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Low-loss polarization maintaining THz photonic crystal fiber with a triple-hole core

zhiqing wu, xiaoyan zhoux, Handing Xia, ZHAOHUA SHI, Huang Jin, XIaodong Jiang, and wu weidong

Doc ID: 283790 Received 29 Dec 2016; Accepted 17 Feb 2017; Posted 17 Feb 2017  View: PDF

Abstract: In this paper, we report a novel low-loss and polarization maintaining THz photonic crystal fiber (PCF) with a triple-hole unit inside the core. The properties of birefringence, effective material loss, confinement loss, bending loss, power fraction, dispersion and single-mode condition are analyzed in detail by using the finite element methods. Simulation results show that high birefringence at a level of 10−2 can be achieved by simply reducing the diameter of one air-hole of the triple-hole core. And low effective material loss down to 30% of its bulk material loss can be achieved in our interested band around 3 THz, due to the high core porosity of the designed triple-hole core. Moreover, this design dramatically facilitates the fabrication process, because of the typical hexagonal structure with all circular air-holes and avoiding the troublesome multiple sub-wavelength air-holes in the core area. The results reveal that this proposal has potential for efficient THz transmission and other functional applications.

A broadband terahertz metamaterial absorber based on Tantalum Nitride

Deng Guangsheng, Jun Yang, and Zhiping Yin

Doc ID: 284443 Received 10 Jan 2017; Accepted 16 Feb 2017; Posted 17 Feb 2017  View: PDF

Abstract: A broadband metamaterial absorber with a single-layer of Tantalum Nitride(Ta2N3) frequency selective surface printed on a foam substrate, is presented. The proposed design has been numerically examined at terahertz region. The results have shown that a wideband absorption with absorptivity greater than 90% was achieved in the frequency range 1.17–2.99 THz, and the relative absorption bandwidth was up to 112.97%, which is significantly better than previously reported results. Moreover, the absorber was independent on wave polarization, and a high absorption for a wide range of oblique incidence was achieved. The surface current distribution, the electric field distributions, and the power loss analyses were used to explain the physical mechanism of a wideband absorption. However, the Tantalum Nitride layer has an important role in the energy absorption. According to obtained results, the proposed absorber, which is compact and simple to design, has a potential application in evolving broadband terahertz absorbers and sensors.

25mJ, 5KHz, 3ns, Nd:YAG discrete path slab amplifier using hybrid resonator

yefei Mao, Hengli zhang, Jiahe Cui, Jiahua Yuan, Xianglong Hao, and Yi Jiang

Doc ID: 283975 Received 04 Jan 2017; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: We report what we believe to be high performance for an Nd:YAG discrete path slab amplifier configuration based on a hybrid resonator system. The amplifier is driven by a Q-switched 0.3mJ nanosecond oscillator that generates initial laser pulse at a repetition rate of 5 KHz and beam quality of M2<1.3. The input pulse first passes through a simple amplifier system, eventually resulting in an amplified laser output of 25mJ at the absorbed pump power of 878W. A corresponding optical-to-optical efficiency of 14.3% was obtained and the beam quality factors M2 in the unstable and stable direction were 1.7 and 1.5, respectively. No remarkable signs of ASE were observed.

Programmable light source based on echellogram of a supercontinuum laser

Ding Luo, Miro Taphanel, Thomas Längle, and Jürgen Beyerer

Doc ID: 285062 Received 18 Jan 2017; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Illumination system with tunable spectrum has been receiving increasing amount of attention due to its wide application and unique capability. This article proposes a programmable light source in the visible range based on the combination of a prism and an echelle grating. A supercontinuum laser is utilized as the primary source, whose echellogram is projected to a digital mirror device (DMD) for wavelength selection. Complete calibration procedure is developed to generate any target spectrum of choice. Experiments have shown that spectral peaks with FWHM of 1 nm can be easily generated and the wavelength tuning resolution can reach as small as 0.01 nm.

Univariate and multivariate analyses of rare earth elements by laser induced breakdown spectroscopy (LIBS)

Chet Bhatt, Fang Yueh, and Jagdish Singh

Doc ID: 283666 Received 29 Dec 2016; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Univariate and multivariate analyses of six rare earth elements [cerium (Ce), europium (Eu),gadolinium (Gd), neodymium (Nd), samarium (Sm), and yttrium (Y)] have been performed usingdata from laser induced breakdown spectroscopy (LIBS). Binary mixtures of oxide forms of each rareearth element in an Al2O3 matrix with their concentrations varying from 1% to 10% by weight inpowder form were used as working samples for univariate analysis. For multivariate analysis,complex mixtures of oxides of all these six rare earth elements and Al2O3 in powder form, where theconcentration of each element oxide was varied from 1% to 50% by weight one by one, were used torecord LIBS spectra. Optimum values of gate delay, gate width, and laser energy were used to getspectra from these samples and spectra were used to develop calibration models. The limits ofdetection (LOD's) for Ce, Eu, Gd, Nd, Sm, and Y were calculated to be 0.098, 0.052, 0.077, 0.047,0.250, and 0.036 % respectively from the calibration curves.

Holographic recording of the volume phase Fresnellenses in ZnSe semiconductor material

Sergei Krivoshlykov

Doc ID: 272469 Received 26 Jul 2016; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Holographic recording of the relief-free volume phase Fresnel lenses in polycrystalline ZnSe semiconductormaterial, which is transparent from the visible to long wave infrared wavelengths, is demonstrated. The roomtemperatureprocess of photo-modification, which changes refractive index of the semiconductor materialdramatically (Δn = 0.74 - 1.2 ) under illumination with low intensity light, is used for recording of the Fresnel lensemploying a computer-generated photomask in the proximity configuration. The thin-plate volume phasediffractive optics offers broader functionality and at least three-fold cost reduction due to saving of expensivematerial and labor. The possibility of recording the volume phase diffraction gratings also in the active Cr-dopedZnSe material opens door to fabrication of the mid-infrared lasers with narrowed and tunable emission spectrum.

Collimation testing using deflectometry in conjunction with WFT analysis

Shashi Prakash, Jitendra Dhanotia, and Vimal Bhatia

Doc ID: 273805 Received 15 Aug 2016; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: In this article, we demonstrate a simple automated procedure for detection of collimation of an optical beam by incorporating windowed Fourier fringe analysis technique into deflectometric set-up. The experimental arrangement consists of a deflectometry based system in which light from a laser is expanded and passed through a collimating lens. The transmitted light illuminates a coarse sinusoidal grating. The grating image is directly captured through charge couple device (CCD). Typical image patterns corresponding to ‘in-focus’, ‘at-focus’ and ‘out-focus’ positions of an optical beam are recorded. Depending on the position of collimating lens, the grating line spacing and the resulting phase of the emerging wavefront varies. Direct phase measurement using windowed Fourier transform (WFT) method has been used to obtain the slope map of the wavefront. The slope of the phase map depicts the diverging, collimated or converging nature of the optical beam. The positioning error of light beam collimation was approximately 1 µm. The experimental arrangement is simple, low cost, and compact. The technique is fully automatic and provides high resolution, high precision and good sensitivity.

Characterization of ultrashort pulses by time-frequency conversion and temporal magnification based on FWM at 1 μm

Zhi Qiao, Xue Pan, Xiaochao Wang, Tingrui Huang, Peng Zhang, Wei Fan, Li xuechun, and Zunqi Lin

Doc ID: 275758 Received 26 Sep 2016; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: In order to characterize ultrashort pulses in real-time at 1 µm wavelength, a temporal imaging structure based on the four-wave mixing effect in highly nonlinear fibers is implemented and analyzed both theoretically and experimentally. It is found that both time–frequency transfer and the temporal magnification process can be realized approximately in one structure. The pulse widths of the signal laser measured by the time–frequency transfer and the temporal magnification process are 3.2 ps and 3.1 ps, respectively, which are nearly the same and are in agreement with the result of the autocorrelator. The temporal magnification factor is 33 and the temporal resolution is 380 fs. The method based on the temporal magnification process is inherently real-time and single-shot, which makes it suitable for application in the measurement of high-power ultrashort pulses. The FWM time lens has future applications in the characterization of the single-shot high-power short laser.

Co-axis digital holography based on sinusoidal phase modulation using generalized lock-in detection

Yunlong ZHU, julien Vaillant, Manuel François, Guillaume Montay, and aurelien Bruyant

Doc ID: 281979 Received 01 Dec 2016; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Sinusoidal phase modulating (SPM) interferometers are used to precisely measure complex light fields with simple interferometric setups. Recently, a generalized lock-in technique was proposed for optimizing the signal extraction in phase-modulated interferometers. This article showed its applicability in digital holography as well as digital holographic interferometry. A compact home-made setup based on Michelson interferometer is used to observe scattering sample surface with a spatial resolution of 32 LP/mm; out-of-plane rotation can be measured with a theoretical resolution of 0.01°. The comparison between generalized lock-in detection and traditional SPM interferometer method is done theoretically and experimentally.

Deep Modulation of Second Harmonic Light by Wavelength Detuning of a Laser Diode

Mathias Christensen, Anders Hansen, Danny Noordegraaf, Ole Jensen, and Peter Skovgaard

Doc ID: 282021 Received 01 Dec 2016; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Power modulated visible lasers are interesting for a number of applications within areas such as laser displays and medical laser treatments. In this paper we present a system for modulating the second harmonic (SH) light generated by single-pass frequency doubling of a distributed feedback (DFB) master oscillator power amplifier (MOPA) laser diode with separate electrical contacts for the MO and the PA. A modulation depth in excess of 97% from 0.1 Hz to 10 kHz is demonstrated. This is done by wavelength tuning of the laser diode using only a 40 mA adjustment of the current through the MO. The bandwidth of the modulation is limited by the electronics. This method has the potential to decrease the size as well as cost of modulated visible lasers. The achievable optical powers will increase as DFB MOPAs are further developed.

The optimization and continuous fabrication of motheyenanostructure array on flexible PET substratetowards broadband antireflection

Chengpeng Zhang, Peiyun Yi, Linfa Peng, Xinmin Lai, and Jun Ni

Doc ID: 282526 Received 08 Dec 2016; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Reflection loss can cause harmful effects on the performance of optoelectronic devices, such as cell phones, notebooks,displays, solar cells and light-emitting-diode (LED) devices. In order to obtain broadband antireflection (AR) properties,many researchers have utilized surface texture techniques to produce antireflection subwavelength structures on theinterfaces. Among the antireflection subwavelength structures, the moth-eye nanostructure is one of the most promisingstructures with potential for commercialization in the near future. In this research, to obtain broadband AR performance,the optimization of moth-eye nanostructures was firstly carried out using the finite difference time domain (FDTD) methodwithin the spectral ranges of 400-800 nm, including the optimization of shape, height, pitch, and residual layer thickness. Inaddition, the continuous production of moth-eye nanostructure array upon a flexible PET substrate was demonstrated byusing roll-to-roll ultraviolet nanoimprint lithography (R2R UV-NIL) process and Anodic Aluminum Oxide (AAO) mold, whichprovided a solution for the cost-effective fabrication of moth-eye nanostructure array. The AR performance of moth-eyenanostructure array obtained by R2R UV-NIL process was also investigated experimentally and good consistence wasshown with the simulated results. This research can provide a beneficial direction for the optimization and cost-effectiveproduction of the moth-eye nanostructure array.

Strehl ratio and the amplitude-weighted generalized orthonormal Zernike-based polynomials

Cosmas Mafusire and Tjaart Krüger

Doc ID: 283322 Received 20 Dec 2016; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: The concept of orthonormal polynomials is revisited by developing a Zernike-based orthonormal set for anon-circular pupil that is transmitting an aberrated, non-uniform field. We refer to this pupil as a generalpupil. The process is achieved by using the QR form of the Gram-Schmidt procedure on Zernike circlepolynomials and is interpreted as a process of balancing each Zernike circle polynomial by adding those oflower order in the general pupil, a procedure which was performed in the past using classical aberrations.We demonstrate this concept numerically by comparing the representation of phase in a square-Gaussianpupil using the Zernike-Gauss square and Zernike circle polynomials. As expected, using the Strehl ratio, weshow that only specific lower order aberrations can be used to balance specific aberrations, e.g. tilt cannot beused to balance spherical aberration. In the process, we present a possible definition of the Maréchalcriterion for the analysis of tolerance of systems with apodized pupils.

Long range surface plasmon induced tunable ultra-low threshold optical bistability using graphene sheets at THz frequency

APARUPA KAR, Ardhendu Saha, and Nabamita Goswami

Doc ID: 283393 Received 21 Dec 2016; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: A proposal on optical bistability at ultra-low switching threshold and lower Fermi-level of graphene around 2 THz is implemented analytically through the proposed long range surface plasmon resonance configuration by employing local field enhancement effect owing to the excitation of graphene symmetric mode within the graphene sheets. Reported threshold intensity for the optical bistability till date is 1.6 kW/cm² within THz region and 1.83 MW/cm² at near-IR range. Whereas the proposed scheme explores the possibility of reducing this threshold down to 143.68 W/cm². This technique proffers potential applications in nano-illumination, optical memory and all-optical switching at ultra-low threshold.

