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Temperature dependence of Brewster's angle

Wei Guo

Doc ID: 301891 Received 07 Jul 2017; Accepted 21 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: In this work, a dielectric at a finite temperature is modeled as an ensemble of identical atoms movingrandomly around where they are trapped. Light reflection from the dielectric is then discussed in terms ofatomic radiation. Specific calculation demonstrates that because of the atoms’ thermal motion, Brewster’sangle is in principle temperature dependent, and the dependence is weak in the low-temperature limit.What is also found is that the Brewster’s angle is nothing but a result of destructive superposition ofelectromagnetic radiation from the atoms.

Incoherent component of light scattered bymonolayer of spherical particles. Analysis of angulardistribution and absorption of light

Natalia Loiko, Alexander Miskevich, and Valery Loiko

Doc ID: 304492 Received 10 Aug 2017; Accepted 20 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: We have derived analytical solution for incoherent component of light scattered by normally illuminatedmonolayer of homogeneous spherical particles. It is based on the quasicrystalline approximation (QCA) of thetheory of multiple scattering of waves as well as on the multipole expansion of electromagnetic fields and tensorGreen’s function in terms of vector spherical wave functions. We apply the solution to description of scattering andabsorption characteristics of partially ordered monolayer and monolayer with imperfect lattice. Impact of particlesize and type of particle spatial order on light absorption is studied. The comparison of calculated and availableexperimental data is made on the angular and spectral position of the first diffraction order peak for monolayerwith imperfect triangular lattice from SiO2 particles. The theoretical and experimental data are in close agreement.

Introduction to electromagnetic scattering

Fabrizio Frezza, fabio mangini, and Nicola Tedeschi

Doc ID: 296467 Received 23 May 2017; Accepted 20 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: In this paper, an introduction to the electromagnetic scattering is presented. We introduce the basic concepts needed to face a scattering problem, as the scattering, absorption, and extinction cross-sections. We define the vector harmonics and we present some of their properties. Finally, we face the two canonical problems of the scattering by an infinitely long circular cylinder, and by a sphere, showing as the introduction of the vector harmonics makes the imposition and solution of the boundary conditions particularly simple.

Precision of proportion estimation with binary compressed Raman spectrum

Philippe Réfrégier, Camille Scotté, Hilton de Aguiar, Herve Rigneault, and Frederic Galland

Doc ID: 302706 Received 21 Jul 2017; Accepted 19 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: The precision of proportion estimation with binary filtering of Raman spectrum mixture is analyzed when the number of binary filters is equal to the number of present species. It is shown that the Cramer-Rao bound provides a useful methodology to analyze the performance of such an approach and in particular when the binary filters are orthogonal. It is demonstrated that a simple linear mean square error estimation method is efficient (i.e. has a variance equal to the Cramer-Rao Bound). Evolutions of the Cramer-Rao bound are analyzed when the measuring times are optimized or when the considered proportion for binary filter synthesis are not optimized. Two strategies for the appropriate choice of this considered proportion are also analyzed for the binary filter synthesis.

Mode diversity of weakly modulated cavity antennas

Daniel Marks and David Smith

Doc ID: 300534 Received 22 Jun 2017; Accepted 18 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: The radiating mode of a cavity antenna at a particular frequency is fixed, however, by actively modulating the permittivity inside the cavity, the radiating mode may be changed. Using time-independent perturbation theory, we derive the modes of a cavity perturbed by a many modulating elements. It is found that with a sufficient number of modulators of sufficient strength, the number of unique fields radiated by the cavity may reach a limit determined by the number of unperturbed cavity modes. The number of addressable radiated fields increases exponentially with the number of modulators, however, perturbations involving the interaction of several modulators become progessively weaker. For antennas at millimeter and terahertz frequencies, such cavity antennas can realize a great diversity of radiation patterns using fewer active devices, better exploiting the diversity achieved by each added modulator.

