Accepted papers to appear in an upcoming issue
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Deformation verification and surface improvement of active stressed lap for 4m-class primary mirror fabrication
- received 11/25/2014; accepted 02/20/2015; posted 02/23/2015; Doc. ID 228568
- [full text: PDF (2721) KB)]
- Abstract: The surface shape accuracy of active stressed lap impacts performance of grinding and polishing basically in the fabrication of large mirrors. We introduce a model of active stressed lap for the fabrication of 4m f/1.5 mirror based on Finite Element Analysis, and lap surface accuracy achieves RMS<1.8μm in FEA method. Using lap surface measurement system, experimental verification is put forward and RMS of measured lap surface is within 2μm in practice. A general improvement of lap surface accuracy by using Zernike polynomial is carried out. After compensating the calculation errors, lap surface accuracy is improved by 8%~23%, and achieves RMS<1.5μm finally, which is appropriate for practical grinding and polishing.
- (220.0220) Optical design and fabrication : Optical design and fabrication
- (220.4610) Optical design and fabrication : Optical fabrication
- (230.4040) Optical devices : Mirrors
A first approach to characterize tilts through multiples of pistons in the classical Ronchi test
- received 12/04/2014; accepted 02/20/2015; posted 02/23/2015; Doc. ID 228770
- [full text: PDF (940) KB)]
- Abstract: In this work, it is shown how a tilt can be introduced into a segmented surface through several piston terms, by using the classical Ronchi test. We have developed tilt error simulations by adding multiple constant terms in each point on the sagitta surface of a segment using ray tracing. So that a comparison between simulated Ronchigrams for piston and tilt has been realized for two adjacent segments of a segmented surface, thereby a clear difference in the shape of the piston and tilt patterns has been found. As a result we show the behavior of the central maximum of the fringes with the presence of tilt and/or piston. Additionally we present evidence of how to induce tilting without changing surface shape by adding multiple of pistons, and a description of how to characterize both piston and tilt using the Ronchi test is obtained.
- (120.5050) Instrumentation, measurement, and metrology : Phase measurement
- (220.1140) Optical design and fabrication : Alignment
Method of simultaneous measurement of two direction force and temperature using FBG sensor head
- received 12/18/2014; accepted 02/20/2015; posted 02/23/2015; Doc. ID 231080
- [full text: PDF (2452) KB)]
- Abstract: This paper presents a method for measuring two components of bending force and temperature using one sensor head. Indirect inference based on the spectra of two fiber Bragg gratings (FBGs) placed on a cantilever beam is used. The method was developed during work on the inverse problem of determining a non-uniform stress distribution based on FBG spectra. A gradient in the FBG stress profile results in a characteristic shape of its reflective spectrum. The simultaneous measurements of force and temperature were possible through the use of an appropriate layout of the sensor head. The spectral characteristics of the sensor's gratings do not retain full symmetry, which is due to the geometry of the sensor's head and the related difference in the distribution of the axial stress of the gratings. In the proposed approach, the change in width of the sum of the normalized transmission spectra was used to determine the value of the applied force. In the presented method, an increase in the sensitivity of this change to the force is obtained relative to the other known systems. A change in the spectral width was observed for an increase in bending forces from 0 to 150 N. The sensitivity coefficient of the spectral width to force, defined as the ratio of the change of the spectral half-width to the change in force was 2.6e-3 nm/N for the first grating and 1.2e-3 nm/N for the second grating. However, the sensitivity of the whole sensor system was 5.8e-3 nm/N, which is greater than the sum of the sensitivities of the individual gratings. For the purpose of this work, a station with a thermal chamber has been designed with a bracket on which fiber optic transducers have been mounted for use in further measurements. The sensor head in this experiment is considered to be a universal device with potential applications in other types of optical sensors, and it can be treated as a module for development through its multiplication on a single optical fiber.
- (060.2370) Fiber optics and optical communications : Fiber optics sensors
- (130.6010) Integrated optics : Sensors
- (060.3735) Fiber optics and optical communications : Fiber Bragg gratings
Photoemission performance of thin graded-structure AlGaN photocathode
- received 11/04/2014; accepted 02/20/2015; posted 02/20/2015; Doc. ID 226159
- [full text: PDF (360) KB)]
- Abstract: In order to research on the high-efficiency AlGaN photocathode, two AlGaN photocathodes with varied Al composition (0.68 and 0.4) and uniform Al composition (0.24) were grown. The photocathodes were activated by Cs adsorption, and got its quantum efficiency by the multi-information system. The result shown that the absorption rate of AlGaN photocathode with varied Al composition is half of AlGaN photocathode with uniform Al composition, but the quantum efficiency of the former is approximately about 29% higher than the latter. The built-in field at the emission layer of AlGaN photocathode with varied Al composition is much higher than the uniform Al composition AlGaN photocathode, which is the main factor that promotes the photoelectron movement toward photocathode surface and improves the photoemission performance of AlGaN photocathode.