Refractometric Detection of Liquids Using Suspended Core Microstructured Fiber and Tapered Optical Fiber: A Comparison of Methods

Tomas Martan, Tomas Nemecek, Matej Komanec, Redwan Ahmad, and Stanislav Zvanovec

Doc ID: 283430 Received 22 Dec 2016; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Detecting explosive, flammable or toxic industrial liquids reliably and accurately is a matter of civic responsibility which cannot be treated lightly. Suspended core microstructured optical fibers (SC MOFs) or tapered optical fibers (TOFs) were separately used as sensors of liquids without being compared to each other. The paper is focused on comparison of SC MOF and TOF of equal parameters for detection of selected liquids. This paper presents a validated method that incorporates SC MOF and TOF of small core (waist) diameter developed to operate by refractometric detection when considering liquids of defined refractive indices. The principle of detection is based on the overlap of an enhanced evanescent wave with a liquid analyte which either fills the cladding holes of the SC MOF, or surrounds the waist area of the TOF. Measurement results concerning SC MOF and TOF of similar parameters are compared. Optical power within the evanescent wave for both sensing structures and a variety of liquid analytes is also analyzed. Calculations to ascertain the limit of detection (LOD) for each sensor and the sensitivity (S) to refractive indices of liquid analytes in the range of 1.4269 to 1.4361 were performed at a wavelength of 1550 nm with the lowest refractive index step of 0.0007. Results affirming that S = 600.96 dB/RIU and LOD = 0.0733 RIU for the SC MOF and S = 1143.2 dB/RIU and LOD of 0.0026 RIU for the TOF sensor were achieved, clearly illustrating that TOF based sensors can reach close to two times greater sensitivity and 30-times higher limit of detection. The paper extends the comparison of the fiber sensors by discussing the potential applications of each.

The NOMAD spectrometer on the ExoMars Trace Gas Orbiter mission: part 2—design, manufacturing and testing of the ultraviolet and visible channel

Manish Patel, Philippe Antoine, Jon Mason, Mark Leese, Brijen Hathi, Adam Stevens, Daniel Dawson, Jason Gow, Timothy Ringrose, James Holmes, Stephen Lewis, Didier Beghuin, Philip Van Donink, Renaud Ligot, Jean-Luc Dewandel, Daohua Hu, Douglas Bates, Richard Cole, Rachel Drummond, Ian Thomas, Cédric Depiesse, Eddy Neefs, Eddy Equeter, Bojan Ristic, Sophie Berkenbosch, David Bolsee, Yannick Willame, Ann Vandaele, Stefan Lesschaeve, Lieve De Vos, Nico Van Vooren, Tanguy Thibert, Emmanuel Mazy, Julio Rodriguez-Gómez, Rafael Morales, Gian Paolo Candini, M. Carmen Pastor-Morales, Rosario Sanz, Beatriz Aparicio del Moral, José-Maria Jeronimo-Zafra, Juan-Manuel Gómez-López, Gustavo Alonso-Rodrigo, Isabel Pérez-Grande, Javier Cubas, Alejandro M. Gomez-Sanjuan, Fermin Navarro-Medina, Ali BENMOUSSA, Boris Giordanengo, SAMUEL GISSOT, Giancarlo Bellucci, and José-Juan Lopez-Moreno

Doc ID: 283497 Received 23 Dec 2016; Accepted 15 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: NOMAD is a spectrometer suite on board the ESA/Roscosmos ExoMars Trace Gas Orbiter (TGO) which launched in March 2016. NOMAD consists of two infrared channels and one ultraviolet and visible channel allowing the instrument to perform observations quasi constantly, by taking nadir measurements at the day- and night-side, and during solar occultations. Here, in part two of a linked study, we describe the design, manufacturing and testing of the ultraviolet and visible spectrometer channel called UVIS. We focus upon the optical design and working principle where two telescopes are coupled to a single grating spectrometer using a selector mechanism.

Secure fingerprint imaging based on structural and microangiographic optical coherence tomography

Xuan Liu, farzana zaki, Yahui Wang, qiongdan huang, Xin Mei, and Jianjun Wang

Doc ID: 282921 Received 15 Dec 2016; Accepted 15 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Optical coherence tomography (OCT) allows noncontact acquisition of fingerprint and hence is a highly promising technology in the field of biometrics. OCT can be used to acquire both structural and microangiographic images of fingerprint. Microangiographic OCT derives its contrast from the blood flow in the vasculature of viable skin tissue. Therefore, microangiographic fingerprint imaging is inherently immune to fake fingerprint attack and dual-modality (structural and microangiographic) OCT imaging of fingerprint enables more secured acquisition of biometric data. In this study, we performed OCT imaging study for fingerprint acquisition, and demonstrated the capability of dual-modality OCT imaging for the identification of fake fingerprint.

Characterization of micro structure through hybrid interference and phase determination in broadband light interferometry

yan tang, Yi Zhou, Jiangping Zhu, Qinyuan Deng, Yong yang, Lixin Zhao, and SONG HU

Doc ID: 279420 Received 25 Oct 2016; Accepted 15 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Broadband light interferometry which is a well-developed method for surface profiling has been applied with great success in past years. The conventional multi-wavelength interferometric surface profilers mostly utilize the light irradiance to locate the zero fringe order, but the serious problems are that the accuracy and stability can be negatively influenced by intensity fluctuations and external light disturbance. In this paper we discuss a hybrid technique combining light intensity and spectral modulation to determine zero optical path difference in which the light instability can be effectively suppressed. Additionally, the phase evaluation at each pixel will provide a high vertical resolution to obtain the characterization of micro structure. The hybrid-interference method will not only improve the sensitivity of measurement system, but also level up the robustness and stability. Both simulation and experiment on a micro-dome structure have been presented to verify the effectiveness. Furthermore, the proposed method is possibly promising to replace the previously intensity-based method especially in online topography measurement.

A High-precision Method Of Binocular Camera Calibration with distortion model

Weimin Li, SiYu Shan, and Hui Liu

Doc ID: 279548 Received 26 Oct 2016; Accepted 15 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: A high-precision camera calibration method for binocular stereo vision system based on multi-view template and alternative bundle adjustment is presented inthis paper. The proposed method could be achieved by taking several photos on special-designed calibration template that has diverse encoded points indifferent orientations. In this paper, the method utilize the existing algorithm used for monocular camera calibration to get the initialization, whichinvolves a camera model including radial lens distortion and tangential distortion. We do create reference coordinate system based on left camera coordinate,to optimize intrinsic parameters of left camera through alternative bundle adjustment to obtain optimal values. Then optimal intrinsic parameters of right camera can be obtained through alternative bundle adjustment when we create reference coordinate system based on right camera coordinate. And we do use all intrinsic parameters, which have been acquired, to optimize extrinsic parameters. Thus, the optimal lens distortion parameters, intrinsic and extrinsic parameters are obtained. Synthetic data as well as real data have been used to test the method. The simulation result shows that the maximum mean absolute relative calibration errors are about 3.5e-6 and 1.2e-6 for the focal lengths and the principal point respectively, under zero-mean Gaussian noise with 0.05 pixels standard deviation. And the real result shows that the reprojection error of our model is about 0.045 pixels with an average accuracy of 1.0e-6 over the intrinsic parameters. The proposed method is convenient, cost-efficient, high-precision and simple to be carried out.

A GPS-aided method for platform attitude determination based on target images

Teng Xu, Lijun Xu, Xiangrui Tian, and Xiaolu Li

Doc ID: 279921 Received 01 Nov 2016; Accepted 15 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Attitude measurement error is one of the main factors that deteriorate the imaging accuracy of laser scanning. Inview of the fact that the inertial navigation system (INS) with high accuracy is very costly, a low-cost but effectiveGPS-aided method based on the target images is proposed to measure the platform attitude angles in this paper.Based on the relationship between the attitude change of the platform and the displacement of two adjacentimages, the attitude change can be derived by the proposed method. To quantitatively evaluate the accuracy of theplatform attitude angles measured by the proposed method, an outdoor experiment was carried out incomparison with the INS-based method. The preliminary results demonstrated that the measurement accuracyusing the proposed method.

Investigation of deep-level defects in CuGaSe2 thin-film solar cells using photocapacitance methods

Xiaobo Hu, Juanjuan Xue, Jiao Tian, Guo-En Weng, and Shaoqiang Chen

Doc ID: 283835 Received 29 Dec 2016; Accepted 15 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Properties of deep-level defects in CuGaSe2 thin-film solar cells were investigated using photocapacitance methods. By measuring the transient photocapacitance spectroscopy, a deep-level defect centered at around 0.8 eV above the valence band and a defect band located around 1.54 eV above the valence band were determined. A configuration coordinate model was used to explain the thermal quenching effect of the two defects. By measuring the steady-state photocapacitance, a fast increase, followed by a slow increase, was observed in the photocapacitance transient when the sample was illuminated by light with a photon energy of 0.8 eV at low temperature. Upon being re-exposed by sub-bandgap light, an extra slow decrease in photocapacitance transient was observed. These observations were interpreted using a configuration coordinate model assuming two states for the 0.8 eV defect: a stable state D and its metastable state D* with a large lattice relaxation. The variation of the photocapacitance transients was attributed to the different optical transition processes of carriers between the two states of the 0.8 eV defect and the valence and conduction bands.

Speeding Up Image Quality Improvement in Random Phase-free Holograms using Ringing Artifact Characteristics

Yuki Nagahama, Tomoyoshi Shimobaba, Takashi Kakue, Nobuyuki Masuda, and Tomoyoshi Ito

Doc ID: 281822 Received 05 Dec 2016; Accepted 15 Feb 2017; Posted 15 Feb 2017  View: PDF

Abstract: A holographic projector utilizes holography techniques. However, there are several barriers to realizing holographic projections. One is deterioration of hologram image quality caused by speckle noise and ringing artifacts. The combination of the random phase-free method and the Gerchberg-Saxton (GS) algorithm has improved the image quality of holograms. However, the GS algorithm requires significant computation time. We propose faster methods for image quality improvement of random phase-free holograms using the characteristics of ringing artifacts.

Stress homogenization effect in multicore fiber optic bending sensors

Gustavo Capilla-Gonzalez, Daniel May-Arrioja, Daniel Lopez-Cortes, and Jose Guzman-Sepulveda

Doc ID: 281854 Received 15 Dec 2016; Accepted 15 Feb 2017; Posted 15 Feb 2017  View: PDF

Abstract: In this work we study the particular case of an optical fiber subjected to compression-bending load, the most common loading configuration for testing fiber optic bending sensors. Our analysis is based on the foundations of column theory and reveals a progressive stress homogenization across the optical fiber with increasing bending. This effect is general to any optical fiber subjected to this load configuration and it is of particular interest for structures with multiple cores since the state of stress experienced by each core can significantly differ even for a condition of constant load. The approach outlined here captures relevant features observed in experiments with multicore fiber optic bending sensors. Also, this approach can be incorporated into coupled mode theory for assessing the performance of spectrally operated fiber sensors based on multicore coupled structures under realistic conditions commonly encountered in the experiments and without the need of performing computationally expensive simulations. The progressive stress homogenization, as well as the regime of homogeneous stress dominated by the bending contribution, is experimentally demonstrated using a multicore optical fiber with three coupled cores. Our observations are similar to those reported in recent experiments using other multicore fibers with different amount of cores.

The influence of two-photon absorption on the dynamic behaviors of microring resonator

Haowen Chen, Qiliang Li, Jie Xu, Miao Hu, Ran Zeng, xuefang zhou, and Shuqin li

Doc ID: 283907 Received 04 Jan 2017; Accepted 14 Feb 2017; Posted 15 Feb 2017  View: PDF

Abstract: In this paper, we have investigated the influence of two-photon absorption (TPA) on the dynamic behaviors of all-pass andadd-drop microring resonators by using two iterative methods and linear stability analysis method. While incident field isabove a certain value, the TPA coefficient has larger influence on the steady state for all-pass and add-drop microringresonators. We use the linear stability analysis method to analyze the stability of the steady state solutions, and obtainstability conditions. Results obtained have shown that the change of TPA coefficient will lead to different dynamicbehaviors; in addition, while TPA coefficient is small and the change of it is slight, the dynamic behaviors of the systemswon’t change much for most region. Lastly, we observe the period windows and route from chaotic to period-N in someoriginal chaotic region due to the fluctuation of TPA coefficient.

A simple, picojoule-sensitive ultraviolet autocorrelator based on two-photon conductivity in sapphire

Kenneth Leedle, Karel Urbanek, and Robert Byer

Doc ID: 283265 Received 20 Dec 2016; Accepted 14 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: We present a simple autocorrelator for ultraviolet pulses based on two-photon conductivity in a bench-top fabricatable sapphire sensor. We perform measurements on femtosecond 226 - 278 nm ultraviolet pulses from the third and fourth harmonics of a standard 76 MHz titanium sapphire oscillator and picosecond 266 nm pulses from the fourth harmonic of a 1064 nm 50 MHz neodymium vanadate oscillator. Our device is sensitive to 2.6 pJ ultraviolet pulses with peak powers below 20 W. These results represent the lowest measured autocorrelation peak powers by over one order of magnitude for a system with no reference pulse in the deep ultraviolet ( < 300 nm). The autocorrelator can potentially support UV pulse lengths from 50 fs – 10's of picoseconds.

