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Intelligent and Automatic Wavelength Calibration Method

qing song, Tian Zhang, Zhihui Wang, Shihui Zhang, and Lu Yang

Doc ID: 326589 Received 21 Mar 2018; Accepted 16 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: Wavelength calibration is carried on before the spectrometer being used normally. The usual calibration process is to measure a standard light source of known wavelength, such as the mer- curyargon lamp. The spectral lines formed by the standard light source is divided to find the peak value, and then the peak value of the light source is matched with the wavelength of the standard light source. At present, the calibration of the spectrometer needs to be carried out with human intervention, which requires a lot of work and the accuracy is not high. In our previous work, we proposed an efficient and accurate peak finding method and matching method. This paper will expand on this basis to illustrate a new intelligent and automated wavelength calibra- tion method. In terms of peak searching, we discussed the implementation and defects of the maximum, DCT, GMM, Polynomial fitting methods; we compared the maximum linear match- ing method with the maximum matching method and proposed the advantages of our method. Our experiments show that spectrum segmentation and peak-seeking methods based on spec- tral energy can effectively solve the problem of segmentation and peak seeking in wavelength calibration, and is superior to other fitting methods. The matching method combining Hough transform and RANSAC can effectively solve the matching problem in wavelength calibration without manual intervention. In addition, both the average accuracy and the average recall rate exceed the traditional manual matching method and the maximum linear matching method.

Quadrant response model and error analysis of fourquadrantdetectors related to non-uniform spot andblind area

Jun Zhang, Qian Weixian, Guohua Gu, Kan Ren, Qian Chen, Chen Mao, GuiXia Cai, ZeWei Liu, and Liwei Xu

Doc ID: 326924 Received 26 Mar 2018; Accepted 16 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: In the system of tracking and detection based on the four-quadrant detector (4-QD), the energy distribution of the incidentspot and the blind area of the photosensitive surface will affect the location accuracy. The current model of the spot is basedon the ideal circular Gauss spot, which makes the error caused by the spot shape easily ignored. In this paper, the model ofthe spot energy distribution is improved, which can adapt to the elliptical Gauss distribution, and the width of the blind areais added to the response models of the detector. So that the output of each quadrant and the error of the localizationalgorithm can be calculated more accurately. The simulation results show that the measurement accuracy of 4-QD decreasewith the increase of the blind area, the shape and the inclination of the light spot. In the experiment, we first verify thecorrectness and practicability of the improved model of the spot energy distribution, and then the improved model is provedto be able to make the response and error calculation more accurate.

Combining and collimation of RGB laser beams with atransmissive resonance domain diffractive optics

Omri Barlev and Michael Golub

Doc ID: 327983 Received 09 Apr 2018; Accepted 16 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: Resonance domain diffractive optical elements for combining of RGB laser beams into a single collimated beamwere designed, fabricated and experimentally investigated. The input RGB beams were angular separated up totenths of degrees and set in nearly Bragg arrangement for high diffraction efficiency. Single resonance domaindiffractive lens delivered both beam combining and collimation functions with reasonable residue divergence. Theresonance domain diffraction grating delivered diffraction-limited residue divergence in combining of collimatedRGB beams. Optical experiments with fiber-coupled RGB lasers and e-beam-fabricated beam combiners proved lowresidue beam divergence, high polarization extinction ratio and total measured diffraction efficiency about 80%.

Wavelength-tunable all-fiber mode-locked laser basedon supermode interference in a seven-core fiber

xiaogang Jiang, BAREREM-MELGUEBA MAO, yizhen Wei, Daru Chen, Lijuan She, Gaofeng Feng, and Junyong Yang

Doc ID: 334378 Received 04 Jun 2018; Accepted 16 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: A wavelength-tunable all-fiber mode-locked Erbium-doped fiber laser has been proposed and realized by using asupermode interference filter (SMIF). The SMIF is fabricated by splicing a segment of seven-core fiber (SCF) to twostandard single mode fibers. Since two supermodes of the propagating light are excited in the SCF, the transmissionspectrum of the SMIF shows clean broadband comb-shape characteristic. By bending the SMIF in the proposedmode-locked laser, the output spectrum can be continuously tuned in a wavelength range up to 22 nm whilekeeping mode-locking operation. The self-starting laser produces 0 fs pulses with a spectral width of 14 nm.

Laser reflection differential confocal large-radius measurement for concave surfaces

Yang Xiao, Lirong Qiu, and Weiqian Zhao

Doc ID: 331945 Received 16 May 2018; Accepted 15 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: In this paper, a laser reflection differential confocal large-radius measurement method is proposed for concave surfaces (RDCLM). Based on the property that the zero point of the axial intensity curve precisely corresponds to its focus in a laser differential confocal system (LDCS),RDCLM precisely identifies the positions of the surface vertex of the test lens and the last surface vertex of the objective lens, and obtains the moving distance L of the test lens. And finally, RDCLM obtains an accurate radius of curvature (ROC) of the test lens using L, the focal length f of the objective lens and the system aperture D. Preliminary theoretical analysis and experimental results show that the RDCLM relative measurement uncertainty is 0.003% for a concave lens with a ROC of -5,003 mm.

Fabrication of a multilayer tissue-mimicking phantomwith tunable optical properties to simulate vascularoxygenation and perfusion for optical image technology

Guangli Liu, KUIMING HUANG, jia min, Cedar Liu, Shuwei Shen, Jialuo Li, Erbao Dong, Paul Lemaillet, David Allen, and Ronald Xu

Doc ID: 325101 Received 01 Mar 2018; Accepted 15 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: Due to convenient use and easy storage, vast research has been carried out to fabricate tissue-mimicking phantoms toassess and validate the performance of optical imaging devices. However, there is little research on the use of multilayertissue phantoms for optical image technology, although their structure is closer to that of real skin tissue. In this work,we design, fabricate, and characterize multilayer tissue-mimicking phantoms that contain an epidermis, a dermis, and ahypodermis with a morphological mouse ear blood vessel. Each tissue-mimicking phantom layer is characterizedindividually to match specific skin tissue layer characteristics. The thickness, optical properties (absorption coefficientand reduced scattering coefficient), oxygenation and perfusion of skin are the most critical parameters for diseasediagnosis and for some medical equipment. These phantoms can be used as calibration artifacts and help evaluateoptical imaging technologies.

Experiences with a three-current ionization chamberas primary detector standard for absolute calibrationin space

Robert Schaefer, Gerhard Schmidtke, and Raimund Brunner

Doc ID: 330544 Received 27 Apr 2018; Accepted 14 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: Context. With ISS-SOLAR-SolACES a new approach in terms of calibrating solar spectral irradiance(SSI) data was validated during the mission period from 2008 to 2017: an ionizationchamber (IC) as primary detector standard, operated in space, allowed daily calibration measurements.Issue. Though primary photo-ionization efficiencies and higher-order ionization effects fromphotoelectrons are constant with time, filter transmissions and signal contributions from solarX-rays are to be determined for the SSI data evaluation requiring a deeper investigation.Aims and Methods. The experiences made with ionization chambers in the laboratory andaboard the ISS-SOLAR-SolACES mission are presented. It includes the determination of higherorderionization effects, the measured transmission of the filters with time, and the treatmentof the solar soft X-ray background. Recommended combinations of ionization chamber fillinggases and filter materials as well as laboratory and in-space measurements will provide correctionprocedures for different levels of solar activity to achieve further improvement of SSI dataaccuracy in the spectral range from 1nm to 133 nm.Results and Perspectives. The usage of the ionization chamber technology aims for establishingan absolute SolACES-type calibration equipment in space providing reference SSI data setsin solar and solar-terrestrial science as well as in related applications such as GNSS signalevaluation.

Spherical-harmonic-transform-based fast calculation algorithm for spherical computer-generated hologram considering occlusion culling

Yusuke Sando, Daisuke Barada, Jackin Boaz Jessie, and Toyohiko Yatagai

Doc ID: 331236 Received 09 May 2018; Accepted 13 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: The diffraction integral onto a spherical surface is discussed in the three-dimensional (3D) Fourier domain of the 3D object used. The diffraction integral is expressed in the form of the convolution integral between the partial Fourier components of the 3D object and the kernel function defined on the sphere. This two-dimensional convolution on the sphere can be calculated rapidly based on the convolution theorem by performing spherical harmonic transform instead of Fourier transform. This paper presents a detailed derivation of this diffraction integral and analyzes the sampling pitch required for handing the data on the sphere. Our proposed method is verified using a simple simulation of Young's interference experiment. Moreover, a numerical simulation with a more complicated 3D object is demonstrated. Our proposed method speeds-up the calculation of the diffraction integral by more than 1,800 times compared with the direct calculation method.

Generation of high conical angle Bessel-Gauss beams with reflective axicons

Pauline Boucher, Jesus Hoyo, Cyril Billet, Olivier Pinel, Guillaume Labroille, and Francois Courvoisier

Doc ID: 330339 Received 25 Apr 2018; Accepted 13 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: We report the generation of Bessel-Gauss beams of high conical angle, up to 35 degrees, using reflective off-axis axicons and a magnification optical system. We experimentally characterize the beams with three-dimensional scans. The high precision of fabrication of the axicons in the vicinity of the axicon singularity allows us to generate a beam with intensity distribution close to analytical description.

Enhanced circular dichroism of crossed nanorods with nanowire

mingyan wang, fei wang, Yu Qu, Tiankun Wang, YuYan Chen, Yu Bai, and Zhongyue Zhang

Doc ID: 328139 Received 11 Apr 2018; Accepted 13 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: Circular dichroism (CD) is a signal that characterizes the optical properties of chiral structures. Structures with intense CD signals have valuable applications in molecular chemistry, pharmaceuticals, and biosensing. This work proposes the use of a nanowire to increase the CD signal of crossed nanorods. The separation of resonant wavelengths of transmission under left-handed and right-handed circular polarization incidence (LCP and RCP) increases because the electric interaction between the upper nanorod and nanowire under LCP incidence is different from that under RCP incidence. The increased separation of resonant wavelengths, in turn, enhances the CD signals. In addition, two new CD modes appear, and these modes can be tuned by changing the structural parameters of the proposed structure. The present results will guide the design of plasmonic chiral nanostructures for enhancing the CD signal.

Elliptical Airy Beam

YONG ZHA, Kaikai Huag, Binjie Liu, MINGLI SUN, Huizhu HU, Xian Zhang, BOCHENG ZHU, and Xuanhui Lu

Doc ID: 328353 Received 16 Apr 2018; Accepted 13 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: We found a new type of noncircular symmetrical Airy beam called Elliptical Airy Beam(EAB). Using simple Single pixel checkerboard hologram method, we achieved EAB in experiment. We observed its unique property of double focusing and vertical energy flow towards long axis end points during propagation. These particular properties will have wide application fields.

Batch-producible MEMS fiber-optic Fabry-Perotpressure sensor for high-temperature application

Ping-gang Jia, Hao Liang, guocheng fang, JIang Qian, Fei Feng, Ting Liang, and Jijun Xiong

Doc ID: 331417 Received 10 May 2018; Accepted 13 Jul 2018; Posted 13 Jul 2018  View: PDF

Abstract: A fiber-optic Fabry–Perot pressure sensor based on micro-electro-mechanical system (MEMS) and CO2 laser fusiontechnology is developed and experimentally demonstrated for high-temperature application. The sensing headsare batch-fabricated by anodically bonding the micromachined Pyrex-glass wafer and local gold-plated siliconwafer. The separated sensing head and the single-mode fiber are fused together to form the Fabry-Perot cavityusing the CO2 laser. In order to improve the measurement accuracy in high temperature environment, a fiber Bragggrating is used as a temperature sensor for temperature decoupling. The experimental results show that the fiberopticFabry–Perot pressure sensor has a maximum nonlinearity of 0.4%. The maximal error of the pressure aftertemperature decoupling is less than 1.05% over pressure range 0-0.5MPa and temperature range of 20-350 °C. Thebatch fabrication technology makes the sensors low cost and high uniformity.

Eye-safe fiber laser for long range 3D imaging applications

Lars Holmen, Gunnar Rustad, and Magnus Haakestad

Doc ID: 332379 Received 15 Jun 2018; Accepted 13 Jul 2018; Posted 13 Jul 2018  View: PDF

Abstract: We report an all-fiber Er/Yb master oscillator power amplifier at 1.55 μm, delivering 135 μJ pulses with 6 ns duration (FWHM) at 100 kHz pulse repetition frequency, limited by stimulated Brillouin scattering. The output contains 1 % amplified spontaneous emission, and has a beam quality of M²=1.1. By seeding with a high power distributed feedback laser diode, only two fiber amplification stages are needed, which represents a low overall system complexity compared to reported sources of similar performance. With an optical-to-optical efficiency of 29 % and a robust alignment-free design, the source is well suited for field applications in 3D imaging with several km range, and we present results from using it in an in-house developed scanning lidar system.

Development of a tunable diode laser sensor for COconcentration analysis at laboratory-scale conditionsfor in situ combustion tests of heavy crude oils

Juan Duque Posada, Sebastian López Gómez, and Alejandro Molin

Doc ID: 334650 Received 07 Jun 2018; Accepted 13 Jul 2018; Posted 13 Jul 2018  View: PDF

Abstract: A tunable diode laser-based sensor is reported to monitor carbon monoxide (CO) concentration under conditionssimilar to those of laboratory-scale tests used to characterize the behavior of a heavy crude oil during in situcombustion (ISC). The sensor uses a DFB diode laser operating over the spectral range of the rotational transitionR(11) of the first overtone, wherein simulations of spectral absorption bands for CO, CO2 and H2O showed minimalspectral interference. The absorption spectra were calculated using the HiTran 2008 database at temperaturesvarying between 150°C and 800°C, pressures from 1 atm to 5 atm and the typical concentration of major species inISC characterization experiments. CO-concentration measurements were conducted at ambient temperature andpressure in a static glass cell of borosilicate with a pathlength of 3.81 cm, to validate the CO sensor architectureunder controlled laboratory environments. The calibration curve for CO obtained by quantifying the opticaldensity at the line center of R(11) for a molar-concentration range between 0.7% and 3.4% demonstrated a linearresponse (coefficient of determination of 0.9986). Experiments at 4 atm and 600 K were carried out in a customdesignedoptical chamber, which has two optical wedged sapphire windows (2°) to avoid the etalon effect. COabsorptionspectra were validated by a comparative study with the HiTran database, while a calibration-freemethodology using scanned-wavelength direct absorption was investigated for future characterizing experimentsof ISC. Signal to noise ratios (SNRs) were above 40 in the optical chamber and higher than 14 in the glass cell. TheTDL sensor was also successfully validated during real ISC experiments of a Colombian heavy crude oil. Thecalibration and oxidation experiments showed the potential of TDL-based sensors in the region of 2.3 μm for noninvasive,real-time and in situ measurements of carbon monoxide generated at similar conditions to those of labscaleexperimental tests of ISC.

