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Spectroscopic investigation of molecular formation in laterally colliding laserproduced carbon plasmas

ARVIND SAXENA, R K Singh, Hem Joshi, and Ajai Kumar

Doc ID: 342560 Received 22 Aug 2018; Accepted 12 Dec 2018; Posted 12 Dec 2018  View: PDF

Abstract: We report detailed spectroscopic investigation of carbon dimer productionin the stagnation layer formed due to laterally colliding plasma plumes under vacuum and N2 ambient. Two spatially separated Nd : YAG laser pulses are used to generate plasma plumes in close proximity from a solid graphite target. A comparative optical emission spectroscopic study of stagnation layer and single carbon plasma plume is carried out for finding optimum experimental conditions for carbon dimer (C2) production. Significant enhancement in the C2 production is observed in stagnation layer as compared to that observed in single plume. Further, substantial increase in carbon dimer formation is monitored by introducing N2 gas. Along with carbon dimer, CN emission is also observed in the emission spectra. Spatio-temporal evolution of C2 and CN emission reveals that the yield of carbon dimer production is maximum close to the target surface, and decreases with increase in time as well as spatial position. On the contrary, CN emission increases with the target distance. The dominant pathways for CN formation are suggested, and it is demonstrated that C2 acts as a precursor for CN formation. The above observation is correlated with cooling of ejected carbon species in the collisional regime and the estimated vibrational temperature of C2.

A image spherizing-based planeness detectingmethod for micro-channel plate

Ran Zhao, Yonggang Huang, Jiuwang Wang, Yong Sun, Kangsheng Huang, You Zhou, Yun Wang, and Yang Fu

Doc ID: 347044 Received 28 Sep 2018; Accepted 12 Dec 2018; Posted 12 Dec 2018  View: PDF

Abstract: Based on the mathematical models proposed by image spherizing algorithm, a novel planeness detecting methodfor micro-channel plate(MCP) is presented. After describing the theory of image spherizing algorithm, a straightline image is chosen as standard picture and the imaging simulation for deformed MCP is performed. According tothe simulated results, deformation characteristic of MCP and the mechanism of image twisting phenomenon wereanalysed. Finally, the scheme of double lines method that specialize in planeness detection is proposed. Theexperimental result obtained by interferometer shows that the profile characteristics of deformed MCP isconsistent with the theoretical analysis. To verify the effectiveness of the double lines method, we measured theplaneness of 100 pieces of MCP and then defined the detecting standard: a micro-channel plate will be treat asdefective product when the twisting angle of two orthogonal lines in the reflected image is greater than 40°,whereas the product will meet the military standard when the twisting angle is smaller than 7°. In this method, theplaneness detection could be completed only by observing the reflected image of MCP even in harsh environment.In particular, the accuracy can reach 1 μm and it has been applied to the production process of MCP.

Thermal Emission Spectroscopy for SingleNanoparticle Temperature Measurement:Optical System Design and Calibration

Bryan Long, Daniel Rodriguez, Chris Lau, and Scott Anderson

Doc ID: 347912 Received 19 Oct 2018; Accepted 12 Dec 2018; Posted 12 Dec 2018  View: PDF

Abstract: We discuss the design of an optical system that allows measurement of 600 nm to1650 nm emission spectra for individual nanoparticles (NPs), laser heated in anelectrodynamic trap in controlled atmospheres. An approach to calibration of absoluteintensity vs. wavelength for very low emission intensities is discussed, and examples of NPgraphite and carbon black spectra are used to illustrate the methodology.

Comparison of different schemes for stimulated Brillouinscattering enhancement

Ilya Golub, Ahmad Atieh, and Pranav Mohanan

Doc ID: 349665 Received 30 Oct 2018; Accepted 12 Dec 2018; Posted 12 Dec 2018  View: PDF

Abstract: A comparison of different schemes to enhance Stimulated Brillouin Scattering (SBS) in single mode opticalfiber is performed. Specifically, we evaluated SBS generation efficiency in a 3 Km length fiber with andwithout power recycling vs same fiber placed in a ring resonator and in a ring resonator in a recyclingconfiguration. For the latter case, a large number of both odd and even higher-order Stokes and anti-Stokesharmonics is generated. We show that the choice of a scheme is dictated by specific application. In addition,when incorporating a ring resonator in a Sagnac loop a flat optical frequency comb is generated..

Design of off-axis three-mirror systems with ultrawidefield of view based on an expansion process ofsurface freeform and field of view

Qingyu Meng, Hongyuan Wang, Wenjing Liang, zhiqiang yan, and Bingwen Wang

Doc ID: 341504 Received 06 Aug 2018; Accepted 11 Dec 2018; Posted 12 Dec 2018  View: PDF

Abstract: Unobscured reflective optical systems with wide field of view (FOV) have significant application values. However,the aberration will increase with the increase of the system FOV, so the wide-FOV system is difficult to design. Inthis paper, a design method which is effective to achieve the off-axis three-mirror systems with ultra-wide FOV isproposed. In this method, the system FOV is expanded stepwise in design process, and the surface optical freeformpolynomial terms are extended based on the judgment of image quality and some constraint conditions, and finalto obtain a prospective ultra-wide FOV system. A freeform off-axis three-mirror imaging system with a focal lengthof 1000mm, an F-number of 10, and an ultra-wide FOV of 80°×4° is designed as an example. This design resultshows that the system has a high imaging quality of RMS wavefront error (WFE) value of 0.040λ (λ=0.633μm), andit demonstrates that the method is effective to achieve the off-axis three-mirror systems with an ultra-wide FOV.

Extended light source based lens-less microscopy using constrained and regularized reconstruction

SANJEEV KUMAR, Manjunatha Mahadevappa, and Pranab Dutta

Doc ID: 349382 Received 26 Oct 2018; Accepted 11 Dec 2018; Posted 12 Dec 2018  View: PDF

Abstract: Lens-less microscopy is a simple, portable and cost effective method of microscopy. It has been extensively investigated with coherent light sources such as laser setups or partially coherent light sources such as LED filtered with a pinhole aperture. The coherence of light has a direct influence on the resolution of reconstructed object. This paper presents lens-less microscopy with a spatially extended light source (white LED flashlight without any subsequent engineering). A reconstruction method based on constrained and regularized optimization has been presented. The resolution reduced due to decreased coherence is gained by the presented method of object estimation.

Dispersion compensation by a liquid lens (DisCoBALL)

Michael Durst, Anthony Turcios, Colin Laurence, and Emma Moskovitz

Doc ID: 346579 Received 25 Sep 2018; Accepted 11 Dec 2018; Posted 12 Dec 2018  View: PDF

Abstract: We present dispersion compensation by a liquid lens (DisCoBALL), which providestunable group-delay dispersion (GDD) that is high speed, has a large tuning range, and usesoff-the-shelf components. GDD compensation is crucial for experiments with ultrashort pulses.With an electrically tunable lens (ETL) at the Fourier plane of a 4 f grating pair pulse shaper, theETL applies a parabolic phase shift in space and therefore a parabolic phase shift to the laserspectrum, i.e., GDD. The GDD can be tuned with a range greater than 2 105 fs2 at a rate of 100Hz while maintaining stable coupling into a single mode fiber.

Security analysis and enhancement of a cryptosystembased on phase truncation and a designed amplitudemodulator

YI XIONG, Aohan He, and Chenggen Quan

Doc ID: 346117 Received 17 Sep 2018; Accepted 11 Dec 2018; Posted 11 Dec 2018  View: PDF

Abstract: In this paper, the security of a cryptosystem based on phase-truncation and a designed amplitude modulator (AM)is evaluated. In the cryptosystem, an undercover AM used as an additional key is added to modulate the amplitudeinformation of the spectrum in the Fourier plane. Compared to the conventional phase-truncated Fouriertransform (PTFT)-based cryptosystem, the security of the cryptosystem is improved by increasing the number ofunknown keys. However, it is found that the designed AM is irrelative to the plaintext and one of the parameters inthe designed AM contributes less to the security enhancement of the cryptosystem due to low key sensitivity. Basedon the analysis, a special attack containing two iterative processes is proposed to crack the cryptosystem, in whichthe KPA-based iterative process I with a specific normalization operator is used to retrieve the designed AM andthe amplitude-phase retrieval technique-based iterative process II is used to retrieve the corresponding plaintextfrom the arbitrarily given ciphertext with the help of the retrieved AM. In addition, an inherent drawback widelyexisting in PTFT-based cryptosystems is reported for the first time: most information of the original image could beretrieved using two correct phase keys (or only the first phase key) generated in the encryption process evenwithout the corresponding ciphertext in PTFT-based cryptosystems. To address this issue, a security-enhancedcryptosystem is proposed in this paper. Numerical simulation is carried out to demonstrate the effectiveness andfeasibility of the proposed attack and cryptosystem

Field enhanced nanofocusing of radially polarized light by tapered hybrid plasmonic waveguide with periodic grooves

Ji Xu, Kang Li, Sicheng Zhang, Xinyi Lu, Nannan Shi, Zhaohuan Tan, Yuqing Lu, Ning Liu, Baifu Zhang, and Zhongcheng Liang

Doc ID: 348860 Received 25 Oct 2018; Accepted 11 Dec 2018; Posted 11 Dec 2018  View: PDF

Abstract: This study reports the field enhanced nanofocusing of radially polarized light by tapered hybrid plasmonic waveguide (THPW) with periodic grooves. The THPW consists of a conical high-index dielectric cone, a sandwiched low-index dielectric thin layer and a metal cladding. Axially symmetric 3D finite element method is used to investigate the nanofocusing effect. Under radially polarized illumination at 632.8 nm, strongly enhanced nanofocusing occurs. The hybrid plasmonic structure reduces the energy loss effectively, and improve the field enhancement to nearly 554 times. Furthermore, periodic grooves are constructed on the metallic surface of the THPW, satisfying the phase matching condition and couple light energy from the inside to the outside. Finally, optimized nanofocusing performance with field enhancement about 1810 times is obtained. The results offer important reference for designing related photonic devices and the proposed scheme could be potentially exploited in applications of light–matter interactions.OCIS codes: (240.6680) Surface plasmons, (050.6624) Subwavelength structures, (260.5430) Polarization, (180.4243) Near-field microscopy.http://dx.doi.org/10.1364/AO.99.099999

High-efficiency, broadband, and wide-angle alldielectricquarter wave plate based on anisotropicelectric and magnetic dipole resonances

Jiaqi Yang and Tian Lan

Doc ID: 349298 Received 25 Oct 2018; Accepted 11 Dec 2018; Posted 11 Dec 2018  View: PDF

Abstract: Metadevices based on dielectric nanostructure with excitation of electric and magnetic resonances have shown highefficiency for polarization control compared with conventional manipulating methods as well as plasmonic structuremetadevices. Since both the electric and magnetic dipole resonances can be precisely adjusted by optimizing geometricparameters of the resonators to meet the desired wavelength, this paper proposes an approach to implement the hightransmittance metadevices operating at preferred wavelengths. By employing this method, we demonstrate an alldielectricquarter wave plate (QWP) metasurface with high transmittance (>85%) and high polarization conversionefficiency (>0.88) in a broad telecom waveband. At the same time, conversion efficiency is nearly unaffected for incidentangles within 75°. With features of high transmittance, wide-angle and invertible linear to circular polarizationconversion, the all dielectric QWP can be a good replacement for plasmonic metasurface devices and offers a furtherstep in developing polarization and phase manipulation metadevices.

Temperature Sensor Based on Multi-layer MoS2Coated Etched Fiber Bragg Grating

Sridhar S, Suneetha Sebastian, and Sundarrajan Asokan

Doc ID: 347585 Received 05 Oct 2018; Accepted 10 Dec 2018; Posted 10 Dec 2018  View: PDF

Abstract: The development of an etched Fiber Bragg Grating (eFBG) based temperature sensor with a uniform multi-layermolybdenum-di-sulphide (MoS2) coating, is presented in this paper; Multi-layer MoS2 has been coated on cladetched FBG sensor by DC magnetron sputtering of molybdenum (Mo) and subsequent sulfurization. Thedependence of temperature sensitivity on coating thickness of MoS2 on eFBGs has been tested from roomtemperature to 100oC. It has been found that MoS2 coated clad etched FBG sensors with a coating thickness ofaround 10nm exhibit a maximum temperature sensitivity of ~95pm/°C (almost one order higher than that of bareFiber Bragg Gratings), with a resolution of ∼ 0.01°C obtained using a FBG interrogator of with 1pm resolution.

Tapered Tellurite Step-Index Optical Fiber for Coherent Near-to-mid-IR Supercontinuum Generation: Experiment and Modeling

Than Singh Saini, Trung Hoa Nguyen Phuoc, Tong Tuan, Luo Xing, Takenobu Suzuki, and Yasutake Ohishi

Doc ID: 348962 Received 22 Oct 2018; Accepted 10 Dec 2018; Posted 10 Dec 2018  View: PDF

Abstract: We demonstrate a broadband highly coherent near-to-mid-IR supercontinuum generation using a short length oftapered tellurite step-index fiber pumped with ultrafast laser in normal dispersion regime. The tapered telluritefiber possesses all-normal dispersion characteristic within the whole range of the generated supercontinuumspectrum. A highly coherent near-to-mid-IR supercontinuum spectrum spanning 1.28 to 3.31 μm at -40 dBintensity level is obtained using a 3.2 cm long tapered tellurite fiber when it is pumped with 200 fs laser pulse ofpeak power of 19.8 kW at 2 μm. To obtain supercontinuum spectrum, we also carried out the numerical modelingfor the tapered tellurite step-index fiber with the same geometrical parameters and pump conditions used in theexperiment. The numerical observation supports the experimentally obtained result. The findings of this workshow that the fabricated tapered tellurite step-index fiber is a promising nonlinear medium to obtain a coherentnear-to-mid-IR supercontinuum spectrum in a short length of the fiber.

The non-hot-image-plane intense fringe from double scatterers in anintense laser beam through cascaded Kerr medium disks

Jianhua Zhou and Donghua Li

Doc ID: 347106 Received 01 Oct 2018; Accepted 09 Dec 2018; Posted 10 Dec 2018  View: PDF

Abstract: We theoretically investigate beam properties in a laser system of two scatterers with cascaded Kerrmedium disks. A non-hot-image-plane intense fringe may appear when an intense laser beam which ismodulated by double scatterers, passing through cascaded Kerr medium disks. It is found that besidesgenerating hot images at expected positions, a new intense fringe appears at a position of about tens ofcentimeters downstream of the hot-image plane. The intensity of this intense fringe is greater than thatof the first hot image and it is sufficient to damage the optical elements. The effect of object distance,wavelength and width of scatterer on the properties of this intense fringe is investigated and we findthat this intense fringe appears under certain conditions. Its intensity is closely related to several factorssuch as the distance from the scatterer to the first Kerr medium disk, the scatterer width and thewavelength of the incident beam, as well as the position of this intense fringe is not varied with theobject distance.

Planar antenna array as highly-sensitive terahertz sensor

Fei Shen, Jianyuan Qin, and Zhanghua Han

Doc ID: 345954 Received 14 Sep 2018; Accepted 09 Dec 2018; Posted 11 Dec 2018  View: PDF

Abstract: In this paper, a planar comb-shaped antenna array for terahertz sensing based on the excitation of spoof surface plasmon modes is proposed. The structure is constructed by an array of three periodic rectangular grooves perforated through metal stripes on top of a silicon substrate. The effective detection of lactose is given as an example to demonstrate the ability of this structure to enhance the detection sensitivity. In the transmission mode, the sensing signal of lactose using antenna array was 7.6 times larger than that of using a silicon substrate. In the reflection mode, the sensing signal of lactose increased almost 13 times using our proposed antenna array compared to that of using a silicon substrate, exhibiting a high sensitivity in terahertz sensing. Further, lactose thickness could be predicted based on the reflectance at the peak using our proposed structure. Our results indicated that the proposed structure has great potentiality in the field of biological and chemical sensing.