ICL-based optical transfer standard for atmospheric CO measurements

Javis Nwaboh, Zhechao Qu, olav werhahn, and Volker Ebert

Doc ID: 280951 Received 16 Nov 2016; Accepted 14 Feb 2017; Posted 15 Feb 2017  View: PDF

Abstract: We report an interband cascade laser (ICL)- absorption spectrometer for absolute, calibration free, atmospheric COamount fraction measurements, addressing direct traceability of the results. The system combines first principlesdirect tunable diode laser absorption spectroscopy (dTDLAS) with a metrological validation. Using a multi path cellwith 76 m path length, our detection limit is 0.5 nmol/mol at Δt = 14s. The system is highly linear (slope:0.999±0.008) in the amount fraction range of 0.1 μmol/mol to 1000 μmol/mol and thus interesting for industrialas well as environmental applications. The sensor repeatability at 300 nmol/mol is 0.06 nmol/mol (with Δt = 10minutes). The sensors absolute response is in excellent agreement with the gravimetric values of a set of primarygas standards used to test the sensor accuracy. The relative expanded uncertainty (k =2) of the measured COamount fraction is 2.8 %. Due to this performance and the calibration free approach, the spectrometer maybe usedas an optical transfer standard (OTS) if gas standards are for whatever reason not available or applicabale, e.g. forairborne instruments. As our dTDLAS approach has shown previously for the case of H2O detection (Buchholz et alAppl. Phys. B 116, pp. 883–899, 2014) with an excellent stability and accuracy even when compared to primarystandards, we deduce that the ICL spectrometer (after its adaption to field conditions, similar to our H2Ospectrometers) has a good potential to meet the 2 nmol/mol compatibility goal stated by WMO for atmospheric COmeasurements, and serve as an optical transfer standard (OTS), which does not need frequent calibrations usingreference gases.

A Novel Laser Stripe Extraction Method in Industrial Environments Utilizing Self-adaptive Convolution Technique

Xiao-Qia Yin, Wei Tao, Yi-Yang Feng, Qiang Gao, Qiao-Zhi He, and Hui Zhao

Doc ID: 281702 Received 28 Nov 2016; Accepted 14 Feb 2017; Posted 15 Feb 2017  View: PDF

Abstract: Line-structured laser scanner is widely applied for 3D reconstruction in industrial environments withubiquitous various luminance, complicated background, diverse objects and instable lasers. Theseelements will show up as noise in the obtained laser stripe images. Therefore, the basic and keypoint for line-structured laser scanner is to accurately extract the laser stripe from noise. This paperproposes an effective laser stripe extraction procedure with two steps. Firstly, a novel laser stripe centerextraction method based on the geometry information and correlation in the laser stripe, is designed tosignificantly eliminate noise and accurately extract the laser stripe centers. Besides, the robustness, speedand accuracy of this method are respectively analyzed in detail. Secondly, piecewise fitting is adopted toacquire a smooth and continuous laser stripe centerline. In order to select the optimal fitting method, thecharacteristics of two spline methods, Akima spline and cubic Hermite spline, are deeply analyzed andcompared. Finally, an experiment is carried out by using a rough metal step and a line-structured laserscanning system. The experiment results demonstrate that the proposed SACM method can significantlyeliminate noise in industrial environments. In addition, cubic Hermite spline is a better choice for 3Dreconstruction, rather than Akima spline.

Analysis of fiber optic gyroscope vibration error based on improved local mean decomposition and kernel principal component analysis

Rui Song and xiyuan chen

Doc ID: 279745 Received 28 Oct 2016; Accepted 14 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: Fiber Optic Gyroscope (FOG), as one kind of all solid-state rotation sensors and has been widely used in navigation and position applications. However, due to the elastic-optic effect of fiber which will introduce non-negligible error in the output of FOG under vibration and shock environment. To overcome the limitation of mechanism structure improvement methods and the traditional nonlinear analysis approaches, a hybrid algorithm of optimized local mean decomposition-kernel principal component analysis method (OLMD-KPCA) is proposed in this paper. The vibration signal features of higher frequency components are analyzed by OLMD and the energy of which are calculated to take shape as the input vector of KPCA. In addition, the output data of three axis gyroscopes in an inertial measurement unit (IMU) under vibration experiment are used to validate the effectiveness and generalization ability of the proposed approach. Experimental results demonstrate, comparing with the wavelet transform (WT), LMD-KPCA, the vibration noise in FOG output are greatly reduced. Besides, the Allan variance analysis results indicate one order magnitude increasement of the error coefficients could be achieved by OLMD-KPCA, and the stability is proved by another two sets of data under different vibration conditions.

Hybrid Generation and Analysis of Vector Vortexbeams

Sandra Mamani, Ethan Bendau, Jeff Secor, Solyman Ashrafi, Jiufen Tu, and Robert Alfano

Doc ID: 280970 Received 18 Nov 2016; Accepted 14 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: A method is described for generating optical vector vortex beams carrying superpositions of orbital angularmomentum states by using a tandem application of a spatial light modulator with a vortex retarder.The vortex component has a spatially inhomogeneous phase-front which can carry orbital angular momentum,and the vector nature is a spatially inhomogeneous state of polarization in the laser beam profile.The vector vortex beams are characterized experimentally by imaging the beam at points across the focalplane in an astigmatic system using a tilted lens. Mathematical analysis of the Gouy phase shows goodagreement with the phase structure obtained in the experimental images. The polarization structure ofthe vector beam as well as the orbital angular momentum of the vortex beam are shown to be preserved.

Modelling of Light Interaction with Exoskeletons of Scarab Beetles

Sergiy Valyukh and Kenneth Jarrendahl

Doc ID: 281241 Received 21 Nov 2016; Accepted 14 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: Some beetles of the family Scarabaeidae produce brilliant metallic-looking colors by their pure dielectric exoskeletons and reflect light with high degree of circular polarization. In the present work, we discuss three models for simultaneously describing scattering, spectral and polarization characteristics of scarab beetles. Each model consists of three slabs: an outer thin epicuticle, an exocuticle having helicoidal structure and a thick uniform slightly absorbing endocuticle. Scattering features are defined by rough interfaces of the epicuticle and/or non-uniformities of the exocuticle. As an example, a slightly modified model of an earlier study of Chrysina aurata is considered. The modification is aimed at including surface and volume non-uniformities that affect not only spectral and polarization properties but also scattering. Another example of using the proposed models is based on the analysis of image formations of a specimen of the species Mimela chinensis, which was studied in a polarizing microscope at different magnifications. The results show that the proposed models can be applied for explanation of light interaction with the exoskeletons of scarab beetles.

Calibration of a paracatadioptric camera by projection imaging of a single sphere

Yue Zhao and Yuanzhen Li

Doc ID: 281514 Received 24 Nov 2016; Accepted 14 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: This paper introduces an omnidirectional vision system calibration method that uses the central catadioptric projection properties of a single sphere. A central catadioptric camera with a single effective viewpoint images a single sphere as a closed conic. The intrinsic parameters of the camera can be obtained based on the imaged circular points and orthogonal vanishing points. The feasibility and validity of three algorithms were demonstrated through simulations and experiments with real data.

Scalable process for mitigation of laser-damaged potassium dihydrogen phosphate crystal optic surfaces with removal of damaged antireflective coating

Selim Elhadj, William Steele, Diana VanBlarcom, Ruth Hawley, Kathleen Schaffers, and Paul Geraghty

Doc ID: 281781 Received 29 Nov 2016; Accepted 14 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: We investigate an approach for the recycling of laser damaged large aperture deuterated potassium dihydrogen phosphate (DKDP) crystals used for optical switching and for frequency conversion in megajoule-class high power laser systems. The approach consists of micro-machining the surface laser damage sites (mitigation), combined with multiple soaks and ultrasonication steps in coating solvent to remove, synergistically, both the highly adherent machining debris and the laser damage affected antireflection coating. We identify features of the laser damage affected coating, such as the “solvent persistent coating” and the “burned-in” coating, that are difficult to remove by conventional approaches without damaging the surface. We also provide a solution to the erosion problem identified in this work when colloidal coatings are processed during ultrasonication. Finally, we provide a proof of principle of the approach by testing the full process that includes laser damage mitigation of DKDP test parts, coat stripping, re-application of a new antireflective coat, and laser damage test demonstrating performance up to at least 12 J/cm2 at UV wavelengths, well above current requirements. This approach ultimately provides a potential path to a scalable recycling loop for the management of optics in large, high power laser systems that can reduce cost, and extend lifetime of highly valuable and difficult to grow large DKDP crystals.

Goos-Hänchen shifts due to spin-orbit coupling in the carbon-nanotube quantum dot nanostructures

seyyed Hossein Asadpour

Doc ID: 282270 Received 07 Dec 2016; Accepted 14 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: The properties of Goos-Hänchen (GH) shifts for transmitted and reflected light pulses in a cavity with an intracavity medium consists of carbon nanotube quantum dot nanostructure are discussed theoretically by using the stationary phase theory. Our findings show that due to presence of spin-orbit coupling, the maximum negative and positive shifts can be realized by modifying the absorption and dispersion properties of the intracavity medium. Moreover, the effect of transverse magnetic field are also considered as a new parameter for controlling the GH shifts in reflected and transmitted light beams. We hope that our proposed structure suitable for the future all-optical systems devices based on carbon-nanotube quantum dot nanostructure.

Enhanced Light Absorption in Perpendicular Elliptical Nanocone Array for Solar Cells

Yonggang Wu, Xuefei Qin, Zihuan Xia, Jian Zhou, and Zongyi Zhang

Doc ID: 282575 Received 13 Dec 2016; Accepted 14 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: Silicon nanowire-based arrays have demonstrated superior light trapping properties and great potentials for next-generation photovoltaics. In this paper, we propose a perpendicular elliptical nanocone (PENC) array solar cell, which introduces an asymmetry in the direction parallel to the array surface in addition to the asymmetry in the direction normal to the array surface that has been implemented in the circular nanocone (CNC) array. The PENC array displays more and higher resonant absorption peaks in the long wavelength compared to the CNC array. The newly exhibiting absorption peaks are found to be derived from periodical Bloch modes by the band-folding of the PENC array and cavity modes introduced by the asymmetry of the elliptical nanocone. The ultimate efficiency of the optimal PENC array is 24.3%, which is 17.4% higher than that of the optimal CNC one with the same nanocone height, and 59.1% higher than that of the flat counterpart coated with a 70 nm zinc oxide anti-reflection film. When the nanocone height is between 0.3 and 5.0 μm and the incident angle between 0 and 65°, the PENC array demonstrates better light trapping property compared with the CNC ones.

Silicon three-dimensional structures fabricated by femtosecond laser modification with dry etching

Qi-Dai Chen, Xue-Qing Liu, Lei Yu, and Zhuo-Chen Ma

Doc ID: 282887 Received 15 Dec 2016; Accepted 13 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: In this paper, a maskless, high efficiency and flexible technology is developed to fabricate 3D microstructures on the silicon wafer, which is based on the combination of femtosecond laser modification and subsequent dry etching. The silicon atoms in 2D patterned areas were insufficiently oxidized after femtosecond laser irradiation. Complex 3D structures can be fabricated on silicon wafer after etching, such as micro gear, comb drive actuator and micro cantilever applied in MEMS and micro Fresnel zone plate applied in micro optics. What’s more, surface roughness of laser structured wafer can be improved with increasing etching time in the dry etching process. This technology shows its unique capacity to fabricate various 3D microstructures for applications in MEMS and micro optics.

Mid-infrared transmitter and receiver modules forfree-space optical communication

Qiang Hao, Guoshen Zhu, Song Yong, Kangwen Yang, Tao Duan, Xiaoping Xie, Kun Huang, and Heping Zeng

Doc ID: 279184 Received 20 Oct 2016; Accepted 13 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: We report on the experimental implementation of single-frequency fiber-laser pumped mid-infrared (mid-IR)transmitter and receiver modules for free-space communications. These modules enable frequency up- and downconversionbetween the 1550-nm telecom wavelength and the mid-IR, thus providing essential free–spacetransmission links with mid-IR single frequency laser in the 3.6 μm region. Specifically, based on differencefrequency generation (DFG) in MgO-doped periodically poled LiNbO3 (MgO:PPLN), the mid-IR transmitter produces9.3-mW power at 3594 nm with 5-W pump power at 1083 nm (<10 kHz linewidth) and 3-W signal power at 1550nm (<10 kHz linewidth), and the mid-IR receiver reproduces 12-μW power at 1550 nm with 4.7-W pump power at1083 nm and 5-mW laser at 3594 nm. The whole modules are integrated into portable and compact devices byincorporating single-frequency fiber lasers, fiber amplifiers, DFG units, and related electronic circuits. In addition,the uses of all polarization-maintaining (PM) fiber configuration and well-controlled heat dissipation make themid-IR transmitter and receiver exhibit a long-term stability.

Wavefront correction performed by a low-costdeformable mirror group in a small-aperture-beamfiber laser

Chenlu Zhou, Lei Huang, Xingkun Ma, Meng Yan, and Junbiao Fan

Doc ID: 281889 Received 30 Nov 2016; Accepted 13 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: A low-cost deformable mirror (DM) group for wavefront correction in small-aperture-beam fiber laser is reportedin this paper. The DM group consists of 9 single-actuator DMs and could act as a “virtual” 9-actuator DM arranged ina 3×3 array. The equivalent distance between two adjacent actuators could reach as small as 3mm, which can leadto a relatively high lateral resolution. Reflection mirrors in the DM group can be individually polished and highdamage-threshold coated. The unique manufacture flexibility will ensure the particularly low cost of the DM group.In this paper, detailed configuration of the DM group and its application in small-aperture-beam fiber laser arepresented. Theoretic simulations and experimental results successfully demonstrate its capability in wavefrontaberration correction for a small-aperture-beam fiber laser.

Error compensation in a pointing system based on Risley prisms

Manuel Salvador Bravo Medina, Marija Strojnik, Guillermo García-Torales, Hector Torres-Ortega, Ruben Marmolejo, Anuar Beltran, and Jorge Flores

Doc ID: 283634 Received 26 Dec 2016; Accepted 13 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: Risley prism are widely used as beam pointing in several optical systems. The exact solution for its inverse problem do not exist. However, the errors by misalignment are usually greater than the approximation errors. We present a new method to compensate alignment errors in pointing systems based on Risley prisms. The prism model that we used is based on paraxial approximation with an additional vector to compensate typical alignment errors. Simulated and experimental results show that the improvement in pointing accuracy is achievable even in comparison with exact ray tracing methods.

