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Accepted papers to appear in an upcoming issue

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Optical device terahertz integration in 2D-3D hetero-structure

zhifang Feng, Jie Lin, and shuai feng

Doc ID: 310154 Received 27 Oct 2017; Accepted 08 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: The transmission properties of off-planar integrated circuit included two wavelength division demultiplexers are designed, simulated, and analyzed in detail by the finite-difference time-domain method. The results show that the wavelength selection for different ports (0.404[c/a] for B2 port, 0.389[c/a] for B2 portand0.394[c/a] for B2 port) can be realized by adjusting the parameters. Especially, it is important that the off-planar integration between two complex devices is also realized. This simulation may be valuable in the all-optical integrated circuit, especially in compact integration.

The impact of input field characteristics on vibrationalfemtosecond coherent anti-Stokes Raman scatteringthermometry

Chaobo Yang, He Ping, David Escofet Martin, Jiang bo Peng, Rongwei Fan, Xin Yu, and Derek Dunn-Rankin

Doc ID: 306495 Received 07 Sep 2017; Accepted 07 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: In this paper, three ultrashort-pulse coherent anti-Stokes Raman scattering (CARS) thermometry approachesare summarized with a theoretical time-domain model. The difference between the approachescan be attributed to variations in the input field characteristics of the time-domain model. That is, allthree approaches of ultrashort-pulse (CARS) thermometry can be simulated with the unified model byonly changing the input fields features. As a specific example, the hybrid femtosecond/picosecond CARSis assessed for its use as a combustion flow diagnostics so the examination of the input field impacts onthermometry focuses on vibrational hybrid femtosecond/picosecond CARS. Beginning with the generalmodel of ultrashort-pulse CARS, the spectra with different input field parameters are simulated. To analyzethe temperature measurement error brought by the input field impacts, the spectra are fitted andcompared to fits with the model neglecting the influence introduced by the input fields. The resultsdemonstrate that however the input pulses are depicted, temperature errors still would be introducedduring an experiment. With proper field characterization, however, the significance of the error can bereduced.

Determination of Toxic and Essential Metals in Rock and Sea SaltsUsing Pulsed Nanosecond Laser-Induced Breakdown Spectroscopy(LIBS)

Imran Rehan, M Zubair Khan, Kamran Rehan, Abdul Mateen, Muhammad AAmar, Sabiha Sultana, and Zahid Farooq

Doc ID: 307550 Received 19 Oct 2017; Accepted 07 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: A spectrometer based on pulsed nanosecond Laser induced breakdown spectroscopy (LIBS) wasapplied for the quantitative determination of heavy and essential metals in salts from various sourcesavailable in Pakistan. Six salt samples were collected from sea salt and rock salt. Toxic metals (Cu,Cd, and Ni) and other micro essentials (Fe, Ca, Co, Mg, Mn, S, and Zn) were investigated from therecorded spectra. The detection system was calibrated using parametric dependence study. Thequantitative analyses were accomplished under the assumption of local thermodynamic equilibrium(LTE) and optically thin plasma. The results by LIBS technique were agreed to the outcomes ofsame samples studied using more standard approach like Inductively Coupled Plasma-AtomicEmission Spectroscopy (ICP-AES). When the concentrations of heavy and essential metals werecalculated using calibration-free (CF)-LIBS method that does not need standard salt specimen anddilution, both LIBS and ICP-AES were also in good agreement. Limit of detection (LOD) ofexperimental set up was determined for the observed heavy metals in the studied samples.

Inverse Synthetic Aperture LADAR demonstration:System Structure, Imaging Processing and ExperimentResult

NING WANG, wang ran, Di Mo, Guangzuo Li, keshu zhang, and Yirong Wu

Doc ID: 308032 Received 28 Sep 2017; Accepted 06 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: A long-distance inverse system aperture LADAR (ISAL) imaging experiment outdoor over 1 km for cooperative targets is demonstrated, which gets a two-dimensional high-resolution image with resolution exceeded 2.5 cm. The system utilizes an electro-optic in-phase and quadrature modulator to output a linear frequency-modulated continuous waveform (LFMCW) with a bandwidth of 6 GHz and pulse repetition frequency (PRF) of 16.7 KHz. For the problem of the coherence of laser, the effects of coherent processing interval (CPI) and time delay of the local oscillator (LO) on the coherence are discussed. By setting the fiber delay line and reducing the CPI to lower the requirement of the frequency stability of the laser source. The images are formed by two-dimensional Fourier transform and joint time-frequency transform method, respectively. In this paper, we present the system structure, imaging processing and the experiment result in detail. The experiment result validates the performance of our system for ISAL imaging.

Simultaneous trilateral communication based onthree mutually coupled chaotic semiconductorlasers with optical feedback

Qiliang Li, lu shan, Qi Bao, DeWang Chen, Miao Hu, Ran Zeng, Guowei Yang, and Shuqin li

Doc ID: 310182 Received 03 Nov 2017; Accepted 06 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: In this paper, we propose a chaos-based scheme allowing for trilateral communication among three mutually coupled chaoticsemiconductor lasers. The coupling through a partially transparent optical mirror between two lasers induces the chaotic dynamics.We numerically solve the delay rate equations of three lasers and demonstrate that the dynamics is completely synchronous. Herein,each laser is not only a transmitter but a receiver; three different messages are encoded by simultaneously modulating bias current ofthree lasers. By monitoring the synchronization error between transmitter and receiver, and comparing the error with the messageof the local laser, we can decipher the message of sender. The investigation indicates that these messages introduced on the two endsof each link among three lasers can be simultaneously transmitted and restored, so the system can realize simultaneous trilateralcommunication. In this scheme, an eavesdropper can monitor the synchronization error, but one has no way to obtain the bits whichare being sent, so the trilateral communication is secure.

Rapid acousto-optic focus tuning for improvement ofimaging performance in confocal microscopy

Krzysztof Szulżycki, Viktoriya Savaryn, and Ireneusz Grulkowski

Doc ID: 313194 Received 16 Nov 2017; Accepted 06 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: We demonstrate the application of focus tunable acousto-optic lens technology in confocal microscopy for a highspeedaxial scanning of the object. The advantages of the proposed approach include high axial scan rate, nomechanical sample movement, no additional non-symmetric aberrations and the control of the effective depth offocus. The acousto-optic lens operating at the focus tuning rate of 300 kHz is developed and implemented inscanning laser confocal microscopy. The performance of the instrumentation is presented using test targets. Rapidfocus tuning may enhance in vivo three-dimensional imaging in confocal microscopy.

Random Fiber Laser Based on Artificially ControlledBackscattering Fibers

XIAOLIANG Wang, Daru Chen, Haitao Li, Lijuan She, and qiong wu

Doc ID: 306762 Received 27 Sep 2017; Accepted 06 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: The random fiber laser which is a milestone in laser physics and nonlinear optics, has attracted considerableattention recently. Most previously reported RFLs are based on distributed feedback of Rayleigh scatteringamplified through stimulated Raman/Brillouin scattering effect in single mode fibers, which require long-distance(tens of kilometers) single mode fibers and high threshold up to watt-level due to the extremely small Rayleighscattering coefficient of the fiber. We proposed and demonstrated a half-open cavity random fiber laser based on asegment of an artificially controlled backscattering single mode fiber with a length of 210 m, 310 m or 390 m. Afiber Bragg grating with the central wavelength of 1530 nm and a segment of artificially controlled backscatteringsingle mode fiber fabricated by using the femtosecond laser forms the half-open cavity. The proposed random fiberlaser achieves the threshold of 25mW, 30 mW and 30 mW, respectively. Random lasing at the wavelength of 1530nm and the extinction ratio of 50 dB is achieved when a segment of 5m EDF is pumped by a 980 nm LD in therandom fiber laser. The novel random fiber laser with much short cavities have been achieved with low threshold.

Frequency down-conversion with independent multichannel phase shifting and zero-IF receiving based on optical frequency shift and polarization multiplexing

zihang zhu, Zhao ShangHong, xuan li, tao lin, and Dapeng Hu

Doc ID: 306831 Received 12 Sep 2017; Accepted 06 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: Photonic microwave frequency down-conversion with independent multichannel phase shifting and zero-intermediate frequency (IF) receiving via an integrated polarization multiplexing dual-parallel Mach-Zehnder modulator (PM-DPMZM) is proposed. Based on the ideas of optical frequency shift and polarization multiplexing, the radio frequency (RF) signal is frequency down-converted to multichannel IF signals with the phases independently and arbitrarily tuned by adjusting the polarization controllers (PCs) or even frequency down-converted to baseband directly by choosing two quadrature channels. In the simulation, the gain of our proposed frequency down-conversion system is higher than that of the conventional two cascaded MZMs system and the phase shift with the range of 360 degree can be obtained concurrently. Furthermore, 2.5 Gbit/s RF vector signals centered at 10 GHz with different modulation formats are successfully demodulated.

Simultaneous determination of the size andconcentration of fine bubbles in water by laser-lightscattering

Kayori Takahashi, SEIKA OHUCHI, KEIZO SAITO, MAKOTO HIRASAWA, and Hiromu Sakurai

Doc ID: 309667 Received 23 Oct 2017; Accepted 06 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: The preparation of nanoscale fine bubbles in water is an innovative technology, but no precise method forsimultaneously measuring the size and concentration of such bubbles had previously been developed. We havedeveloped a method for simultaneously determining the size and concentration of fine bubbles in water by a lightscatteringtechnique. Dynamic light scattering gives the diffusion constant and particle size of fine bubbles,whereas static light scattering provides their concentration or molar mass. Static light scattering also provides theradius of gyration of the bubbles, thereby providing a means for validating measurements of the sizes of the finebubbles.