- (230.5160) Optical devices : Photodetectors
- (300.6470) Spectroscopy : Spectroscopy, semiconductors
- (300.6540) Spectroscopy : Spectroscopy, ultraviolet
Estimation of excited state absorption and photo-bleaching in Fe2+ doped lithium sodium silicate glass under exposure to high power nanosecond laser pulses
- received 12/12/2014; accepted 02/19/2015; posted 02/20/2015; Doc. ID 230591
- [full text: PDF (1340) KB)]
- Abstract: Fe-doped lithium sodium silicate glasses co-doped with Sn and C to promote the Fe2+ redox state are investigated under simultaneous excitation at the first and third harmonics of a nanosecond Nd:YAG laser. The aim is to evaluate critical parameters associated with the potential use of this material as optical filter that transmits the third harmonic but blocks the fundamental frequency. Estimations of the excited state absorption coefficient and photobleaching (reduction of absorption at the fundamental) are provided. The results provide insight on the design and expected operational parameters of this type of Fe-doped materials.
- (160.2220) Materials : Defect-center materials
- (160.2750) Materials : Glass and other amorphous materials
- (160.4670) Materials : Optical materials
Dichroic Directional Excitation of Surface Plasmon Based on Integer-Programming Model
- received 01/06/2015; accepted 02/19/2015; posted 02/19/2015; Doc. ID 231982
- [full text: PDF (972) KB)]
- Abstract: A silver film, perforated with two subwavelength uniform slits, is proposed for dichroic directional excitation of surface plasmons polaritons (SPPs). Under the backside oblique illumination, the SPPs for two work wavelengths can propagate along the two opposite directions respectively or the same direction. Based on the SPPs interference, an Integer-Programming Model is established for dichroic directional excitation of SPPs. Branch and Bound Method is introduced to find the optimal solutions of Integer-Programming Model, and therefore the parameters of the structure and illumination angles can be obtained. The field distribution of the structure is investigated by using the Finite-difference time-domain method (FDTD) to verify our design. Our theoretical model can achieve dichroic directional excitation of SPPs, simultaneously
- (240.0240) Optics at surfaces : Optics at surfaces
- (240.6680) Optics at surfaces : Surface plasmons
Rigorous analysis of acoustic modes in low and high-index contrast silica fibers
- received 12/12/2014; accepted 02/19/2015; posted 02/19/2015; Doc. ID 229411
- [full text: PDF (884) KB)]
- Abstract: The vector acoustic modes in both well-established and emerging designs of optical waveguides have been studied through use of a computer code which has been developed based on the Finite Element Method (FEM). Dispersion curves and the displacement vectors for the transverse and longitudinal acoustic modes and the modal hybriness have been determined and these are shown for both low and high index contrast silica (SiO2) acoustic waveguides. Stimulated Brillouin Scattering (SBS) frequencies are also reported for the sub-wavelength size SiO2 optical waveguides.
- (000.4430) General : Numerical approximation and analysis
- (190.2640) Nonlinear optics : Stimulated scattering, modulation, etc.
- (190.5890) Nonlinear optics : Scattering, stimulated
- (290.5900) Scattering : Scattering, stimulated Brillouin
Optical distortions in end-pumped zigzag slab lasers
- received 01/05/2015; accepted 02/19/2015; posted 02/23/2015; Doc. ID 231483
- [full text: PDF (1059) KB)]
- Abstract: Ray tracing is performed to investigate the optical distortions in the end-pumped, zigzag slab. Optical path differences (OPDs) caused by temperature, slab deformation and stress birefringence are calculated under uniform pumping, the results show a steep edge in the width dimension and a thermal lens with an effective focal length as short as several meters in the thickness dimension. Dependence of depolarization on total internal reflection (TIR) phase retardance as well as the slab's cut angle is studied by the Jones matrix technique, results show that although at the pumping power of 10 kW, the mean depolarization of the 2.5×30×150.2 mm Nd:YAG slab is generally below 3%, it increases rapidly with pumping power. Besides, for the 0º or 60º cut slab, an optimal phase retardance range of 5º-13º exists, in which the depolarization loss can be lower than 0.5%. Finally, experiments on temperature and depolarization measurements verify the numerical results.
