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Accepted papers to appear in an upcoming issue

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Miniature endoscopic optical coherence tomography for calculus detection

Kao Meng-Chun, CHUN-LI LIN, CHE-YEN KUNG, YI-FUNG HUANG, and Wen-Chuan Kuo

Doc ID: 237590 Received 14 Apr 2015; Accepted 31 Jul 2015; Posted 31 Jul 2015  View: PDF

Abstract: Effective treatment of periodontitis involves the detection and removal of subgingival dental calculus. However, subgingival calculus is more difficult to detect than supragingival calculus because it is firmly attached to root surfaces within periodontal pockets. To achieve a smooth root surface, clinicians often remove excessive amounts of root structure because of decreased visibility. In addition, enamel pearl, a rare type of ectopic enamel formation on the root surface, can easily be confused with dental calculus in the subgingival environment. In this study, we developed a fiber-probe swept-source optical coherence tomography (SSOCT) technique and combined it with quantitative measurement of an optical parameter (standard deviation [SD] of the OCT intensity) to differentiate subgingival calculus from sound enamel, including enamel pearl. Two-dimensional circumferential images were constructed by rotating the miniprobe (0.9 mm diameter) while acquiring image lines, and the adjacent lines in each rotation were stacked to generate a three-dimensional volume. In OCT images, compared to sound enamel and enamel pearls, dental calculus showed significant differences (P < 0.001) in SD value. Finally, the receiver operating characteristic curve had a high capacity (area under the curve = 0.934) for discriminating between healthy regions (including enamel pearl) and dental calculus.

Optical identification based on time domain optical coherence tomography

Vishal Gandhi, Dmitry semenov, Seppo Honkanen, and Markku Hauta-Kasari

Doc ID: 240116 Received 30 Apr 2015; Accepted 31 Jul 2015; Posted 31 Jul 2015  View: PDF

Abstract: We present a novel method for optical identification, i.e., authenticating valuable documents such as passport, credit cards and bank notes, using optical coherence tomography (OCT). An OCT system can capture three dimensional (3D) images and visualize the internal structure of an object. In our work, as an object, we consider a multilayered optical identification tag composed of a limited number of thin layers (10-100 um thick). The thickness, width and location of the layers in the tag encode a unique identification information. Reading of the tag is done using a Time Domain OCT (TD-OCT) system. Typically, a TD-OCT system requires continuous mechanical scanning in one or more directions to get a 3D volume image of an object. The continuous scanning implies a complicated optical setup, which makes an OCT system fragile and expensive. We propose to avoid the conventional scanning by 1) not requiring 3D imaging and 2) utilizing the motion of the optical tag itself. The motion is introduced to the tag reader, for example, by a user, which replaces the need of conventional scanning. The absence of a conventional scanning mechanism makes the proposed OCT method very simple and suited for identification purposes; however, it also puts some constrains to the construction of the optical tag, which we discuss in this paper in detail.

Graphene-based electromagnetically induced transparency with coupling Fabry-Perot resonators

Fanmin Kong, Huawei Zhuang, Kang Li, and Shiwei Sheng

Doc ID: 241088 Received 18 May 2015; Accepted 31 Jul 2015; Posted 31 Jul 2015  View: PDF

Abstract: We investigate the plasmonic analog of electromagnetically induced transparency using two adjacent graphene-based Fabry-Perot resonators side-coupling to a nanoribbon waveguide. By the coupling mode theory and F-P resonant model, the destructive interference from the coupling of the two F-P resonators results in the EIT-like optical response. The induced peak and width of the transparency window can be dynamically manipulated by varying the coupling distance of the two resonators, and the transparent window is easily shifted by tuning the resonator length or the chemical potential of the graphene nanoribbon. In order to verify the characteristics of slow light, the group index profile is analyzed at different coupling distance. The proposed graphene-based EIT-like system could open up new opportunities for potential applications in plasmonic slow light and optical information buffering devices.

Strain and mechanical properties of VCM multi-layer sheet and their composites using digital speckle correlation method

De-hai ZHANG, Guizhong Xie, Jianxiu Liu, and Yanqin Li

Doc ID: 241733 Received 26 May 2015; Accepted 31 Jul 2015; Posted 31 Jul 2015  View: PDF

Abstract: Digital speckle correlation method (DSCM) is introduced to solve the challenging problems in the related geometric measurement. Theoretical calculations of strain are deduced using DSCM. Corresponding strains along x and y directions are obtained from uniaxial tension experiments and digital speckle measurements, using the VCM non-deep drawing multi-layer sheet, the VCM deep-drawing multi-layer, clad film, non-deep drawing substrate and deep-drawing substrate sheet as the targeted experimental objects. Results show that maximum strains along x direction of VCM non-deep drawing multi-layer sheet, the VCM deep-drawing multi-layer, clad film, non-deep drawing substrate and deep-drawing substrate sheet are 68.473%, 48.632%, 91.632%, 50.784% and 40.068%, respectively. While maximum strains along y direction are -2.657%, -15.381%, 2.826%, -9.780% and -7.783%, respectively. Mechanical properties of VCM multi-layer sheet are between those of the substrate and clad film, while mechanical properties of VCM deep-drawing multi-layer sheet are superior to those of the VCM non-deep drawing multi-layer sheet.

Study of the Impact of Truncations on Wedge Waves by Using Laser Ultrasound Technique

Jing Jia, Shen Zhong-Hua, and Kaihua Sun

Doc ID: 238051 Received 13 Apr 2015; Accepted 29 Jul 2015; Posted 30 Jul 2015  View: PDF

Abstract: This research focuses on measuring the impact of truncations on the dispersion characteristics of wedge waves propagating along wedge tip by using laser generated ultrasound. Firstly, finite-element method was used to simulate laser induced wedge waves and the dispersion curves were obtained by using 2D Fourier transformation method. Then pulsed laser excitation and laser-based wedge wave detection was built to investigate these characteristics experimentally. Take 20° and 60° line wedge for example, both experimental and numerical results indicate that non-ideal wedge tip has great impact on the wedge waves, the modes of 20° line wedge with truncations present anomalous dispersion, low mode closed to high mode in high frequency, and the characteristics of antisymmetric Lamb waves as the truncation increasing. Meanwhile, the modes of 60° line wedge with truncations appears the characteristics of antisymmetric Lamb waves, and the A1 mode are observed clearly. The study can be used to evaluate and detect wedge structure.

Femtosecond pulsed laser ablation of Polyimide at oblique angles for medical applications

Khan Alam, Bibi Safia Haq, Hidayat Khan, Mian Mateenullah, Islam Zari, and Shehnaz Attaullah

Doc ID: 238264 Received 27 Apr 2015; Accepted 29 Jul 2015; Posted 30 Jul 2015  View: PDF

Abstract: We report the ablation results for surface modification of polyimide Kapton (HN) foils using ultra short femtosecond laser pulses. The modification threshold fluences for 75μm thick films of polyimide were determined at different incident angles (0o, 20o, 30o, 45o and 50o) for vertical and horizontal diameters. Ablation at oblique angles was investigated as such interactions are found during the laser procedure with the eye that require scanning of the beam, and are very important to know for the treatment of various eye deseases. Polyimide, in this study, was considered as a model for corneal sculpting. Use of ultra short femtosecond laser pulses for high precision patterning of the sample, without thermal damage to the surroundings has been investigated. The relationship between the incidence angle with ablation threshold fluence, threshold energy and beam radius are described. Also threshold energies and threshold fluences for different thicknesses of poyimide were investigated.

Design of a Pentagonal Photonic Crystal Fiber with High Birefringence and Large Flattened Negative Dispersion

Pan Liu, Zhenlong Xu, Xu-You Li, and Zhiyong Zhang

Doc ID: 237552 Received 10 Apr 2015; Accepted 28 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: A novel pentagonal photonic crystal fiber with high birefringence, large flattened negative dispersion and high nonlinearity is proposed. The dispersion and birefringence properties of this structure is simulated and analyzed numerically based on the full vector finite element method (FEM). Numerical results indicate that the fiber obtains large average dispersion of -611.9 ps/nm/km over 1460-1625 nm and –474 ps/nm/km over 1425-1675 nm wavelength bands for two kinds of optimized design, respectively. In addition, the proposed PCF shows a high birefringence of 0.0167 and 0.0175 at the operating wavelength 1550 nm, respectively. Moreover, the influence of the possible variation in the parameters during the fabrication process on the dispersion and birefringence properties is studied. The proposed PCF would have important applications in polarization maintaining transmission system, residual dispersion compensation, super-continuum generation and the design of widely tunable wavelength converter based on four-wave mixing.

(NRL) Simulation of free-space optical guiding structure based on colliding gas flows

Dmitri Kaganovich, John Palastro, Yu-hsin Chen, Daniel Gordon, Michael Helle, and Antonio Ting

Doc ID: 241541 Received 26 May 2015; Accepted 28 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: Preformed plasma channels with parabolic radial density profiles enable the extended and stable optical guiding of high intensity laser pulses. High voltage discharge capillaries, commonly used for channel formation, have limited guiding length and opaque walls, complicating diagnosis of the plasma within. In this paper we propose a free-space gas channel produced by the collision of several gas flows. The collision of the gas flows forms an on-axis density depression surrounded by higher density walls. Once ionized, the resulting plasma density profile has a near-parabolic dependence ideal for guiding. Detailed 2-D fluid dynamics simulations are performed to examine the properties and stability of the guiding structure.

(NRL) Suspended Photonic Waveguide Devices

Todd Stievater, Marcel Pruessner, William Rabinovich, Doewon Park, Rita Mahon, Dmitry Kozak, J Boos, Scott Holmstrom, and Jacob Khurgin

Doc ID: 241842 Received 27 May 2015; Accepted 28 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: This article describes recent research at the U. S. Naval Research Laboratory that focuses on the use of micro- and nano-machining techniques for photonic waveguide devices. By selectively etching a sacrificial layer that the waveguide core is supported by, in whole or in part, the waveguide obtains enhanced properties and functionality, such as mechanical flexibility, index contrast, birefringence, or evanescent field depth. We describe how these properties enable unique waveguide applications in areas such as cavity optomechanics, displacement sensing, electro-optics, and nonlinear optics.

(NRL) Refractive Index Measurements of Poly(methyl methacrylate) (PMMA) from 0.4-1.6 μm

Guy Beadie, Michael Brindza, Richard Flynn, Armand Rosenberg, and James Shirk

Doc ID: 242083 Received 01 Jun 2015; Accepted 28 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: Using a transmission-spectrum-based method, the refractive index of a 50-micron-thick sample of PMMA was measured as a function of wavelength. To mitigate the effects of non-plane-parallel surfaces, the sample was measured at 16 different locations. The technique resulted in the measurement of index at several thousand independent wavelengths from 0.42-1.62 microns, with a relative RMS accuracy < 0.5x10-4 and absolute accuracy < 2x10-4.

Millijoule femtosecond micro-Bessel beams for ultra-high aspect-ratio machining

David Grojo, Sambit Mitra, Margaux Chanal, Raphaël CLADY, and Alexandros Mouskeftaras

Doc ID: 243407 Received 19 Jun 2015; Accepted 28 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: We report on a functional experimental design for Bessel beam generation capable of handling high energy ultrashort pulses (up to 1.2 mJ per pulse of 50 fs duration). This allows us to deliver intensities exceeding the breakdown threshold for air or any dielectric along controlled micro-filaments with lengths exceeding 4 mm. It represents an unprecedented up-scaling in comparison to recent femtosecond Bessel beam micromachining experiments. We produce void microchannels through glass substrates to demonstrate that aspect ratios exceeding 1200:1 can be achieved by using single high-intensity pulses. This demonstration must lead to new methodologies for deep-drilling and high-speed cutting applications.

A novel pseudo-cat’s eye for improved mirror-tilt-free interferometry

Miranda Bradshaw and C Speake

Doc ID: 236884 Received 25 Mar 2015; Accepted 28 Jul 2015; Posted 29 Jul 2015  View: PDF

Abstract: We present a new simple optical design for a cat’s eye retroreflector. We describe the design of the new cat’s eye and its use in tilt-immune interferometry. In this application a cat’s eye is integrated into an interferometer to enable the tracking of the displacement of a plane target mirror with minimum sensitivity to its tilt about axes orthogonal to the interferometer’s optical axis. The new design allows, for the first time, tilt-immune interferometric displacement measurements in cases where the nominal distance to the target mirror is significantly larger than the scale of the cat’s eye. The new optical scheme is not a perfect cat’s eye but in practice behaves essentially as one; we therefore refer to it as a ‘pseudo’ cat’s eye. In this paper we describe the characteristics of the pseudo cat’s eye and compare its performance with a conventional cat’s eye optical configuration using ABCD matrices and Zemax analyses. We further suggest a simple modification to the design that would enable the pseudo-cat’s eye to behave as a perfect cat’s eye, and this design may provide an acceptable solution for other applications.