Compact and field portable 3D printed shearing digital holographic microscope for automated cell identification

SIDDHARTH RAWAT, Satoru Komatsu, Adam Markman, Arun Anand, and Bahram Javidi

Doc ID: 278544 Received 12 Oct 2016; Accepted 12 Feb 2017; Posted 13 Feb 2017  View: PDF

Abstract: We propose a low-cost, compact and field portable 3D printed holographic microscope for automated cell identification based on a common path shearing interferometer setup. Once a hologram is captured from the portable setup, a 3D reconstructed height profile of the cell is created. We extract several morphological cell features from the reconstructed 3D height profiles including mean physical cell thickness, coefficient of variation, cell’s optical volume (OV), projected area of cell (PA), ratio of PA to OV, cell thickness kurtosis, cell thickness skewness and cell’s dry mass for cell identification using the random forest (RF) classifier. The 3D printed prototype can serve as a low-cost alternative for the developing world where accesses to the laboratory facilities for disease diagnosis are limited. Additionally, a cell-phone sensor is also used to capture the digital holograms. This allows the user to send the acquired holograms over the internet to a computational device located remotely for cell identification and classification (analysis). The 3D printed system presented in this paper can be used as a low cost stable field portable digital holographic microscope as well as an automated cell identification system. To the best of our knowledge, this is the first report of automatic cell identification using a low-cost 3D printed digital holographic microscopy setup based on common path shearing interferometry.

Engineering poly-shell spherical microcapsulesfor optimal localized light absorption

Yuri Geints, Alexander Zemlyanov, and Ekaterina Panina

Doc ID: 281726 Received 28 Nov 2016; Accepted 12 Feb 2017; Posted 13 Feb 2017  View: PDF

Abstract: Optical radiation absorption in a poly-layer spherical microparticle simulating an inorganic/organic poly-shellabsorbing microcapsule is considered. With the aim of the finite-difference time-domain technique, the spatialdistribution of the absorbed light power in microcapsules of various sizes and internal structure is numericallycalculated. For the purpose of light absorption enhancement, we have engineered the optimal structure of acapsule consisting of a strong-refracting transparent outer coating and an absorbing layer which covers a liquidcore. Proposed microcapsule prototype provides for manifold increase in the absorbed light power density incomparison with usual single-layer absorbing capsule. We show that for light wavelengths-scaled microcapsules itis optimal to use a material with the refractive index larger than two as an outer shell, for example, titaniumdioxide (TiO2). The highest values of the absorbed power density can be obtained in microcapsules with absorbingshell thickness of about tenth of laser wavelength.

Benchmark evaluation of inversion algorithms for tomographic absorption spectroscopy

Weiwei Cai and Tao Yu

Doc ID: 282609 Received 20 Dec 2016; Accepted 12 Feb 2017; Posted 13 Feb 2017  View: PDF

Abstract: Tomographic absorption spectroscopy (TAS) is experiencing a surge of interest due to recent progress in laser technology and advanced imaging concepts such as nonlinear tomography and compressed sensing. Nevertheless, even though numerous algorithms have been adapted from other tomographic areas such as medical imaging and engineering process control, and applied in TAS applications, systematic comparison between those methods has not be investigated. In this work, we aim to test major inversion algorithms on both the so-called rank-deficient (RD) and discrete ill-posed (DIP) problems. Comparative studies were performed on extensive cases and the results for three representative phantoms are reported here. Other important topics such as determination of control parameters and the semi-convergent behavior of iterative methods have also been studied. According to our study, Landweber outperformed other methods for two RD cases and is slightly inferior to maximum likelihood expectation maximization (MLEM) algorithm for the third one. It has also been found that Landweber and MLEM feature better immunity to semi-convergence than the others; however, since MLEM is sensitive to initial guess, it is less robust than Landweber. On the other hand, truncated singular value decomposition (TSVD) method is recommended for DIP problems due to its superior performance as it can effectively suppress detrimental effects from noise, which will be amplified during the inversion procedure. It should be emphasized that even though this study was conducted under the context of TAS, we expect it to provide useful insights for other tomographic modalities.

Three-color vibrational CARS thermometry of fuel-rich ethylene/air flames using a KGd(WO4)2 Raman-active crystal as a source of narrowband probe radiation

Christian Meißner, Johannes Tröger, Dimitrii Kozlov, Frank Beyrau, and Thomas Seeger

Doc ID: 280967 Received 16 Nov 2016; Accepted 11 Feb 2017; Posted 13 Feb 2017  View: PDF

Abstract: Three-color broadband vibrational CARS temperature measurements were accomplished in laminar fuel-rich sooting ethylene/air flames. Stimulated Raman scattering (SRS) of a picosecond pump laser pulse in a Raman-active KGd(WO4)2 crystal was employed as a source of narrowband probe radiation. In the three-color CARS experiment this wavelength-shifted radiation enables N2-based vibrational CARS temperature measurements in sooting flames free of the signal interference with the absorption/emission bands of the flame intermediate radicals C2. Spatial temperature profiles for different fuel-rich atmospheric pressure ethylene/air flames are presented in comparison with the results of two-color broadband vibrational and dual broadband pure rotational CARS temperature measurements. The comparison shows the suitability of the three-color CARS measurement technique employing the KGd(WO4)2 crystal for accurate, C2-interference-free, temperature measurements in sooting flames.

Stent Optical Inspection System calibration and performance

Carlos Bermúdez, Ferran Laguarta, Cristina Cadevall, Aitor Matilla, Sergi Ibañez, and Roger Artigas

Doc ID: 278329 Received 14 Oct 2016; Accepted 11 Feb 2017; Posted 13 Feb 2017  View: PDF

Abstract: Implantable medical devices, such as stents, have to be inspected 100% so no defective one is implanted into a human body. In this paper, a novel optical stent inspection system is presented. By the combination of a high numerical aperture microscope, a triple illumination system, a rotational stage, and a CMOS camera, unrolled sections of the outer and inner surfaces of the stent are obtained with high resolution at high speed with a line-scan approach. In this paper, a comparison between the conventional microscope image formation and this new approach is shown. A calibration process, and the investigation of the error sources that lead to inaccuracies of the critical dimensions measurements are presented.

BRDF-dependent accuracy of array projection-based 3D sensors

Stefan Heist, Peter kuehmstedt, Andreas Tünnermann, and Gunther Notni

Doc ID: 275435 Received 07 Sep 2016; Accepted 10 Feb 2017; Posted 13 Feb 2017  View: PDF

Abstract: In order to perform high-speed three-dimensional (3D) shape measurements with structured light systems, high-speed projectors are required. One possibility is an array projector which allows pattern projection at several 10 kHz by switching on and off the LEDs of various slide projectors. The different projection centers require a separate analysis, as the intensity received by the cameras depends on the projection direction and the object's bidirectional reflectance distribution function (BRDF). In this contribution, we investigate the BRDF-dependent errors of array projection-based 3D sensors and propose an error compensation process.

Passive Q-switching of an Erbium:glass laser with Co:Mg(Al,Ga)2O4-based glass-ceramics

Vladimir Vitkin, Pavel Loiko, Olga Dymshits, Alexander Zhilin, Irina Alekseeva, Dinara Sabitova, Anton Polishchuk, A. Malyarevich, Xavier Mateos, and Konstantin Yumashev

Doc ID: 282113 Received 05 Dec 2016; Accepted 10 Feb 2017; Posted 13 Feb 2017  View: PDF

Abstract: Transparent glass-ceramics (GCs) containing Co:Mg(Al,Ga)2O4 nanocrystals (mean diameter: 7-9 nm) are synthesized by heat-treatments at 850–950 °C from magnesium aluminosilicate (MAS) glass nucleated by TiO2 and doped with Ga2O3 and CoO. The GCs exhibit a broadband 4A2(4F) → 4T1(4F) absorption due to the Co2+ ions, low saturation fluence (~0.5 J/cm2), fast recovery time of the initial absorption (~300 ns) and high laser damage threshold (~20 J/cm2). They are used for passive Q-switching of a diode side-pumped Er,Yb:glass laser generating 3.1 mJ / 20 ns pulses (peak power, 155 kW) at 1535 nm with a TEM00 output mode. The Q-switching performance of the Co:Mg(Al,Ga)2O4-based GCs is compared with various Co2+-doped GCs and Co:MgAl2O4 single crystal. The prepared GCs are promising for further applications in passively Q-switched Er:YAG and other Er crystalline (or ceramic) lasers.

Comparison of diffraction patterns exposed by pulsed and CW lasers on positive-tone photoresist

Ramunas Bakanas, Virginija Jankauskaitė, Andrejs Bulanovs, Stanislovas Zacharovas, and Andrius Vilkauskas

Doc ID: 273486 Received 11 Aug 2016; Accepted 10 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: Two different grating formation geometries for recording onto the positive-tone photoresist with pulsed laser and continuous-wave sources are analyzed and compared. Diffraction efficiency measurements and AFM examination have been performed in order to investigate the optical and topographical properties of the recorded structures. Gratings patterned by a continuous-wave laser and by a pulsed laser working in the single pulse and multi-pulse regime showed different surface roughness and optical properties. The possible reasons for surface roughness and effective exposure difference between pulsed and CW laser are discussed. The processing schemes of diffractive structures patterned by pulsed laser on to positive-tone photoresist for commercial hologram production are analyzed and presented in this work.

Improving the timing jitter of a superconducting nanowire single-photon detection system

Junjie Wu, Lixing YOU, Chen Sijing, Hao Li, Yu He, chaolin lv, Zhen Wang, and Xiaoming Xie

Doc ID: 283213 Received 20 Dec 2016; Accepted 09 Feb 2017; Posted 13 Feb 2017  View: PDF

Abstract: Timing jitter is a key parameter for the time-correlated applications of single-photon detectors. Low timing jitter is a unique merit of superconducting nanowire single-photon detectors (SNSPD). Quantitative analysis was carried out for the SNSPD system. Aid by an oscilloscope, we were able to measure a full-width at half-maximum system timing jitter as low as 14.2 ps for a high switching-current SNSPD using a room-temperature low-noise amplifier. While using a time-correlated single-photon counting module, the system timing jitter was 17.3 ps. The detector’s intrinsic timing jitter was estimated at ~12 ps.

Compact and Fabrication-tolerant Polarization Splitter Based on Horizontal Triple-slot Waveguide

Weifeng Jiang, Xiaohan Sun, and Azizur Rahman

Doc ID: 281044 Received 16 Nov 2016; Accepted 09 Feb 2017; Posted 13 Feb 2017  View: PDF

Abstract: A compact and fabrication-tolerant polarization beam splitter (PBS) based on the horizontal triple-slot waveguides is proposed and optimized by using the rigorous H-field based full-vectorial finite element method (VFEM) and the least squares boundary residual (LSBR) method. It can be noted from the simulation results that a fabrication-tolerant PBS with a compact length of 33 μm can be yielded based on the horizontal triple-slot waveguides. The polarization extinction ratios (PERs) are -21.8 dB and -20.3 dB at 1.55 μm wavelength for the quasi-TE and quasi-TM modes, respectively. The 1 dB bandwidth is 100 nm for both the polarizations. The fabrication tolerances are also thoroughly calculated for the proposed PBS.

Coded aperture correlation holography (COACH) system with improved performance

Joseph Rosen, Vijayakumar Anand, Roy Kelner, and Yuval Kashter

Doc ID: 281764 Received 29 Nov 2016; Accepted 09 Feb 2017; Posted 09 Feb 2017  View: PDF

Abstract: Coded aperture correlation holography (COACH) is a recently introduced technique for recording incoherent digital holograms of general three-dimensional scenes. In COACH, a random-like coded phase mask (CPM) is used as a coded aperture. Even though the CPM is optimized to reduce the background noise, there is still a substantial amount of noise, mitigating the performance of COACH. In order to reduce the noise, we first modify the hologram reconstruction method. Instead of computing the correlation between a complex hologram of the entire object and a hologram of a source point, in this study the numerical correlation is performed with a phase-only filter. In other words, the phase function of the Fourier transform of the source point hologram is used as the spatial filter in the correlation process. Furthermore, we propose and demonstrate two additional methods for reducing the background noise in COACH. The first is based on the integration of a quadratic phase function, as used in Fresnel incoherent correlation holography (FINCH), together with the CPM of COACH. This hybrid COACH-FINCH system enables dynamic trade-off between the amount of background noise and the axial resolution of the system. The second method is employed by recording COACH holograms with multiple independent CPMs and averaging over the reconstructed images. The results of the above two techniques are compared with FINCH and with a regular imaging system.

Interferometric wavefront sensing with a single diode using spatial light modulation.

Tarquin Ralph, Paul Altin, David Rabeling, David McClelland, and Daniel Shaddock

Doc ID: 280663 Received 14 Nov 2016; Accepted 09 Feb 2017; Posted 15 Feb 2017  View: PDF

Abstract: We present a new technique for the fine alignment sensing of optical interferometers. Unlikeconventional wavefront sensing systems, which use multi-element photodiodes, this approach works with a singleelementphotodiode, in combination with a spatial light modulator and digitally enhanced heterodyneinterferometry. As all signals pass through a single photo-detection and analogue path, the technique exhibits highcommon-mode rejection to low frequency errors present in conventional systems. By changing the modulationpattern on the spatial light modulator (SLM), the technique can also be extended to sensing higher-order wavefront errors. In this paper we demonstrate the technique experimentally and compare performance with aconventional heterodyne wavefront sensing system. This may improve and simplify alignment systems in spacebasedinterferometers such as the planned LISA gravitational wave detector and provide a way to optimise thepower in laser cavities not possible with the traditional segmented diode approach.