Focus prediction in digital holographic microscopy using deep convolutional neural networks

Tomi Pitkäaho, Aki Manninen, and Thomas Naughton

Doc ID: 346136 Received 18 Sep 2018; Accepted 08 Dec 2018; Posted 10 Dec 2018  View: PDF

Abstract: Deep artificial neural network learning is an emerging tool in image analysis. We demonstrate its potential in the field of digital holographic microscopy by addressing the challenging problem of determining the in-focus reconstruction depth of Madin-Darby canine kidney cell clusters encoded in digital holograms. A deep convolutional neural network learns the in-focus depths from half a million hologram amplitude images. The trained network correctly determines the in-focus depth of new holograms with high probability, without performing numerical propagation. This paper reports on extensions to preliminary work published earlier as one of the first applications of deep learning in the field of digital holographic microscopy.

Direct phase unwrapping method based on a local third order polynomial fit

Alejandro Téllez-Quiñones, Ricardo Legarda-Saenz, Adán Salazar-Garibay, Juan Valdiviezo-N, and MIGUEL LEON-RODRIGUEZ

Doc ID: 351289 Received 06 Nov 2018; Accepted 08 Dec 2018; Posted 10 Dec 2018  View: PDF

Abstract: When recovering smooth phases by phase unwrapping algorithms, many non-iterative algorithms are available. However, normally those algorithms offer approximations of the current phase that cannot be accurate enough. This is because the majority of them are based on global approaches, instead of local ones. Although the smooth estimations are not often expected in phase reconstructions for real applications, a smooth initial guess could be useful for the robust iterative techniques. Therefore, based on the most recent local polynomial approaches, we propose a simple least square fitting of the partial derivatives of the phase, normally estimated from the wrapped operator, by considering local polynomial models of the phase up to the third order. Synthetic and real data of wrapped phases are considered in our work.

Velocimetry Based on Dye Visualization for a Pulsatile Tubing Flow Measurement

Zifeng Yang and Mark Johnson

Doc ID: 349764 Received 01 Nov 2018; Accepted 08 Dec 2018; Posted 11 Dec 2018  View: PDF

Abstract: A dye visualization experiment was designed and operated as an analogy of the X-ray angiographic imaging. The velocimetry technique based on dye visualization for a pulsatile tubing flow measurement is introduced. Optical flow method was utilized to recover the velocity field from the visualization images. For the same flow condition, a digital Particle Image Velocity (PIV) system was also employed to measure the same flow field in the middle plane. The purpose of this study was to determine the accuracy of the velocity field estimation from the transmittance-based two-dimensional projection image of the three-dimensional volumetric flow field by dye visualization in comparison with the PIV measurement results. Compared to the PIV results in the middle plane, the averaged velocity magnitude from the dye visualization measurement was underestimated by about 16% - 24% in the central region and by about 29% - 43% in the outer region across the tube at two time instants of the cyclic pulsatile flow.

Control of resonance mode using finestructured grating: towards high resolvingpower filter

Xin He, Jinliang Jie, Junbo Yang, Yunxin Han, and Sen Zhang

Doc ID: 347197 Received 01 Oct 2018; Accepted 07 Dec 2018; Posted 10 Dec 2018  View: PDF

Abstract: A bandstop filter with high resolving power is designed for mid-infraredspectroscopic sensing and imaging applications. By utilizing truncated grating consistingof multiple gold nanowires in each unit cell of the periodic structure, compression of thestop bandwidth and improvement of the resonance extinction are realized simultaneously.It shows only single stop band at ~4.474 μm with 15 dB extinction and >80% backgroundtransmission over a wide spectral range. The obtained narrow linewidth (~1.45 nm)enables a spectral resolving power higher than 3000. Flexible control of the filteringperformance is investigated by adjusting the variety of geometrical parameters. Moreover,the structure may have potential applications in refractive index sensing.

Degenerate Four-Wave Mixing for measurement of Magnetic Field using a Nanoparticles-Doped Highly-Nonlinear Photonic Crystal Fiber

N Nagarajan, Peng Zu, Vasantha Jayakantha Raja R., NORBERTO ARZATE, and vigneswaran dhasarathan

Doc ID: 348245 Received 15 Oct 2018; Accepted 07 Dec 2018; Posted 07 Dec 2018  View: PDF

Abstract: A novel magnetic-field sensor based on degenerate four-wave mixing (DFWM) technique is theoreticallyproposed using a As2S3-core silica-cladding photonic crystal fiber (PCF). In order to enhance the sensitivity,we put forth a novel design of highly-nonlinear PCF where the silica cladding is doped with either Au,Ag or Al metallic nanoparticles. The effect of volume fraction of the nanoparticles within the claddingand the size of nanoparticles are considered as the control parameters in designing the magnetic-field PCFsensor to obtain high sensitivity using this novel DFWM scheme. The PCF structure of the proposed sensoris optimized with the proposed pitch of 3 um and airhole diameter of 2.78 um. We consider a pumpingcontinuous-wave laser light with a wavelength of 2100 nm in the mid-IR regime. It has been found that,the optimized PCF with Al-SiO2-cladding with small volume fraction and small nanoparticle size possessmagnetic-field sensitivity values of 2.74 and -0.058 nm/Oe for the Stokes and anti-Stokes gain lines.

The reconstruction method based on the Hilbert fractal curve recovery sequence in Fourier Ptychography Microscope

Chen Xin, Haobo cheng, yongfu wen, Hengyu Wu, and Yingwei Wang

Doc ID: 346938 Received 27 Sep 2018; Accepted 06 Dec 2018; Posted 07 Dec 2018  View: PDF

Abstract: Many Fourier ptychography microscopy (FPM) techniques have been proposed to achieve higher recovery accuracy in the past few years, little is known that their reconstructed quality is also depended on the choice of recovery sequence, which is important for fast solution convergence during the Fourier ptychography (FP) reconstruction process. In this paper, we propose to use the Hilbert fractal curve, which is one of the most representative of classic space filling curves, as a new kind of recovery sequence of mesh LED array and validate its effectiveness and robustness with both simulated and real experiments. Results show that the Hilbert fractal curve as the recovery sequence is a better choice for periodic LED array, compared with the raster lines, spiral lines and wave-shaped curve three recovery sequences.

Tunable circular dichroism from a bilayer rotational F4 nanostructure arrays

Jianxia Qi, Mingdi Zhang, yunguang Zhang, Qingyan Han, wei gao, RunCai Miao, and jun dong

Doc ID: 347708 Received 10 Oct 2018; Accepted 06 Dec 2018; Posted 10 Dec 2018  View: PDF

Abstract: A chiral nanostructure array is designed, which is composed of bilayer rotationalF4 configuration. The surface plasmon resonance and circular dichroism are studiedby changing the parameters of the structure, such as the size of the structure and thespacing between the upper and lower layers. The results show that the structure hasstrong circular dichroism, which are strongly dependent on structural parameters. Intheory, based on the Born-kuhn model, the upper and lower nanostructures areequivalent to electric dipoles. By analyzing the coupling mode of electric dipoles inthe upper and lower layer, the mechanism of circular dichroism and the shift of thecircular dichroism resonance are revealed. The suggested chiral nanostructure can beused to biological targeted molecular detection and spectral sensing.

Optical design of a compact multi-spectral LED light source with high irradiance and uniformity

Zhiliang jin, daxi xiong, Jianfei Dong, Wang Haiyang, weimin Li, Liquan Guo, and Peipei wang

Doc ID: 347030 Received 01 Oct 2018; Accepted 05 Dec 2018; Posted 06 Dec 2018  View: PDF

Abstract: As light emitting diodes (LEDs) become dominating solutions in general lighting, their applications are also penetrating into biomedical engineering, especially light therapies. These new applications usually require much higher light power density at a shorter working distance than general lighting. Besides the high power, uniformity in the power distribution is another important factor in such applications to illuminate the samples with equal irradiance. These factors require designing a compact optical system to transmit the light from a highly integrated high power LED light source. While the existing designs mainly focus on providing desired illuminance in much larger target space, little work has been devoted to the optical design to achieve a high irradiance that is uniformly distributed on a target area with a short distance away from the light source. This work proposes a design method to solve such a problem, based on a highly integrated LED module, a mixing rod and a pair of aspheric lenses. Both numerical simulations and experiments by a prototype are performed, which have verified the effectiveness of the proposed method.

Liquid-Crystal Based Fabry–Perot Interferometer Displacement Sensor

BOYI SONG, JIANYANG HU, CHUNLI XIA, HAI ZHANG, Yue Lv, Weimin Sun, and yongjun liu

Doc ID: 348848 Received 24 Oct 2018; Accepted 05 Dec 2018; Posted 06 Dec 2018  View: PDF

Abstract: A Fabry–Perot interferometer (FPI) displacement sensor is proposed and demonstrated. This sensor is prepared by inserting two ceramic ferrules into a polydimethylsiloxane (PDMS) hose to generate a Fabry–Perot cavity. The cavity is filled with liquid crystals (LCs), which induces a Vernier effect due to the birefringence of LCs. The flexible PDMS hose makes the cavity length adjustable. A displacement sensor with the sensitivity of ∼2.97 nm/μm and dynamic range of 0.9 mm at the center wavelength of 1550 nm is experimentally demonstrated.

Deep-turbulence wavefront sensing using digitalholography in the on-axis phase shifting recordinggeometry with comparisons to the self-referencinginterferometer

Douglas Thornton, Mark Spencer, and Glen Perram

Doc ID: 346495 Received 28 Sep 2018; Accepted 05 Dec 2018; Posted 05 Dec 2018  View: PDF

Abstract: In this paper, we study the use of digital holography in the on-axis phase shifting recording geometry forthe purposes of deep-turbulence wavefront sensing. In particular, we develop closed-form expressionsfor the field-estimated Strehl ratio and signal-to-noise ratio for three separate phase-shifting strategies—the four-, three-, and two-step methods. These closed form expressions compare favorably with our detailedwave-optics simulations, which propagate a point-source beacon through deep-turbulence conditions,model digital holography with noise, and calculate the Monte-Carlo averages associated with increasingturbulence strengths and decreasing focal-plane array sampling. Overall, the results show thefour-step method is the most efficient phase-shifting strategy and deep-turbulence conditions only degradeperformance with respect to insufficient focal-plane array sampling and low signal-to-noise ratios.The results also show the strong-reference beam from the local oscillator provided by digital holographygreatly improves performance by 10’s of dB when compared with the self-referencing interferometer.

Optimization of the optical particle counter for onlineparticle measurement in high-pressure gas

Lifeng Lu, Xiaolin Wu, Zhongli Ji, Zhiyi Xiong, and Mingxing wang

Doc ID: 349256 Received 25 Oct 2018; Accepted 05 Dec 2018; Posted 05 Dec 2018  View: PDF

Abstract: With the aim to achieve fast and accurate on-line measurement of particle size and concentration in different highpressuregas, the application of optical particle counter (OPC) is extended from atmospheric pressure to high-pressure conditions(more than 2 MPa). But with the increase of the gas pressure, the performance of OPC is reduced resulting in the error of testedparticle size. In order to resolve this problem, an optimization model of optical window thickness is established for the optical sensorof OPC based on the geometric optics theory. The effects of gas pressure, temperature and medium on the optimized model areanalyzed, which are helpful to improve the accuracy of the optical sensor. Finally, the feasibility, reliability and accuracy of themethod are verified through experiments.

Quantitative determination of Ta and Nb intantalum-niobium ore using laser-inducedbreakdown spectroscopy

Zhong Qi Hao and Li Liu

Doc ID: 349943 Received 01 Nov 2018; Accepted 04 Dec 2018; Posted 05 Dec 2018  View: PDF

Abstract: Tantalum-niobium ore is the main source of Ta and Nb metal, which is very important rare metal. However, it isstill a challenge for laser-induced breakdown spectroscopy (LIBS) to quantitative detect trace Ta and Nb elementsin tantalum-niobium ore samples. In this work, LIBS assisted with univariate and multivariate calibration methodswere used to quantitative determine Ta and Nb elements under optimized experimental parameters, such as delaytime, gate width, and analytical lines. The results show that LIBS with multivariate calibration methods is a feasiblemethod, and the LoDs of Ta and Nb elements were 59.21 and 8.02 μg g-1, respectively. It provides a promising wayfor the rapid and sensitive quantitative detecting of trace Ta and Nb elements in tantalum-niobium ore samples.

Cyphertext-only attack on the joint-transform-correlator-based optical encryption: experimental demonstration

Lei Wang, Guowei Li, Quanying Wu, and Guohai Situ

Doc ID: 346610 Received 24 Sep 2018; Accepted 04 Dec 2018; Posted 05 Dec 2018  View: PDF

Abstract: A cyphertext-only attack (COA) on a joint transform correlator (JTC) encryption system is proposed. Under the proposed COA scheme, the energy spectral density (ESD) of the plaintext can be calculated with the cyphertext, and then the plaintext information can be recovered by using a phase retrieval algorithm such as the hybrid input-output algorithm. We also numerically and experimentally demonstrated the cyphertext-only attack to verify the feasibility of the proposed technique.

Highly sensitive polarimetric camera (B-BOP) forSPICA mission

Obaid Adami, Louis Rodriguez, Albrecht Poglitsch, Sophie Bounissou, Vincent REVERET, Abdelkader Aliane, Valerie Goudon, and Laurent Dussopt

Doc ID: 346987 Received 27 Sep 2018; Accepted 04 Dec 2018; Posted 05 Dec 2018  View: PDF

Abstract: The SPICA mission has just been selected by the European Space Agency (ESA) as one of the three candidate missionsto be further studied for the medium size mission M5.B-BOP, formerly named POL, is one of the three scientific instruments of SPICA which aims, among other scientificgoals, to map the galactic filamentary structures and their associated magnetic fields. With a novel interlaced-shapeddesign, B-BOP will contain 1344 pixels, operating within a temperature range of 50-100 mK, covering a 2.6 arcminfield of view, and delivering imaging polarimetry in three spectral bands: 100 μm, 200 μm and 350 μmsimultaneously. In this paper, we investigate by numerical simulations the mechanical, electromagnetic andthermoelectric behaviors of B-BOP detectors and predict for the three bands (i) a sufficient mechanical stability, (ii) agood electromagnetic absorption higher than 95 %, (iii) a high response value better than 1011 V/W and (iv)especially a very low NEP reaching 1 aW/Hz1/2 at 50 mK.

Measurement of Mid-Frequency Wavefront Error forLarge Optical Components with Ptychography

Xuejie Zhang, Bei Cheng, Cheng Liu, Weixing Shen, Xue Dong, Xiaojun Ma, and Jianqiang Zhu

Doc ID: 347900 Received 10 Oct 2018; Accepted 04 Dec 2018; Posted 05 Dec 2018  View: PDF

Abstract: In high power laser system, the wavefront quality of large optical components in mid spatial frequency band playsa critical role in system performance and safe operation. A simple and efficient method based on ptychography isused to measure mid-frequency wavefront error, which has the advantages of simple structure, strong antiinterfereability, flexible frequency-range selection and low cost. It has excellent frequency response in the entiremid-frequency region. The transfer function is demonstrated to be greater than 0.7 at 1/2 Nyquist frequencies(8.33mm-1) for 60mm field-of-view experimentally. The method has been successfully applied to the wedge focusedlens (WFL) to achieve high-fidelity measurement. Without any auxiliary lens, the power spectrum of WFL at thefrequency of interest is obtained through large aperture measurement. This technique is especially suitable foroptical components difficult to be measured using interferometers and opens up a new perspective for measuringmid-frequency wavefronts.

3D Shape Shearography Technique for Surface Strain Measurement of Free-Form Objects

Andrei Anisimov, Mariya Serikova, and Roger Groves

Doc ID: 348519 Received 16 Oct 2018; Accepted 04 Dec 2018; Posted 05 Dec 2018  View: PDF

Abstract: Shearography is a non-destructive testing technique that provides full-field surface strain characterization. Previously inspection of flat objects or simple geometric shapes has been reported. However, real-life objects especially in aerospace, transport or cultural heritage are not flat, but their inspection with shearography is of interest for both hidden defect detection and material characterization. Accurate strain measurement of a highly curved or free-form surface needs to be performed by combining in-line object shape measuring and processing of the shearography data in 3D. Previous research has not provided a general solution for that. The paper presents a new approach of 3D shape shearography which is based on the integration of a structured light projector for in-line shape measuring with 3D shearography. For the experimental part, a 3D shape shearography system prototype was developed and its performance was evaluated with a cylinder specimen loaded by internal pressure and compared with strain gauges.