Projected Image Correction Technology Research on Autonomous-Perception Anisotropic Surfaces

Fan Yang, han cheng, Bao Bai, and Chao Zhang

Doc ID: 303297 Received 25 Jul 2017; Accepted 05 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: In this paper, a projection correction method was proposed for autonomous-perception depth anisotropic surfaces, in order to improve the adaptive perceptual projection of the projection equipment under different circumstances. During the parameter calibration process of a projector-camera system with low recognition precision, as well as low noise resistance at angular points, an angular-point subpixel detection algorithm based on color information guidance, were proposed to effectively improve the identification precision of the angular-point detection. Meanwhile, the projection geometry correction algorithm was proposed, which was based on the topology analysis, in order to analyze the spatial topology distribution of the depth anisotropic surface, and to also solve the homography matrix in the different regions of the anisotropic surface. Eventually, the homography matrix was used for the geometric distortion correction of the projection distortion image. The experimental analysis showed that the identification accuracy of the proposed method achieved 0.25 pixel, with simultaneous high planar parallelism and liner perpendicularity. In the meantime, through utilizing this method for the projection correction of the depth anisotropic surface, which confirmed that the geometric distortion correction precision of the proposed method had reached the subpixel level, as well as confirming the consistency level of the imaging picture.

Bicontrollable Terahertz Metasurface with Subwavelength Scattering Elements of Two Different Materials

Francesco Chiadini and Akhlesh Lakhtakia

Doc ID: 305279 Received 23 Aug 2017; Accepted 05 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: Transmission of a normally incident plane wave through a metasurface with bicontrollable subwave- length scattering elements was simulated using a commercial software. Some pixels comprising the H- shaped scattering elements were made of a magnetostatically controllable material whereas the remaining pixels were made of a thermally controllable material, the metasurface designed to operate in the terahertz spectral regime. The co-polarized transmission coefficients were found to exhibit stopbands that redshift when either a magnetostatic field is applied or the temperature is increased or both. The magnetostatic field gives coarse control whereas temperature gives fine control. The level of coarse control depends on the magnetostatic-field configuration.

A comprehensive 3-dimensional ray tracing model for3-mirror cavity-enhanced spectroscopy

Faisal Nadeem, Berber Postma, Geert Postma, Simona Cristescu, Julien Mandon, and Frans J. Harren

Doc ID: 306150 Received 11 Sep 2017; Accepted 04 Dec 2017; Posted 05 Dec 2017  View: PDF

Abstract: A 3-D ray tracing model is used to simulate optical re-injection in a non-resonant optical cavity, for Off-AxisIntegrated Cavity Output Spectroscopy (OA-ICOS). The optical cavities are optimized for maximum intensityenhancement factors via a grid search and a genetic algorithm. Intensity enhancements factors up to 1400 arefound for short cavities (3 cm) and up to 101 for long cavities (50 cm). The model predicts that short absorptioncells can be used, having a long effective path length and a high throughput power. This opens new opportunities inthe field of ultrasensitive absorption spectroscopy and allows the design of compact optical gas sensors.

Talbot-Lau x-ray deflectometry phase retrieval methods for electron density diagnostics in High Energy Density experiments

Maria Valdivia, Dan Stutman, Christian Stoeckl, Chad Mileham, Ildar Begishev, Jake Bromage, and Sean Regan

Doc ID: 308751 Received 09 Oct 2017; Accepted 04 Dec 2017; Posted 05 Dec 2017  View: PDF

Abstract: Talbot-Lau x-ray interferometry uses incoherent x-ray sources to measure refraction index changes in matter. These measurements can provide accurate electron density mapping through phase-retrieval. An adaptation of the Interferometer has developed in order meets the specific requirements of High Energy Density experiments. The Moiré deflectometer is a particular configuration of the Talbot-Lau x-ray interferometer with single-shot capabilities. The Moiré X-ray Deflectometry technique requires a set of object and reference images in order to provide electron density maps, which can be costly in the High Energy Density environment. In particular, synthetic reference phase images obtained ex-situ through a phase-scan procedure, can provide a feasible solution. To test this procedure, an object phase map was retrieved from a single-shot Moiré image obtained from a plasma-produced x-ray source. Then, a reference phase map was obtained from phase-stepping measurements using a continuous x-ray tube source in a small laboratory setting. These two phase maps were used to retrieve an electron density map. A comparison of the Moiré and phase stepping phase retrieval methods was performed to evaluate single-exposure plasma electron density mapping for High Energy Density and other transient plasma experiments. It was found that a combination of phase-retrieval methods can deliver accurate refraction angle mapping. Once x-ray backlighter quality is optimized, the ex-situ method is expected to deliver electron density mapping with improved resolution. The steps necessary for improved diagnostic performance are discussed.

Volume holographic spatial mode demultiplexer withdual-wavelength method

Shimpei Shimizu, Atsushi Okamoto, Fumiya Mizukawa, Kazuhisa Ogawa, Akihisa Tomita, Taketoshi Takahata, Satoshi Shinada, and Naoya Wada

Doc ID: 308954 Received 10 Oct 2017; Accepted 04 Dec 2017; Posted 05 Dec 2017  View: PDF

Abstract: Volume holographic demultiplexers (VHDMs) provide spatial mode demultiplexing using simple optical systems.However, applying VHDM to practical optical communication systems is difficult, as typical holographic mediumshave no sensitivity in the infrared region, which includes optical transmission bands. In this paper, we propose aVHDM scheme combined with a dual-wavelength method (DWM). Using the DWM, VHDMs are able to performmode demultiplexing in the optical transmission bands. We experimentally demonstrated the basic operation ofour proposal using experiments performed at an 850-nm wavelength. In addition, we performed numericalsimulations to investigate the application of VHDM to the C-band..

Adaptive compensation of intracavity tilts duringlasing through detecting the direction of outputbeams

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

Doc ID: 309770 Received 23 Oct 2017; Accepted 04 Dec 2017; Posted 05 Dec 2017  View: PDF

Abstract: We present adaptive compensation of intracavity tilts based on detecting the direction of output beams. Weuse the initial direction of the output beam when the laser cavity is well collimated as reference. Then thedifference between the actual direction of the output beam and the reference is used as the feedback tocontrol the intracavity tip/tilt mirror. The relation between the direction of output beam and intracavity tilt isinvestigated with both Fox-Li method and measurements. A series of experiments demonstrate thatintracavity tilts could be well compensated by the proposed method. We have also proved that it is possible tosubstitute the proposed method for conventional extra cavity beam stabilization.

Suppressing the influence of CCD vertical blooming on the measurement of laser beam quality factor (M2) of a near-infrared laser

Lingqiang Meng, Kunhao Ji, Qingqing Kong, Zhigang Han, Hua Shen, and Rihong Zhu

Doc ID: 309866 Received 24 Oct 2017; Accepted 04 Dec 2017; Posted 05 Dec 2017  View: PDF

Abstract: In this paper, a new method, which is based on reconstructing the original intensity distribution of a laser with images captured by a charged-coupled device (CCD) in two orthogonal directions, is proposed for suppressing the influence of CCD vertical blooming on the measurement of the laser beam quality factor (M2). A simplified theoretical model for the distribution of CCD blooming is also proposed. With the proposed method and model, the influence of CCD vertical blooming on the measurement of M2 is simulated. The experimental results demonstrate that the new method can be an effective means to measure the M2 of a NIR laser with a silicon CCD camera. The proposed method can be applied to a beam quality analyzer in order to suppress the influence of blooming on the measurement of M2.

Highly directive plasmonic structure with double resonance at excitation and emission for molecule’s enhanced fluorescence

Guoguo Kang and FANGZHOU WANG

Doc ID: 308123 Received 28 Sep 2017; Accepted 04 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: An improved bull’s eye nanostructure is proposed as a substrate for surface enhanced fluorescence. Optimized by FDTD, annular corrugation on both upper and lower surfaces are placed around a nano bowtie in the middle. The whole structure is designed for the excitation and emission process of a certain fluorescence simultaneously, which can enhance the fluorescence intensity enormously (35 times for excitation field and 120 times for radiation, independently). Meanwhile, it is able to confine the far-field emission energy within a divergence angle of ±3.5 degrees. The dual-resonant enhancement and directivity of such substrate allows higher sensitivity during fluorescence detection. Furthermore, the designed resonance and directional light control at emission may effectively reduce the required energy at excitation, which is ideal for those molecules with low laser change threshold.

Ray tracing method for the evaluation of grazingincidence X-ray telescopes described by spatiallysampled surfaces

Jun Yu, zhengxiang shen, Pengfeng Sheng, Xiaoqiang Wang, Charles Hailey, and Zhanshan Wang

Doc ID: 306678 Received 07 Sep 2017; Accepted 04 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: The nested grazing incidence telescope can achieve large collecting area in X-ray astronomy, with a large number of closelypacked, thin conical mirrors. Exploiting the surface metrological data, the ray tracing method used to reconstruct the shellsurface topography and evaluate the imaging performance, is a powerful tool to assist iterative improvement in thefabrication process. However current 2-dimensional (2D) ray tracing codes, especially when utilized with densely sampledsurface shape data, may not provide sufficient accuracy of reconstruction, and are computationally cumbersome. Inparticular, 2D ray tracing currently employed considers coplanar rays and thus only simulates these rays along themeridional plane. This captures axial figure errors, but leaves other important errors, such as roundness errors,unaccounted for. We introduce a semi-analytic, 3-dimensional (3D) ray tracing approach for X-ray optics that overcomesthese shortcomings. And the present method is both computationally fast and accurate. We first introduce the principlesand the computational details of this 3D ray tracing method. Then the computer simulations of this approach compared to2D ray tracing are demonstrated, using an ideal conic Wolter-I telescope for benchmarking. Finally, the present 3D raytracing is used to evaluate the performance of a prototype X-ray telescope fabricated for the enhance X-ray Timing andPolarization (eXTP) mission.