Wideangle Filters Based on Nanoresonators for the Visible Spectrum

Igor Leonardo Gomes de Souza, Vitaly Rodriguez Esquerre, and Davi Rego

Doc ID: 332653 Received 29 May 2018; Accepted 12 Jul 2018; Posted 13 Jul 2018  View: PDF

Abstract: We present a design for a highly efficient and omnidirectional color selective filter for the visible spectrum, based on a Fabry-Perot metal-dielectric-metal nanoresonator. The filter can have the same color transmitted in a range of incident angles from 0⁰ up to 60⁰ for TM polarization. The dielectrics used for each color filter are carefully chosen so that the angle-insensitive resonance conditions are satisfied while achieving transmission values from 44.3% to 78.36%. We calculated the dielectric thickness for each filter and analyzed the optimal Ag thickness for maximum transmission. The proposed filters have a simple multilayer structure and do not require complex lithographic fabrication processes.

n-GaAs/Co diode with photoresponsivity based on 3-aminorhodanine thin films

Murat Soylu

Doc ID: 331248 Received 15 May 2018; Accepted 12 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: In this work, the electrical characteristics of 3-aminorhodanine (aRh)/n-GaAs heterostructure were investigated in dark and under various illumination conditions. Although the structure shows low rectifying rate, the photocurrent in both the forward and reverse biasing increases with increasing illumination intensity. The photodiode exhibits a large detectivity (the capable of detecting visible light) approaching 3.9x1011 Jones at room temperature. On illumination with light (100 mW/cm2), the current value in aRh/n-GaAs heterostructure is 2.8 × 105 times when compared to its dark value at zero applied voltage. The obtained responsivity value at the bias of 2 V and under the illumination intensity of 100 mW/cm2 is 0.16 A/W, which is high for any organic−inorganic hybrid photodiode. Photocurrent to dark current ratio is 6.5x104. Results show that aRh/n-GaAs self-powered photodiode introduces new opportunities for dynamic systems needing partially low or zero external energy inputs.

Multiwavelength Wavefront Detection Based on a Lateral Shear Interferometer and Polarization Phase Shifting Techniques

David Serrano García, Noel-Ivan Toto-Arellano, Geliztle Parra-Escamilla, Amalia Martinez-Garcia, Gustavo Zurita, and Yukitoshi Otani

Doc ID: 330600 Received 01 May 2018; Accepted 12 Jul 2018; Posted 12 Jul 2018  View: PDF

Abstract: We present a multiwavelength analysis of a wavefront detected by a color camera and a lateral shear interferometer. The system employs polarization phase shifting techniques by rotating a linear polarizer at the output and detect the phase information through a frequency demodulation algorithm. By considering the phase modulation obtained by rotating the analyzer, a frequency filter centered on the desired peak, carries the phase and amplitude information of the detected wavefront. Theoretical approach, considering Jones Matrices of each element, and experimental results shows the feasibility of the implementation.

Integrating Cavity Device for Measuring the Optical Backscattering Coefficient In a Fluid

Ellie Figueroa, Michael Cone, Cristina Orrico, Michael Dewey, Alex Derr, Michael Twardowski, and Edward S. Fry

Doc ID: 330743 Received 03 May 2018; Accepted 12 Jul 2018; Posted 12 Jul 2018  View: PDF

Abstract: An optical instrument was developed to precisely determine the backscattering coefficient (bb) in water using a custom integrating cavity to collect light scattered in the backward hemisphere. Scattered light enters the cavity through a 1.52 mm wide aperture that is designed and oriented so as to introduce a sin(θ) weighting factor on the amount of light scattered at angle θ(i.e. the amount given by the volume scattering function β(θ) of the medium) Thus, the amount of light that can reach the detector is consistent with the spherical integration given by b_b=2π∫sin(θ)β(θ)dθ from π to π/2 (azimuthal symmetry is assumed). This allows us to directly measure the backscattering coefficient (bb) in a medium while not making any assumptions about the shape of β(θ) and/or of the scattering particulates in the medium. We present the mathematical description, design and development of this true bb meter, along with calibration methods and results of a laboratory prototype. The concave surface of the quartz aperture to the integrating cavity minimizes reflection losses; it is located perpendicular to, and in the middle of a 19 mm diameter half-cylinder channel surrounding the laser source beam. Light scattered by the hydrosol along the laser path enters the cavity through the aperture, and an output signal is recorded by a silicon diode detector interfaced to the cavity. The integrating cavity scrambles directionality so all incoming light is weighted the same. The output signal can then be expressed as a direct linear function of bb. This bb meter is the first instrument to make a direct measurement of bb with <1% accuracy and it is compatible with several modes of routine oceanic deployment.

Rigorous Bragg condition for volume holographic gratings with anisotropic distortion

Shuhei Yoshida and Shuma Horiuchi

Doc ID: 331145 Received 08 May 2018; Accepted 12 Jul 2018; Posted 12 Jul 2018  View: PDF

Abstract: Volume holograms have Bragg selectivity because of the volume effect and are used for holographic data storage (HDS), which represents next-generation optical storage. High capacity can be realized in HDS because multiple holograms recorded within the same volume can be retrieved selectively using Bragg selectivity by varying the readout conditions. However, it is inhibited to retrieve holograms via the holographic grating distortion that results from volume or refractive index changes of the medium. We therefore derived the rigorous Bragg matching condition when anisotropic distortion occurs in-plane and the thickness direction of the holographic grating. We also evaluated the effects of readout compensation with angle and wavelength adjustments based on the derived Bragg matching condition using numerical analysis and the condition’s effectiveness was clarified.

Explicit formulas for photon number discrimination with on/off detectors

Filippo Miatto, Akbar Safari, and Robert Boyd

Doc ID: 331395 Received 10 May 2018; Accepted 11 Jul 2018; Posted 12 Jul 2018  View: PDF

Abstract: Discriminating between Fock states with a high degree of accuracy is a desirable feature for modern applications of optical quantum information processing. A well-known alternative to sophisticated photon number discriminating detectors is to split the field among a number of simple on/off detectors and infer the desired quantity from the measurement results.In this work we find an explicit analytical expression of the detection probability for any number of input photons, any number of on/off detectors, and we include quantum efficiency and a false count probability. This allows us to explicitly invert the conditional probability using Bayes' theorem and express the number of photons that we had at the input in the most unbiased way possible with ready-to-use formulas. We conclude with some examples.

Design of Atom Source Collimator for CompactFrequency-Stabilized Laser

Hao Shi, Jie Ma, Xiao-feng Li, Jie Liu, and Shou-Gang Zhang

Doc ID: 327993 Received 09 Apr 2018; Accepted 11 Jul 2018; Posted 11 Jul 2018  View: PDF

Abstract: A concise laser system for optically pumped cesium beam clocks is presented. The lasers frequency is locked byfluorescence signal, produced by the interaction between cesium atomic beam and laser. A cesium oven with alonger atom source collimator, formed by an array of channels, was used to reduce the divergence angle of cesiumatomic beam. The size of cesium source collimator is 4 mm × 0.6 mm, and the cesium expenditure rate is 2.4×10-1 gper year. A dense cesium atomic flux was used to interact with the laser to generate a fluorescence signal when theoven heating temperature is not too high. The cesium beam tube could have a longer life time. The optical structureof laser system is compact. The measured frequency stability of laser is ∼4×10-11 at 10,000 s when the laserfrequency is locked in the F = 4→F′ = 5 transition of cesium D2 line. The design of atom oven and atom source maybe used in other atomic beam clocks to improve their performance.

Widely-tunable dual-wavelength operation of Tm:YLF,Tm:LuAG and Tm:YAG lasers using off-surface opticaxis birefringent filters

ERSEN BEYATLI and Umit Demirbas

Doc ID: 334651 Received 06 Jun 2018; Accepted 11 Jul 2018; Posted 11 Jul 2018  View: PDF

Abstract: In this work, we have demonstrated dual-wavelength continuous-wave laser operation in diode-end-pumped Tm:YLF,Tm:LuAG and Tm:YAG lasers. A 3-mm thick quartz birefringent filter with an optical axis 45° to the surface plane wasexploited for achieving broadly-tunable two-color laser operation. By using the different orders of the filter with varyingfilter width and free spectral range values, dual-wavelength operation has been achieved in 11, 12 and 8 differentwavelength pairs in Tm:YLF, Tm:LuAG and Tm:YAG, respectively. Fine tuning of the rotation angle of the birefringent filterenabled control of laser power in each line. To our knowledge, this is the first report of multicolor laser operation in thesegain media, and the technique used is applicable to other laser operation regimes including mode-locking.

Error performance analysis of a non-ideal photon counting array receiver system for optical wireless communication

Chen Wang, jingyuan Wang, zhiyong xu, Rong Wang, Jiyong Zhao, and Yimei Wei

Doc ID: 326622 Received 04 Apr 2018; Accepted 11 Jul 2018; Posted 12 Jul 2018  View: PDF

Abstract: In order to detect weak signal from background noise, using an array of Geiger-mode avalanche photodiode (GM-APD) as a detector is researched. Firstly, the principle of GM-APD operated in gate mode is analyzed. Based on the Poisson random process of arriving photons, the trigger probability of single GM-APD has been computed. Then according to the trigger probability, a new bit error rate (BER) model of photon counting array receiver system is built. And the expression of BER is derived based on the quantum efficiency, signal photons, background photons, dark carriers and the number of GM-APDs in array. By the BER expression, the error performance of a new photon counting array receiver system can be predicted quickly. Furthermore, the error performance of GM-APD array based system is investigated. The simulation results indicated that limiting background noise power less than signal power is necessary to system operation. After background noise is limited in the acceptable range, keeping a certain scale of GM-APDs (above 20) in array can greatly reduce the demands of transmitting power.

Ultrafast All-Optical Plasmonic Graphene Modulator

Feng Zhou and Wei Du

Doc ID: 328098 Received 11 Apr 2018; Accepted 10 Jul 2018; Posted 12 Jul 2018  View: PDF

Abstract: By utilizing the ultrafast dynamics of the photo-excited electrons in graphene, we theoretically present an ultrafastall-optical plasmonic modulator. With the help of an external pump, the femtosecond thermodynamics of the hotcarriers can tune the Fermi level of the graphene sheet in less than 1 ps, which is the dependence of the support forthe surface plasmonic wave. This device shows the ability to operate from the near-infrared regime to the farinfraredspectrum with the extinction ratio over 10 dB and the pump power of 0.41 mJ/cm2. Such an ultrafastmodulator may pave the way for designing the ultrahigh speed integrated photonics circuits.

Photothermal determination of the angular variation of emissivity

Yaqi Zhang and Gerald Diebold

Doc ID: 331219 Received 09 May 2018; Accepted 10 Jul 2018; Posted 11 Jul 2018  View: PDF

Abstract: A method for directional emissivity determination by measurement of absorption through a photothermal effect is described. The experimental results found for Au, Al and graphite show good agreement with the theoretical prediction of the electromagnetic theory. It is shown, as well that complex refractive indices can be determined by fitting angular absorption data with theory.

Micro-structured fiber cladding light stripper for kW-class laser systems

Mateusz Wysmolek, Christoph Ottenhues, Tony Pulzer, Thomas Theeg, Hakan Sayinc, Michael Steinke, Uwe Morgner, Joerg Neumann, and Dietmar Kracht

Doc ID: 332120 Received 18 May 2018; Accepted 10 Jul 2018; Posted 11 Jul 2018  View: PDF

Abstract: All-glass micro-structured high power cladding mode stripper capable of handling cladding light of up to a power of approx. 350 W with stripping efficiencies >22 dB is presented. An optimized graded structure pattern increased device’s reliability and its power handling capabilities. Subjected to 500 hours stress-test, the device shows no degradation.

Investigating the color of the blood stains onarchaeological cloths: the case of the Shroud of Turin

Antonio Di Lascio, Paolo Di Lazzaro, Paola Iacomussi, Mauro Missori, and Daniele Murra

Doc ID: 327635 Received 04 Apr 2018; Accepted 10 Jul 2018; Posted 11 Jul 2018  View: PDF

Abstract: The unique reddish blood stains on the archaeological cloth known as the Shroud of Turin caught the attention ofseveral scholars, who proposed different hypotheses to explain the unusual blood color. To date, just few hypotheseshave been tested experimentally, and the results are debatable. In this paper we test the strength of two hypotheses(namely, the presence of carboxyhemoglobin and the long term influence of ultraviolet light on high-bilirubin blood)by the spectral reflectance of the blood stain regions on the Shroud and by color analyses of ultraviolet irradiatedhigh-bilirubin blood stains on linen. The relevance of these simple methods to the study of stained textiles is discussed.

A numerical tool for estimating the dielectric constant,the thickness and the coverage of immobilizedinhomogeneous protein films on gold in aqueoussolution

Tiago Sousa, Leiva Oliveira, Helmut Neff, Herve Laborde, and Antonio Marcus Lima

Doc ID: 328740 Received 18 Apr 2018; Accepted 09 Jul 2018; Posted 16 Jul 2018  View: PDF

Abstract: A numerical simulation tool is reported for nanometer thin and inhomogeneous immobilized proteinfilms on gold in aqueous solution. It allows for the first time the simultaneous assessment of refractiveindex, film thickness and surface coverage. The model relies on and combines the convective diffusionequation, the Langmuir adsorption isotherm and the Helmholtz equation, with appropriate boundaryconditions. These three differential equations were jointly solved using a multi-physics software. Thephysical film parameters were extracted by means of an optimization procedure for immobilized bovineserum albumin (BSA), Hemoglobin and Neutravidin films. The relatively good agreement between theextracted values for the refractive index, film thickness and surface coverage and the corresponding valuesreported in the open literature show the correctness of the proposed methodology.

Quantitative analysis of potassium in ceramic raw materials using laser-induced breakdown spectroscopy

yun tang, Lianbo Guo, Shisong Tang, YanWu Chu, Qingdong Zeng, Yan Zeng, Jun Duan, and Yongfeng Lu

Doc ID: 334098 Received 31 May 2018; Accepted 09 Jul 2018; Posted 09 Jul 2018  View: PDF

Abstract: The determination of potassium (K) content in ceramic raw materials provide important references for ceramic sintering. To realize rapid, in situ, and real-time analysis detection, a laser-induced breakdown spectroscopy (LIBS) system was set up to analyze K content in ceramic raw materials. However, the self-absorption was the serious influence on the accuracy of K element analysis. In this work, a method of peak fitting with Lorentz function was proposed to reduce the self-absorption effect in LIBS. After Lorentz fitting, the determination coefficient (R2 factor) for K element improved from 0.993 to 0.998, the root-mean-square error of cross-validation (RMSECV) reduced from 0.458 wt. % to 0.145 wt. %, the average relative error (ARE) reduced from 13.769 % to 5.121 %. The results indicate that the Lorentz fitting can effectively reduce the self-absorption effect, and improve the accuracy of quantitative analysis for K element. According to the results, the proposed approach can be a promising method for determination of elements suffered from self-absorption in LIBS.