Quasi three-dimensional particle imaging with digital holography

Osku Kemppinen, Yuli Heinson, and Matthew Berg

Doc ID: 282452 Received 08 Dec 2016; Accepted 08 Feb 2017; Posted 09 Feb 2017  View: PDF

Abstract: In this work, approximate three-dimensional structures of microparticles are generated with digital holographyusing an automated focus method. This is done by stacking a collection of silhouette-like imagesof a particle reconstructed from a single in-line hologram. The method enables estimation of the particlesize in the longitudinal and transverse dimensions. Using the Discrete Dipole Approximation, themethod is tested computationally by simulating holograms for a variety of particles and attempting toreconstruct the known three-dimensional structure. It is found that poor longitudinal resolution stronglyperturbs the reconstructed structure, yet the method does provide an approximate sense for the structure’slongitudinal dimension. The method is then applied to laboratory measurements of holograms of singlemicroparticles and their scattering patterns.

Using Arago’s Spot to Monitor Optical Axis Shift in a Nagler-Petzval Refractor

Donald Bruns

Doc ID: 284105 Received 05 Jan 2017; Accepted 08 Feb 2017; Posted 09 Feb 2017  View: PDF

Abstract: Measuring the change in the optical alignment of a camera attached to a telescope is necessary to perform astrometric measurements. Camera movement when the telescope is refocused changes the plate constants, invalidating the calibration. Monitoring the shift in the optical axis requires a stable internal reference source. This is easily implemented in a Nagler-Petzval refractor by adding an illuminated pinhole and a small obscuration that creates a spot of Arago on the camera. Measurements of the optical axis shift for a commercial telescope are given as an example.

Effects of elemental-images' quantity on 3D segmentation using computational integral-imaging

doron aloni and Yitzhak Yitzhaky

Doc ID: 278916 Received 17 Oct 2016; Accepted 08 Feb 2017; Posted 09 Feb 2017  View: PDF

Abstract: 3D objects detection and isolation can be achieved algorithmically using computational integral-imaging data. The 3D scene is acquired by a multi-channel system, where, each channel (elemental-image) captures the scene from a shifted perspective angle. The number of these channels affects the weight, the cost and the computational load of the segmentation process, while a lower number of channels may reduce the performance of the objects separation in the 3D scene. This research examines the effect of the elemental-images quantity on the 3D object detection and segmentation, both under regular and noisy conditions. Moreover, based on our previous works, we perform an improvement to the 3D object segmentation quality using an adapted active contour method.

Photonic Doppler Frequency Shift Measurement Based on a Dual-Polarization Modulator

aijun Wen, Xiaoyan Li, Wei Chen, Yongsheng Gao, Shuiying Xiang, Huixing Zhang, and Xiaoming Ma

Doc ID: 281993 Received 07 Dec 2016; Accepted 08 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: In this paper, a novel photonic-assisted Doppler frequency shift (DFS) measurement scheme based on an integrated dual-polarization Mach-Zehnder modulator (DPol-MZM) is presented. In the proposed scheme, the DFS to be identified is transformed into a low-frequency electrical signal through an optical frequency-conversion link. The value of the DFS can be acquired by analyzing the spectrum of the low-frequency electrical signal. Meantime, the orientation of the DFS can be easily determined utilizing a 90-degree hybrid coupler. If the receiver is moving toward the transmitter, only the positive port has an output signal while only the negative port has an output signal if the receiver is moving away from the transmitter. The scheme can simultaneously obtain the value and the orientation of the DFS. In addition, in order to verify that the scheme is independent of the carrier frequency, the DFS which varies from -100KHz to 100KHz at a step of 10KHz for different microwave signals at frequency of 10GHz, 15GHz and 18GHz are demonstrated experimentally, where the errors are within±5×10^-6 Hz.

Enhanced sampling of two-dimensional interference patterns

eyal schwartz and Erez Ribak

Doc ID: 282922 Received 16 Dec 2016; Accepted 08 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: We propose a simple analysis to improve the resolution of interference patterns which consist of straight fringes. As the pattern is rotated with respect to the detector, each row or column in the camera perceives it in a slightly shifted manner. The different samplings of the same pattern allow the improvement of the resolution. We support this proposed method by analysis both by simulated and experimental interference patterns, and verify it using an interferogram obtained from a spectrally complex light source. The results imply that this technique could be implemented in different aspects of image analysis common in many fields in physics.

Analysis of Ultra Compact Plasmonic Modulator withMetal-Taper Structure Embedded in Furan–ThiopheneChromatophore Electro-Optic Polymer

Naoya Hojo, Tomo Amemiya, Kazuto Itoh, Zhichen Gu, Chiyumi Yamada, Toshiki Yamada, Junichi Suzuki, Yusuke Hayashi, Nobu Nishiyama, Akira Otomo, and Shigehisa Arai

Doc ID: 283399 Received 28 Dec 2016; Accepted 08 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: We analyzed two types of Mach–Zehnder (MZ) plasmonic modulators on a silicon-on-insulator platform with adifferent furan–thiophene chromophore electro-optic polymer (FTC-EO polymer) compare to other reports. Themetal-taper coupling structure and the metal-insulator-metal cross section in our design have been optimizedbased on the new material parameters. According to the simulation result, a modulator with a slot width of 50 nmand an on-off voltage of Vπ = 20 V can be 21 um long, leading to a total modulator loss of 15 dB which is comparableto previously reported devices.

Enhancing wavefront estimation accuracy by using higher-order iterative compensations in the Southwell configuration

Hui Guang, Yajun Wang, Lianxin Zhang, Lulu Li, Ming Li, and Linhong Ji

Doc ID: 280271 Received 09 Nov 2016; Accepted 08 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: Accurate wavefront integration based on gradient fields is crucial for various indirect measurement techniques, such as Shack-Hartman sensing, shearography and fringe reflection technique. In this paper, a higher-order iterative compensation algorithm is proposed to enhance the reconstruction accuracy for finite-difference-based least-square integration (FLI) method. In this method, higher-order gradient fields are reconstructed and the calculated residual gradient fields compensate the truncation error with the traditional FLI by iterations. Comparison of different FLI methods including traditional FLI, iterative FLI, higher-order FLI and the proposed FLI method is conducted. The result shows that the reconstructed wavafront with the proposed method is more accurate than those with other FLI methods. In addition, the impact of the gradient measurement noise is also discussed.

Remote photonic sensor to detect crude and refined oil

Óscar Sampedro and Jose Salgueiro

Doc ID: 280299 Received 09 Nov 2016; Accepted 07 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: This article describes a low-cost fluorometer to detect and distinguish among different types of crude and refined oil. The device is based on the measurement of induced fluorescence using 280 and a 390 nm LEDs as excitation sources, and is designed including a low-cost lock-in amplifier to increase sensitivity. The sensor is able to send data remotely and is fully configurable via telecommands. The apparatus can be a useful tool to detect, identify and monitor oil spills, when placed in buoys or added to marine or aerial vehicles.

Linearly polarized orbital angular momentum mode purity measurement in optical fibers

Youchao Jiang, Guobin Ren, Haisu Li, Min Tang, Yu Liu, Yue Wu, Wei Jian, and Shuisheng Jian

Doc ID: 280706 Received 14 Nov 2016; Accepted 07 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: We presented a simple method for measuring the mode purity of linearly polarized orbital angular momentum (OAM) modes in optical fibers. The method is based on the analysis of OAM beam projections filtered by a polarizer. The amplitude spectrum and phase spectrum of a data ring derived from the beam pattern are obtained by Fourier transform. Then, the coefficients of the mixed electric field expression can be determined and the mode purity can be obtained. The proposed method is validated and it is experimentally demonstrated in a two-mode fiber.

Specifics of spectral loss measurement in IR fibers

Victor Plotnichenko, Vyacheslav Sokolov, Elena Kryukova, Gennady Snopatin, Igor Scripachev, and M. churbanov

Doc ID: 281021 Received 23 Nov 2016; Accepted 07 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: Main error sources and their contribution to the total error of measuring the optical loss spectrum by cut-back method in the middle IR range (2-20 μm) are analyzed for multimode optical fibers made from materials with a high (2 to 4) refractive index value. It is shown that in case of insufficient fiber length, a neglect of the refractive index value leads to a systematic overestimation of the measured optical losses: the higher the refractive index of a fiber core material, the greater an overestimation. The main errors are typically introduced by a bad repeatability of preparation quality of fiber ends and a low value of signal-to-noise ratio after an initial fiber piece.

Robust silicon-on-insulator adiabatic splitter optimized by metamodeling

Karim HASSAN, Cédric Durantin, Vincent Hugues, Bertrand SZELAG, and Alain Gliere

Doc ID: 283440 Received 22 Dec 2016; Accepted 07 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: A robust integrated power splitter based on a silicon-on-insulator adiabatic coupler configuration is demonstrated. The power separation is achieved by a slow and simultaneous change of phase and coupling constants. The geometrical parameters of the device are determined thanks to a metamodel-based iterative optimization strategy. Solving the multiple parameter problem together with a realistic bandwidth constraint provides a clear improvement of the power splitting stability. The robustness is confirmed experimentally on a single device and at the wafer scale.

Measurement of Thickness of Highly Inhomogeneous Crude Oil Slicks

Anna Pyayt, Surya Cheemalapati, Heather Forth, Hao Wang, Karthik Raj Konnaiyan, and Jeff Morris

Doc ID: 280264 Received 09 Nov 2016; Accepted 07 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: As part of the Deepwater Horizon toxicity testing program, a number of laboratories generated oil slicks in the laboratory to study potential toxic effects of these oil slicks on aquatic organisms. Understanding the details of how these slicks affect aquatic organisms requires careful correlation between slick thickness and the observed detrimental effects. Estimating oil film thickness on water can be challenging, since the traditional color based technique used in the field is very imprecise. Also, as we demonstrate here, the films formed on the water surface are highly non-uniform on a micro-scale level, and thus uniform thin film thickness measurement techniques based on optical interference do not work. In this paper, we present a method that estimates the local thickness of weathered oil slicks formed on artificial seawater using light transmission and Beer-Lambert’s law. Here, we demonstrate results of careful calibration together with the actual thickness estimation. Due to the heterogeneity of the slicks formed, we present slick thickness as a range of thicknesses collected from multiple points within the oil slick. In all the experiments we used oil samples provided by the Natural Resource Damage Assessment toxicity testing program for the Deepwater Horizon oil spill. Therefore, this study has an important practical value and successfully addresses unique challenges related to measurements involving complex, viscous, paste-like heterogeneous substances such as weathered crude oil.

Temperature dependent optical properties of lead selenide quantum dotpolymer nanocomposites

Dennis Waldron, Amanda Preske, Joseph Zawodny, Todd Krauss, and Mool Gupta

Doc ID: 281715 Received 28 Nov 2016; Accepted 06 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: The optical properties of PbSe quantum dots (QDs) in AB9093 epoxy nanocomposite are examined with respect to temperature over a range of 0°C to 80°C, a useful working range for many QD-based sensors and devices, and results are compared to QDs in toluene solution. A complete characterization of QD optical properties is provided as a function of temperature, including the absorption spectrum, first excitonic 1-s absorption peak intensity and wavelength, fluorescence intensity, peak wavelength, and fluorescence spectrum full-width at half maximum. QD optical properties in toluene were found to be more sensitive to temperature as compared to those in AB9093. Interestingly, 1-s and fluorescence peak wavelength variation with temperature are reversed in AB9093 as compared to those in toluene solution. Results for the fluorescence properties of Lumogen F Red 305 dye in toluene are presented for comparison. The dye was found to have similar sensitivity to temperature as the QDs in terms of fluorescence peak wavelength shift, but the fluorescence peak intensity was far less variant. These results can be used to build a temperature sensor or as a guide to building other types of QD-based devices to be more robust against changes in ambient temperature.

Kilowatts-level cladding light stripper for high power fiber laser

Ping Yan, Junyi Sun, Yusheng Huang, Dan Li, Xuejiao Wang, Qirong Xiao, and mali gong

Doc ID: 283888 Received 30 Dec 2016; Accepted 06 Feb 2017; Posted 06 Feb 2017  View: PDF

Abstract: We designed and fabricated a high power cladding light stripper (CLS) by combining fiber etching CLS with cascaded polymer recoating CLS. The etched fiber reorganizes the NA distribution of the cladding light, leading to an increasing leaking power and a flatter leaking proportion distribution in the cascaded polymer-recoated fiber. The index distribution of the cascaded polymer-recoated fiber is carefully designed to leak cladding light evenly. More stages near the index of 1.451 are set to disperse the heat. The CLS is capable to work persistently under 1187W cladding light with an attenuation of 26.59dB. The highest local temperature is below 35℃.

Large aperture space optical system testing based on scanning Hartmann

Haisong Wei, Feng Yan, Xindong Chen, Hao Zhang, Qiang Cheng, Xue Donglin, Zeng xuefeng, and Xuejun Zhang

Doc ID: 279945 Received 01 Nov 2016; Accepted 06 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: Based on Hartmann testing principle, this paper proposes a novel image quality testing technology which applies to large aperture space optical system. Compared with the traditional testing method through large aperture collimator, the scanning Hartmann testing technology has great advantages due to its sample structure, low cost and ability to perform wavefront measurement of optical system. Basic testing principle of scanning Hartmann testing technology, data processing method and simulation process are presented in this paper. Certain simulation results are also given to verify the feasibility of this technology. Furthermore, a measuring system is developed to conduct a wavefront measurement experiment for a 200mm aperture optical system. The small deviation (6.3%) of root mean square (RMS) between experimental results and interferometric results indicates that the testing system can measure low order aberration correctly, which means that the scanning Hartmann testing technology has the ability to test the imaging quality of large aperture space optical system.