Multi-step phase aberration compensationmethod based on optimal principal componentanalysis and subsampling for digitalholographic microscopy

Xiangyu Zhang, Jiasong Sun, Zuxin Zhang, Yao Fan, Qian Chen, and Chao Zuo

Doc ID: 345169 Received 06 Sep 2018; Accepted 04 Dec 2018; Posted 04 Dec 2018  View: PDF

Abstract: Digital holographic microscopy (DHM) is well-known powerful technique allowingmeasurement of the spatial distributions of both the amplitude and phase produced by a transparentsample. Nevertheless, in order to improve the transverse resolution of the DHM system, amicroscope objective has to be introduced in the object beam path, which inevitably leads tophase aberration in the object wavefront. During past decades, a multitude of techniques havebeen proposed to compensate this phase aberration, and among which the principal componentanalysis (PCA) technique has proven to be one of the most promising approach due to its highcompensation accuracy, low computational complexity, and simplicity to implement. However,when it comes to high-order phase aberration which is common for a mal-aligned DHM system,the PCA technique usually performs poorly since it is unable to fit the cross-terms of the standardZernike polynomials. To address this problem, here we propose a multi-step phase aberrationcompensation method based on optimal PCA and subsampling where PCA is firstly appliedto remove the non-cross aberration terms and then followed by the sub-sampled fitting forthe remaining cross aberration correction. The key advantage of our approach is that it canhandle both the conventional objective phase curvature and the high-order aberrations suchas astigmatism and anamorphism with very little computational overhead. Simulation andexperimental results demonstrate that our method outperforms state-of-the-art approaches and thecompensation results are consistent well with those obtained from the double exposure method.

Double square rings with different dimensionsproduce multiple absorption bands

Zeng Qu, Yong Zhang, and Binzhen Zhang

Doc ID: 346879 Received 27 Sep 2018; Accepted 04 Dec 2018; Posted 04 Dec 2018  View: PDF

Abstract: The quantity of absorption bands is traditionally less than the quantity of resonator sub-units. Based on absorptiontheory of electromagnetic resonance, three millimeter waves metamaterial absorbers (MWMAs) based on periodicresonators with double square rings (DSRs) are proposed, discussed, fabricated and measured. Multipleabsorption bands including two, three, and four bands can be effectively achieved by adjusting DSRs dimensions.The electric field distributions at corresponding resonance frequency can adequately explain the physicalmechanism of adjustable absorption bands affected by the strong LC, dipole and surface responses complexly.Detailed influence produced by sizes and materials are elaborated. The adjustable absorption can be easily scaledto the entire spectrum by geometrical regulation. The presented MWMAs show attractive prospects inelectromagnetic devices, biological sensing, material detection, and function materials because of its sizeadaptation, flexible design, ultrathin thickness, strong flexibility, and convenient fabrication.

Improving reconstruction of specklecorrelation imaging by using a modified phaseretrieval algorithm with the number ofnonzero-pixels constraint

Meihua Liao, da lu, Wenqi He, Giancarlo Pedrini, Wolfgang Osten, and Xiang Peng

Doc ID: 346880 Received 27 Sep 2018; Accepted 04 Dec 2018; Posted 04 Dec 2018  View: PDF

Abstract: Speckle correlation imaging (SCI) has been considered as one of the mostpromising techniques for computational imaging through a scattering medium. However, theimage quality is not always acceptable in conventional SCI, especially when a complex objectis involved. In this work, a modified phase retrieval algorithm is introduced to significantlyimprove the imaging quality of SCI. In the proposed scheme, a number of nonzero-pixels(NNP) constraint, rather than the real and nonnegative constraint, is employed as the objectdomain constraint of the iterative algorithm in the image reconstruction process. Experimentalresults are presented to show the performance enhancement of this scheme, inclusive of lessiterations, better image quality and higher reliability in comparison with the conventional SCImethod.

Subdivision of Brillouin gain spectrum to improve thespatial resolution of a BOTDA system

Jiang Chao, Xiaoyan Wen, ZHU run, Min Li, Haifei Lu, and Kai Su

Doc ID: 347667 Received 08 Oct 2018; Accepted 04 Dec 2018; Posted 04 Dec 2018  View: PDF

Abstract: A pulse subdivision analysis method was developed to improve the spatial resolution of a conventional long pumppulse Brillouin optical time domain analysis (BOTDA) system. An exclusive photodetector was used to get theaccurate energy distribution along the long pulse, based on which the long pulse was subdivided into severalsub-pulses with certain energy weights. With these energy weights the Brillouin spectrum generated by the longpulse was subdivided into equal numbers of sub-spectra. Each sub-spectrum could provide the detailed sensinginformation on a fiber sub-segment related to a sub-pulse. Thus the actual spatial resolution of the BOTDA systemwas determined by the sub-pulse instead of the long pulse. As a result, spatial resolution was several timesincreased, depending on the subdivision multiples. The method was theoretically simulated and thenexperimentally demonstrated. For experimental demonstration the recognition capability of the method to themelting point of two different fiber sections and the discrete strain distribution along a sensing fiber wasrespectively tested. For melting point recognition, thanks to 5-multiple subdivision, a 1 m spatial resolution over31 km sensing fiber was realized using a 50 ns pump pulse. For strain sensing test ten-multiple subdivision wasperformed to distinguish two 0.5 m stretched fiber sections with a 0.2 m interval using a 20 ns pump pulse. Thespatial resolution is 0.2 m, which is ten times improved compared with that before subdivision analysis. Due to itssimple and cost effective characteristic, the method was believed to have extensive application prospects indistributed fiber sensing fields.

Supernumerary bows: caustics of a refractive sphereand analysis of the relative overall Gouy phase shiftof the supernumerary rays

Paul Etienne Ouellette

Doc ID: 343112 Received 23 Aug 2018; Accepted 04 Dec 2018; Posted 05 Dec 2018  View: PDF

Abstract: The modified Young’s theory of interference related to the supernumerary rainbows is based on a differenceof 90 in the Gouy phase shifts for the parallel rays producing these bows. An observation screenplaced at a given distance from a refractive sphere illuminated by a point source of light should also showsupernumerary screenbows. An extensive description and analysis of the caustics involved is given. Forany k order, k being the number of reflections inside the sphere, a procedure is established to determinethe number of Gouy phase shifts encountered by any ray along its path from the source to the screen.Special consideration is given to the order k = 0. For any k supernumerary bow, on any spherical screenwhose center is that of the sphere, the difference in the Gouy phase shifts for the two rays producing abow always amounts to 90. An indirect proof of this characteristic is given. All considerations are madewithin the framework of geometrical optics being, on the one hand, the limit of the electromagnetic theoryas the wave length goes to 0, and being, on the other hand, complemented by the Gouy phase shifttheory.

Numerical simulation and experimentalverification of dense multi-view full-resolutionautostereoscopic 3D display based dynamicshutter parallax barrier

Yang Meng, Zhongyuan Yu, Chunyu Zhang, Ye Wang, Yumin Liu, Han Ye, and Laurence Chen

Doc ID: 345623 Received 12 Sep 2018; Accepted 03 Dec 2018; Posted 04 Dec 2018  View: PDF

Abstract: We come up with a practical setup and simulation for building up a glasslessautostereoscopic 3D display system based on the concept of “eye space” with dynamic shutterparallax barrier. “Eye space” is designed based on geometrical optics to get multi-view asmuch as possible through adjusting width of slit and parallax barrier dynamically. Thedynamic parallax barrier is placed in front of the display screen to form the shutter screen.The addressable drive circuit controls the switches of pupil windows on the shutter screen.The two signals are synchronous that drive circuit and frame frequency scanning of displayscreen. The shutter parallax barrier makes it possible that all right and left eyes in the “eyespace” see their own views simultaneously. The numerical simulation and experimentalverification with simplified 1D pupil windows and FPGA-based driving circuit unit arementioned in this paper, which have good practical value.

Super-multiview integral imaging scheme based on sparse camera array and CNN super-resolution

Ren Hui, Qiong-Hua Wang, Yan Xing, Min Zhao, luo ling, and Huan Deng

Doc ID: 345852 Received 18 Sep 2018; Accepted 03 Dec 2018; Posted 04 Dec 2018  View: PDF

Abstract: In this paper, we propose a scheme based on sparse camera array and convolution neural network (CNN) super-resolution for super-multiview integral imaging. Especially, the proposed scheme is adequate to not only the virtual-world three-dimensional (3D) scene with high performance and efficiency, but also the real-world 3D scene with higher availability than the traditional methods. In the proposed scheme, we firstly adopt the sparse camera array strategy to capture the sparse viewpoint images and use these images to synthesize the low-resolution (LR) elemental image array (EIA), then the CNN super-resolution scheme is used to restore the high-resolution (HR) EIA from the LR EIA for super-multiview integral image display. Experimental results verify the feasibility of the proposed scheme.

Multiple Just-Noticeable-Difference Based No-Reference Stereoscopic Image Quality Assessment

Zijin Gu, Yong Ding, Ruizhe Deng, Xiaodong Chen, and Andrey S. Krylov

Doc ID: 346163 Received 19 Sep 2018; Accepted 03 Dec 2018; Posted 04 Dec 2018  View: PDF

Abstract: Just Noticeable Difference (JND) is an important characteristic of human visual system (HVS), and there alreadyexist some matured JND models imitating the perception of human eyes. However, their utilization in stereoscopicimage quality assessment (SIQA) remains limited. To better simulate how HVS senses 3D images under noreferencesituation, a novel SIQA method based on multiple JND models is proposed in this paper. In our metric, thestereoscopic image pairs are decomposed into multi-scale monocular views and binocular views. Then, texture andedge information of these multi-scale images are extracted. Next, a 2D JND model, a binocular JND model and adepth JND model are separately applied to the extracted features and the depth map. Finally, these features aresynthesized and mapping to objective scores. Through experiment and comparison, the proposed method shows acompetitive advantage over most state-of-art SIQA methods, which indicates that it has a promising prospect inpractical applications.

Recording digital color information ontransparent polyethylene films by thermaltreatment

Alexander Kondratov, Vladislav Yakubov, and Alex Volinsky

Doc ID: 346345 Received 21 Sep 2018; Accepted 03 Dec 2018; Posted 04 Dec 2018  View: PDF

Abstract: This study characterizes the use of transparent low-density polyethylene laminatefilms for the purpose or recording digital information in the form of linear and color twodimensionalmatrix codes that are distinguishable in polarized light. Color characteristics ofmultilayer laminated materials made from polyethylene and heat treatment methods forchanging their coloring are examined. The contribution of the number of multilayer filmsinterfaces to the lightness and color of the laminate is shown. Melt-extruded industrialpolyethylene films’ heat treatment methods by convection, conduction, and radiation, tocontrol their optical characteristics and color in polarized light, are studied.

Spectral, spatial, and survivability evaluation of aflash-dried plasma-etched nanotube spray coating

Matthew Spidell, Davis Conklin, Christopher Yung, Evangelos Theocharous, and John Lehman

Doc ID: 342969 Received 23 Aug 2018; Accepted 03 Dec 2018; Posted 04 Dec 2018  View: PDF

Abstract: We demonstrate improved manufacturability of spectrally flat detectors for visible to mid-infrared wavelengths bycharacterizing a carbon nanotube spray coating compatible with lithium tantalate and other thermal sensors. Comparedagainst previous spray coatings, it demonstrated the highest responsivity yet attained due to both higher absorptivityand thermal diffusivity while also being matured to a commercially available product. It demonstrated spectral nonuniformityfrom 300 nm to 12 μm less than 1 % with uncertainty (k = 2) under 0.4 %. The spatial non-uniformity of theassembled sensor was less than 0.5 % over the central half (4 mm) of the absorber. As with previous developmentsemploying isotropic carbon nanotube coatings, the absorber surface was sufficiently robust to withstand cleaning bycompressed air-blast and survived repeated vacuum cycling without measurable impact upon responsivity.

High-precision grating period measurement

Thanarwut Photia, Wipawee Temnuch, Sorakrai Srisuphaphon, Nuttanan Tanasanchai, Waranont Anukool, KUNAREE WONGRACH, PACHARA MANIT, Surasak Chiangga, and Sarayut Deachapunya

Doc ID: 344380 Received 28 Aug 2018; Accepted 03 Dec 2018; Posted 04 Dec 2018  View: PDF

Abstract: We introduce a method for measuring a periodic structure, particularly a gratingperiod. The method is based on the high-precision laser Talbot effect. The combination of arubidium-locked external cavity diode laser and the Talbot interferometer provides an excellentand simple tool for this purpose. Some experimental results are provided to demonstrate theapproach.

Lithium Ion Detection in Liquid with LowDetection Limit by Laser-Induced BreakdownSpectroscopy

Yage He, xianshuang wang, Shuai Guo, Angze Li, Xiangjun Xu, Nasrullah Wazir, chunjie ding, tianqi lu, lingling xie, Min Zhang, Yan Hao, Wei Guo, and ruibin liu

Doc ID: 348974 Received 22 Oct 2018; Accepted 02 Dec 2018; Posted 07 Dec 2018  View: PDF

Abstract: Lithium, as the lightest metal and the most important powerful material inbattery fabrication, is widely used in many field. The fast detection of Li isnecessary for industrial application. The slow-speed detection methods,including atomic absorption spectroscopy (AAS) and inductively coupledplasma mass spectroscopy (ICPMS) with high-accuracy and low limit ofdetection, are hardly to be utilized in in-situ industrial control due to complexpre-preparation of samples. Here, through the analysis of the typicalspectrum line at Li I 670.79 nm, Li ions in water were detected quantitativelyin one minute including sample preparation by laser-induced breakdownspectroscopy (LIBS) with filter paper as adsorption substrate. The calibrationcurve by polynomial function fitting is used to predict the Li+ concentration.The limit of detection (LOD) as low as 18.4 ppb is obtained, which is muchlower than the results ever reported by using filter paper. The related factorR² reaches 99% and the prediction error is lower than 2%, proving the fastand on-line monitor for Li+ by LIBS is feasible. Furthermore, by comparisonwith the results with filter paper enrichment, the Li+ detection from waterdirectly shows higher LOD to 10.5 ppm. Moreover, the plasma images, bygate controlled intensified charge-coupled device (ICCD), illustrate differentmorphology and evolution between that on water surface and filter papersurface through visual observation. This study provides experimental andtheoretical experience in a fast way for the quantitative detection of thelightest metal ion (Li+) in liquid.

Entanglement in ladder-plus-Y-double quantum dot structure via entropy

hakeem al-ameri, M. Abdullah, and Amin Al-Khursan

Doc ID: 344366 Received 28 Aug 2018; Accepted 02 Dec 2018; Posted 03 Dec 2018  View: PDF

Abstract: The quantum entropy in ladder-plus-Y double quantum dot (DQD) systemwas calculated. The controlling parameters that are examined are: Four coherentoptical fields, three tunneling components, and an incoherent optical pumping.This work differs from others by the inclusion of wetting layer (WL) and thecalculation of momenta for each transition. The results show that the entropydepends on the difference between the carrier occupations in the states of thesetwo quantum dots (QDs). It is also shown that the probe optical field reduces theentropy while the pumping field increases it. Turned off the main tunnelingcomponent removes the entropy. High WL-QD momentum increases theentropy. Taking the same value of momentum for all transitions (the case ofother works) underestimates the entropy.

Receiver Performance Characteristics ofSingle Photon Lidar in Strong BackgroundEnvironment

Cheng Wu, Wenge Xing, Linghao Xia, Huixin Huang, and Chi Xu

Doc ID: 344869 Received 04 Sep 2018; Accepted 02 Dec 2018; Posted 03 Dec 2018  View: PDF

Abstract: The detection performance of the single photon lidar (SPL) receiver is investigatedas a function of optical attenuation and the superconducting nanowire single-photon detector(SNSPD) parameters (detection efficiency and dead time) in strong background environment.With the detection theory, it is found that there is an optimal attenuation to make the detectionprobability the highest at a given false alarm probability, namely optimal working conditions.Optical attenuation is proved to be required only when the background photon number ishigher than a certain value, otherwise it is not necessary. Furthermore, the performance ofGeiger-mode avalanche photodiode (GMAPD) is compared. Under optimized workingconditions, the SNSPD-based receiver exhibits a higher detection performance in strongbackground environment than that of GMAPD-based receiver due to shorted dead time.While in low-noise environment, the attenuation is not essential and the detection efficiencybecomes the dominant factor. The theoretical result gives a reference for the SPL receiversystem design to achieve the optimal detection performance.