Holographic fabrication of graded photonic super-quasi-crystal with multiple level gradients

David Lowell, safaa hassan, Oliver Sale, Murthada Adewole, Noah Hurley, Usha Philipose, banglin chen, and Yuankun Lin

Doc ID: 330391 Received 25 Apr 2018; Accepted 09 Jul 2018; Posted 10 Jul 2018  View: PDF

Abstract: Photonic quasi-crystals and photonic crystals with certain degrees of disorder can have a broad-band light-matter interaction. In this paper, we present the holographic fabrication of graded photonic super-quasi-crystals through pixel-by-pixel phase pattern engineering using a spatial light modulator. Using the same phase pattern arranged in a decagon, we have fabricated graded photonic super-quasi-crystals with five-fold symmetry and multiple levels of gradients and graded photonic super-crystals with rectangular unit super-cells, depending on the Fourier filter. Although a certain degree of disorder was incorporated in the quasi-crystals, we still observed the golden ratio in the diameters of the diffraction rings of the fabricated quasi-crystals, indicating five-fold symmetry. Using direct pixel-by-pixel phase engineering, the same laser projection system consisting of an integrated spatial light modulator and reflective optical element can be used for the fabrication of graded photonic super-crystals with various symmetries. The multi-level gradient effects on the optical properties of an organic light-emitting diode were simulated. When the cathode of an organic light emitting device is patterned in the graded photonic super-crystals, a light extraction efficiency up to 76% in the visible range can be achieved.

Silane functionalization effects on dispersion of alumina nanoparticles in hybrid carbon fiber composites revealed through photo-luminescence spectroscopy

Alex Selimov, Sanjida Jahan, Eric Barker, Peter Dackus, Declan Carolan, Ambrose Taylor, and Seetha Raghavan

Doc ID: 331085 Received 08 May 2018; Accepted 09 Jul 2018; Posted 10 Jul 2018  View: PDF

Abstract: Hybrid carbon fiber reinforced polymer composites are a new breed of materials currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, hybrid properties including improved mechanical properties and stress-sensing capabilities can be achieved. However, manufacturing solutions that address the inherent tendency for the nanoparticles to agglomerate must first be developed to realize the benefits of the reinforcing nanoparticles. Photoluminescence spectroscopy is used here to investigate the effects of both reactive and non-reactive silane functionalization on particle dispersion for different weight percentages of reinforcements used in the manufacturing process. The photo-luminescence results show that application of surface treatments on the nanoparticles improved their dispersion, with the reactive treatment providing for the most consistent samples. Improvements to dispersion and increased consistency were shown quantitatively for different weight percentages of filler particles. The findings provide guidelines for manufacturing that will help achieve improved dispersion and consequently more uniform mechani- cal properties of these hybrid composites.

Polarization Induced Distortion Effects on theInformation Rate in the Single Mode Fibers

Mahdi Zamani

Doc ID: 328471 Received 16 Apr 2018; Accepted 09 Jul 2018; Posted 09 Jul 2018  View: PDF

Abstract: In this paper, we examine information theoretic propertiesof the single mode fiber in the presence of polarizationinduced distortion effects. We derive some capacityresults, and further obtain several non-ergodic achievablerates. In this work, however, mostly linear distortions areconsidered. Since polarization dependent loss (PDL) is anon-unitary phenomenon, information rate loss caused byPDL is fundamentally inevitable. Interestingly, it is shownthat in the presence of channel state information (CSI) atthe transmitter, PDL can increase the capacity in some scenaria.We analytically found also that the highest averagecapacity improvement from the knowledge of PDL at thetransmitter is equal to the mean PDL of the link, and thisbenefit vanishes at high signal-to-noise ratio (SNR). In orderto achieve the ergodic capacity, it is established thatsending uncorrelated Gaussian signals with equal powervia both polarizations is the optimum transmit strategy. Asit turns out from the results, perhaps counter-intuitively, inthe presence of PDL, polarization mode dispersion (PMD)always improves the maximum outage rate; however thePMD impact on the maximum throughput and the maximumtwo-layer expected-rate is trivial. Finally, an extensionto the simple Gaussian noise (GN) model of fiber nonlinearityis explored. All theoretical results are illustratedby numerical simulations.

Optical properties of oak wood in the near-infrared range of semi-transparency

Leonid Dombrovsky, Jean-Francois Henry, Clarisse Lorreyte, Herve Pron, and Jaona Randrianalisoa

Doc ID: 328714 Received 17 Apr 2018; Accepted 06 Jul 2018; Posted 09 Jul 2018  View: PDF

Abstract: The spectral absorption and scattering properties of oak wood are retrieved from the measurements of both the normal-hemispherical reflectance and transmittance in the visible and near-infrared ranges of semi-transparency. Two alternative methods for the radiative transfer in wood samples are employed: the modified two-flux approximation and the high-order discrete ordinate method. The modifications of both methods take into account the effect of total internal reflection at both surfaces of the wood samples. The analytical approximate solution of the first method gives very accurate results for the absorption coefficient, but the transport scattering coefficient of wood appeared to be systematically underestimated. Fortunately, this error is between 7% and 12% and that is acceptable for the estimates. The samples of oak wood of four different thicknesses are used in the experiments. The effect of orientation of wood cells appears to be insignificant and can be observed in the reflectance from optically thin samples only. There is a considerable decrease in transport scattering coefficient of oak wood with the wavelength. This effect is explained by a predominant contribution of micron-sized longitudinal pores in oak wood. The latter is used to develop an approximate theoretical model of scattering based on the rigorous solution for arbitrary oriented cylindrical pores. The model suggested is in good agreement with the experimental data.

Binarized dual phase-shifting method for high-quality 3D shape measurement

Yajun Wang, Saptarshi Basu, and Beiwen Li

Doc ID: 327045 Received 27 Mar 2018; Accepted 06 Jul 2018; Posted 09 Jul 2018  View: PDF

Abstract: It has been demonstrated that using 1-bit binary patterns is better than using 8-bit sinusoidal patterns for high-speed applications. However, the phase quality generated from binary patterns is lower especially when the projector is nearly focused. Dual phase-shifting method can effectively reduce the dominant periodical phase errors caused by high order harmonics. Yet, such method requires an additional set of phase-shifting patterns, which thus slows down the measurement speed. To overcome this problem, this paper proposes a binarized dual phase-shifting method (BDPS) to generate high-quality phase using just three phase-shifted binary patterns. The basic idea is to merge the two sets of square binary phase-shifting patterns into one set of patterns with three gray levels, which is further binarized by employing 2D area modulation. Given this, the BDPS method can realize error reduction for the binary defocusing technique while maintaining its speed advantage by neither adding the total number of patterns nor the number of bits. The effectiveness of the proposed method is verified by both a quantitative evaluation by measuring a white flat board, and a qualitative evaluation by measuring a complex sculpture surface.

Experimental characterization and modeling of optical tweezer particle handling dynamics

Michael Porter, Brian Giera, Robert Panas, Lucas Shaw, Maxim Shusteff, and Jonathan Hopkins

Doc ID: 327672 Received 04 Apr 2018; Accepted 05 Jul 2018; Posted 09 Jul 2018  View: PDF

Abstract: We report a new framework for a quantitative understanding of optical trapping (OT) particle handling dynamics. We present a novel three-dimensional particle-based model that includes optical, hydrodynamic, and inter-particle forces. This semi-empirical colloid model is based on an open-source simulation code known as LAMMPS, and properly recapitulates the full OT force profile beyond the typical linear approximations valid near the trap center. Simulations are carried out with typical system parameters relevant for our experimental holographic optical trapping (HOT) system, including varied particle sizes, trap movement speeds, and beam powers. Furthermore, we present a new experimental method for measuring both the stable and metastable boundaries of the optical force profile to inform or validate the model's underlying force profile. We show that our framework is a powerful tool for accurately predicting particle behavior in a practical experimental OT setup, and can be used to characterize and predict particle handling dynamics within any arbitrary OT force profile.

Simultaneous determination of aerosol optical depthand exponent of Junge power-law from MODISshortwave infrared bands over Qinghai Lake

Lin Zhu, Qingshan Xu, chen cheng, Xiongwei Sun, Pengfei Wu, and Lei Yang

Doc ID: 330988 Received 04 May 2018; Accepted 05 Jul 2018; Posted 05 Jul 2018  View: PDF

Abstract: The water-leaving radiances for the shortwave infrared(SWIR) channels can be negligible for case II waters, andthese channels also contain information of aerosol particle sizes. So, the satellite-based data of SWIR channels canbe used to estimate aerosol particle size over coastal waters and inland lakes. Suppose the actual atmosphericaerosol size distribution is Junge power-law. An iterative algorithm is used to simultaneously determining theaerosol optical depth(AOD) and the exponent of Junge power-law from Aqua MODIS L1B reflectance data ofchannel 1.64um and 2.13um over Qinghai Lake, in this paper. Whether constant or variable aerosol complexrefractive index(ACRI), the retrieved exponent of Junge power law always larger than product value. Suppose theproduct values are accurate. For constant ACRI, there are 68.91% and 25.48% pixels with acceptable retrieval AODand the exponent of Junge power law value, respectively. Likewise, there are 71.63% and 43.75% pixels forvariable ACRI. Compared with the retrieval error under constant ACRI, there are 58.65% and 98.72% pixels withsmaller AOD and Junge power-law index retrieval error under variable ACRI, respectively. Besides, the precision ofAOD retrieved with variable ACRI are improved when the AOD product is less than 0.17. However, under thecurrent environment with frequent aerosol particle pollution, the same ACRI for the ten wavelengths can get resultwith equivalent accuracy compared with variable ACRI.

On-Orbit Characterization of the VIIRS Solar Diffuser and Attenuation Screens for NOAA-20 Using Yaw Measurements

Junqiang Sun, Mike Chu, and Menghua Wang

Doc ID: 327842 Received 10 Apr 2018; Accepted 05 Jul 2018; Posted 10 Jul 2018  View: PDF

Abstract: The follow-up Visible Infrared Imaging Radiometer Suite (VIIRS) housed in the Joint Polar Satellite System (JPSS)-1 satellite, designated post-launch as NOAA-20 and the first of four in the NOAA JPSS satellite series, was launched on 18 November 2017. The on-orbit satellite yaw maneuver operation was carried out on 25-26 January 2018 over 15 scheduled orbits to obtain responses of the reflective solar bands (RSBs) and the solar diffuser stability monitor (SDSM) over a specified angular range. This paper presents a comprehensive analysis of the yaw measurements that characterizes the three required input functions for the standard on-orbit RSB calibration pipeline. The characterization functions of the product of the bidirectional reflectance factors (BRFs) of the solar diffuser (SD) with the vignetting function (VF) of the SD screen (SDS), dubbed the BRF-VF-products (BVPs), are derived for the two required outgoing directions from the SD, one set for the RSB BVPs from the SD to the Rotation Telescope Assembly (RTA) that directs light to the RSBs, and another set for the SDSM BVPs for the outgoing direction from the SD to SDSM. The VFs for the attenuation screen placed in front of the Sun-view port, the Sun-view screen (SVS), are analyzed as a set of standalone functions to characterize the direct solar illumination reaching the SDSM through the SVS, but the complexity of their non-smooth two-dimensional dependence requires an additional direct treatment in the derivation of the degradation of the SD, the H-factors. The result for the RSB BVPs, SDSM BVPs and the SVS VFs are presented and discussed, and further applied to derive the early-mission performance of H-factors and the RSB calibration coefficients, or F-factors. The overall results of the H-factors and F-factors showing smooth trends with negligible residuals indicate that the derived BVP functions and the SVS VFs have been accurately characterized or treated, and are ready for use for the standard on-orbit RSB calibration of NOAA-20 VIIRS.

Spatially correlated coherent diffractive imaging method

Xu Tao, Zijian Xu, Haigang Liu, Chunpeng Wang, Zhenjiang Xing, Yong Wang, and Renzhong Tai

Doc ID: 331652 Received 14 May 2018; Accepted 05 Jul 2018; Posted 09 Jul 2018  View: PDF

Abstract: Coherent diffractive imaging (CDI) is a lensless, high-resolution imaging method that is currently under rapid development by using X-rays, visible light, or electrons. However, its inherent ambiguities and the need of a priori knowledge about objects are limiting applications of this method. By combining a conventional CDI method with the basic idea of ptychography, the method of spatially correlated CDI, a method fit for multiple samples imaging in single-shot mode, is proposed to enhance the robustness of CDI. In this method, a strong spatial relevancy is built by introducing a same region into each sample, which establishes a strong real-space constraint for image reconstruction. Both simulations and visible light experiments demonstrated the good imaging quality and robustness of this method which does not need tight supports.

Noiseless optical encryption based on complex secret key and joint Fresnel transform correlator with Billet split lens

shaozu li, xue shen, Bing zhou, and Long Wang

Doc ID: 331137 Received 08 May 2018; Accepted 04 Jul 2018; Posted 05 Jul 2018  View: PDF

Abstract: A noiseless optical cryptosystem based on joint Fresnel transform correlator (JFTC) with Billet split lens (BSL) wasdesigned, benefit from the adjustable structure of BSL, we can control the size and recording position of the jointFresnel transform power distribution by changing the split width of BSL. To avoid the texts being affected by noise,we converted the texts into quick response (QR) code in advance, then used the QR code as the plaintext, andutilized the noise tolerance ability of QR code to realize noiseless recover of the texts. In this cryptosystem, wedesigned a complex secret key (CSK) to replace the secret key made from random phase mask, and the CSK consistsof QR code filter and spiral phase mask. Because QR code and spiral phase can be determined by a few simple data,the transmission and preservation of the CSK is convenient. Finally, the validity and feasibility of the cryptosystemwere demonstrated, and the sensitivity of the CSK was researched by simulation and experiment.

Measuring refractive index of glass by using speckle

Changliang Guo, Dayan Li, Damien Kelly, Haoyu Li, James Ryle, and John Sheridan

Doc ID: 327417 Received 04 Apr 2018; Accepted 04 Jul 2018; Posted 05 Jul 2018  View: PDF

Abstract: A method to measure the refractive index of an optically flat regularly shaped slab of glass using speckle correlation-based techniques is reported. The intensity of the diffraction field of the diffuser is captured by a CCD both with and without the glass present. As the position of peak correlation coefficient is quantitatively related to the change in optical path length arising due to the presence of the glass, the refractive index of the glass can be evaluated by cross correlating the two captured images. The theoretical correlation function that describes the effects of such an optical path length change is discussed and the resulting speckle decorrelation function derived. Several glass samples are measured to demonstrate the accuracy and robustness of the proposed technique.