Time resolved study of optical properties and microscopic dynamics during the drying of TiO2 films by spectral diffusing wave spectroscopy

Angel Duran-Ledezma, Damian Jacinto-Méndez, and Luis Rojas-Ochoa

Doc ID: 306122 Received 05 Sep 2017; Accepted 04 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: We present a combined experimental, theoretical and numerical study of photon transport and microscopic dynamics in rigid and drying turbid thin films. Our setup is based in multi-speckle diffusing wave spectroscopy and is adapted for frequency sweep of the illuminating source. We apply our approach to simultaneously monitor the changes in optical properties and microscopic dynamics of turbid thin films of rutile TiO2 powder dispersed in ethanol during the full drying process. Accordingly, we introduce an extension of the photon diffusion model for spectral speckle intensity correlations to account for systems microscopic dynamics. We find that our results are well described by the model, where parameters required as the time dependent sample thickness and transport mean free path are obtained from experiments. Furthermore, our findings are validated by numerical simulations of speckle dynamics based on the copula scheme. We consider that our scheme could be useful in time resolved physical characterization of time evolving turbid thin systems.

Ultrafast and low power crystallization in Ge1Sb2Te4 andGe1Sb4Te7 thin films using femtosecond laser pulses

Smriti Sahu, Rituraj Sharma, KV Adarsh, and Anbarasu Manivannan

Doc ID: 307767 Received 22 Sep 2017; Accepted 03 Dec 2017; Posted 05 Dec 2017  View: PDF

Abstract: Rapid and reversible switching between amorphous and crystalline phases of phase change materialpromises to revolutionize the field of information processing with a wide range of applications includingelectronic, optoelectronics and photonic memory devices. However, achieving faster crystallization is a keychallenge. Here, we demonstrate femtosecond-driven transient inspection of ultrafast crystallization of asdepositedamorphous Ge1Sb2Te4 and Ge1Sb4Te7 thin films induced by a series of 120 fs-laser pulses. Thesnapshots of phase transitions are correlated with the time-resolved measurements of change in theabsorption of the samples. The crystallization is attributed to the reiterative excitation of an intermediatestate with sub-critical nuclei at a strikingly low fluence of 3.19 mJ/cm2 for Ge1Sb2Te4 and 1.59 mJ/cm2 forGe1Sb4Te7. Furthermore, 100 % volumetric crystallization of Ge1Sb4Te7 was achieved with the fluence of4.78 mJ/cm2 and also re-amorphization is seen for a continuous stimulation at the same repetition rate andfluence. A systematic confirmation to structural transformations of all samples is validated by Ramanspectroscopic measurements on the spots produced by the various excitation fluences.

Signal-to-noise ratio of single-pixel cameras based onphotodiodes

YESSENIA JAUREGUI SANCHEZ, Pere Clemente, Pedro Latorre Carmona, Enrique Tajahuerce, and Jesus Lancis

Doc ID: 308419 Received 03 Oct 2017; Accepted 03 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: Single-pixel cameras have been successfully used in different imaging applications in the last years. Oneof the key elements affecting the quality of these cameras is the photodetector. Here we develop a numericalmodel of a single-pixel camera, which takes into account not only the characteristics of the incidentlight but also the physical properties of the detector. In particular, our model considers the photocurrent,the dark current, the photocurrent shot noise, the dark current shot noise, and the Johnson-Nyquist (thermal)noise of the photodiode used as light detector. The model establishes a clear relationship betweenthe electric signal and the quality of the final image. This allows us to perform a systematic study of thequality of the image obtained with single-pixel cameras in different contexts. In particular, we study thesignal-to-noise ratio (SNR) as a function of the optical power of the incident light, the wavelength, andthe photodiode temperature. The results of the model are compared with those obtained experimentallywith a single-pixel camera.

Sequential Fitting-and-Separating ReflectanceComponents for Analytical BRDF Estimation

Yu Lee, Chanki Yu, and Sang Lee

Doc ID: 305379 Received 13 Sep 2017; Accepted 03 Dec 2017; Posted 05 Dec 2017  View: PDF

Abstract: We present a sequential fitting-and-separating algorithm for surface reflectance components that separatesindividual dominant reflectance components and simultaneously estimates the corresponding BidirectionalReflectance Distribution Function (BRDF) parameters from the separated reflectance values. We tackle theestimation of a Lafortune BRDF model, which combines a non-Lambertian diffuse reflection and multiple specularreflectance components with a different specular lobe. Our proposed method infers the appropriate number ofBRDF lobes and their parameters by separating-and-estimating each of the reflectance components using aninterval analysis-based branch-and-bound method in conjunction with Iterative K-Ordered Scale Estimation. Thefocus of this paper is the estimation of the Lafortune BRDF model. Nevertheless, our proposed method can beapplied to other analytical BRDF models such as the Cook-Torrance and Ward models. Experiments were carriedout to validate the proposed method using isotropic materials from the MERL-MIT BRDF database and the resultsshow that our method is superior to a conventional minimization algorithm.

Model-assisted measuring method for periodical subwavelengthnanostructures

Gabriela Alexe, ANDREAS TAUSENDFREUND, Dirk Stöbener, and Andreas Fischer

Doc ID: 303071 Received 21 Jul 2017; Accepted 02 Dec 2017; Posted 04 Dec 2017  View: PDF

Abstract: This paper describes a scatterometry approach designed by simulations for the in-line characterization of subwavelengthsinusoidal gratings, which are formed on a transparent foil in a roll-to-roll procedure. Currently usedmethods are based on series of in-situ measurements of the specular optical response at different incident anglesor wavelengths for acquiring dimensional information of the gratings. The capability of single measurements of thefirst diffraction maxima at a fixed incident angle and wavelength to accurately measure the height of the subwavelengthsinusoidal gratings is investigated in this work. The relation between the scattered powers of thediffraction maxima and the grating height is extracted from light scattering simulations, i.e., the inverse problem issolved. Optimal setup parameters for the measurement of grating heights ranging from 100 nm to 300 nm arederived from simulations. Limits of measurability and the measurement uncertainty are evaluated for differentinstrumentation and simulation parameters. When using laser light in the visible wavelength range, themeasurement uncertainty is physically limited by the photon shot noise to the picometre range, but the systematiccontributions dominate the uncertainty. As a result, the measurement uncertainty for the grating height isestimated to ≤12 nm, with a potential for <4 nm. Large area scanning measurements performed offline andreference atomic force microscopy measurements verify the sensitivity of the presented measurement approachfor identifying local variations of the spatial surface properties. Depending on the chosen detection system,sampling rates up to the MHz range are feasible meeting the requirements of in-line process control of the roll-torollproduction process.

All Polymer Thermal Optical Switch using for Flexible Photonic Circuit

Yue Sun, Yue Cao, Qi Wang, Yi Yunji, Xiaoqiang Sun, Yuanda Wu, Fei Wang, and Da-Ming Zhang

Doc ID: 308847 Received 17 Oct 2017; Accepted 01 Dec 2017; Posted 01 Dec 2017  View: PDF

Abstract: Flexible and wearable optoelectronic devices are the new trend for an active lifestyle. These devices are polymer-based for flexibility. We demonstrated flexible all polymer waveguide optical switches for a flexible photonic integrated circuit. The optical switches are composed of a single mode invert waveguide with dimensions of 5μm waveguide width, 3μm ridge height, and 3μm slab height. M-Z structure was used in the device, with a Y branch angle less than 1°and heating branch length of 1cm. The optical field of the device was simulated by beam propagation to optimize the electrode position. The switching properties of the flexible optical switch with different working conditions, such as contact to the polymer, silicon, and skin, were simulated. The device was prepared based on the photo curved polymer and lithography method. The end faces of the flexible film device were processed using an excimer laser with optimized parameters of 28mJ/cm2 and 15 Hz. The response rise time and fall time on the PMMA substrate were measured as 1.98 ms and 2.71ms. The power consumption was 80mW and the extinction ratio was 11 dB. The response rise and fall time on the Si substrate were measured as 1.08 ms and 1.62ms, respectively. The power consumption was 85mW and the extinction ratio was 11 dB. The demonstrated properties indicate that this flexible optical waveguide structure can be used in the light control area of a wearable device.

Evaluation of Finite Difference and FFT-Based Solutions of theTransport of Intensity Equation

Honbo Zhang, Wenjing Zhou, Donald Leber, Partha Banerjee, Mahmudunnabi basunia, Ting-Chung Poon, and Ying Lui

Doc ID: 303950 Received 02 Aug 2017; Accepted 01 Dec 2017; Posted 01 Dec 2017  View: PDF

Abstract: A finite difference method is proposed for solving the transport of intensity equation. Simulation results show that although slower than FFT basedmethods, finite difference methods are able to reconstruct the phase with better accuracy due to relaxed assumptions for solving the transport ofintensity equation relative to FFT methods. Finite difference methods are also more flexible than FFT methods in dealing with different boundaryconditions.

