Accepted papers to appear in an upcoming issue
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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.
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 m1 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.
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).
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.
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.
Analytical and graphical ray tracing techniques based on a classical principle for photon refraction
Doc ID: 305130 Received 21 Aug 2017; Accepted 03 Nov 2017; Posted 06 Nov 2017 View: PDF
Abstract: In this work, a new classical principle that can explain the refraction of a single photon path at the boundary between two different media is proposed. This principle leads to the two well known laws of refraction and also to a simple linear form of Snell's law. This linear form not only played a vital role in simplifying the mathematics of analytical ray tracing but also led to a unified common form for the meridional ray tracing formulas. Also, it works as a basic rule for a new graphical ray tracing technique. In a previous work [H. A. Elagha, J. Opt. Soc. Am. A. 34, pp. 335- 343 (2017).], new exact ray tracing formulas were derived. All of these formulas are rewritten, in the current work, in terms of that linear form of Snell's law which revealed their common mathematical form. The meridional exact formula of a thick lens is generalized to include a whole system of spherical surfaces. From the latter, all the other exact ray tracing formulas can be easily derived. As an application, a single exact meridional formula for a ball lens and a formula for its longitudinal spherical aberration are derived. Also, we present a new ray tracing procedure for skew rays propagating through a system of spherical surfaces which can be centered, de-centered and/or tilted without the need to determine the point of incidence or the normal to the surface. Finally and also based on that linear form of Snell's law, a new graphical ray tracing technique that is simpler than the classical one is presented.
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
Reduced-basis boundary element method for fast electromagnetic field computation
Yating Shi, Xiuguo Chen, yinyin tan, Hao Jiang, and Shiyuan Liu
Doc ID: 296708 Received 25 May 2017; Accepted 02 Nov 2017; Posted 06 Nov 2017 View: PDF
Abstract: In this work, we combine conventional boundary element method (BEM) with the reduced-basis method (RBM)and propose a reduced-basis boundary element method (RB-BEM) to realize efficient modeling for parameterizedelectromagnetic scattering problems of dielectric scatterers. The RB-BEM allows splitting the modeling processinto a parameter-independent offline part and a parameter-dependent online part, and replacing the highdimensionaloriginal model obtained by conventional BEM with a low-dimensional reduced-basis model, toimprove computational efficiency of the online part. We also propose an improved greedy algorithm based onmulti-grid to improve the computational efficiency of the offline part. The numerical experiments indicate that theefficiency of the improved greedy algorithm is several times higher than that of the standard one, and the solvingefficiency of the reduced-basis model is several times to dozens of times higher than that of the original model witha prescribed approximation accuracy.
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.
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.
Effective spatial coherence of planar generalized sources propagating in the Fresnel model
Andre Beckus, alexandru tamasan, Aristide Dogariu, Ayman Abouraddy, and George Atia
Doc ID: 297626 Received 04 Jul 2017; Accepted 30 Oct 2017; Posted 30 Oct 2017 View: PDF
Abstract: Analytic expressions of the spatial coherence of partially coherent fields propagating in the Fresnel model in all but the simplest of scenarios are largely lacking and calculation of the Fresnel transform typically entails tedious numerical integration. Here, we provide a closed-form approximation formula for the case of a generalized source obtained by modulating a Gauss-Schell field distribution with a piecewise constant transmission function, which may be used to model the field's interaction with objects and apertures. The formula characterizes the coherence function in terms of the coherence of the Gauss-Schell field propagated in free space and a multiplicative term capturing the interaction with the transmission function. This approximation holds in the regime where the intensity width of the beam is much larger than the coherence width under mild assumptions on the modulating transmission function. The formula derived for generalized sources lays the foundation for the study of the inverse problem of scene reconstruction from coherence measurements.
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.
Improvement in Error Propagation in the Shack-Hartmann type Zonal Wavefront Sensors
BISWAJIT PATHAK and Bosanta Boruah
Doc ID: 306043 Received 31 Aug 2017; Accepted 26 Oct 2017; Posted 27 Oct 2017 View: PDF
Abstract: Estimation of the wavefront from measured slope values is an essential step in a Shack-Hartmann type wavefront sensor. Using an appropriate estimation algorithm, these measured slopes are converted into wavefront phase values. Hence, accuracy in wavefront estimation lies in proper interpretation of these measured slope values using the chosen estimation algorithm. There are two important sources of error associated with the wavefront estimation process, namely, the slope measurement error and the algorithm discretization error. The former type is due to the noise in the slope measurements or due to the detector centroiding error and the latter is a consequence of solving equations of a basic estimation algorithm adopted onto a discrete geometry. These errors deserve particular attention as they decide the preference of a specific estimation algorithm for wavefront estimation. In this paper, we investigate these two important sources of error associated with the wavefront estimation algorithms of Shack-Hartmann type wavefront sensors. We consider the widely used Southwell algorithm and the recently proposed Pathak-Boruah algorithm and perform a comparative study between the two. We find that the latter algorithm is inherently superior to the Southwell algorithm in terms of the error propagation performance. We also conduct experiments that further establishes the correctness of the comparative study between the said two estimation algorithms.
Application of Derivative Matrices of Skew Rays to Direct and Inverse Problems of Risley and Tilting- Orthogonal-Double-Prism
Psang Dain Lin and R. Barry Johnson
Doc ID: 301943 Received 11 Jul 2017; Accepted 23 Oct 2017; Posted 25 Oct 2017 View: PDF
Abstract: Risley systems and tilting-orthogonal-double-prism (TODP) systems are optical systems consisting of two prisms in series. The analysis of such systems typically involves both direct and inverse problems. Problems of the former type can be easily solved using raytracing equations. However, inverse problems are comparatively more difficult if the search direction is not properly given prior to iteration. In the present study, the two optical systems are modeled using the homogeneous coordinate notation. A method is then proposed for solving the direct and inverse problems of both optical systems using a raytracing approach and the first- and second-order derivative matrices of the skew rays. In addition, four optimization methods based on the two derivative matrices are proposed for determining the search direction in the inverse problem. Eight illustrative examples are given. It is shown that the proposed method can not only determine the scan patterns and sensitivity coefficients in the direct problem, but can also determine the search direction in the inverse problem.
A novel metrics for quantitative noise appraisal in holographic phase measurements
Silvio Montresor, Pascal Picart, and Mayssa KARRAY
Doc ID: 302770 Received 20 Jul 2017; Accepted 23 Oct 2017; Posted 25 Oct 2017 View: PDF
Abstract: This paper presents a reference-free metric for quantitative appraisal of de-noising algorithms for phase measurements in digital holography. In literature, quality metrics are not self-sufficient because they require a reference noise-free phase fringe pattern in order to be computed. In practical situations, no exact phase is available to evaluate the quality of processing. In order to bypass such a limitation, one needs a metrics directly capable of providing information on how efficient the filtering is, without any help of any reference measurement and by only considering the measured available phase data. This paper presents a novel reference-free metric, called estimated phase error for quantitative appraisal of de-noising algorithms for noisy phase data processing. This metrics is based on the computation of an estimator of the standard deviation of the phase error between data processed with an outstanding algorithm and that from the evaluated algorithm. A benchmark, including 37 different de-noising algorithms, demonstrates that the proposed metrics is capable of producing the same rankings as those obtained with a classical metrics requiring a reference phase. Application to phase data from mechanical testing leads to demonstration that ranking obtained from experimental phase data is similar than that obtained during the benchmark with simulated data.