Optimizing the precision of a multichannel three-polarizer spectroscopic ellipsometer

• Won Chegal, Jeong Pyo Lee, Hyun Mo Cho, Sang-Wook Han, and Yong Jai Cho
• received 03/04/2013; accepted 05/15/2013; posted 05/16/2013; Doc. ID 186396
• [full text: PDF (1467) KB)]
• Abstract: We developed a multichannel three-polarizer spectroscopic ellipsometer based on a novel data acquisition algorithm for achieving optimized precision. This algorithm measures unnormalized Fourier coefficients accurately and precisely. Offset angles for optical elements were obtained as wavelength-independent values using regression calibration. Derived subsets of data reduction functions were used to calculate sample parameters. Correlation coefficients of Fourier coefficients were used to calculate errors in the sample parameters. Mean standard deviations of the sample parameters for each data reduction method were compared to identify the best method. This approach could be used to identify suitable precision optimization methods for other rotating-element ellipsometers.

Keywords (OCIS):

• (120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
• (120.2130) Instrumentation, measurement, and metrology : Ellipsometry and polarimetry

Coherent backscattering enhancement in refracting media: diffusion approximation.

• Ya. Ilyushin
• received 02/22/2013; accepted 05/15/2013; posted 05/17/2013; Doc. ID 185797
• [full text: PDF (331) KB)]
• Abstract: Weak localization (coherent backscattering enhancement) phenomenon in media with graded refraction index is investigated within the diffusion approximation. The obtained analytic results are validated with numerical solution by finite-difference and Monte-Carlo calculations.

Keywords (OCIS):

• (030.5620) Coherence and statistical optics : Radiative transfer
• (290.1350) Scattering : Backscattering
• (010.5620) Atmospheric and oceanic optics : Radiative transfer

12345678910111213141516171819202122232425262728293031Study of Image Reconstruction for Terahertz Indirect Holography with Quasi-optics Receiver

• Xiang Gao, Chao Li, and Guangyou Fang
• received 02/04/2013; accepted 05/13/2013; posted 05/13/2013; Doc. ID 184849
• [full text: PDF (1185) KB)]
• Abstract: 12345678910111213141516171819202122232425262728293031In this paper, the indirect holographic image reconstruction algorithm was studied for terahertz imaging with quasi-optics receiver. Based on the combination of reciprocity principle and modified quasi-optics theory, analytical expressions of the received spatial power distribution and its spectrum are obtained for the interference of the object and reference wave. These results clearly give the quantitative relationship between the imaging quality and the parameters of the Gaussian beam, which provides a good criterion for the THz quasi-optics transceivers design in terahertz off-axis holographic imagers. To validate the effectiveness of the proposed analysis method, some imaging results with a 0.3THz prototype system are shown based on electromagnetic simulation.

Keywords (OCIS):

• (100.3010) Image processing : Image reconstruction techniques
• (090.1995) Holography : Digital holography
• (110.6795) Imaging systems : Terahertz imaging

12345678910111213141516171819202122232425262728293031Destructive impact of imperfect beam collimation in extraordinary optical transmission

• Aaron Jackson, Da Huang, Daniel Gauthier, and Stephanos Venakides
• received 01/29/2013; accepted 05/12/2013; posted 05/13/2013; Doc. ID 184327
• [full text: PDF (797) KB)]
• Abstract: 12345678910111213141516171819202122232425262728293031We investigate the difference between simulations and experiments measuring the transmission of energy through sub-wavelength, periodically arranged holes in a metal film. At normal incidence, simulations predict a sharp transmission minimum when the wavelength is equal to the periodicity, and sharp transmission maxima at one or more nearby wavelengths. In experiments, the sharpest maximum from the simulation is not observed at all, while the others appear less sharp. We make the model more accurate with the incorporation of new features to assess which one of them is responsible for the destruction of the sharp maximum. Incorporating imperfect conductivity and imperfect periodicity in our model leaves the sharp maximum intact. Imperfect collimation, on the other hand, incorporated into the model causes the destruction of the sharp maximum as happens in experiments. We provide analytic support through an asymptotic calculation for both the existence of the sharp maximum and for the destructive impact of imperfect collimation.

