdetermination of a relative emissivity. Results of measurementsfor several plastic and metal surfaces are reported.

Focus shaping by tailoring arbitrary hybridpolarization states that have a combination oforthogonal linear polarization bases

Zhongsheng Man, Bai Zhidong, jinjian li, shuoshuo zhang, Li Xiaoyu, Ge Xiaolu, and fu Shenggui

Doc ID: 318193 Received 20 Dec 2017; Accepted 12 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: We report a focus shaping method by tailoring hybrid states of polarization of arbitrary polarized beams that havea combination of orthogonal linear polarization bases. Such hybridly polarized beams, comprising linear, elliptical,and circular polarizations in the beam cross-section, have completely different optical properties compared to thescalar and locally-linear polarized vector beams. We demonstrate that apart from orientation of local polarizationstate, another two degrees of freedom, including the local ellipticity and the handedness in the beam cross-sectioncan be used in focus shaping. Square-shaped patterns, multiple foci, three-dimensional optical cages, opticalneedles, and channels can be obtained due to the increased control, without any additional phase or amplitudemodulations.

KTN Based High Speed Axial and Lateral ScanningTechnique for Optical Coherence Tomography Systemand Application to Dental Imaging

Vani Damodaran, Nilesh Vasa, and R Sarathi

Doc ID: 318296 Received 21 Dec 2017; Accepted 12 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: A high-speed 840 nm based polarisation sensitive time domain optical coherence tomography (PSOCT) techniqueis proposed and demonstrated based on the quadratic electro-optic property of Potassium Tantalate Niobate (KTN)crystals. A longitudinal (axial) scanning depth of ≈10 μm is obtained for an applied AC voltage of 600 V, at 1000 Hzand temperature maintained around 40 °C. The OCT system with the KTN based electro-optic delay line combinedwith a linear actuation is extended to image an early dental demineralisation. For enhanced contrast by theelimination of the strong surface reflection from the sample and high speed imaging, the quadratic electro-opticallytunable PSOCT technique is proposed and demonstrated. Further, a lateral scanning range of 490 μm is alsodemonstrated by controlling the KTN temperature at 35 °C for an applied voltage of 600 V on the tooth sample. ThisKTN based quadratic electro-optic delay line combined with lateral scan approach provides an automated highspeed two-dimensional scanning of samples of interest.

Substrate aberration and correction for meta-lensimaging: an analytical approach

Benedikt Groever, Charles Roques-Carmes, Steven Byrnes, and Federico Capasso

Doc ID: 318972 Received 25 Jan 2018; Accepted 12 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: Meta-lenses based on flat optics enabled a fundamental shift in lens production - providing an easiermanufacturing process with an increase in lens profile precision and a reduction in size and weight. Herewe present an analytical approach to correct spherical aberrations caused by light propagation through thesubstrate by adding a substrate-corrected phase profile which differs from the original hyperbolic one. Ameta-lens encoding the new phase profile would yield diffraction-limited focusing and an increase of itsnumerical aperture of up to 0.3 without changing the radius or the focal length. In tightly-focused laserspot applications such as direct laser lithography and laser printing a substrate-corrected meta-lens canreduce the spatial footprint of the meta-lens.

Lensless Light-Field Imaging with Fresnel ZoneAperture: Quasi-Coherent Coding

Takeshi Shimano, YUSUKE NAKAMURA, Kazuyuki Tajima, Mayu Sao, and Taku Hoshizawa

Doc ID: 319103 Received 05 Jan 2018; Accepted 12 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: We propose a new type of lens-less cameras enabling light-field imaging for focusing after image capturingtogether with showing its feasibilities with some prototyping. The camera basically consists only of an imagesensor and Fresnel zone aperture (FZA). Point sources making up the subjects to be captured cast overlappingshadows of the FZA on the sensor, which result in overlapping straight moiré fringes due to multiplication ofanother virtual FZA in the computer. The fringes generate a captured image by two-dimensional fast Fouriertransform. Refocusing is possible by adjusting the size of the virtual FZA. We found this imaging principle is quiteanalogous to a coherent hologram. Not only the functions of still cameras but also of video cameras are confirmedexperimentally by using the proto-typed cameras.

Assessment and removal of additive noise in complexOCT signal based on Doppler variation analysis

Xuan Liu, farzana zaki, and Dylan Renaud

Doc ID: 319301 Received 08 Jan 2018; Accepted 12 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: In this study, we investigate and validate a novel approach to assess and remove additive noise for opticalcoherence tomography (OCT) imaging. Our method first generates a map of additive noise for the OCT image throughDoppler variation analysis. We then remove the additive noise from the real and imaginary parts of the complex OCT signalthrough pixel-wise Wiener filtering. Our results show that the method described in this manuscript improves the sensitivityof OCT imaging and preserves the spatial resolution, without the need to modify the imaging apparatus and data acquisitionprotocol.

Improving the Spatial Resolution of Volume BraggGrating Two-Dimensional Monochromatic Images

Jiazhu Duan, Zhao Xiangjie, yongquan luo, and Dayong Zhang

Doc ID: 320113 Received 19 Jan 2018; Accepted 12 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: Higher spatial resolution indicates sharper recognition ability in applications. To improve the spatial resolution ofvolume Bragg grating (VBG) spectral imagers, quantitative wave vector theory is used to elucidate the formationmechanism of diffraction blur, and the corresponding optimal design approaches are put forward. The simulationresults show that the main factors for the spectral image blur are the chromatic blur and diffraction aberration,while the central wavelength deviation further deteriorates these. To deal with these factors, one must optimizethe grating period, thickness, slant angle and refractive index, as well as compress the divergence angle of theincident beam. After optimization under the guidance of the newly defined integrated merit functions, theexperimental results show that the optimized smeared point-spread-function is reduced by about an order ofmagnitude. The horizontal spatial resolution of the recorded two-dimensional monochromatic images is improvedto 14.3 lines/mm under diffuse reflection illumination.

Wideband infrared trap detector based upon dopedsilicon photocurrent devices

Solomon Woods, James Proctor, Timothy Jung, Adriaan Carter, Jorge Neira, and Dana Defibaugh

Doc ID: 320346 Received 22 Jan 2018; Accepted 12 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: We have designed, fabricated and measured infrared trap detectors made from arsenic-doped silicon (Si:As)blocked impurity band (BIB) photodetectors. These trap detectors are composed of two detectors in a wedgegeometry, with an entrance aperture diameter of either 1 mm or 3 mm. The detectors were calibrated for quantumefficiency against a pyroelectric reference detector using a Fourier transform spectral comparator system, andetalon effects and spatial uniformity of the traps were also quantified. Measurements of the traps at a temperatureof 10 K show that nearly ideal external quantum efficiency (> 90 %) can be attained over much of the range from4 μm to 24 μm, with significant responsivity from 2 μm to 30 μm. The traps exhibited maximum etalon oscillationsof only 2 %, about 10 times smaller amplitude than those of the single Si:As BIB detectors measured under similarconditions. Spatial non-uniformity across the entrance apertures of the traps was about 1 %. The combination ofhigh detectivity, wideband wavelength coverage, spectral flatness, and spatial uniformity make these trapdetectors an excellent reference detector for spectrally-resolved measurements and radiometric calibrations overthe near- to far-infrared wavelength range.

Channel correlation and BER performance analysis of coherent optical communication systems with receive diversity over moderate-to-strong non-Kolmogorov turbulence

Yulong Fu, Jing Ma, Liying Tan, Siyuan Yu, and GaoYuan Lu

Doc ID: 315394 Received 12 Dec 2017; Accepted 11 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: In this paper, the new expressions of the channel correlation coefficient and its components (the large-scale and small-scale channel correlation coefficients) for a plane wave are derived for horizontal link in moderate-to-strong non-Kolmogorov turbulence, by using a generalized effective atmospheric spectrum which includes finite turbulence inner and outer scales and high wave number "bump". The closed-form expression of the average bit-error-rate (BER) of the coherent free space optical communication system is derived, by using the derived channel correlation coefficients and an α-μ distribution to approximate the sum of the square root of arbitrarily correlated Gamma-Gamma random variables. Analytical results are provided to investigate the channel correlation and evaluate the average BER performance. The validity of the proposed approximation is illustrated by Monte Carlo simulations. This work will help with the further investigation on the fading correlation in the spatial diversity systems.

Effect of electron avalanche breakdown on highpuritysemi-insulating 4H-SiC photoconductivesemiconductor switch under intrinsic absorption

Longfei Xiao, xianglong yang, Peng Duan, Huanyong Xu, Xiufang Chen, Xiao Hu, Yan Peng, and Xiangang Xu

Doc ID: 320615 Received 25 Jan 2018; Accepted 09 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: High-power photoconductive semiconductor switching devices were fabricated from a high-purity semi-insulating4H-SiC wafer. A highly n-doped GaN subcontact layer was inserted between the contact metal and the highresistivitySiC wafer. The minimum ON-state resistance of the device was less than one ohm when the energy of355nm laser was 10.5 mJ with a bias voltage of 6 kV. The maximum device lifetime is 3151 pulses which the devicefail completely. The failure mechanisms are determined using several analysis methods. Under a strong electricfield, the failure mechanism differs for the two electrodes. Near the edge of the anode electrode, the switch isdamaged due to the thermal stress caused by impact ionization. At the edge of the cathode electrode, the electrodeerosion is the main reason for the failure to operate for long periods of time. These two different damagemechanisms are both important factors influencing the device performance. The electron avalanche breakdown atthe edge of the anode electrode causes the formation of cracks between the electrodes; this is the root cause of theswitch failure.

Compensating additional optical power in the centralzone of multifocal contact lens for minimization ofshrinkage error of shell mold in injection moldingprocess

Lien Vu, Chao-Chang Chen, Cheng Lee, and Wei Yu

Doc ID: 318862 Received 03 Jan 2018; Accepted 09 Mar 2018; Posted 15 Mar 2018  View: PDF

Abstract: This study aims to develop a compensating method to minimize the shrinkage error of the shell mold (SM) ininjection molding (IM) process to obtain a uniform optical power in the central optical zone of soft axial symmetricmultifocal contact lens (CL). The Z-shrinkage error along the Z-axis or axial axis of the anterior SM correspondingto the anterior surface of dry contact lens in IM process can be minimized by optimizing IM process parameters andthen compensating additional (Add) powers in the central zone of the original lens design. First, the shrinkageerror is minimized by optimizing three levels of four IM parameters including mold temperature, injection velocity,packing pressure and cooling time in eighteen IM simulations based on an orthogonal array L18 (2134). Then,based on the Z-shrinkage error from IM simulation, three new contact lens designs are obtained by increasing theAdd power in the central zone of the original multifocal CL design to compensate the optical power errors. Resultsobtained from IM process simulations and the optical simulations show that the new CL design with 0.1 Dincreasing in Add power has the closest shrinkage profile to the original anterior SM profile with Percentage ofReduction in absolute Z-Shrinkage error (PRS) of 55% and more uniform power in the central zone than the othertwo cases. Moreover, actual experiment of IM of SM for casting soft multifocal CLs has been performed. The finalproduct of wet CLs have been completed for the original design and the new design. Results of optical performancehas been verified the improvement of compensated design of CLs. The feasibility of this compensating method hasbeen proven based on the measurement results of the produced soft multifocal CLs of the new design. Results ofthis study can be further applied to predict or compensate the total optical power errors of the soft multifocal CLs.