Nonlocal Low-Rank-Based Blind Deconvolution ofRaman Spectroscopy for Carbohydrate Recognition

Tingting Liu, Liu Hai, Zhaoli Zhang, and Sanya Liu

Doc ID: 327450 Received 03 Apr 2018; Accepted 04 Jul 2018; Posted 05 Jul 2018  View: PDF

Abstract: Raman spectroscopy often suffers from the problems of band overlap and random noise. In this work, wedevelop a nonlocal low-rank regularization (NLR) approach toward exploiting structured sparsity andexplore its applications in Raman spectral deconvolution. Motivated by the observation that the rank ofground-truth spectrum matrix is lower than that of the observed spectrum, a Raman spectraldeconvolution model is formulated in our method to regularize the rank of the observed spectrum by totalvariation regularization. Then, an effective optimization algorithm is described to solve this model, whichalternates between the instrument broadening function and latent spectrum until convergence. In additionto conceptual simplicity, the proposed method has achieved highly competent objective performancecompared to several state-of-the-art methods in Raman spectrum deconvolution task. The restored Ramanspectra are more suitable for extracting the spectral features and recognizing the carbohydrate materials.

Space-variant video compression and processing in digital holographic microscopy sensor networks with application to potable water monitoring

Tomi Pitkäaho, Ville Pitkakangas, Mikko Niemela, Sudheesh Rajput, Naveen K. Nishchal, and Thomas Naughton

Doc ID: 327476 Received 03 Apr 2018; Accepted 04 Jul 2018; Posted 05 Jul 2018  View: PDF

Abstract: Water-related diseases affect societies in all parts of the world. On-line sensors are considered as a solution to the problems associated with laboratory testing in potable water. One of the most active research areas of such on-line sensor has been within optics. Digital holographic microscopy (DHM) has the potential to rival state-of-the-art techniques such as advanced turbidity measurement. However, its use as an on-line sensor is limited by the large data requirements typical for digital holographic video. In this paper, we provide a solution that permits DHM to be applied to a whole class of on-line remote sensor networks, of which potable water analysis is one example. The designed sensors incorporate a novel space-variant quantization algorithm to preprocess each frame of a video sequence before transmission over a network. The system satisfies the generally accepted requirements of an on-line system: automated, near real-time, and operating in a real environment. To verify the effectiveness of the design, we implemented and evaluated it in an active potable water facility.

Chiral Sculptured Thin Films for Circular Polarization of Mid-Wavelength Infrared Light

Vikas Vepachedu and Akhlesh Lakhtakia

Doc ID: 328175 Received 11 Apr 2018; Accepted 04 Jul 2018; Posted 05 Jul 2018  View: PDF

Abstract: Being an assembly of identical upright helixes, a chiral sculptured thin film (CSTF) exhibits the circular Bragg phenomenon and can therefore be used as a circular-polarization filter in a spectral regime called the circular Bragg regime. This has been already demonstrated in the near-infrared and short-wavelength infrared regimes. If two CSTFs are fabricated in identical conditions to differ only in the helical pitch, and if both are made of a material whose bulk refractive index is constant in a wide enough spectral regime, then the center wavelengths of the circular Bragg regimes of the two CSTFs must be in the same ratio as their helical pitches by virtue of the scale invariance of the frequency-domain Maxwell postulates. This theoretical result was confirmed by measuring the linear-transmittance spectrums of two zinc-selenide CSTFs with helical pitches in the ratio $1$:$7.97$. The center wavelengths were found to be in the ratio $1$:$7.1$, thedeviation from the ratio of helical pitches being explainableat least in part because the bulk refractive index of zinc selenide decreased a little with wavelength.We concluded that CSTFscan be fabricated to function as circular-polarization filters in the mid-wavelength infrared regime.

Feasibility of cmOCT angiographic technique using 200kHz VCSEL source for in vivo microcirculation imagingapplications

CERINE LAL, Hrebesh Subhash, Sergey Alexandrov, and Martin Leahy

Doc ID: 328513 Received 16 Apr 2018; Accepted 04 Jul 2018; Posted 05 Jul 2018  View: PDF

Abstract: Optical coherence tomography (OCT) angiography is a wellestablishedin vivo imaging technique to assess the overall vascularmorphology of tissues and is an emerging field of research for theassessment of blood flow dynamics and functional parameters such asoxygen saturation. In this study, we present a modified scanning basedcorrelation mapping OCT (cmOCT) using a 200 kHz high speed sweptsource OCT system operating at 1300 nm and demonstrate its widefield imaging capability in ocular angiographic studies.

Silicon-wire optical demultiplexers based onmultistage delayed Mach-Zehnder interferometers forhigher production yield

Seok-Hwan Jeong and Yu Tanaka

Doc ID: 330255 Received 24 Apr 2018; Accepted 03 Jul 2018; Posted 05 Jul 2018  View: PDF

Abstract: We report better spectral uniformity in Si-wire-based multistage delayed Mach-Zehnder interferometer typeoptical multiplexers/demultiplexers (MUX/DeMUX). Based on 300-mm silicon-on-insulator (SOI) waferscale ArFimmersionlithography process that guarantees higher phase controllability for low insertion loss, spectral flatnessand low crosstalk, we were able to further improve spectral uniformity across the wafer by optimizing thewaveguide width within the optical path of each DMZI region. Irrespective of channel spacing in wavelengthdomain, it was experimentally demonstrated that the filter spectral center wavelength deviation of the proposedDeMUXs were 3 times smaller than that of conventional ones. The proposed device scheme would also be veryattractive for arbitrary channel spacing and channel count, which makes the proposed scheme more practical inhigh-performance WDM optical transceivers. ©

Dependence of the imaging properties of the liquid lenswith variable focal length on membrane thickness

Filip Šmejkal and Antonin Miks

Doc ID: 330850 Received 02 May 2018; Accepted 03 Jul 2018; Posted 05 Jul 2018  View: PDF

Abstract: This paper presents influence of membrane thickness on imaging properties of membrane liquid lenses withvariable focal length. Approximate formulas for varying thickness of spherically and parabolically deformedmembrane were derived, which allows us to determine its influence on quality of imaging properties of amembrane liquid lens. Furthermore, formulas for wave spherical aberration calculation of a membrane and liquidlens body were derived. It has been shown that the influence of membrane thickness and its changes on wavespherical aberration is negligible from practical point of view.

Q-switched Ytterbium-doped Fiber Laser Via ThuliumdopedFiber Saturable Absorber

MOHD F. A. RAHMAN, A. A. Latiff, M. F. M. Rusdi, Kaharudin Dimyati, and Sulaiman Wadi Harun

Doc ID: 332260 Received 21 May 2018; Accepted 03 Jul 2018; Posted 03 Jul 2018  View: PDF

Abstract: We demonstrated a reliable and stable Q-switched Ytterbium-doped fiber laser (YDFL) centred at 1069 nm byemploying a segment of 11 cm Thulium-doped fiber (TDF) as a saturable absorber (SA) in the ring cavity. Thefiber SA has an optical absorption of 1.35 dB at the Q-switched operating regime. As we increased the pumppower from 109 mW to the maximum available pump power of 206 mW, a consistent Q-switched laser withoutput power, ranging from 1.8 mW to 4.8 mW was attained. The pulse width narrowed from 4.9 μs to 2.87 μs,whereas the repetition rate increased from 40 kHz to 60.2 kHz. In addition, a maximum pulse energy of 80.7 nJand a maximum peak power of 28.1 mW, were obtained at the maximum pump power. The signal to noise ratio(SNR) was around 47 dB. Our experimental study shows that a segment of TDF can be used as a Q-switcher in the1-micron fiber laser cavity to facilitate a reliable and robust microseconds pulse generation.

Regularized slanted-edge method for measuring themodulation transfer function of imaging systems

Xufen Xie, Hongda Fan, Anding Wang, Nianyu Zou, and Yuncui Zhang

Doc ID: 326685 Received 22 Mar 2018; Accepted 03 Jul 2018; Posted 05 Jul 2018  View: PDF

Abstract: The slanted-edge method for modulation transfer function (MTF) measurement uses edge target images whosegray values are often affected by noise and other factors, decreasing its accuracy. We first analyze the ill-posednessin the edge spread function (ESF) regression caused by noise. Second, we propose a regularized slanted-edgemethod to solve this problem by incorporating a Tikhonov regularization term. Combined with varying precisionweights, the ESF is solved using the variational principle, and the MTF is estimated using the regularized ESF. Theregularized slanted-edge method is verified for Gaussian, gamma, and Rayleigh noise. The results show that ourmethod improves the accuracy by 0.01%–9.02% and 4.33% on average. The proposed method is more robust tonoise and accurate than the slanted-edge method.

Wrapping-free numerical refocusing of scalar electromagnetic fields

Pascal Berto, Marc Guillon, and Pierre Bon

Doc ID: 331759 Received 15 May 2018; Accepted 03 Jul 2018; Posted 05 Jul 2018  View: PDF

Abstract: Numerical refocusing in any plane is one powerful feature granted by measuring both the amplitude and the phase of a coherent light beam. Here we introduce a method based on the first Rytov approximation of scalar electromagnetic fields which (i) allows numerical propagation without requiring phase-unwrapping after propagation and (ii) limits the effect of artificial phase singularities that appear upon numerical defocusing when the measurement-noise is mixing with the signal. We demonstrate the feasibility of this method with both scalar electromagnetic field simulations and real acquisitions of microscopic biological samples imaged at high numerical aperture.

Rayleigh backscattered radiation produced by an arbitrary incident mode in multimode optical fibers

Mikhail Bisyarin, Oleg Kotov, Arthur Hartog, Leonid Liokumovich, and Nikolai Ushakov

Doc ID: 328997 Received 20 Apr 2018; Accepted 03 Jul 2018; Posted 03 Jul 2018  View: PDF

Abstract: The recently developed diffraction technique of analytical investigation of the Rayleigh backscattering produced by an incident fundamental mode in a multimode optical fiber with an arbitrary refractive index profile is generalized to admit an arbitrary incident mode, either radial or azimuthal. The relative powers of all backscattered modes are determined with explicit formulas via the properly normalized transverse distributions of the incident and backscattered mode fields within the fiber cross section. The regularities conditioned by azimuthal indices are expressed via a universal set of coefficients, and dependences on the radial mode indices are estimated numerically. Excitation coefficients are shown to be symmetrical for any pair of incident and backscattered modes.

Analysis of the impact of air scattering on point source transmittance

zhirui cao, xun chao, and Yuegang Fu

Doc ID: 327782 Received 10 Apr 2018; Accepted 03 Jul 2018; Posted 10 Jul 2018  View: PDF

Abstract: This paper proposes a method to simulate an average air scattering model by using random particles obeying a certain size spectrum and shape distribution, and analyzes the influence of air scattering on the point source transmittance (PST) test using the model. The results of the analysis indicated that PST measurement errors caused by air scattering are directly proportional to the cube of the diameter of the optical system, and that a one-level change in the air cleanliness may result in a one-order-of-magnitude change in the error. The cleanliness level of the measurement environment is less expensive and easier to obtain from analysis than from empirical values.

Tunable and passively Q-switched laser operation of Nd,Lu:CaF₂ disordered crystal

Qianqian Hao, siyuan pang, Jie Liu, and Liangbi Su

Doc ID: 331024 Received 07 May 2018; Accepted 02 Jul 2018; Posted 03 Jul 2018  View: PDF

Abstract: We report the first demonstration, to the best of our knowledge, of tunable and Q-switched lasers based on diode-pumped Nd,Lu:CaF₂ disordered crystal. A continuous tuning range of approximately 32 nm (1047–1079 nm) was obtained for tunable operations. A passively Q-switched laser was successfully achieved using a Cr4+:YAG as a saturable absorber. The shortest pulse width of 275 ns was obtained with a repetition rate of 1.85 kHz and corresponding peak power and single pulse energy of 189 W and 51.9 µJ, respectively.

Vibration Phases Estimation Based on Multi-channels Interferometry for ISAL

Xuan Hu and Daojing Li

Doc ID: 331183 Received 08 May 2018; Accepted 02 Jul 2018; Posted 03 Jul 2018  View: PDF

Abstract: Target vibration introduces unexpected vibration phases in the echo signal of inverse synthetic aperture LADAR (ISAL). The vibration phases cause the imaging results to be defocused. How to estimate the vibration phases has always been one of the difficulties in ISAL imaging, and there has not been an effective solution. In this paper, two methods are proposed to estimate the vibration phases in different situations. The method based on multi-channels along-track interferometry (MCATI method) is for some cases that the target velocity vector is parallel to some baselines of ISAL. The method based on orthogonal interferometry (OI method) is for other cases that the target velocity vector is not parallel to any baseline of ISAL. In addition, high signal to noise ratio (SNR) is essential for the MCATI method and OI method to get high estimation accuracy. Therefore, large power-aperture product should be carefully considered in ISAL system design. Furthermore, on the condition of low SNR, range cells accumulation is also helpful to reduce the influence of noise. Take the ISAL which is utilized to image the satellite in 500km orbit as an example, the estimation accuracy can satisfy the demand of synthetic aperture imaging with 0dB single pulse SNR and 300 range cells accumulation. The proposed methods are verified with simulation and experiment.

Behavior of tiled-aperture arrays fed by vector partially coherent sources

Milo Hyde and Mark Spencer

Doc ID: 331416 Received 10 May 2018; Accepted 02 Jul 2018; Posted 03 Jul 2018  View: PDF

Abstract: This paper explores the far-zone behavior of partially coherent arrays. We derive an expression for the far-zone spectral density valid for any array composed of circular elements and fed by fields with Schell-model cross-spectral density functions. This expression is written as the sum of convolution integrals making it easy to physically interpret. We discuss this expression at length and present examples. We validate our analysis by comparing Monte-Carlo averages from wave-optics simulations with theory. Lastly, we conclude this paper with a brief summary of the results and potential uses of our work.

Electric arc induced strength-controllable weakpolarization mode coupling in polarizationmaintaining fiber

yanshuang zhao, Sheng Huang, zhiru cui, Chai Quan, yanlei liu, Jing Ren, Jianzhong Zhang, Elfed Lewis, Zhihai Liu, Jun Yang, and Libo Yuan

Doc ID: 331636 Received 15 May 2018; Accepted 02 Jul 2018; Posted 03 Jul 2018  View: PDF

Abstract: An electric arc based scheme to generate strength-controllable weak polarization mode coupling (PMC) points inpolarization maintaining fiber (PMF) is described. The resulting PMC strengths can be readily controlled to be inthe very weak range of -60dB~-40dB. In this range, excellent mechanical strength combined with high return loss isachieved. An experimental quasi-distributed temperature sensor is formed by three separate PMC points in asingle PMF using electric arc method.