Hybrid Sensing Face Detection and Registration forLow Light and Unconstrained Conditions

Mingyuan Zhou, haiting Lin, Jingyi Yu, and S. Young

Doc ID: 305383 Received 23 Aug 2017; Accepted 01 Dec 2017; Posted 01 Dec 2017  View: PDF

Abstract: The capability to track, detect, and identify human targets in highly cluttered scenes under extreme conditions,such as in complete darkness or on the battlefield, has been one of the primary tactical advantagesin military operations. In this paper, we propose a new collaborative, multi-spectrum sensing method toachieve face detection and registration under low-light and unconstrained conditions. We design and prototypea novel type of hybrid sensors by combining a pair of near-infrared (NIR) cameras and a thermalcamera (a long-wave infrared camera). We strategically surround each NIR sensor with a ring of LED IRflashes to capture the “red-eye”, or more precisely, the “bright-eye” effect of the target. The “bright-eyes”are used to localize the 3D position of eyes and face. The recovered 3D information is further used towarp the thermal face imagery to a frontal-parallel pose so that additional tasks such as face recognitioncan be reliably conducted, especially with the assistance of accurate eye locations. Experiments on realface images are provided to demonstrate the merit of our method.

Broadband perfect infrared absorption by tuningepsilon-near-zero and epsilon-near-pole resonances ofmultilayer ITO nanowires

Kun Zhou, Qiang Cheng, Jinlin Song, Lu Lu, Zhihao Jia, and JunWei Li

Doc ID: 300673 Received 30 Jun 2017; Accepted 30 Nov 2017; Posted 05 Dec 2017  View: PDF

Abstract: We numerically investigate the broadband perfect infrared absorption by tuning epsilon-near-zero (ENZ) andepsilon-near-pole (ENP) resonances of multilayer indium tin oxide nanowires (ITO NWs). The monolayer ITONWs array shows intensive absorption at ENZ and ENP wavelengths for p polarization, while only at ENPwavelength for s polarization. Moreover, the ENP resonances are almost omnidirectional and the ENZresonances are angularly dependent. Therefore, the absorption bandwidth is broader for p polarization thanthat for s polarization when polarized waves are incident obliquely. The ENZ resonances can be tuned byaltering the doping concentration and volume filling factor of ITO NWs. However, the ENP resonances onlycan be tuned by changing the doping concentration of ITO NWs, and volume filling factor impacts little on theENP resonances. Based on the strong absorption properties of each layer at their own ENP and ENZresonances, the tuned absorption of the bilayer ITO NWs with the different doping concentrations can bebroader and stronger. Furthermore, multilayer ITO NWs can achieve broadband perfect absorption bycontrolling the doping concentration, volume filling factor, and length of the NWs in each layer. This study hasthe potential to apply to applications requiring efficient absorption and energy conversion.

Fast switching optically isotropic liquid crystal nanodropletswith improved depolarization and Kerr effectby doping high k nanoparticles

Byeonggon Kim, Hyun Gyu Kim, Gyuyeop Shim, Ji-Sub Park, Kyung-Il Joo, Dong-Jin Lee, Joun-Ho Lee, Ji-Ho Beak, Byeong Koo Kim, Yoonseuk Choi, and Hak Rin Kim

Doc ID: 307261 Received 18 Sep 2017; Accepted 30 Nov 2017; Posted 05 Dec 2017  View: PDF

Abstract: We proposed and analyzed an optically isotropic nano-droplet liquid crystal (LC) doped with high k nanoparticles(NPs), exhibiting enhanced Kerr effects, which could be operated with reduced driving voltages. For enhancing thecontrast ratio together with the light efficiencies, the LC droplet sizes were adjusted to be shorter than thewavelength of visible light to reduce depolarization effects by optical scattering of the LC droplets. Based on theoptical analysis of the depolarization effects, the influence of the relationship between the LC droplet size and theNP doping ratio on the Kerr effect change was investigated.

Single-shot polarization digital holography for recording stimulated Raman scattering signal for time-resolved measurement of gaseous species

Eynas Amer, Per Gren, and Mikael Sjodahl

Doc ID: 306944 Received 12 Sep 2017; Accepted 29 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Polarization pulsed digital holography was used to record the stimulated Raman scattering (SRS) signal from one single-shot hologram based on the polarization sensitivity of the SRS process. A Q-switched Nd-YAG laser (532 nm) was used to pump methane gas (CH4) at a pressure of 12 bars. The frequency tripled (355 nm) beam from the same laser is used to pump an optical parametric oscillator (OPO). The Stokes beam (from the OPO) was tuned to 629.93 nm so that the frequency difference between the pump (532 nm) and the Stokes (629.93 nm) beams fits a Raman active vibrational mode of the methane molecule (2922 cm-1). The pump beam was spatially modulated with fringes produced in a Michelson interferometer. The pump beam polarization was kept vertical while the Stokes beam polarization was 45o. The two polarization components of the Stokes beam were recorded in a single hologram by blending the Stokes beam with two reference beams with orthogonal polarization on the detector. The two components of the Stokes beam were separated in the Fourier domain and the corresponding intensity maps were calculated. The vertically polarized component of the Stokes beam was amplified due to the SRS process while the horizontal component experienced no gain. The difference between the vertically and the horizontally polarized intensity maps, respectively was calculated and Fourier transformed to separate the gain signal in the spatial frequency domain. The results show that SRS polarization holography is a promising technique for recording the SRS signal from one single-shot hologram for time-resolved monitoring of specific species.

Sequences of the ranged amplitudes as a universal method for fast noninvasive characterization of SPAD dark counts

Maksim Smirnov, Nikolay Perminov, Raoul Nigmatullin, Anvar Talipov, and Sergey Moiseev

Doc ID: 307068 Received 13 Sep 2017; Accepted 28 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Single-photon detectors based on avalanche photodiodes (SPAD) are key elements of many modern highly sensitive optical systems. One of the bottlenecks of such detectors is a afterpulsing effect which limits a detection rate and requires an optimal hold-off time. In this letter we propose a novel approach for statistical analysis of SPAD dark counts and we demonstrate its usefulness for the search of the experimental condition where the afterpulsing effect can be strongly eliminated. This approach exploits a sequence of ranked time intervals between the dark counts and does not contain a complex mathematical analysis of the experimental data. We show that the approach can be efficiently applied for a small number of the dark counts and it seems to be very beneficial for practical characterization of SPAD devices.

Modulation transfer function of liquid crystalmicrolenses and microprisms using double dielectriclayer

Oleksandr Sova, Victor Reshetnyak, and Tigran Galstian

Doc ID: 301921 Received 07 Jul 2017; Accepted 28 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: We investigate electrically tunable liquid crystal (LC) microlenses and microprisms based on double dielectricoptically hidden (DDOH) layers. Comparative theoretical study of the spatial resolution limits in the creation ofspatially modulated electric field by the DDOH layer is conducted. Both the depth of the resulting optical phasemodulation and its deviation from the desired wavefront are obtained for sine and sawtooth geometries of theDDOH layer’s structure. A comparison is provided with the standard LC reorientation approach using patternedelectrodes.

High-precision rotation angle measurement methodbased on lensless digital holographic microscope

Yumin Wu, Haobo cheng, and Yongfu Wen

Doc ID: 304827 Received 20 Sep 2017; Accepted 28 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: To accurately measure ultra-small rotation angles, a robust and effective method based on lensless digitalholographic microscopy is proposed in this paper. The method combines holographic microscopy, solid geometry, and3D measurement, including holographic measurement process and angle measurement process. We can calculatethe three-dimensional shape by angular spectrum algorithm and the least-squares phase-unwrapping algorithm inthe holographic process. According to the relationship between the surface shape and rotation angles, the real-timerotation angles can be calculated. To validate the feasibility and practicability of the proposed approach, numericalnoise simulations and experiments were performed. The measurement precision of rotation angle can reach 0.5″in the range of 1000″ in this paper’s experiments. The holographic method has the high measurement precisionand good stability. In addition, the compact small volume has great potential in small angle sensor applications.

Investigation of faithful reconstruction in the non-paraxial approximation polarization holography

Yifan Hong, Guoguo Kang, Jinliang Zang, fan lan, Ying Liu, Xiaodi Tan, Tsutomu Shimura, and Kazuo kuroda

Doc ID: 308191 Received 29 Sep 2017; Accepted 28 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Faithful reconstruction, polarization state of the diffraction wave being identical to that of the signal wave, is the primary target in polarization holography. With the large crossing angle between signal and reference wave, namely non-paraxial approximation, attaining a balance between intensity and polarization grating is generally known as a prerequisite for faithful reconstruction. However, obtaining such balance point within polarization-sensitive material has long been known as a challenging job, due to its extremely strict exposure condition. In this paper, we report on a smart method with the well-designed reference and reading wave to faithfully reconstruct the signal wave at arbitrary exposure energy. Moreover, when the signal is circularly polarized, the diffraction efficiency can be precisely manipulated by changing the reading wave’s polarization state, which is favorable for optical storage and functional diffractive optical elements.