Keywords (OCIS):

• (050.1950) Diffraction and gratings : Diffraction gratings
• (310.2790) Thin films : Guided waves
• (050.6624) Diffraction and gratings : Subwavelength structures
• (310.6628) Thin films : Subwavelength structures, nanostructures

12345678910111213141516171819202122232425262728293031Insights into the dependent-scattering contributions to the extinction coefficient of highly scattering suspensions

• A. Garcia-Valenzuela, H. Contreras-Tello, J. A. Olivares, and F. Cuppo
• received 02/12/2013; accepted 05/11/2013; posted 05/13/2013; Doc. ID 185197
• [full text: PDF (779) KB)]
• Abstract: 12345678910111213141516171819202122232425262728293031We study theoretically the light extinction in random systems of highly scattering particles embedded in non-absorbing media. We aim to provide simple qualitative guidelines on the dependence of the light-extinction coefficient with the volume filling-fraction in the so-called dependent-scattering regime. We base our analysis on Keller’s second order perturbative approximation to the effective propagation constant. To gain some physical insight, we also analyze a simple model based on the physical notion that particles in a dense system scatter light in an effective medium to provide some physical insight.

Keywords (OCIS):

• (290.2200) Scattering : Extinction
• (290.4210) Scattering : Multiple scattering
• (290.7050) Scattering : Turbid media

12345678910111213141516171819202122232425262728293031Electromagnetic energy within single-resonance chiral metamaterial spheres

• Tiago Arruda, Felipe Pinheiro, and Alexandre Martinez
• received 03/04/2013; accepted 05/11/2013; posted 05/13/2013; Doc. ID 186359
• [full text: PDF (468) KB)]
• Abstract: 12345678910111213141516171819202122232425262728293031We derive an exact expression for the time-averaged electromagnetic energy inside a chiral dispersive sphere irradiated by a plane wave. The dispersion relations correspond to a chiral metamaterial consisting of uncoupled single-resonance helical resonators. Using a field decomposition scheme and a general expression for the electromagnetic energy density in bi-anisotropic media, we calculate the Lorenz-Mie solution for the internal fields in a medium that is simultaneously magnetic and chiral. We also obtain an explicit analytical relation between the internal electromagnetic field and the absorption cross-section. This result is applied to demonstrate that strong chirality leads to an off-resonance field enhancement within weakly absorbing spheres.

Keywords (OCIS):

• (290.4020) Scattering : Mie theory
• (160.1585) Materials : Chiral media
• (160.3918) Materials : Metamaterials
• (290.5825) Scattering : Scattering theory

12345678910111213141516171819202122232425262728293031Scattering by multiple parallel radially stratified infinite cylinders buried in a lossy half space

• Siu-Chun Lee
• received 03/21/2013; accepted 05/11/2013; posted 05/13/2013; Doc. ID 187521
• [full text: PDF (1033) KB)]
• Abstract: 12345678910111213141516171819202122232425262728293031The theoretical solution for scattering by an arbitrary configuration of closely spaced parallel infinite cylinders buried in a lossy half space is presented in this paper. Each cylinder is radially stratified with distinct complex refractive index and permeability. The incident radiation is an arbitrarily polarized plane wave propagating in the plane normal to the axes of the cylinders. Closed-form solutions are derived for the electric and magnetic fields and Poynting vector of radiation emerging from the half space. Numerical examples are presented to illustrate backscattering from a lossy half space containing multiple homogeneous and radially stratified cylinders at various depths for different angles of incidence of the source wave.

Keywords (OCIS):

• (290.0290) Scattering : Scattering
• (290.1350) Scattering : Backscattering
• (290.4210) Scattering : Multiple scattering
• (290.5850) Scattering : Scattering, particles
• (290.5825) Scattering : Scattering theory

12345678910111213141516171819202122232425262728293031Imaging Sparse Metallic Cylinders through a Local Shape Function Bayesian Compressive Sensing Approach

• Lorenzo Poli, Giacomo Oliveri, and Andrea Massa
• received 02/19/2013; accepted 05/05/2013; posted 05/09/2013; Doc. ID 185506
• [full text: PDF (361) KB)]
• Abstract: 12345678910111213141516171819202122232425262728293031An innovative method for the localization of multiple sparse metallic targets is proposed. Starting from the local-shape-function (LSF) formulation of the inverse scattering problem and exploiting the Multi-Task Bayesian Compressive Sensing (MT−BCS) paradigm, a two-step approach is described where, after a first estimation of the LSF scattering amplitudes, the reconstruction of the metallic objects is yielded through a thresholding and voting step. Selected numerical examples are presented to analyze the accuracy, the robustness, and the computational efficiency of the LSF−MT−BCS technique.