A New Robust Commercial DIffuse Reflector for UV-VIS-NIR Applications

John Mason, Michael Cone, Matthew Donelon, Jeffrey Wigle, Gary Noojin, and Edward S. Fry

Doc ID: 241524 Received 29 May 2015; Accepted 28 Jul 2015; Posted 29 Jul 2015  View: PDF

Abstract: We report the development and testing of a new commercially available diffuse reflecting material with reflectivities in the visible comparable to industry leading products. This new diffuse reflector consists of solid quartz in which there is a dense distribution of tiny pockets of air. The multiple reflections by the quartz-air interfaces of these air pockets transforms a highly transmisssive base material into a highly diffuse reflecting material.

Phase sensitivity to temperature of the guiding mode in polarization maintaining photonic crystal fiber

Sun Kang, Song Jingming, Li Shuai, and Cai Wei

Doc ID: 242104 Received 01 Jun 2015; Accepted 28 Jul 2015; Posted 29 Jul 2015  View: PDF

Abstract: The propagating phase changing of polarization maintaining-photonic crystal fiber (PM-PCF) caused by temperature variation is theoretically studied, as well as compared with conventional PANDA fiber. As to verifying numerical analysis, a platform based on Michelson interferometer for phase vs. temperature measurement was built for both kinds of fiber. Experiments show that PM-PCF has similar temperature sensitivity with conventional polarization maintaining fiber. With optimized PM-PCF design (thinner coating layer and coating material with smaller thermal expansion coefficient), the sensitivity could be further reduced to about 80% of the present level.

Fabrication, characterization and applications of microlenses

Anming Hu, Tingxiu Hou, chong zheng, Shi Bai, Qian Ma, Denzel Bridges, and Walter Duley

Doc ID: 237955 Received 13 Apr 2015; Accepted 27 Jul 2015; Posted 30 Jul 2015  View: PDF

Abstract: Microlenses (MLs) and microlense arrays (MLAs) are assuming an increasingly important role in optical devices. In response to this rapid evolution in technology, emphasis is being placed on research into new manufacturing methods for these devices as well as the characterization of their performance. This paper provides an overview of the fabrication of MLs and MLAs by electrical, mechanical, chemical and optical methods. As each processing method has distinct advantages and limitations, the most significant characteristic parameters and the measurement of these parameters are discussed for each method. These parameters are then used as indices to evaluate and improve each of the processing methods. Some examples of practical applications of MLAs, especially for micro-mechanical optoelectronic devices, are also given. This paper aims to summarize the present development and the state of the art in processing technology of MLs and MLAs.

Dual-view angle backlight module design

Jui Wen Pan and Bo Tsuen Chen

Doc ID: 240592 Received 15 May 2015; Accepted 27 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: We propose a bilayer light guide plate (BLGP) with specially designed microstructures and two light source modules to achieve an adjustable viewing angle backlight for eco-friendly display. The dual viewing angle backlight module has a thin, simple structure and high optical efficiency. Comparison with the conventional edge-lit backlight module shows an improvement in the on-axis luminance of the narrow viewing angle mode of 4.3-times and a decrease in the half-luminance angle of 7 degrees in the horizontal direction. When using the wide viewing angle mode, there is an improvement in the on-axis luminance of 1.8-times and an improvement in the half-luminance angle of 54 degrees in the horizontal direction. The uniformity of illuminance can reach 80% in each mode. The backlight optical sheet number is reduced from 5 to 1.

Optical and Thermal Design of LED Omnidirectional Bulb

ZhiTing Ye, Hao-chung Kuo, and Cheng-Huan Chen

Doc ID: 240927 Received 13 May 2015; Accepted 27 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: The penetration of LED light bulbs into lighting market is growing quickly in the recent years due to significant increase of LED efficiency and reduction of cost. One major issue to be improved is the overall light bulb efficiency, which can fulfill “Energy Star for Lamps” while meeting the specification of omnidirectional bulb. The efficiency issue results mainly from the high directionality of the LED sources and the corresponding solutions to make the emission more diverse. In this article, a diffusion white reflection sheet(DWRS) with an array of hole is proposed as a high efficiency solution for modulating light emission profile with SMD type LED source. The hole size is adjusted with fixed hole pitch to both maximize the efficiency and meet the omnidirectional specification. In addition, the concept of thermal plastic insert molding metal is proposed for thermal management without fins for cooling part. The prototype demonstrates an efficiency of 87.6% and LED pad temperature of 85oC, which shows the feasibility as a total solution for high efficiency LED omnidirectional bulb.

Silicon hybrid plasmonic microring resonator for sensing applications

meng zhang, genzhu wu, and Daru Chen

Doc ID: 241788 Received 27 May 2015; Accepted 27 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: A novel silicon hybrid plasmonic microring resonator consisting of a silver nanoring on top of a silicon-on-insulator (SOI) ring is proposed and investigated theoretically for possible applications in sensing at deep sub-wavelength scale. By using the finite-element method (FEM), an insight of the mode properties (Q factor, the effective mode volume, energry ratio, sensitivity) depend on the geometric structure of the hybrid microring resonator is presented. Simulation results reveal that this kind of hybrid microcavity maintains high Q factor ~ 600, ultra-small mode volume of 0.15 µm3and high sensitivity of 497 nm/RIU(reflactive index unit) for reflactive index sensing. The presented hybrid plasmonic microcavity with optimized geometric structures provides the potential to ultra-compact sensing applications.

(NRL) Infrared photothermal imaging spectroscopy for detection of trace explosives on surfaces

Chris Kendziora, Robert Furstenberg, Michael Papantonakis, Viet Nguyen, Jeff Byers, and R. McGill

Doc ID: 242081 Received 29 May 2015; Accepted 27 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: We are developing a technique for the stand-off detection of trace explosives on relevant substrate surfaces using photo-thermal infrared (IR) imaging spectroscopy (PT-IRIS). This approach leverages one or more compact IR quantum cascade lasers, tuned to strong absorption bands in the analytes and directed to illuminate an area on a surface of interest. An IR focal plane array is used to image the surface and detect small increases in thermal emission upon laser illumination. The PT-IRIS signal is processed as a hyperspectral image cube comprised of spatial, spectral and temporal dimensions as vectors within a detection algorithm. The ability to detect trace analytes on relevant substrates is critical for stand-off applications, but is complicated by the optical and thermal analyte/substrate interactions. This manuscript describes a series of PT-IRIS experimental results and analysis for traces of RDX, TNT, ammonium nitrate (AN) and sucrose on relevant substrates (steel, polyethylene, glass and painted steel panels). We demonstrate detection at relevant surface mass loadings (10 µg/cm2 to100 µg/cm2) from an area corresponding to a single pixel within the thermal image.

Surface measurement of indium tin oxide thin film by wavelength-tuning Fizeau interferometry

YANGJIN KIM, Kenichi Hibino, Naohiko Sugita, and Mamoru Mitsuishi

Doc ID: 243494 Received 22 Jun 2015; Accepted 27 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: Indium tin oxide (ITO) thin films have been widely used in displays such as liquid crystal displays and touch panels because of their favorable electrical conductivity and optical transparency. The surface shape and thickness of ITO thin films must be precisely measured to improve their reliability and performance. Conventional measurement techniques take single point measurements and require expensive systems. In this paper, we measure the surface shape of an ITO thin film on top of a transparent plate using wavelength-tuning Fizeau interferometry. The surface shape was determined by compensating for the phase error introduced by optical interference from the thin film, which was calculated using the phase and amplitude distributions measured by wavelength-tuning. The proposed measurement method achieved non-contact, large-aperture, and precise measurements of transparent thin films. The surface shape of the sample was experimentally measured to an accuracy of 5.13 nm.

Aspherical Lens Design Using Hybrid Neural-Genetic Algorithm of Contact Lenses

Chih-Ta Yen and Jhe-Wen Ye

Doc ID: 241126 Received 15 May 2015; Accepted 27 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: The design of complex contact lenses involves numerous uncertain variables. How to help optical designer first to design the optimal contact lens to reduce discomfort when wearing a pair of glasses is an essential design concern. This study examined the impact of aberrations on contact lenses to optimize a contact lens design for myopic and astigmatic eyes. In general, two aspherical surfaces can be assembled in an optical system to reduce the overall volume size. However, this design reduces the spherical aberration (SA) values at wide contact radii. The proposed optimization algorithm with optical design can be corrected to improve the SA value and, thus, reduce coma aberration (TCO) values and enhance modulation transfer function (MTF). It means integrating a modified genetic algorithm (GA) with a neural network (NN) to optimize multiple quality characteristics, namely the SA, TCO, and MTF, of contact lenses. When the proposed optional weight NN-GA algorithm is implemented, the weight values of the fitness function can be varied to adjust system performance. The method simplifies the selection of parameters in the optimization of optical systems. Compared with the traditional CODE V built-in optimal scheme, the proposed scheme is more flexibility and intuition to improve SA, TCO, and MTF values by 50.03%, 45.78%, and 24.7%, respectively.

Precise autofocus method employing normalized fluorescence image size in a two-photon polymeriza-tion nanofabrication system

Byoung Goo Jeon, Yong Hoon Cho, Hong Jin Kong, and Byung Je Jung

Doc ID: 240488 Received 25 May 2015; Accepted 27 Jul 2015; Posted 30 Jul 2015  View: PDF

Abstract: An autofocus method has been investigated to improve the precise positioning of a substrate surface at the center of the laser focal spot in two photon polymerization (TPP) nanofabrication. For this purpose, we developed a novel autofocus method using normalized image size, which was calculated with the second momentum radius (SMR) of two-photon induced fluorescence (TPIF). The SMR of TPIF was theoretically analyzed and experimentally compared with the average intensity of TPIF for various input laser powers. The results show that the proposed method enhanced the precision and robustness of autofocus in TPP. Specifically, the experimental creation of ascending voxel arrays demonstrated both the method’s immunity to input laser power change, and a high precision of ± 0.045 μm. To test the practical feasibility of the proposed autofocus method, 300 μm x 260 μm single layer honey-comb structures were successfully fabricated with precompensation and dynamic compensation using the proposed autofocus method.

Laser echo signal amplification in a turbulent atmosphere

Victor Banakh, Igor Razenkov, and Igor Smalikho

Doc ID: 237553 Received 03 Apr 2015; Accepted 27 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: The lidar system for registration of a laser return amplification arising in a turbulent atmosphere due to the backscatter amplification effect is considered in the paper. In the system two receiving channels are used. One of them (axial) coincides with the transmitter channel, while another channel (nonaxial) receives the backscattered radiation at a small angle to the probing beam axis. The ratio of power of the echo signal recorded in the axial channel to that recorded in the nonaxial one is a measure of the return amplification. The results of long duration lidar atmospheric experiments show that the power of the echo signal registered in the axial channel usually exceeds that in the nonaxial one.

Accurate estimation of the backscattering coefficient by light scattering at two backward angles

Tomohiko Oishi, Hiroyuki Tan, Akihiko Tanaka, and Roland Doerffer

Doc ID: 239851 Received 01 May 2015; Accepted 27 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: Backscattering coefficients are frequently estimated from light scattering at one backward angle multiplied by a conversion factor. We elucidated that the shape of the volume scattering functions (VSFs), particularly for scattering angles larger than 170˚, cause significant variations in the conversion factor at 120˚. Our approach uses the ratio of scattering at 170˚ and at 120˚, which is a good indicator of the shape differences of VSFs for most oceanic waters and wavelengths in the visible range. The proposed method provides significant accuracy improvement in the determination of the backscattering coefficients with a prediction error of 3% of the mean.

Three-dimensional imaging through scattering media using three-dimensionally coded pattern projection

Takamasa Ando, Ryoichi Horisaki, and Jun Tanida

Doc ID: 238369 Received 20 Apr 2015; Accepted 26 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: We propose a method for visualizing three-dimensional objects in scattering media. Our method is based on active illumination using three-dimensionally coded patterns and a numerical algorithm employing a sparsity constraint. We experimentally demonstrated the proposed imaging method for test charts located threedimensionally at dierent depths in the space behind a translucent sheet.

Reducing the coherent noise in the interference systems using phase modulation technique

Zhaobo Liu, Jiwen Cui, Zhang Tao, and Jiubin Tan

Doc ID: 237498 Received 20 Apr 2015; Accepted 26 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: The phase modulation technique is adopted to reduce the coherent noise which arises from the spurious interference. By choosing an appropriate driving signal, the method can reduce the coherent function of coherent noise to a great degree while maintaining the coherent function of coherent signal nearly unchanged. Simulation results show that for the grating interferometer, the phase error caused by coherent noise is averagely reduced by 81.53%, and for the Twyman interferometer, the fringe quality and contrast deteriorated by coherent noise are significantly improved. Furthermore, an experiment is set up in the phase modulated Twyman Interferometer to verify the feasibility of the principle. It is concluded that the method is effective to reduce the coherent noise in interference systems.

Least Squares Fitting of Hartmann or Shack-Hartmann Data with a Circular Array of Sampling Points

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

Doc ID: 240999 Received 14 May 2015; Accepted 24 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: A least squares procedure to find the tilts, curvature, astigmatism, coma and triangular astigmatism by means of measurements of the transverse aberrations, using a Hartmann or Shack-Hartmann test is described. The sampling points are distributed in a ring centered on the pupil of the optical system. The properties and characteristics of rings with three, four, five, six or more sampling points are analyzed with more detail and better mathematical analysis than in previous publications.