Modeling, Simulation, and Fabrication of Bi-directional Mode Division Multiplexing (BMDM) for Silicon-on-Insulator Platform

Omnia Nawwar, Hossam Shalaby, and Ramesh Pokharel

Doc ID: 309189 Received 16 Oct 2017; Accepted 28 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: A strip waveguide based bi-directional mode division multiplexer (BMDM) is proposed. A mathematical model has been proposed to analyze the performance and the results are simulated. The design concept of this device to (de)multiplex three modes simultaneously has been studied previously for slab waveguides; both mathematically using the perturbative mode-coupled theory and by simulation using 2D-FDTD Solutions. As slab waveguides are not suitable for extracting fabrication parameters for most silicon-on-insulator (SOI) applications, we apply the concept to a more practical device that involves strip waveguides rather than slab waveguides. Effective IndexMethod (EIM) has been used to develop the mathematical model and to get approximate forms for both the profiles and coupling coefficients. The return loss of different modes are taken into consideration to fully characterize the device performance. Simple formulas for both insertion and return losses of all multiplexing modes have been derived. In addition, full vectorial 3D-FDTD simulations are performed so as to validate our mathematical model. Different design parameters have been used to get numerical results of the proposed device. Our results reveal that the EIM has enough accuracy to characterize the performance of our device compared to that of the complex full vectorial simulation. In order to validate used model, the device hasbeen fabricated and tested. Good insertion losses and crosstalks for all modes has been obtained.

Single-shot dual-mode water-immersion microscopy platform for biological applications

José Ángel Picazo-Bueno, Dan Cojoc, federico issepon, Vicent Torre, and Vicente Mico

Doc ID: 300613 Received 22 Jun 2017; Accepted 28 Nov 2017; Posted 28 Nov 2017  View: PDF

Abstract: A single-shot water-immersion digital holographic microscope combined with broadband (white light) illumination mode is presented. This double imaging platform allows conventional incoherent visualization with phase holographic imaging of inspected samples. The holographic architecture is implemented at the image space (that is, after passing the microscope lens) thus reducing the sensitivity of the system to vibrations and/or thermal changes in comparison to regular interferometers. Because of the off-axis holographic recording principle, quantitative phase images of live biosamples can be recorded in a single camera snapshot at full-field geometry without any moving parts. And the use of water immersion imaging lenses maximizes the achievable resolution limit. This dual mode microscope platform is first calibrated using microbeads, then applied to the characterization of fixed cells (neuroblastoma, breast cancer and hippocampal neuronal cells) and finally validated for visualization of dynamic living cells (hippocampal neurons).

Fast occlusion processing for polygon-basedcomputer-generated hologram using slice-by-slicesilhouette method

Jung-Ping Liu and Heng-Kuang Liao

Doc ID: 302351 Received 12 Jul 2017; Accepted 27 Nov 2017; Posted 28 Nov 2017  View: PDF

Abstract: In polygon-based computer-generated hologram (CGH), the three-dimensional model is represented as a polygon,which consists of numerous small facets. Lighting effect, material texture and surface property can be included inthe polygonal model, which enables polygon-based CGH to realize high-fidelity three-dimensional (3D) display. Onthe other hand, the occlusion effect is an important depth cue for 3D display. In polygon-based CGH, however, theocclusion processing is a difficult and time-consuming work. In this paper, we proposed a simple and fast occlusionprocessing method, the slice-by-slice silhouette (S3) method, for generating the occlusion effect in polygon-basedCGH. In S3 method, the polygonal model is sliced into multiple thin segments. For each segment, a silhouette mask isgenerated and located at the backside of the segment. The incident light is first shaded by the mask andsuperimposes on the light emitted from the facets of the evaluated segment. By this way, every segment can beprocessed sequentially to get the resulting object light. Our experimental result demonstrates that S3 method cangenerate a high-definition hologram with qualified occlusion effect. The computing complexity of S3 method islower than that of previous method. In addition, S3 method can be parallelized easily, and thus can be furtherspeeded up by applying parallel computing framework, such as multi-core CPU or GPU.

Distortion-compensated multifocusing of ultrashort pulse beams using cascade optical system

Jun Amako and Hidetoshi Nakano

Doc ID: 308521 Received 05 Oct 2017; Accepted 27 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: We report a cascade optical system for multifocusing ultrashort pulse beams, particularly sub-50-fs pulses. System achromaticity is key to simultaneous compensation of the spatio-temporal pulse distortions. In this system, diffractive and refractive subsystems are optically coupled in cascade to correct chromatic aberrations, which are the primary cause of pulse distortion. We design a prototype system by applying achromatic conditions derived from an ABCD matrix analysis. The designed system is then evaluated using 20-fs pulses, by characterizing the transmitted pulses in terms of beam width and pulse duration; hence, the proposed distortion compensation scheme is validated. This pulse delivery system enables damage-free and high-throughput materials processing using ultrashort pulses.

Evaluation of the key design parameters of Liquidcrystal tunable lenses for Depth-from-Focus algorithm

Simon Emberger, Laurent Alacoque, Antoine Dupret, Nicolas Fraval, and Jean Louis de Bougrenet de la Tocnaye

Doc ID: 307282 Received 19 Sep 2017; Accepted 27 Nov 2017; Posted 01 Dec 2017  View: PDF

Abstract: Liquid crystal (LC) tunable lenses have been extensively studied and used in various applications (see for instance[1-3]), however, most of them have been evaluated regardless of their optical imaging quality, in particular,concerning their intrinsic diffuse scattering. In this paper, we investigate the impact of such impairments when LClenses are used as tunable elements in a depth from focus algorithm (DfF). We attempt to analyze these effects inorder to design LC lenses that mitigate their impact on the imaging quality. For this purpose, we designed variouslenses to evaluate several parameters such as optical, electrical, manufacturing, etc., according to theirimplementations in a near pixel DfF architecture [4].

Rotating of low-refractive-index microparticles withquasi-perfect optical vortex

Yansheng Liang, Ming Lei, Shaohui Yan, Manman Li, YaNan Cai, ZhaoJun Wang, Xianghua Yu, and Baoli Yao

Doc ID: 312304 Received 30 Oct 2017; Accepted 27 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Low-refractive-index microparticles, such as hollow microspheres, have shown great significance in some applications, suchas biomedical sensing and targeted drug delivery. However, optical trapping and manipulation of low-refractive-indexmicroparticles are challenging owing to the repelling force exerted by typical optical traps. In this paper, we demonstratedoptical trapping and rotating of large-sized low-refractive-index microparticles by using quasi-perfect optical vortex (quasi-POV) beams, which were generated by Fourier transform of high-order quasi-Bessel beams. Numerical simulation wascarried out to characterize the focusing property of the quasi-POV beams. The dynamics of low-refractive-indexmicroparticles in the quasi-POV with various topological charges was investigated in detail. To improve the trapping androtating performances of the vortex, a point trap was introduced at the center of the ring. Experimental results showed thatthe quasi-POV was preferable for manipulation of large-sized low-refractive-index microparticles, with its control of theparticle’s rotating velocity only dependent on the topological charge due to the unchanged orbital radius.

Design for a high birefringence photonic crystal fiberwith multimode and low-loss

Fengji Gui, Ping Jiang, Yang Huajun, Yan Qin, and Wei Caiyang

Doc ID: 308201 Received 03 Oct 2017; Accepted 25 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: In this work, a novel design of high birefringence photonic crystal fiber (HB-PCF) with multi-mode and lowconfinement loss is proposed. To achieve high birefringence, the core is designed as an elliptical region which isenclosed by twelve small holes. Based on this design, replacing the two circular holes at the top and bottom of thecore region with two elliptical holes can further improve the birefringence. At the wavelength of 1.55 μm, thebirefringence of the fundamental mode (LP01) and the second-order mode (LP11) are 1.70×10-2 and 1.85×10-2,respectively. Meanwhile the confinement losses maintain on orders of 10-5 dB/km (LP01) and 10-1 dB/km (LP11).After the effective refractive indices of two types of proposed HB-PCF are calculated by finite element method, thebirefringence, confinement loss, bending loss, dispersion and nonlinear coefficient are studied. These resultsreveal that the HB-PCF might be applied for polarization-maintaining and nonlinear optics.

Stability design of LED light source for trace constituent concentration measurement

Ling Ma, Fajie Duan, Jiajia Jiang, Xiao Fu, Tingting Huang, and Jingtao Chen

Doc ID: 309056 Received 19 Oct 2017; Accepted 25 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: Optical measurement is widely applied in determining the concentration of trace constituents in oilfield injection water. The performance of light source directly affects the accuracy of the whole optical measurement system. To guarantee the stability of the infrared light source and the ultraviolet light source, an infrared LED with the central wavelength of 860nm and an ultraviolet LED with the central wavelength of 365nm were chosen. Both LEDs were modulated to high frequency to shield the stray light. Through the analysis and comparison among the double-load current-source drive mode, single-load voltage-source drive mode and single-load current-source drive mode, we designed and theoretically deduced a closed-loop control system for the single-load constant-current-source driving LED. Experiment validated that this system could effectively eliminate the light intensity instability caused by the drift of ambient temperature and light emitting efficiency, and ensure the intensity stability of light source in the determination of trace constituents.

Experimental Investigation of Unidentified HeNe Lasers

Nasrullah Khan, Sam Goldwasser, Naeem Abas, Aun Haider, and Ali Kalair

Doc ID: 309730 Received 23 Oct 2017; Accepted 24 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: The Helium-Neon (HeNe) laser used to be a staple in every industrial or university lab having anything to do with photonics, as well as in numerous commercial products like barcode scanners. They are now less common, but still essential for many areas of research and education, and may turn up without any documentation. This paper describes an interesting experience of attempting to operate a Helium-Neon (HeNe) laser without any prior information about its input-output specifications. A HeNe tube was encapsulated in a plastic cover with a copper foil wrapped power supply jack attached to it. It was like an optoelectronic gadget without any mention of its operating instructions, wiring, or power requirements. This HeNe laser was investigated as a part of a research methods course case study. One week’s testing and investigation led us to conclude that the plasma tube was either defective due to mirror misalignment or internal contamination. As a result of this troubleshooting experience a well engineered investigation procedure was developed for testing HeNe lasers. A systematic approach helped to prioritize investigation of mirror alignment, mirror coating damage, possible debris inside the cavity, and power supply problems. General guidelines as well as this specific diagnostic experience can be very useful for laser technicians and engineers.