Versatile photoacoustic spectrometer based on a mid-infrared pulsed optical parametric oscillator

Laurent Lamard, David Balslev-Harder, Andre Peremans, Jan Petersen, and Mikael Lassen

Doc ID: 347881 Received 10 Oct 2018; Accepted 02 Dec 2018; Posted 03 Dec 2018  View: PDF

Abstract: We demonstrate the usefulness of a nanosecond pulsed single-mode mid-infrared (MIR) optical parametric oscillator (OPO) for Photoacoustic (PA) spectroscopic measurements. The maximum wavelength ranges for the signal and idler are 1.4 $\mu$m to 1.7 $\mu$m and 2.8 $\mu$m to 4.6 $\mu$m, respectively, and with a MIR output power of up to 500 mW. Making the OPO useful for different spectroscopic PA trace-gas measurements targeting the major market opportunity of environmental monitoring and breath gas analysis. We perform spectroscopic measurements of methane (CH$_4$) nitrodioxide (NO$_2$) and ammonia (NH$_3$) in the 2.8 $\mu$m to 3.7 $\mu$m wavelength region. The measurements were conducted with a constant flow rate of 300 ml/min, thus demonstrating the suitability of the gas sensor for real time trace gas measurements. The acquired spectra are compared with data from the Hitran database and good agreement is found. Demonstrating a resolution bandwidth of 1.5 cm$^{−1}$. An Allan deviation analysis shows that the detection limit for methane at optimum integration time for the PAS sensor is 8 ppbV (nmol/mol) at 105 seconds of integration time, corresponding to a normalized noise equivalent absorption (NNEA) coefficient of 2.9$\times 10^{-7}$ W cm$^{-1}$ Hz$^{-1/2}$.

Weighted-least-squares multi-filter phase imagingwith partially coherent light: Characteristics ofannular illumination

Yijun Bao, Dong George, and Thomas Gaylord

Doc ID: 347935 Received 11 Oct 2018; Accepted 01 Dec 2018; Posted 03 Dec 2018  View: PDF

Abstract: Multi-filter phase imaging with partially coherent light (MFPI-PC) is a promising microscopic quantitative phaseimaging method that measures the phase of a transparent object. In the present work, a weighted-least-squaresversion is developed and applied to the important case of annular illumination. The resulting improved algorithmshave largely solved the noise magnification problem associated with the original MFPI-PC in annular illumination.Simulation and microlens experiments are used to validate the new QPI method for the case of annularillumination.

Structure parameter of anisotropic atmosphericturbulence expressed in terms of anisotropy factorsand oceanic turbulence parameters

Yahya Baykal, Yalçın Ata, and Muhsin Gökçe

Doc ID: 345192 Received 06 Sep 2018; Accepted 01 Dec 2018; Posted 03 Dec 2018  View: PDF

Abstract: The structure parameter of the anisotropic atmospheric turbulence is expressed in term of atmospheric, oceanic anisotropy factors in xand y directions and the oceanic turbulence parameters which are the wavelength, link length, ratio of temperature to salinitycontributions to the refractive index spectrum, the rate of dissipation of mean-squared temperature and the rate of dissipation of kineticenergy per unit mass of fluid. For the purpose of expressing the structure parameter of the anisotropic atmospheric turbulence in term ofatmospheric, oceanic anisotropy factors and the oceanic turbulence parameters, the spherical wave scintillation indices which are foundin weak anisotropic atmospheric turbulence and in weak oceanic turbulence are equated to each other. We aim to utilize this structureparameter expressed in this paper, in the evaluations of various physical entities such as the average intensity, scintillation index, beamspread in anisotropic oceanic turbulence by exploiting the existing solutions for the same physical entities in anisotropic atmosphericturbulence. Use of this structure parameter will help us to obtain the anisotropic oceanic turbulence results easily since such results willbe found by just inserting the structure parameter expressed in this paper to the already reported corresponding results of anisotropicatmospheric turbulence.

Compound period grating coupler for doublebeams generation and steering

Dachuan Wu, Wei Guo, and Yasha Yi

Doc ID: 344382 Received 27 Aug 2018; Accepted 30 Nov 2018; Posted 03 Dec 2018  View: PDF

Abstract: Grating couplers are one of the most basic integrated photonic structures. It hasraised tremendous research interest due to its outstanding performance in compact nonmechanicalbeam steering. Here we propose a new compound period grating coupler formedby combining two grating structures with different periodicities. The new compound periodgrating coupler structure can couple the waveguide mode into two radiation modes withdifferent angles. Therefore, the beam steering range is doubled due to the extra beam. Wenumerically demonstrate this idea, and a 26.20° steering range is observed within awavelength tuning range of 1500 nm to 1600 nm. The compound period grating structurewith DBR (distributed Bragg reflector) as the substrate is also numerically demonstrated, andits energy leakage to the substrate is highly suppressed. In addition, the investigation offabrication tolerance shows that the new structure can be fabricated with the current CMOStechnology.

Simulation of grating compressormisalignment tolerances and mitigationstrategies for chirped-pulse–amplificationsystems of varying bandwidth and beam size

Benjamin Webb, Mark Guardalben, Christophe Dorrer, Sara Bucht, and Jake Bromage

Doc ID: 347057 Received 28 Sep 2018; Accepted 30 Nov 2018; Posted 30 Nov 2018  View: PDF

Abstract: The effects of pulse compressor grating misalignment on the pulse duration and focusability are simulatedfor chirped-pulse–amplification systems of varying bandwidth, beam size, groove density, and incident angle. Tiltalignmenttolerances are specified based on a 2 drop in focused intensity, illustrating how tolerances scale withbandwidth and compressor beam size, which scales with energy when transformed via known grating damagethresholds. Grating-alignment tolerance scaling with grating groove density and incident/diffracted angles isinvestigated and applied to compressor design. A correlation between grating tip and in-plane rotation errorsensitivity is defined and used to compensate residual out-of-plane angular dispersion, even for ultra-broadbandpulses. Simulation of dispersion compensation methods after grating misalignment are shown to mitigate pulselengthening, limited by temporal contrast degradation and higher-order effects for ultrabroad bandwidths.

Spectropolarimetric measurement based on fast-axis-adjustablephotoelastic modulator

Rui Zhang, Zhi WANG, Wu li, Yuanyuan Chen, Jing Ning, ya qiao, and yang xie

Doc ID: 338170 Received 09 Jul 2018; Accepted 30 Nov 2018; Posted 30 Nov 2018  View: PDF

Abstract: A fast-axis-adjustable photoelastic modulator (Faa-PEM) is developed and studied, and a spectropolarimetric imagingmethod using the Faa-PEM and an acousto-optic tunable filter (AOTF) is presented. The Faa-PEM modulation retardation amplitudeand fast axis direction of the Faa-PEM can be adjusted by adjusting the two drives with no mechanical rotation. The I, Q, and U ofthe Stokes parameters of the incident light can be obtained by adjusting the retardation amplitude and fast axis direction of theFaa-PEM. This measurement method does not require high-frequency components, and thus a general area array detector can realizethe measurement. Theoretical simulation analyses show that the relative errors ΔI/I, ΔQ/Q, ΔU/U and ΔDoLP/DoLP are less than5.6%, and that the deviation error ΔAoLP is less than 0.2° (@ I=1.00, Q = 0.707, U = 0.707, V = 0.0,-0.1° ≤ Δθ0 ≤ 0.1°, and -0.05 rad≤ Δδ0 ≤ 0.05 rad). A prototype was developed and tested. The test results show that the average absolute relative error of the degreeof linear polarization is 0.36%, and the average absolute deviation error of the angle of linear polarization (AoLP) is 0.048°. Themethod has potential application value to spectropolarimetric imaging technology.

Characterizing Vortex Beams from a SpatialLight Modulator with Collinear Phase ShiftingHolography

Jasmine Andersen, Samuel Alperin, Andrew Voitive, William Holtzmann, Juliet Gopinath, and Mark Siemens

Doc ID: 341337 Received 01 Aug 2018; Accepted 29 Nov 2018; Posted 30 Nov 2018  View: PDF

Abstract: We demonstrate collinear phase shifting holography for measuring complex optical modesof twisted light beams with orbital angular momentum (OAM) generated by passing a laserthrough a spatial light modulator (SLM). This technique measures the mode along the direction ofpropagation from the SLM and requires no additional optics, so it can be used to aid alignment ofthe SLM, to efficiently check for the effects of beam wander, and to fully characterize generatedbeams before use in other experiments. Optimized error analysis and careful SLM alignmentallow us to generate and measure OAM with purity as high as 99.9%.

Enhanced circular dichroism of tilted zigzag-shaped nanohole arrays

Xiaoyu Feng, Yu Bai, Zhimin Jing, Qu Yu, Tiankun Wang, HAMAD ULLAH, and Zhongyue Zhang

Doc ID: 345749 Received 12 Sep 2018; Accepted 29 Nov 2018; Posted 30 Nov 2018  View: PDF

Abstract: Circular dichroism (CD) of nanostructures is in great demand for applications in biological molecules, photocurrent devices, and photocatalysis. Planar nanostructures can be prepared in concise manners, and their CD effects have gained much research interest. In this study, tilted zigzag-shaped nanohole (TZSN) arrays are proposed and the CD effect is studied by finite element method. A strong resonance occurs in the gap by tuning the charge distributions between adjacent nanoholes. Meanwhile, the CD effect of TZSN arrays is strongly dependent on the structural parameters of TZSN. Results provide a novel method for tuning the CD effects of nanohole arrays on a film.

Weighted least-squares phase unwrapping algorithm based on the orientation coherence for discontinuousoptical phase patterns

Biyuan Li, Chen Tang, Qiuling Zhou, and Zhenkun Lei

Doc ID: 345821 Received 14 Sep 2018; Accepted 29 Nov 2018; Posted 30 Nov 2018  View: PDF

Abstract: Phase unwrapping is one of the key steps of optical interferogram analysis, among which the phase discontinuity isstill a challenging problem. In this paper, we propose a new weighted least-squares phase unwrapping algorithmfor discontinuous optical phase patterns. In the proposed algorithm, the orientation coherence is introduced todefine the new weighting coefficient which can accurately show the wrapped phase quality. According to ourproposed algorithm, the new weighting coefficient has a good performance on distinguishing the continuousregions and the discontinuous regions in wrapped phase patterns. This advantage of our algorithm can ensure amore reliable unwrapped result for discontinuous optical phase patterns. We test the proposed algorithm on thecomputer-simulated speckle phase images and two experimentally obtained phase images, respectively, andcompare them with the other five widely used methods. The experimental results demonstrate the performance ofour new weighted least-squares phase unwrapping algorithm.

Pulsed upconversion imaging of mid-infrared supercontinuum light using an electronically synchronized pump laser

Laurent Huot, Peter Moselund, Peter Tidemand-Lichtenberg, and Christian Pedersen

Doc ID: 346680 Received 24 Sep 2018; Accepted 29 Nov 2018; Posted 30 Nov 2018  View: PDF

Abstract: In this paper, a novel method for synchronized imaging upconversion in the mid-IR wavelength range is presented. A versatile 1064 nm MOPA source pump laser is electronically adjusted in pulse duration and repetition rate to match the output from a 40 kHz, 1.6 ns pulses mid-IR supercontinuum light source followed by upconversion to the near-infrared captured by a sensitive CCD camera. The systems noise is characterized and we present a simple algorithm for correcting for the image distortion caused by the use of off axis parabolic mirrors.

A Transmission Line Method for the Simulation of Fiber Bragg Gratings

Nikolaos Stathopoulos, Stylianos Savaidis, Hercules Simos, Evangelos Rigas, Ricardo Correia, Stephen James, and Ralph Tatam

Doc ID: 347614 Received 08 Oct 2018; Accepted 29 Nov 2018; Posted 30 Nov 2018  View: PDF

Abstract: A new method for the analysis and design of fiber Bragg gratings (FBG) based on the theory of transmission lines has been developed and verified both theoretically and experimentally. The method is an extension of the Coupled Mode Theory and utilizes the equivalent transmission lines in order to simulate any type of grating, with an easy and direct implementation. The method provides the ability to analyze the optical devices without using full wave approaches, while also facilitating the incorporation of core materials with a complex or nonlinear refractive index, non-uniform distributions of the grating’s refractive index, and tilted and phase shifted gratings. The approach also allows the design of the grating for a given reflection spectra. Numerical results of the method’s application on a randomly varied inscription of the refractive index of a FBG have also been simulated and discussed. Using this method, the characteristics of an Erbium – Doped FBG have been simulated and the predictions verified experimentally.

Crystal structure dependence of the breathingvibration of individual gold nanodisks inducedby ultrafast laser

Yong Gan and Zheng Sun

Doc ID: 348662 Received 18 Oct 2018; Accepted 29 Nov 2018; Posted 30 Nov 2018  View: PDF

Abstract: The ultrafast laser excited breathing vibrations of gold nanodisks with differentcrystal structures have been studied via the atomistic simulations. The vibrational periods anddamping rates of nanodisks are obtained by the analysis of the simulated transient responsesof nanodisks. It is shown that the breathing period of nanodisks is considerably dependent ontheir crystal structure, which is contrary to the cases for the breathing vibration of metalnanospheres and nanorods. Furthermore, single-crystal nanodisk exhibits much lowerintrinsic damping as compared with polycrystalline nanodisks, for which the additionalenergy dissipation by the grain boundaries in the polycrystalline nanodisks could be onemajor factor.

The Macek and Davis Experiment Revisited: ALarge Ring Laser Interferometer Operating onthe 2s2 􀀀!2p4 Transition of Neon

Caroline Anyi, Robert Thirkettle, Dian Zou, David Follman, Garrett Cole, Ulrich Schreiber, and Jon-Paul Wells

Doc ID: 351282 Received 06 Nov 2018; Accepted 28 Nov 2018; Posted 29 Nov 2018  View: PDF

Abstract: We operate a large helium-neon based ring laser interferometer with single-crystalGaAs/AlGaAs optical coatings on the 2s2 􀀀!2p4 transition of neon at a wavelength of 1.152276m. For either single longitudinal- or phase-locked multi-mode operation, the preferable gascomposition for gyroscopic operation is 0.2 and 0.3 mbar of 50:50 neon with total pressuresbetween 6-12 mbar. The Earth rotation bias is sufficient is to unlock the device, yielding a Sagnacfrequency of approximately 60 Hz.

Miniature Holographic Projector with Cloud Computing Capability

Michal Makowski, Adam Kowalczyk, Marcin Bieda, Jaroslaw Suszek, Izabela Ducin, Tomoyoshi Shimobaba, Yuki Nagahama, and Tomoyoshi Ito

Doc ID: 344700 Received 31 Aug 2018; Accepted 28 Nov 2018; Posted 29 Nov 2018  View: PDF

Abstract: A fully functional miniaturized projection head below 5 cm3 is presented, using computer generated holograms dynamically displayed on a liquid-crystal spatial light modulator. Spatial division of the modulator is used for color projection without color break-up and especially designed, anti-reflection coated prisms ensure simple light paths with small losses. Real time calculations are performed on a remote server with on-the-fly compression of holographic fringes. Cloud computing allows 1 W of local electrical power usage and apparent image brightness equivalent to 15-500 lm/W efficiency, depending on the displayed content. The properties of the projector allow future applications in handheld displays.

Optical characterization and Adaptive Opticscorrection of polymer adaptive lensesaberrations

Martino Quintavalla, Freddie Santiago, stefano bonora, and Sergio Restaino

Doc ID: 345668 Received 19 Sep 2018; Accepted 28 Nov 2018; Posted 29 Nov 2018  View: PDF

Abstract: Adaptive lenses based on fluid-filled polymer membranes allow for greatsimplification of optical systems providing large focal length variation and reduction of size,weight and power consumption. However, aberrations can reduce their optical quality and, forsome demanding applications, their correction by means of adaptive optics implies increasedcomplexity, especially if reflective wavefront correctors are used. In this work, wecharacterize two adaptive lenses in terms of optical power and aberrations. We then correctthe gravity-induced aberrations by means of a multi actuator adaptive lens in a closed-loopadaptive optics configuration, with a minimal increase in the optical setup complexity. Theimprovement in the performance of an imaging system are shown.