Plasmonic filter and sensor based on subwavelength end-coupled hexagonal resonator

Wenhui Lai, Kun-Hua Wen, Jiyan Lin, Zicong Guo, Qinyang Hu, and Yihong Fang

Doc ID: 331899 Received 17 May 2018; Accepted 02 Jul 2018; Posted 03 Jul 2018  View: PDF

Abstract: In this paper, an end-coupled hexagonal resonator inserted with dual parallel metallic blocks is proposed based on subwavelength metal-insulator-metal (MIM) waveguides. When the blocks are vertically inserted into the resonator, more transmission channels (3 peaks) with symmetrical spectral shapes than that (1 peak) of the perfect hexagonal resonator are achieved in the same wavelength range. The transmission peaks are all with high transmittances, thus, the structure can be performed as an on-chip optical filter. When the blocks are horizontally distributed in the resonator, antinode and node of the magnetic field for the expected mode will arise inside and outside of the blocks, leading to the mode interactions. Subsequently, Fano resonance with asymmetrical peak is achieved in the structure. High index sensitivity and high figure of merit, which are the significantly factors for optical sensors, are investigated by using finite-difference time-domain method. The proposed structure can highly support the development of the integrated photonics, and find widely applications in the on-chip optical filtering and sensing areas.

A nonlinear mapping method for the generation of elemental image array in photorealistic pseudoscopic free 3D display

Jun Wen, Xingpeng Yan, Xiaoyu Jiang, Zhiqiang Yan, Yifei Wang, and Junfu Wang

Doc ID: 326504 Received 22 Mar 2018; Accepted 02 Jul 2018; Posted 03 Jul 2018  View: PDF

Abstract: Limited available elemental image array resources may be the most severe bottleneck for the promotion and application of integral imaging based 3D display. We propose a nonlinear mapping method for the generation of elmental image array to get photorealistic pseudoscopic free 3D display based on the parallel light field reconstruction nature of the integral imaging system. All the light rays emitted from the display panel are classified into a corresponding parallel light field according to its direction, and all the parallel light fields are captured as orthogonal projections of the scene before synthesizing all the orthogonal projections using nonlinear mapping method to form the final elemental image array. Preliminary optical experiments as well as ray optical analysis are conducted to prove the feasibility and validity of the proposed method. The proposed method can exploit the most of the current 3D platform. It is an effective and efficient way to generate elemental image array.

Polarization-Insensitive broadband THz metamaterialabsorber based on hybrid structures

Yuying Lu, Jining Li, Shaohua Zhang, and jinhai Sun

Doc ID: 326604 Received 22 Mar 2018; Accepted 02 Jul 2018; Posted 03 Jul 2018  View: PDF

Abstract: A polarization-insensitive broadband terahertz metamaterial absorber is presented in this paper. Themetamaterial absorber consists of several circular and rhombus metallic patches as a unit cell and a metallicground plane separated by a polyimide dielectric layer. By increasing the number of circular and rhombus patcheswith different sizes, the operating bandwidth of the absorber is broadened because of the resonances of each singlepatch getting close enough and merging together in the frequency range. The simulated results show that theabsorption bandwidth covers a broadband frequency range of 0.22-0.33 THz with the highest absorptivity of99.93% at 0.3035 THz. The full width at half maximum (FWHM) is as wide as 0.155 THz, and the bandwidth of over80% absorptivity is 0.1315 THz. This study promises applications in terahertz detection and communicationsystem. And the operation bandwidth is much convenient and compatible for electronic terahertz source.

A compact portable laser system for mobile cold atom gravimeters

Xiaowei Zhang, Jiaqi Zhong, biao tang, Xi Chen, Lei Zhu, panwei huang, Jin Wang, and Mingsheng Zhan

Doc ID: 331995 Received 21 May 2018; Accepted 01 Jul 2018; Posted 03 Jul 2018  View: PDF

Abstract: We have designed and realized a compact portable laser system for high sensitivity mobile cold atominterferometers. The laser system is mounted in a single module with the dimension of 45 cm 45 cm 16 cm, and emits lights directly on up to 13 fiber ports for 2-dimension magneto-optical trap, atom fountain,Raman transition and normalized detection. A double-sided optical structure and mounts withoutkinematic adjustment are designed to achieve high level integration and stability. The laser system isapplied to a mobile atom gravimeter and achieves a sensitivity of 28 mGal/Hz1/2. Experienced 1200-kmlong-distance truck transportation, the laser system could be restored to good operating status withoutinternal realignment.

Time-delay-signature-suppressed broadband chaos byscattering feedback and optical injection

Jianzhong Zhang, Mengwen Li, Anbang Wang, Mingjiang Zhang, Yongning Ji, and Yun-cai Wang

Doc ID: 332202 Received 21 May 2018; Accepted 01 Jul 2018; Posted 03 Jul 2018  View: PDF

Abstract: We propose and demonstrate a novel scheme to generate time-delay-signature-suppressed broadband chaoticlight by using an optically injected laser diode subjected to scattering light feedback. The achievement ofbroadband chaos is based on the interaction between the injection light and chaotic laser from the scatteringfeedback semiconductor laser via beating. A single mode fiber as a continuous scatterer is specially used as afeedback cavity to introduce random feedback, which could truly eliminate the time delay signature of chaotic light.The chaotic light with power spectrum that extends to 13.6 GHz within 3 dB is experimentally achieved.

Fiber-coupled Vapor Cell for a Portable Rydberg Atom-based RF Electric Field Sensor

Matt Simons, Joshua Gordon, and Christopher Holloway

Doc ID: 330212 Received 24 Apr 2018; Accepted 30 Jun 2018; Posted 03 Jul 2018  View: PDF

Abstract: We demonstrate a movable, Rydberg atom-based radio frequency (RF) electric (E) field probe. The technique is based on Electromagnetically-induced transparency and Autler-Townes splitting. Two fibers attached to a 10 mm cubic cesium vapor cell are used to couple counter-propagating probe and coupling lasers through the cell. This all-dielectric fiber-coupled sensor can be moved from the optics table to locations more suitable for RF (GHz to sub-THz) E-field measurements and calibrations.

Improving the throughput of automated holographic optical tweezers

Lucas Shaw, Samira Chizari, and Jonathan Hopkins

Doc ID: 328358 Received 16 Apr 2018; Accepted 30 Jun 2018; Posted 03 Jul 2018  View: PDF

Abstract: The purpose of this work is to introduce three improvements to automated holographic-optical-tweezers systems that increase the number and speed of particles that can be manipulated simultaneously. First, we address path planning by solving a bottleneck assignment problem, which can reduce total move time by up to 30% when compared with traditional assignment problem solutions. Next, we demonstrate a new strategy to identify and remove undesired (e.g. misshapen or agglomerated) particles. Finally, we employ a controller that combines both closed- and open-loop automation steps, which can increase the overall loop rate and average particle speeds while also utilizing necessary process monitoring checks to ensure that particles reach their destinations. Using these improvements, we show fast reconfiguration of 100 microspheres simultaneously with a closed-loop control rate of 6Hz, and 10Hz by employing both closed- and open-loop steps. We also demonstrate the closed-loop assembly of a large pattern in a continuously-flowing microchannel-based particle-delivery system. The proposed approach provides a promising path toward automatic and scalable assembly of microgranular structures.

Determination of the thermal boundary conductance ofgold nanoparticles in aqueous solution using a methodbased on the nanobubble generation

Martín González, Eduardo Acosta, and Guillermo Santiago

Doc ID: 328841 Received 25 Apr 2018; Accepted 29 Jun 2018; Posted 03 Jul 2018  View: PDF

Abstract: We present a method to determine the thermal boundary conductance of gold nanoparticles in aqueoussolution. The novel approach consist of two steps. First measuring photoacoustic signals originatedby laser-induced nanobubbles at different energies and, secondly, fitting the experimental data with ananobubble generation model developed in a previous work. We used this method on gold nanoparticleswith diameters from 10 to 70 nm. Within this range, we obtained values of the thermal boundaryconductance between 180 W/m2K and 225 W/m2K.

Hartmann-Shack wavefront sensing without a lensletarray using a digital micromirror device

Brian Vohnsen, Alessandra Carmichael Martins, Salihah Qaysi, and Najnin Sharmin

Doc ID: 326120 Received 27 Mar 2018; Accepted 29 Jun 2018; Posted 29 Jun 2018  View: PDF

Abstract: The common Hartmann-Shack wavefront sensor makes use of a lenslet array to sample in-parallel opticalwavefronts. Here, we introduce a Hartmann-Shack wavefront sensor that employs a digital micromirror device incombination with a single lens for serial sampling by scanning. Sensing is analyzed numerically and validatedexperimentally using a deformable mirror operated in closed-loop adaptive optics with a conventional Hartmann-Shack wavefront sensor, as well as with a set of ophthalmic trial lenses, to generate controllable amounts ofmonochromatic aberrations. The new sensor is free of crosstalk and can potentially operate at kHz speed. It offersa reconfigurable aperture that can exclude unwanted parts of the wavefront.

Surface-enhanced Raman scattering for rapidhematopoietic stem cell differentiation analysis

Nebras Alattar, Hasbullah Daud, Rasoul Al-Majmaie, DOMONIC ZEULLA, MOHAMEED AL-RUBEAI, and James Rice

Doc ID: 327328 Received 30 Mar 2018; Accepted 29 Jun 2018; Posted 29 Jun 2018  View: PDF

Abstract: Raman spectroscopy based methods such as surface enhanced Raman spectroscopy is a well devolved method tomolecular fingerprint cell types. Here we demonstrate that surface enhanced Raman spectroscopy can enable todistinguish cell development stages of bone marrow hematopoietic stem cells towards red blood cells through theidentification of specific surface enhanced Raman spectroscopy biomarkers. The approach taken here is to allowcells to take in gold nanoparticles as Raman enhancement platforms for kinetic structural observations presentedhere through view of the multidimensional parameter contribution. Thereby enabling profiling of bone marrowhematopoietic stem cells acquired from proliferation (stage one), differentiation (stage two) and mature red bloodcells (stage three).

Self-processing photopolymer materials for versatile design and fabrication of holographic sensors and interactive holograms

Dervil Cody, Sabad Gul, Tatsiana Mikulchyk, Mohammad Irfan, ANASTASIA KHARCHENKO, KAMILA GOLDYN, Suzanne Martin, Svetlana Mintova, John Cassidy, and Izabela Naydenova

Doc ID: 327457 Received 03 Apr 2018; Accepted 29 Jun 2018; Posted 29 Jun 2018  View: PDF

Abstract: The aim of this article is to discuss the benefits as well as the limitations of utilising photopolymer materials in the design of holograms that are responsive to changes in their environment, such as changes in concentration of a specific substance, temperature and pressure. Three different case studies are presented including both surface and volume phase holograms in order to demonstrate the flexibility in the approach of utilising holographic photopolymers for the design of sensors and interactive optical devices. First, a functionalized surface relief hologram is demonstrated to operate as an optical sensor for detection of metal ions in water. The sensitivity and selectivity of the sensor are investigated. The second example demonstrates a volume transmission hologram recorded in a temperature sensitive photopolymer and the memory effects of its exposure to elevated temperature. Finally, a pressure sensitive reflection hologram that changes color under application of pressure is characterised and its potential application in document authentication is described.

Advances and Challenges of Intraocular Lens Design

Lan Zeng and Fengzhou Fang

Doc ID: 325338 Received 05 Mar 2018; Accepted 29 Jun 2018; Posted 02 Jul 2018  View: PDF

Abstract: Phacoemulsification technique with intraocular lens implantation has been a common treatment for cataract patients. With the rising demand of the public, new technologies on lens design have come around to minimizing intraocular aberrations, improving visual quality to the largest extent. This paper systematically review the development of the materials applied in the lens manufacturing, the different categories of intraocular lenses and the principle of design respectively. The advantages and potential drawbacks of intraocular lenses are illustrated in the paper and the prospective research to improve the design are presented in the end

High-sensitive absorption measurement intransparent isotropic dielectrics with time-resolvedphotothermal common-path interferometry

Ksenia Vlasova, Alexander Makarov, Nikolai Andreev, and Alexander Konstantinov

Doc ID: 320802 Received 13 Feb 2018; Accepted 29 Jun 2018; Posted 03 Jul 2018  View: PDF

Abstract: We propose a time-resolved photothermal common-path interferometry scheme at fast heating in the absence ofheat diffusion and employ it to measure absorption in Suprasil 311 silica glass (2.8⋅10-6 cm-1) at a wavelength of1071 nm and continual absorption in laboratory air (2.9⋅10-8 cm-1) for a signal-to-noise ratio of 100/1. Theabsorption was measured at a thermally induced phase incursion of less than 0.1 rad in a heating beam, whichguaranteed correct calibration. To calibrate this scheme, we developed a theory of diffraction on deformationstaking into account the stresses arising in an inhomogeneous temperature field. This allowed us to use a standardglass K8 for calibration. The low level of noise and time resolution of pulsed signals allowed distinguishing thecontributions of Kerr and striction nonlinearities to absorption measurements in Suprasil 311 silica glass, andenabled observing the time evolution of strictional deformations. Additionally, an anomalous temporaldevelopment of the absorption of broadband laser radiation in atmospheric air at 2.9⋅10-8 cm-1 has been revealed.

Influence of sample surface height for evaluation of peak extraction algorithms in confocal microscopy

Cheng Chen, Jian Wang, Liu jun, Wenlong Lu, Hong Zhu, and Xiangqian Jiang

Doc ID: 331050 Received 08 May 2018; Accepted 29 Jun 2018; Posted 03 Jul 2018  View: PDF

Abstract: The axial resolution performance of confocal microscopy is not only dependent on the optical characteristics, but also on the peak extraction algorithms. In previous evaluations of the peak extraction algorithms, generally sample surface height is assumed to be zero and only sampling noises-induced peak extraction uncertainty was analyzed. Here we propose a sample surface height-dependent (SHD) evaluation model which takes the combined considerations of surface height and noises for algorithms' performance comparisons. Monte Carlo based simulations were first conducted on a centroid algorithm and several nonlinear fitting algorithms such as the parabola fitting algorithm (PFA), Gaussian fitting algorithm (GFA) and sinc2 fitting algorithm (SFA). Subsequently, the evaluation indicators including mean peak-extraction error and mean uncertainty were suggested for algorithms' performance ranking. At the end, experiment verifications of the SHD model were carried out using a fiber-based chromatic confocal system. From our simulations and experiments, we demonstrate that sample surface height is a critical influence factor of peak extraction computation in terms of both the accuracy and standard deviations. Compared to the conventional uncertainty evaluation model, our SHD model can provide a more comprehensive characterization of peak-extraction algorithms' performance and offer a more flexible and consistent reference for algorithms' selections.