Keywords (OCIS):

• (100.3190) Image processing : Inverse problems
• (100.6950) Image processing : Tomographic image processing
• (280.0280) Remote sensing and sensors : Remote sensing and sensors
• (290.3200) Scattering : Inverse scattering
• (350.4010) Other areas of optics : Microwaves

Brightness perception of unrelated self-luminous colours

• Martijn Withouck, Kevin Smet, Wouter Ryckaert, Michael Pointer, Geert Deconinck, Jan Koenderink, and Peter Hanselaer
• received 12/19/2012; accepted 04/30/2013; posted 05/01/2013; Doc. ID 181968
• [full text: PDF (1095) KB)]
• Abstract: The perception of brightness of unrelated self-luminous coloured stimuli of the same luminance has been investigated. The Helmholtz-Kohlrausch effect, i.e. an increase in brightness perception due to an increase in saturation, is clearly observed. This brightness perception is compared with the calculated brightness according to six existing vision models, colour appearance models and models based on the concept of equivalent luminance. Although these models included the Helmholtz-Kohlrausch effect and half of them were developed to work with unrelated colours, none of the models seemed to be able to fully predict the perceived brightness. A tentative solution to increase the prediction accuracy of the colour appearance model CAM97u, developed by Hunt, is presented.

Keywords (OCIS):

• (330.1690) Vision, color, and visual optics : Color
• (330.5020) Vision, color, and visual optics : Perception psychology
• (330.5510) Vision, color, and visual optics : Psychophysics

12345678910111213141516171819202122232425262728293031Retinal mesopic adaptation model for brightness perception under transient glare

• Pablo Barrionuevo, Elisa Colombo, and Luis Issolio
• received 10/16/2012; accepted 04/26/2013; posted 05/06/2013; Doc. ID 178017
• [full text: PDF (1192) KB)]
• Abstract: 12345678910111213141516171819202122232425262728293031A glare source in the visual field modifies the brightness of a patch against a mesopic background. We have investigated the effect of two levels of transient glare on brightness perception for incremental stimuli with several combinations of both test (Lt) and background (Lb) mesopic luminances. With the lowest Lb, we obtained the highest brightness reduction, and, when Lb was increased, a growing trend was found. From the middle and through the high mesopic range, there was no major brightness reduction. The influence of Lt was insignificant. As Lb sets the adaptation, we hypothesized that retinal adaptation mechanisms would act when a transient glare source is present in the visual field. To explain our findings, a physiology-based model was developed; it adequately fits present and previous results.

Keywords (OCIS):

• (330.4060) Vision, color, and visual optics : Vision modeling
• (330.5380) Vision, color, and visual optics : Physiology
• (330.5510) Vision, color, and visual optics : Psychophysics
• (330.7320) Vision, color, and visual optics : Vision adaptation
• (290.2558) Scattering : Forward scattering

12345678910111213141516171819202122232425262728293031Optimization of Planar Self-Collimating Photonic Crystals

• Raymond Rumpf and Javier Pazos
• received 03/07/2013; accepted 04/25/2013; posted 05/07/2013; Doc. ID 186577
• [full text: PDF (5745) KB)]
• Abstract: 12345678910111213141516171819202122232425262728293031Self-collimation in photonic crystals has received a lot of attention in the literature, partly due to recent interest in silicon photonics, yet no performance metrics have been proposed. This paper proposes a figure of merit for self-collimation and outlines a methodical approach for calculating it. Performance metrics include bandwidth, angular acceptance, strength, and an overall figure of merit. Two key contributions of this work include the performance metrics and identifying that the optimum frequency for self-collimation is not at the inflection point. The figure of merit is used to optimize a planar photonic crystal composed of a square array of cylinders. Conclusions are drawn about how the refractive indices and fill fraction of the lattice impacts each of the performance metrics. The optimization is demonstrated by simulating two spatially variant self-collimating photonic crystals, where one has a high figure of merit and the other has a low figure of merit. This work gives optical designers tremendous insight in how to design and optimize robust self-collimating photonic crystals which promises many applications in silicon photonics and integrated optics.