Investigation of the thermo stability of aluminium thin film filters with protectiveMoSi2 cap layers

Nikolay Chkhalo, Mikhail Drozdov, Sergey Gusev, Alexey Lopatin, Valery Luchin, Nikolay Salashchenko, Dmitry Tatarsky, Nikolay Tsybin, and Sergey Zuev

Doc ID: 347518 Received 05 Oct 2018; Accepted 27 Nov 2018; Posted 29 Nov 2018  View: PDF

Abstract: Aluminium thin film spectral filters are widely used in telescopes for space observations of theSun in the extreme ultraviolet range of wavelengths. The main purpose of film filters is to blockradiation in the UV, visible, and near-IR spectral range. In connection with the development of newprojects for the observation of the Sun from close distances, the thermal stability of the entrance filmfilter is an important characteristic. In this paper, the thermal stability of Al films with 2.5 nm thick MoSi2protective cap layers has been studied. MoSi2 was chosen as a coating material because MoSi2 capseffectively protect the Al film from oxidation and simultaneously increase the mechanical strength ofthe Al film. Vacuum annealing of MoSi2/Al/MoSi2 films was carried out at temperatures up to 300°C. Ithas been demonstrated that at an annealing temperature of more than 200°C for 24 hours, a noticeabledecrease in the blocking properties of the MoSi2/Al/MoSi2 film is observed in the visible wavelengthrange, which is caused by the appearance of semi-transparent crystalline silicon dendritic structures thatare tens of microns in size in the film. In the annealed area of the film specimen, the intermetallicAl12Mo phase was detected by electron diffraction structure analysis, indicating a possible reason for theappearance of silicon atoms needed for dendrite growth as a result of the chemical interaction of Al andMoSi2. Due to the requirements for a high degree of visible radiation blocking (106 to 107 times), theappearance of even one dendritic structure significantly reduces the blocking properties of the film filterand is, therefore, not permissible. Based on the measurement of the transmission of MoSi2-2.5 nm/Al-72 nm/MoSi2-2.5 nm films at 633 nm for isothermal annealing at 200–250 °C, the activation energy forthe formation of dendritic structures (E=1.55 ± 0.1 eV) was measured and the maximum permissible filmtemperature (130°C) at which dendritic structures did not appear during a 5-year mission was predicted.

Influence of altitude on aero-optic imaging qualitydegradation of the hemispherical optical dome

Hui Wang, Shouqian Chen, HUAJUN DU, Fanyang Dang, lin Ju, YUE MING, RONGDA ZHANG, XIAOTIAN SHI, Jiaqian Yu, and Fan Zhigang

Doc ID: 348480 Received 17 Oct 2018; Accepted 27 Nov 2018; Posted 29 Nov 2018  View: PDF

Abstract: We investigated the influence of altitude on aero-optic imaging quality degradation of the hemispherical opticaldome. The boundary conditions for aerodynamic heating effect of optical dome were calculated by solving theReynolds-averaged Navier-Stokes equations provided by FLUENT. The finite element model and the thermalstructuresimulation results of optical dome were obtained by using ANSYS. The three dimensional non-uniformrefractive index field of optical dome was obtained according to the thermal-optical effect. The optical trackingmethod based on the fourth-order runge-kutta algorithm was adopted to simulate the optical transmissionthrough the optical dome. The Strehl ratio(SR), encircled energy, distorted target images and peak signal-to-noiseratio were presented for imaging quality evaluation. The variation rules of these image quality evaluationparameters were obtained in the altitude range of 0~45Km.The results showed that in the same flight conditions,with the increase of altitude, peak signal-to-noise ratio (PSNR) of the distorted image and SR result were increased;radiuses of dispersion spots including 80% energy was decreased, therefore the influence of aero-optics effect onimage quality degradation was gradually weakened.

Single-shot 3D shape measurement ofdiscontinuous objects based on coaxial fringeprojection system

Zhangying Wang, Zonghua Zhang, Nan Gao, Yanjun Xiao, Feng Gao, and Xiangqian Jiang

Doc ID: 344295 Received 12 Sep 2018; Accepted 27 Nov 2018; Posted 29 Nov 2018  View: PDF

Abstract: Fringe projection profilometry has been widely used in high-speed threedimensional(3D) shape measurement. To improve the speed without loss of accuracy, wepresent a novel single-shot 3D shape measuring system that utilizes a coaxial fringeprojection system and a 2CCD camera. The coaxial projection system comprising of a visiblelight (red, green and blue) projector and an infrared (IR) light projector can simultaneouslyproject red, green, blue and IR fringe patterns. The 2CCD camera, as the name suggests, hastwo CCD chips that can acquire visible and IR fringe patterns at the same time. Combiningthe two-step phase shift, Fourier transform profilometry and the optimum three-frequencyselection method, 3D shape measurement of complex surfaces such as large slopes ordiscontinuous objects can be obtained from single-shot acquisition. A virtual fringe projectionmeasurement system has been established to generate pre-deformed fringe patterns to correctpositional deviations of the coaxial projection system. This method has been applied tosimulations and experiments on static and dynamic objects with promising results.

Low-noise and high-gain of stimulated Brillouinamplification via orbital angular momentum modedivision filtering

Liwen Sheng, Dexin Ba, and Zhiwei Lu

Doc ID: 345233 Received 06 Sep 2018; Accepted 27 Nov 2018; Posted 29 Nov 2018  View: PDF

Abstract: We demonstrate a Brillouin amplifier scheme by using orbital angular momentum (OAM) mode division filtering,which is able to amplify the weak optical signals with low-noise and high-gain. The system retains the advantagesof conventional collinear Brillouin amplifier structure, and employs a liquid-crystal spatial light modulator (SLM)to generate distinguishable degree-of-freedom of beams. As we all know, the noise mainly derives from theunwanted coupling in SBS processes, which severely limits the amplifier’s performances. The efficient SBS noisefilteringmethod is discussed which could improve the output beam quality effectively. The experimental resultsshow the proposed amplifier scheme can overcome this obstacle, providing the magnification (or called signal gain)of 71dB for an input signal of 4.7×10−12J. Besides, the amplified signal is recognized from the ASE-like noise with aSNR of 6.7dB.

Direct measurements of collisional Raman linebroadening in the S-branch transitions of COperturbed by CO, N2, and CO2

Paul Hsu, Hans Stauffer, Naibo Jiang, James Gord, and Sukesh Roy

Doc ID: 349879 Received 01 Nov 2018; Accepted 27 Nov 2018; Posted 29 Nov 2018  View: PDF

Abstract: We report direct measurement of collisional line-broadening coefficientsassociated with rotational Raman transitions of carbon monoxide (CO), obtained using timeresolvedpicosecond rotational coherent anti-Stokes Raman scattering (ps-RCARS)spectroscopy. The dependencies of the CO self-broadening coefficients on rotational quantumnumber, J, and temperature are described for the J = 3–16 lines of S-branch (ΔJ = +2)transitions for T = 295–600 K at atmospheric pressure. Further, we report collisionallinewidths of CO and collision partners N2 and CO2. The obtained S-branch linewidths ofself-broadened CO agree well with previously reported frequency-domain experimentalspectroscopy results, whereas, the mixture-linewidth broadening coefficients differ fromreported theoretical results by up to 80%.

Eccentric fiber Bragg gratings refractometer inscribedby point-by-point IR femtosecond laser

Hicham Chikh-Bled, Debbal Mohammed, Mohemmed El-Kebir Chikh-Bled, mohammed chemss edine, Venancio Calero, and Mouweffeq Bouregaa

Doc ID: 344930 Received 04 Sep 2018; Accepted 26 Nov 2018; Posted 29 Nov 2018  View: PDF

Abstract: In this paper, we demonstrate Point-by-Point (PbP) inscription of Eccentric FBG (EFBG) in conventional singlemodefiber (Corning SMF-28) with second order Bragg resonances within C-band using an IR femtosecond laser.Highly localized fiber Bragg gratings and asymmetric can be inscribed with focused ultrashort pulses. EFBG arelocalized close to the core-cladding interface, yielding strong cladding mode resonance couplings and highphotoinduced birefringence. The inscription conditions to optimize the grating fabrication have been explored toachieve second-order resonances of good spectral quality. Potential applications of EFBG in refractometry sensingare further illustrated. Two interrogation techniques for EFBG in refractometry are reported and experimentallytested.

HIGH EFFICIENCY FLEXIBLE MULTILEVEL PHOTONSIEVES BY SINGLE-STEP LASER-BASEDFABRICATION AND OPTICAL ANALYSIS

Matthew Julian, David Macdonnell, and Mool Gupta

Doc ID: 348526 Received 19 Oct 2018; Accepted 26 Nov 2018; Posted 29 Nov 2018  View: PDF

Abstract: Over the past several decades, the need for high-resolution, high-efficiency,lightweight, high contrast focusing optics has continued to increase due to theirapplications in fields such as astronomy, spectroscopy, free-space opticalcommunications, defense, and remote sensing. In recent years, photon sieve planardiffractive optics, which are essentially Fresnel zone plates with the rings broken intoindividual “pinhole” apertures, have been developed on flexible, lightweight polyimidesubstrates. However, transmission efficiencies have continuously been very low (~1-11%) until this work, thus impeding the widespread use of photon sieves in practicalapplications. Here, we present flexible, lightweight, 4 and 8-level level phase photonsieves with 25.7% and 49.7% transmission efficiency, respectively – up to 5x greaterthan that of any other photon sieve reported thus far. Additionally, these sieves werefabricated via a single step pulsed laser ablation method. The total time to fabricate a ~3cm2 photon sieve via the single-step fabrication was tens of seconds, giving the techniquea significant advantage over traditional photolithography used to generate multilevelstructures. Analytical analysis of the photon sieve was carried out via finite-differencetime domain (FDTD) method, and was in very good agreement with experimentalresults. We have also calculated via FDTD modeling the behavior of higher level photonsieves for further enhanced efficiencies, and analytically show an estimated upper boundon photon sieve efficiency of 70% within the first focal plane null in the limit ofincreasing step number, and the data presented herein provides a relationship betweenefficiency and step number. Additionally, this process of multilevel diffractive lensfabrication can be extended to multilevel Fresnel zone plates, which have not previouslybeen demonstrated by this process. The results presented in this work represent a newstep in high-resolution diffractive optics, showing efficiencies suitable for widespreadapplications in addition to drastically reducing the cost and complexity of fabricatingmultilevel focusing elements.

Feasibility study of digital holography forerosion measurements under extremeenvironmental conditions inside the ITERTokamak

Giancarlo Pedrini, Igor Alexeenko, Mark Kempenaars, Govindarajan Jagannathan, George Vayakis, and Wolfgang Osten

Doc ID: 347031 Received 01 Oct 2018; Accepted 26 Nov 2018; Posted 29 Nov 2018  View: PDF

Abstract: In the International Thermonuclear Experimental Reactor (ITER), underconstruction in southern France, there will be a need for continually measuring the erosion atthe wall, after the machine starts operating. A two wavelength interferometric techniquebased on digital holography is proposed for the erosion measurement. This technique has theability to tackle the challenging environmental conditions within the reactor by a longdistance measurement, where a relay optic will be used for imaging the investigated surfaceon the detector. We will show that shape measurements of objects located at a distance ofmore than 20 m from the measuring head can be carried out in a short time (100 μs) by thetwo wavelength interferometric technique. A depth accuracy of ±10 μm is achieved.

Multidispersed bubble-size measurements byIPI at scattering angles of 90° and 45°

Hongxia Zhang, Xiaolei Wang, Jinlu Sun, Dagong Jia, and T. Liu

Doc ID: 340782 Received 26 Jul 2018; Accepted 26 Nov 2018; Posted 28 Nov 2018  View: PDF

Abstract: Measurements of multidispersed bubble diameter are important in hydraulics,biology, and other such fields. Interferometric particle imaging (IPI) systems are used tomeasure the bubble diameter. In geometric approximation (GOA), the scattering angle cannotbe greater than 2arccosm. We propose a universal method for calculating the bubble diameterat wide scattering angles and use an IPI system to measure the bubble-size distribution at 90°and 45°. The particle size distribution measured at two angles is in consistent with each other.The results of this study indicate that this method is suitable for measuring the bubble-sizedistribution.

A novel auto-correction method for improvingtemperature stability in the long-range Raman fibertemperature sensor

Jian Li, Yan Baoqiang, Mingjiang Zhang, Jianzhong Zhang, Qiao Lijun, and Wang Tao

Doc ID: 348049 Received 12 Oct 2018; Accepted 26 Nov 2018; Posted 28 Nov 2018  View: PDF

Abstract: We propose and experimentally demonstrate a novel auto-correction method for improving temperaturestability in the long-range Raman distributed fiber temperature sensors. The proposed method is based onthe multi-stage constant temperature control and dynamic gain calibration technology, which can suppressthe unstable photoresponsivity and noise of system. The experimental results indicate that the temperaturestability is optimized from ±12.6 °C to ±7.2°C at the sensing distance of 30 km for multimode fiber (MMF)using this method.

Reconstruction of 2D velocity distribution in scramjetby laser absorption spectroscopy tomography

Qianwei Qu, Zhang Cao, Lijun Xu, Chang Liu, Liuyong Chang, and Hugh McCann

Doc ID: 342263 Received 20 Aug 2018; Accepted 25 Nov 2018; Posted 29 Nov 2018  View: PDF

Abstract: We propose a method to reconstruct the two-dimensional (2D) velocity distribution of flow fields by laserabsorption spectroscopy tomography. A mathematic model is established to reveal the dependence of spectralabsorbance on line-of-sight velocity distribution. Then, with multiple laser beams from different angular viewscovering the region of interest, a nonlinear equation set of 2D velocity distribution is established according to themodel. The integrated absorbance coefficient distribution is reconstructed using the Landweber iterationalgorithm and substituted into the nonlinear equation set for further simplification. Finally, the velocitydistribution is reconstructed by solving the simplified equation group via the interior-point algorithm. Theproposed method is validated numerically by reconstructing the velocity distribution of water molecules, ascalculated by Computational Fluid Dynamics, over a cross-section of a double-mode scramjet combustor. Themethod does not require adding extra tracer particles and avoids issues arising from the short lifetime ofmolecular tags. It is suitable for diagnosis of high-speed flow fields.

Laser micromachining of periodic surface radiuschange on the optical fiber circumference.

Luc Levesque and Robert Gauthier

Doc ID: 347918 Received 10 Oct 2018; Accepted 25 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: In this report we are showing that holes and markings spots with sizes that are comparable to the wavelength of aCO2 laser at λ = 10.6 μm can be achieved reproducibly on a conventional optical fiber SMF28 when it is positionedat the focal point. Some theory on the Gaussian beam propagation is briefly reviewed and readily applied to drill afiber on its axis near the focal point. As the fiber is moved from the focal point, it was found that some features suchas ridges along the fiber circumference were also micromachined by laser. It was demonstrated that thefabrication of surface nanoaxial photonic fibers, long pitch grating fibers and pump laser strippers can beenvisaged on conventional SMF28 with a cladding diameter of 125μm.

Plasmonic-induced absorption based on anend coupled combined resonance system ofsemi-annular cavity and rectangular cavity

Yihong Fang, Kun-Hua Wen, Li Chen, Zhengfeng Li, and Bingye Wu

Doc ID: 349395 Received 02 Nov 2018; Accepted 25 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: A semi-annular-rectangular composite cavity (SARCC) structure based on metalinsulator-metal (MIM) waveguides is proposed. By adding a rectangular cavity at a suitableposition around the semi-annular cavity (SAC), single analogous plasmonic-inducedabsorption (PIA) effect is achieved at the expected mode of the SAC structure. After addingtwo rectangular cavities together in the SAC system, dual analogous PIA effects for bothmodes can be realized simultaneously. In addition, the phase response is also studied, andabnormal dispersions are achieved in the PIA windows, which can be used in the integratedoptics for fast/slow light. The performances of the proposed 2-dimensional structure areanalyzed and studied by the coupled mode theory (CMT) and the finite-difference timedomain(FDTD) method, respectively.