Demonstration of single-shot digital holography using a Bayesian framework

Casey Pellizzari, Matthias Banet, Mark Spencer, and Charles Bouman

Doc ID: 306095 Received 11 Sep 2017; Accepted 17 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: In this letter, we present experimental results for image reconstruction, with isoplanatic-phase-error correction, from single-shot digital holography data. We demonstrate the utility of using a model-based iterative reconstruction (MBIR) algorithm to jointly compute the maximum a posteriori estimates of the phase errors and the real-valued object reflectance function. Specifically, we show that the MBIR algorithm is robust to noise and phase errors over a range of conditions.

Generation of vector Bessel beams with diffractive phase elements based on the Jacobi-Anger expansion

Gabriel Mellado-Villaseñor, Dilia Aguirre-Olivas, Ulises Ruiz, and Victor Arrizon

Doc ID: 306983 Received 12 Sep 2017; Accepted 14 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: We report the design and optimization of a diffractive phase element, whose phase modulation is derived from theJacobi-Anger relation, which allows the simultaneous generation of multiple scalar Bessel beams of differentinteger orders. In addition, by the appropriate treatment of a couple of such Bessel beams, we generate a vectorBessel beam of arbitrary order m. This beam is constructed by the collinear superposition of the scalar Besselbeam modes of orders m1 and m+1, with circular orthogonal polarizations. We demonstrate experimentally boththe simultaneous generation of the multiple scalar Bessel beams and the generation of vector Bessel beams oforders m=0 and m=1. These tasks are performed in an optical setup based on a pixelated liquid crystal spatial lightmodulator.

High-Q All-dielectric Thermal Emitters for Mid-InfraredGas-Sensing Applications

Muhammad Ali, Niall Tait, and Shulabh Gupta

Doc ID: 303959 Received 02 Aug 2017; Accepted 14 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: A simple all-dielectric thermal emitter unit cell for narrowband gas-sensing application, is proposed providinglarge Q-factors compared to its plasmonic counterpart. It consists of a high index dielectric basedelliptical puck on top of a back-reflector, providing narrowband thermal emission. Using full-wave simulations,it is demonstrated that the achievable Q-factors in this structure is orders of magnitude largerthan what have been shown for plasmonic cells, thanks to their low-loss electrical characteristics. Furthermore,the thermal emission properties can be engineered by manipulating the geometry of the unit cell,whereby it is shown that these unit cells can provide polarized thermal emission simultaneously in twoseparate frequency bands, with identical Q-factor characteristics, depending on its ellipticity parameter.

Iterative design of diffractive elements made of lossy materials

Antonie Verhoeven, Frank Wyrowski, and Jari Turunen

Doc ID: 304039 Received 02 Aug 2017; Accepted 13 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: Diffractive surface-relief elements made of lossy materials exhibit phase-dependent absorption, whichnot only reduces the efficiency but also distorts the signal if the surface-profile is realized on the basisof a phase-only design. We introduce an extension of the Iterative Fourier-Transform Algorithm, whichaccounts for such phase-dependent absorption, and present examples of its application to the design ofdiffractive beam splitters. The operator required for taking absorption into account is chosen to maximizethe efficiency of the found design.

Talbot carpet at the transverse plane produced in thediffraction of plane wave from amplitude radial gratings

Saifollah Rasouli, ALI MOHAMMAD KHAZAEI, and Davud Hebri

Doc ID: 304732 Received 15 Aug 2017; Accepted 13 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: We experimentally demonstrate and theoretically predict a new and unprecedented optical carpet thatincluded all the geometric shadow, and far-field and near-field diffraction patterns at the transverse planein the diffraction from a radial grating illuminated by a plane wave-front. The main feature of using radialgrating is the continuous change of spatial period along the radial direction. Therefore, the geometricshadow, and the near-field and far-field diffraction regimes are mixed at various propagation distancesand the traditional definitions for the different diffraction regimes would not apply here. We show thatfor a given propagation distance, at a certain radial distance the shadow regime changes to the near-fieldregime and at another certain radial distance the diffraction pattern changes from a near-field to a far-fieldcase.