Phase sensitive OTDR with ultrafast data processingbased on GPU parallel computation

Zhou Sha, Hao Feng, Yi Shi, and zeng zhoumo

Doc ID: 315536 Received 12 Dec 2017; Accepted 08 Mar 2018; Posted 08 Mar 2018  View: PDF

Abstract: The sensing performance of Φ-OTDR has been sufficiently improved thanks to plenty of valuable researches inrecent years. However in the literature there are hardly any attention aimed at enhancing the data processingcapability of the system, the necessity and significance of which is undisputed. This paper for the first timeanalyzed the intrinsic superiority of employing GPU parallel computation in Φ-OTDR for improving the dataprocessing capability and presents a comprehensive performance evaluation. Three typical, highly correlatedalgorithms in Φ-OTDR - moving average, batch Fast Fourier Transform and batch correlation dimensioncomputation - are carried out where CPU-based program and the corresponding counterpart GPU-based programare respectively developed. Their time consuming performance in different data scales are experimentally testedand compared. The experiment results show that in each case, employing GPU parallel computation cansignificantly enhance the system’s data processing capacity, thus providing a feasible and efficient way ofguaranteeing real time operation with the growing data scale.

Thermo-optic dispersion formula for BaGa₄Se₇

Kiyoshi Kato, Kentaro Miyata, Valeriy Badikov, and Valentin Petrov

Doc ID: 319387 Received 09 Jan 2018; Accepted 08 Mar 2018; Posted 08 Mar 2018  View: PDF

Abstract: This paper reports on the thermo-optic dispersion formula for BaGa₄Se₇ that provides a good reproduction of the temperature dependent phase-matching conditions for type-1 and type-2 second-harmonic generation of a Nd:YAG laser-pumped AgGaS₂ optical parametric oscillator (OPO) and a CO₂ laser in the 0.901-10.5910 μm spectral range as well as the published data points for a Nd:YAG laser-pumped OPO at λi = 3.9040 μm when combined with the Sellmeier equations of the present authors (K. Kato et al., Appl. Opt. 56, 2978-2981, 2017[1]).

Modeling the optical field in off-axis integrated-cavityoutputspectroscopy using decentered Gaussian beammodel

Guofeng Shen, Xing Chao, and Kai Sun

Doc ID: 309398 Received 26 Oct 2017; Accepted 08 Mar 2018; Posted 12 Mar 2018  View: PDF

Abstract: Off-axis integrated-cavity-output spectroscopy (OA-ICOS) is widely used in trace gas detection and isotopic analysisfor its enhanced sensitivity as well as robustness against optical instability. However, its sensitivity is ultimatelylimited by the spurious coupling noise formed in the cavity, and much of the design and optimization process relieson empirical iterations while quantitative analysis is lacking. In this paper, we develop a method to model theoptical field in OA-ICOS based on decentered Gaussian beam model, which is a generalization for large tilting anglesas compared with previously developed models. From the optical field, the cavity transmission spectrum fordifferent cavity configurations or input beam conditions can be calculated and the fringe noise level can be derived.Results show that an optimum combination of input laser beam and off-axis alignment exist to fully suppress theinterference fringes. Factors affecting the fringe noise level, including mismatch between the input beam and thecavity, optical alignment conditions, and deviation from the re-entrant condition, are studied thoroughly. Thedeveloped method can serve to guide the design and optimization of OA-ICOS systems.

A novel technique for two-dimensional displacement field determination using a reliability-guided spatial-gradient-based digital image correlation algorithm

Wei Feng, Yi Jin, Ye Wei, Wenhui Hou, and Chan Zhu

Doc ID: 319408 Received 09 Jan 2018; Accepted 08 Mar 2018; Posted 12 Mar 2018  View: PDF

Abstract: This paper proposed a novel in-plane displacement field measurement algorithm using an optical flow strategy. We built a linear illumination model between images before and after deformation to guarantee intensity invariability. We used image upsampling and a reliability-guided strategy to find the matching points accurate to 0.5 pixels in the reference and deformed images. The criterion to determine the reliability is zero-mean normalized cross-correlation coefficient. Afterward, we used the brightness constancy constraint combined with a first-order shape function in a specific image region to obtain an overdetermined linear equation. We applied the noniterative least-squares algorithm to solve the equations and to achieve the displacement offsets. This research utilized multithread calculation to handle the complete cracking applications. We estimated the computing efficiency and calculation precision of the proposed method through a series of experimental speckle patterns. All results demonstrated the correctness, effectiveness, and robustness of the proposed method.

Efficient solution to the stagnation problem of particleswarm optimization (PSO) algorithm for phasediversity

XIN QI, Guohao JU, and Shuyan Xu

Doc ID: 318507 Received 27 Dec 2017; Accepted 07 Mar 2018; Posted 08 Mar 2018  View: PDF

Abstract: Phase diversity (PD) technique needs optimization algorithms to minimize the error metric and find the globalminimum. Particle swarm optimization (PSO) is very suitable for PD due to its simple structure, fast convergence and globalsearching ability. However, the traditional PSO algorithm for PD still suffers from the stagnation problem (prematureconvergence) which can result in a wrong solution. In this paper, the stagnation problem of the traditional PSO algorithm forPD is illustrated first. Then an explicit strategy is proposed to solve this problem based on an in-depth understanding of theinherent optimization mechanism of the PSO algorithm. Specifically, a criterion is proposed to detect prematureconvergence; then a redistributing mechanism is proposed to prevent premature convergence. To improve the efficiency ofthis redistributing mechanism, randomized Halton sequences are further introduced to ensure the uniform distribution andrandomness of the redistributed particles in the search space. Simulation results show that this strategy can effectively solvethe stagnation problem of PSO algorithm for PD, especially for large scale and high dimension wavefront sensing and noisycondition. This work is further verified by an experiment. This work can improve the robustness and performance of phasediversity wavefront sensing.

Image quality degradation of object-color metamer mismatching in digital camera color reproduction

Jueqin Qiu, Haisong Xu, Zhengnan Ye, and Changyu Diao

Doc ID: 319487 Received 10 Jan 2018; Accepted 07 Mar 2018; Posted 07 Mar 2018  View: PDF

Abstract: Metamer mismatching is a phenomenon that two objects, which are colorimetrically indistinguishable under one lighting condition, become distinguishable under another one. Due to the unavailability of spectral information, metamer mismatching introduces an inherent uncertainty into cameras' color reproduction. To investigate the degree of image quality degradation by the metamer mismatching, a large spectral reflectance database was collected in this study to search the \textit{object-color metamers sets} (OCMSs) of the spectra in hyperspectral images. Then metamer-degraded images were constructed and compared with the ground truth images by directional statistics based color similarity index image quality assessment (DSCSI-IQA) metrics to evaluate the perceptual image degradation. The results indicate that the object-color metamer mismatching has only little impact on the image quality degradation, whereas the inappropriate selection of color correction matrices involved with the illuminant metamerism is the primary factor for the accuracy decrease in the digital camera color reproduction.

Reducing the minimum range of RGB-D sensor to aid navigation in visually impaired individuals

Kailun Yang, Kaiwei Wang, Hao Chen, and Jian Bai

Doc ID: 319718 Received 26 Jan 2018; Accepted 07 Mar 2018; Posted 07 Mar 2018  View: PDF

Abstract: The introduction of RGB-Depth (RGB-D) sensors harbors a revolutionary power in the field of navigational assistance for the visually impaired. However, RGB-D sensors are limited by a minimum detectable distance of about 800mm. This paper proposes an effective approach to decrease the minimum range for navigational assistance based on a RGB-D sensor of RealSense R200. A large-scale stereo matching between two IR images and a cross-modal stereo matching between one IR image and RGB image are incorporated for short-range depth acquisition. The minimum range reduction is critical not only for avoiding obstacles up close, but also in the enhancement of traversability awareness. Overall, the minimum detectable distance of RealSense is reduced from 650mm to 60mm with qualified accuracy. A traversable line is created to feedback visually impaired individuals through stereo sound. The approach is proved to be with usefulness and reliability by a comprehensive set of experiments and field tests in real-world scenarios involving real visually impaired participants.

Validity of the Instrument Transfer Function for Fringe Projection Metrology

Bin Zhang, Angela Davies, Chris Evans, and John Ziegert

Doc ID: 320459 Received 25 Jan 2018; Accepted 06 Mar 2018; Posted 07 Mar 2018  View: PDF

Abstract: When fringe projection profilometry is used for measuring texture on rough surfaces, the measurement resolution is subject to the spatial frequency response of the instrument. The instrument transfer function (ITF) is a good metric to quantify this property. A valid ITF analysis requires the system to be linear. In this paper, we investigate the validity of using ITF to characterize the spatial resolution of a fringe projection system. Approximate linearity is shown through a mathematical analysis and simulation. We also demonstrate a practical method for measuring ITF using a stepped surface. The measured ITF is compared with an ITF prediction which is simulated with a theoretical model.

A micro-analysis model for material removalmechanisms of bonnet polishing

chenchun shi, Yunfeng Peng, Liang Hou, Zhenzhong Wang, and Yinbiao Guo

Doc ID: 321179 Received 31 Jan 2018; Accepted 06 Mar 2018; Posted 07 Mar 2018  View: PDF

Abstract: There has been many researches concerning the modeling for material removal mechanisms of bonnet polishing(BP) based on the well-known Preston model. However, various parameters involved in the BP process are notformulated and considered into the classical model, such as slurry characteristics, pad properties, bonnet featuresand processing conditions. In this paper, a Micro-analysis model capturing those parameters is proposed based onthe mutual interaction of the slurry, pad and workpiece among the BP interfaces with the micro-contact theory andthe tribology theory. The proposed model is validated by comparing with the experimental data and goodagreement can be obtained. According to the analysis of key parameters, the proposed model is capable of layingsome insights into the material removal mechanisms of BP and even those cannot be explained properly by theclassical Preston model.