Object wave retrieval using normalized holograms inthree-step generalized phase-shifting digitalholography

Nobukazu Yoshikawa, SYOUMA NAMIKI, and Atsushi Uoya

Doc ID: 345850 Received 14 Sep 2018; Accepted 25 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: Phase-shifting method using interferogram normalization is often applied to smooth objects, for which therequirements for the normalization approach, including zero-order term elimination and the normapproximation condition, are easily achieved. Here, we propose a three-step generalized phase-shiftingmethod using the normalization approach for diffuse objects. In the proposed method, the zero-order termsare sufficiently suppressed by mutual subtraction of the phase-shifted holograms. The norm approximationcondition is satisfied and the complex field of the object wave can be estimated by the normalization approachwhen the hologram satisfies the phase randomness condition. We present an object wave retrieval algorithmusing three phase-shifted holograms, in which estimation of phase shift values is unnecessary. The proposedmethod is verified through simulations and optical experiments.

Coherence control of entanglement dynamics oftwo-mode Gaussian state via Raman drivenquantum beat laser using Simon’s criterion

Shakir Ullah, Haleema Qureshi, Gul Tiaz, Fazal Ghafoor, and Farhan Saif

Doc ID: 346485 Received 24 Sep 2018; Accepted 24 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: We study the entanglement dynamics of two-mode Gaussian state (TMGS) in aquantum beat laser driven by two classical fields in Raman configuration using Simon’s criterionof quantum state separability. The two modes of the cavity field is considered initially in generalsingle-mode Gaussian states. The effect of the non-classicality, purity and relative phase ofthe cavity modes on the entanglement phenomenon is studied thoroughly. We show that inpresence of cavity decay rates, the higher the non-classicality of the initial states, the higher isthe inseparability of the evolved TMGS of the cavity field. The inseparability, on the other side,is independent of the purity of the initial states. Moreover, the time scale of the entangled stateincreases with the relative intensity of the driving fields whereas the relative phase switches theentangled state into disentangled state of the cavity field and vice versa. The quantum statisticsof the mean photons number of the cavity field is analyzed.

Total internal reflection shell for LED bulbs

Hiroshi Ohno and Mitsuaki Kato

Doc ID: 348523 Received 16 Oct 2018; Accepted 23 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: A total internal reflection (TIR) shell capable of generating illuminating light with a wide-angle distribution from light-emitting diodes (LEDs) is proposed. The TIR shell can be used to create a LED light bulb with enclosed heat dissipaters to release the heat generated by the LEDs. The TIR shell has light-scattering areas on its inner surface and a mirror-polished free-form outer surface that can guide all rays emitted from the LEDs to the scattering areas by the total internal reflection. The rays diffused by the light-scattering areas are emitted from the TIR shell in a wide-angle light distribution. A prototype of the LED light bulb with a metal shell for heat dissipation inside the TIR shell shows favorable features such as a half-intensity angle of 330 degrees, lighting efficiency of 81 %, and glare-free lighting emitted from the entire surface area of the TIR shell.

A 9-sector three-stage Fresnel lens concentrator

Yong-Da Chen, Sheng-han Tu, Hwen-Fen Hong, Chun-Yi Chen, and Jui Wen Pan

Doc ID: 345740 Received 12 Sep 2018; Accepted 23 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: In this paper, we design a three-stage Fresnel lens concentrator with a low f number. The proposed concentratorconsists of a primary optical element (POE) and a second optical element (SOE). The 9-sector three-stage Fresnellens is composed of three types of triangular prisms: the refractive triangular prism, the single total internalreflection (STIR) triangular prism, and the double total internal reflection (DTIR) triangular prism. In order toincrease the uniformity and the acceptance angle of the POE coupled to with the SOE, the SOE is also divided into 9sectors. Finally, it is found that this 9-sector three-stage Fresnel lens concentrator can achieve a concentration ratioof 1000X, the uniformity is 25.8, the optical efficiency is 81.8%, the f number is 0.46 and the acceptance angle is ±0.73°.

Rotation double prisms steered by noncircular gearpairs to scan specified nonlinear trajectories

Anhu Li, Yang Zhang, Xingsheng Liu, and Wanli Yi

Doc ID: 341291 Received 31 Jul 2018; Accepted 23 Nov 2018; Posted 28 Nov 2018  View: PDF

Abstract: In order to scan some specified nonlinear motion trajectories with high accuracy, simple control process and goodstability, we propose a method to design the drive mechanism of the rotation double-prism scanner, which cantransfer the nonlinear motor control to the profile design of corresponding noncircular gear pairs. Given anonlinear target trajectory, this method can successfully change the complicated nonlinear motion of the motor tothe more operative uniform rotation. The simulation and experiment results show that the tracking error is lessthan 0.981 mm in the distance of 500 mm between the actual tracking trajectory and the original one. Theproposed drive mechanical setup offers a perfect alternative to the nonlinear control design of rotation doubleprismscanner.

CIOMP-Study on low order aberrations measurements oflarge aperture flats based on scanning pentaprism

Er Qi, Haixiang Hu, and Xiao Luo

Doc ID: 336087 Received 03 Jul 2018; Accepted 23 Nov 2018; Posted 30 Nov 2018  View: PDF

Abstract: The PPS (pentaprism scanning technology) is an absolute testing method which has advantages of simple structure,absolute testing without extra reference flat, providing in-situ surface measurement, etc. It plays an important rolein the manufacturing process of large flat mirrors. For calibrating the PPS’s uncertainty, this paper developed amulti-mode scanning method to implement the measurement of low order aberrations and introduced a concept ofautocorrelation coefficient to evaluate the data processing progress. These improvements were applied to themeasurement of a large flat mirror (1630mm in diameter), which demonstrates the measuring uncertainty of PPScan be about 20nm rms. Furthermore, aimed at the special requirement of M3MP, which is the prototype mirror ofM3M (the tertiary mirror) in TMT (Thirty Meter Telescope) project and has an un-circular aperture, this paperanalyzed the slope distribution of low order aberrations, power and astigmatism. Then the sample route lines ofPPS are reorganized and new data process algorism is implemented. All these work were done to improve PPS’sperformance on measuring low order aberrations of large flat mirrors.

Volumetric analysis of breast cancer tissuesusing machine learning and swept-sourceoptical coherence tomography

Ankit Butola, Azeem Ahmad, Vishesh Kumar Dubey, Vishal Srivastava, DRAKSHAM QAISER, ANURAG SRIVASTAVA, Paramasivam Senthilkumaran, and Dalip Mehta

Doc ID: 345099 Received 05 Sep 2018; Accepted 22 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: In breast cancer, 20 - 30% cases require a second surgery because of incompleteexcision of malignant tissues. Therefore, to avoid the risk of recurrence, accurate detection ofthe cancer margin by the clinician or surgeons need some assistance. In this paper, anautomated volumetric analysis of normal and breast cancer tissue is done by machine learningalgorithm to separate them into two classes. The proposed method is based on support vectormachine (SVM) based classifier by dissociating ten features extracted from A-line, textureand phase map by the swept source optical coherence tomographic (SS-OCT) intensity andphase images. A set of 88 freshly excised breast tissue (44 normal and 44 cancers (Invasiveductal carcinoma tissues)) samples from 22 patients were used in our study. The algorithmsuccessfully classifies the cancerous tissue with sensitivity, specificity and accuracy of91.56%, 93.86%, and 92.71% respectively. The present computational technique is fast,simple, sensitive and extracting features from whole volume of the tissue which doesn'trequire any special tissue preparation and an expert to analyze the breast cancer as required inhistopathology. Diagnosis of breast cancer by extracting quantitative features from the OCTimages could be a potentially powerful method for cancer detection and would be a valuabletool for fine needle guided biopsy.

Tunable defect modes of one-dimensionalphotonic crystals containing a Diracsemimetal based metamaterial defect layer

Qin WANG, Xinliang Wang, liwei Zhang, Yongqiang Wang, Wentao Qiao, Xu Han, Xiaolin Cai, and Weiyang Yu

Doc ID: 345432 Received 11 Sep 2018; Accepted 22 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: The transmission properties of one-dimensional photonic crystals containing ametamaterial defect layer are investigated using the transfer matrix method. The metamaterialis composed of alternating layers of a dielectric material and a Dirac semimetal material.Numerical results show that the defective photonic crystals possess tunable defect mode,which is significantly dependent on the Fermi level of the Dirac semimetal as well as thestructural parameters of the metamaterial defect layer. The defect mode properties underdifferent incident angles for TE and TM polarizations are also studied. Such defectivestructures have potential applications in tunable filters and sensors in terahertz regions.

Magneto-optical imaging feature extraction ofmicro-gap weld joint under nonuniformmagnetic field excitation

Xiangdong Gao, Yanfeng Li, Tingyan Chen, PERRY P Gao, and Yanxi Zhang

Doc ID: 332622 Received 28 Jun 2018; Accepted 21 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: To reduce the effect of the nonuniformity of magnetic field excitation on microgapweld joint magneto-optical (MO) imaging, a new experimental system based on theFaraday MO effect to detect micro-gap welds (gap width less than 0.1 mm) under nonuniformmagnetic field excitation was developed. Horseshoe permanent magnets were used tomagnetize the weldment and establish a nonuniform magnetic field at the welding joint. MOimages of the micro-gap weld joint were captured using an MO sensor under nonuniformmagnetic field excitation. After analyzing the distribution characteristics of the magneticinduction intensity in the weld joint area, a characterization method for the weld zone slopewas proposed. The weld zone slope could accurately determine the MO imaging effects underthe nonuniform magnetic field. A model based on error back propagation (BP) neural networkwas used to predict the offset of the weld joint center at each moment, and the resultsperformed by BP were utilized to optimize the measured value of the weld joint center.Experimental results show that it can accurately extract the position of micro-gap welds undernonuniform magnetic field excitation.

Detection of material zones on the surface of asteel-aluminium hybrid component using reflectionmodels and a monochromatic fringe projectionprofilometry system

Lorenz Quentin, Rüdiger Beermann, Markus Kaestner, and Eduard Reithmeier

Doc ID: 347051 Received 28 Sep 2018; Accepted 21 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: The limits of traditional lightweight engineering are being extended by the development of hybrid components.Lightweight potential is especially high when using dissimilar materials, e.g. a friction-weldedsteel-aluminium combination. An important factor for the mechanical properties of such a combinationis the geometry and location of the joining zone between the materials. The geometry of these objectscan be reconstructed by optical triangulation techniques like fringe projection profilometry. In this paper,we present a method to robustly detect the different material zones on the surface of an hybridsteel-aluminium component. We use reflection models and the data from a fringe projection profilometrysystem. The intensity values and the 3D geometry data from the fringe projection system are usedto estimate material-specific reflection parameters for each 3D point and detect different material areasbased on a global theshold.

High-resolution Light-Field Imagingvia Phase Space Retrieval

Chien-Hung Lu, Stefan Muenzel, and Jason Fleischer

Doc ID: 347162 Received 08 Oct 2018; Accepted 21 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: By combining a high-resolution image from a standard camera with a low-resolution light-field image from a lenslet array, we numerically reconstruct a high-resolution light-field image. We experimentally demonstrate the method by creating a high-definition 3D image of a human cheek cell with a commercially available microscope.

Exo-atmospheric infrared objects classification usingRecurrence Plots based Convolutional NeuralNetworks

Qiuqun Deng, Huanzhang Lu, Moufa HU, and Bendong Zhao

Doc ID: 344358 Received 11 Sep 2018; Accepted 21 Nov 2018; Posted 21 Nov 2018  View: PDF

Abstract: Object discrimination plays an important role in infrared (IR) imaging system. However, at long observingdistance, the presence of detector noise and absence of robust features make exo-atmospheric objectsclassification difficult to tackle with. In this paper, a Recurrence Plots based Convolutional Neural Network (RPCNN)is proposed for feature learning and classification. Firstly, it uses Recurrence Plots (RP) to transform timesequences of IR radiation into 2-dimension texture images. Then, a CNN model is adopted for classification.Different from previous objects classification methods, RP representation has well-defined visual texture patternsand their graphical nature exposes hidden patterns and structural changes in time sequences of IR signatures. Inaddition, it can process IR signatures of objects without the limitation of fixed length. Training data are generatedfrom IR irradiation models considering micro-motion dynamics and geometrical shape of exo-atmospheric objects.Results based on time-evolving IR radiation data indicate that our method achieves a significant improvement inaccuracy and robustness of the exo-atmospheric IR objects classification.

3D displacement measurement of self-oscillating gelusing digital holographic microscopy

Yoshiyuki Morita, Tsukasa Matsuo, Shingo Maeda, Masamichi Oishi, and Marie Oshima

Doc ID: 345813 Received 17 Sep 2018; Accepted 21 Nov 2018; Posted 21 Nov 2018  View: PDF

Abstract: To measure the 3D micro-displacement of a self-oscillating polymer gel driven by the Belousov-Zhabotinsky (BZ)reaction, we propose a new particle detection and tracking method based on a phase image/volume templatematching using digital holographic microscopy (DHM). We demonstrate the precision of the proposed method andcompare it with conventional approaches. The method is applied to 3D measurement of the motions of particlesattached to the surface of an oscillating gel. Measurement results show that the local area of the gel oscillatesperiodically, and the motion propagates throughout the gel. Our method can measure rapid and complex 3D microdisplacementchange.

Research on Adaptive Filter for Mie Lidar Return

Yuehui Song, Yudong Zhou, Pengbo Liu, Gaodong Shi, yufeng wang, di huige, and hua Dengxin

Doc ID: 347697 Received 08 Oct 2018; Accepted 21 Nov 2018; Posted 21 Nov 2018  View: PDF

Abstract: The statistical properties of the noise in the Mie lidar return is analyzed by statistical hypotheses testing method. Based on this, an adaptive filter is proposed to eliminate the noise. The LMSE algorithm is used to achieve optimal filtering, in which the MSE is minimized by adjusting the filter's weight matrix. The validity of the adaptive filter is verified by numerical simulation and experimental data retrieving. In numerical simulation, the SNR of the output of the adaptive filter is larger than that of the wavelet transform filter, and the MSE of the output of the adaptive filter is less than that of the wavelet transform filter. In experimental data retrieving, the filtered lidar return of adaptive filter and wavelet transform filter is used to retrieve extinction coefficient respectively. The amplitude of the ripples in extinction coefficient profile of adaptive filter is less than that of wavelet transform filter. The profile of adaptive filter is smoother than that of wavelet transform filter. The detail of extinction coefficient is displayed more clearly in the profile of the adaptive filter. The research result is of great importance for improving accuracy of lidar data retrieving.

Optical axis maladjustment sensitivity in atriangular ring resonator

Shaoman Song, Chnuhui Hu, and Changxiang Yan

Doc ID: 348056 Received 15 Oct 2018; Accepted 21 Nov 2018; Posted 21 Nov 2018  View: PDF

Abstract: This paper estimates and measures the influences of mismatch and misalignmenton continuous-wave cavity ring-down spectroscopy (CW-CRDS). We describe the theoreticaldifferences in maladjustment effects on power transfer under different resonant cavityconfigurations and present a method for reducing the impact of maladjustment. Finally, wedemonstrate a method for measuring the effect of maladjustment on power transfer when aGaussian beam is matched to a triangular ring resonator.

In-line integration of offset MMF-Capillary-MMF structure as a portable and compactFiber-optic SERS microfluidic chip

Shiyu Li, Li Xia, Houjin Zhang, Wei Li, Ke Li, and Xin Chen

Doc ID: 345737 Received 12 Sep 2018; Accepted 21 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: A novel Fiber-optic SERS microfluidic chip integrated with an embedded Ramanprobe is presented and demonstrated. The Raman probe consists of the offset multimode fiber(MMF)-Capillary-MMF (OMCM) structure and surface-enhanced Raman scattering (SERS)substrate. The probe is embedded in the microfluidic channel to form a compact and portablechip. The chip is employed with a fiber coupler in an all-fiber detection system which has agood stability compared to the free space focusing by the conventional confocal Ramanmicroscope. The excitation lights transmit from both ends of the OMCM probe into thecapillary, and the generated Raman scattered signals are collected by two MMFssimultaneously. Experimental results of the Rhodamine 6G (R6G) detection show that theRaman signal intensity increases in a linear pattern at ~1509 cm-1 with the increase of R6Gconcentrations. This kind of chip has the features of compact, integrated, and miniaturized forthe Raman signal detection. Furthermore, it can be fabricated easily in large quantities at cost,which renders promising applications.