Full characterization of the trajectories on the Poincaré sphere of polarization states of a beam passing through a rotating retarder

Karol Salazar-Ariza and Rafael Torres

Doc ID: 307082 Received 14 Sep 2017; Accepted 13 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: The emerging polarization states from a linearly polarized monochromatic light passing through a rotating retarder have been characterized as the intersection curve of a cylinder and the Poincaré sphere. But in the cases where the input polarization states are in general elliptical or circular, it produce trajectories which do not correspond to the intersection of a sphere with one cylinder. Hence, in this work we present a full characterization of the trajectories on the Poincaré sphere for monochromatic input beams with an arbitrary polarization state passing through a rotating retarder as the intersection curve of the Poincarésphere with a cone. Moreover, it is shown that these trajectories are characterized by their projection on the equator plane, having the form of Limaçon of Pascal (Pascal’s snails).

Determination of the optimum double-pass image through focus operators

Anibal de Paul Camacho, Roberto Sánchez, and Luis Issolio

Doc ID: 296117 Received 24 May 2017; Accepted 12 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: A set of autofocus operators (AFO) are assessed for their ability to determine the optimal double-pass image, as well as their potential to detect the focuses lines and the disc of least confusion in astigmatic eyes. Eight AFO and three optical quality parameters (OQP) often used to analyze double-pass aerial images were considered. To quantify the discriminative power of each AFO and OQP a maximum discrimination (MD) parameter was proposed. Double-pass images were obtained from an artificial eye with an induced astigmatism (Cylinder. -1 D, -0.75 D, 0.75 D, 1 D) and without astigmatism (Sphere. 0.1 D) and from 19 eyes of subjects with different refraction. The MD values for the autofocus operators Tenengrad variance and Gray level local variance were the highest for the artificial eye with and without astigmatism. In the case of astigmatic eyes the discrimination of the focuses lines with the autofocus operator Tenengrad variance was better than with OQP.

Built-up index methods and their applications for urban extraction from Sentinel 2A satellite data: discussion

Juan Valdiviezo-N, Alejandro Téllez-Quiñones, Adán Salazar-Garibay, and Alejandra López-Caloca

Doc ID: 301415 Received 03 Jul 2017; Accepted 12 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: Several built-up indices have been proposed in the literature in order to extract the urban sprawl from satellite data. Given their relative simplicity and easy implementation, such methods have been widely adopted for urban growth monitoring. Previous researches have shown that built-up indices are sensitive to different factors related to image resolution, seasonality, and study area location. Also, most of them confuse urban surfaces with bare soil and barren land covers. By gathering the existing built-up indices, the aim of this paper is to discuss some of their advantages, difficulties, and limitations. In order to illustrate our study, we provide some application examples using Sentinel 2A data.

Experimental comparison of single-pixel imaging algorithms

Liheng Bian, Jinli Suo, Qionghai Dai, and Feng Chen

Doc ID: 302829 Received 21 Jul 2017; Accepted 12 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: Single-pixel imaging (SPI) is a novel technique capturing 2D images using a photodiode, instead of conventional 2D array sensors. SPI owns high signal-to-noise ratio, wide spectrum range, and low cost. Various algorithms have been proposed for SPI reconstruction, including linear correlation methods that consider measurements as the correlations between scenes and modulation patterns, alternating projection methods treating measurements as zero-frequency coefficients of light fields in Fourier space, and compressive sensing based methods introducing priors of natural images. However, there is no comprehensive review discussing respective advantages, which is important for SPI's further applications and development. In this paper, we reviewed and compared these algorithms in a unified reconstruction framework. Besides, we proposed two other SPI algorithms including a conjugate gradient descent based method aiming to fit measurement formation, and a Poisson maximum likelihood based method utilizing photons' Poisson statistic. Experimental results on both simulated and real captured data validate the following conclusions: to obtain comparable reconstruction accuracy, the compressive sensing based total variation regularization method requires the least measurements and consumes the least running time for small-scale reconstruction; the conjugate gradient descent method and the alternating projection method run fastest in large-scale cases; the alternating projection method is the most robust to measurement noise. In a word, there are trade-offs between capture efficiency, computational complexity and noise robustness among different SPI reconstruction algorithms. We have released our source code for non-commercial use.