- (140.3480) Lasers and laser optics : Lasers, diode-pumped
- (140.3580) Lasers and laser optics : Lasers, solid-state
- (140.6810) Lasers and laser optics : Thermal effects
(ISSR2014) Real Time Automated Counterfeit Integrated Circuit Detection using X-ray Microscopy
- received 11/04/2014; accepted 02/18/2015; posted 02/19/2015; Doc. ID 226220
- [full text: PDF (860) KB)]
- Abstract: Determining the authenticity of integrated circuits is paramount in preventing counterfeit and malicious hardware from being used in critical military, healthcare, aerospace, consumer, and industry applications. Existing techniques to distinguish between authentic and counterfeit integrated circuits often includes destructive testing requiring subject matter experts. We present a non-destructive technique to detect counterfeit integrated circuits using X-ray microscopy and advanced imaging analysis with different pattern recognition approaches. Our proposed method is completely automated, and runs in real time. In our approach, images of an integrated circuit are obtained from an X-ray microscope. Local binary pattern features are then extracted from the X-ray image followed by dimensionality reduction through principal component analysis, and alternatively through a non-linear principal component methodology using a stacked autoencoder embedded in a deep neural network. From the reduced dimension features, we train two types of learning machines, a support vector machine with a non-linear kernel, and a deep neural network. We present experiments using authentic and counterfeit integrated circuits to demonstrate that the proposed approach achieves an accuracy of 100% in distinguishing between the counterfeit and authentic samples.
- (110.7440) Imaging systems : X-ray imaging
- (340.7440) X-ray optics : X-ray imaging
- (150.1135) Machine vision : Algorithms
- (100.4996) Image processing : Pattern recognition, neural networks
Non-unified integral imaging elemental image array generation method based on selective pixel sampling algorithm
- received 12/03/2014; accepted 02/17/2015; posted 02/19/2015; Doc. ID 228883
- [full text: PDF (3048) KB)]
- Abstract: We propose a method based on selective pixel sampling algorithm to generate non-unified integral imaging (II) elemental image array (EIA) with reduced moiré patterns at a low rendering cost and high three-dimensional (3D) resolution. In the proposed method, the redundant 3D information is captured for the non-unified pixel arrangement of elemental images and the moiré patterns are constrained by the constraint equations. The non-unified EIA’s corresponding information is mapped from the obtained 3D information based on selective pixel sampling algorithm. Appropriate experiments are carried out and the experimental results show that the proposed method can increase the 3D display quality of the reconstructed 3D images in the II display and reduce rendering cost markedly in the generation of ultra high-definition EIA.
- (110.0110) Imaging systems : Imaging systems
- (110.6880) Imaging systems : Three-dimensional image acquisition
- (230.0230) Optical devices : Optical devices
Single shot Z-effective dense plasmas diagnostic through simultaneous refraction and attenuation measurements with a Talbot-Lau X-ray Moiré Deflectometer
- received 12/09/2014; accepted 02/17/2015; posted 02/19/2015; Doc. ID 229251
- [full text: PDF (518) KB)]
- Abstract: The Talbot-Lau x-ray Moiré deflectometer is a powerful plasma diagnostic capable of delivering simultaneous refraction and attenuation information through the accurate detection of x-ray phase-shift and intensity. The diagnostic can provide the index of refraction n = 1 - δ + iβ of an object (dense plasma, for example) placed in the x-ray beam by independently measuring both δ and β, which are directly related to the electron density ne and the attenuation coefficient µ, respectively. Since δ and β depend on the effective atomic number Zeff, an elemental composition map can be obtained from the ratio between phase and absorption images acquired in a single shot. The Talbot-Lau X-ray Moiré deflectometer and its corresponding data acquisition and processing are briefly described to illustrate how the above is achieved; Zeff values of test objects within the 4-12 range were obtained experimentally through simultaneous refraction and attenuation measurements. We show that elemental mapping of objects does not require previous knowledge of sample length or shape. The determination of Zeff from refraction and attenuation measurements with Moiré deflectometry could be of high interest to various domains of HED research such as shocked materials and ICF experiments, as well as material science and NDT.