Improving the color uniformity of multiple colored LEDs by using periodic microstructure surface

Shang-Ping Ying, Chao-Ying Lin, and Chih-Cheng Ni

Doc ID: 241011 Received 15 May 2015; Accepted 24 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: This study proposes the performance of the periodic microstructure surface on multiple colored LEDs. The periodic microstructure surface on the package was used to reshape the light from the different colored LED chips in the multiple colored LEDs, and then decreased the color separation and spatial color variation of multiple colored LEDs. Experimental results show that the multiple colored LEDs with periodic microstructure surface could provide a medium or high collimation as well as good color uniformity. Thus, this study provides a simple and cost-effective method to greatly improve the color uniformity of multiple colored LEDs with medium or high collimation.

Near-infrared imaging system for nondestructive inspection of micro-crack in wafer through dicing tape

Sheng-Feng Lin, Cheng-Huan Chen, and Cheng-Yao Lo

Doc ID: 241065 Received 15 May 2015; Accepted 24 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: Detection of wafer/die crack after wafer dicing process is important for yield rate control prior to packaging. Traditional approach of microscopic examination is done after the dies are stripped from the dicing tape, and further crack propagation could be resulted in this pick-and-place process. An on-tape crack inspection technique is proposed in this paper so that the crack from the dicing process can be clearly identified. The issues of seeing through silicon substrate and the scattering at the dicing type have been resolved respectively with using nearinfrared wavelength of 1100 nm for illumination and feeding index matching liquid for filling the rough surface of the tape. Both the illumination and imaging optics of the inspection system have been designed and simulated with ray tracing program, and the prototype demonstrates the ability of seeing through silicon substrate and dicing type as well as detecting micro-crack down to 1.25μm, whose resolution is sufficient for most application of die crack inspection.

(NRL) Spatial Heterodyne Spectroscopy at the Naval Research Laboratory

Christoph Englert, Charles Brown, John Mark Harlander, and Kenneth Marr

Doc ID: 241529 Received 26 May 2015; Accepted 24 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: Spatial Heterodyne Spectroscopy (SHS) is based on traditional Michelson interferometry. However, instead of employing retro-reflectors in the interferometer arms, one or both of which are moving, it uses fixed, tilted diffraction gratings and an imaging detector to spatially sample the optical path differences. This concept allows high resolution, high throughput spectroscopy without moving interferometer parts, particularly suitable for problems that require compact, robust instrumentation. Here, we briefly review about 20 years of ground- and space-based SHS work performed at the U.S. Naval Research Laboratory (NRL), which started with a visit of Prof. Fred Roesler to NRL in 1993.

(NRL) Ultrafast Z-Scan measurements of nonlinear optical constants of window materials at 772 nm, 1030 nm, and 1550 nm

Steven Flom, Guy Beadie, Jason Auxier, Shayam Bayya, and Brandon Shaw

Doc ID: 242086 Received 01 Jun 2015; Accepted 24 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: Femtosecond Z-Scan measurements have been performed on six window materials at 772, 1030 and 1550 nm. Measurements of the nonlinear refractive index are presented for reference materials, Fused Silica and BK7 and four near infrared window materials, multispectral ZnS (CLEARTRAN®), Aluminum Oxynitride (AlON), Spinel (MgAl2O4) ceramic, and Barium GalloGermanate (BGG) glass.

Design of multi-segmented freeform lens for LED fishing/working lamp with high efficiency

MIN-FENG LAI, NGUYEN DOAN ANH, JIA-ZHI GAO, Hsin Ma, and Hsiao-Yi Lee

Doc ID: 240929 Received 15 May 2015; Accepted 23 Jul 2015; Posted 23 Jul 2015  View: PDF

Abstract: A novel LED fishing/working light is proposed for enhancing the lighting efficiency of a fishing boat. The study is focused on the freeform secondary lens design for creating a lamp to attract fishes and shine light on the deck for fishing work. The experimental results show that the proposed multi-segmented freeform lens (MSFL) can accomplish the proposed light three times illuminance more than that of the traditional HID fishing lamp under the same input electrical power.

Investigation of fringing electric field effect on high resolution blue phase liquid crystal spatial light modulator

Qing Li, Jing Yan, Zhengbo Guo, and Yufei Xing

Doc ID: 242512 Received 08 Jun 2015; Accepted 22 Jul 2015; Posted 22 Jul 2015  View: PDF

Abstract: The fringing electric field effect which determines the performance of a high resolution blue phase liquid crystal spatial light modulator (BPLC-SLM) is investigated by numerical modeling. The BPLC-SLM is polarization dependent due to the transverse electric field component. The physical mechanism of the phase profile properties for different polarization states is analyzed. General design issues related to the BPLC-SLM configuration and phase profile properties are discussed. Notably, the material parameters and cell gap thickness are both optimized to obtain a low operation voltage (V2π=26.07V). This work provides fundamental understanding for the feasibility of low operation voltage and high spatial resolution BPLC-SLM.

Mineralogy and astrobiology detection using laser remote sensing instrument

M. Nurul Abedin, Arthur Bradley, Shiv Sharma, Anupam Misra, Paul Lucey, Christopher McKay, Syed Ismail, and Stephen Sandford

Doc ID: 239768 Received 14 May 2015; Accepted 22 Jul 2015; Posted 22 Jul 2015  View: PDF

Abstract: The multi-spectral instrument based on Raman, Laser Induced Fluorescence (LIF), Laser Induced Breakdown Spectroscopy (LIBS), and Lidar system provides high-fidelity scientific investigations, scientific input, and science operations constraints in the context of planetary field campaigns with the Jupiter Europa Robotic Lander and Mars Sample Return (MSR) mission opportunities. It does this by conducting scientific investigations analogous to investigations anticipated for missions to Mars and Jupiter’s Icy Moons. This combined multi-spectral instrument is capable of performing Raman and fluorescence spectroscopy out to a >100-meter target distance from the rover system and provides single-wavelength atmospheric profiling over long ranges (>20 km). In this article, we will reveal an integrated remote Raman, LIF, and Lidar technologies for use in robotic and lander based planetary remote sensing applications. Discussions are focused on recently developed Raman, LIF, and lidar system in addition to emphasizing on surface water ice, surface and subsurface minerals, organics, biogenic, and biomarkers identification and atmospheric aerosols and clouds distributions, i.e., near-field atmospheric thin layers detection for next robotic-lander based instruments to measure all the above-mentioned parameters.

Gradient-based Inverse Extreme Ultraviolet Lithography

Xu Ma, Jie Wang, Xuanbo Chen, Yanqiu Li, and Gonzalo Arce

Doc ID: 240207 Received 04 May 2015; Accepted 22 Jul 2015; Posted 23 Jul 2015  View: PDF

Abstract: Extreme ultraviolet (EUV) lithography is the most promising successor of current deep ultraviolet (DUV) lithography. The very short wavelength, reflective optics and non-telecentric structure of EUV lithography systems bring in different imaging phenomena into the lithographic image synthesis problem. This paper develops a gradient-based inverse algorithm for EUV lithography systems to effectively improve the image fidelity by comprehensively compensating the optical proximity effect, flare, photoresist and mask shadowing effects. A block-based method is applied to iteratively optimize the main features and sub-resolution assist features (SRAF) of mask patterns, while simultaneously preserving the mask manufacturability. The mask shadowing effect may be compensated by a retargeting method based on a calibrated shadowing model. Illustrative simulations at 22nm and 16nm technology nodes are presented to validate the effectiveness of the proposed methods.

Objective Shearing Digital Holography for Removing Aberration from Optical System

pan weiqing, Kehan Tian, and Chuhang Zhang

Doc ID: 240230 Received 04 May 2015; Accepted 22 Jul 2015; Posted 30 Jul 2015  View: PDF

Abstract: We propose a new digital holography based on the lateral shearing interference concept to remove the total aberrations from the reference wave, illumination wave and the optical elements. It uses of three mutually shifted image holograms of the object, which are divided from each other to obtain phase differences. By the phase differences, the phase aberration can be removed and the original sample phase can be reconstructed. Then the influence of the stage moving imprecision on the reconstruction quality is analyzed. Optical experiments have been carried out. It verified that the proposed method can totally remove the phase aberrations. As a result, the proposed method could be used to ultra-precise optical measurement through eliminating optical phase aberration to increase the measurement accuracy.

Optimal design of tilt carrier frequency computer-generated holograms to measure aspherics

Jiantao Peng, Zhe Chen, Xingxiang Zhang, Jianyue Ren, and Tianjiao Fu

Doc ID: 241063 Received 15 May 2015; Accepted 21 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: Computer-generated holograms (CGHs) provide an approach to high-precision metrology of aspherics. A CGH is designed under the trade-off among the size, the mapping distortion and the line spacing. This paper describes an optimal design method based on the parametric model for tilt carrier frequency CGHs placed outside the interferometer focus points. Under the condition of retaining an admissible size and a tolerable mapping distortion, the optimal design method has two advantages: (1) separating the parasitic diffraction orders to improve the contrast of the interferograms; (2) achieving the largest line spacing to minimize sensitivity to fabrication errors. This optimal design method is applicable to common concave aspherical surfaces and illustrated with CGH design examples.

A high temperature strain sensor based on fiber Bragg grating and rhombus metal structure

liang zhang, Xiaoliang Gao, Liu Yueming, and Zhongcheng Xia

Doc ID: 238346 Received 20 Apr 2015; Accepted 21 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: In this paper, a novel high temperature strain sensor based on polyimide-coated fiber Bragg grating (FBG) and rhombus metal structure is presented and experimentally demonstrated. By heating the low softening point glass via a micro torch, the polyimide-coated FBG could be fixed into the rhombus metal structure. Consequently, when the rhombus structure is stretched and compressed respectively, then the FBG will be subjected to a reverse state. Moreover, the strain sensitivity is controllable and enhanced by adjusting the dimension of rhombus metal structure appropriately. Experiment was then carried out by using an equi-intensity cantilever beam and high temperature chamber and the result showed that the proposed high temperature strain sensor could be used at high temperature of 300℃. A resolution of ~10µε has been experimentally achieved. The average wavelength-strain sensitivity at 300℃ is 1.821pm/µε and 1.814pm/µε, for compress and stretch state, respectively.

BACKSCATTER NEAR-END SOLUTION IN PROCESSING OF SCANNING LIDAR DATA

Vladimir Kovalev, Cyle Wold, Alexander Petkov, and Wei Min Hao

Doc ID: 240069 Received 29 Apr 2015; Accepted 21 Jul 2015; Posted 22 Jul 2015  View: PDF

Abstract: The significant issue of the classic multiangle data-processing technique is that the upper height, up to which this technique allows the reliable profiling of the searched atmosphere, is always significantly less than the maximum operative range of the scanning lidar signals. The existing multiangle inversion methodology does not allow the proper inversion of the distant range signals measured in and close to zenith into the optical profiles. In this study, the data processing technique is considered which allows increasing the maximal heights when profiling of the atmosphere with scanning lidar by using the auxiliary backscatter near-end solution. Simulated and experimental data are presented that illustrate the specifics of such a combined technique. The technique can also be useful for processing the data of the zenith directed lidar.

On-orbit calibration of VIIRS reflective solar bands and its challenges using a solar diffuser

Junqiang Sun and Menghua Wang

Doc ID: 242099 Received 01 Jun 2015; Accepted 21 Jul 2015; Posted 22 Jul 2015  View: PDF

Abstract: The reflective solar bands (RSB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) on board the Suomi National Polar-orbiting Partnership (SNPP) satellite is calibrated by a solar diffuser (SD) panel whose performance is itself monitored by an accompanying solar diffuser stability monitor (SDSM). In this comprehensive work we describe the SD-based calibration algorithm of the RSB, analyze the calibration data, and derive the performance result, the RSB calibration coefficients or F-factors, for the current three years of mission. The application of the newly derived product of the SD bidirectional reflectance factor and the vignetting function for the SD screen and the newly derived SD degradation, so-called H-factors, effectively removes the artificial seasonal patterns in the RSB calibration coefficients. The full illumination region, the “sweet spot”, during calibration events for SD view is carefully examined and selected to ensure high data quality and to reduce noise owing to non-fully illuminated samples. A time-dependent relative spectral response (RSR), coming from the large out-of-band contribution and the VIIRS optical system wavelength-dependent degradation, is derived from an iterative approached and applied in the SD calibration for each RSB. The result shows that VIIRS RSB degrades much faster at near-infrared (NIR) and shortwave infrared (SWIR) wavelength range due to the faster degradation of the rotating telescope assembly (RTA) against the remaining part of the system. The gains of the VIIRS RSB have degraded 2.0% (410 nm, Band M1), 0.2% (443 nm, Band M2), -0.3% (486 nm, Band M3), 0.2% (551 nm, Band M4), 6.2% (640 nm, Band I1), 11.0% (671 nm, Band M5), 21.3% (745 nm, Band M6), 35.8% (862 nm, Band I2), and 35.8% (862 nm, Band M11), respectively, since launch and 24.8% (1238 nm, Band M8), 18.5% (1378 nm, Band M9), 11.5% (1610 nm, Band I3), 11.5% (1610, Band M10), and 4.0% (2250 nm, Band M11), respectively, since January 20 2012. It is established that the SD calibration accurately catches the on-orbit RSB degradation as according to the instrument design and the calibration algorithm. However, due to the inherent non-uniform degradation of the SD affecting especially the short wavelength bands and the lack of capability of the SDSM calibration to catch degradation beyond 935 nm, the direct and the unmitigated application of the SD calibration result will introduce non-negligible error into the calibration coefficients resulting in long-term drifts in the sensor data records (SDR) and consequently the high-level products. We explicitly unveil the effect of the non-uniformity in SD degradation in the RSB calibration coefficients but also briefly discuss a critical yet simple mitigation to restore the accuracy of the calibration coefficients base on lunar observations. The presented methodology thus remains intact as the corner stone of the RSB calibration and our derived RSB calibration coefficients represents the optimal result. This work has the most impact on the quality of the ocean color products that sensitively depend on the moderate visible (VIS) and NIR bands (M1-M7), as well as SWIR bands (M8, M10, and M11).