Active control of edge-mode-based plasmon-induced absorption sensor

Yong Li, Yi Su, qi lin, Xiang Zhai, and Wang Lingling

Doc ID: 317900 Received 18 Dec 2017; Accepted 06 Mar 2018; Posted 06 Mar 2018  View: PDF

Abstract: We investigate the formation and evolution of plasmon-induced absorption (PIA) effect in a three-dimensional graphene waveguide structure. The PIA window is formed by the near-field coupling of graphene edge mode, the extremely destructive interference between radiative mode and the sub-radiative mode of graphene nanoribbons. Resonance intensity has a significant dependence on the coupling distance between graphene nanoribbons. At the same time, it is particularly sensitive to the refractive index of the environment, which is promising for sensing devices. In addition, the resonant wavelength is actively controlled by changing the Fermi energy of graphene. Moreover, it can be seen that the group time delay of the PIA window reaches -0.28ps, which is a good candidate for ultra-fast light application. Finally, additional graphene nanoribbon can also form a double-channel PIA window. Our work may provide an excellent platform for controlling the optical transmission of highly integrated plasmonic components.

The morphologies, optical and electrical properties ofInGaN/GaN micro-square array light emitting diodechips

Dan Han, Shufang Ma, Zhigang Jia, Peizhi Liu, wei jia, Lin Shang, zhai guangmei, and bingshe xu

Doc ID: 318159 Received 22 Dec 2017; Accepted 06 Mar 2018; Posted 07 Mar 2018  View: PDF

Abstract: InGaN/GaN micro-square array light emitting diode (LED) chips (micro-chips) have been prepared via focused ionbeam (FIB) etching technique which can not only reduce ohmic contact degradation but also control the aspectratio precisely in three-dimensional (3D) structure LED (3D-LED) devices fabrication. The effects of FIB beamcurrent and micro-square array depth on morphologies, optical and electrical properties of the micro-chips havebeen studied. Our results show that sidewall surface morphology, optical and electrical properties of micro-chipsdegrade with increased beam current. After KOH etching with different times, an optimal current–voltage (I-V) andluminescence performance can be obtained. Combining the results of cathodoluminescence (CL) mappings andlight output-current(L-I) characteristics, the light extraction efficiency (LEE) of micro-chip is reduced as FIB etchdepth increases. The mechanisms of micro-square depth on light extraction have been revealed by threedimensionalfinite difference time domain (3D-FDTD).

Size reduction of Ge-on-Si photodetectors via photonic band gap

haifeng zhou and Yiling Sun

Doc ID: 320082 Received 05 Feb 2018; Accepted 06 Mar 2018; Posted 16 Mar 2018  View: PDF

Abstract: This work shrinks down the size of Ge-on-Si photo-detectors to reduce the dark current and maintain the optical responsivity by surrounding photonic crystals. Numerical simulation shows that the employment of photonic crystal in the Si slab effectively prohibit the radiation modes from guided outgoing waves and facilitate light cyclic absorption in the epitaxial Ge region. A photo-detector with 5 um-long Ge absorption region is demonstrated with a dark current of 150 nA (1 uA up to 70℃), a 3-dB bandwidth of 17 GHz and a responsivity of 0.75 A/W.


Alexander Durst, Michael Wensing, and Edouard Berrocal

Doc ID: 320720 Received 25 Jan 2018; Accepted 05 Mar 2018; Posted 06 Mar 2018  View: PDF

Abstract: This article describes the adaptation of the laser-induced fluorescence (LIF) measurement technique for the investigation of the primary breakup ofmodern diesel and gasoline direct injection sprays. To investigate the primary breakup, a microscopic technique is required and with the help ofspecial tracer dyes, a high fluorescence signal can be achieved in the visible range of the electromagnetic spectrum, resulting in good image qualitywith a non-intensified camera. Besides the optimization of the optical setup for the microscopic field of view, different tracer dyes are compared andtheir solubility and fluorescence tested in the desired surrogate and real-world fuels. As a tracer, the phenoxazine dye Nile Red was found to providesufficient solubility in alkanes as well as suitable emission and excitation spectrum for the use of the second harmonic frequency of an Nd:YAG laser(532 nm). The good quantum efficiency delivered by Nile Red also meant that single-shot images clearly showing spray structures in regionsmeasuring up to 3 by 3 mm around the nozzle outlet could be recorded. Compared to relatively easy shadowgraph techniques and complex andcostly X-ray synchrotron measurements, LSFM imaging is not overly complex yet delivers excellent data on spray structures as well as qualitativefuel distribution.

Wavelength modulation technique-based photoacoustic spectroscopy for multi-point gas sensing

zongliang wang, Cunwei Tian, Qi Liu, Jun Chang, Qinduan Zhang, and cunguang zhu

Doc ID: 318275 Received 21 Dec 2017; Accepted 05 Mar 2018; Posted 05 Mar 2018  View: PDF

Abstract: A multi-point gas sensing scheme based on photoacoustic spectroscopy was proposed. Multiple photoacousticspectroscopy (PAS) gas cells (resonant frequency f 0 = 5.0 kHz) were connected in series for the multi-point gassensing with wavelength modulation technique. The PAS signal was excited by modulating the tunable distributedfeedback laser diode (DFB-LD) wavelength at f 0∕2 using changing driving current. The gas concentration of each gascell was obtained by the PAS signal which was demodulated by the lock-in amplifier. A multi-point PAS experiment todetect the water vapor at 1368.597nm was implemented to verify the scheme we presented. With the three PAS gascells, the linear response to the water vapor concentration of our sensors achieved 0.9978, 0.99591 and 0.99617respectively and the minimum detection limit of them were 479, 662 and 630 ppb correspondingly.

Numerical modeling of the effect of multipleincoherent layers in Cu(In,Ga)Se2 solar cells based onthe equispaced thickness averaging method

Kyungnam Kang, Sung Chul Kim, and Jung Ho Kim

Doc ID: 318287 Received 21 Dec 2017; Accepted 05 Mar 2018; Posted 05 Mar 2018  View: PDF

Abstract: We investigate the effect of multiple incoherent layers on the optical characteristics of Cu(In,Ga)Se2 (CIGS) solarcells, based on the equispaced thickness averaging method (ETAM). The studied multiple incoherent layers consistof a glass cover layer, surface flattening layer, and transparent conducting layer, whose respective thicknesses arelarger than the coherence length of sunlight (~0.6 μm). An independent equispaced thickness is added to eachincoherent layer and the coherent simulation results, obtained by finite element method, are averaged over acombination of the equispaced thicknesses. By applying the proposed method, we calculated the reflectancespectra in planar and surface-textured CIGS solar cells. Considering the planar structure, the calculation resultsbased on the ETAM are in good agreement with the exact analytical solution based on the generalized transfermatrix method. The statistical deviation from the exact solution was calculated with respect to the number of theequispaced thicknesses in each incoherent layer. When only four equispaced thicknesses are used, the calculateddeviation from the exact solution rapidly decreases to 1% for planar and 10% for surface-textured CIGS solar cells,which demonstrates that the effect of the multiple incoherent layers can be efficiently calculated based on theETAM in thin-film solar cells.

Smart design of LPFG refractive index sensorbased on dual-peak resonance near PMTP

qiang ling, Zhengtian Gu, and Kan Gao

Doc ID: 312539 Received 02 Nov 2017; Accepted 05 Mar 2018; Posted 05 Mar 2018  View: PDF

Abstract: This paper presents a smart design way for the long period fiber grating (LPFG) refractive index sensor, which isbased on high sensitivity of LPFG near phase-matching point (PMTP) to the surrounding refractive index (SRI). Onthe basis of coupled mode theory of LPFG, cladding etching and film coating have opposite effect on the shift of thedual peaks. Therefore, an LPFG can be controlled by the cladding etching and film coating successively, until itoperates near PMTP. Experimentally, an LPFG operating near PMTP was fabricated, and the glycerol solutionconcentration monitoring test was performed. The results show that the sensitivity of this LPFG to the SRI is as highas 5602nm/RIU.

Wide-band white light sparse aperture Fizeau imaginginterferometer testbed for distributed small satellitesconstellation

aimin jiang, Sen Wang, Zhichao Dong, Jianwei Xue, jing wang, and Yanfeng Dai

Doc ID: 314622 Received 29 Nov 2017; Accepted 05 Mar 2018; Posted 05 Mar 2018  View: PDF

Abstract: Under the background of astronomical observation by a distributed small satellites constellation, a Fizeau imaginginterferometer testbed (FIIT) was designed and constructed at NAOC in the past four years, which achieved widebandwhite light (400-700nm) phased imaging at laboratory with a field of view (FOV) ~2 arcmin. This study presentsthe design of FIIT, which is mainly composed of a light source module for simulating infinite objects, threesub-telescopes in a Golay-3 distribution (i.e., equilateral triangle), three tip/tilt correction modules and opticalpath delay modules, as well as three detecting telescopes and one beam combining telescope for phased imaging.The three detecting telescopes could determine the piston and tip/tilt errors, which could be compensated by opticalpath delay modules and fast steering mirrors in a close-loop mode. The performance of FIIT is also derived analyticallyand simulated by a ray-tracing model. The tolerance analysis of the pupil geometry and magnificationmatching are also performed for achieving a better FOV. The optical test of each module could efficiently validatethem to achieve diffraction limit imaging. The preliminary experimental results for both point source and extendscene could sufficiently demonstrated the phased mode imaging of FIIT, thus validated the good prospect of thistechnique in the future.

Arbitrary trapezoidal illumination generation method based on variable slits for optical lithography

lin liang, Zhang Fang, cheng lin, and Huijie Huang

Doc ID: 319158 Received 11 Jan 2018; Accepted 04 Mar 2018; Posted 05 Mar 2018  View: PDF

Abstract: Trapezoidal illumination is an effective approach to improve the integrated uniformity of light intensity in step-and-scan lithographic systems. When different laser pulses are utilized, the optimal trapezoidal illumination varies. In addition, if the coherence factor takes different values, the outline of the trapezoidal illumination varies as well, which directly affects the exposure dose. In order to reduce the impact of variations in trapezoidal illumination, a newly designed method for generating arbitrary trapezoidal illuminations using variable slits is proposed. The performance of our method after adjusting the trapezoidal profile for different coherence factors in different illumination modes was verified through optical simulations. Compared with the traditional method, the proposed strategy to realize arbitrary trapezoidal illuminations based on variable slits can obtain the best outlines for illumination, calculated by balancing pulse quantization error and energy losses. Furthermore, when different coherence factors are applied, the outline of the generated trapezoidal illumination can always be maintained by simply moving the blades an appropriate distance.