- (050.5080) Diffraction and gratings : Phase shift
- (110.7440) Imaging systems : X-ray imaging
- (120.4120) Instrumentation, measurement, and metrology : Moire' techniques
- (120.5050) Instrumentation, measurement, and metrology : Phase measurement
- (340.7440) X-ray optics : X-ray imaging
Polarizer based upon a plasmonic resonant thin layer on a squeezed photonic crystal fiber
- received 10/22/2014; accepted 02/17/2015; posted 02/19/2015; Doc. ID 225434
- [full text: PDF (827) KB)]
- Abstract: In this article, a polarizer based on surface plasmon resonance in a squeezed rectangular lattice is analyzed through a full-vector finite-element method (FEM) solver. The device allows one state of polarization (e.g. y-polarized mode) to propagate through the fiber while the other state (x-polarized mode) is heavily attenuated: the modal losses for the x- and y- polarized modes are 1221dB/cm and 1.6dB/cm, respectively, at the wavelength of 1310nm. Given the high differential attenuation between the two orthogonal polarization modes, the device could be used as a compact polarizer with potential applications in sensing, communications and other areas.
- (060.2400) Fiber optics and optical communications : Fiber properties
- (060.2420) Fiber optics and optical communications : Fibers, polarization-maintaining
- (230.3990) Optical devices : Micro-optical devices
- (230.5298) Optical devices : Photonic crystals
Spectro-temporal dynamics of Kerr combs with parametric seeding
- received 12/16/2014; accepted 02/17/2015; posted 02/17/2015; Doc. ID 230895
- [full text: PDF (577) KB)]
- Abstract: We report a joint theoretical and experimental investigation of the parametric seeding of a primary Kerr optical frequency comb. Electro-optic modulation sidebands matching multiple free-spectral ranges of an ultra-high Q mm-size magnesium fluoride disk-resonator are used as seed signals. These seed signals interact through four-wave mixing with the spectral components of a stable primary comb and give rise to complex spectro-temporal patterns. We show that the new frequency combs feature multi-scale frequency spacing, with major frequency gaps in the order of few hundred GHz, and minor frequency spacing in the order of few tens of GHz. The experimental results are in agreement with the numerical simulations using Lugiato-Lefever equation (LLE). We expect such versatile and coherent optical frequency combs to have potential applications in optical communications systems where frequency management assigns pre-defined spectral windows at the emitter stage.
- (140.4780) Lasers and laser optics : Optical resonators
- (190.3270) Nonlinear optics : Kerr effect
- (190.4380) Nonlinear optics : Nonlinear optics, four-wave mixing
- (230.5750) Optical devices : Resonators
Depth plane adaptive integral imaging using a varifocal liquid lens array
- received 08/27/2014; accepted 02/17/2015; posted 02/19/2015; Doc. ID 221755
- [full text: PDF (1111) KB)]
- Abstract: This paper proposes an enhanced integral imaging system with electrically controllable image plane to address the issue of limited depth problem in integral imaging. For implementation of the variable image plane, varifocal liquid lens array and driving device are adopted instead of an ordinary solid lens array. The position of the central depth plane is varied by adjusting focal length of the lens array. The proposed system enables matching between object position and depth plane electrically, and thus an object moving from 5.15 cm to 11.72 cm is clearly displayed with this method.
- (080.0080) Geometric optics : Geometric optics
- (100.6890) Image processing : Three-dimensional image processing
- (110.2990) Imaging systems : Image formation theory
Weak-Signal Iterative Holography
- received 10/07/2014; accepted 02/17/2015; posted 02/19/2015; Doc. ID 224422
- [full text: PDF (597) KB)]
- Abstract: An iterative holographic table-top experiment is presented, where a recorded hologram is used to re-illuminate the initial target. With this beam shaping setup, more light is directed to the target and the signal-to-noise is increased in the recorded hologram for each iteration until a convergence limit is met. We experimentally examine convergence properties of this iterative hologram reconstruction approach for weak object signals and compare with theory.
- (030.4280) Coherence and statistical optics : Noise in imaging systems
- (070.5040) Fourier optics and signal processing : Phase conjugation
- (090.0090) Holography : Holography
- (100.3010) Image processing : Image reconstruction techniques
- (110.1085) Imaging systems : Adaptive imaging
Beam shaping system based on prism array for improving the throughput of dispersive spectrometers
- received 12/09/2014; accepted 02/17/2015; posted 02/19/2015; Doc. ID 229475
- [full text: PDF (1109) KB)]
- Abstract: A beam shaping system (BSS) for improving the throughput of dispersive spectrometers is presented by employing two sets of single cylindrical lenses with short focal lengths and a prism array with advantages in the configuration and adjustment. The prism array configuration can achieve segmentation of the beam, and each subprism realizes the rotation of the subbeams around their direction of propagation. The BSS was designed based on the inverse method of beam shaping for laser diode (LD) bars and the means of optical slicer. In the preliminary experiment, a BSS was set up and by this BSS the incident light of a Neon lamp with circular spot from an input fiber was transformed into an elliptical spot coupled into the silt of spectrometers without the change of the divergence. Spectral measurement results demonstrated that the throughput of a dispersive spectrometer was doubled without the influence on the spectral resolution. The BSS has the characteristics of the miniaturization and modularization, and can be combined with the existing dispersive spectrometer to improve the luminous flux and the signal-to-noise ratios.