Resolution enhancement of the microscopic imaging by unknown sinusoidal structured illumination with iterative algorithm

Jun Ma, Caojin Yuan, Jiantai Dou, Jiadong Wei, Shaoteng Feng, Shouping Nie, and Chenliang Chang

Doc ID: 279882 Received 02 Nov 2016; Accepted 06 Feb 2017; Posted 06 Feb 2017  View: PDF

Abstract: The microscopy by sinusoidal structured illumination is a conventional method to improve the resolution, which largely depends on the accurate knowledge of the structured pattern and phase-shifting amounts. Besides the phase-shifting amounts, the period, the modulation and the background intensity of the pattern are extracted from three segmented raw images in the spatial domain by the iterative algorithm. The low and high frequency information of the object is respectively solved and synthesized in the Fourier space with obtained data. Since the unknown object information is not involved in pattern parameters solving process, it is possible to figure out the problem with higher precision and less requirements. We test the performance of this method in the experiments. The resolution is improved with the designed carrier frequency of the illumination pattern.

Magnetization shaping generated by tight focusing of azimuthally polarized vortex multi-Gaussian beam

weichao yan, zhongquan nie, Xueru Zhang, Yuxiao Wang, and Yinglin Song

Doc ID: 280948 Received 21 Nov 2016; Accepted 05 Feb 2017; Posted 06 Feb 2017  View: PDF

Abstract: Combining the vector diffraction theory with the inverse Faraday effect, we have theoretically studied magnetization shaping generated by tight focusing of azimuthally polarized multi-Gaussian beam superimposed with helical phase. By selecting optimized parameters of multi-Gaussian beam and topological charge of spiral phase plate, not only a super-long and sub-wavelength longitudinal magnetization needle with single/dual channels for a single-len high numerical aperture focusing system, but also an extralong and three dimensional super-resolution longitudinal magnetization chain with single/dual channels for a 4π high numerical aperture focusing system is achieved in the focal region. Further more, by continuously changing the phase difference between two counter-propagating beams, these super-long longitudinal magnetization chains with three dimensional super-resolution can dynamically move alongthe z axis. It is expected that these results pave the path for fabricating magnetic lattices for spin wave operation, multiple atoms or magnetic particle trapping and transportation, confocal and magnetic resonance microscopy, as well as multilayer ultrahigh density magnetic storage.

An optical method to measure the surface of objects by using only one photo

Qin-Zhi Fang, Jiong Qian, HyeonGyu Beom, and Hui Min Yu

Doc ID: 281906 Received 30 Nov 2016; Accepted 05 Feb 2017; Posted 06 Feb 2017  View: PDF

Abstract: A novel method to measure the dimension of an object with one defocused photo of an object has been presented in this paper. To do this, a photo of the object is taken by a camera. The focal plane is chosen as a reference plane. The coordinates of the object surface are obtained by using the camera’s parameters and corresponding defocused distance. The depth from the reference plane is obtained by evaluating the confusion degree of the photo around an edge. The relationship between the confusion degree and the distance from the reference plane has been given theoretically and experimentally. Several objects have been measured with the method, and it is shown that the results obtained are reliable. For non-textured surfaces, the edges of objects can be used to make the measurement.

Phase-sensitive cascaded four-wave mixing processes for generating continuous-variable entanglement

Li Wang and Jietai Jing

Doc ID: 282002 Received 05 Dec 2016; Accepted 03 Feb 2017; Posted 06 Feb 2017  View: PDF

Abstract: Quantum entanglement shared by different parties enhances their capabilities to communicate and it isthe core content of continuous variables quantum optics and quantum information science. Here, westudy an experimentally feasible scheme for generating quantum entanglement of bipartite and tripartitecases based on phase-sensitive cascaded four-wave mixing processes in rubidium vapor. Quantum entanglementof bipartite and tripartite cases in our system, which can be manipulated by the phases andthe intensity gains of the input beams, is predicted. We also find a sufficient optimal single-conditioncriterion to give a valid description for genuine tripartite quantum entanglement in our system. Thesufficient optimal single-condition criterion is convenient, and can be extended to genuine multipartiteentanglement.

Aberration compensation for optical trapping of cells within living mice

Min-Cheng Zhong, Yinmei Li, and Ziqiang Wang

Doc ID: 279914 Received 01 Nov 2016; Accepted 03 Feb 2017; Posted 06 Feb 2017  View: PDF

Abstract: Optical tweezers have been used to trap and manipulate micro-particles within living animals. When optical trap is constructed with an oil immersion objectives, it suffers from spherical aberrations. There have been lots of reports about the investigation on the effect of spherical aberration when the particles are trapped in water medium. However, the dependence of optical force on trapping depth is still ambiguous when the trapped particles are immersed in high refractive index medium (such as biological tissue, refractive index solution). In this paper, the micro-particles are immersed in aqueous solution of glycerol to mimic the cells within biological tissue. As the trapping laser is focused into the specimen, spherical aberration is introduced, degrading the optical trapping performance. It is similar to trapping in water, altering the effective tube length can also compensate for the spherical aberration of optical trap in high refractive index medium. At last, the cells in living mice are trapped by the optical tweezers with help of spherical aberration compensation.

Development of a multi-perspective optical measuring system for investigating switching arcs at the nozzle exit of circuit breakers

Franz Marius Stoffels, Sandor Simon, Paul Nikolic Nikolic, Patrick Stoller, and Jan Carstensen

Doc ID: 277784 Received 29 Sep 2016; Accepted 02 Feb 2017; Posted 03 Feb 2017  View: PDF

Abstract: High voltage gas circuit breakers, which play an important role in the operation and protection of the power grid, function by drawing an arc between two contacts and then extinguishing it by cooling it using a transonic gas flow. Improving the design of circuit breakers requires an understanding of the physical processes involved in interruption of the arc, particularly during the zero-crossing of the alternating current (the point in time when the arc can be interrupted). Most diagnostic techniques that are currently available focus on measurement of current, voltage, and gas pressure at defined locations. However, these integral properties do not give sufficient insight into the arc physics. In order to understand the current interruption process, spatially resolved information about the density, temperature, and conductivity of the arc and surrounding gas flow is needed. Due to the three-dimensional, unstable nature of the arc in a circuit breaker, especially near current-zero, a spatially-resolved, tomographic diagnostic technique is required that is capable of freezing the rapid, transient behavior and that is insensitive to the vibrations and electromagnetic interference inherent in the interruption of short-circuit current arcs. Here a new measurement system, based on background-oriented Schlieren (BOS) imaging, is presented and assessed. BOS imaging using four beams consisting of white light sources, background pattern, imaging optics, and camera permits measurement of the line-of-sight integrated refractive index. Tomographic re-construction is used to determine the three-dimensional, spatially resolved index of refraction distribution, which in turn is used to calculate the density. The quantitative accuracy of a single beam of the BOS setup is verified by using a calibration lens with a known focal length. The ability of the tomographic reconstruction to detect asymmetric features of the arc and surrounding gas flow is assessed semi-quantitatively using a nozzle that generates two gas jets, as described in [E. Goldhahn, J. Seume, The Background oriented schlieren technique: sensitivity, accuracy, resolution and application to a three-dimensional density field, Experiments in Fluids, Vol. 43, No. 2, pp. 241-249, 2007.]. Experiments using a simple model of a circuit breaker, which provides optical access to an ~1 kA arc that burns between two contacts and is blown through a nozzle system by synthetic air from a high pressure reservoir, are also described. The density in the arc and surrounding gas flow is re-constructed, and the limitation of the technique, which are related to the temporal and spatial resolution, are addressed.

Background noise removal in X-ray ptychography

Zijian Xu, Chunpeng Wang, Haigang Liu, Yong Wang, Renzhong Tai, and Jian Wang

Doc ID: 278414 Received 12 Oct 2016; Accepted 02 Feb 2017; Posted 06 Feb 2017  View: PDF

Abstract: Ptychography is a diffraction-based X-ray microscopy method that removes the resolution limit imposed by image-forming optical elements. However, background noise in the recorded diffraction patterns will degrade the reconstructed images and may cause reconstruction failure. Removal of the background noise from a ptychography dataset is an important but rather ambiguous pre-reconstruction data processing step because high spatial frequency diffraction signals are inevitably partly wiped out along with the noise. In this paper, several newly-designed techniques for removing background noise from experimental ptychographic datasets are provided. Meanwhile, effects of residual background noise and high frequency signal loss on reconstructed image quality are discussed in detail. The image quality is assessed quantitatively by power spectral density analysis method and spatial resolution calculation. Both the simulated and experimental results indicate that the positive effect of noise removal by these methods significantly exceeds the negative effect of the accompanied high spatial frequency signal loss because part of the lost signals can be recovered by the improved consistencies between neighboring diffraction patterns by the noise removal.

Backward-gazing method for measuring solar concentrators shape errors

Francois Henault, Cyril Caliot, and Mathieu Coquand

Doc ID: 279135 Received 19 Oct 2016; Accepted 02 Feb 2017; Posted 06 Feb 2017  View: PDF

Abstract: This paper describes a backward-gazing method for measuring the opto-mechanical errors of solar concentrating surfaces. It makes use of four cameras placed near the solar receiver and simultaneously recording images of the sun reflected by the optical surfaces. Simple data processing then allows reconstructing the slope and shape errors of the surfaces. The originality of the method is enforced by the use of generalized quad-cell formulas and approximate mathematical relations between the slope errors of the mirrors and their reflected wavefront in the case of sun-tracking heliostats at high incidence angles. Numerical simulations demonstrate that the measurement accuracy is compliant with standard requirements of solar concentrating optics in presence of noise or calibration errors. The method is suitable to fine characterization of the optical and mechanical errors of heliostats and their facets, or to provide better control for real-time sun tracking.

In vivo 3D imaging of human tympanic membrane using wide-field diagonal-scanning optical coherence tomography probe

Kibeom Park, Namhyun Cho, Jeong Hun Jang, Sang Heun Lee, Pilun Kim, Man Sik Jeon, Stephen Boppart, jeehyun kim, and Woonggyu Jung

Doc ID: 278740 Received 14 Oct 2016; Accepted 02 Feb 2017; Posted 02 Feb 2017  View: PDF

Abstract: A wide-field optical coherence tomography (OCT) probe was developed that adapts a diagonal scanning scheme for three-dimensional (3D) in vivo imaging of the human tympanic membrane. The probe consists of a relay lens to enhance the lateral scanning range up to 7 mm. Motion artifacts that occur with the use of hand-held probes were found to be decreased owing to the diagonal scanning pattern, which crosses the center of the sample to facilitate entire 3D scans. 3D images could be constructed from a small number of two-dimensional OCT images acquired using the diagonal scanning technique. To demonstrate the usefulness and performance of the developed system with the hand-held probe, in vivo tympanic membranes of humans and animals were imaged in real time

Plasmonic nanogratings on MIM and SOI thin-film solar cells: comparison and optimization of optical and electric enhancements

Mohammad Sabaeian and Mehdi Heydari

Doc ID: 279157 Received 20 Oct 2016; Accepted 02 Feb 2017; Posted 02 Feb 2017  View: PDF

Abstract: In this work, Ag nanogratings comprised of arrays of nanostrips with three different cross sections of triangle, rectangular, and trapezoidwere considered and put at the top of the thin-film metal-insulator-metal (MIM) and semiconductor-on-insulator (SOI) solar cells. Then, theoptical absorption and the short-circuit current density (JSC) enhancement (relative to a bare cell) were calculated and compared. In additionthe best strip cross section, among three types of cross sections, and the optimum grating period were found. The results showed that for TEmodeonly the waveguide modes were excited inside the Si active layer with the assistance of Ag nanogratings. For TM-mode, the waveguideas well as the localized surface plasmonic (LSP) modes were excited. The LSP modes, which were excited at the longer wavelengths centeredon ~600 nm, led to an additional and consequently a larger JSC enhancement. Finally, among the various types of plasmonic SOI and MIMsolar cells, a SOI cell with a 300 nm grating period, comprised of rectangular nanostrips, showed a 40% enhancement in JSC which is thehighest possible value achieved in this work.

High efficiency echelle gratings for MIGHTI, the spatial heterodyne interferometers for the ICON mission

Christoph Englert, Charles Brown, Bernhard Bach, Erich Bach, Kirk Bach, John Harlander, John Seely, Kenneth Marr, and Ian Miller

Doc ID: 280647 Received 17 Nov 2016; Accepted 02 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: Development of a new generation of low groove density blazed echelle gratings optimized for MIGHTI, a space borne spatial heterodyne interferometer operating in the visible and near infrared is described. Special demands are placed on the wavefront accuracy, groove profile, and efficiency of these gratings. These demands required a new ruling for this application with significant improvements over existing gratings. Properties of a new generation of highly efficient, plane gratings with 64 grooves/mm blazed at 8.2° are reported.

