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Accepted papers to appear in an upcoming issue

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Tighter focus for ultrashort pulse vector light beams:change of the relative contribution of different fieldcomponents to the focal spot upon pulse shortening

Svetlana Khonina and Ilya Golub

Doc ID: 319809 Received 15 Jan 2018; Accepted 18 Apr 2018; Posted 19 Apr 2018  View: PDF

Abstract: We investigate focusing of Poisson-spectrum few cycle pulsed light beams for linear, circular, azimuthal andradial input polarizations with and without a 1st order vortex. It is shown that for all the considered cases thefocal spot is tighter when compared to long pulses due to the increased blue frequencies content in theultrashort pulses spectrum. More significantly, we show, for the first time, to the best of our knowledge, thatupon pulse shortening, different focused beam vector components associated with different Bessel functionsJ0 or J1 undergo a change in the relative weight of their respective contribution to the focal spot size. Thiseffect is caused by different spectral dependencies of J0 and J1 near the focus. The revealed property ofbroadband ultrashort pulses has to be taken into account/may be used to an advantage in light-matterinteractions.

Two-photon speckle illumination for super-resolutionmicroscopy

awoke negash, simon labouesse, Patrick Chaumet, Kamal Belkebir, Hugues Giovannini, Marc Allain, Jerôme Idier, and Anne Sentenac

Doc ID: 320626 Received 25 Jan 2018; Accepted 18 Apr 2018; Posted 19 Apr 2018  View: PDF

Abstract: We provide a numerical study of a microscopy set-up in which the sample is illuminated with uncontrolledspeckle patterns and the Two-Photon Excitation fluorescence is collected on a camera. We showthat, using a simple deconvolution algorithm for processing the speckle low-resolution images, this widefieldimaging technique exhibits a resolution significantly better than that of Two-Photon Excitation scanningmicroscopy or One-Photon Excitation brightfield microscopy.

Focus shaping and optical manipulation using highlyfocused second-order full Poincaré beam

Yuxiong Xue, Yusong Wang, Sichao zhou, Hongwei Chen, Guanghao Rui, Gu Bing, and Qiwen Zhan

Doc ID: 322682 Received 08 Feb 2018; Accepted 18 Apr 2018; Posted 19 Apr 2018  View: PDF

Abstract: Generation of vectorial optical fields with arbitrary polarization distribution is of great interest in plenty ofapplications. In this work, we propose and experimentally demonstrate the generation of second-order fullPoincaré (FP) beam and its application in two-dimensional (2D) flattop beam shaping with spatially variantpolarization under high numerical aperture focusing condition. Besides, the force mechanism of the focal field with2D flattop beam profile is numerically studied, demonstrating the feasibility to trap dielectric Rayleigh particle inthree-dimensional space. The results show that the additional degree of freedom provided by the FP beam allowsone to control the spatial structure of polarization, to engineer the focusing field, and to tailor the optical forceexerted on a dielectric Rayleigh particle. The findings reported in the work may find useful applications in lasermicromachining, optical trapping, and optical assembly.

Experimental demonstration of ray-rotation sheets

Johannes Courtial, Nong Chen, Sean Ogilvie, Blair Kirkpatrick, Alasdair Hamilton, Graham Gibson, Tomas Tyc, Eric Logean, and Toralf Scharf

Doc ID: 325977 Received 13 Mar 2018; Accepted 18 Apr 2018; Posted 19 Apr 2018  View: PDF

Abstract: We have built micro-structured sheets that rotate, on transmission, the direction of light rays by an arbitrary, but fixed, angle around the sheet normal. These ray-rotation (RR) sheets comprise two pairs of confocal lenticular arrays. In addition to rotate the direction of transmitted light rays, our sheets also offset ray position, but only on the scale of the scale of the diameter of the lenticules. If this ray offset is sufficiently small so that it cannot be resolved, our RR sheets appear to perform generalised refraction.