No-reference stereoscopic image quality assessment guided by visual hierarchical structure and binocular effects

Yong Ding and Yang Zhao

Doc ID: 318144 Received 20 Dec 2017; Accepted 04 Mar 2018; Posted 05 Mar 2018  View: PDF

Abstract: Stereoscopic image quality assessment (SIQA) is an essential technique for modern 3D image and video processing systems serving as performance evaluators and monitors. However, the study upon SIQA remains immature due to the complexity of human visual system (HVS) and binocular effects that binocular vision brings about. To overcome the difficulties, a novel method is proposed that extracts and quantifies image quality-aware features related to cortex areas in charge of visual quality perception, rather than attempts to rigorously simulate the biological processing in HVS, so that the predicting accuracy is preserved while the computational complexity remains moderate. In the meanwhile, binocular effects including binocular rivalry and visual discomfort are taken into consideration. Moreover, the proposed method can be operated completely without the assistance of reference images, indicating its wide practical usages. Comparing to state-of-the-art works, our method shows evident superiority in terms of effectiveness and robustness.

Automated collimation testing by determining thestatistical correlation coefficient of Talbot self-images

Santosh Rana, Jitendra Dhanotia, Vimal Bhatia, and Shashi Prakash

Doc ID: 314265 Received 14 Dec 2017; Accepted 03 Mar 2018; Posted 05 Mar 2018  View: PDF

Abstract: In this paper, we propose a simple, fast, and accurate technique for detection of collimation position of an opticalbeam using self-imaging phenomenon and correlation analysis. Herrera-Fernandez et. al. [Dual self-imagetechnique for beam collimation, J. Opt. 18, 2016] proposed an experimental arrangement for collimationtesting by comparing the period of two different self-images produced by a single diffraction grating.Following their approach, we propose a testing procedure based on correlation coefficient (CC) for efficientdetection of variation in the size and fringe width of the Talbot self images, and thereby the collimation position.When the beam is collimated, the physical properties of the self-images of the grating such as its size and fringewidth do not vary from one Talbot plane to the other, and are identical; the CC is maximum in such a situation. Forthe de-collimated position, the size and fringe width of the self-images vary and correspondingly the CC decreases.Hence, the magnitude of CC is a measure of degree of collimation. Using the method, we could set the collimationposition to a resolution of 1 μm, which relates to ±0.25μ radians in terms of collimation angle (for testing acollimating lens of diameter 46mm and focal length 300mm). In contrast to most collimation techniques reportedtill date, the proposed technique does not require any translation/rotation of the grating, use of complicated phaseevaluation algorithms, or the intricate method for determination of period of the grating or its self-images. Thetechnique is fully automated, provides high resolution and precision.

Eddy Current Pulsed Thermography for Ballistic Impact Evaluation in Basalt-Carbon Hybrid Composite Panels

Hai Zhang, Stefano Sfarra, Ahmad Osman, Fabrizio Sarasini, Udo Netzelmann, Stefano Perilli, Clemente Ibarra-Castanedo, and Xavier Maldague

Doc ID: 319879 Received 18 Jan 2018; Accepted 03 Mar 2018; Posted 05 Mar 2018  View: PDF

Abstract: In this paper, eddy current pulsed thermography was used to evaluate ballistic impact damages in basalt-carbon hybrid fiber-reinforced polymer composite laminates for the first time. In particular, different hybrid structures including intercalated stacking and sandwich-like sequences were used. Pulsed phase thermography, wavelet transform, principle component thermography and partial least square thermography were used to process the thermographic data. Ultrasound C-scan testing and X-ray computed tomography were also performed for comparative purposes. Finite element analysis was used for validation. Finally, an analytical and comparative study was conducted based on signal-to-noise ratio analysis.

All-optical tunable power splitter based on surface plasmonic two-mode interference

NILIMA GOGOI and Partha Sahu

Doc ID: 322613 Received 05 Feb 2018; Accepted 03 Mar 2018; Posted 05 Mar 2018  View: PDF

Abstract: In this paper, we have introduced surface plasmonic two-mode interference (SPTMI) coupler having silicon core, GaAsInP side cladding and silver top and bottom cladding as an optical power splitter. Wide range of tunability from 50:50 splitting ratio to 1:99 is achieved by refractive index modulation of GaAsInP cladding with application of varying optical pulse power. The coupling length of SPTMI based splitter is ~11.5 times less than that of previously reported optical power splitter based on multimode waveguide holograms. The proposed optical power splitter has potential in development of large scale integrated circuits due to its compactness and high fabrication tolerance.

Design of two-dimensional diffractive optical elements for beam shaping of multicolor light-emitting diodes

Huarong Gu, Mengzhu Chen, Qixia Wang, and Qiaofeng Tan

Doc ID: 315450 Received 11 Dec 2017; Accepted 03 Mar 2018; Posted 05 Mar 2018  View: PDF

Abstract: To achieve cellular network in visible light communication, the illumination areas covered by red, green, and blue light-emitting diodes (LEDs) forming a white LED should be of the same size with uniform intensity distribution. In this paper, the iterative algorithm for the design of multicolor oriented two-dimensional diffractive optical elements (DOEs) is improved. Simulation results indicate that almost the same size of the diffraction patterns of the DOE illuminated by multicolor LEDs is achieved with good uniformity of the intensity distribution.

Solar spectrum matching with white OLED and monochromatic LEDs

Huiyuan Yu, Guanying Cao, Jinghui Zhang, Yi Yang, Wenliang Sun, Liping Wang, and Nianyu Zou

Doc ID: 308094 Received 18 Oct 2017; Accepted 02 Mar 2018; Posted 02 Mar 2018  View: PDF

Abstract: In the paper, the solar spectrum matching in the visible range of 380-780 nm with white OLED and monochromatic LEDs is investigated.The correlation index (R^2) is used to evaluate the difference between the matching spectrum and the solar spectrum. The optimal combinationis obtained by the least square method. We perform the subtraction experiments on the basis of the optimal combination. We utilize a commonwhite OLED device design and just change the species of monochromatic LEDs used. We report and evaluate different degrees of matchingeffects. The results show that the correlation index of the best combination can reach 94.09% with OLED and 36 monochromatic LEDs. We define3 levels as an evaluation system in accordance with matching effect. The level is excellent with R^2 above 90.14%. The good level is from 86.65%to 58.28%. From 42.08% to 33.06% is the reasonable level. Compared with other methods, using white OLED compensated with monochromaticLEDs can achieve the best solar spectrum matching effect. The results can be applied in different requirements of engineering practice.

Powder SFG as a versatile method for infrared opticalalignment

Baodong Gai, Hong Yuan, Yuefeng Song, Jinbo Liu, Shu Hu, Xianglong Cai, Pengyuan Wang, Ying Chen, and jingwei Guo

Doc ID: 312259 Received 30 Oct 2017; Accepted 02 Mar 2018; Posted 02 Mar 2018  View: PDF

Abstract: The SFG (sum-frequency generation) in KDP (potassium dihydrogen phosphate) powder with μm-grade particlesizeis successfully demonstrated under various experimental conditions. Two focused beams of 870 nm and 1369nm are used for SFG excitation. SFG is observed under different excitation energies. The SFG intensity showsisotropy with different observation azimuth. The intersection angle between two excitation beams is not limited byconventional phase-matching conditions, and it owns the flexibility of a very large allowed range, for example, itcan be 0 °~100 ° in this work. The polarization combination of excitation beams is not limited either. Thanks to thenon-toxicity, low-price and low SFG threshold properties of KDP material and the optical flexibility, this powderSFG technology is a versatile method, and is expected to be applied to a various situations of optical alignment, e.g.surface SFG, FWM (four-wave mixing), CARS (coherent anti-Stokes Raman spectroscopy), multi-color laserexcitation, etc. The effect of potential powder SFG assisted optical alignments is also discussed. Extension of thismethod to multi- beams, tight focusing beams, and plasmonic polariton devices are proposed.

Accurate and Rapid Detection of Soil and FertilizerProperties based on VIS/NIR Spectroscopy

Zhidan Lin, Rujing Wang, yubing Wang, Liusan Wang, Cuiping Lu, Yang Liu, Zhenyong Zhang, and Likai Zhu

Doc ID: 320041 Received 18 Jan 2018; Accepted 02 Mar 2018; Posted 02 Mar 2018  View: PDF

Abstract: Accurate information of soil macronutrient contents and fertilizer macronutrient contents is the precondition ofprecision fertilization; however, how to detect soil and fertilizer information rapidly, reliably and inexpensivelyremains a great challenge. Visible and near infrared (VIS/NIR) diffuse reflectance spectroscopy proves to be aneffective tool for extensive investigation of soil and fertilizer properties. This study first collected a lot of soil andchemical fertilizer samples and performed both spectral scanning and chemical analysis. During the correlationbetween the collected VIS/NIR spectra and the measured data, different spectral pretreatment, sample selectionand wavelength optimization methods were applied for improving the accuracy and robustness of the predictionmodels. After appropriate spectral processing and selection of representative samples, both PCA and GA canadequately reduce the number of variables and pick out the characteristic variables, which not only enhancedprediction speed but also greatly improved prediction accuracy. In particular, using GA-based models, OMC, total Nand pH value in soil and N, P and K contents in fertilizer can all be accurately predicted.

Effects of auxiliary atmospheric state parameters on the aerosol optical properties retrieval errors of high-spectral-resolution lidar

Yupeng Zhang, Dong Liu, Zhuofan Zheng, Zhengkuan liu, Deyun Hu, Bing Qi, Chong Liu, Lei Bi, Kejun Zhang, chunao wen, lingying jiang, yuling Liu, Ju Ke, and Zhongming Zang

Doc ID: 315092 Received 07 Dec 2017; Accepted 02 Mar 2018; Posted 02 Mar 2018  View: PDF

Abstract: A detailed assessment is carried out in relation to the influence of the uncertainties associated with the input auxiliary atmospheric state parameters on retrieving aerosol optical properties from high-spectral-resolution lidar (HSRL) observations. The study starts from a review of the main spectral structure of the backscattering in elastic lidar followed by evaluating the temperature effects on backscattering cross section of atmospheric molecules based on numerical simulation. It shows that the transmittance of the background interference filter should be taken into account depending on the full width at half maximum (FWHM), although overall temperature sensitivity is negligible. Based on the Taylor expansion of Tenti S6 model, the systematic errors arising from input temperature and pressure profiles are analyzed. It is demonstrated that the atmospheric pressure profiles have limited effects on the inversion results of aerosol optical parameters as the atmospheric pressure is usually quite stable. The relative errors of aerosol backscatter coefficient mainly stem from temperature profile errors and highly depend on the aerosol concentration. Quantitatively, the aerosol backscatter coefficient error could be larger than 5% with a 3K deviation of temperature when the backscatter ratio is lager than 1.1. The accuracy of aerosol extinction coefficient retrieval is affected not only by the error in temperature, but also by the error in temperature lapse rate; the retrieval accuracy is more sensitive to the latter than the former. Further analysis based on the sounding temperature data shows that the variation of temperature inversion layer during the night could induce a bias larger than 0.04km-1 on the aerosol extinction coefficient retrieval. Therefore, the time resolution of temperature measurement from sounding balloons twice per day is too low to obtain an accurate retrieval of the aerosol optical properties from the HSRL.