Spectroscopic study of a diffusion-bonded all sapphire cell for hot metal vapors

Naota Sekiguchi, Takumi Sato, Kiyoshi Ishikawa, and Atsushi Hatakeyama

Doc ID: 309852 Received 26 Oct 2017; Accepted 24 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Characteristics of a diffusion-bonded all-sapphire cell for optical experiments with hot metal vapors were investigated. The sapphire cell consisted of sapphire-crystal plates and a borosilicate-glass tube, which were bonded to each other by diffusion bonding without any binders or glues. The glass tube was attached to a vacuum manifold using the standard method applied in glass processing, filled with a small amount of Rb metal by chasing with a torch, and then sealed. The cell was baked at high temperatures and optical experiments were then performed using rubidium atoms at room temperature. The sapphire cell was found to be vacuum tight, at least up to 350ºC, and the sapphire walls remained clear over all temperatures. From the optical experiments, the generation of a background gas was observed after baking at 200ºC. The background gas pressure was low enough to avoid pressure broadening of absorption lines but high enough to cause velocity-changing collisions of Rb atoms. The generated gas decreased at higher temperatures, probably due to chemical reactions.

Large scale clinical validation of non-contact and continuous extraction of blood pressure via multi-point defocused photonic imaging

Mark Golberg, Joaquin Rivas, Sagi Polani, Yevgeny Beiderman, and Zeev Zalevsky

Doc ID: 307332 Received 18 Sep 2017; Accepted 24 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: Blood pressure measurement is usually being done either invasively by an intra-arterial catheter or noninvasively by a cuff based sphygmomanometer. While the invasive method is continuous and more accurate, it has the risk of infection, and generally is not comfortable for the patient. On the other hand, the cuff based measurement is safer but less reliable and infrequent. Thus, a reliable continuous noninvasive blood pressure measurement is highly desirable. In this work, we propose a remote optical system, based on temporal analysis of secondary reflected speckle patterns, for computing subject's pulse transit time (PTT). Afterwards, a model is proposed and clinically validated for converting the PTT value into systolic and diastolic blood pressure. A full statistical analysis is performed over a comparison to a reference device (SOMNOtouch™).

Doping concentration distribution in 2-signal LP modering-core erbium-doped fiber

Makoto Yamada, Daiki Nobuhira, Shota Miyagawa, Osanori Koyama, and Hirotaka Ono

Doc ID: 308964 Received 10 Oct 2017; Accepted 22 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: We simulated an improvement in fiber characteristics, specifically the differential modal gain (DMG) and the LP11mode wavelength dependent gain (WDG) characteristics. We defined the DMG as the gain difference between the CbandWDM signal channels of the LP01 and LP11 modes at the shortest wavelength, and WDG was the gain differencebetween the signal gain of the LP11 mode at the shortest and longest wavelengths, when the DMG of the LP01 modewas zero. We achieved this improvement by changing the erbium doping distribution in ring-core erbium-dopedfiber (RC-EDF), which has been attracting attention as an amplification medium for a 2-mode (LP01 and LP11 modes)erbium-doped fiber amplifier for mode-division multiplexed transmission. We applied an α-th power profile,trapezoid profile, and right and left triangular profiles to the RC-EDF. We found that the DMG value changed fromnegative to positive despite the value of the LP11 mode WDG being positive, and confirmed that the DMG could beadjusted by changing the distribution. We show level curve maps of the DMG, LP11 mode WDG, pump power andEDF length on the allowable 2-signal-mode area map for inner and outer radius combinations of the RC-EDF, andclarify that it is possible to realize a region that provides high efficiency amplification with a low DMG of < |0.1| dBand a low WDG of < 0.1 dB. Furthermore, we show that by varying the distribution of the erbium dopingconcentration we can greatly change the position of the region on the map of the allowable 2-signal-mode area.

Analysis of fluoroquinolones antibiotic residue infeed matrices using terahertz spectroscopy


Doc ID: 308833 Received 13 Oct 2017; Accepted 22 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: As antibiotic residue become more and more serious all over the world, rapid and effective detection method was needed to evaluatethe antibiotic residue in feed matrices to ensure food safety for consumers. In this study, three different kinds of fluoroquinolones (norfloxacin,enrofloxacin and ofloxacin) in feed matrices were analyzed using terahertz (THz) spectroscopy, respectively. Meanwhile, pure fluoroquinolonesand pure feed matrices were also measured in the same way. Then the absorption spectra of all the samples were extracted in transmissionmode. Pure norfloxacin has two absorption peaks at 0.825 THz and 1.187 THz and they still could be observed when mixing norfloxacin with feedmatrices. Also there was obvious and strong absorption peak for ofloxacin at 1.044 THz. However, no obvious absorption peak for enrofloxacinwas observed and only a weak absorption peak located at 0.8 THz. Then the different models were established with different chemometrics toidentify the fluoroquinolones in feed matrices and determined the fluoroquinolones content in the feed matrices. Least squares support vectormachines (PL-SVM), naive bayes (NB), mahalanobis distance and back propagation neural network (BPNN) were used to build the identificationmodel with Savitzky–Golay filter and standardized normal variate (SNV) pretreatments. The results show that the excellent classification modelwas acquired with the back propagation neural network (BPNN) combined with no pretreatment. The optimal classification accuracy was 80.56%in the testing set. After that, multiple linear regression and stepwise regression were used to establish the quantitative detection model fordifferent kinds of fluoroquinolones in feed matrices. The optimal correlation coefficients for norfloxacin, enrofloxacin and ofloxacin in theprediction set were obtained with multiple linear regression that combined absorption peaks with wavelengths selected by stepwise regression,which were 0.867, 0.828 and 0.964, respectively. Overall, this research explored the potential of identifying the fluoroquinolones in feed matricesusing THz spectroscopy without complex pretreatment process and then quantitatively detecting the fluoroquinolones content in feed matrices.The results demonstrate that THz spectra could be used to identify fluoroquinolones in feed matrices and also detect their content quantitatively,which has great significance for food safety industry

Spectral characteristics of coralline algae: a multi-instrumental approach, with emphasis on underwater hyperspectral imaging

Aksel Mogstad and Geir Johnsen

Doc ID: 307047 Received 13 Sep 2017; Accepted 21 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: Coralline algae constitute a cosmopolitan group of calcifying rhodophytes (red algae) that display characteristic optical fingerprints due to light absorption by specific light-harvesting pigments. The spectrally conspicuous nature of coralline algae makes them potential candidates for optical remote sensing surveys, and recently, a novel optical remote sensing technique has entered the scene of marine research: underwater hyperspectral imaging (UHI). The aim of the study was to characterize the spectral properties of different coralline algal species, and to assess the potential of UHI as a coralline algal identification and mapping tool. Four species of coralline algae were investigated: Corallina officinalis, Lithothamnion glaciale, Phymatolithon lenormandii, and Phymatolithon tenue. Important coralline algal pigments were identified using spectrophotometry and high-performance liquid chromatography (HPLC). Reflectance spectra of all species were obtained using both a spectrometer and UHI. Multivariate statistical analyses were performed on the reflectance data to identify spectral differences between species and instruments. In addition, supervised classification of coralline algae in UHI transects recorded both in vivo and in situ was carried out. R-phycoerythrin and chlorophyll a were found to be the most dominant coralline algal pigments. The analyzed species of coralline algae displayed highly similar reflectance spectra, and dips in reflectance corresponding to the absorbance peaks of R-phycoerythrin and chlorophyll a were identified in all spectra. Wavelengths corresponding to R-phycoerythrin light absorbance were the greatest contributors to interspecific spectral differences, but the investigated coralline algal species could not be spectrally distinguished with great accuracy. Optical signatures recorded using different instruments were comparable, but inter-instrumental spectral differences were found to be greater than interspecific differences. Supervised UHI classification was unable to accurately map different coralline algal species due to the similarity of the optical fingerprints, but as a group, coralline algae could easily be identified. In the future, large-scale UHI surveys of coralline algal habitats should be carried out using platforms such as remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs) to enhance our understanding of this widespread and ecologically important organism group.

Distribution law of dust concentration by imagetransmission in cement workshop

Jieping Wu, Guohui Li, Zhiwen Luo, Ming Zhu, and Xin Wu

Doc ID: 308040 Received 28 Sep 2017; Accepted 20 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: The traditional experimental method has a common disadvantage that it only can measure the dust concentrationof a few sampling points, resulting in a limitation of the further research about distribution law of dustconcentration in cement workshop. Aiming at revealing more visually and accurately the distribution law of dustconcentration, a Vision Based Measurement (VBM) system for dust concentration based on the image transmissionis constructed by utilizing an established dust simulation device in cement workshop. The measurement systemmeasured the dust concentration in the X-direction and Z-direction with a line-scanning-measuring mode and that ofend face XOZ in a face-scanning-measuring mode. Experimental results show that the distribution law of dustconcentration can be regarded as a first exponential function and then oscillating function relationship between thedust concentration and the distance from the dust source in X-direction, a parabolic function between the dustconcentration and the distance from the dust source in Z-direction, and a type of laminar or turbulence distribution inthe end face XOZ. The proposed VBM and the revealed law can provide a reference for the study of dust concentrationdistribution and dust control.