Detection of micro-toxic elements in commercial coffeebrands using optimized dual-pulsed laser inducedspectral analysis spectrometry

Ahmed Khalil and Osama Labib

Doc ID: 326830 Received 27 Mar 2018; Accepted 29 Jun 2018; Posted 09 Jul 2018  View: PDF

Abstract: A fast detection system based on dual-pulsed laser induced breakdown spectroscopy (DP-LIBS) was successfully developed and optimized for theestimation of micro-toxic element’s content in commercial coffee brands to monitor pollution and ensure food safety. A series of thirteen various coffeebrands were quantitatively analyzed in this study utilizing DP-LIBS and a standard analytical technique like inductively coupled plasma/optical emissionspectrometry (ICP-OES). The micro-toxic elements like aluminum (Al), lead (Pb), zinc (Zn) and chromium (Cr) exist in the coffee brands were exactlyidentified. We prepared standard matrices in a known concentration in the coffee sample to draw the standard calibration curves for each element as well asby utilizing a tactic based on the intense line emission of interesting element as a quantitative analysis. The analytical routines were approved under theexpectations that the dual-pulsed lasers created plasma was in local thermodynamic equilibrium (LTE) and optically thin. We investigated the influence ofdifferent parametric dependence studies to enhance our DP-LIBS detection sensitivity. Furthermore, the precision of our DP-LIBS data for determining theconcentration of micro -toxic elements present in coffee samples was validated via ICP-OES technique. The results achieved by DP-LIBS technique were infull agreement with the ICP-OES results. In addition, the estimated limit of detection (LOD) of our DP-LIB spectrometer for aluminum, lead, zinc andchromium elements were 105.13±07, 90.17±12, 83.58±15 and 68.78±09 μg L-1, respectively. The suggested protocols demonstrated that the excellentbenefit of the DP-LIBS for the detection of a micro -toxic elements exist in coffee and for checking the purity and quality of food products.

THERMALLY STABLE HYBRID CAVITY LASER BASEDON SILICON NITRIDE GRATINGS

Simone Iadanza, Andrei Bakoz, Praveen Singaravelu, Danilo Panettieri, Sebastian Schulz, Chinna Devarapu, Sylvain GUERBER, Charles BAUDOT, Frederic Boeuf, Stephen Hegarty, and Liam O'Faolain

Doc ID: 327314 Received 05 Apr 2018; Accepted 28 Jun 2018; Posted 28 Jun 2018  View: PDF

Abstract: In this paper we show experimental results of a thermallystable Si3N4 external cavity (SiN EC) laser withhigh power output and the lowest SiN EC laser thresholdto our knowledge. The device consists in a 250μm sized Reflective Semiconductor Optical Amplifier(RSOA) butt-coupled to a passive chip based on a seriesof Si3N4 Bragg gratings acting as narrow reflectors.A threshold of 12 mA has been achieved, with a typicalSide-Mode Suppression Ratio of 45 dB and measuredpower output higher than 3mW. Furthermore, weachieved a mode-hop free lasing regime in the range of15 mA to 62 mA and wavelength thermal stability up to80°C. This solves the challenges related to cavity resonancesthermal shift and shows the possibility for thisdevice to be integrated in Dense WDM and heat intensiveoptical-interconnects technologies.

Bendable large-mode-area fiber with non-circular cores

Junhua Ji, Huaiqin Lin, Raghuraman Sidharthan, Daryl Ho, Yanyan Zhou, Johan Nilsson, and Seongwoo Yoo

Doc ID: 327680 Received 04 Apr 2018; Accepted 27 Jun 2018; Posted 28 Jun 2018  View: PDF

Abstract: We investigate mode area scaling and bending performances of a Yb-doped large-mode-area fiber with an elongated non-circular core. Such fiber can be bent in the plane of its short axis to suppress bending effects such as mode area reduction and mode profile distortion. Meanwhile, the other orthogonal axis can be stretched for mode area scaling. Calculations show that for fibers with same mode area, the higher aspect ratio between the long axis and short axis the fiber has, the less sensitive the fiber will be to bending effects. However, mode area scaling is limited by the increased beat length between the fundamental mode and the second order mode, leading to mode degeneracy at higher aspect ratios. Within 100 mm beat length, the fundamental mode area is scalable to 3,000 μm2 in a bent fiber. To facilitate fundamental mode operation, we study mode-selective gain through confined doping. Thanks to the small bending distortions, the confined-doping approach works well in the bent large-mode-area fiber. Besides, the advantage of tandem pumping is also discussed in terms of preferential modal gain. A non-circular core fiber with a 41 μm short axis and 120 μm long axis was fabricated in-house. We evaluated the fiber in a linear laser cavity pumped by a 975 nm laser diode. The maximum output power obtained was 191 W with slope efficiency of approximately 67% with respect to launched pump power. The output signal has good beam qualities with M2 of ~1.5 and ~3.1 respectively, along short and long axis.

Fast quantitative fluorescence authentication of milkpowder and vanillin by a line-scan hyperspectralsystem

Li Jingwei, Wentao Jiang, Xinli Yao, Fuhong Cai, and Sailing He

Doc ID: 330143 Received 24 Apr 2018; Accepted 27 Jun 2018; Posted 28 Jun 2018  View: PDF

Abstract: We present a fast hyperspectral line-scan fluorescence imaging system to verify the feasibility of quantitativefluorescence authentication of powders. Vanillin, which is restricted for use in milk powder, especially in the milkpowder for infants, is mixed with milk powder in different mass concentrations (5%, 10%, 30%, 50%, 70%, and90%). Mixed powders are located on a motorized linear stage. A 405 nm line laser is utilized to excite thefluorescence of the sample. Based on galvo scanning, we can generate a laser line with high spatial resolution andhigh intensity density on the samples. An imaging spectrometer with a CMOS camera as detector is built. Thespectral range of the spectrometer is 365 nm-810 nm, with about 1 nm spectral resolution. One snapshot of theCMOS can acquire the fluorescent spatial and spectral information of a line-region in 100ms. By scanning themotorized linear stage, we obtain the fluorescence hypercube of the sample. A 100*1926*1216 hypercube, whichcovers an area of 15*5 mm2, is obtained in 50 seconds. The imaging speed can be enhanced further by increasingthe intensity of the excitation laser and the sensitivity of the area camera. Fully constrained least squares, a linearspectral mixture analysis, is utilized to analyze the hypercube obtained by our homemade imaging spectrometer,thus obtaining the pixel concentration of vanillin in each mixed powder. Linear regression analysis is used for thepixel concentration and mass concentration of vanillin. A linear relationship with coefficient of determination R2equal to one is observed, which demonstrates the capability of fluorescence hyperspectral quantitative analysis inpowders.

Semicylindrical microresonator: excitation, modalstructure, and Q factor

Hovhannes Haroyan, Henrik Parsamyan, Torgom Yezekyan, and Khachatur Nerkararyan

Doc ID: 327931 Received 10 Apr 2018; Accepted 27 Jun 2018; Posted 27 Jun 2018  View: PDF

Abstract: The semicylindrical microresonator with relatively simple excitation with plane wave is studied. The resonator isformed on the base of the dielectric / metal / dielectric structure, where the wave energy penetrates into resonatorthrough a thin metal layer and stored in a semicylindrical dielectric with high permittivity. The proposedmicroresonator combines features of Fabry-Perot and Whispering gallery mode resonators. Dependence ofradiation losses on the radius and materials are estimated by theoretical analysis, while excitation by a plane waveis shown via numerical analysis. The quality Q-factor of the resonator can achieve up to 104, at radius of asemicylinder of several microns..

Investigation of multiple laser shock peening on the mechanicalproperty and corrosion resistance of shipbuilding 5083Al underthe simulated seawater environment

Hao Wang, Yihui Huang, Wenwu Zhang, and Andreas Ostendorf

Doc ID: 330095 Received 23 Apr 2018; Accepted 27 Jun 2018; Posted 27 Jun 2018  View: PDF

Abstract: To investigate the effect of laser shock peening(LSP) with different LSP impacts on the mechanical property inartificial seawater and corrosion resistance of shipbuilding 5083Al alloy in 3.5% NaCl solution, the wear propertyand electrochemical corrosion resistance tests were performed by ball-on-disk sliding wear tester andelectrochemical workstation. The wear mass loss of samples treated by 1 and 3 LSP impacts are much lower by55.22% and 65.94% than it of untreated specimen in artificial seawater. Comparing with the untreated sample, theelectrochemical corrosion rate of samples decreased by 74.91% and 95.03% after treated by 1 and 3 LSP impactsrespectively. The reasons of enhancement of the wear property and electrochemical corrosion behavior werecaused by the increased residual stress and microhardness after LSP treatment.

Top-of-atmosphere reflectance over homogeneousLambertian and non-Lambertian surfaces

Tatiana Russkova and Tatiana Zhuravleva

Doc ID: 330421 Received 11 May 2018; Accepted 27 Jun 2018; Posted 27 Jun 2018  View: PDF

Abstract: In this study, the effects of the Lambertian assumption on the top-of-atmosphere reflectance areevaluated through comparison with calculations derived using a more detailed Bidirectional ReflectanceDistribution Function under different atmospheric, lighting and viewing conditions. The numerical experimentsare performed for background, dusty, and cloudy models of the atmosphere in spectral channels of 0.44 and 0.87μm. In the case of background or dusty medium over terrestrial surface, the overestimation of the top-ofatmospherereflectance in the forward scatter viewing direction and underestimation in the backscatter one isobserved. The angular range as well as magnitude of discrepancy is noticeably narrower and lower respectivelywhen the atmosphere is more turbid and the wavelength is shorter. The use of Lambertian assumption instead‘true’ ocean reflectance leads to a significant underestimation of the top-of-atmosphere reflectance in the forwardscatter direction and a moderate overestimation of reflectance in the backscatter one. The ocean reflectanceexhibits generally high dependence on wind which affects the reflected solar radiation distribution around theforward scatter direction. Analysis of simulation results for overcast sky showed that, in general, the multiplescattered radiation smoothes the anisotropy effects. However, there are conditions at which the choice of aBidirectional Reflectance Distribution Function model is significant: in the case of thin cirrus cloudiness over oceanat large solar zenith angles and stratus cloudiness with an optical thickness of at least 5 over a vegetation cover orocean in the near infrared region of the spectrum.

Optofluidic adaptive optics

Kaustubh Banerjee, Pouya Rajaeipour, Caglar Ataman, and Hans Zappe

Doc ID: 327131 Received 09 Apr 2018; Accepted 27 Jun 2018; Posted 28 Jun 2018  View: PDF

Abstract: We introduce a transmissive refractive adaptive optics system consisting of a deformable transparent optofluidic wavefront modulator operated with a sensorless wavefront error estimation algorithm. The wavefront modulator consists of a cavity, filled with an optical liquid, that is sealed by a deformable elastic polymer membrane. Deformation of the membrane is achieved through electrostatic actuation using transparent indium tin oxide electrodes buried in the cavity. Modulation of the two-dimensional phase distribution generated by the system is performed using open loop control both with and without active wavefront sensing. For the latter, a progressive modal decomposition algorithm is used to estimate and correct distortion inthe point-spread function of the wavefront arising due to the optical system and other sources of wavefront distortion.

Jones matrix physical parameters for media ininhomogeneous fields

Zhizhong Guo, Caiyun Mo, xiao hong, Guoqing Zhang, Wen bin Yu, and Gui zhong Wang

Doc ID: 331476 Received 10 May 2018; Accepted 26 Jun 2018; Posted 27 Jun 2018  View: PDF

Abstract: Inhomogeneous media are affected by a physical or electromagnetic field, where the off-diagonal elements of theJones matrix are complex numbers with both real and imaginary parts. Inhomogeneities of the electromagneticfield result in the eigenvalue coordinate system changing along the light path. In this study, we used the unitarytransformation to propose a Jones matrix of the inhomogeneous field induced medium with three physical orelectromagnetic parameters: the medium’s phase delay, induction angle, and inhomogeneous angle. This Jonesmatrix and the integral formulas of its three parameters are applicable to not only remarkable optical effects butalso for the light propagation process of inhomogeneous field induced media.

A Multiple View Polarimetric Camera

Philip Birch, Rupert Young, and C. Chatwin

Doc ID: 331946 Received 18 May 2018; Accepted 26 Jun 2018; Posted 27 Jun 2018  View: PDF

Abstract: A multiple view polarimetric camera is developed. The system uses four separate action cameras and software is employed to map the images onto each other in order to generate the Stokes vectors, the degree of linear polarisation and angle images. To ensure robustness, an automated calibration system has been developed that ensures the pixels are correctly mapped. Video frame synchronisation is also developed.

Phase-noise model for actively-linearized FMCW ladar

Thomas DiLazaro and George Nehmetallah

Doc ID: 332158 Received 18 May 2018; Accepted 26 Jun 2018; Posted 27 Jun 2018  View: PDF

Abstract: Understanding the effects of laser phase noise on frequency-modulated continuous wave distance measurements isimportant in evaluating ranging accuracy. The standard white frequency-noise assumption is commonly used topredict the ranging performance. However, other noise sources are typically present that can further degrade theheterodyne beat signal and make this assumption invalid. In addition, many ranging systems employ active sweeplinearization techniques that can impact the phase noise. Here, we present a phase-noise model for assessing theaccuracy of a phase-locked swept laser source.

Highly coherent supercontinuum in the mid – infraredregion with cascaded tellurite and chalcogenide fibers

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

Doc ID: 328906 Received 19 Apr 2018; Accepted 26 Jun 2018; Posted 26 Jun 2018  View: PDF

Abstract: We numerically investigate a 2-step supercontinuum generation using cascaded tellurite and chalcogenide fiberswith all-normal group velocity dispersion pumped by a femto second laser at 2 μm. The optimized tellurite fiber isa hybrid micro-structured optical fiber with a core surrounded by 12 rods. It has flat normal chromatic dispersionfrom 2 to 5 μm. The chalcogenide fiber is a double-core fiber with flat normal chromatic dispersion from 4 to 10μm. The output SC spectrum from the best candidate fibers spans from 0.78 to 8.3 μm with coherence of unity allover the spectrum. Such high coherence pulse with broad spectrum will be valuable for many applications intomography, ultrafast transient absorption spectroscopy, etc. The proposed fiber structures are all-solid which arefeasible for fabrication with common rod-in-tube method. This implies that 2-step supercontinuum is a potentialway for obtaining broad, highly coherent supercontinuum in the mid-infrared.