- (120.4820) Instrumentation, measurement, and metrology : Optical systems
- (120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
- (140.3300) Lasers and laser optics : Laser beam shaping
- (230.5480) Optical devices : Prisms
Nano-indentation of single-layer optical oxide thin films grown by electron-beam deposition
- received 12/22/2014; accepted 02/17/2015; posted 02/19/2015; Doc. ID 231162
- [full text: PDF (2580) KB)]
- Abstract: Mechanical characterization of optical oxide thin films is performed using nano-indentation, and the results are explained based on the deposition conditions used. These oxide films are generally deposited to have a porous microstructure that optimizes laser induced damage thresholds, but changes in deposition conditions lead to varying degrees of porosity, density, and possibly the microstructure of the thin film. This can directly explain the difference in the mechanical properties of the film studied here and those reported in literature.
- (310.1860) Thin films : Deposition and fabrication
- (310.3840) Thin films : Materials and process characterization
- (310.6870) Thin films : Thin films, other properties
Laser Beam Splitting by Polarization Encoding
- received 12/23/2014; accepted 02/17/2015; posted 02/19/2015; Doc. ID 231272
- [full text: PDF (674) KB)]
- Abstract: A scheme is proposed to design a polarization grating that splits an incident linearly polarized beam to an array of linearly polarized beams of identical intensity distribution and various polarization angles. The grating is equivalent to a combination of a space-variant rotator and a space-variant retarder. The linear polarization states of all split beams make the grating suitable for coherent beam combining architectures based on Dammann gratings.
- (050.1950) Diffraction and gratings : Diffraction gratings
- (140.3298) Lasers and laser optics : Laser beam combining
(CS2014) Compressive Sensing in the EO/IR
- received 11/04/2014; accepted 02/17/2015; posted 02/19/2015; Doc. ID 226157
- [full text: PDF (10840) KB)]
- Abstract: We investigate the utility of compressive sensing (CS) to electro-optic and infrared (EO/IR) applications. We introduce the field through a discussion of historical antecedents and the development of the modern CS framework. Basic economic arguments (in the broadest sense) are presented regarding the applicability of CS to the EO/IR and used to draw conclusions regarding application areas where CS would be most viable. A number of experimental success stories are presented to demonstrate the overall feasibility of the approaches and we conclude with a discussion of open challenges to practical adoption of CS methods.
- (110.1758) Imaging systems : Computational imaging
- (010.0280) Atmospheric and oceanic optics : Remote sensing and sensors
Extractive FTIR Spectroscopy with Cryogen-Free Low-Temperature Inert Preconcentration for Autonomous Measurements of Atmospheric Organics: 1: Instrument Development and Preliminary Performance
- received 01/26/2015; accepted 02/17/2015; posted 02/25/2015; Doc. ID 230496
- [full text: PDF (1882) KB)]
- Abstract: In collaboration with the Jefferson County Department of Health (JCDH) and the Environmental Protection Agency (EPA), the University of Alabama in Huntsville developed a novel sensor for detecting very low levels of volatile organic compounds (VOCs). This sensor uses a commercial FTIR spectrometer, a commercial long-path IR gas cell, a commercial acoustic Stirling cyrocooler, and a custom cryogen-free cryotrap to improve sensitivity in an autonomous system with on-board quality control and quality assurance. Laboratory and initial field results show this methodology is sensitive to and well-suited for a wide variety of VOC atmospheric research and monitoring applications, including EPA National Air Toxics Trends Stations and the National Core monitoring network.
- (010.1280) Atmospheric and oceanic optics : Atmospheric composition
- (070.4790) Fourier optics and signal processing : Spectrum analysis
- (120.4640) Instrumentation, measurement, and metrology : Optical instruments
- (280.1120) Remote sensing and sensors : Air pollution monitoring
- (300.6340) Spectroscopy : Spectroscopy, infrared