Large real-time holographic 3D displays: enabling components and results

Ralf Häussler, Yuri Gritsai, Enrico Zschau, Robert Missbach, Hagen Sahm, Michael Stock, and Hagen Stolle

Doc ID: 281923 Received 02 Dec 2016; Accepted 02 Feb 2017; Posted 08 Feb 2017  View: PDF

Abstract: A holographic 3D display with 300 mm × 200 mm active area was built. The display comprises a spatial light modulator that modulates amplitude and phase of light and thus enables holographic reconstruction with high efficiency. Furthermore, holographic optical elements in photopolymer films and laser light sources are used. The requirements on these optical components are discussed. Photographs taken at the display demonstrate that a 3D scene is reconstructed in depth, thus enabling selective accommodation of the observer’s eye lenses and natural depth perception. The results demonstrate the advantages of SeeReal’s proprietary holographic 3D display solution.

Research of combining module based on coherent polarization beam combining

Yan Yang, Chao Geng, Feng Li, and Xinyang Li

Doc ID: 279069 Received 18 Oct 2016; Accepted 01 Feb 2017; Posted 02 Feb 2017  View: PDF

Abstract: Multi-aperture receiver with phased array is an effective approach to overcome the effect of the random optical disturbance in coherent free-space laser communications, in which how to combine the multiple laser beams received by the phased array antenna efficiently is one of the key technologies. A combining module based on coherent polarization beam combining (CPBC) is proposed in this paper. The combining module can combine multiple laser beams to one laser beam with high combining efficiency and output a linearly polarized beam. The principle of the combining module is introduced. The influence factors of the CPBC are analyzed, and the performance of the combining module is evaluated. Moreover, the feasibility and the expansibility of the proposed combining module are validated in the experiments of CPBC based on active phase locking.

Selection of the tagged photons by off axis heterodyne holography in Ultrasound-modulated optical tomography

Michel Gross

Doc ID: 278543 Received 11 Oct 2016; Accepted 01 Feb 2017; Posted 01 Feb 2017  View: PDF

Abstract: Ultrasound-modulated optical tomography (UOT) is a technique that images optical contrast deep inside scattering media. Heterodyne holography is a promising tool able to detect the UOT tagged photons with high efficiency. In this work, we describe theoretically the detection of the tagged photon in heterodyne holography based UOT, show how to filter the untagged photon, and discuss the effect of shot noise. The discussion considers also speckle decorrelation. We show that optimal detection sensitivity can be reached, if the frame exposure time of the camera used to perform the holographic detection is of the order of the decorrelation time.

Optimizing spectral compositions of multi-channelLED light sources by IES color fidelity index andluminous efficacy of radiation

Haisong Xu and Fuzheng Zhang

Doc ID: 281749 Received 29 Nov 2016; Accepted 31 Jan 2017; Posted 01 Feb 2017  View: PDF

Abstract: The trade-off between the color fidelity index (Rf) released recently by the Illuminating Engineering Society ofNorth America (IES) and luminous efficacy of radiation (LER) was investigated by adjusting the peak wavelengths,spectral widths, and intensities of four-channel LEDs utilizing a multi-objective optimization algorithm based ondifferential evolution in the correlated color temperature (CCT) ranging from 2800 K to 6500 K for general lighting.The results indicate that Rf at a specific LER value decreases with the increasing CCT, and vice versa, and that Rf hassignificant improvements over the Commission Internationale de l’Eclairage (CIE) color rendering index (CRI) inavoiding spectral gaming and evaluating the light sources even with negative CIE general CRI (Ra). Further, theoptimal peak wavelengths with regard to Rf were identified as 629 nm, 568 nm, 504 nm, and 447 nm, yielding highcolor rendering in terms of Rf (93 ~ 94) and Ra (95 ~ 97) and relatively excellent LER (299 lm/W ~ 339 lm/W) overa wide range of CCT from 2800 K to 6500 K. This suggests that Rf can be compatible with Ra, making it possible toobtain a common set of optimal peak wavelengths for Rf and Ra. Besides, the IES method could assess saturated redand skin tones more fairly than the CIE CRI. With a practical 17-channel LED array covering the resulted fouroptimal peak wavelengths, the improvements of the IES method over the CIE CRI were validated further.

Optical fine-tuning for improving the dark level of a reflective liquid crystal display

Jin Seog Gwag

Doc ID: 282964 Received 15 Dec 2016; Accepted 31 Jan 2017; Posted 01 Feb 2017  View: PDF

Abstract: Optical fine-tuning was performed to reduce blue light leakage in a conventional reflective LCD and to obtain a reflective LCD with better contrast ratio. Total light leakage in the dark state was examined by simulation, according to the optical axes of the half-wave plate and LC layer and the central wavelength used in the optical design of the LCD. The contrast ratio of the reflective LCD could be improved by more than fivefold, compared to that of a conventional LCD with a wideband optical design, when the optical axis angles of the half-wave plate and the LC layer were 75° and 15.68°, respectively, and the central wavelength was 520 nm. Therefore, such optical fine-tuning can be applied to reflective LCDs to increase their contrast ratio.

A Multilateral Spectral Radiance Factor Scale Comparison

Christian Strothkämper, Alejandro Ferrero, Annette Koo, Priit Jaanson, Guillaume Ged, Gael Obein, Stefan Källberg, Jan Audenaert, Frederic Leloup, Francisco Martínez-Verdú, Esther Perales, alfred schirmacher, and Joaquin Campos-Acosta

Doc ID: 279674 Received 01 Nov 2016; Accepted 31 Jan 2017; Posted 06 Feb 2017  View: PDF

Abstract: The field of spectral radiance factor (SRF) measurements has seen growing interest in recent years. Scale conformity has so far only been established between the national metrology institutes (NMIs) of Germany and the USA. This study aims at a bigger, multilateral scale comparison. For this purpose, a total of six NMIs participated in a scale comparison of gonio-spectrophotometers based on neutral and colored diffusely reflecting ceramics samples. In addition, two universities, providing a home-built gonioreflectometer and two widely used commercially available color measurement instruments, respectively, were involved. The wavelength range of the scale comparison covers the visible wavelength range from 380 nm to 780 nm. Results indicate systematic issues and the uncertainty evaluation of the NMIs requires further work, though for the greatest part of the covered spectral range the agreement is good.

Global Maxima for the Acousto-Optic Effect in SrB4O7 Crystals

Oleh Buryy, NAZARIY ANDRUSHCHAK, ANDRIY RATYCH, Natalya Demyanyshyn, Bohdan Mytsyk, and Anatoliy Andrushchak

Doc ID: 278156 Received 04 Oct 2016; Accepted 30 Jan 2017; Posted 01 Feb 2017  View: PDF

Abstract: For the first time the global maxima of the acousto-optic interaction are theoretically determined for biaxial SrB4O7 crystals byextreme surfaces method. As it is shown, the highest value of the acousto-optic figure of merit M2 is equal to 6.3⋅10-16 s3/kg andachieved in the case of the isotropic diffraction of the electromagnetic wave propagating in [010] direction on the fast quasitransversalacoustic wave.

Expanding color gamut of reflective liquid crystal displays from filtering undesirable wavelengths of backlight by an embedded etalon

Ko-Ting Cheng, Cheng-Kai Liu, and Tsung-Hsun Yang

Doc ID: 279309 Received 21 Oct 2016; Accepted 30 Jan 2017; Posted 01 Feb 2017  View: PDF

Abstract: This work demonstrates a method to reduce the intensity of the undesirable wavelengths of blue and green ambient lights to expand the color gamut of reflective liquid crystal displays (LCDs) by an embedded etalon. The built-in reflector of the reflective LCDs is replaced by the blue-green overlapping wavelengths filtering etalon which is used to reduce the intensity of undesirable B- and G-primaries, thereby decreasing the color crosstalk of B- and G-color filters. After etalon adoption, the color gamut can be expanded from 105.96% to 121.81% of NTSC in CIE 1976 color space. Compared with the color gamut of the display without the blue-green overlapping wavelength etalon, the maximum expansion of color gamut is ~15.85%. Moreover, the balance between light loss and color gamut expansion should be taken into consideration.

High-temperature sensor instrumentation with a thinfilm-based sapphire fiber

Yuqing Guo, Wei Xia, Zhangzhong Hu, and Ming Wang

Doc ID: 280126 Received 04 Nov 2016; Accepted 30 Jan 2017; Posted 01 Feb 2017  View: PDF

Abstract: A novel sapphire fiber-optic high temperature sensor has been designed and fabricated based on blackbodyradiation theory. Metallic molybdenum has been used as the film material to develop the blackbody cavity owing toits relatively high melting point compared to that of sapphire. More importantly, the fabrication process for theblackbody cavity is simple, efficient and economical. Thermal radiation emitted from such a blackbody cavity istransmitted via optical fiber to a remote place for detection. The operating principle, the sensor structure and thefabrication process are described here in detail. The developed high temperature sensor was calibrated through acalibration blackbody furnace at temperatures from 900 °C to 1200 °C and tested by a sapphire crystal growthfurnace up to 1880 °C. The experimental results of our system agree well with those from a commercial RayteckMR1SCCF infrared pyrometer and the maximum residual is approximately 5 °C, paving the way for high accuracytemperature measurement especially for extremely harsh environments.

Analysis of transient radiative transfer induced by anincident short-pulsed laser in a graded index mediumwith Fresnel boundary

yong zhang, Cunhai WANG, Hong-Liang Yi, and Ming Xie

Doc ID: 280537 Received 09 Nov 2016; Accepted 30 Jan 2017; Posted 01 Feb 2017  View: PDF

Abstract: Transient radiative transfer induced by short-pulsed laser in a one-dimensional graded index medium isinvestigated by discontinuous finite element method (DFEM). The boundaries of the medium are Fresnel reflectorsand the incident pulse is considered as the combination of the collimated and the diffuse parts after its firstinteraction with the medium. The correctness and accuracy of the DFEM solutions for time-resolved reflectanceand transmittance are firstly validated by comparisons with the results obtained by a Monte Carlo method, and theDFEM is then employed to investigate the transient radiative transfer in a graded index medium with Fresnelboundary. Effects of the refractive index distributions, the pulse width, the optical thickness, and the scatteringphase functions on the transient radiative signals are examined. Several meaningful trends on the time-resolvedreflectance and transmittance are observed and analyzed.

The effect of oil on an electrowetting lenticular lens and related optical characteristics

Dooseub Shin, Junoh Kim, Cheoljoong Kim, Gyohyun Koo, Jee Hoon Sim, Junsik Lee, and Yong H. Won

Doc ID: 280707 Received 14 Nov 2016; Accepted 30 Jan 2017; Posted 01 Feb 2017  View: PDF

Abstract: While there are many ways to realize auto-stereoscopic 2D/3D switchable displays, the electrowettinng lenticular lens is superior due to the high optical efficiency and short response time. In this paper, we proposed more stable electrowetting lenticular lens by controlling the quantity of oil. With a large amount of oil, the oil layer was broken and the lenticular lens was damaged at relatively low voltage. Therefore, controlling the amount of oil is crucial to obtain the required dioptric power with stability. We proposed a new structure to evenly adjust the volume of oil and the dioptric power was measured by varying the volume of oil. Furthermore, the optical characteristics were finally analyzed in the electrowetting lenticular lens array with a proper amount of oil.

Tunable resonance-domain diffraction gratings based on electrostrictive polymers

Ramon Axelrod, Michael Golub, and Yosi Shacham

Doc ID: 281533 Received 25 Nov 2016; Accepted 29 Jan 2017; Posted 31 Jan 2017  View: PDF

Abstract: Critical combination of high diffraction efficiency and large diffraction angles can be delivered by resonance-domain diffractive optics with high aspect ratio and wavelength-scale grating periods. To advance from static to electrically tunable resonance domain diffraction grating we resorted to its replication onto 2-5 µm thick P(VDF-TrFE-CFE) electrostrictive ter-polymer membranes. Electro-mechanical and optical computer simulations provided higher than 90% diffraction efficiency, large continuous deflection range exceeding 20° and capabilities for adiabatic spatial modulation of the grating period and slant. A prototype of the tunable resonance domain diffraction grating was fabricated in soft-stamp thermal nano-imprinting process, characterized, optically tested and provided experimental feasibility proof for the tunable sub-micron-period gratings on electrostrictive polymers.

Highly Sensitive Refractive Index Sensor Based on TiO2 Nanowire Array

Qiu-Shun Li, Dong Xiang, Zhi-Min Chang, Jian-Guo Shi, Yao-Hong Ma, Lei Cai, and Wen-Fei Dong

Doc ID: 281540 Received 28 Nov 2016; Accepted 29 Jan 2017; Posted 31 Jan 2017  View: PDF

Abstract: We proposed a novel high sensitive refractive index (RI) sensor via combining Kretschmann prism with TiO2 nanowire array and do not use any metallic layer in the Kretschmann configuration. Its RI sensing performance was investigated through measuring different concentrations of sodium chloride solution. Experimental results showed that, with increasing RI of liquid, the resonant wavelength in the reflectance spectrum red shifted gradually in the visible light range. There was a very good linear relationship between resonant wavelength and RI in the range of 1.3330 to 1.3546. More importantly, contrast to the SPR sensor, the interferometric sensors showed higher sensitivity to the external RI. In the case of transverse magnetic mode, the RI sensitivity is up to 320,700.93 a.u./RIU (refractive index unit) by expression of light intensity, which is 9.55 times of that of SPR sensor. As for transverse electric mode, it achieves 4,371.76 nm/RIU by expression of resonant wavelength, which is increased by a factor of 1.4 in comparison with the SPR sensor. Moreover, the experimental results have favorable repeatability. TiO2 nanowire array sensor has also other advantages such as easy manufacture, low cost, and in situ determination etc. To our knowledge, this fact is reported for the first time. It has great potential applications in the field of biological and chemical sensing. © 2015 Optical Society of America

Refractive index sensor based on multi-notched plastic optical fiber

Jie Zheng, Teng Chuanxin, Jing Ning, Fangda Yu, and Yue Ding

Doc ID: 282212 Received 05 Dec 2016; Accepted 29 Jan 2017; Posted 31 Jan 2017  View: PDF

Abstract: A plastic optical fiber (POF) with multi-notched structure as a long period grating was proposed for refractive index (RI) sensing. A new approach to modify the structure of POF with enhanced RI sensitivity was carried out. The multi-notched structure was made on the surface of the fiber by pressing a thread rod against the POF. The RI sensing performances for straight and macro-bending (U-shaped) POFs with this structure were studied. It is found that the POF probes with straight multi-notched structure were not sensitive enough for RI measurement. After bending the multi-notched structure into U-shaped probes, the RI sensing performance was improved markedly. By altering the structural parameters, the RI sensing performance of the U-shaped POF probes with multi-notched structure were optimized, and the highest sensitivity of 1130%/RIU with a resolution of 8.44×10-4 RIU in the RI range of 1.333-1.410 was obtained. In addition, the characteristic of the temperature dependence of the sensor was presented. The probe is a low cost solution for RI sensing purpose, which has the features of simple structure, easy fabrication, compact size and intensity modulation at visible wavelengths.