All-fiber polarization division multiplexing tomode division multiplexing conversion forhybrid optical networks

lipeng feng, Yan Li, Hang Zhou, Sihan Wu, CHEN YANG, Wei Li, Jifang Qiu, Hongxiang Guo, Xiaobin Hong, and Jian Wu

Doc ID: 348916 Received 22 Oct 2018; Accepted 21 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: This paper proposes and experimentally demonstrates an all-fiber conversionmethod that transfer the polarization division multiplexing (PDM) signals to the modedivision multiplexing (MDM) signals. The conversion scheme is based on a mode convertor(MC) and a polarization-mode controller (PMC). The input X-polarized/Y-polarizedfundamental modes are converted to the first order linear-polarized LP11A/LP11B modes withthe crosstalks of -10dB/-18dB and the insertion losses of 3.04dB/3.1dB at 1550 nm,respectively. Using the proposed convertor, 11.2 GBaud/s polarization-division-multiplexedquadrature-phase-shift-keying (PDM-QPSK) and 16 quadrature-amplitude-modulation(PDM-16QAM) signals are successfully converted to 11.2 GBaud/s MDM-QPSK and MDM-16QAM signals.

Microstructured light guiding plate for single-sidedlight emission as light source for room illumination

Michael Jakubowsky, Carolin Hubschneider, Andreas Neyer, Yuan Fang, and Jan de Boer

Doc ID: 348072 Received 12 Oct 2018; Accepted 20 Nov 2018; Posted 21 Nov 2018  View: PDF

Abstract: Microstructured light guiding plates (LGP) open up new capabilities in the design of energy efficient and flexiblelight sources for room lighting. One desirable application is the illumination of office rooms by LGPs located mainlyat the façade. Starting with the requirements of an ideal light distribution curve for uniform room lighting, suitableoptical microstructures have been designed and investigated by numerical ray tracing methods to be integrated infaçade elements. The maximum of the desired light distribution curve for the test case is at an angle of 96° withrespect to the vertical direction. The designed micro system meets this requirement very well at an angle of 98°and a light cone width of 25°. The light emission of the proposed LGP is highly efficient with 80% couplingefficiency.

Chromatic aberrations of plane-symmetric optical systems

Yiqing Cao, Lijun Lu, and Zhiyong Deng

Doc ID: 345115 Received 06 Sep 2018; Accepted 20 Nov 2018; Posted 20 Nov 2018  View: PDF

Abstract: This paper presents a calculation method of chromatic aberration of such kinds of optical systems based on the aberration theory of plane-symmetric optical systems; and the analytic expressions of the axial chromatic aberration and chromatic change in the magnification at an image plane of any position are derived. The resultant expressions are used to calculate the chromatic aberration of two single lens optical systems with a large incidence angle; and the calculation results are compared to the ones obtained from ray-tracing program to validate the chromatic aberration expressions. The study shows that the calculation accuracy of the chromatic aberration expressions is satisfactory. The analytical analysis of chromatic aberration is helpful in the imaging analysis of plane-symmetric optical systems.

A Simple Derivative-Free Method of Zero Extraction by Phase-based Enclosure for Determination of Complex Propagation Constants in Planar Multilayer Waveguides

Elias Glytsis and Emmanuel Anemogiannis

Doc ID: 346116 Received 17 Sep 2018; Accepted 20 Nov 2018; Posted 20 Nov 2018  View: PDF

Abstract: A rigorous and simple to implement numerical method for extracting the propagation constants and modal characteristics of lossless, lossy, and active planar multilayer waveguides, is presented. The method can accurately determine the complex propagation constants of both guided and leaky modes. The method does not utilize the derivative of the dispersion function nor any integrals of it. It is based on finding the estimates of the zeros of the dispersion function by a systematic successively-tighter enclosure of the zeros with exclusive use of only the phase of the dispersion function along varying rectangular contours in the complex plane. The zero estimates are then refined by the Muller's iterative scheme with deflation.The method was named derivative-free zero-extraction by phased-based enclosure (DFZEPE) for brevity. The DFZEPE method has been applied to lossless, lossy, active, and antiresonant reflecting optical waveguides published in the literature and analyzed with similar methods, and the results are excellent. The proposed DFZEPE method has global convergence and can be applied to a plethora of electromagnetic (and not only) problems that the zeros of an analytic function are sought.

Color holographic display using single chip LCOS

Han Zhe, Boxia Yan, Yan Qo, Yanwei Wang, and Yu Wang

Doc ID: 347196 Received 01 Oct 2018; Accepted 20 Nov 2018; Posted 20 Nov 2018  View: PDF

Abstract: An algorithm of calculating phase only computer-generated hologram (CGH) for3D color display using single chip LCOS is proposed. As an evolution of G-S iteration, theproposed algorithm was obtained by replacing the Fresnel diffraction of single wavelength inG-S algorithm with a color Fresnel diffraction process. Moreover, combined with “Ping-Pong”iteration this algorithm was used to calculate 3D color hologram. Finally, the hologram that iscapable to project color 3D image was generated. Numerical simulation was operated and anoptical reconstruction system based on single spatial light modulation (SLM) was built toprove this method. Both numerical and optical reconstruction result indicated that theproposed method realized 3D color holographic display using single chip LCOS.

Low coherence quantitative phase microscopywith machine learning model and Ramanspectroscopy for the study of breast cancercells and their classification

Vishesh Kumar Dubey, Azeem Ahmad, Ankit Butola, DRAKSHAM QAISER, ANURAG SRIVASTAVA, and Dalip Mehta

Doc ID: 345558 Received 10 Sep 2018; Accepted 19 Nov 2018; Posted 20 Nov 2018  View: PDF

Abstract: Early stage detection of breast cancer is the primary requirement in modernhealthcare as it is the most common cancer among women worldwide. Histopathology is themost widely preferred method for the diagnosis of breast cancer but it requires longprocessing time and involves qualitative assessment of cancer by a trained person/doctor.Here, we present an alternate technique based on white light interference microscopy(WLIM) and Raman spectroscopy, which has the capability to differentiate cancerous breasttissues from the normal one. WLIM provides the quantitative phase information about thebiological tissues/cells, whereas, Raman spectroscopy can detect the changes in theirmolecular structure and chemical composition during cancer growth. Further, both thetechniques can be implemented very fast without staining the sample. The present techniqueis employed to perform ex-vivo study on total 80 normal and cancerous tissue samplescollected from 16 different patients. A generalized machine learning model is developed forthe classification of normal and cancerous tissues, which is based on texture features obtainedfrom phase maps with an accuracy of 90.6%. The correlation of outcomes from these twotechniques can open a new avenue for fast and accurate detection of cancer without anytrained personnel.

Orthographic projection image-based Full-color holographic display with Directional-view image scaling (DIS) for RGB channel

Yan-Ling Piao, Munkh-Uchral Erdenebat, Ki-Chul Kwon, Sangkeun Gil, and Nam Kim

Doc ID: 346081 Received 17 Sep 2018; Accepted 19 Nov 2018; Posted 20 Nov 2018  View: PDF

Abstract: In this research, a directional-view image scaling (DIS) method is proposed to enhance the reconstruction quality for an orthographic projection image-based full-color holographic display system. The camera acquires integral images from real scene through the lens-array, then each orthographic projection image is synthetic to computer-generated hologram. In order to solve the chromatic dispersion problem, each directional view image is scaled depends on the relation between different wavelength and resolution of hologram. The proposed method is simple but effective way to producing the full-color computer-generated hologram using orthographic projection images. The feasibility of the DIS method is confirmed by experimental results.

Occlusion-Robust Sensing Method to Interact with a 3D Image by Using the Light-Field of a 3D Display System

Masahiko Yasui, Yoshihiro Watanabe, and Masatoshi Ishikawa

Doc ID: 345474 Received 17 Sep 2018; Accepted 19 Nov 2018; Posted 27 Nov 2018  View: PDF

Abstract: The recent developments in 3D display technology are remarkable. Owing to such developments, the importance of methods for interacting with 3D images has been increasing. In particular, the ability to perform input operations by directly touching displayed images is important. Therefore, a sensing method is required for recognizing the 3D positions of fingers and determining whether the fingers are touching the 3D image displayed. Conventionally, such a sensing method generally involves position sensing of fingers through image-based active sensing. However, this does not solve the following two problems: (1) the problem of positional registration, that is, the accurate matching between the displayed image and input location, and (2) the problem of occlusion robustness, that is, the achievement of successful sensing even with the presence of an occluding object between the sensor and hands to allow free movement of the hands. Our proposed method solves these problems through the following two ideas. First, we used a method called aerial imaging by retro-reflection, which focuses light rays from a wider range than other 3D display systems. Second, for capturing the reflected light as well as projecting to the sensing target in active sensing, we used the light-field formed by the 3D display system. We also propose a method for obtaining rotation information, considering that the light-field formed by the reflected light changes based on the angle of the sensing target. Simulations and experiments were performed to evaluate the proposed system, and the system setup was optimized through simulations. In the first two experiments conducted on position and rotation sensing, we evaluated the sensing errors due to occlusion and found them to be less than 1.74 mm and less than 15.4 deg, respectively. In the third experiment, we constructed an interaction system with 3D images by using the proposed method, and evaluated this system.

Alignment mark optimization for improving Signalto-Noise Ratio of wafer alignment signal

Juyou Du, Fengzhao Dai, and Xiangzhao Wang

Doc ID: 346734 Received 25 Sep 2018; Accepted 19 Nov 2018; Posted 19 Nov 2018  View: PDF

Abstract: Phase diffraction grating is widely used as alignment mark in wafer alignment system. A higher alignment accuracycan be obtained by using higher diffraction orders of the alignment mark. Meanwhile, the alignment accuracy isalso affected by the Signal-to-Noise Ratio (SNR) of the alignment signal. The diffraction efficiency of the alignmentmark is significantly reduced in practical lithography process, because of the strong absorption of the opaque filmstacks on the mark surface, especially the metal layer. The reduction of the diffraction efficiency leads to adeterioration of the SNR of the alignment signal. Equal sub-segmented phase grating is usually used to improve thediffraction efficiency of higher odd orders, so as to improve the SNR of the corresponding alignment signal.However, there is still a relatively high diffraction efficiency of zeroth and even orders of such grating. They willaffect the SNR of the alignment signal of odd diffraction orders which are usually used to measure mark position. Inthis paper, we propose a method to improve the diffraction efficiency of odd orders for sub-segmented phasegrating through optimizing the structure of alignment mark. Moreover, the diffraction efficiency of zeroth and evenorders, which are not used in the measurement process of mark position, are sufficiently reduced. Simulationresults indicate that the SNR of the alignment signal was improved obviously by the proposed method, which isvery helpful for improving alignment accuracy.

Graphene surface plasmon off-axis superlens basedon tilted one dimensional Si/SiO2 gratings

mengjia lu, yueke wang, zhifei yao, and Chunyang Zhang

Doc ID: 342515 Received 15 Aug 2018; Accepted 18 Nov 2018; Posted 19 Nov 2018  View: PDF

Abstract: Graphene surface plasmon(GSP) superlens, induced from the negative refraction, have recently beendemonstrated in various two-dimensional photonic crystal systems. However, in-plane GSP superlens have neverbeen reported in one-dimensional(1D) photonic crystal system. Here, we propose a Graphene-Si/SiO2 system, bytransferring a graphene sheet on the tilted 1D subwavelength silicon/silica gratings. By discussing the dispersionrelations of the in-plane GSP in this system, the GSP negative refraction is found in mid-infrared region. When tiltedangle, working wavelength and Fermi level are set to be 60º, 11.22μm and 0.2eV, respectively, the off-axissubwavelength focusing have the best resolution, and the full width half maximum(FWHM) of the image is0.0091λ(102.1nm). Further, we investigate the effects of Fermi level on superlens frequency range and FWHM ofthe image, the broadband and deep subwavelength superlens are achieved. The full wave numerical simulationsare conducted by finite element method. Our findings can be applied to the manipulation of in-plane GSPpropagation and biological imaging.

Controllable switch of the transmittance signalvia the polarization combination manipulation

Boquan Ren, Xiang'an Yan, Baorui Duan, Huanqin Gao, Zhou Guo, and Liu Hanchen

Doc ID: 348118 Received 12 Oct 2018; Accepted 18 Nov 2018; Posted 21 Nov 2018  View: PDF

Abstract: We propose and experimentally demonstrate a process in which we can control thebehavior of an atomic medium to switch on or off the transmittance signals at multiplefrequencies in ladder-type electromagnetically induced transparency (EIT) of 5S1/2-5P3/2-5D3/2transition of 87Rb atoms. By adjusting the polarizations of the applied optical fields, theamplitudes of the transmittance spectra at multiple frequency channels can be controlled. Thismechanism originates from the competition between EIT subsystems and the single photonabsorption with a contribution from different transition strengths. Moreover, we also analyzethe influences of the intensity and detuning of the coupling field on the transmitted signalswhen two lasers are perpendicular, linearly polarized lights, and observe electromagneticallyinduced absorption (EIA) due to the quantum constructive interference. Detailed theoreticalanalyses including the different strengths in different transitions and Doppler-broadeningagree with the experimental observations.

Experiments on laser cleaning of sooted opticalwindows

Takuma Endo, Kazuki Okada, Yuto Ito, Wookyung Kim, TOMOYUKI JOHZAKI, and Shinichi Namba

Doc ID: 344975 Received 04 Sep 2018; Accepted 17 Nov 2018; Posted 19 Nov 2018  View: PDF

Abstract: For developing laser-ignition technology, transparent glass plates were artificially sooted, and they were irradiatedrepetitively by laser from the front (sooted) side and the back side separately. Generally, the back-side irradiationwas more effective in the soot removal. However, the cleaning effect was saturated after thousands of laser shots.Although the saturated soot quantity was a decreasing function of the laser fluence per pulse, its magnituderemained the same for both the front-side and the back-side irradiations. By examining several soot-removalmechanisms proposed so far, it was found that the aerodynamic force produced by the flow induced by the laserheatingof the soot was the most plausible one.

Polarization sensitive femtosecond mid-infraredspectrometer with tunable Fabry-Perot filter andchirped-pulse upconversion

Ryosuke Nakamura, Yoshizumi Inagaki, and Tomosumi Kamimura

Doc ID: 345030 Received 05 Sep 2018; Accepted 16 Nov 2018; Posted 19 Nov 2018  View: PDF

Abstract: Femtosecond time-resolved mid-infrared (MIR) spectroscopy based on chirped-pulse upconversion is a promisingmethod for observing molecular structure and vibrational dynamics. We have developed a femtosecond MIRspectrometer that is more sensitive to molecular structure by using a polarized narrowband pump pulse whosecenter frequency is rapidly scanned with an electrically tunable Fabry-Perot filter. The pump energy andpolarization dependences of transient MIR absorption spectra measured with the spectroscopic system revealedthe appearance of a dark (IR-inactive) mode due to a slight decrease in the molecular symmetry of a metal carbonylcomplex, Mn2(CO)10, in solution. In addition, the rotational relaxation time of Mn2(CO)10 in solution was determinedas about 20 ps.

Measuring spatial coherence by using a lateralshearing interferometry

Luping Pan, Xingbing Chao, Zhi-Cheng Ren, Hui-Tian Wang, and Jianping Ding

Doc ID: 349010 Received 22 Oct 2018; Accepted 16 Nov 2018; Posted 19 Nov 2018  View: PDF

Abstract: A modified lateral shearing interferometry is proposed to measure the spatial coherence of partially coherent lightbeams. This interferometry based on a 4-f system consists of a diffraction grating and a spatial light modulator(SLM). In this system, the diffraction grating splits the partially coherent wave into two copied waves, forming ashearing interferogram on the observation plane. The period of composite blazing grating generated by phasemodulatedSLM is flexibly tuned for controlling the lateral displacement of the two copied waves. The complex degreeof spatial coherence of the partially coherent field is obtained through measurements and Fourier analysis ofthe fringe pattern.