Keywords (OCIS):

• (050.0050) Diffraction and gratings : Diffraction and gratings
• (130.0130) Integrated optics : Integrated optics
• (130.1750) Integrated optics : Components
• (130.2790) Integrated optics : Guided waves
• (130.5296) Integrated optics : Photonic crystal waveguides
• (050.5298) Diffraction and gratings : Photonic crystals

12345678910111213141516171819202122232425262728293031A Polarization Analyzer for all the States of Polarization of Light using a Structured Polarizer

• L. Kaiser, E. Frins, B. Hils, L. Beresnev, W. Dultz, and H. Schmitzer
• received 02/14/2013; accepted 04/24/2013; posted 05/02/2013; Doc. ID 185187
• [full text: PDF (697) KB)]
• Abstract: 12345678910111213141516171819202122232425262728293031Polarization analyzers are an essential measuring tool to improve the characteristics of optical components and optimize them with respect to a useful application in optical networks. We describe a new instrument of this kind which consists of two crossed birefringent wedges and acts as a continuous structured polarizer for all the states of polarization of light. We analyze this device theoretically using the Poincaré-sphere and the Jones-matrix method and verify our results in a number of experiments with quartz wedges and red filtered light. Different realizations of this instrument are discussed and an application as a beam splitter for all the states of polarization is proposed.

Keywords (OCIS):

• (120.5410) Instrumentation, measurement, and metrology : Polarimetry
• (260.1440) Physical optics : Birefringence

12345678910111213141516171819202122232425262728293031Multilevel fast multipole method based on a potential formulation for 3D electromagnetic scattering problems

• Mandiaye Fall, Salim Boutami, Alain Glière, Brian Stout, and Jerome Hazart
• received 01/24/2013; accepted 04/23/2013; posted 05/03/2013; Doc. ID 184084
• [full text: PDF (675) KB)]
• Abstract: 12345678910111213141516171819202122232425262728293031Combinations of Multilevel Fast Multipole Method (MLFMM) and Boundary Element Method (BEM) allow solving large-scale photonics problems with arbitrary geometry. A new MLFMM, based on a scalar and vector potentials formulation, instead of the conventional electric and magnetic currents formulation, is described. The method can deal with multiple lossy or lossless dielectric objects of arbitrary geometries, whether they are nested, in contact, or separated. It is demonstrated on several examples that the method is able to handle efficiently 3D photonic scatterers involving large numbers of unknowns. Firstly, absorption, scattering and extinction efficiencies of gold nanoparticle spheres, calculated by the MLFMM are compared with Mie's theory. Then, the bistatic Radar Cross Section (RCS) of a gold sphere near the plasmon resonance and of a silica coated gold sphere, obtained by the MLFMM, are compared with the predictions of Mie's theory. Finally, bistatic RCS of nanoparticle gold-silver heterodimer, calculated with MLFMM, are compared with BEM alone calculations.

Keywords (OCIS):

• (000.3860) General : Mathematical methods in physics
• (000.3870) General : Mathematics
• (000.4430) General : Numerical approximation and analysis
• (160.4670) Materials : Optical materials
• (190.5890) Nonlinear optics : Scattering, stimulated
• (260.1960) Physical optics : Diffraction theory

On the hydrodynamics of the turbulent Point-Spread Function

• Guy Potvin
• received 10/22/2012; accepted 04/23/2013; posted 04/24/2013; Doc. ID 178400
• [full text: PDF (1002) KB)]
• Abstract: We derive hydrodynamic equations for the Point-Spread Function (PSF) of an imaging system looking through atmospheric turbulence at an incoherent object. These are derived from the hydrodynamics of the index of refraction of the air. We use the path integral representation of the paraxial approximation for wave propagation through turbulence. We then study the case of a frozen turbulent refractive index field bieng advected past the imaging system with a constant wind and discuss the implications for optical flow estimation.We conclude by discussing possible directions for future work.

Keywords (OCIS):

• (000.3860) General : Mathematical methods in physics
• (010.1290) Atmospheric and oceanic optics : Atmospheric optics
• (010.1300) Atmospheric and oceanic optics : Atmospheric propagation
• (110.0115) Imaging systems : Imaging through turbulent media
• (110.4153) Imaging systems : Motion estimation and optical flow

Double Zernike expansion of the optical aberration function from its power series expansion

• Joseph J. Braat and Augustus Janssen
• received 04/16/2013; accepted 04/23/2013; posted 04/26/2013; Doc. ID 188903
• [full text: PDF (1230) KB)]
• Abstract: Various authors have presented the aberration function of an optical system as a power series expansion with respect to the ray coordinates in the exit pupil and the coordinates of the intersection point with the image field of the optical system. In practical applications, for reasons of efficiency and accuracy, an expansion with the aid of orthogonal polynomials is preferred for which, since the 1980's, orthogonal Zernike polynomials have become the reference. In the literature, some conversion schemes of power series coefficients to coefficients for the corresponding Zernike polynomial expansion have been given. In this paper we present an analytic solution for the conversion problem from a power series expansion in three or four dimensions to a double Zernike polynomial expansion. The solution pertains to a general optical system with four independent pupil and field coordinates and to a system with rotational symmetry in which case three independent coordinate combinations have to be considered. The conversion of the coefficients is analytically in closed form and the result is independent of a specific sampling scheme or sampling density as this is the case for the commonly used least squares fitting techniques. Computation schemes are given that allow the evaluation of coefficients of arbitrarily high order in pupil and field coordinates.