Wavelength Dependence for Silicon-Wafer Temperature Measurement by Autocorrelation-type Frequency-Domain Low-Coherence Interferometry

takayoshi tsutsumi, takayuki ohta, keigo takeda, masafumi ito, and masaru hori

Doc ID: 236880 Received 24 Mar 2015; Accepted 21 Jul 2015; Posted 21 Jul 2015  View: PDF

Abstract: We investigated silicon wafer temperature measurement characteristics based on optical low-coherence interferometry by altering the light source wavelength. Variations in Si wafer optical thickness with temperature are expressed by thermal expansion and the refractive index. The optical characteristics determine the measurement precision and range. In this study, the measurement precision and the measurable temperature range were evaluated for three wavelengths of 1040, 1310, and 1550 nm. The maximum measurable temperature at 1040 nm was the lowest because of signal light absorption caused by fundamental interband absorption. The measurement precision at 1040 nm was the highest at 0.020°C because optical thickness changes per degree C increase with decreasing wavelength.

560 W all fiber and polarization-maintaining amplifier with narrow linewidth and near-diffraction-limited beam quality

Yang Ran, Rumao Tao, Pengfei Ma, Xiaolin Wang, Rongtao Su, Pu Zhou, and Lei Si

Doc ID: 240640 Received 11 May 2015; Accepted 21 Jul 2015; Posted 21 Jul 2015  View: PDF

Abstract: We present a narrow linewidth, all fiber polarization-maintained (PM) amplifier chain seeded by a phase modulated single-frequency laser. Different from previous phase modulation techniques, the phase modulation signal is generated by simply imposing an excite signal to an acoustic-optical driven source (AODS). Theoretical simulation results show that this way can suppress SBS to some better degree, and the output power can be boosted to about 1.2 kW in terms of the stimulated Brillouin scattering (SBS) threshold. In experiment, by amplifying the phase modulated seed based on master oscillator power amplification (MOPA) configuration, a 560W output laser is achieved with slope efficiency of 87.2% and linewidth of <5 GHz. Further power scaling is limited by mode instability (MI) instead of SBS effect. At maximal output power, the beam quality (M2 factor) and polarization extinction ratio (PER) is respectively measured to be within 1.3 and 14 dB.

Measurement of Lithium Isotope Ratio in various concentration samples using Degenerate Four-wave Mixing

Xunli Yin, Xuemei Cheng, Ying Zhang, Haowei Chen, Jintao Bai, and Zhaoyu Ren

Doc ID: 237519 Received 03 Apr 2015; Accepted 21 Jul 2015; Posted 22 Jul 2015  View: PDF

Abstract: Phase-conjugate degenerate four-wave mixing (PCDFWM), as a sub-Doppler spectroscopy technique, can be employed to selectively analyze Li isotopes. It is necessary to explore the optimal incident powers in order to measure Li isotope ratio accurately. In this case, the power condition of PCDFWM signal is firstly investigated using the samples with various concentrations. The results indicate that the power characteristic is intimately related to the sample concentration, and the optimal incident power conditions for different sample concentrations are different. Under their own optimized power conditions, we measured 7Li/6Li isotope ratio in Li standard solution of 500 ng/mL, 300 ng/mL and 200 ng/mL, respectively. And the corresponding results of them are 11.571±0.003, 11.552±0.003 and 11.582±0.004, which are in good agreement with the value calculated by atomic absorption spectroscopy (AAS). The information obtained from this paper suggests that PCDFWM can be used to measure isotope ratios accurately in the samples with different concentrations under their suitable power conditions.

Optimization of GRIN lens Stokes polarimeter

Hui Ma, Jintao Chang, Honghui He, Chao He, Yong Wang, Nan Zeng, and Ran Liao

Doc ID: 237869 Received 10 Apr 2015; Accepted 20 Jul 2015; Posted 22 Jul 2015  View: PDF

Abstract: In a recent study we reported the gradient index (GRIN) lens Stokes polarimeter (GLP) [1]. With a simple architecture, this polarimeter can measure the state of polarization (SOP) in a single shot. In this article, we present further studies for improving the performance of the GLP. Detailed discussions are presented on the optimization process of the GLP based on different choices of data from the CCD images. It is pointed out that many optimization techniques, although developed for other types of Stokes polarimeters, can also be applied to the GLP because the GRIN lens can traverse all possible retardance and fast axis modulations.

Multi-region apodized photon sieve with enhanced efficiency and enlarged pinhole sizes

Tao Liu, Xin Zhang, Lingjie Wang, Yanxiong Wu, Jizhen Zhang, and Hemeng Qu

Doc ID: 240616 Received 08 May 2015; Accepted 20 Jul 2015; Posted 20 Jul 2015  View: PDF

Abstract: A novel multi-region structure apodized photon sieve is proposed. The number of regions, the apodization window values and pinhole sizes of each pinhole ring are all optimized to enhance the energy efficiency and enlarge the pinhole sizes. The design theory and principle are thoroughly discussed and proposed. Two numerically designed apodized photon sieves with the same diameter are given as examples. Comparisons have shown that the multi-region apodized photon sieve has a 25.5% higher energy efficiency and the minimum pinhole size is enlarged by 27.5%. Meanwhile, the two apodized photon sieves have the same form of normalized intensity distribution at the focal plane. This method could benefit the flexibility of design and fabricating the apodized photon sieve.

New hyperbola-parabola primary mirror in Cassgrain Optical antenna to improve transmission efficiency

yang huajun, Li Zhang, Lu Chen, Ping Jiang, Qian Mao, and Wei Caiyang

Doc ID: 242241 Received 02 Jun 2015; Accepted 20 Jul 2015; Posted 20 Jul 2015  View: PDF

Abstract: A novel optical model with a hyperbola-parabola primary mirror added in Cassegrain optical antenna, which can effectively improve the transmission efficiency, is firstly proposed in this paper. The optimum parameters of hyperbola-parabola primary mirror and secondary mirror for the optical antenna system have been designed and analyzed in detail. The parabola-hyperbola primary structure optical antenna is obtained to improve the transmission efficiency of 10.60% in theory and simulation efficiency changed 9.359%. For the different deflection angles to the receiving antenna with emit antenna, the coupling efficiency curve of the optical antenna has been obtained.

Dual-wavelength extinction method for fast sizing of metal nanosphere ensembles

Benfeng Bai, Xiaofei Xiao, and Ninghan Xu

Doc ID: 242326 Received 03 Jun 2015; Accepted 20 Jul 2015; Posted 20 Jul 2015  View: PDF

Abstract: We propose a simple dual-wavelength extinction (DWE) method to measure the average size of spherical metal nanoparticle (NP) ensembles. Unlike the spectroscopic methods that need to measure the full spectra of scattering and/or extinction to retrieve the NP size, the DWE method can estimate the NP size by measuring the light extinction at only two properly selected wavelengths and thus is useful for fast sizing of metal NP ensembles. The influences of both the NP shape deviation and ensemble dispersancy on the measurement accuracy are analyzed and discussed in detail. An empirical correction procedure is established to compensate these influences so as to further improve the accuracy. The feasibility and reliability of the DWE method are corroborated by experimentally measuring several typical gold spherical NP ensembles and comparing the results with those obtained by three other standard methods. The experimental results indicate satisfactory accuracy of the DWE method for measuring gold NPs from 30 nm to 100 nm by using two measurement wavelengths of 532 nm and 573 nm. The studies show that the DWE method is efficient, reliable, and easy to implement. It may find wide applications in the metrology of NPs.

Acousto-optic Q-switching laser performance of Yb:GdCa4O(BO3)3 crystal

Junhai Liu, Xiaowen Chen, Honghao Xu, Yunfeng Guo, Wenjuan Han, Haohai Yu, and Huaijin Zhang

Doc ID: 240726 Received 11 May 2015; Accepted 20 Jul 2015; Posted 21 Jul 2015  View: PDF

Abstract: We report on the active Q-switching laser performance of Yb:GdCa4O(BO3)3 crystal, demonstrated employing an acousto-optic Q-switch in a compact plano-concave resonator. Stable repetitively Q-switched operation is achieved with pulse repetition rates varying from 30 to 0.2 kHz, producing an average output power of 10.2 W at 1027.5 nm at 30 kHz of repetition rate, with an optical-to-optical efficiency of 30%. The maximum pulse energy generated at the lowest repetition rate of 0.2 kHz is 4.75 mJ, with a pulse width being 11 ns, giving rise to a peak power that amounts to 432 kW.

Transverse image translation using an optical freeform single lens

Jun Zhu, Xiaofei Wu, Tong Yang, and Guofan Jin

Doc ID: 240953 Received 13 May 2015; Accepted 20 Jul 2015; Posted 21 Jul 2015  View: PDF

Abstract: In this paper, we have proposed an approach utilizing freeform optical surfaces to the realization of a novel optical function called the transverse image translation, which acts as a basic geometrical transformation for images. Its purpose is to make the image of a given optical system move directionally with the designated distance by means of inserting and arranging some extra optical elements behind the given system. The structure of the given system, as well as its optical specifications, keeps unchanged when performing translation. As the translation is transverse, it is only allowed that the image moves transversely in the plane where the original image lies. A freeform single lens comprised of two different freeform surfaces is well-designed for the given system as the only translation element. The image of the given system is expected to be successfully translated transversely as designed when the freeform lens is properly inserted. The design method and process of freeform lens is presented briefly. A design example is introduced to demonstrate the feasibility of our proposed approach to the new-type transverse image translation.

Cell shape identification using digital holographic microscopy

Magnus Andersson, Johan Zakrisson, and Staffan Schedin

Doc ID: 241589 Received 25 May 2015; Accepted 20 Jul 2015; Posted 21 Jul 2015  View: PDF

Abstract: We present a cost-effective, simple and fast digital holographic microscopy method based upon Rayleigh-Sommerfeld back propagation for identification of the geometrical shape of a cell. The method was tested using synthetic hologram images generated by ray-tracing software and from experimental images of semi-transparent spherical beads and living red blood cells. Our results show that by only using the real part of the back-reconstructed amplitude the proposed method can provide information of the geometrical shape of the object and at the same time accurately determine the axial position of the object under study. The proposed method can be used in flow chamber assays for pathophysiological studies where fast morphological changes of cells are studied in high numbers and at different heights.

Characterization of Dual-Polarization LTE Radio over a Free-Space Optical Turbulence Channel

Jan Bohata, Stanislav Zvanovec, Zabih Ghassemlooy, Mojtaba Abadi, and Tomas Korinek

Doc ID: 242873 Received 12 Jun 2015; Accepted 20 Jul 2015; Posted 21 Jul 2015  View: PDF

Abstract: A dual polarization (DP) radio over a free-space optical (FSO) communication link using a long-term evolution (LTE) radio signal is proposed and analyzed under different turbulence channel conditions. Radio signal transmission over the DP FSO channel is experimentally verified via error vector magnitude statistics. Based on the results we show that transmitting of the LTE signal over the FSO channel is a potential solution for the last-mile access or backbone networks, when using multiple-input multiple-output based DP signals.

A reconfigurable optofluidic switch for generation of optical Pulse Width Modulation (PWM) based on tunable reflective interface

morteza mansuori, hamed hashemi, and gholam hossin zareei

Doc ID: 236960 Received 31 Mar 2015; Accepted 20 Jul 2015; Posted 21 Jul 2015  View: PDF

Abstract: We presented a novel method for generation of optical Pulse Width Modulation (PWM) based on tunable reflective interface by using microfluidic droplet. We have demonstrated a single layer, planar, optofluidic PWM switch that is driven by excited alternating microbubbles. The main parameters of generation of this PWM such as frequency and speed of switching can be controlled by the mass flow rates of input fluids, and the shape of plug or droplet. Advantages of this design are the reconfigurability in design andthe easy control of the switching parameters. The validation of the proposed design is carried out by employing the Finite Element Method" (FEM) for the mechanical simulation and the finite-difference time domain (FDTD) for the optical simulation.