Characteristic and improvement on thereconstructed quality of effective perspectiveimages’ segmentation and mosaicking basedholographic stereogram

Xingpeng Yan, Yibei Chen, Jian Su, Teng Zhang, Zhuo Chen, Song Chen, and Xiaoyu Jiang

Doc ID: 344792 Received 03 Sep 2018; Accepted 16 Nov 2018; Posted 19 Nov 2018  View: PDF

Abstract: Based on the effective perspective images’ segmentation and mosaicking (EPISM)printing method, the influence of the holographic element (hogel) size on the reconstructedquality is analyzed to improve the reconstructed quality of holographic stereogram. Theflipping effect and diffraction effect in spatial domain are also discussed, and the opticaltransfer function (OTF) of the holographic stereogram is used in spectrum domain to evaluatethe reconstructed quality. Theoretical analysis and optical experimental results show that thehogel size plays an important role on the flipping effect as well as the clarity of thereconstrued 3D perspective images of EPISM based holographic stereogram, and the flippingeffect can be improved significantly with optimized hogel size.

Robust 3D Surface Recovery by Applying a FocusCriterion in White Light Scanning InterferenceMicroscopy

Hernando Altamar-Mercado, Alberto Patiño-Vanegas, and Andres Marrugo

Doc ID: 346098 Received 19 Sep 2018; Accepted 16 Nov 2018; Posted 16 Nov 2018  View: PDF

Abstract: White Light Scanning Interference (WLSI) microscopes provide an accurate surface topography of engineeredsurfaces. However, the measurement accuracy is substantially reduced in surfaces with low reflectivityregions or high roughness, like a surface affected by corrosion. An alternative technique calledShape from Focus (SFF) takes advantage of the surface texture to recover the 3D surface by using a focusmetric through a vertical scan. In this work, we propose a technique called SFF-WLSI, which consists inrecovering the 3D surface of an object by applying the Tennegrad Variance (TENV) focus metric to WLSIimages. Extensive simulation results show that the proposed technique yields accurate measurements underdifferent surface roughness and surface reflectivity outperforming the conventional WLSI and the SFFtechniques. We validated the simulation results on two real objects with a Mirau-type microscope. Thefirst, a flat lapping specimen with Ra = 0.05 mm for which we measured an average value of Ra = 0.055 mmand standard deviation s = 0.008 mm. The second, a metallic sphere with corrosion which we reconstructedwith WLSI versus the proposed SFF-WLSI technique producing a better 3D reconstruction withless undefined depth values.

Large-Coverage Underwater Visible LightCommunication System Based On Blue-LED EmployingEqual Gain Combining with Integrated PIN arrayReception

jiehui li, Fumin Wang, Mingming Zhao, Fengyi Jiang, and Nan Chi

Doc ID: 331678 Received 12 Oct 2018; Accepted 15 Nov 2018; Posted 16 Nov 2018  View: PDF

Abstract: In this paper, we proposed a large-coverage underwater visible light communication (VLC) system utilizingQuadrature Amplitude Modulation-Discrete Multitone (QAM-DMT) and integrated 2×2 Positive-Intrinsic-Negative(PIN) array reception to do the Equal-Gain combining (EGC) receiving. The transmitter contains of lens group and ablue-emitting silicon substrate Light Emitting Diodes (LED) peak emission wavelength of which is 458nm. After1.2m underwater transmission, a data rate of over 1Gbit/s is successfully achieved with a spot of 25cm in diameterand 11cm alignment tolerances. A data rate of 1.8Gbit/s is also achieved when using parallel light reception. Bothare the highest data rates in large-coverage underwater VLC system, which shows the benefit and feasibility ofusing integrated PIN array with QAM-DMT modulation and EGC.

Strong coupling of metamaterial resonances tointersubband transitions of quantum dots forenhanced second harmonic generation

Jafar Hamidi and Mahdi Zavvari

Doc ID: 346661 Received 24 Sep 2018; Accepted 13 Nov 2018; Posted 15 Nov 2018  View: PDF

Abstract: Recently quantum confined structure have been widely studied for their nonlinear properties andapplications in harmonic generation. However because of lower orders of susceptibility, thegenerated harmonic power is low. In this paper we present coupling of metamaterial resonance tointersubband transitions of quantum dots (QD) for enhanced second harmonic generationefficiency. To do so, firstly the quantum dots are such designed to exhibit three electronic energylevels with identical energy spacing. The values of energy levels and the wavefunctions arecalculated by solving Schrodinger equation using modified effective mass approximation. Thesecond order nonlinear susceptibly of QD layers is then calculated and the results are used inFDTD simulation of structure. Metamaterial structure is also designed to resonate in responsefrequency of QDs. The results show that for a pump input with 24THz fundamental frequency, aharmonic with the 48 THz frequency appears in the output with conversion efficiency of about5*10-7.

In vivo hemodynamic visualization of berberineinducedeffect on mouse cerebral cortex byphotoacoustic tomography

DAN WU, Xiuyun Guo, Ruihuan Cui, Man Wu, Qiquan Shang, and Huabei Jiang

Doc ID: 345865 Received 17 Sep 2018; Accepted 12 Nov 2018; Posted 13 Nov 2018  View: PDF

Abstract: While berberine, a traditional Oriental herbal drug commonly used for treatment of diarrhea, has recently beenused to treat a number of brain disorders such as stroke and Alzheimer’s disease, berberine-induced changes inhemodynamics are largely unknown. Here we utilize photoacoustic tomography (PAT) to study hemodynamiceffects of berberine in mice. In vivo photoacoustic images are obtained in ten functional regions of mouse brain.Cortical vascular network and dynamic changes in total hemoglobin (HbT) concentration are acquired at 532 nm.Functional atlas and statistical data arealso obtained at low-dose and high-dose berberine. Our results providecompelling evidence that both low-dose and high-dose berberine can increase the HbT concentration to variedextent in certain brain regions. This study also suggests that PAT provides a powerful tool for visualizing brainhemodynamic changes induced by drugs.

Highly Sensitive Fiber Bragg Grating Based PressureSensor using Side-hole Packaging

Suneetha Sebastian, Sridhar S, Shivaprasad P, and Sundarrajan Asokan

Doc ID: 343102 Received 06 Sep 2018; Accepted 07 Nov 2018; Posted 08 Nov 2018  View: PDF

Abstract: In this work, an analysis of pressure response of Fiber Bragg Grating (FBG) sensor in side-hole package has beenpresented using finite element method. Various parameters of the side-hole packaging such as hole radius; thedistance of separation between them; the radius and length of the package and the choice of the package materialare considered and optimized in order to promote maximum pressure sensitivity of FBG sensor. This investigationon optimization of the side–hole package parameters gives rise to pressure sensitivity of nearly 105 times ascompared with the bare FBG sensor, with the numerical values of 3 pm/MPa for a bare FBG sensor, to ~2,80,000pm/MPa for optimized side–hole package FBG sensor. Such a high-pressure sensitivity of FBG sensor is beingreported for the very first time in this work and can be considered as the initial step towards the realization ofhighly sensitive hydrophone based on FBG, for sensing underwater acoustic signals.

Mesoporous plasmonic nanocompositesbased on Au/Ag-TiO2 aerogels as SERSsubstrates

Sima Sadrieyeh and Rasoul Malekfar

Doc ID: 347337 Received 03 Oct 2018; Accepted 06 Nov 2018; Posted 15 Nov 2018  View: PDF

Abstract: Au/Ag-TiO2 mesoporous nanocomposite aerogels are special materials that can beapplied as efficient surface-enhanced Raman spectroscopy (SERS) substrates, in order todetect low concentration of analytes from aqueous environments. At the same time, theybenefit from structural and intrinsic properties of aerogels and TiO2, respectively, and also theplasmonic effects of Au/Ag nanoparticles. Here, several composites of TiO2 aerogel modifiedwith various concentrations of Au, Ag and mixture of Au-Ag nanoparticles were prepared byapplying two different methods of synthesis. The SERS detection efficiency of thenanocomposites were established by using the dye crystal violate (CV) as test molecule. Thelowest concentration of CV detectable by SERS, which was 10-10 M, was found to depend onthe method of synthesis, size and type of the nanoparticles that were used in thenanocomposite structure. Besides, the morphological and structural characterizations of thenanocomposites were investigated through BET results, FESEM and TEM images.

Metamaterial structures of variable and gradient basisorientations embedded with periodic linear defects:phase engineered design, single step opticalrealization and applications

Saraswati Behera and Joby Joseph

Doc ID: 344630 Received 30 Aug 2018; Accepted 05 Nov 2018; Posted 06 Nov 2018  View: PDF

Abstract: Metamaterial structures of different basis shape, orientations and with gradient refractive index variations areapplicable in integrated photonics, miniaturized optoelectronics, diffraction limited focusing and super-resolutionimaging. We present design and experimental realizations of gradient metamaterial structures embedded withlinear periodic defects and propose its applications in on-substrate color filtering through simulation based study.A combination of phase engineered plane beams in double cone geometry and an axial plane beam are interferedto obtain different gradient basis metamaterial structures with linear defects in 2D and 3D respectively. The defectsize and spatial gradient amplitude modulations can be controlled computationally through shift in interferenceangle for some of the plane beams in double cone geometry without changing any optical components in theexperiment. The designed and realized metamaterial structures upon transferring to certain material will findapplication in optical circuits and in metalenses for enhanced light matter interactions.

Thin lens aberrations for anamorphic lenses

Zhang Jinkai, Xiaobo Chen, Haining Liu, Fajia Li, and Xuan Sun

Doc ID: 342202 Received 04 Sep 2018; Accepted 31 Oct 2018; Posted 01 Nov 2018  View: PDF

Abstract: This paper provided the thin lens aberrations for anamorphic lenses, including the Central Thin Lens Aberrations,the Central Lagrange Invariant Shift, the Central Conjugate Shift, and the Central Pupil Shift. Based on the thin lenstheory and the paraxial lens module, the aberration of the anamorphic lens system can be easily corrected. TheCentral Lagrange Invariant Shift can be used for aberration correction for anamorphic zoom lens system. In orderto make a concise expression for Central Conjugate Shift, eight aberration coefficients are introduced: D_3x, D_5x, D_6x,D _10x, D_11y, D_12x, D_15x, and D_16y. Similarly, four aberration coefficients are introduced for Central Pupil Shift, which areD11x, D_11x, D16x, D_16x. A simulation is conducted at last which proves numerically the validity of the thin lensaberrations for anamorphic lens system.

Intercomparison of airborne multi-angle polarimeterobservations from the Polarimeter DefinitionExperiment (PODEX)

Kirk Knobelspiesse, qian tan, Carol Bruegge, Brian Cairns, Jacek Chowdhary, Bastiaan van Diedenhoven, David Diner, Richard Ferrare, Gerard van Harten, Veljko Jovanovic, Matteo Ottaviani, Jens Redemann, Felix Seidel, and Kenneth Sinclair

Doc ID: 343215 Received 27 Aug 2018; Accepted 31 Oct 2018; Posted 04 Dec 2018  View: PDF

Abstract: In early 2013, three airborne polarimeters were flown on the high altitude NASA ER-2 aircraft in Californiafor the Polarimeter Definition Experiment (PODEX). PODEX supported the pre-formulation NASAAerosol-Cloud-Ecosystem (ACE) mission, which calls for an imaging polarimeter in polar orbit (amongother instruments) for the remote sensing of aerosols, oceans and clouds. Several polarimeter conceptsexist as airborne prototypes, some of which were deployed during PODEX as a capabilities test. Twoof those instruments to date have successfully produced Level 1 (georegistered, calibrated radiance andpolarization) data from that campaign: the Airborne Multiangle SpectroPolarimetric Imager (AirMSPI)and the Research Scanning Polarimeter (RSP). We compared georegistered observations of a variety ofscene types by these instruments to test if Level 1 products agree within stated uncertainties. Initial comparisonsfound radiometric agreement, but polarimetric biases beyond measurement uncertainties. Aftersubsequent updates to calibration, georegistration, and the measurement uncertainty models, observationsfrom the instruments now largely agree within stated uncertainties. However, the 470nm reflectancechannels have a roughly +6% bias of AirMSPI relative to RSP, beyond expected measurement uncertainties.We also find that observations of dark (ocean) scenes, where polarimetric uncertainty is expected tobe largest, do not agree within stated polarimetric uncertainties. Otherwise, AirMSPI and RSP observationsare consistent within measurement uncertainty expectations, providing credibility for subsequentcreation of Level 2 (geophysical product) data from these instruments, and comparison thereof. The techniquesused in this work can also form a methodological basis for other intercomparisons, such as ofthe data gathered during the recent Aerosol Characterization from Polarimeter and Lidar (ACEPOL) fieldcampaign, carried out in October and November of 2017 with four polarimeters (including AirMSPI andRSP).

Improvements to Dispersed Reference Interferometry:beyond the linear approximation

Andrew Henning, James Williamson, Haydn Martin, and Xiangqian Jiang

Doc ID: 345367 Received 11 Sep 2018; Accepted 28 Oct 2018; Posted 29 Oct 2018  View: PDF

Abstract: Interferometric instruments with dispersion introduced in the reference arm have previously been createdas the controlled dispersion can be used to generate a signal which contains a clearly identifiablepoint, the location of which relates to the position of the scattering surface in the measurement arm. Inthe following we illustrate that the linear approximations that have been used previously can lead to significanterrors, and that second order terms need to be included in order to correct this. These correctionsare vital if these instruments are to be used for metrological applications.

Fiber-Coupled LWIR Hyperspectral Sensor Suite forNon-Contact Component Surface TemperatureMeasurements

Paul Hsu, Keith Rein, Oleksandr Bibik, DAVID Wu, TIMOTHY COOK, SUBODH ADHIKARI, Benjamin Emerson, Timothy Lieuwen, James Gord, and Sukesh Roy

Doc ID: 345010 Received 05 Sep 2018; Accepted 26 Oct 2018; Posted 26 Oct 2018  View: PDF

Abstract: We report on the development of a robust fiber-coupled long-wavelength infrared (LWIR) hyperspectral sensorsuite for accurate and reliable non-contact surface temperature measurements in propulsion systems with limitedoptical access. We first experimentally investigate various state-of-the-art LWIR optical fibers and identify the idealfiber for reliable transmission of LWIR signals. The effects of the fiber material, structure, bending, and thermalheating on LWIR fiber transmission are characterized. Subsequently, we discuss the development of a fibercoupledLWIR hyperspectral sensor using a multi-mode polycrystalline fiber. The temperature measurementaccuracy and precision of the sensor are determined using a well-calibrated blackbody radiation source andheated thermal barrier coating (TBC). The sensor is integrated into a homemade water-cooled probe housing andenvironmental protection box and subsequently used for reliable combustor liner temperature measurements in ahigh-pressure, liquid-fueled combustor rig with no built-in optical access. We also discuss the measurementchallenges associated with flame interference and potential solutions. The LWIR sensor shows significant promisein its application to surface temperature measurements, and our findings can aid propulsion system engineers andresearchers in system design and operation optimization.

Multicore optical fiber based vibration sensors for biomedical applications

Md Rejvi Kaysir and Md Jahirul Islam

Doc ID: 331662 Received 16 May 2018; Accepted 28 Jul 2018; Posted 30 Jul 2018  View: PDF

Abstract: Vibration is one of the key parameters for extracting information from surrounding environments, and optical fiber-based sensors show great promise for achieving such information. In this work, an intensity-based multicore fiber (MCF) based vibration sensor is designed, fabricated and characterized for biomedical applications. The fabricated MCF has seven cores, in which the middle core is used for launching light and the surrounding cores are used for collecting lights from any reflective substances. The working principle of the MCF sensor is based on the intensity modulation of reflected light from vibrating substances that is coupled to the collecting cores (i.e. side cores) of the MCF. Here, light from a 532 nm laser was launched into the middle core of the MCF and the reflected light from a mirror, situated at the output face of MCF, was collected from a single side core. To characterize the sensor and demonstrate the sensing activities of MCF, two experimental approaches were taken: (i) static sensitivity and (ii) dynamic measurements. The static measurement demonstrated the region of maximum sensitivity and helped to find out the optimal design parameters of MCF for any desired applications. A simple ray tracing model also included getting the maximum sensitive regions of the designed sensor that verifies our experimental results. Dynamic measurement demonstrates the vibration sensing activities of the sensor. This information provides pathways to design MCF based vibration sensors for the specific applications.

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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