Matched and Wideband Flat Lens Antennasusing Symmetric Graded Dielectrics

Mohammad Khalaj AmirHosseini and mohammad Mahdi Taskhiri

Doc ID: 304294 Received 08 Aug 2017; Accepted 12 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: Matched and wideband flat lens antennas using atwo-dimensional symmetric graded dielectric (SGD) isconsidered. An explicit relation for refractive index of this type ofantenna is presented. This design relation is obtained in twosteps. First, the variation of refractive index in the radialdirection and then in the axial direction are determined.Additionally, reflector-lens antennas are introduced using twodimensional SGD. The validity of design methodology is verifiedby simulation.

Theoretical modelling and design of photonic structures in zeolite nanocomposites for gas sensing: part II - volume gratings

Dervil Cody and Izabela Naydenova

Doc ID: 305859 Received 01 Sep 2017; Accepted 12 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: The suitability of holographic structures fabricated in zeolite nanoparticle-polymer composite materials for gas sensing applications has been investigated. Theoretical modelling of the sensor response (i.e. change in hologram readout due to a change in refractive index modulation or thickness as a result of gas adsorption) of different sensor designs was carried out using Raman-Nath theory and Kogelnik’s Couple Wave Theory. The influence of a range of parameters on the sensitivity of holographically-recorded surface and volume photonic structures has been studied, namely hologram geometry, hologram thickness and spatial frequency, reconstruction wavelength, and zeolite nanoparticle refractive index. From this, the optimum fabrication conditions for both surface and volume holographic gas sensor designs have been identified. Here in part 2, results from modelling of the influence of design on the sensor response of holographically-recorded volume grating structures for gas sensing applications are reported.

Approximate Bayesian Computation Techniques for Optical Characterization of Nanoparticle Clusters

Ozan Ericok, Ali Cemgil, and Hakan Erturk

Doc ID: 295428 Received 08 May 2017; Accepted 10 Nov 2017; Posted 10 Nov 2017  View: PDF

Abstract: Characterization of nanoparticle aggregates from observed scattered light leads to a highly complex inverse problem. Even the forward model is so complex that it prohibits the use of classical likelihood based inference methods. In this study, we compare four so-called likelihood-free methods based on Approximate Bayesian Computation (ABC) that requires only numeric simulation of the forward model without the need of evaluating a likelihood. In particular, Rejection, Markov Chain Monte Carlo (MCMC), Population Monte Carlo (PMC) and Adaptive Population Monte Carlo (APMC) are compared in terms of accuracy. In the current model, we assume that the nanoparticle aggregates are mutually well separated and made up of particles of same size. Filippov’s particle-cluster algorithm is used to generate aggregates and discrete dipole approximation is used to estimate scattering behavior. It is found that APMC algorithm is superior to others in terms of time and acceptance rates although all algorithms produce similarposterior distributions. Using ABC techniques and utilizing unpolarized light experiments at 266 nm wavelength, characterization of soot aggregates is performed with less than 2 nm deviation in nanoparticle radius and 3-4 deviation in number of nanoparticles forming the monodisperse aggregates. Promising results are also observed for the polydisperse aggregate with log-normal particle size distribution.