Influences of surface defects on the laser-induced damage performances of KDP crystal

Shengfei Wang, Jian Wang, Qiao Xu, Xiangyang Lei, Zhichao Liu, and Jianfeng Zhang

Doc ID: 315558 Received 13 Dec 2017; Accepted 02 Mar 2018; Posted 02 Mar 2018  View: PDF

Abstract: When Potassium Dihydrogen Phosphate (KDP) crystals are exposed to high energy laser irradiation, the preexistingsurface defects may act as damage precursors and will reduce the lifespan of crystal components. Thoughit has been found that different kinds of surface defects exhibit distinct damage characteristics, the influences ofsurface defects on the laser-induced damage performance of KDP crystal is not clear yet. In this paper, KDP surfacedefects have been characterized by multiple measuring methods and classified into five categories according totheir structure features. Laser-induced damage tests were then carried out to investigate the laser-induced damagethresholds of different kinds of KDP surface defects as well as the morphology evolution of damage sites.Experiment results indicate that the damage thresholds of cracks, fracture pits and surface protuberances arebetween 6-11 J/cm2 (355nm, 3ns, similarly hereinafter), which are much lower than the thresholds of plasticscratches, discontinuous scratches and defects-free KDP surface. In addition, it has been found thatfluorescence enhancement is just a necessary condition for reduction of damage thresholds. Finally, formingreasons of the most threatening KDP surface defects have been analyzed and corresponding suppression measureshave been proposed for increasing the surface damage threshold of crystal components.

Spatial hole burning in thin-disk lasers andtwisted-mode operation

Karsten Schuhmann, Klaus Kirch, Francois Nez, Randolf Pohl, Gunther Wichmann, and aldo antognini

Doc ID: 313560 Received 06 Dec 2017; Accepted 02 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: Spatial hole burning prevents single-frequency operation of thin-disk lasers when the thin disk is used as a foldingmirror. We present an evaluation of the saturation effects in the disk for disks acting as end-mirrors andas folding-mirrors explaining one of the main obstacles towards single-frequency operation. It is shown thata twisted-mode scheme based on a multi-order quarter-wave plate combined with a polarizer provides an almostcomplete suppression of spatial hole burning and creates an additional wavelength selectivity that enforcesefficient single-frequency operation.

Diffraction characteristics of Laguerre-Gaussian beam through a Maksutov-Cassegrain optical system

Xizheng Ke, Jiao Wang, Mingjun Wang, and Tan Zhenkun Tan

Doc ID: 318475 Received 28 Dec 2017; Accepted 01 Mar 2018; Posted 02 Mar 2018  View: PDF

Abstract: Maksutov–Cassegrain (MC) systems are widely used in long-range free-space optical (FSO) communication. In this study, analytical expressions for the diffraction field of a Laguerre–Gaussian (LG) beam passing through an MC system have been derived. The numerical results reveal that in the long-range FSO system, the replacement of a Gaussian beam by the LG beam enhances the emission efficiency of the MC. Furthermore, the MC has a shaping effect on the LG beam, and the orbital angular momentum of the LG beam is not dispersed when the beam is diffracted by the MC.

Resolution enhancement of wide-field interferometricmicroscopy by coupled deep autoencoders

Çağatay IŞIL, Mustafa Yorulmaz, Berkan Solmaz, Adil Turhan, Celalettin Yurdakul, M. Selim Ünlü, Ekmel Ozbay, and AYKUT KOC

Doc ID: 319155 Received 08 Jan 2018; Accepted 01 Mar 2018; Posted 02 Mar 2018  View: PDF

Abstract: Wide-field interferometric microscopy is a highly sensitive, label-free and low-cost biosensing imaging technique capable of visualizing individual biological nanoparticles such as viral pathogens and exosomes. However, further resolution enhancement is necessary to increase detection and classification accuracy of sub-diffration limited nanoparticles. In this study, we propose a deep learning approach, based on coupled deep autoencoders, to improve resolution of images of L-shaped nanostructures. During training, our method utilizes microscope image patches and their corresponding manual truth image patches in order to learn the transformation between them. Following training, the designed network reconstructs denoised and resolution enhanced image patches for unseen input.

Study on spectral and refractive index sensing characteristics of etched excessively tilted fiber gratings

Huafeng Lu, Bin-bin Luo, Shenghui Shi, M Zhao, Jiao Lu, Lu Ye, Niangbing Zhong, Bin Tang, Xin Wang, and Yajie Wang

Doc ID: 319172 Received 08 Jan 2018; Accepted 01 Mar 2018; Posted 02 Mar 2018  View: PDF

Abstract: We investigated the spectral and refractive index(RI) sensing characteristics of the excessively tilted fiber grating (Ex-TFG) with different cladding diameters. The Ex-TFG is inscribed in standard single mode fiber and the cladding reduces from 125μm to around 15μm by chemical etching method. Experimental results show that the number of cladding modes decreases and the spacing of adjacent resonance peaks becomes larger and larger with the reduction of cladding diameter in the observed wavelength range of 1250nm~1650nm. The average RI sensitivity in the index region of 1.33~1.38, the one near 1.33, and the one at around 1.38 of the etched Ex-TFG with diameter of 15μm is ~6.3, ~5.3, and ~6.67 fold as compared to those of the no-etched Ex-TFG, respectively. And also, the RI sensing performances of the etched Ex-TFG with diameter smaller than 30μm are better than that of the Ex-TFG inscribed in SM1500(4.2μm/80μm) fiber in the index region of 1.33. The proposed micro-nano Ex-TFG has higher RI sensitivity and more compact structure in biosensing applications, as compared with the standard Ex-TFGs and Ex-TFGs inscribed in SM1500 fiber.

High-sensitivity Humidity Sensing of Side-PolishedOptical Fiber with Polymer Nanostructure Cladding

Li Tang, Yaoming Feng, Zengshan Xing, zhe chen, JianHui Yu, Heyuan Guan, Huihui Lu, Junbin Fang, and Yongchun Zhong

Doc ID: 319520 Received 10 Jan 2018; Accepted 01 Mar 2018; Posted 01 Mar 2018  View: PDF

Abstract: This paper presented a high-sensitivity humidity sensorcomprised of a side-polished fiber (SPF) with polymernanostructure cladding, which was constructed bydehydrating dichromate gelatin (DCG) film on the polishedsurface. Due to intermodal interference of coremode and cladding modes, two main transmission dipswere observed at 1184.4 nm and 1325.6 nm. These twotransmission dips showed significant sensitivity to humidity.The position of transmission dip at 1325.6nmshifted 22nm while the relative humidity (RH) changefrom 30 %RH to 50 %RH. The humidity sensitivitywas up to 1.12 nm/%RH and its linear correlation was98.45 %. The humidity sensing characteristic of nanostructurecladding fiber was successfully demonstrated.This novel sensor is compatible with optical fiber systemand has high potential in optical sensing applications.

3-D profiling of rough SiC surfaces by coherence scanning interferometry using femtosecond laser

Yang Lu, Jiyong Park, Liandong Yu, and Seung-Woo Kim

Doc ID: 323102 Received 15 Feb 2018; Accepted 01 Mar 2018; Posted 02 Mar 2018  View: PDF

Abstract: We test an Er-doped fiber femtosecond laser for its potential as a light source of coherence scanning interferometer for large field-of-view profiling of rough SiC surfaces. This infrared fiber pulse laser is able to provide a relatively long temporal coherence length of ~30 μm to be appropriate for coherence scanning of rough surfaces. At the same time, it offers high degree of spatial coherence comparable to that of a monochromatic cw laser to achieve a large measurement field-of-view at a time. In addition, the highly maintained linear polarization of the pulse laser source permits overcoming the low specular reflectance of rough SiC surfaces by polarization based optical power splitting control between the reference and measurement arms.

Measurement of grating groove density using multiplediffraction orders and one standard wavelength

Bing Sheng, Guohua Chen, Yuanshen Huang, and LUWEN LUO

Doc ID: 314033 Received 22 Nov 2017; Accepted 01 Mar 2018; Posted 02 Mar 2018  View: PDF

Abstract: A new method for measuring grating groove density is proposed using multiple diffraction orders and one standard wavelengthto eliminate the eccentricity effect originated from the rotation of diffraction grating. Based on Littman configuration forautocollimation, the groove density can be obtained by measuring the internal angles between the zeroth-order and twononzeroth-order diffracted beams for one laser wavelength at a certain incident angle. The method was applied to measure thegroove density of a plane grating with a nominal groove density of 651 lines/mm, where the mean value of this grating wasmeasured to be 650.76 lines/mm with relative measurement error ΔN/N of 3.8× 10-5.

Compact optical image amplifier pumped by a subnanosecondNd:YAG microlaser

lei liu, Hongyan Wang, Yu Ning, ren ge, Yi Yang, Fengjie Xi, and Lei Si

Doc ID: 313668 Received 17 Nov 2017; Accepted 01 Mar 2018; Posted 05 Mar 2018  View: PDF

Abstract: A compact sub-nanosecond optical image amplifier is proposed followed by being demonstrated. It is pumped by anactively Q-switched diode-pumped Nd:YAG microlaser in virtue of the optical parametric amplification (OPA)technique and quasi phase matching scheme. Experimental results show that the optical image gain reaches 15.4 dBunder pump intensity of 15.3 MW/cm2 pump intensity. The influence of parametric fluorescence noise on theamplified image is obvious after 10 dB gain. The signal-to-noise ratio degradation of amplifier image characterizedby the noise figures is sheer contrast with theoretical expectations. It shows that the experimental noise figurevalue reaches 2.2 dB, larger than the theoretical result of 0.7 dB at 15 dB gain.

QEPAS sensor for breath analysis: A behavior of pressure

Tobias Milde, Morten Hoppe, Herve Tatenguem Fankem, Mario Mordmüller, Ulrike Willer, Wolfgang Schade, Joachim Sacher, and James O’GORMAN

Doc ID: 312591 Received 02 Nov 2017; Accepted 01 Mar 2018; Posted 01 Mar 2018  View: PDF

Abstract: The measurement of trace gases become more and more a fundamental technique in healthcare and other medical applications. The quartz-enhanced photoacoustic spectroscopy (QEPAS) is therefor a suitable method which can provide appropriate results for a comparatively low cost and small size. The quantitative detection and a low detection limit is required. In this paper we present new results on sensing biomedical relevant gases using the on-beam QEPAS technique with some newly developed tunable high power single mode laser diodes based on the GaSb material. The data processing and detection limit determination is done by a FPGA device as well as a automatic measurement of the resonance frequency.