Single-angle Reflectance Spectroscopy to Determine the Optical Constants n and k: Considerations in the Far-Infrared Domain

Brent DeVetter, Nicole Scharko, Bret Cannon, Tanya Myers, and Timothy Johnson

Doc ID: 330397 Received 27 Apr 2018; Accepted 26 Jun 2018; Posted 09 Jul 2018  View: PDF

Abstract: Single-angle infrared reflectance spectroscopy is a proven and effective method for determining the complex optical constants n and k of condensed matter. The modern method uses a Fourier transform IR spectrometer to record the quantitative reflectance R(ν) spectra followed by application of the Kramers-Kronig transform (KKT) to obtain the complex optical constants. In order to carry out the KKT, it is essential to measure the reflectance spectra to as high and low a frequency (wavenumber) as possible. Traditionally, the reflectance spectra of solid specimens consist of large (typically, > 10 mm diameter) polished single-crystal faces free of defects or voids. The requirement of a large polished face, however, is not a realistic expectation for most synthetic, geologic or rare specimens where the size is usually small and the morphology can vary. In this paper we discuss several improvements and considerations to both the hardware and far-infrared measurement protocols that lead to more accurate R(ν) values and thus to more accurate n/k values, especially for small (millimeter-sized) specimens where the R(ν) spectrum is concatenated from multiple independent R(ν) spectra from overlapping hardware/spectral domains. Specifically, the improved hardware and analyses introduced here include: 1) Providing a set of far-IR calibration standards; 2) Custom-designing and manufacturing low reflectivity, stray-light reducing sample masks for small specimens; 3) Minimizing stray light interaction between the sample mask, the interferometer Jacquinot stop and the detector; 4) Optimizing the methods to "splice" together the spectra from independent domains; 5) Discussing what methods one can use to obtain or calculate the important R(0 cm-1) value; 6) Using a quartic relationship to extrapolate from the measured R data to R(0); and 7) Accounting for the limiting effects of diffraction for the spot size at the sample mask and detector for mm-sized specimens, especially at the very long wavelengths. These seven considerations are all highly interconnected and are discussed in turn, as well as their strong interdependencies. The paper presents a holistic approach for determining reliable n/k values of millimeter-sized samples using fixed-angle reflectance in the mid- and far-IR.

Ultra-compact reference ULE cavity

Alexandre Didier, Jacques Millo, Baptiste Marechal, Cyrus Rocher, Enrico Rubiola, Roméo Lecomte, Morvan Ouisse, Jérôme Delporte, Clement Lacroute, and Yann Kersale

Doc ID: 328389 Received 13 Apr 2018; Accepted 26 Jun 2018; Posted 05 Jul 2018  View: PDF

Abstract: We present a first experimental characterization of our ultra-compact, ultra-stable laser. The heart of theapparatus is an original Fabry-Perot cavity with a 25mmlength and a pyramidal geometry, equipped withhighly-reflective crystalline coatings. The cavity, along with its vacuum chamber and optical setup, fitsinside a 30 L volume. We have measured the cavity thermal and vibration sensitivities, and present a firstestimation of the cavity fractional frequency instability at sy(1s) = 7.510􀀀15.

Study on Skylight Polarization Patterns over the Oceanfor Polarized Light Navigation Application

Le Guan, Shiqi Li, Liyuan Zhai, Sheng Liu, Hui Liu, Wei Lin, Yan Cui, Jinkui Chu, and Huikai Xie

Doc ID: 331352 Received 10 May 2018; Accepted 25 Jun 2018; Posted 26 Jun 2018  View: PDF

Abstract: Polarized skylight navigation has excellent navigation performance with no error accumulation over time and lowsusceptibility to interferences. The skylight polarization distribution contains rich directional information such asthe solar meridian, the neutral point, and the polarization angle, which plays a key role in the polarizationnavigation. But up to now the polarizations of both sunlit and moonlit skies have been investigated mainly over theland. In this work, the polarization distribution patterns of the skylight over the East China Sea and the Yellow Seawere studied. The polarization patterns were captured continuously during daytime and nighttime by using a fullskyimaging polarimetry system, and then compared with the simulation results using the libRadtran - radiativetransfer software package. The result shows that the skylight polarization distribution over the sea has almost thesame pattern as that on the land. The accuracy of the angle of polarization and the degree of polarization droppedsignificantly under the cloudy sky. It was found that when the ship sailed on the sea, the direction of the realmeridian was close to the solar azimuth during the daytime and close to the lunar azimuth during the nighttime. Itwas also found that the nautical twilight polarization distribution was affected by both the solar polarization andthe lunar polarization, but the solar polarization was dominant. The experiments show that the skylightpolarization distribution pattern over the sea can still be applied in the field of polarization navigation. Thus it isfeasible for ships and unmanned aerial vehicles to use the polarized skylight to navigate and orient on the sea.

Novel Unimorph Deformable Mirror with anIntegrated Strain Feedback Layer

Fan Bin, Yifan Dai, Chaoliang Guan, guipeng tie, Chao Qi, and Yaoyu Zhong

Doc ID: 327925 Received 10 Apr 2018; Accepted 25 Jun 2018; Posted 26 Jun 2018  View: PDF

Abstract: The correction accuracy of a pint-sized unimorph deformable mirror (DM) is significantly influenced by the nonlinear hysteresis error ofpiezoelectric ceramics, especially in an open-loop state. Moreover, the control bandwidth is also reduced by the non-linearity. In this paper, wefabricated a three-unit pint-sized unimorph DM with strain gauges integrated on the actuators as a feedback layer for the first time. An experimentalplatform was built and utilized to test each electrode’s strain signal. Testing results show that, under quasi-static condition, the hysteresis curve ofmirror’s central displacement is corrected and the hysteresis rate could be reduced from 11% to less than 2% by adopting the strain feedback signal.More specifically, DM’s initial surface, Zernike defocus together with spherical aberration can also be corrected by this method, and the correctionaccuracy is improved more than 20% compared to the open loop state. By introducing a close-loop control the gaps of DMs under open loop issupplied. This demonstrates that adding strain feedback layer is promising to enhance the performance of unimorph DM.

Detection and identification of transformer windingstrain based on distributed optical fibre sensing

Yunpeng Liu, Yuan Tian, Xiaozhou Fan, Yanan Bu, and Bowen Wang

Doc ID: 328824 Received 20 Apr 2018; Accepted 25 Jun 2018; Posted 26 Jun 2018  View: PDF

Abstract: At present, transformer winding strain monitoring is mainly divided into off-line detection and on-line detection. Due tothe interference of the complex electromagnetic environment, on-line detection has not been widely used. Although offlinedetection is more mature, it can not accurately judge the winding strain form. Based on the above problems, thisresearch investigated a strain gauge strain detection method based on distributed fibre optic sensing, and proposes awinding strain identification method based on the S-transform and an extreme learning machine (ELM). First, thedeformation of the winding in the process of transformer operation is simulated, and the corresponding Brillouinfrequency shift is collected. Then, the time-frequency analysis of the strain signal is carried out using an S-transform, andthe transformed time-frequency feature is extracted as the input sample to the neural network. An ELM was used fortraining identification. Experimental results show that the method can effectively identify the common windingdeformation form, the recognition effect is better and the accuracy is high.

Double-wedge prism scanner for application in thermalimaging systems

Shian-Fu Lai and Cheng-Chung Lee

Doc ID: 330256 Received 30 Apr 2018; Accepted 24 Jun 2018; Posted 25 Jun 2018  View: PDF

Abstract: In this paper, double wedge prisms, known as Risley prisms, composed of two wedge prisms, is presented with assemblies infour configurations. In the double-wedge prism scanner, the center of the two wedge prisms are aligned with the optical axis;thus, the optical system and mechanical structure are simple. In contrast to conventional scanners, its assembly is compact,robust, and insensitive to vibrations and wobbles. However, the relationship between the deviated and rotated angles is notlinear, and the trajectory of the scan pattern is non-rectilinear, therefore double wedge prisms have rarely been used in imagingsystems as a one-dimensional scanner until now. This study presents the optical characteristics of double wedgeprisms and proposes methods to solve the problems mentioned above. The experimental results demonstrate that the doublewedge prisms can be used in an imaging system as a one-dimensional scanner.

Sky brightness and colour measurements during the 21 August 2017 total solar eclipse: COMMENT

Russell Sampson

Doc ID: 334229 Received 04 Jun 2018; Accepted 24 Jun 2018; Posted 09 Jul 2018  View: PDF

Abstract: While observing the August 21, 2017 total solar eclipse from Shoshoni, Wyoming the author briefly witnessed an annulus of red light about 2° to 3° from the center of the totally eclipsed sun. The author had no prior knowledge of this phenomenon, thus reducing the chances of observational bias. A simple experiment suggests that the phenomenon may not be the result of an afterimage illusion produced by observing the eclipse through binoculars. This appears to support the CCD color measurements of the sky during same eclipse [1].

Highly-sensitive carbon disulfide on-line detectionsystem based on deep ultraviolet absorptionspectroscopy, and its application in liquid-sealreliability assessment

Lin Wang, Yungang Zhang, Xue Zhou, and Zhiguo Zhang

Doc ID: 330994 Received 04 May 2018; Accepted 22 Jun 2018; Posted 25 Jun 2018  View: PDF

Abstract: This paper investigated a potential instrument for carbon disulfide in-situ measurement with high precision andstrong anti-interference capability. A compact and automated carbon disulfide detection system was developedusing a fiber opto-electronic sensing device. A custom software interface based on LabVIEW was developed. Multiwavelengthleast squares method based on differential optical absorption spectroscopy was employed forimproved detection and anti-interference capabilities of the system. The detection limit of the system (signal-tonoise= 3) was determined to be 1 ppb per meter. Using this scheme, the reliability of a liquid-seal was verifiedcarbon disulfide leakage. Although the liquid level of the liquid-sealed carbon disulfide showed no significantchange over 24 h, a residue concentration of over 30 ppm remained detectable on the surface.

Integrated Athermal Arrayed-waveguide GratingMultiplexer and Demultiplexer with All-metalCompensating Rod For Broadband TemperatureApplication

Xiaoping Wu, Chenglu Liu, Wen Liu, Changan Li, Zhilin Yuan, Chenggang Guan, Keyu Wu, Fengfan Tang, Yulan Min, HUi Chen, and Wenjun Liu

Doc ID: 328475 Received 16 Apr 2018; Accepted 22 Jun 2018; Posted 25 Jun 2018  View: PDF

Abstract: In this paper, a unique device which can act as both multiplexer and demultiplexer is proposed with two all-metalcompensating rods that makes the compensated chip almost the same spectrum profiles as the original one. In thisway a flat-top athermal AWG module of 100-GHz×40-ch is successfully fabricated. Small center wavelength shift of±25pm is achieved for the ultra-wide temperature range from -40 to 85°C with the low insertion loss change of lessthan ±0.14dB.

Simultaneous Achievement of Highly Birefringent andNonlinear Photonic Crystal Fibers with EllipticalTellurite Core

Min Liu, Hongtao Yuan, Ping Shum, Cong Shao, Haonan Han, and Lihua Chu

Doc ID: 328547 Received 16 Apr 2018; Accepted 21 Jun 2018; Posted 26 Jun 2018  View: PDF

Abstract: A novel photonic crystal fiber with an elliptical tellurite core is proposed to realize high birefringence and highnonlinearity simultaneously as well as low confinement loss at the wavelength of 1.55μm. The guiding properties,such as the birefringence, the nonlinearity and the confinement loss have been investigated by using the fullvectorial finite element method. The results show that the birefringence and the nonlinear coefficient can be up to7.57×10-2 and 188.39W−1 Km−1, respectively, and the confinement loss can be only 10-9 dB/m. The proposed PCF canfind potential applications in optical fiber sensing, polarization maintaining transmission, and super-continuumgeneration.

A broadband time resolved multi-channel fNIRSsystem to monitor in-vivo physiological changes ofhuman brain activity

Frederic Lange, Françoise Peyrin, and Bruno Montcel

Doc ID: 323340 Received 22 Feb 2018; Accepted 21 Jun 2018; Posted 22 Jun 2018  View: PDF

Abstract: We have developed a broadband Time Resolved multi-channel Near Infrared Spectroscopy system that canmonitor the physiological responses of the adult human brain. This system is composed of a supercontinuum laserfor the source part and of an ICCD camera coupled with an imaging spectrometer for the detection part. It allowsthe detection of the spectral, from 600 to 900 nm, and spatial dimensions as well as the arrival time of photonsinformation simultaneously. We describe the set up and its characterization in terms of temporal instrumentresponse function, wavelength sensitivity, and stability. The ability of the system to detect the hemodynamicresponse is then demonstrated. First, an in-vivo experiment on an adult volunteer was performed to monitor theresponse in the arm during a cuff occlusion. Secondly, the response in the brain during a cognitive task wasmonitored on a group of 5 healthy volunteers. Moreover, looking at the response at different time windows, wecould monitor the hemodynamic response in depth, enhancing the detection of the cortical activation. Those firstresults demonstrate the ability of our system to discriminate between the responses of superficial and deeptissues, addressing an important issue in fNIRS.

Investigation of Thermoforming Mechanism andOptical Properties Change of Chalcogenide Glass InPrecision Glass Molding

Lin Zhang, Wenchen Zhou, and Allen Yi

Doc ID: 330741 Received 30 Apr 2018; Accepted 21 Jun 2018; Posted 22 Jun 2018  View: PDF

Abstract: Chalcogenide glasses are emerging as enabling materials for low-cost infrared optics due to their transparency inshort-to-long wave infrared bands and the possibility to be mass produced by precision glass molding (PGM), anear net-shape process. This article is aimed to evaluate the thermoforming mechanism of As40S60 glass around itsglass transition temperature (Tg) and investigate its refractive index change and residual stresses in molded lensduring and after PGM. First, a constitutive model was introduced to precisely predict the material behavior in PGMby integrating subroutines into a commercial finite element analysis (FEA) software. This modeling approachutilizes the Williams-Landel-Ferry (WLF) equation and Tool-Narayanaswamy-Moynihan (TNM) model to describestress relaxation and structural relaxation behaviors, respectively. The numerical simulation revealed that thecooling rate above glass transition temperature (Tg) can introduce large geometry deviations to the molded opticallens. The residual stresses in a molded lens are generated mainly at the temperature around Tg due to theheterogeneity of thermal expansion from viscoelastic to solid state, while structural relaxation occurs during theentire cooling process. The refractive index variations inside molded lenses were predicted by performing FEMsimulation and further evaluated by measuring wavefront changes using an infrared Shack-Hartmann wavefrontsensor (SHS), while the residual stresses trapped inside the molded lenses were obtained by using a birefringencemethod. Combination of measurements of the molded infrared lenses and numerical simulation results providedan opportunity for optical manufacturers to gain better understanding of the mechanism and optical performanceof chalcogenide glasses during and after PGM.

Continuum removal for ground based LWIRhyperspectral infrared imagery applying non-negativematrix factorization

Bardia Yousefi, Saeed Sojasi, Clemente Ibarra-Castanedo, Xavier Maldague, Georges Beaudoin, and Martin Chamberland

Doc ID: 318836 Received 08 Jan 2018; Accepted 21 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: Continuum removal is vital in hyperspectral imageanalysis. It enables data to be used for any applicationand usually requires approximations or assumptionsto be made. One of these approximations isrelated to the calculation of the spectra of the background’sblackbody temperature. Here, we present anew method to calculate the continuum removal process.The proposed method eliminates the calculationfor ground-based hyperspectral infrared imageryby applying two acquisition sets before and after usingthe heating source. The approach involves a laboratoryexperiment on a long-wave infrared (7.7mmto 11.8mm - LWIR), with a LWIR-macro lens, an Infragoldplate and a heating source. To calculate thecontinuum removal process, the approach applies nonnegativematrix factorization (NMF) to extract Rank-1NMF, estimate the downwelling radiance and compareit with that of other conventional methods. NMF usesgradient-descent-based multiplicative rules (GD) andnon-negative least squares (NNLS) optimization algorithmsto obtain Rank-1 NMF. A comparative analysisis performed with 1%˘20% additive noise for all algorithmsby using the spectral angle mapper and normalizedcross correlation (NCC). Results reveal the promisingperformance of NMF-GD (average of 72.5% similaritypercentage using NCC) and NMF-NNLS (average of77.6% similarity percentage using NCC).