Zonal Processing of Hartmann or Shack-Hartmann patterns

Francisco Gantes, Zacarias Malacara-Hernandez, Daniel Malacara-Doblado, and Daniel Malacara Hernandez

Doc ID: 280886 Received 15 Nov 2016; Accepted 29 Jan 2017; Posted 31 Jan 2017  View: PDF

Abstract: Instead of measuring the wavefront deformations, Hartmann and Shack-Hartmann tests, measure the wavefront slopes, which are equivalent to the ray transverse aberrations. Numerous different integration methods have been described in the literature to obtain the wavefront deformations from these measurements. Basically, they can be classified in two different categories, i.e., modal and zonal. In this paper we describe a proposed new zonal procedure. This method finds a different analytical expression for each square cell formed by four sampling points in the pupil of the system. In this manner, a full single analytical expression for the wavefront is not obtained. The advantage is that small localized errors that cannot be adjusted by a single polynomial function can be represented with this method. A second advantage is that the analytical function for each cell is obtained in an exact manner, without the errors in a trapezoidal integration.

Electrical and Optical Performance evaluation in ‎Solution Process Optoelectronics Devices: ‎Theoretical Modeling

Mahboubeh Dolatyari, Mohammad Rashidi, Ali Rostami, and ghassem Rostami

Doc ID: 281963 Received 08 Dec 2016; Accepted 29 Jan 2017; Posted 01 Feb 2017  View: PDF

Abstract: In this paper, a computational and semi-analytical approach for theoretical evaluation of solution process basedoptoelectronic devices such as quantum-dot infrared photodetectors is presented. Using the presented model, the darkand photocurrent for infrared photodetectors are extracted. In this regard, it has assumed that there are two mainmechanisms contributing to the devices current: the electron tunneling in the confined states and the drift of electronsin the continuum states. For the former, the Landuar-Buttiker formalism in which the transmission function wasobtained through the Green’s function method is used. However, for the latter, while considering the trapping and detrappingroles of QDs, the drift-diffusion model was applied. Furthermore, different geometrical effects, including theQDs’ size distribution, the space between QDs, the system’s length, and the system’s width, on the device’s parameters,including absorption coefficient, photo-conductive gain, dark current, and detectivity, have analyzed. The results show agreat dependency of the device’s performance on these geometrical aspects. For example, it has been shown that thenon-uniformity of the QDs’ sizes could have negative effects on the device’s detectivity. Besides, it could noticeablyinfluence the tunneling current such as decreasing the maximum value of the current.‎

Light Transmission Spectroscopy in Real Time: a High-Resolution Nanoparticle Analysis Instrument

Carol Tanner, Nan Sun, Alison Deatsch, Frank Li, and Steven Ruggiero

Doc ID: 281280 Received 21 Nov 2016; Accepted 27 Jan 2017; Posted 31 Jan 2017  View: PDF

Abstract: This paper describes Light Transmission Spectroscopy (LTS), a technique for eliminating spectral noise and systematic effects in real-time spectroscopic measurements. In our work, we combine LTS with spectral inversion for the purpose of nanoparticle analysis. This work employs a wide-band multi-wavelength light source and grating spectrometers coupled to CCD detectors. The light source ranges from 210 to 2000 nm, the wavelength dependent light detection system ranges from 200 to 1100 nm with ≤1 nm resolution, and the nanoparticle diameters range from 1 to 3000 nm. The nanoparticles are suspended in pure water or water-based buffer solutions. For testing and calibration purposes, results are presented for nanoparticles composed of polystyrene and gold. Mie theory is used to model the total extinction cross section, and spectral inversion is employed to obtain quantitative particle size distributions, from which information on the size, shape, and number of nanoparticles can be derived. Discussed are the precision, accuracy, resolution, and sensitivity of our results. The LTS technique is quite versatile and can be applied to spectroscopic investigations where wideband, accurate, low-noise, real-time spectra are desired.

Ultra-fast Analog-to-Digital Converter Based on a Nonlinear Triplexerand an Optical Coder with a Photonic CrystalStructure

Farhad Mehdizadeh, Mohammad Soroosh, hamed Alipour-Banaei, and Ebrahim Farshidi

Doc ID: 282082 Received 02 Dec 2016; Accepted 27 Jan 2017; Posted 31 Jan 2017  View: PDF

Abstract: In this paper, we propose a novel all-optical analog-to-digital converter based on photonic crystals. The proposedstructure is composed of a nonlinear triplexer and an optical coder. The nonlinear triplexer is for creating discretelevels in the continuous optical input signal, and the optical coder is for generating a 2-bit standard binary code outof the discrete levels coming from the nonlinear triplexer. Controlling the resonant mode of the resonant ringsthrough optical intensity is the main objective and working mechanism of the proposed structure. The maximumdelay time obtained for the proposed structure was about 5 ps and the total footprint is about 1520 μm2.

Three-Dimensional Integral Imaging and Object Recognition for Long Wave Infrared Imaging

Satoru Komatsu, Adam Markman, Abhijit Mahalanobis, Kenny Chen, and Bahram Javidi

Doc ID: 278287 Received 11 Oct 2016; Accepted 26 Jan 2017; Posted 30 Jan 2017  View: PDF

Abstract: When an object of interest is behind occlusions such as a branch or a bush, it is difficult for pattern recognition algorithms to detect the object. Furthermore, in poorly illuminated environments, imaging using cameras that operate in the visible part of the spectrum do not perform well due to the inherent low illumination conditions. To overcome these obstacles, we propose a passive three-dimensional (3D) imaging technique known as integral imaging (II) using a long wave infrared (LWIR) camera. 3D imaging allows for the removal of occlusions in front of objects along with depth estimation by reconstructing the scene at a particular depth plane. This is done by combining the information of multiple images captured using the LWIR camera, known as elemental images (EI), with each image having a slightly different perspective of the scene. Moreover, LWIR imaging performs well in photon-limited environments due to detecting thermal radiation from an object rather than the reflected light. Once the elemental images have been captured, image restoration using restoration filters is performed. A 3D scene is then reconstructed and object recognition using support vector machines is performed. Our experiments show that 2D imaging may fail to detect occluded faces whereas passive 3D imaging could be successful in face detection of all the faces including the occluded ones. To the best of our knowledge, this is the first report on combining passive 3D imaging with LWIR for object recognition, and in particular for photon-limited scenarios.

Experimental, Infrared Point Source Detection using an Iterative GLRT Algorithm

Jonathan Nichols and James Waterman

Doc ID: 281122 Received 18 Nov 2016; Accepted 26 Jan 2017; Posted 30 Jan 2017  View: PDF

Abstract: This work documents the performance of a recently proposed GLRT algorithm in detecting thermal point source targets against a sky background. A calibrated source is placed above the horizon at various ranges and then imaged using a mid-wave infrared camera. The proposed algorithm combines a so-called ``shrinkage' estimator of the background covariance matrix and an iterative maximum likelihood estimator of the point source parameters to produce the GLRT statistic. It is clearly shown that the proposed approach results in better detection performance than either standard energy detection or previous implementations of the GLRT detector.

Precious Locating Approach of the Beacon Based on Gray Gradient Segmentation Interpolation in Satellite Optical Communications

Qiang Wang, Yuefei Liu, YIQIANG CHEN, jing ma, Liying Tan, and Siyuan Yu

Doc ID: 274098 Received 19 Aug 2016; Accepted 25 Jan 2017; Posted 26 Jan 2017  View: PDF

Abstract: Accurate location computation for the beacon is an important guarantee for the reliability of satellite optical communications, however, the location precision is limited by the resolution of CCD in general. How to improve the location precision of the beacon is a very important and urgent issue. In this paper, we present two precious centroid computation methods for locating of the beacon in satellite optical communications. Firstly, In terms of its characteristics, the beacon is divided into several parts according to the gray gradients. Afterwards, different numbers of interpolation points and the different interpolation methods are applied in the interpolation area; we calculate the centroid position after interpolation, and choose the best strategy according to the algorithm. The method is called gradient segmentation interpolation approach, simply, GSI (gradient segmentation interpolation) algorithm. To take full advantages of the pixels of the beacon's central portion, we also present an improved algorithm-SSW (segmentation square weighting) algorithm whose effectiveness is verified by the simulation experiment. Finally, an experiment is established to verify GSI and SSW algorithms. The results indicate that GSI algorithm and SSW algorithm can improve locating accuracy than that calculated by traditional gray centroid method. These approaches help to greatly improve the location precision for the beacon in the satellite optical communications.

Determination of the spectral-dependent refractive index of a single layer in a natural multilayer system: comparison of different approaches

Diana Skigin, Marina Inchaussandague, Demetrio Macias, and Alexandre Vial

Doc ID: 281206 Received 21 Nov 2016; Accepted 25 Jan 2017; Posted 26 Jan 2017  View: PDF

Abstract: By means of heuristic optimization techniques, we estimate the unknown refractive index of one layer of a periodic natural multilayer system from far-field reflectance data. To take into account the dispersive characteristics of the material, we employ two different strategies. The first is based on the retrieval of Lorentz model-related parameters, to describe the unknown dielectric permittivity within a specific spectral range. The second strategy, based on a wavelength-by-wavelength approach, takes into account the reflectance values for each wavelength at a time. Through some examples, we compare the performance of both strategies when they look for the best estimates and analyze the error involved in each case. The applicability of both approaches to the case of noisy reflectance spectra is also explored.

Electrically tunable infrared filter based on a cascaded liquid-crystal Fabry-Perot for spectral imaging detection

qing tong, Jiuning Lin, yu lei, Zhaowei Xin, Dong Wei, Zhang Xinyu, Jing Liao, Haiwei Wang, and changsheng Xie

Doc ID: 279766 Received 14 Nov 2016; Accepted 12 Jan 2017; Posted 13 Jan 2017  View: PDF

Abstract: An electrically tunable infrared (IR) filter based on a key cascaded liquid-crystal Fabry-Perot (C-LC-FP) working in the wavelength range of 3-5 μm, is presented. The C-LC-FP is constructed by closely stacking two FP microcavities with different depth of 12 and 15 μm and fully filled by nematic LC materials. Through continuous wavelength selection of both microcavities, the radiation with high transmittance and narrow bandwidth can pass through the filter. According to the electrically controlled birefringence characteristics of nematic LC molecules, the transmission spectrum can be shifted through applying dual voltage signals over the C-LC-FP. Compared with common LC-FP with single microcavity, the C-LC-FP demonstrates better transmittance peak morphology and spectral selection performance. To be more specific, the number and the shifted scope of the IR transmission peak can be decreased and widened, respectively.

Measurement of thickness profiles of glass plates by analyzing Haidinger fringes

Myoungsik Cha, Ju Eun Park, and Jiung Kim

Doc ID: 280680 Received 11 Nov 2016; Accepted 05 Jan 2017; Posted 02 Feb 2017  View: PDF

Abstract: We report a novel method for measuring the thickness profiles of plane parallel plates by analyzing their Haidinger fringes. When an extended monochromatic source is viewed through a ~1-mm-thick plate, concentric transmission-type Haidinger fringes can easily be observed. Small variations in the plate thickness result in changes in the radii of the ring fringes. In this study, we scanned 25-mm-diameter fused silica and BK7 plates while tracing a specific ring in each fringe pattern to measure the thickness profiles of the plates, achieving an uncertainty of 2 nm in the measurements of the thickness differences between two locations on each plate.

Research on artificial dielectric material for millimeter-wave imaging application

Jinbang wang, Hanxue MEI, Kui Yang, Lu Zhao, zhiguo liu, and Tao Zhang

Doc ID: 282660 Received 12 Dec 2016; Accepted 04 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: Material made of artificial molecules fabricated from cage-shaped granules of conductor (CGC) is introduced and its electrical and magnetic characteristics are presented. Its refractive index, calculated using complex relative permittivity and complex relative permeability, is 1.504 at 35 GHz. A two-element lens, consisting of a pair of spherical plano-convex lenses, was designed and fabricated by embedding CGC in PMMA. The active millimeter-wave (AMMW) imaging system was constructed with the two-element lens by having the curved surfaces face each other. Millimeter-wave (MMW) images of a right trapezoid and twin bars were obtained. The image quality was acceptable, proving that the CGC material has the ability to refract MMWs in MMW imaging and that ability contrasts with that of some traditional high polymer material.

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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