Fast and high quality light field acquisition using defocus modulation

Haichao Wang, Ni Chen, Shanshan Zheng, Jingdan Liu, and Guohai Situ

Doc ID: 301632 Received 05 Jul 2017; Accepted 20 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Light field reconstruction from images captured by focal plane sweeping, such as light field moment imaging~(LFMI) and light field reconstruction with back projection~(LFBP), can achieve high transverse resolution comparable to the modern camera sensor. This is impossible for the conventional microlens-array-based light field imaging systems. However, the acquisition of a series of focal plane sweeping images along the optical axis is time consuming and requires fine alignment. Besides, different focal plane based light field reconstruction techniques require images with different characteristics. To solve these problems, we present an efficient approach for fast light field acquisition with precise focal plane sweeping capture by defocus modulation rather than mechanical movement. Because of the controllable point spread function, we can capture images for light field reconstruction with both LFMI and LFBP

Deformation of a spherical lens caused by its own weight

Petr Pokorny, Filip Smejkal, and Antonin Miks

Doc ID: 305910 Received 29 Aug 2017; Accepted 19 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: The paper presents method for calculation of a surface deformation of a spherical lens or a plane-parallel plate caused by their own weight. Formulas for the case of support at the edge or for the inner radius support are presented. Since it is not possible to find an analytical solution with appropriate boundary conditions, the paper presents numerical methods enabling us to calculate an approximate solution. The mentioned deflection has enormous impact in the field of optical metrology of large lenses where it has to be taken into account during precise measurements.

Digital synthesis of optical interleaver based on solidmulti-mirror Fabry-Perot interferometer

Juan Zhang, Dong Hua, Yipeng Ding, and Yang Wang

Doc ID: 306435 Received 11 Sep 2017; Accepted 19 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: Starting from the matrix method introduced by Stadt, Muller and Bae, digital signal processing (DSP) techniquesare used to design multi-mirror Fabry-Perot (MMFP) interferometers. Solid MMFP interleavers with different filterorders and duty cycles are synthesized and optimized with this DSP method to achieve high isolation, wide flat-top,and large passband bandwidth ratio. Tolerance analysis of a typical structure is presented as well. This method isused to explain an interferometric measurement to show its utility in experimental practice. This method can alsobe applied to the design and analysis of other interference devices based on Fabry-Perot etalons.

Performance Improvement of GSSM prototype:Calibration, Added-on Damping Treatment andWarping Harness

qichang an, zhang jingxu, Fei Yang, Hongchao Zhao, and liang wang

Doc ID: 307736 Received 22 Sep 2017; Accepted 19 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: Giant Steerable Science Mirror (GSSM), the tertiary mirror of Thirty Meter Telescope (TMT), is designed to meet complicatedrequirements. Calibration, added-on Damping Treatment and Warping Harness will lower the cost to meet thosestrictrequirements. Laser Tracker and Sphere Mounted Retro-reflector (SMRs) were used to calibrate the GSSM prototype. Usingof un-uniform distribution SMRs will lower the systematic metrology error. Frequency Response Function (FRF) between inputsexcitation and dummy mirror responses is investigated to realize the design of Tuned Mass Damping (TMD), which will be addedon GSSMP as a damping treatment to improve settling time and tracing performance.Finally, we utilized the Warping Harness,combining Zernike mode and Bending mode, to relax the requirements of GSSM for low order mirror figure aberrations.

Closed-form Harmonic Contrast Control with Surface Impedance Coatings for Conductive Objects

Giuseppe Labate, Symon Podilchak, and Ladislau Matekovits

Doc ID: 310188 Received 03 Nov 2017; Accepted 18 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: The problem of suppressing the scattering from conductive objects is addressed in terms of harmonic contrast reduction. A unique compact closed-form solution for a surface impedance Zs(m,kr) is found in a straightforward manner and without any approximation as a function of the harmonic index m (scattering mode to suppress) and of the frequency regime kr (product of wavenumber k and radius r of the cloaked system) at any frequency regime.In the quasi-static limit, mantle cloaking is obtained as a particular case for kr << 1 and m=0. In addition, beyond quasi-static regime, impedance coatings for a selected dominant harmonic wave can be build with their proper dispersive behaviour, resulting in improved reduction levels and harmonic filtering capability.

Discrete plasmonic Talbot effect in single mode graphene ribbon arrays

Lei Wang, yonglei jia, and Zhichao Ji

Doc ID: 308179 Received 28 Sep 2017; Accepted 16 Nov 2017; Posted 17 Nov 2017  View: PDF

Abstract: Controllable manipulation of surface plasmon polaritons in discrete waveguide arrays is critical in plasmonic applications. In this paper, exploiting the coupled-mode theory with the tight-binding approximation, discrete plasmonic Talbot effect in the weak coupled single mode graphene ribbon arrays is investigated. The Talbot distance can be flexible modulated by changing parameters (i.e. the carrier doping or array periods) of the graphene ribbon arrays, and the significantly subwavelength Talbot distances (λ/13) are obtained. In the configuration, the coupled-mode theory with the tight-binding approximation is proved intensely efficient to describe the propagation of surface plasmon supermodes. Our analysis can thus open a new avenue for developing graphene-based imaging devices and pave a way for their potential applications.

Accurate shape measurement of focusing microstructures in Fourier Digital Holographic Microscopy

Marta Mikula, Tomasz Kozacki, Michal Jozwik, and Julianna Kostencka

Doc ID: 303086 Received 31 Jul 2017; Accepted 16 Nov 2017; Posted 16 Nov 2017  View: PDF

Abstract: This paper proposes a measurement method of focusing objects with high gradient shape of small and large radius of curvature. The measurements are carried out on a Fourier Digital Holographic Microscope with optimized illumination conditions maximizing the usage of the system numerical aperture. The obtained fringe patterns are the result of interference of deformed spherical object and spherical reference waves. The key elements of the method are the aberration compensation and calibration procedures. They provide accurate reconstruction of the object wave and determination of the focus position of the sample. The shape is calculated in two steps. First, the object wave is reconstructed at the plane of the object focus using single or multi-frame phase extraction algorithm and the specialized propagation method. The step includes also compensation of spherical aberration. In the second step, the sample shape is computed with Local Ray Approximation approach. The proposed method is experimentally validated with measurements of challenging, high gradient shapes (convex, concave) of different radiuses of curvature.

Standoff ultra-compact μ-Raman sensor for planetarysurface explorations

M. Nurul Abedin, Arthur Bradley, Anupam Misra, Yingxin Bai, Glenn Hines, and Shiv Sharma

Doc ID: 307774 Received 25 Sep 2017; Accepted 16 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: We report the development of an innovative Standoff Ultra-Compact micro-Raman (SUCR)instrument that would solve some of the limitations of traditional micro-Raman systems toprovide a superior instrument for future NASA missions. This active remote sensor system,based on a 532 nm laser and a miniature spectrometer, is capable of inspection and identificationof minerals, organics, and biogenic materials within several centimeters (2 to 20 cm) at a high 10micrometer resolution. The sensor system is based on inelastic (Raman) light scattering andLaser-Induced Fluorescence (LIF). We report on micro-Raman spectroscopy development anddemonstration of the standoff Raman measurements by acquiring Raman spectra in daylight at a10 cm target distance with a small line-shaped laser spot size of 17.3 micrometer (width) by 5millimeter (height).

High Speed Real Time Heterodyne Interferometry UsingSoftware Defined Radio

Lucas Riobo, Francisco Veiras, Martín González, Maria Teresa Garea, and Patricio Sorichetti

Doc ID: 305548 Received 24 Aug 2017; Accepted 16 Nov 2017; Posted 06 Dec 2017  View: PDF

Abstract: This paper describes the design and performance of a phase demodulation scheme based on SoftwareDefined Radio (SDR), applied in heterodyne interferometry. The phase retrieval is performed in real timeby means of a low cost SDR with a wideband optoelectronic front-end. Compared to other demodulationschemes, the system is quite simpler, versatile and of lower cost. The performance of the demodulator isdemonstrated by measuring the displacement per volt of a thin-film polymeric piezoelectric transducerbased on polyvinylidene fluoride for ultrasonic applications. We measured displacements between 3.5pm to 122 pm with 7% relative uncertainty, in the frequency range from 20 kHz to 1 MHz.

Small-mode-volume, channel-connected Fabry-Perotmicrocavities on a chip

Mohammad Bitarafan and Ray DeCorby

Doc ID: 304748 Received 14 Aug 2017; Accepted 15 Nov 2017; Posted 17 Nov 2017  View: PDF

Abstract: A monolithic thin-film buckling process was used to fabricate arrays of high-finesse ( 2 103) curvedmirrorFabry-Perot cavities on a silicon chip, with areal density 104 per square centimeter. The cavityshape matches the predictions of elastic buckling theory, with maximum curvature at the center where thefundamental mode resides. We describe cavities with mode volume < 1.5l3 for the fundamental spatialresonance. We also describe cavities connected to air-core channels. Preliminary light-coupling resultssuggest that these structures have potential to enable the side-coupling of gases, liquids, and pump, probeor trapping beams.