Q-switched 1329 nm Nd:CNGG laser

Kun Xiao, Qiulin Zhang, Bin Lin, Dongxiang Zhang, Baohua Feng, Jingliang He, Huaijin Zhang, and jiyang wang

Doc ID: 239776 Received 27 Apr 2015; Accepted 20 Jul 2015; Posted 21 Jul 2015  View: PDF

Abstract: We demonstrate a laser diode pumped Q-switched 1329 nm neodymium-doped calcium-niobium-gallium-garnet (Nd:CNGG) laser using a V:YAG crystal as a saturable absorber. An average output power of 353 mW and a repetition rate of 13.43 kHz for Q-switched pulses were obtained. The pulse width was from 124 ns to 151.4 ns under different pump powers. Output power of 685 mW was obtained without the V:YAG crystal inserted.

760-fs diode-pumped mode-locked laser with Yb:LuAG crystal at 1032 nm

Xian-cui Su, Yiran Wang, Jingliang He, Ru-Wei Zhao, Peixiong Zhang, Yin Hang, Jia Hou, Baitao Zhang, and Zhao Shuang

Doc ID: 240035 Received 07 May 2015; Accepted 20 Jul 2015; Posted 21 Jul 2015  View: PDF

Abstract: In this study, we experimentally demonstrated the generation of 760-fs pulse duration from a diode-pumped Yb:LuAG mode-locked laser at 1032 nm. At the repetition rate of 58.6 MHz, the maximum average power of 1.07 W was obtained, corresponding to the peak power of 24 kW. To our knowledge, this results represent the shortest pulse duration and highest peak power ever obtained for a 1032 nm mode-locked laser with Yb:LuAG crystal.

(NRL) Irradiance correlations in retro-reflected beams

Rita Mahon, Mike Ferraro, Peter Goetz, Christopher Moore, James Murphy, and William Rabinovich

Doc ID: 240316 Received 06 May 2015; Accepted 20 Jul 2015; Posted 21 Jul 2015  View: PDF

Abstract: Communications links that utilize modulating retro-reflectors can make use of turbulence-induced fade information available at the remote data-signal terminal in order to optimize the data transfer rate. Experiments were conducted to measure the irradiance in both the direct and the retro-reflected beams, with both on-axis and off-axis components being recorded in order to further study the enhancement in scintillation index observed in the retro-reflected beam. Measurements were made over a 1.8km terrestrial range at AP Hill, VA. The degree of correlation of the received irradiance between the direct and double-passage beams is found to approach 90% onaxis and 70% outside of the Fresnel zone radius. The scintillation index in the retro-reflected beam is enhanced on-axis due to reciprocal optical paths. The measured scintillation indices, and the correlation of the retroreflected beam with the direct beam, are compared with a point source, point scatterer and point receiver model in the strong scintillation approximation.

Polarization-based balanced detection for spectral-domain optical coherence tomography

Taner Akkin and Adam Black

Doc ID: 241086 Received 18 May 2015; Accepted 20 Jul 2015; Posted 20 Jul 2015  View: PDF

Abstract: We present a new design for spectral-domain optical coherence tomography that allows balanced detection using a single camera. The design uses polarization optics to encode the light in reference and sample arms. Two parallel and highly aligned spectra, which carry out-of-phase interference signal and in-phase common noise and auto-interference terms, are focused on the camera that performs the digital balanced detection for each wavelength. The optical system is characterized and tested for tissue imaging. Results demonstrate consistent signal gains in depth and suppression of DC and sample auto-interference. The design can be amended further for polarization-sensitive imaging, and could provide a basis and demonstrate a market for manufacturing dual-line cameras with analog balanced detection capability.

Preparation of Fe-doped colloidal SiO2 abrasives and their chemical mechanical polishing behavior on sapphire substrates

hong Lei, zhanyong wang, qian Gu, and Ruling Chen

Doc ID: 240932 Received 14 May 2015; Accepted 20 Jul 2015; Posted 23 Jul 2015  View: PDF

Abstract: Abrasive is one of key influencing factors on the surface quality during the chemical mechanic polishing (CMP). Silica sol, as a kind of widely used abrasive in CMP slurries for sapphire substrates, often causes lower material removal rate (MRR). In order to improve MRR of sapphire substrates, Fe-doped colloidal SiO2 composite abrasives were prepared in the present paper. The CMP performances of Fe-doped colloidal SiO2 abrasives on sapphire substrate were investigated by using UNIPOL-1502 CMP equipment. Experimental results indicate that the Fe-doped colloidal SiO2 composite abrasives exhibit lower surface roughness and higher MRR than that of pure colloidal SiO2 abrasive under the same testing conditions. Furthermore, the acting mechanism of Fe-doped colloidal SiO2 composite abrasives in sapphire CMP was analyzed. X-ray photoelectron spectroscopy analysis shows that element Fe in the composite abrasives can react with sapphire substrates to form aluminum ferrite (AlFeO3) during CMP, which promotes the chemical effect in CMP and lead to the improvement of MRR.

Static spectropolarimeter concept adapted to space conditions and wide spectrum constraints

Martin Pertenais, Coralie Neiner, Pernelle Bernardi, Jean-Michel Reess, and Pascal Petit

Doc ID: 241806 Received 28 May 2015; Accepted 20 Jul 2015; Posted 23 Jul 2015  View: PDF

Abstract: The issues of moving elements in space and instruments working in always wider wavelength ranges lead to a need of robust polarimeters, efficient on a wide spectral domain and adapted to space conditions. As part of the UVMag consortium, created to develop spectropolarimetric UV facilities in space (such as the Arago mission proposed to ESA), we present an innovative concept of static spectropolarimetry. We studied a static and polychromatic method for spectropolarimetry. Instead of modulating the polarization information temporally, as usually done in spectropolarimeters, the modulation occurs in a spatial direction, orthogonal to the spectral one. Thanks to the proportionality between phase retardance imposed by a birefringent material and its thickness, birefringent wedges can be used to create this spatial modulation. The light is then spectrally cross-dispersed and a full-Stokes determination of the polarization over the whole spectrum can be obtained with a single-shot measurement. The use of Magnesium Fluoride wedges for example could lead to a compact, static polarimeter working at wavelengths from 0.115 μm up to 7 µm. We present the theory and simulations of this concept, as well as laboratory validation and practical application.

Exploring the physics of efficient optical trapping of nano-particles with ultrafast illumination

Arijit De, Debjit Roy, and Debabrata Goswami

Doc ID: 242653 Received 09 Jun 2015; Accepted 19 Jul 2015; Posted 20 Jul 2015  View: PDF

Abstract: Stable optical trapping of dielectric nano-particles with low power high repetition-rate ultrafast pulsed excitation has received considerable attention in recent times. However, the exact role of such excitation has so far been quite illusive since, for dielectric micron sized particles, the trapping efficiency turns out to be similar to that with continuous-wave excitation. In order to provide a coherent explanation of this apparently puzzling phenomenon, here we justify the superior role of high repetition-rate pulsed excitation in dielectric nano-particle trapping which is otherwise not possible with continuous-wave excitation at similar average power level. In addition, we show gradual trapping of individual quantum dots detected by stepwise rise in two-photon fluorescence signal from the trapped dots.

Microwave interrogated large core fused silica fiber Michelson interferometer for strain sensing

Liwei Hua, Yang Song, Jie Huang, Xinwei Lan, Yanjun Li, and Hai Xiao

Doc ID: 238398 Received 20 Apr 2015; Accepted 19 Jul 2015; Posted 20 Jul 2015  View: PDF

Abstract: A Michelson-type large core optical fiber sensor has been developed, which is designed based on the optical carrier based microwave interferometry (OCMI) technique, and fabricated by using two pieces of 200-µm diameter fused silica core fiber as two arms of the Michelson interferometer. The interference fringe pattern caused by the optical path difference of the two arms is interrogated in microwave domain, where the fringe visibility of 40 dB has easily been obtained. The strain sensing at both room temperature and high temperatures have been demonstrated by using such a sensor. Experimental results show that this sensor has a linear response to the applied strain, and also has minimized temperature-strain crosstalk. The dopant free quality of the fused silica fiber provides high possibility for the sensor to have promising strain sensing performance in high temperature environment.

Spectral attenuation and backscattering as indicators of average particle size

Wayne Slade and Emmanuel Boss

Doc ID: 239602 Received 23 Apr 2015; Accepted 19 Jul 2015; Posted 20 Jul 2015  View: PDF

Abstract: Measurements of the particulate beam attenuation at multiple wavelengths in the ocean typically exhibit a power law dependence on wavelength, and the slope of that power law has been related to the slope of the particle size distribution (PSD), assumed to be a power law function of particle size. Recently, spectral backscattering measurements have been made using sensors deployed at moored observatories, on autonomous underwater vehicles, and even retrieved from space-based measurements of remote sensing reflectance. It has been suggested that these backscattering measurements may also be used to obtain information about the shape of the PSD. In this work, we directly compared field-measured PSD with multi-spectral beam attenuation and backscattering in a coastal bottom boundary later. The results of this comparison demonstrated that (1) beam attenuation spectral slope correlates with average particle size as suggested by theory for idealized particles and PSD; and (2) measurements of spectral backscattering also contain information reflective of average particle size in spite of large deviations from a spectral power law shape.

Non-contact full-angle fluorescence molecular tomography system based on rotary mirrors

Daifa Wang, Jin He, Huiting Qiao, Ping Li, Yubo Fan, and Deyu Li

Doc ID: 240342 Received 05 May 2015; Accepted 19 Jul 2015; Posted 20 Jul 2015  View: PDF

Abstract: We propose a novel non-contact FMT system that achieves full-angle capacity with the use of a new rotary-mirror-based imaging head. In the imaging head, four plane mirrors are mounted on a rotating gantry to enable illumination and detection over 360°. In comparison with existing full-angle systems, our system does not require rotation of the specimen animal, the large and heavy light source with scanning head, or the camera with filters and lens. The system design and implementation are described in detail. Both physical phantom and in vivo experiments are performed to verify the performance of the proposed system.

Metallically coated dielectric rectangle resonator

Kai-Jun Che, Shuai Liu, Cheng-Xu Chu, Pan Zhang, Huiying XU, and Zhiping Cai

Doc ID: 240747 Received 27 May 2015; Accepted 19 Jul 2015; Posted 20 Jul 2015  View: PDF

Abstract: Double transfer matrix method (DTMM) is proposed for calculating the eigen values of the resonant mode of metallically coated dielectric rectangle resonator. Two dimensional electromagnetic analyses are performed to investigate the optical influences induced by planar structure parameters. The results show that there theoretically exists a highest Q factor resonance for both TE and TM modes at a certain length-width ratio with fixed resonant wavelength and resonator area. Due to the influences of surface plasma polaritons(SPP) trapped at the corners of the resonator which is not considered in DTMM, the TM mode resonances are deformed and deviate severely from that of analytical model. The geometric deformation on the resonator is introduced by replacing the four-right angles with circular boundaries, the SPP accompanied mode behaviors are corrected to the standing waves.

Manipulative attack using the phase retrieval algorithm for double random phase encoding

Tieyu Zhao, QIwen Ran, Lin Yuan, and Yingying Chi

Doc ID: 237973 Received 13 Apr 2015; Accepted 18 Jul 2015; Posted 20 Jul 2015  View: PDF

Abstract: A novel attack scheme is proposed based on phase retrieval algorithm. In the scheme, the attacker wiretaps channel and falsifies the ciphertext, which interferes with the users’ normal communication and quickly cracks system by gathering information. The difference between the attack scheme and the previous attack schemes is that it needs not establish certain assumptions, so this attack scheme has more practical application value and further significance of research. In this paper, we verify taking the double random phase encoding (DRPE) for example, and the results show that our proposed scheme is efficient and feasible.

Self-calibration and laser energy monitor validations for double-pulsed 2-μm CO₂IPDA lidar application

Tamer Refaat, Upendra Singh, Mulugeta Petros, Ruben Remus, and Jirong Yu

Doc ID: 246227 Received 01 Apr 2015; Accepted 18 Jul 2015; Posted 22 Jul 2015  View: PDF

Abstract: Double-pulsed 2-μm IPDA lidar is well suited for atmospheric CO₂remote sensing. IPDA lidar technique relies on wavelength differentiation between strong and weak absorbing features of the gas normalized to the transmitted energy. In double-pulse case, each shot of the transmitter produces two successive laser pulses separated by short interval. Calibration of the transmitted pulse energies is required for accurate CO₂ measurement. Design and calibration of a 2-μm double-pulse laser energy monitor is presented. The design is based on InGaAs pin quantum detector. A high-speed photo-electro-magnetic quantum detector was used for laser-pulse profile verification. Both quantum detectors were calibrated using a reference pyroelectric thermal detector. Calibration included comparing the three detection technologies in single-pulsed mode, then comparing the quantum detectors in double-pulsed mode. In addition, a self-calibration feature of the 2-μmIPDA lidar is presented. This feature allows monitoring the transmitted laser energy, through residual scattering, with a single detection channel. This reduces CO₂ measurement uncertainty. IPDA lidar ground validation for CO₂ measurement is presented for both calibrated energy monitor and self-calibration options. Calibrated energy monitor resulted in a lower CO₂ measurement bias while self-calibration resulted in a better CO₂ temporal profiling when compared to in-situ sensor.