Effect of laser shock peening on electrochemical corrosion resistance of IN718 superalloy

Chengyi Ning, guangyi zhang, Yapeng Yang, and Wenwu Zhang

Doc ID: 315075 Received 03 Jan 2018; Accepted 01 Mar 2018; Posted 01 Mar 2018  View: PDF

Abstract: The effects of laser shock peening (LSP) treatment with different impacts on surface roughness, micro-hardness, microstructural observations, residual stress and electrochemical corrosion resistance of IN718 superalloy were investigated. Results show that the corrosion potential increases to −0.4863 V,−0.2956 V,−0.3578V and the corrosion rate reduces 56.31%, 79.08%, 84.07% for 2 impacts, 4 impacts, 6 impacts respectively compared with the untreated one. In addition, LSP treatment has an important influence on gain refinement which increases micro-hardness, reduces roughness of surface, and also results in a compressive residual stress on surface, both of which can be responsible for the electrochemical corrosion improvement. Finally, corrosion morphology under scanning the electron microscopy (SEM) demonstrates that LSP is an effective method to prevent the corrosion micro-crack propagation along and improve the corrosion resistance. Also, with an increase in laser impacts, the electrochemical corrosion resistance will be further improved.

Profiled absorber design illuminated uniformly byparabolic reflectors

RAbi Rabady, Mohamed Al-fandi, Mohammad Khasawneh, Abeer Andrawes, and yahia makableh

Doc ID: 315425 Received 13 Dec 2017; Accepted 28 Feb 2018; Posted 01 Mar 2018  View: PDF

Abstract: In this paper a general method is proposed in order to develop a special absorber profile that receives sunlight fromparabolic reflector uniformly. Different parameters were taken into consideration while performing the simulation includingreflector focal length, collector length and concentration ratio. The total power reflected to the absorber was calculated byaccounting for the Fresnel angular dependency and the shadowing effect by the absorber. Furthermore, a verification methodbased on the ray tracing technique was also developed in order to verify that uniform illumination was achieved. Theuniformity of the sunlight flux onto the absorber is expected to improve solar system efficiency and extend its life service.Therefore, the validated absorber profile design in this theoretical work can be useful for applications which employ parabolicconcentrators with the concern of reaching higher performance by achieving uniform concentration ratio on the absorber.

A theoretical surface type classifier based on awaveform model of a satellite laser altimeter and itsperformance in the north of Greenland

Song Li, Wenhao Zhang, Yue Ma, xiaohua wang, Fanlin Yang, and Su Peng

Doc ID: 315683 Received 13 Dec 2017; Accepted 28 Feb 2018; Posted 01 Mar 2018  View: PDF

Abstract: Current land-cover classification methods using ICESat/GLAS’s (Ice, Cloud, and land Elevation Satellite/ GeoscienceLaser Altimeter System) datasets are based on empirical thresholds or machine learning by training multiple GLASparameters, e.g., the reflectivity and elevation of the target and width, amplitude, kurtosis, and skewness of thereturn waveform. A theoretical classifier is derived based on a waveform model of an actual laser altimeterilluminating the sea surface. With given system parameters and the sea surface wind corresponding to the locationof a laser footprint (the wind can be calculated by using the National Centers for Environmental Prediction (NCEP)dataset), a precise theoretical waveform can be generated as a reference. Compared with the measured waveform,a Weighted Total Difference (WTD), which is very sensitive to small-scale sea ice within the laser footprint, can becalculated to classify the GLAS measured data as open water. In the north of Greenland, after discarding thesaturated GLAS data, the new theoretical classifier performed better (Overall Accuracy OA=95.62%, Kappacoefficient=0.8959) compared to the classical SVM (Support Vector Machine) classifier (OA=90.44%,Kappa=0.7901), but the SVM classifier showed a better result for the User's accuracy of sea ice. Benefiting from thesynergies of the theoretical and SVM classifiers, the integrated theoretical and SVM classifier achieved excellentaccuracy (OA=98.21%, Kappa=0.9588). In the future, the new ICESat-2 photon counting laser altimeter will alsoconstruct a ‘waveform’ (elevation distribution) by selecting the photon cloud; and thus, this new analytical methodwill be potentially useful for detecting open water in the Arctic.

Steep large film thickness measurement with off-axisterahertz digital holography reconstructed by directFourier and Hermite polynomial

Dahi Abdelsalam

Doc ID: 315726 Received 04 Jan 2018; Accepted 28 Feb 2018; Posted 01 Mar 2018  View: PDF

Abstract: In this paper, we enhance the steepness of film thickness edge in THz off-axis digital holography by employing areconstruction method based on direct Fourier and Hermite polynomial function. The method is applied to samples of110μm and 80μm step heights to extract the phase images in real time. Use of this method reduces the resolution factorby around one half, representing around 50% decrease in critical dimension as compared with conventionalmeasurements. The method is very promising and opens the route to potential applications in the fields ofmicrolithography.

Multiple light scattering in metallic ejecta produced under intense shockwave compression

Jean-Eloi Franzkowiak, Patrick Mercier, Gabriel Prudhomme, and Laurent Berthe

Doc ID: 315857 Received 18 Dec 2017; Accepted 28 Feb 2018; Posted 01 Mar 2018  View: PDF

Abstract: A roughened metallic plate, subjected to an intense shock wave compression, gives rise to an expandingejecta particle cloud. Photonic Doppler Velocimetry (PDV), a fiber-based heterodyne velocimeter, isoften used to track ejecta velocities in dynamic compression experiments and on nanosecond time scales.Shortly after shock breakout at the metal-vacuum interface, a particular feature observed in many experimentsin the velocity spectrograms is what appears to be slow-moving ejecta, below the free-surfacevelocity. Using Doppler Monte Carlo (MC) simulations incorporating the transport of polarization in theejecta, we show that this feature is likely to be explained by the multiple scattering of light, rather thanby possible collisions among particles, slowing down the ejecta. As the cloud expands in a vacuum, thecontribution of multiple scattering decreases due to the limited Field Of View (FOV) of the pigtailedcollimator used to probe the ejecta, showing that the whole geometry of the system must be taken intoaccount in the calculations to interpret and predict PDV measurements.

Influence of passive facet of multilayer diffractiveoptical elements

yang hongfang and Changxi Xue

Doc ID: 318867 Received 04 Jan 2018; Accepted 28 Feb 2018; Posted 01 Mar 2018  View: PDF

Abstract: The effect of passive facet on diffraction efficiency of multilayer diffraction optical elements (MLDOEs) wasanalyzed and the mathematical model of polychromatic integral diffraction efficiency affected by passive blazedfacet for MLDOEs is presented. We found passive facet could cause a significant reduction in polychromatic integraldiffraction efficiency in the working waveband. The reduction of diffraction efficiency is quantitatively describedby the shielding effect, which is caused by the sidewall slope of sawtooth-shaped MLDOEs. Through rigorouscalculations, our shielding model is consistent with the numerical results. The Analysis results can be utilized forfabrication of MLDOEs and our shielding model of passive facet can be applied to predict the optical performance ofMLDOEs and refractive-diffractive hybrid imaging optical systems.

Optical measurements of dynamic wetting and dynamic contact angle

LIPING HOU, XIAODONG YANG, Jianxia Qi, and RunCai Miao

Doc ID: 315172 Received 07 Dec 2017; Accepted 28 Feb 2018; Posted 28 Feb 2018  View: PDF

Abstract: We present a method of optical measurement of the dynamic wetting, the dynamic contact angles and the changes of the dynamic curved liquid surface corresponding to dynamic wetting, which uses the critical light reflection from dynamic curved liquid surfaces due to the dynamic wetting. When an expanded and collimated laser beam impinges on the dynamic curved liquid surfaces at glancing incidence, the special reflection patterns, which corresponding to the different states of the dynamic wetting, are observed. Based on an analytic relation between the bright /dark region width and the height of down/ up curved liquid surfaces, we proposed a method of optical measurement. In the experiment, a rod such as iron, copper and aluminum is immersed at constant speed(u=0.2mm/s)into a liquid bath and withdrawn out gradually. We measured the changing curve of the dynamic contact angle of the iron rod and the characterization of the dynamic curved liquid surface of the iron rod.

Correction of interferogram data acquired using focalplane FT-IR spectrometer system

CONG GAO, Mao Jianhua, and Chen Ren

Doc ID: 313672 Received 24 Nov 2017; Accepted 28 Feb 2018; Posted 28 Feb 2018  View: PDF

Abstract: Interferogram data acquired using the focal plane of a Fourier transform infrared (FT-IR) spectrometer acquisitionsystem was processed for the purpose of calculating the noise equivalent spectral radiation. This study introducesthe composition of the acquisition system based on a focal plane FT-IR spectrometer and analyzes the cause ofordinate drifting and abscissa shifting. The influence of these problems on system noise is analyzed quantitativelythrough mathematical calculations. Correction algorithms and methods are introduced to solve these problems.These can correct the error of interferogram data based on the FT-IR acquisition system.

GaN-based mid-power flip-chip LED with high -3dB bandwidth for visible light communications

Zheng Zhou, Bing Yan, xuejin ma, Dongdong Teng, Lilin Liu, and Gang Wang

Doc ID: 319536 Received 18 Jan 2018; Accepted 28 Feb 2018; Posted 01 Mar 2018  View: PDF

Abstract: Through directly flip-chip soldering three mid-power LED chips with periodic micro-via-holes on ceramic substrates, -3dB modulation bandwidths of 49.9MHz, 58.8MHz and 25MHz are obtained at the driving current of 170mA. To the best of our knowledge, these are the reported highest -3dB bandwidth values for flip-chip power-type LEDs at the low bias current levels. Moreover, good radiant powers are also achieved, and are 180.2mW, 168.8mW and 3.8mW at 150mA, respectively. Featured by gold wire free, the fabricated FC-LEDs could offer an opportunity to miniaturize the package volume of an LED module for illumination and free-space high speed VLC dual-usage applications.

Gain investigation of Perylene Red-doped PMMA for Stimulated Luminescent Solar Concentrators

Md Rejvi Kaysir, Simon Fleming, and Alexander Argyros

Doc ID: 320399 Received 22 Jan 2018; Accepted 28 Feb 2018; Posted 28 Feb 2018  View: PDF

Abstract: Luminescent solar concentrators (LSCs) utilizing stimulated emission by a seed laser are a promising approach to overcome the limitations of conventional LSCs, with a significant reduction of the photovoltaic material. In our previous work, we demonstrated the principle of a stimulated-LSC (s-LSC) and correspondingly developed a model for quantifying the output power of such a system taking into account different important physical parameters. The model suggested Perylene Red (PR) dye as potential candidate for s-LSCs. Here, we experimentally investigate the gain of PR-doped PMMA required for s-LSCs using a single pump wavelength (instead of the solar spectrum) as a proof of principle. The results found from the experiment are well-matched with the previously developed numerical model except for gain saturation which occurs at a comparatively small seed laser signal power. To investigate the gain saturation, two approaches were taken: investigating (i) spectral hole burning and (ii) triplet state absorption. Experimental investigation of spectral hole burning with PR dyes showed a small effect on the gain saturation. We developed a general state model considering triplet state absorption of the PR-dyes for the second approach. The state model suggests that the PR dyes suffer from significant triplet state absorption loss, which obstructs the normal operation of the PR based s-LSC system.