The Validity of the Kirchhoff Approximation for the Scattering of Electromagnetic Waves from Dielectric, Doubly Periodic Surfaces

Mariano Franco, Matías Barber, Martín Maas, Oscar Bruno, Francisco Grings, and Esteban Calzetta

Doc ID: 306582 Received 08 Sep 2017; Accepted 06 Nov 2017; Posted 06 Nov 2017  View: PDF

Abstract: The accuracy of the Kirchhoff Approximation (KA) for rough-surface electromagnetic wave scattering is studied by comparison with accurate numerical solutions in the context of three-dimensional dielectric surfaces. The Kirchhoff tangent-plane approximation is examined without resorting to the principle of stationary phase. In particular, it is shown that this additional assumption leads to zero cross-polarized backscattered power, but not the tangent-plane approximation itself. Extensive numerical results in the case of a bisinusoidal surface are presented for a wide range of problem parameters: height-to-period, wavelength, incidence angles and dielectric constants. In particular, this paper shows that the range of validity inherent in KA includes surfaces whose curvature is not only much smaller, but also comparable to the incident wavelength, with errors smaller than 5% in total reflectivity; thus presenting a detailed and reliable source for the validity of KA in a three-dimensional fully polarimetric formulation.

Geometric optics of a refringent sphere illuminated by a point source: caustics, wavefronts and zero phase-fronts for every rainbow 'k' order

Paul Etienne Ouellette

Doc ID: 305673 Received 25 Aug 2017; Accepted 03 Nov 2017; Posted 06 Nov 2017  View: PDF

Abstract: This study relates to a refringent sphere illuminated by a point source placed at a distance h from its center; for h being infinite the light beam becomes parallel. A selection of variables, principally angular with the center of the sphere as common point, allows a global, straightforward and geometrically transparent way to the rays, caustics and wavefronts, internal as well as external, for every 'k' order, 'k' being the number of internal reflections. One obtains compact formulas for generating the rays and the wavefronts

Herpin effective media resonant underlayers andresonant overlayer designs for ultra high NAinterference lithography

Levi Bourke and Richard Blaikie

Doc ID: 296606 Received 23 May 2017; Accepted 01 Nov 2017; Posted 06 Nov 2017  View: PDF

Abstract: Dielectric waveguide resonant underlayers are employed in ultra high NA interference photolithography to effectively double the depth of field. Generally a single high refractive index waveguiding layer is employed.Here multilayer Herpin effective medium methods are explored to develop equivalent multilayer waveguiding layers. Herpin equivalent resonant underlayers are shown to be suitable replacements provided at least one layer within the Herpin trilayer supports propagating fields. Further to this a method of increasing the intensity incident upon the photoresist using resonant overlayers is also developed. This method is shown to greatly enhance the intensity within the photoresist making the use of thicker, safer,non-absorbing, low refractive index index matching liquids potentially suitable for large scale applications.

On the "unreasonable" effectiveness of Transport ofIntensity imaging and optical deconvolution

Timur Gureyev, Yakov Nesterets, Alexander Kozlov, David Paganin, and Harry Quiney

Doc ID: 304801 Received 15 Aug 2017; Accepted 01 Nov 2017; Posted 06 Nov 2017  View: PDF

Abstract: The effectiveness of reconstructive imaging using the Homogeneous Transport of Intensity equation may beregarded as “unreasonable”, because it has been shown to significantly increase signal-to-noise ratio whilepreserving spatial resolution, compared to equivalent conventional absorption-based imaging techniques at thesame photon fluence. We reconcile this surprising behavior by analyzing the propagation of noise in typical in-lineholography experiments. This analysis indicates that novel imaging techniques may be designed which producehigh signal-to-noise images at low radiation doses without sacrificing spatial resolution.

Polarization Properties of Ince-Gaussian Laser Beams

Surendra Singh, Sean Nomoto, Adam Goldstein, and Reeta Vyas

Doc ID: 309642 Received 24 Oct 2017; Accepted 27 Oct 2017; Posted 06 Nov 2017  View: PDF

Abstract: A consistent theoretical description of the polarization properties of Ince-Gauss (IG) laser beams is providedby constructing paraxial IG solutions to Maxwell equations. We confirm this description experimentallyby recording both the dominant and cross-polarization components. Moreover, by experimentallyconfirming the evolution of the dominant and cross-polarization components as functions of ellipticityparameters, our paper extends further support to a unified treatment of the three (Laguerre-Gauss,Hermite-Gauss, and Ince-Gauss) families of paraxial laser beams.

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