Windowed Fourier ridges for demodulation of carrierfringe patterns with nonlinearity: a theoreticalanalysis

Nimisha Agarwal, Chenxing Wang, and Kemao Qian

Doc ID: 332032 Received 17 May 2018; Accepted 21 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: Extracting phase or phase derivative accurately is the utmost requirement in optical metrology. However, inpractice, there are many error sources, among which nonlinear distortion in fringe patterns is often encountered.Several techniques have been proposed over time to remove the nonlinearity error. Among these techniques, thewindowed Fourier ridges (WFR) algorithm has been shown to be an effective solution insensitive to nonlinearity,but it lacks a theoretical justification. In this paper, we theoretically analyse the local frequency estimation errorand phase extraction error, which not only proves the mentioned insensitivity, but also supports performanceprediction and error control and thus is very important and useful in optical measurement practice. Thetheoretical results have been verified by computer simulations. Other error sources such as model error and noiseare also compared and discussed.

Interferometric Particle Imaging of ice particles usinga multi-view optical system

Mohamed Talbi, Gerard Grehan, and Marc Brunel

Doc ID: 328049 Received 10 Apr 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: Interferometric Particle Imaging (IPI) enables particle’s size estimation in a wide range [from 10 μm to a few millimeters]depending on the optical system design. With a multi-view optical system it is possible to extract more information about the 3Dmorphologyof the particle. In this study, multi-view interferometric out-of-focus imaging of ice particles is performed in abackward scattering configuration. It is used to estimate ice particle volume, and thus to reduce uncertainty concerning particle’ssize estimation. It is further used to better analyze the presence of nearby particles whose images overlap.

High resolution two-photon microscopy using pixel reassignment

Shiyi Sun, Shaocong Liu, Wensheng Wang, zhimin zhang, Cuifang Kuang, and Xu Liu

Doc ID: 331166 Received 08 May 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: An imaging system combines parallel detection and two-photon excitation is presented in this paper. In the proposed method, seven avalanche photodiodes (APD) are used in the detection path. The light is guided into the APD sensor by a fiber bundle with seven fibers. The circular arranged fiber end faces together function as a detection array. The outer contour fiber ends deviate from optical axis center and thus obtaining higher frequency information. Seven images are acquired simultaneously by the detection array. By using de-convolution and pixel reassignment to process the images acquired, both the resolution and the contrast of the final image are enhanced. The capability of image quality enhancement of the system constructed is demonstrated successfully both by theoretical simulation and experimental results.

Modeling for Detecting Weld Defects Based onMagneto-optical Imaging

Xiangdong Gao, Guohua Li, Ziqin Chen, Chongzhou Lan, Yanfeng Li, and Perry Gao

Doc ID: 319355 Received 08 Jan 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: Magneto-optical (MO) imaging non-destructive testing (NDT) method for ferromagnetic weldments has beenproposed. The mechanism of MO imaging was analyzed by the Faraday MO effect, magnetic domain theory andmagnetic hysteresis loops. Then the relation between MO images and their corresponding excitation voltages wasinvestigated. To explain the MO imaging system, magnetic domain distribution models of various welding stateswere established. These models are excited by two kinds of magnetic fields. One is the external magnetic field (Hex)and the other is a weldment remanence field (Mr) after Hex is removed. Relations of magnetic field excitationvoltages, thickness of the spacer plate and the corresponding MO images were also researched, which indicates theproposed NDT method can be used to detect incomplete penetration defect. Then, an experiment which uses MOimaging to detect the defects of high strength steel (HSS) weldment was performed. Experimental results provedthis method can detect crack, sag and incomplete penetration of weldment effectively. Finally, a series of weldedjoint MO images of the HSS weldment were captured, which are used as the input data of defect classification modelestablished by using principal component analysis (PCA) and error back propagation (BP) neural network, and theaccuracy of this classification model can achieve at 92.8%.

Bessel-like beam generated by an axicon based onparallel-plate waveguides

Tingting Shen, Tingting Lang, WU MENGRU, and Zhanghua Han

Doc ID: 325965 Received 14 Mar 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: The axicon is the simplest and most effective optical element for generating the zero-order Bessel-like beam. Thezero-order Bessel-like beam has the characteristics of small spot size, high brightness, good direction and largecollimation distance, can be applied to optical micro-manipulation and power transmission. In this paper, weproposed and designed a structure for phase manipulation based on PPWGs can be used to realize the functionalityof the axicon in the THz region. Meanwhile, we characterized the influence of the cone angle of the axicon and thewaist radius of the incident Gaussian beam on the generated zero-order Bessel-like beam by simulation. The planarstructure consisting of a parallel stack of thin copper plates can be easily fabricated to fulfill the phase requirementto realize the zero order Bessel-like beam, and also can be utilized in THz imaging systems, THz sensing systems,THz communication systems, etc.

Generation of optical Bessel beams with arbitrarilytrajectories using a magnetic-liquid deformable mirror

Mathieu Fortin, Michel Piche, Denis Brousseau, and Simon Thibault

Doc ID: 326759 Received 03 Apr 2018; Accepted 20 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: We propose a new strategy to curve the trajectory of the central lobe of a zero-order Bessel beam and a first-order Bessel beam along their propagation axis. Our method involves modifying the phase of a beamthat is incident on an adaptive mirror. As examples, we show that the most intense lobe of the beam can follow a parabolic trajectory, a cubic trajectory or a trajectory made by a combination of these orders. By using a phase correction emulating the effect of cylindrical mirrors, the central lobe always preserves its symmetry. Theoretical simulations were reproduced in laboratory using a magnetic-liquid deformable mirror. The parabolic trajectory of the 60-μm central spot of a zero-order Bessel beam exhibits a 0.6-mm off-axis shift after 30-cm length propagation.

DEVELOPMENT OF A PHOTOPOLYMER HOLOGRAPHIC LENS FORCOLLIMATION OF LIGHT FROM A GREEN LED

Sanjay Keshri, Kevin Murphy, Vincent Toal, Izabela Naydenova, and Suzanne Martin

Doc ID: 327494 Received 18 Apr 2018; Accepted 19 Jun 2018; Posted 21 Jun 2018  View: PDF

Abstract: A Holographic Optical Element (HOE) was developed to collimate a monochromatic Light Emitting Diode (LED). Thefabrication was achieved by the interference of collimated and diverging beams from a 532 􀢔􀢓 laser to producethe required photonic structure in a self-developing photopolymer material. The experimental values of diffractionefficiency and spatial period across HOE were compared with their expected theoretical values. Good agreementwas found for the spatial period however the diffraction efficiency varied significantly across the lens. In thispaper, two approaches have been taken to address this variation (i) modification of recording geometry (ii)optimization of recording intensity and exposure time at constant energy. The performance of an optimized HOE(cylindrical holographic lens) was then demonstrated using a 532 􀢔􀢓 laser beam. The optimized conditions for thecylindrical holographic lens was used to fabricate a spherical holographic lens of same numerical aperture for LEDapplication. This type of lens has the potential to be used in combination with LED sources.

Modeling Mutually Coupled Non-IdenticalSemiconductor Lasers on Photonic Integrated Circuits

Fabien Dubois, Masoud Seifikar, Alison Perrott, and Frank Peters

Doc ID: 327316 Received 29 Mar 2018; Accepted 19 Jun 2018; Posted 19 Jun 2018  View: PDF

Abstract: We model the situation of two lasers in a face to facearrangement, optically coupled through an attenuatingelement, where the distance between the lasers is ona scale typical in photonic integration (100’s of mm tomm’s). We acccount for the existence of a frequency differencebetween the two single moded lasers. A modifiedversion of the Lang-Kobayashi equations was employedto describe the interaction. By solving this delaydifferential equation (DDE) system we characteriseddifferent dynamical regimes including, one and twocolour states, and self pulsations. We focus on the effectvarying coupling strength and detuning betweenthe lasers has on the frequencies of the lasers. Using theresults of this frequency study, we identify the bifurcationscausing changes between the different frequencyregimes.

3D characterization of debris clouds underhypervelocity impact with pulsed digital inlineholography

Yonggang Zhou, Zhiliang Xue, Yingchun Wu, Aimin Xie, and Xuecheng Wu

Doc ID: 326950 Received 26 Mar 2018; Accepted 19 Jun 2018; Posted 20 Jun 2018  View: PDF

Abstract: The increasing space debris poses a great threat to in-orbit spacecrafts and satellites, because its hypervelocityimpact can bring about fatal mechanical and electrical damages to them. This work applies pulseddigital inline holography (DIH) to measure 3D positions and shapes of the debris clouds generated bythe hypervelocity impact in Whipple shield. Detailed operation procedures of synchronizing the pulseDIH system with the impact event and removing the strong plasma radiation are presented, ensuring thesuccessful capture of the transient state of ultrafast ejecta. Experiments on a 2.25 mm aluminum sphereimpacting on an 0.5 thickness aluminum target plate with a velocity of 3.6 km/s are carried out on thehypervelocity impact research center (HIRC) of China Aerodynamics Research and Development Center(CARDC), and results show that the holographic fringes are clearly recorded and the debris fragments arereconstructed and located accurately, agreeing well with the results measured by laser shadowgraph. Thiswork demonstrates the powerful capability and great potential of DIH in the diagnostics of hypervelocityimpact.

The Impacts of Collection System on Laser-inducedBreakdown Spectroscopy Signal Detection

Tianqi Li, Sahar Shata, Zongyu Hou, Jian Dong, and Zhe Wang

Doc ID: 330120 Received 24 Apr 2018; Accepted 15 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: Collecting strong enough and repeatable signals from laser-induced plasmas is the primary goal of the Laser-Induced Breakdown Spectroscopy (LIBS) optical detection systems. Typically, the light emitted from the plasma isrefracted by the lens, collected by the fibre, and measured by the spectrometer. In the present work, we establisheda three-dimensional model to systematically evaluate the overall emission collected from different position of theplasma for a typical optical collection system composed of a focus lens and a collection fibre and sensitivityanalyses were further performed. In addition, experimental were conducted and partially validated the model.Results showed that for the collection system with optical fibre located on the focal point of the collection lens, thecollection efficiency distribution is almost constant within a large cylindrical-shape area; while for that of locatedoff the focal point, there would be a rhombus-shaped area with higher collection efficiency than other areas. Thismuch higher collection efficiency area is small in size but has large impact on the detected spectral intensity. Thespatial distributed collection efficiency on the lens parameters such as size and position was further discussed toclarify the impacts of the collection system. Furthermore, sensitivity analysis were performed to evaluate theimpact of the collection system on the signal repeatability. Based on these calculations, recommendations for thedesign of the collection for optimized spectral intensity and stability were proposed.

Rectangular Structure Based Pose Estimation Methodfor Non-cooperative Rendezvous

Limin Zhang, Feng Zhu, Yingming Hao, and Wang Pan

Doc ID: 326394 Received 20 Mar 2018; Accepted 14 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: Pose estimation for spacecraft is widely recognized as an important technology for space applications. Many spacemissions require accurate relative pose between the chaser and the target spacecraft. Stereo vision is a usual meanto estimate the pose of non-cooperative target during proximity operations. In this paper, an accurate algorithmfor pose estimation is proposed by taking advantage of the geometric structure of the object. With stereo cameras,our approach employs the corners of the solar panel as features and uses bundle adjustment to improve theaccuracy. Simulation results demonstrate that our method improves the precision and robustness fornon-cooperative spacecraft pose estimation. Our laboratory experiments further validate the approach. Theresults show that the rotation angle error of our method is within 0.8°, and the measurement error in translation isless than 0.4% at the distance from 3m to 1.2m.

Stokes imaging spectropolarimeter based onchanneled polarimetry with full-resolution spectraand aliasing reduction

Chunmin Zhang, Naicheng Quan, and Tingkui Mu

Doc ID: 327503 Received 03 Apr 2018; Accepted 14 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: A Stokes channeled interference imaging spectropolarimeter with full-resolution spectra and aliasing reduction ispresented. The sensor uses a Wollaston prism, a Savart polariscope and a linear analyzer as birefringentinterferometer and two high-order retarders to incorporate channeled polarimetry employing tempo-spatiallymixed modulated mode with no internal moving parts and offers a robust system. The performance of the system isverified through laboratory tests. Compared with the previous sensors, the most significant advantage of thedescribed instrument is that the reconstructed spectra retain the resolution of the interferometer and the errors inthe reconstructed spectral resolved polarization state caused by aliasing between the interference channels aresuppressed effectively. Additionally, the advantages of the interferometer are maintained, such as compactstructure and high optical throughput.

Improved light collection in ICOS cells using non-axially symmetric optics

Benjamin Clouser, Laszlo Sarkozy, and Elisabeth Moyer

Doc ID: 326325 Received 22 Mar 2018; Accepted 11 Jun 2018; Posted 12 Jun 2018  View: PDF

Abstract: High effective path lengths and stable optical configuration make Integrated Cavity Output Spectroscopy (ICOS) a useful spectroscopic technique for measuring trace gases. However, the skewed nature of the output ray geometry of ICOS cavities makes it difficult to collect the already weak cavity output onto small detectors. We derive the constraining effect of skewness in ICOS cavities with Herriott alignments, which limits light collection efficiency for compact instrument designs, and show how this constraint can be overcome by addition of a non-axially-symmetric optical component. We demonstrate the efficacy of this approach with the ICOS-based Chicago Water Isotope Spectrometer (ChiWIS), which incorporates a skew-correcting optical element consisting of eight ZnSe wedges, and show that it increases collection efficiency by approximately a factor of six.

Simulated annealing optimization in wavefront shaping controlled transmission

Zahra Fayyaz, NAFISEH mohammadin, Faraneh Salimi, afreen fatima, mohammadreza rahimitabar, and Mohammad Avanaki

Doc ID: 319134 Received 17 May 2018; Accepted 24 May 2018; Posted 22 Jun 2018  View: PDF

Abstract: In this research, we present results of the simulated annealing (SA), a heuristic optimization algorithm, for focusing light through a turbid medium. The performance of the algorithm on phase and amplitude modulations has been evaluated. A number of tips to tune the optimization parameters are provided. Moreover, the effect of measurement noise on the performance of the SA algorithm is explored.

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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