(NRL) Imaging with multi-spectral mosaic-array cameras

Andrey Kanaev, Mary Kutteruf, Michael Yetzbacher, Michael DePrenger, and Kyle Novak

Doc ID: 241617 Received 26 May 2015; Accepted 17 Jul 2015; Posted 22 Jul 2015  View: PDF

Abstract: Emerging class of multi-spectral mosaic-array cameras combines opportunities of spectral data processing and full motion video color display. We explore capabilities of such sensors and propose novel demosaicking algorithm capable of enhancing resolution of equally-sampled multi-spectral mosaic imagery. We present experimental results of the proposed processing using the imagery acquired with 9-band SWIR mosaic-array camera.

Speckle suppressed phase-only holographic 3D display based on double constraint Gerchberg-Saxton algorithm

Jun Xia, Chenliang Chang, Lei Wei, Lei Yang, CM Yang, and Jianhong Chen

Doc ID: 240145 Received 05 May 2015; Accepted 17 Jul 2015; Posted 17 Jul 2015  View: PDF

Abstract: The Gerchberg-Saxton (GS) algorithm is widely used to calculate the phase-only computer-generated hologram (CGH) for holographic 3D display. However, the speckle noise is existed in the reconstruction of object due to the uncontrolled phase distribution in the image plane. In this paper, we proposed a method to suppress the speckle noise by simultaneously reconstructing the desired amplitude and phase distribution. The phase-only CGH is calculated by using a double constraint GS algorithm, in which both of the desired amplitude and phase information are constraint in the image plane in each iteration. The calculated phase-only CGH can reconstruct the 3D object on multiple planes with desired amplitude distribution and uniform phase distribution. So the speckle noise caused by the phase fluctuation between adjacent pixels is suppressed in this way. Both simulations and experiments are presented to demonstrate the validation of our algorithm and the reconstruction of the calculated phase-only CGH shows that the speckle noise can be effectively suppressed.

High data rate transient sensing using dielectric micro-resonator

Amir Ali, M. Otugen, and Tindaro Ioppolo

Doc ID: 240586 Received 13 May 2015; Accepted 17 Jul 2015; Posted 17 Jul 2015  View: PDF

Abstract: An approach to high-speed tracking of optical mode shifts of micro-resonators for wide-bandwidth sensing applications is presented. In the typical micro-resonator sensor, the whispering gallery optical modes (WGM) are excited by tangentially coupling tunable laser light into the resonator cavity, such as a microsphere. The light coupling is achieved by overlapping the evanescent field of the cavity with that of a prism or the tapered section of a single mode optical fiber. The transmission spectrum through the fiber is observed to detect WGM shifts as the laser is tuned across a narrow wavelength range. High data rate transient sensing applications require the tuning of the diode laser at high repetition rates and tracking of the WGM shifts. At high repetition rates the thermal inertia prevents appropriate tuning of the laser leading to smaller tuning ranges and waveform distortions. In the present, the laser is tuned using a harmonic (rather than ramp or triangular) waveform and its output is calibrated at various input frequencies and amplitudes using a Fabry-Perot interferometer to account for the tuning range variations. The WGM shifts are tracked by performing a modified cross-correlation method on the transmission spectra. Force sensor experiments were performed using both ramp and harmonic waveform tuning of the diode laser with rates up to 10 kHz. Results show that the harmonic tuning of the laser eliminates the high-speed transient thermal effects. The thermal model developed to predict the laser tuning agrees well the experiments.

Elliptic Cylindrical Silicon Nanowire Hybrid SPP Waveguide

Li Zhang, Qiulin Xiong, ma junxian, and Li Xiao peng

Doc ID: 240859 Received 25 May 2015; Accepted 17 Jul 2015; Posted 17 Jul 2015  View: PDF

Abstract: We proposed an elliptic cylindrical silicon nanowire hybrid SPP waveguide and evaluated its mode characteristics using a finite element method software COMSOL. The waveguide consists of three parts: an elliptic cylindrical silicon nanowire, a silver film layer and a silica covering layer between them. All of the components are surrounded by air. After optimizing the geometrical parameters of the waveguide, we can achieve the waveguide’s strong field confinement (ranging from λ^2⁄270 to λ^2⁄27) and long propagation distance (about 485 μm). In order to further understand the impact of the waveguide’s architecture on its performance, we also studied the cuboids hybrid waveguide. The results show that the cuboids waveguide has moderate local field confinement ranging from λ^2⁄190 to λ^2⁄20 and its maximum propagation distance is about 340 μm. We compared the proposed elliptic cylindrical and cuboids nanowire hybrid waveguides with the cylindrical hybrid waveguide we studied before. The elliptic cylindrical waveguide achieves a better trade-off between reasonable mode confinement and maximum propagation length in the three waveguides. The proposed hybrid surface plasmon waveguides are useful to construct devices such as directional coupler and may find potential applications in photonic integrated circuits or other novel SPP devices.

Evaluation of low-cadmium ZnCdSeS alloyed quantum dots for remote phosphor solid state lighting technology

Peter Siffalovic, Dominika Badanova, Andrej Vojtko, Matej Jergel, Martin Hodas, Marco Pelletta, Dusan Sabol, Marek Macha, and Eva Majková

Doc ID: 241359 Received 19 May 2015; Accepted 17 Jul 2015; Posted 17 Jul 2015  View: PDF

Abstract: We report on possibility to enhance the color rendering of commercially available remote phosphor light emitting diode modules by using low-cadmium content ZnCdSeS alloyed quantum dots. The employed numerical simulations showed that the color rendering index CRI of 90+ at the color correlated temperature of 3200 K can be achieved by application of a single layer of quantum dots onto neutral white remote phosphor substrate. The experimental results fully support the numerical calculations revealing the only limiting factor in achieving a higher photometric performance is the self-absorption effect in quantum dots. The presented low-cadmium content quantum dots allow price-effective upgrade of already existing remote phosphor solid state lighting technology towards a higher color rendering capability.

Investigation of remote-phosphor pcLEDs with improved scattered photon extraction structure

Shang-Ping Ying and An-Yung Shiu

Doc ID: 241118 Received 18 May 2015; Accepted 16 Jul 2015; Posted 16 Jul 2015  View: PDF

Abstract: In this study, an improved scattered photon extraction (SPE) package structure with a reflection plate over the remote phosphor layer is present. The important factors for the remote phosphor layer in the conventional and improved SPE package structures, including the phosphor layer thickness and phosphor concentration are also studied. The simulation results show that the yellow-blue ratio (YBR) of the conventional and improved SPE package structure increases with the phosphor concentration when the phosphor layer is thin and that the YBR is saturated when the layer is thick. The experimental results show that for both conventional and improved SPE package structure, the correlated color temperature (CCT) decreases as the phosphor concentration increases. However, the YBR of the improved SPE package structure is higher than that of the conventional SPE package structure for a given phosphor layer thickness and phosphor concentration. That is, in the conventional SPE package structure, it is necessary to increase the phosphor concentration and then increase the absorption of blue light to obtain more yellow light. Hence, for the improved SPE package structure, less phosphor is required in the phosphor layer for achieving the chosen CCT.

Optical design of an LED motorcycle headlamp with compound reflectors and a toric lens

Cheun-Lin Tien, Wen-Shing Sun, Wei-Chen Lo, and Pu-Yi Chu

Doc ID: 236954 Received 31 Mar 2015; Accepted 16 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: An optical design for a new white LED motorcycle headlamp is presented. The motorcycle headlamp designed in this study comprises a white LED module, an elliptical reflector, a parabolic reflector and a toric lens. The light emitted from the white LED module is located at the first focal point of the elliptical reflector and focuses on the second focal point. The second focal point of the elliptical reflector and the focal point of the parabolic reflector are confocal. We use non-sequential rays to improve the optical efficiency of the compound reflectors. The toric spherical lens allows the device to meet the Economic Commission of Europe, regulation No. 113 (ECE R113). Furthermore, a good uniformity is obtained by using aspherical surface optimization of the same toric lens. The reflectivity of the reflector is 95% and the transmittance of each lens surface is 98%. The average deviation of the high beam is 14.17% and the optical efficiency is 66.45%.

Study of the two-photon excitation of photoinitiator in various solvents, and the two-photon polymerization process

Khan Alam, Hidayat Khan, Bibi Safia Haq, Shahnaz Attaullah, Islam Zari, and Mian Mateenullah

Doc ID: 241593 Received 26 May 2015; Accepted 15 Jul 2015; Posted 16 Jul 2015  View: PDF

Abstract: In this study, the two photon absorption excited fluorescence of the photosensitizer 4, 4’-Bis (diethylamino) benzophenonin in different solvents is investigated by using mode-locked Ti: sapphire excitation having a wavelength of 800nm with pulse duration of 150 fs at the rate of 1 kHz. The fluorescence signals excited by wavelengths of 800 and 400 nm have been compared. Contribution of these cross section measurements for the two-photon polymerisation processes is also reported.

Efficient scheme for mid-infrared generation using simultaneous OPO and DFG processes in a double-pass pump configuration

om naraniya, M. shenoy, and Krishna Thyagarajan

Doc ID: 241690 Received 25 May 2015; Accepted 15 Jul 2015; Posted 16 Jul 2015  View: PDF

Abstract: We propose an efficient scheme for mid-infrared generation using simultaneous quasi phase matched OPO and DFG processes in a singly resonant cavity, with double-pass pump configuration. We present numerical results for the optimization of pump-to-idler conversion efficiency for the simultaneous OPO+DFG interaction in pulsed nanosecond operation. Considering an appropriately poled grating structure in MgO doped congruent Lithium Niobate (MgCLN), we have shown that it is possible to realize the double-pass pump singly-resonant (DPSR) cavity configuration for the simultaneous OPO+DFG process, unlike the cascaded interaction scheme, leading to efficient mid-IR generation. Our numerical results are in agreement with the recently reported experimental results. We also present optimum parameters for the DPSR cavity configuration that could provide maximum conversion efficiency.

(NRL) Spatially modulated laser pulses for printing electronics

Raymond Auyeung, Heungsoo Kim, Scott Mathews, and Alberto Pique

Doc ID: 242077 Received 01 Jun 2015; Accepted 15 Jul 2015; Posted 15 Jul 2015  View: PDF

Abstract: The use of a digital micromirror device (DMD) in laser-induced forward transfer (LIFT) is reviewed. Combining this technique with high viscosity donor ink (silver nanopaste) results in laser printed features that are highly congruent in shape and size to the incident laser beam spatial profile. The DMD empowers LIFT to become a highly parallel, rapidly reconfigurable direct-write technology. By adapting half-toning techniques to the DMD bitmap image, the laser transfer threshold fluence for 10 µm features can be reduced using an edge-enhanced beam profile. The integration of LIFT with this beam-shaping technique allows the printing of complex large-area patterns with a single laser pulse.

Measuring the contribution of atmospheric scatter to laser eye dazzle

Craig Williamson, John Rickman, David Freeman, Michael Manka, and Leon McLin

Doc ID: 237791 Received 09 Apr 2015; Accepted 15 Jul 2015; Posted 16 Jul 2015  View: PDF

Abstract: An experiment has been conducted to determine the contribution of atmospheric scatter to the severity of the dazzle experienced by a human under illumination from a visible laser. A 15 W 532 nm laser was propagated over a 380 m outdoor range in San Antonio, Texas, over nine data collection sessions spanning June and July 2014. A Narrow Acceptance Angle Detector (NAAD) was used to measure scattered laser radiation within the laser beam at different angles from its axis. Atmospheric conditions were logged via a local weather station, and air quality data were taken from a nearby Continuous Air Monitoring Station (CAMS). The measured laser irradiance data showed very little variation across the sessions and a single fitting equation was derived for the atmospheric scatter function. With very conservative estimates of the scatter from the human eye, atmospheric scatter was found to contribute no more than 5% to the overall veiling luminance across the scene for a human observer experiencing laser eye dazzle. It was concluded that atmospheric scatter does not make a significant contribution to laser eye dazzle for short-range laser engagements in atmospheres of good to moderate air quality, which account for 99.5% of conditions in San Antonio, Texas.