A Two Cores Single Polarization Optical Fiber with aLarge Hollow Coated bimetallic Layer

Qu Hongkun, Fengjun Tian, shanshan chen, yingjie zhang, Luo Jianfeng, Li Li, Xinghua Yang, and Jianzhong Zhang

Doc ID: 314903 Received 04 Dec 2017; Accepted 27 Feb 2018; Posted 27 Feb 2018  View: PDF

Abstract: A two cores hollow optical fiber for polarizer based on surface plasmon resonance(SPR) is proposed and studied bythe full-vector finite element method. The proposed fiber consists of two circular cores, inner cladding, outercladding, and a large central air hole. The two cores are arranged symmetrically in inner cladding and couple weaklywith the air hole. There are no cross-talk between cores because they are insulated by the air hole. A nano-dimensionAg/Au bimetallic layer can be coated on the inner surface of the central air hole to support SPR. The numerical resultsshow that single-polarization of two cores are achieved simultaneously at the wavelength of 1.310μm, due to strongcoupling between TM mode and surface plasmon polariton(SPP) mode. The extinction ratio 40.90dB with 3mmlength is obtained, and the confinement loss of TE mode is 0.19dB/cm. Moreover, the resonance wavelength istunable by varying the refractive index of materials in central air hole. The scheme is helpful of coupling all-fiberpolarizer with multi-cores PMFs, and makes possible application in in-fiber integrated interferometric sensors withpolarization maintaining.

Generation of single mode, high power supercontinuum from 1.57 to 12μm with cascaded fluoride and chalcogenide fibers

Kaiwen Guo, Ramon Martinez, Genevieve Plant, LUKASZ MAKSYMIUK, Brian Janiszewski, Michael Freeman, Robert Maynard, Mohammed Islam, Fred Terry, Robert Bedford, Ricky Gibson, Francois Chenard, Stephane Chatigny, and Agustin Ifarraguerri

Doc ID: 318046 Received 19 Dec 2017; Accepted 27 Feb 2018; Posted 28 Feb 2018  View: PDF

Abstract: We generate a supercontinuum spectrum ranging from 1.57 to 12μm (20dB bandwidth) with a soft glassfiber cascade consisting of ZBLAN fiber, As2S3 fiber and As2Se3 fiber pumped by a nanosecond thuliumMOPA system. The highest on-time average power generated is 417mW at 33% duty cycle. We observe anear diffraction limit beam quality across the wavelength range from 3 to 12μm, even though the As2Se3fiber is multimode below 12μm. Our study also shows that parameters of the As2Se3 fiber, such as numericalaperture, core size and core/cladding composition, have significant effects on the long wavelengthedge of the generated SC spectrum. Our results suggest that the high numerical aperture of 0.76, low lossAs2Se3/GeAs2Se5 core/cladding material all contribute to broad SC generation in LWIR spectral region.Also, among our results, 10μm core diameter selenide fiber yields the best spectral expansion while the12μm core diameter selenide fiber yields the highest output power.

Design methods to generate computer hologram forimproving the image quality

Dapu Pi, Juan Liu, Xinhui Duan, Yu Han, and Pan He

Doc ID: 319418 Received 19 Jan 2018; Accepted 27 Feb 2018; Posted 28 Feb 2018  View: PDF

Abstract: In order to suppress the speckle noise on holographic display, we propose two design methods to initialize the phase to generatecomputer hologram illuminating by partially coherent light. We introduce initial phase of the image in consideration of the relationshipof gray value among the adjacent pixels when generating computer hologram. After simulations, we compare those two methods andconclude that one of the methods is better than the other in terms of running speed or the quality of reconstructed image. Finally, weperform experiments to verify the theory. It is expected that those methods can greatly enhance the quality of reconstructed imagesand could be widely applied in the holographic field in the future.

An eightfold optical encoder with high-density grating

Jili Deng, Xiaona Yan, Chunlong Wei, Yancong Lu, Minkang Li, xiansong Xiang, Jia Wei, and Changhe Zhou

Doc ID: 320028 Received 18 Jan 2018; Accepted 27 Feb 2018; Posted 28 Feb 2018  View: PDF

Abstract: A novel grating interferometer configuration with eight-fold optical subdivision to achieve ultra-high resolution using a special symmetrical prism is proposed. The optical subdivision is enhanced by four times compared to traditional linear optical encoders. In this work, we take advantage of a high linear density grating of 1780 lines/mm, which is combined with an eight-fold optical subdivision configuration for the first time in optical encoders. As a result, a high resolution of 68.6 pm is achieved. The apparatus adopts a symmetrical measurement configuration to reduce the error arising from environmental fluctuations. The verification experiments involve high optical subdivision, long- and short-range displacement measurement and stability, with all results compared to those obtained with a commercial interferometer. The excellent agreement of the results demonstrates the effectiveness of our proposed system.

Terahertz Detection of Alcohol Using Photonic CrystalFiber Sensor

Jakeya Sultana, Mr. Islam, Kawsar Ahmed, Alex Dinovitser, BRIAN W.-H. NG, and Derek Abbott

Doc ID: 320081 Received 17 Jan 2018; Accepted 26 Feb 2018; Posted 28 Feb 2018  View: PDF

Abstract: Ethanol is widely used in chemical industrial processes as well as in the food and beverage industry.Therefore methods of detecting alcohol must be accurate, precise and reliable. In this content, a novelZeonex based photonic crystal fiber (PCF) has been modelled and analysed for ethanol detection in terahertzfrequency range. A finite element method based simulation of the PCF sensor shows a high relativesensitivity of 68.87% with negligible confinement loss of 7.79 10􀀀12 cm􀀀1 at 1 THz frequency andx-polarization mode. Moreover, the core power fraction, birefringence, effective material loss (EML), dispersionand numerical aperture (NA) are also determined in the terahertz frequency range. Owing to thesimple fiber structure, existing fabrication methods are feasible. With the outstanding waveguiding properties,the proposed sensor can potentially be used in ethanol detection, as well as polarization preservingapplications of terahertz waves.

Packaging of InGaN stripe-shaped light-emittingdiodes

Yonghua Park, Kwai Hei Li, Wai Yuen Fu, Yuk Cheung, and H. Choi

Doc ID: 318913 Received 11 Jan 2018; Accepted 26 Feb 2018; Posted 28 Feb 2018  View: PDF

Abstract: We demonstrate the fabrication of InGaN/GaN stripe-shaped LEDs in flip-chip packaging (FC-LED) and verticallymountedpackaging (VM-LED). Compared to conventionally-packaged LEDs (CM-LED), these packaging schemesenhance light output and emission divergence in ways favorable for general lighting applications. The FC-LED cansustain efficiency at high current operations due to effective heat sinking, while the VM-LED excels at lightextraction efficiency due to the exposure of two large emission surfaces. Together with the properties of lowluminous exitance and emission uniformity, the stripe-shaped LEDs are ideal for the assembly of luminaires. AnLED light tube comprising a continuous linear array of 10 stripe-shaped LED chips has been assembled. The opticalperformance of the light tube is compared with another light tube assembled with conventional square-shaped LEDchips (with and without external diffuser) by confocal microscopy. It is found that emission uniformity of thestripe-shaped LED tube is significantly improved, with a three-fold increase in illumination area, without efficiencyloss associated with diffusers.

Optimal bandwidth and systematic error offull-Stokes micropolarizer arrays

Andrey Alenin, Israel Vaughn, and J. Scott Tyo

Doc ID: 319498 Received 11 Jan 2018; Accepted 26 Feb 2018; Posted 26 Feb 2018  View: PDF

Abstract: In this paper, we present the first in-depth analysis of the bandwidth trade-offs, error performance, and noiseresiliency of full-Stokes micropolarizer array (MPA) designs. By applying our Fourier domain tools that providea systematic way for arranging information carriers and allocating bandwidth, we develop a number of new full-Stokes MPA layouts and compare them to the existing full-Stokes MPAs in the literature, all of which use 2 2pixel unit-cells to build the MPA. We compare the reconstruction accuracy afforded by these traditional designswith the generalized 2 L family of MPAs, a 33 tiling, as well as a 223 layout that uses multiple snapshotsand trades off temporal resolution for spatial resolution. Of those systems, the hybrid spatiotemporally modulated2 2 3 MPA provisions the most bandwidth and provides the highest reconstruction accuracy, while themodified 2 L family remains the best performing single-snapshot MPA. Additionally, we study the degradationof reconstruction accuracy under presence of systematic error in MPA fabrication. We find that reducing theamount of correlated error is by far the largest factor in ensuring robust performance.

High-speed CGH based on Resource Optimization for Block-based Parallel Processing

Young-Ho Seo, Dong-wook Kim, and Youn-Hyuk Lee

Doc ID: 318415 Received 27 Dec 2017; Accepted 26 Feb 2018; Posted 26 Feb 2018  View: PDF

Abstract: A huge amount of computation is required to generate a hologram using a computer. In order to speed up the computer generated-hologram (CGH) operation, we use parallel programming technique using GPGPU (Global Purpose Graphic Processing Unit). In this paper, we propose three techniques to improve CGH performance in the condition using GPU. The first is to remove the memory bottleneck by allocating shared memory and a dedicated thread for this process, and the second is to optimize the block allocation within the GPU using a hologram pixel-based method. The third is to increase the computation time by minimizing the idle region by using multiple threads of host processor and device. When these three techniques were implemented in the GTX 1080Ti GPU, it took 25.05ms to generate the HD digital hologram with 10K object points, and compared to the previous researches, the performance improvement was at least 1.56 times up to 216.71 times.