Keywords (OCIS):

• (080.0080) Geometric optics : Geometric optics
• (080.1010) Geometric optics : Aberrations (global)
• (110.0110) Imaging systems : Imaging systems
• (080.1005) Geometric optics : Aberration expansions

Ray-based diffraction calculations using stable aggregates of flexible elements

• Miguel Alonso
• received 04/05/2013; accepted 04/08/2013; posted 04/29/2013; Doc. ID 188370
• [full text: PDF (910) KB)]
• Abstract: Diffraction effects are incorporated into a ray-based method for wave propagation referred to as stable aggregates of flexible elements (SAFE). SAFE is based on the assignment of a Gaussian field contribution to each ray, where these contributions are not independent beam solutions of the wave equation. The effects of diffraction by planar opaque obstacles (within the Kirchhoff approximation) are accounted for by introducing rays emanating from the obstacle’s edges. The two leading asymptotic terms to the complex amplitudes for these contributions are derived. It is shown that this scheme leads to field estimates that remain valid and accurate at caustics and shadow boundaries, as illustrated by two examples, corresponding to a focused wave in free space and a field propagating in a layered inhomogeneous medium. For simplicity, two-dimensional propagation is considered.

Keywords (OCIS):

• (050.1220) Diffraction and gratings : Apertures
• (050.1940) Diffraction and gratings : Diffraction
• (050.1960) Diffraction and gratings : Diffraction theory
• (080.2710) Geometric optics : Inhomogeneous optical media
• (080.7343) Geometric optics : Wave dressing of rays

Design of an Image Restoration Algorithm for the TOMBO Imaging System

• Shachar Mendelowitz, Iftach Klapp, and David Mendlovic
• received 11/07/2012; accepted 04/07/2013; posted 04/22/2013; Doc. ID 178948
• [full text: PDF (9555) KB)]
• Abstract: The TOMBO system (Thin Observation Module in Bound Optics) is a multi channel sub imaging system over a single electronic imaging device. Each sub system provides a low resolution image from a unique lateral point of view. By estimating the images lateral position, a high resolution image is restored from the series of the LR images. The paper proposes a new multi-stage algorithm comprised of successive stages, improving difficulties in previous suggested schemes. First, the registration algorithm estimates the sub channel shift parameters and eliminates bias. Second, we introduce a new fast image fusion, overcoming visual blockiness artifacts which characterized previously suggested schemes. The algorithm fuses the set of sampled sub channel images into a single image, providing the reconstruction initial estimate. Third, an edge-sensitive quadratic upper bound term to the total variation regulator is suggested. The complete algorithm allows the reconstruction of a clean, high resolution image, in linear computation time, by the use of the linear conjugate gradients optimization. Finally, we present a simulated comparison between the proposed method to a previous suggested image restoration method. The results show that the proposed method yields a better reconstruction fidelity while eliminating spatial speckles artifacts associated with the previous suggested metho

Keywords (OCIS):

• (100.3190) Image processing : Inverse problems
• (100.6640) Image processing : Superresolution
• (110.1758) Imaging systems : Computational imaging
• (110.3010) Imaging systems : Image reconstruction techniques

First-order model of thermal lensing in a virtual eye: errata

• Rebecca Vincelette, Robert Thomas, Benjamin Rockwell, Clifton Clark, and Ashley Welch
• received ; accepted ; posted 03/25/2010; Doc. ID 125749
• [full text: PDF (456) KB)]

Keywords (OCIS):

• (120.6810) Instrumentation, measurement, and metrology : Thermal effects
• (170.1020) Medical optics and biotechnology : Ablation of tissue
• (170.3660) Medical optics and biotechnology : Light propagation in tissues
• (190.4710) Nonlinear optics : Optical nonlinearities in organic materials
• (330.3350) Vision, color, and visual optics : Vision - laser damage