Analysis of Stationary Power/Amplitude Distributions for Multiple Channels of Sampled FBGs

Ya Xing, Xihua Zou, Wei Pan, Lianshan Yan, Bing Luo, and Liyang Shao

Doc ID: 238183 Received 15 Apr 2015; Accepted 15 Jul 2015; Posted 16 Jul 2015  View: PDF

Abstract: The stationary power/amplitude distributions for the multiple channels of the sampled fiber Bragg grating (SFBG) along the grating length are analyzed. Unlike a uniform FBG, the SFBG has multiple channels in reflection spectrum, not a single channel. Then, the stationary power/amplitude distributions for these multiple channels are analyzed by using two different theoretical models. In the first model, the SFBG is regarded as a set of grating sections and non-grating sections which are alternately stacked. A step-like distribution is obtained for the corresponding power/amplitude of each channel along the grating length. While in the second model, the SFBG is decomposed into multiple uniform “ghost” gratings, and a continuous distribution is obtained for each ghost grating (i.e., each channel). After a comparison, the distributions obtained in the two models are identical and the equivalence between the two models is demonstrated. In addition, the influences of the duty cycle on the power/amplitude distributions of multiple channels of SFBG are presented. © 2015 Optical Society of America

High laser efficiency and photostability of pyrromethene dyes mediated by non-polar solvent

ALOK RAY, Monika Gupta, Priyadarshani Kamble, Madhab Rath, and Debidas Naik

Doc ID: 240293 Received 05 May 2015; Accepted 15 Jul 2015; Posted 16 Jul 2015  View: PDF

Abstract: Many pyrromethene (PM) dyes have shown to outperform established rhodamine dyes in term of laser efficiency in green-yellow spectral region, but their rapid photochemical degradation in commonly used ethanol or methanol solvents continue to limit its use in high average power liquid dye lasers. A comparative study on narrow band laser efficiency and photostability of commercially available PM567 and PM597 dyes, using non-polar n-heptane and 1,4-dioxane and polar ethanol solvents, was carried out by a constructed pulsed dye laser, pumped by the second harmonic (532 nm) radiation of a Q-switched Nd:YAG laser. Interestingly, both the non-polar solvents showed a significantly higher laser photostability (~100 times) as well as peak efficiency (~5 %) of these PM dyes in comparison to ethanol. The different photostability of the PM dyes was rationalized by determining their triplet state spectra and capability of generating reactive singlet oxygen (1O2) by energy transfer to dissolved oxygen in these solvents using pulse radiolysis. Heptane is identified as a promising solvent for these PM dyes for use in high average power dye lasers, pumped by copper vapor lasers or diode pumped solid-state green lasers.

Extending generalized Kubelka-Munk to three dimensional radiative transfer

Arnold Kim and Christopher Sandoval

Doc ID: 240341 Received 05 May 2015; Accepted 15 Jul 2015; Posted 16 Jul 2015  View: PDF

Abstract: We extend the generalized Kubelka-Munk theory to study problems in three dimensional radiative transfer. We derive this extension by linear transforming the system of equations resulting from applying the double spherical harmonics method of order one to the radiative transfer equation. The result is an 8 x 8 system of partial differential equations, which we call the generalized Kubelka-Munk equations. We apply the generalized Kubelka-Munk equations to the problem of beam propagation and scattering in a plane-parallel slab composed of a uniform absorbing and scattering medium. We compare solutions of the generalized Kubelka-Munk equations with Monte Carlo simulations of the radiative transport equation. By doing so, we identify the range of validity for this approximation.

Precision distance measurement using two-photon absorption process in Si-APD with saw-tooth phase modulation

Yosuke Tanaka, Seiji Tominaka, and Takashi Kurokawa

Doc ID: 240608 Received 15 May 2015; Accepted 15 Jul 2015; Posted 15 Jul 2015  View: PDF

Abstract: We present a novel configuration of precision laser distance measurement based on two-photon absorption (TPA) photocurrent from a Si-APD. The proposed system uses saw-tooth phase modulation known as serrodyne modulation in order to shift the frequency of the reference light from that of the probe light. It suppresses the coherent interference noise between the probe and the reference. The serrodyne modulation also enables lock-in detection of TPA photocurrent. Furthermore, it contributes to reduction of the system components. Precision measurement is experimentally demonstrated by measuring a fiber length difference of 2.6-m with a standard deviation of 27 μm under constant temperature. The high-precision displacement measurement is also demonstrated by measuring temperature-induced change in optical path length difference of a fiber interferometer.

A new approach to analytically minimize the LCD Moiré by image-based particle swarm optimization

Yu-Lin Tsai and Chung-Hao Tien

Doc ID: 240767 Received 12 May 2015; Accepted 15 Jul 2015; Posted 15 Jul 2015  View: PDF

Abstract: In this paper, we proposed a methodology to optimize the parametric window of a LCD system, whose visual performance was deteriorated by the pixel moiré arising in between multiple periodic structures. Conventional analysis and minimization of moiré patterns are limited by few parameters. With proposed image-based particle swarm optimization (PSO), we enable a multi-variable optimization at the same time. A series of experiments was conducted to validate the methodology. Due to its versatility, the proposed technique will certainly have a promising impact on the fast optimization in LCD design with more complex configuration.

Effect of a wall pressure and shear stress on embedded cylindrical micro-lasers

Tindaro Ioppolo and Amir Hosein Zamanian

Doc ID: 240900 Received 13 May 2015; Accepted 15 Jul 2015; Posted 15 Jul 2015  View: PDF

Abstract: In this paper we carried out numerical experiments to study the effect of shear stress and pressure on the optical mode shift of two embedded cylindrical micro lasers. The optical cavities (laser) are encapsulated in a slab that is clamped at the bottom surface while the other sides of the slab are free stress boundaries. When a uniform shear stress and pressure is applied on the top surfaces of the slab, the morphology of the optical resonators are perturbed. This leads to a shift in the optical modes (commonly referred as whispering gallery mode WGM) of the resonators. The effect of the geometry (size and position of the optical cavities) and materials properties on the optical mode shift are studied. The results show a linear dependency of the WGM shift on the applied external pressure. Also the optical mode shift is slightly dependent on the geometry configurations and the material parameters. The effect of the shear stress on the WGM shift shows a quadratic dependency and this non-linearity is strongly dependent on the position of the resonators into the slab. The studies also show that this configuration could be used for simultaneous measurements of wall pressure and shear stress for fluid dynamics applications.

Interferometric nulling of four channels with integrated optics

Stefano Minardi, Ronny Errmann, Lucas Labadie, Balaji Muthusubramanian, Felix Dreisow, Stefan Nolte, and Thomas Pertsch

Doc ID: 241380 Received 21 May 2015; Accepted 14 Jul 2015; Posted 15 Jul 2015  View: PDF

Abstract: Nulling interferometry has been identified as a competitive technique for the detection of extrasolar planets. In its basic form, the technique consists in combining out-of-phase a single pair of telescopes to null effectively the light of a bright star an reveal the dim glow of the companion. However, in order to mitigate the effect of the stellar leaks through the interferometer, a broad angular central null is required. The hierarchical combination of several pairs of telescopes can accomplish this task. We have manufactured and tested with monochromatic light an integrated optics component which combines a linear array of 4 telescopes in the nulling mode envisaged by Angel&Wolf.[1] By simulating in the laboratory the the motion of a star in the sky, we could measure the expected angular transmission of the 4 telescope nuller. Moreover, the tests have demonstrated a broad nulling scaling as the fourth power of the baseline delay.

Modeling of surface topography in single point diamond turning machine

Rongguang Liang and Chih-Yu Huang

Doc ID: 240347 Received 05 May 2015; Accepted 14 Jul 2015; Posted 16 Jul 2015  View: PDF

Abstract: Surface roughness is an important factor in characterizing the performance of high precision optical surfaces. In this paper, we propose a model to estimate the surface roughness generated by single point diamond turning machine. In the model, we take into consideration the basic tool cutting parameters as well as the relative vibration between the tool and the workpiece in both infeed and feeding directions. Current models focus on the relative tool-workpiece vibration in the infeed direction. However, based on our experimental measurements, the contribution of relative tool-workpiece vibration in the feeding direction is significant and cannot be ignored in the model. The proposed model is able to describe the surface topography for flat surface as well as cylindrical surface of the workpiece. It has the potential to describe more complex spherical surfaces or freeform surfaces. Our experimental study with metal materials shows good correlation between the model and the diamond-turned surfaces.

Generalized Fibonacci photon sieves

Jie Ke and Junyong Zhang

Doc ID: 238012 Received 13 Apr 2015; Accepted 14 Jul 2015; Posted 15 Jul 2015  View: PDF

Abstract: We successfully extend the standard Fibonacci zone plates with two on-axis foci to the generalized Fibonacci photon sieves (GFiPS) with multiple on-axis foci, and propose the direct and inverse design methods based on the characteristic roots of the recursion relation of generalized Fibonacci sequence. By means of aperiodic switching sequence corresponding to the transparent and opaque zones generated by generalized Fibonacci sequence, we not only realize adjustable multi-focal distances, but also fulfill adjustable compression ratio of focal spots in different directions.

Active control of residual tool marks for freeform optics functionalization by novel biaxial-servo assisted fly-cutting

Suet To, Zhiwei Zhu, and Shaojian Zhang

Doc ID: 239821 Received 27 Apr 2015; Accepted 14 Jul 2015; Posted 15 Jul 2015  View: PDF

Abstract: The inherent residual tool marks (RTM) with particular pattern highly affects optical functions of the generated freeform optics in fast/ slow tool servo (FTS/STS) diamond turning. In the present study, a novel biaxial servo assisted fly cutting (BSFC) method is developed for flexible control of the RTM to be functional micro-/nanotexture in freeform optics generation, which are generally hard to achieve in FTS/STS diamond turning. In the BSFC system, biaxial servo motions along the z-axis and side-feeding directions are mainly adopted for primary surface generation and RTM control, respectively. Active control of the RTM from the two aspects, namely undesired effect elimination or effective functionalization, are experimentally demonstrated. A typical F-theta freeform surface with scattering homogenization and a micro-pyramid array with phase grating structure integrating both reflective and diffractive functions are experimentally fabricated. Some characteristic advantages of the BSFC system deriving from its unique cutting principle are critically identified, indicating that it is not only suitable for active control of the RTM, but also be more powerful for the generation of freeform optics with uniform surface quality and enhanced machining capacity.

Effective MTF Measurement Method for an Off-Axis Optical System

Yuan Hu, Dewen Cheng, Yongtian Wang, and Haichao Peng

Doc ID: 240021 Received 04 May 2015; Accepted 14 Jul 2015; Posted 15 Jul 2015  View: PDF

Abstract: The most common measurement equipment of modulation transfer function (MTF) operates along a coaxial testing light path, it can be used to test several fields along one radial direction and is suitable for an optical system with rotational symmetry. However, off-axis optical systems need multidimensional adjustment and complex mechanical structure to measure the MTF of fields. In this paper, we propose a MTF testing module to address this issue by adding a rotatable mirror to redirect the light. The testing module greatly simplifies MTF measurement of off-axis imaging systems in both the process and mechanism. The figure error of the rotatable mirror is analyzed to ensure the testing accuracy. An MTF testing of free-form surface prism using this novel method was successfully implemented and the results are presented. The method can be extended to the measurement of other parameters such as the effective focal length.

Time-series methods in analysis of the optical tweezers recordings

Jakub Slezak and Sławomir Drobczyński

Doc ID: 241238 Received 21 May 2015; Accepted 13 Jul 2015; Posted 13 Jul 2015  View: PDF

Abstract: In this paper we treat optical tweezers as discrete-time linear filters and analyse the recorded trajectories of the trapped beads using time-series methods. Using this techniques we obtain simple analytical formula for the aliased power spectrum density. Moreover, we separate influences of the noise and blur induced by the video camera from the physical content of the measurements, providing simple tools to detect and account for these distortions. Finally, checking how our tools work on the real data, we identify for what parameters of video camera calibration the blur is dominating and for what the additive noise is dominating. We also detect a range where these two distortions cancel each other, so that the data can be mistakenly classified as undisturbed.

Investigation on the Response of Fused Taper Couplers to Ultrasound Wave

Liu Yiying, Fengmei Li, Linjie Wang, and Zhenyu Zhao

Doc ID: 239889 Received 28 Apr 2015; Accepted 12 Jul 2015; Posted 13 Jul 2015  View: PDF

Abstract: The responses of fused taper couplers with different structure parameters to ultrasonic wave had been investigated theoretically and experimentally. A comprehensive analysis of the acousto-optic interaction was presented, taking into account both the elasto-optic effect and the geometric effect. It is found that direct deformation of the coupler induced by ultrasonic is the critical factor in the sensing mechanism and closely related to the sensor sensitivity. Moreover, the strain response of the coupler with different structure parameters was analyzed using a 3-D coupled acoustic-solid numerical model which was based on the developed mathematical model. According to the theoretical analysis, related experiments were carried out and experimental results show that sensor with longer stretching length has higher sensitivity and the sensitivity of the sensor takes a non-monotonic relation with aspect ratio, which are consistence with the theoretical analysis results. We argue that our work could provide a useful guide to design and optimize more sensitive ultrasonic sensor used in practical ultrasonic detection.

Fast Two-dimensional Fluorescence Correlation Spectroscopy Technique for Tea Quality Detection

Sailing He, Yongjiang Dong, Chunsheng Yan, yong zhengdong, and Hao Lu

Doc ID: 240105 Received 05 May 2015; Accepted 12 Jul 2015; Posted 13 Jul 2015  View: PDF

Abstract: A fast two-dimensional fluorescence correlation spectroscopy technique based on light emitting diodes is developed, which uses light intensity and excitation wavelength as quickly changeable and easily controllable external perturbations. A compact and automatic system is set up to detect the tea quality. A partial least square regression method is used to create predictive models for tea grades. Compared to the traditional fluorescence spectroscopy method, this convenient two-dimensional correlation spectroscopy technique is more accurate according to our experimental results and is promising for practical applications.