The development of optical defect inspectionalgorithm based on active contour model for largesteel roller surfaces

Jun Yang, Xuekun Li, Jirui Xu, Yuzhong Cao, Yun Zhang, Liping Wang, and Sheng Jiang

Doc ID: 318539 Received 27 Dec 2017; Accepted 26 Feb 2018; Posted 26 Feb 2018  View: PDF

Abstract: The on-site measurements and defect identification are of great importance for precision ground steel rollers dueto their large dimension and weight. Besides the dimensional error, form accuracy, surface roughness andsurface/sub-surface cracks, there also exists optical defect requirement for steel roller surface, e.g. speckles,chatter marks, or feed traces. Since rollers with optical defects will always duplicate the defect patterns onto themetal sheet or foil during rolling, it is necessary as well as significant to scrutinize roller surface after grinding. Inindustrial practice, the defects are inspected mainly by experienced engineers through naked eyes along particulardirections and under appropriate illumination condition, which is usually objective and inconsistent. In this paper,a machine vision system is developed to add on the roller grinder, which is capable to acquire the roller surfaceimage with high and consistent quality. In addition, to identify the defects with fuzzy boundaries, intensityinhomogeneity and complex background textures, an improved segmentation algorithm is developed based onactive contour model without edges. Furthermore, the comparison of the proposed algorithm with Chan-Vesemodel and Local Binary Fitting (LBF) model is carried out. And the comparison proves that the proposed methodpossesses higher capability for fuzzy and inhomogeneous defect identification and consumes less computationaltime.

Optical phase conjugation of diffused light with infinite gain by using gated two-color photorefractive crystal LiNbO3:Cu:Ce

Guanghui Pang, Honglin Liu, pei hou, Mu Qiao, and Shensheng Han

Doc ID: 318677 Received 03 Jan 2018; Accepted 26 Feb 2018; Posted 27 Feb 2018  View: PDF

Abstract: Light focusing in multiple scattering circumstance is important in biomedical imaging, manipulation and therapy. Up to now, many traditional photorefractive crystals have been used to generate an optical phase conjugated wave front in an analogue time-reversed optical focusing technology. But, due to erasure of a volume hologram during a reading procedure, the optical energy gain can never reach unity, which limits its application in delivering more energy into a target area. In this work, we investigated a gated two-color photorefractive crystal LiNbO3:Cu:Ce to generate optical phase conjugation of diffused light with infinite gain.

Vibration identification based on Levenberg-Marquardt optimization for mitigation in adaptiveoptics systems

Kangjian Yang, ping yang, Shanqiu Chen, Shuai Wang, WEN Lianghua, Lizhi Dong, Xing He, boheng lai, xin yu, and Bing Xu

Doc ID: 318068 Received 19 Dec 2017; Accepted 26 Feb 2018; Posted 05 Mar 2018  View: PDF

Abstract: When high performance expected, vibrations are becoming a burning issue in adaptive optics systems. Formitigation of these vibrations, in this paper, we propose a method to identify vibration model. The non-linear leastsquares algorithm named Levenberg-Marquardt method is adapted to acquire the model parameters. Theexperimental validation of the high performance of vibration mitigation associated with our identification methodhas been accomplished. Benefiting from this method, vibrations have been significantly suppressed using linearquadratic Gaussian control, where the root-mean-square of the residual vibrations has been down to a portion ofμrad. Moreover, the experimental results show that with the model identified, vibrations ranging from wide lowfrequencyperturbation to high-frequency vibration peaks can be dramatically mitigated, which is superior toclassical control strategies.

A stigmatic broadband imaging spectrometer with high NA

Lei Yu, Hui Xue, and Jiexiang Chen

Doc ID: 312959 Received 10 Nov 2017; Accepted 25 Feb 2018; Posted 26 Feb 2018  View: PDF

Abstract: A new advanced Dyson spectrometer has been presented for broadband stigmatic imaging. The spectrometer, with large axial spaces and lateral separation perpendicular to the axis between the slit, the imaging plane and the hemispherical lens, is composed of a thin hemispherical lens and two spherical lenses in the same material, and a reflection concave grating. The advanced optical system maintains excellent optical performances and decreases inherent stray light of the concentric spectrometer with high NA, which owns better engineering applicability.

Dual-wavelength dispersion characterization ofconfocal Fabry-Perot interferometers

Changbo SONG, Antonella Boselli, Alberto Porzio, Nicola Spinelli, yiming zhao, and Xuan WANG

Doc ID: 315423 Received 27 Dec 2017; Accepted 24 Feb 2018; Posted 26 Feb 2018  View: PDF

Abstract: Optical resonators simultaneously resonating at different wavelengths are of interest in passive as well as active optical cavities.Dual wavelength lasers, optical parametric amplifiers and spectrometers e.g. in high spectral resolution lidar (HSRL) are effectivelyimproved by employing multiply resonant cavities. In particular, HSRL allows to measure aerosol optical properties without a-priorihypotheses. Here we analyze optical dispersion in a HSRL prototype, based on a confocal Fabry-Perot interferometer (CFPI),developed to work at 532 nm (the lidar excitation wavelength). The presence of dispersion should be accounted for when realizing aneffective HSRL because a second beam is required to obtain sufficient locking stability. We have performed an experiment in order tomeasure the dispersion contributions coming from cavity mirror coating and air, and evaluate the stability of the transmission peaks inorder to optimize the performances of HSRL.

Demonstration of an Optical Directed Half-subtracterUsing Integrated Silicon Photonic Circuits

zilong liu, Yongpeng Zhao, Huifu Xiao, Lin Deng, Yinghao Meng, Xiaonan Guo, Guipeng Liu, Yonghui Tian, and Jianhong Yang

Doc ID: 318558 Received 27 Dec 2017; Accepted 23 Feb 2018; Posted 27 Feb 2018  View: PDF

Abstract: An integrated silicon photonic circuit consisting of two silicon microring resonators (MRRs) is proposed andexperimentally demonstrated for the purpose of half-subtraction operation. The thermo-optic modulation schemeis employed to modulate the MRRs due to its relative simple fabrication process. The high and low levels of theelectrical pulse signal are utilized to define logic 1 and 0 in electrical domain respectively, and the high and lowlevels of the optical power represent logic 1 and 0 in optical domain respectively. Two electrical pulse sequencesregarded as the operands are applied to the corresponding micro-heaters fabricated on the top of MRRs to achievetheir dynamic modulations. The final operation results of bit-wise Borrow and Difference are obtained at theircorresponding output ports in the form of light. At last, subtraction operation of two bits with the operation speedof 10 kbps is demonstrated successfully.

The confined-doped fiber for effective mode controlfabricated by MCVD process

Lei Liao, Fangfang zhang, Xinglong He, YISHA Chen, Wang Yibo, Haiqing Li, Jinggang Peng, luyun yang, Nengli Dai, and Jinyan Li

Doc ID: 314142 Received 05 Jan 2018; Accepted 23 Feb 2018; Posted 28 Feb 2018  View: PDF

Abstract: A confined-doped fiber was fabricated by modified chemical vapor deposition (MCVD) process based on refractiveindex matching technology. With the theory and experiments, we compared the confined-doped fiber and normaldoped fiber. It is found that the confined-doped fiber with the core of 35μm and 0.07 NA could achieve single modeoutput and improve the beam quality from 2.8 to1.5 in the fiber laser. Meanwhile, it still possesses high laserefficiency and have good stability of beam quality with the increase of pump power. It suggests that theconfined-doped fiber with MCVD process maybe the key material for high power fiber laser with excellent beamquality.

Phase and amplitude beam shaping with intelligent input plane and Fourier plane phase modifications

Chensheng Wu, Jonathan Ko, John Rzasa, Daniel Paulson, and Christopher Davis

Doc ID: 318726 Received 03 Jan 2018; Accepted 23 Feb 2018; Posted 26 Feb 2018  View: PDF

Abstract: We find that ideas in optical image encryption can be very useful for adaptive optics in achieving simultaneous phase and amplitude shaping of a laser beam. An adaptive optics system with simultaneous phase and amplitude shaping ability is very desirable for atmospheric turbulence compensation. Atmospheric turbulence induced beam distortions can jeopardize the effectiveness of optical power delivery for directed energy systems and optical information delivery for free space optical communication systems. In this manuscript, a prototype adaptive optics system is proposed based on a famous image encryption structure. The major change is to replace the two random phase plates at the input plane and Fourier plane of the encryption system, respectively, with two deformable mirrors that perform on-demand phase modulations. A Gaussian beam is used as an input to replace the conventional image input. We show through theory, simulation and experiments that the slightly modified image encryption system can be used to achieve arbitrary phase and amplitude beam shaping within the stroke limits of the deformable mirrors. In application, the proposed technique can be used to perform mode conversion between optical beams, generate structured light signals for imaging and scanning, and compensate atmospheric turbulence induced phase and amplitude beam distortions.

Nondestructive testing of resistance spot welds usingeddy current thermography

Abdoulaye Taram, Cyrielle Roquelet, Philip Meilland, Thomas Dupuy, Christine Kaczynski, JEAN-LUC BODNAR, and Thierry Duvaut

Doc ID: 319007 Received 04 Jan 2018; Accepted 23 Feb 2018; Posted 26 Feb 2018  View: PDF

Abstract: The paper presents the use of eddy current thermography for detecting cracks in resistance spot welds. Thesample is a three-sheet stack-up joined together by welding spots. Inductive Helmholtz coil is used for heating upthe sample and the thermal response of each spot is monitored using a cooled InSb camera. The sequence of imagescaptured is processed using pulsed phase thermography technique. Phase image is completed with supplementaryfiltering operation to allow outlining defects. The result was confirmed with confocal microscopy inspection.

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

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

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

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

Research on characteristics of symmetric optothermal microactuators

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

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

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

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

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

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

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

Dual-plane slightly off-axis digital holography basedon a single cube beam splitter

MIGUEL LEON-RODRIGUEZ, Juan Rayas, Raul Cordero, Amalia Martinez Garcia, Adrián Martínez-González, Alejandro Téllez-Quiñones, Pedro Yañez-Contreras, and Orlando Medina

Doc ID: 314462 Received 28 Nov 2017; Accepted 22 Feb 2018; Posted 27 Feb 2018  View: PDF

Abstract: In order to recover the holographic object information, a method based on the recording of twodigital holograms, not only at different planes but also in a slightly off-axis scheme, is presented.By introducing a π -phase shift in the reference wave, the zero order diffracted term and the twinimageare removed in the frequency domain, during the processing of the recorded holograms.We show that the zero-order elimination by the phase-shifted holograms is better than workingwith weak order beam and average intensity removal methods. For recording experimentallytwo π-shifted holograms at different planes slightly off-axis, a single cube beam splitter is used.Computer simulations and experimental results, carried out to validate our proposal, show ahigh accuracy of π/14 that can be comparable with phase-shifting digital holography. For highfringe spacing, our proposal could be applied in electron holography, avoiding high voltage in abiprism.

Spectral-differential-based unmixing for multispectral photoacoustic imaging

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

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

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

Active Underwater Detection with an Array of Atomic Magnetometers

Cameron Deans, Luca Marmugi, and Ferruccio Renzoni

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

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

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

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

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

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

Three-mirror anastigmat for cosmic microwave background observations

Stephen Padin

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

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

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

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

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

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

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

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

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

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

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

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

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

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


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

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

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

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

Rajab Nasehi and Mohammad Mahmoudi

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

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

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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