Noise suppression of micro-grating accelerometerbased on dual modulation method

Tianhang Zhang, huilan liu, Li Shuang Feng, Xiao Wang, and Yu Zhang

Doc ID: 297044 Received 30 May 2017; Accepted 15 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: The micro-grating accelerometer, as a representative Micro-optical Eletromechanical Systerm (MOEMS) accelerometer,is studied widely on account of the advantages of small size and high resolution performance. The extremeaccuracy of the micro-grating accelerometer is mainly restricted by the noise floor. In order to improve theperformance of the micro-grating accelerometer, a dual modulation method is proposed which combined withintensity modulation and phase modulation. The intensity modulation can move the signal to a high frequency, andthe light source noise is suppressed perfectly by combining phase modulation. The dual modulation method isverified by constructing the micro-grating accelerometer prototype. Based on the two conditions above, the impactof 1/f noise is diminished. By comparison, the fluctuation of the system at 0.01g (1g=9.8 m/s2) is reduced about 3 dBwhich is in line with expectations. The power spectral density image shows that the system noise floor reaches -50dB with a decrease of about 10 dB. We hope that the low noise micro-grating accelerometer will be used generally inthe future.

Optical diffraction tomography with fully and partiallycoherent illumination in high numerical aperturelabel-free microscopy

Juan Soto, Jose A. Rodrigo, and Tatiana Alieva

Doc ID: 307386 Received 18 Sep 2017; Accepted 15 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: Quantitative label-free imaging is an important tool for the study of living micro organisms which duringthe last decade has attracted wide attention from the optical community. Optical diffraction tomography(ODT) is probably the most relevant technique for quantitative label-free 3D imaging applied in widefieldmicroscopy in the visible range. The ODT is usually performed using spatially coherent light illuminationand specially designed holographic microscopes. Nevertheless, the ODT is also compatible withpartially coherent illumination and can be realized in conventional wide-field microscopes by applyingrefocusing techniques as it has been recently demonstrated. Here we compare these two ODT modalitiesunderlining their pros and cons and discussing the optical setups for their implementation. In particular,we pay special attention to a system which is compatible with conventional wide-field microscope andcan be used for both ODT modalities. It consists of two easily attachable modules: the first one for sampleillumination engineering based on DLP technology and another one for focus scanning by using anelectrically-driven tunable lens. This hardware allows for a programmable selection of the wavelengthand the illumination design, as well as it provides fast data acquisition. Its performance is experimentallydemonstrated in the case of ODT with partially coherent illumination providing speckle-free 3Dquantitative imaging.

Novel green optical dissolved oxygen sensor onbased chlorophyll-zinc complex extracted from theplant Brassica Oleracea L

Erandir Silva, Paulo Pinto, Jécol Chretien, João Miranda, Hilton Pinho, Átila Timbó, Wilton Fraga, José Menezes, Marcos Silva, and Glendo Guimarães

Doc ID: 302820 Received 21 Jul 2017; Accepted 13 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: In this study we present the development of a novel green and highsensitivity optical dissolved oxygen sensor for measuring dissolvedoxygen in water using spectrofluorimetry. For the development of thesensor element, an organometallic complex was synthesized from the‘chlorophyll A’ molecule, extracted from the plant Brassica OleraceaL.with zinc insertion (Zn+2) replacing the magnesium (Mg+2). In theinvestigation, we evaluated the fluorescence suppression of theorganometallic zinc complex for samples with different concentrationsof dissolved oxygen. The complex has shown two absorption regions,350-475 nm and 600-700 nm. We observed the fluorescencesuppression of the complex, when excited at 440 nm and analyzed at635 nm, using spinning oxygenation and air pump flow methods,respectively. The fluorescence suppression curves presented firstorder decay with good correlation, resulting in R2 = 0.98282 and R2 =0.83849 for the spinning and air pump flow methods, respectively. Inorder to validate the methodology, we developed a prototype of abench sensor. For the relation between the fluorescence intensity andoxygenation time, we obtained a ratio curve with R2 = 0.9809. Themethodology and prototype sensor developed in this work arepresented as a new optical method for the measurement of dissolvedoxygen.

A robust method to probe the topological charge of a Bessel beam by dynamic angular double slits

Jing Zhu, Pei Zhang, Dongxu Chen, Ruifeng Liu, Yingnan Zhou, Jinwen Wang, Hong Gao, and fuli li

Doc ID: 305839 Received 28 Aug 2017; Accepted 10 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: Precisely determining the topological charge (TC) of both integral Bessel beams(IBB) and fractional Besselbeams (FBB) is a key issue for their applications. However, most of the common methods could not probeboth the IBB and FBB precisely and robustly. In this paper we give a robust method to probe the topologicalcharge of a Bessel beam by dynamic angular double slits (ADS). We find that when a Bessel beam verticallyilluminates on a dynamic ADS, the information of the TC can be retrieved from its Fourier transform patternsnear the optical axis. Even though there is a small misalignment between the center of the beams and the ADS,the global variation tendency is still good enough to obtain the TC. Based on these properties, the dynamicADS device combining the method of fitting the experimental data can be used to measure the TC of any Bessellight beam precisely and robustly. The error is less than 2% without the misalign and is less than 6% with asmall misalign for our experimental data. This method paves a new way to measure the TC of vortex beams.

Nanoscale tilt measurement using a cyclic interferometer with polarization phase stepping and multiple reflections

Charles Joenathan, Tahereh Nadarishahab, Ashley Bernal, Avery Krovetz, VC Pretheesh Kumar, and Angarai Ganesan

Doc ID: 307449 Received 21 Sep 2017; Accepted 06 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: High accuracy tilt or roll angle measurement is required for a variety of engineering and scientific applications. A cyclic interferometer with multiple reflections has been developed to measure small tilt angles. To accomplish this task a novel and simple method, phase shift by polarization was developed. The results of these studies show that the multiple reflection cyclic interferometer can be used to measure object tilts in the order of 0.2 nano radians. We develop the theory for polarization phase step and show that accurate measurements can be made with the cyclic interferometer.

Phase retrieval based on transport of intensity anddigital holography

Wenjing Zhou, Xiaofei Guan, Fan Fan Lui, yu yingjie, Honbo Zhang, Ting-Chung Poon, and Partha Banerjee

Doc ID: 305549 Received 24 Aug 2017; Accepted 28 Oct 2017; Posted 29 Nov 2017  View: PDF

Abstract: We propose a technique in which intensity images are reconstructed from a digital hologram to provide inputs forthe transport-of-intensity equation for unwrapped phase recovery. By doing this, we avoid shifting of the sampleor the camera in the experiment, commonly employed while using the method of transport of intensity equationfor phase retrieval. Computer simulations as well as experimental results have been demonstrated to verify theeffectiveness of the proposed idea. The underlying numerical technique can also be viewed as an alternative toexisting phase unwrapping algorithms.

Numerical simulation and design of apodized diffractive optical element composed of open ring zones and pinholes

Tao Liu, Lingjie Wang, Jizhen Zhang, Qiang Fu, and Xin Zhang

Doc ID: 294893 Received 28 Apr 2017; Accepted 11 Oct 2017; Posted 28 Nov 2017  View: PDF

Abstract: In this letter the very essence of the relationship between open ring zones of Fresnel zone plat and the pinhole rings of photon sieve is fully investigated. Numerical simulation showed that the normalized diffraction field near the focal point of individual pinhole ring is the same as the circular open ring zone. It has also been proved that the maximum diffraction efficiency of an open ring zone is higher than that of the traditional pinhole ring. Meanwhile pinhole rings has more flexibility for the apodization filtering. Based on these key findings we propose the design theory of apodized diffractive optical element composed of open ring zones and pinholes. A design example has been designed to validate the theory. Compared with traditional apodized PS, it has been shown that the new apodized diffractive element has a 50.19% higher energy efficiency and the minimum pinhole size is enlarged by 30.77%.

Characterization of the reference wave in a compact digital holographic camera

Ian Park, Robert Middleton, Russell Coggrave, Pablo Ruiz, and Jeremy Coupland

Doc ID: 303484 Received 31 Jul 2017; Accepted 04 Oct 2017; Posted 05 Oct 2017  View: PDF

Abstract: A hologram is a recording of the interference between an unknown object wave and a coherent reference wave. Providing the object and reference waves are sufficiently separated in some region of space and the reference beam is known, a high-fidelity reconstruction of the object wave is possible. In traditional optical holography, high-quality reconstruction is achieved by careful re-illumination of the holographic plate with the exact same reference wave that was used at the recording stage. To reconstruct high-quality digital holograms the exact parameters of the reference wave must be known mathematically. This paper discusses a technique that obtains the mathematical parameters that characterize a strongly divergent reference wave that originates from a fiber source in a new compact digital holographic camera. This is a lens-less design that is similar in principle to a Fourier hologram, but because of the large numerical aperture, the usual paraxial approximations cannot be applied and the Fourier relationship is inexact. To characterize the reference wave, recordings of quasi-planar object waves are made at various angles of incidence using a Dammann grating. An optimization process is then used to find the reference wave that reconstructs a stigmatic image of the object wave regardless of the angle of incidence.

Effect of optical pumping on the dielectric properties of 0.6CaTiO3-0.4NdAlO3 ceramics in terahertz range

Dan Li, Chunya Luo, Yebin Xu, Jing Zhang, Liang Wu, Huaixing Wang, Songjie Shi, furi ling, and Jian-Quan Yao

Doc ID: 302779 Received 18 Jul 2017; Accepted 02 Oct 2017; Posted 29 Nov 2017  View: PDF

Abstract: The dielectric properties of 0.6CaTiO3-0.4NdAlO3 ceramics under external optical fields were investigated by terahertz time-domain spectroscopy in a frequency range of 0.2 THz to 1 THz at room temperature. It could be found that the variation of real part of complex permittivity is approximately 0.31 in the frequency range of 0.2 THz to 1 THz. However the imaginary part of dielectric constant does not change appreciably with external optical field. The micromechanism of these results was attributed to the an built-in electric field caused by the excited free carriers in the ceramics.

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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