Sensitivity Analysis for Oblique Incidence Reflectometry Using Monte Carlo Simulations

Faisal Kamran and Peter Andersen

Doc ID: 237341 Received 01 Apr 2015; Accepted 12 Jul 2015; Posted 13 Jul 2015  View: PDF

Abstract: Oblique incidence reflectometry has developed into an effective, non-contact and non-invasive measurement technology for the quantification of both reduced scattering and absorption coefficients of a sample. The optical properties are deduced by only analyzing the shape of the reflectance profiles. This article presents the sensitivity analysis of the technique in the turbid media. Monte Carlo simulations are used to investigate the technique and its potential to distinguish the small changes between different levels of scattering. We present various regions of dynamic range of optical properties in which the system demands vary to be able to detect subtle changes in the structure of the medium, translated as measured optical properties. Effects of variation in anisotropy are discussed and results presented. Finally, experimental data of milk products with different fat content is considered as an example for comparison.

Registering functional defects into periodic holographic structures

Yuankun Lin, Jeff Lutkenhaus, David George, David Lowell, Bayaner Arigong, and Hualiang Zhang

Doc ID: 239829 Received 27 Apr 2015; Accepted 11 Jul 2015; Posted 13 Jul 2015  View: PDF

Abstract: In this paper, we presented two methods for registering desired defect lattices within background periodic lattices through spatial light modulator based holographic lithography. In one method, the diffraction efficiency from the engineered phase pattern was used to locally modify the fill fraction of polymerized materials in holographic structures, and at the same time, we achieved the lattice matching between modified and background regions. In the second method, we registered spatially variant lattices for 90 degree bend within the background periodic lattices through two steps of phase engineering of the laser beam

Wearable telescopic contact lens

Ashkan Arianpour, Glenn Schuster, Eric Tremblay, Igor Stamenov, Alex Groisman, Jerry Legerton, William Meyers, Goretty Alonso, and Joseph Ford

Doc ID: 235760 Received 27 Mar 2015; Accepted 11 Jul 2015; Posted 13 Jul 2015  View: PDF

Abstract: Abstract We describe the design, fabrication and test of a 1.6mm thick scleral contact lens providing both 1x and 2.8x magnified vision paths, intended for use as a switchable eye-borne telescope telescopic low vision aid. The F/9.7 telescopic vision path uses an 8.2 mm diameter annular entrance pupil and 4 internal reflections in a PMMA precision optic. This gas impermeable insert is contained inside a smooth outer casing of rigid gas permeable polymer, which also provides achromatic correction for refraction at the curved lens face. The unmagnified F/4.1 vision path is through the central aperture of the lens, with additional transmission between the annular telescope rings to enable peripheral vision. We discuss potential solutions for providing oxygenation for an extended wear version of the lens. The prototype lenses were characterized using a scale model human eye, and telescope functionality was confirmed in a small scale clinical (non-dispensed) demonstration.

(NRL) Combining Semiconductor Quantum Dots and Bioscaffolds into Nanoscale Energy Transfer Devices

Christopher Spillmann, Igor Medintz, Kimihiro Susumu, and Michael Stewart

Doc ID: 240149 Received 11 May 2015; Accepted 10 Jul 2015; Posted 13 Jul 2015  View: PDF

Abstract: Significant advances have been made in the development of nanoscale devices capable of exciton transport via Förster resonance energy transfer (FRET). Several requirements must be met for effective operation including a reliable energy harvesting source and highly organized, precision placement of energy relay elements. For the latter, biological scaffolds such as DNA provide a customizable, symmetric and stable structure that can be site-specifically modified with organic fluorophores. Here, advancements in nanoscale energy transfer devices incorporating semiconductor nanocrystals and bioscaffolds are reviewed with discussion of biofunctionalization, linker chemistries, design considerations, and concluding with applications in light harvesting, multiplexed biosensing, and optical logic.

(NRL) High Energy Krypton Fluoride Lasers for Inertial Fusion

Stephen Obenschain, Robert Lehmberg, David Kehne, Frank Hegeler, Matthew Wolford, John Sethian, James Weaver, and Max Karasik

Doc ID: 242526 Received 08 Jun 2015; Accepted 09 Jul 2015; Posted 14 Jul 2015  View: PDF

Abstract: Laser fusion researchers have realized since the 1970's that the deep ultra-violet light from excimer lasers would be an advantage as a driver for robust high-performance capsule implosions for inertial confinement fusion (ICF). Most of this research has centered on the krypton-fluoride (KrF) laser. In this article we review the advantages of the KrF laser for direct-drive ICF, the history of high energy KrF laser development, the present state of the art, and describe a development path to the performance needed for laser fusion and its energy application. We include descriptions of the architecture and performance of the multi-kilojoule Nike KrF laser-target facility and the 700 J Electra high repetition rate KrF laser that were developed at the U.S. Naval Research Laboratory. Nike and Electra are the most advanced KrF lasers for inertial fusion research and the energy application.

Direct measurements of temperature-dependent laser absorptivity of metal powders

Sheldon Wu, Alexander Rubenchik, Scott Mitchell, Ilya Golosker, Mary LeBlanc, and Noel Peterson

Doc ID: 238358 Received 20 Apr 2015; Accepted 09 Jul 2015; Posted 10 Jul 2015  View: PDF

Abstract: A compact system is developed to measure laser absorptivity for a variety of powder materials (metals, ceramics, etc.) with different powder size distributions and thicknesses. The measured results for several metal powders are presented. The results are consistent with those from ray tracing calculations.

High resolution fiber profilometer for hard-to-access areas

Xia Yu, Qijie Wang, Qize Zhong, Zhuang Liu, and Ying Zhang

Doc ID: 238060 Received 16 Apr 2015; Accepted 06 Jul 2015; Posted 07 Jul 2015  View: PDF

Abstract: A fiber-based profilometer is developed to measure hard-to-access areas with high resolutions. This system utilizes the low coherence light interferometry technique to detect internal surface profile of several samples. A differentiation method is employed to enhance the lateral and vertical resolutions of the measured imaging results. The probe structure is optimized for achieving a desired working distance and a small beam size. The performance of the profilometer system, especially its high resolution property, is demonstrated.

(NRL) Optimizing Average Power in Low Quantum Defect Lasers

Steven Bowman

Doc ID: 242059 Received 29 May 2015; Accepted 06 Jul 2015; Posted 15 Jul 2015  View: PDF

Abstract: Waste heat generation is a generic problem in high power solid-state laser systems. One way to reduce heat loading while improving efficiency is to reduce the laser’s quantum defect. This paper presents a simple analysis of low quantum defect laser materials. In these laser materials the effects of fluorescent cooling and weak loss processes should not be ignored. Simple expressions are developed for efficiency and heating in a steady-state purely radiative materials. These expressions are then extended to include weak losses and fluorescence reabsorption. Evaluation of these relations using ytterbium doped YAG is used to illustrate several optimization schemes and the impact of realistic losses.

Parametric Distortion Adaptive Neighborhood for Omnidirectional Camera

Yazhe Tang, You Fu Li, and Jun Luo

Doc ID: 243397 Received 18 Jun 2015; Accepted 03 Jul 2015; Posted 10 Jul 2015  View: PDF

Abstract: Catadioptric omnidirectional images exhibit serious nonlinear distortion due to the involved quadratic mirror. Conventional pinhole model based methods perform poorly when being directly applied to the deformed omnidirectional images. This study constructs a catadioptric geometry system to analyze the variation of neighborhood of an object in terms of the elevation and azimuth directions in a spherical coordinate system. To accurately represent the distorted visual information, a parametric neighborhood mapping model is proposed based on the catadioptric geometry. Unlike the conventional catadioptric models, the prior information of system is effectively integrated into the neighborhood formulation framework. Then, the distortion-adaptive neighborhood can be directly calculated based on its measurable image radial distance. This method can significantly improve the computational efficiency of algorithm since statistical neighborhood sampling is not used. On the basis of the proposed neighborhood model, a distortion-invariant Haar wavelet transform is presented to perform the robust human detection and tracking in catadioptric omnidirectional vision. The experiment results verify the effectiveness of the proposed neighborhood mapping model and prove that the distorted neighborhood in omnidirectional image follows nonlinear pattern.

Experiment evaluation of speckle suppression efficiency of 2D quasi-spiral M-sequence based DOE

Anatoliy Lapchuk, Genadzi Pashkevich, Victor Yurlov, Olexandr Prygun, Andriy Kryuchyn, Borodin Yuriy, Andriy Korchovyi, and Sergiy Shylo

Doc ID: 240683 Received 12 May 2015; Accepted 27 Jun 2015; Posted 22 Jul 2015  View: PDF

Abstract: The quasi –spiral 2D diffractive optical element (DOE) based ob M-sequence of length N = 15 is designed and manufactured. The speckle suppression efficiency by the DOE rotation is measured. The speckle suppression coefficient of 10.5, 6 and 4 are obtained for green, violet and red laser beams, respectively. It is found that the manufactured DOE structure has an error, that result in decrease of speckle suppression efficiency on more than 50%. The results of numerical simulation confirm that spiral DOE structure allows obtaining close to maximum possible speckle suppression efficiency for the DOE. The numerical simulation and experiment results show that the speckle suppression efficiency of the 2D DOE structure decreases approximately twice at the boundaries of visible range. It is shown that a replacement of this structure with the bilateral 1D DOE allows to obtain the maximum speckle suppression efficiency in the entire visible range of light

Plastic Identification Using Multi-Spectral Infrared Spectroscopy

Abraham Vázquez-Guardado, Debashis Chanda, Mason Money, and Nathaniel McKinney

Doc ID: 238391 Received 21 Apr 2015; Accepted 24 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: Identification and classification of plastics plays an important role in waste management and recycling process. Present electrical and optical sorting techniques lack required resolution for accurate identification in a high throughput manner for divers set of plastics commonly found in municipal waste. Multi-spectral infrared spectroscopic measurements are shown to uniquely identify all common as well as specialized plastics based on vibrational resonances. This simple optical technique in combination with a spectral signature library will enable high throughput and accurate detection of various plastics from recovered solid waste.

A broadband wavelength and angle resolved scattering characterization system for nanophotonics investigations

David Payne, Darren Bagnall, and Martin Charlton

Doc ID: 235956 Received 11 Mar 2015; Accepted 21 Jun 2015; Posted 22 Jun 2015  View: PDF

Abstract: The characterization of scattered light is complex and relatively non-standardized despite being of great importance to many optical technologies. Whilst total scatter can be efficiently measured using integrating sphere based techniques, a detailed determination of the full bidirectional scattering distribution function (BSDF) is far more challenging, often requiring complicated and expensive equipment as well as substantial measurement time. Due to this, many research groups rely on simpler, angle resolved scatter (ARS) measurements, yet these are typically carried out using a single wavelength source, therefore providing limited information. Here, we demonstrate a custom-built broadband angle resolved optical spectrometer (BAROS), which utilizes a supercontinuum white light laser source combined with a custom automated goniometer and a Si CCD array spectrometer in order to carry out broad spectral measurements of angle resolved scatter. The use of a collimated supercontinuum allows for small area measurements which are often crucial for investigation of nanophotonic samples created using expensive fabrication techniques. The system has been tested and calibrated, and accuracy and reproducibility has been verified by integrating wavelength and angle resolved scattering (WARS) data over the angular range and comparing to calibrated integrating sphere measurements.

Detection of toxic elements using Laser Induced Breakdown Spectroscopy in smoker and nonsmoker’s teeth and investigation of periodontal parameters

Mohammed Gondal, Abdul Majeed Alhashmi, Mohamed Nasr, Sami Shafik, and Yusuf Habibullah

Doc ID: 240702 Received 12 May 2015; Accepted 15 Jun 2015; Posted 07 Jul 2015  View: PDF

Abstract: Laser induced breakdown spectrometer (LIBS) was built and optimized to detect the level of toxic elements such as lead, cadmium and arsenic present in the roots of extracted teeth of smokers and nonsmokers. Sixty extracted teeth from patients having history of chronic periodontitis were divided into two groups of 30 teeth each for smoker and nonsmoker patients and a third group of 30 patients who didn't have history of chronic periodontitis as controls. The Pb, Cd and As concentrations in smokers were 34 - 55, 0.33 - 0.51 and 0.91- 1.5 ppm respectively, compared to the same elements concentration in non-smoker group, which was 23 - 29, 0.26 – 0. 31, 0.64 - 11 ppm range and 0.17- 0.31, 0.01- 0.05 and 0.05 - 0.09 ppm range for the control group. In order to test the validity of the results achieved using our LIBS system, a standard Inductively Coupled Plasma (ICP) technique was also applied for the analysis of same teeth samples and ICP results were found to be in an excellent agreement with our LIBS results. In addition to this, Gingival index (GI), plaque index (PI), clinical attachment loss (CAL) and probing pocket depth (PD) were also recorded. Our LIBS spectroscopic analysis showed high levels of lead, cadmium and arsenic concentration on root surfaces of teeth which may be due to clinical attachment loss (CAL).

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