Computational simulation of Haidinger’s Brushes

Gary Misson, Shelby Temple, and Stephen Anderson

Doc ID: 321336 Received 05 Feb 2018; Accepted 17 Apr 2018; Posted 18 Apr 2018  View: PDF

Abstract: Haidinger’s Brushes (HB) are entoptic phenomena resulting from differential absorption of linear polarized light by the human macula. Computational models have assisted in understanding the behavior of these subjective phenomena, but have been limited in their application. This study presents a revised computational model that incorporates known determinants of the form and behavior of HB. The model generates both static and animated simulations of HB that can be quantified by their density, contrast and radial/circumferential extent. Measured physiological parameters are used to demonstrate the dependency of HB on macular pigment (MP) density, MP distribution and ocular retardation. Physiological variations in these parameters explain the reported variations in the perception of HP.

Nonclassical correlations of photonic qubits carryingorbital angular momentum through non-Kolmogorovatmospheric turbulence

Mei-Song Wei, Jicheng Wang, YiXin Zhang, and Zhengda Hu

Doc ID: 318282 Received 08 Feb 2018; Accepted 17 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: We consider the non-horizontal distributions of orbitalangular momentum biphotons through free space atmosphericchannels, in which case the non-Kolmogorovturbulent effects shall be considered. By consideringthe case of initial non-perfect resource, i.e., the orbitalangular momentum biphotons are initially prepared inan extended Werner-like state, we investigate the non-Kolmogorov effects on the propagations of nonclassicalcorrelations, including quantum entanglement andquantum discord. It is found that universal decaylaws of entanglement and discord also exist for non-Kolmogorov turbulence but with their decay curves differentfrom that of entanglement for Kolmogorov turbulencereported by [Leonhard et al., Phys. Rev. A91, 01 45 (2015)]. We show that the universal decaylaws are dependent on the power-law exponent of non-Kolmogorov spectrum and compare the differences ofdecay properties between entanglement and discordcaused by non-Kolmogorov turbulence.

Trapping two types of particles by using a tightly focused radially polarized power-exponent-phase vortex beam

Chengjin Fan, Yongxin Liu, Xiaoyan Wang, Ziyang Chen, and Jixiong Pu

Doc ID: 322777 Received 14 Feb 2018; Accepted 16 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: We investigate the intensity of a radially polarized power-exponent-phasevortex (PEPV) beam focused by a high numerical aperture objective. A bright focalspot and a focal annulus with a dark core can be generated by changing the phase ofthe PEPV beam. The possibility of trapping a gold particle with the bright focal spotand trapping an air bubble with the focal annulus is discussed, and the force andtrapping stability are calculated. It is shown that a tightly focused radially polarizedPEPV beam is applicable to trapping two types of particles.

Abruptly autofocusing property of circular Airy vortex beams with different initial launch angles

Yunfeng Jiang, Shuofeng Zhao, Wenlei Yu, and Xiuwei Zhu

Doc ID: 324503 Received 19 Feb 2018; Accepted 16 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: Controlling the trajectory of circular Airy beam (CAB) by negative launch angles would greatly reduce its abruptly autofocusing property. By numerically simulating the propagation of circular Airy vortex beam with different initial launch angles, we demonstrate in this paper that a larger topological charge of optical vortex (OV) is quite helpful to enhance the abruptly autofocusing property under different launch angles (especially for negative launch angles), without affecting the focal position and trajectory. Two opposite OVs would attract each other and partially overlap in the focal plane of CAB under different launch angles, causing even stronger autofocusing. As the distance between two OVs increases, the focal intensity contrast would decrease, especially for the beam with positive launch angles, whose autofocusing property decreases much more quickly with the distance.

Generalized time independent correlation transportequation with static background: influence ofanomalous transport on the field autocorrelationfunction

Tiziano Binzoni, Fabrizio Martelli, and Tomasz Kozubowski

Doc ID: 324579 Received 20 Feb 2018; Accepted 16 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: A generalized time independent correlation transport equation (GCTE) for the field autocorrelation functionis proposed. The GCTE generalizes various models for anomalous transport of the photons and takesinto account possible presence of static background. In a tutorial example, the GCTE is solved for a homogeneoussemi-infinite medium in reflectance configuration through Monte Carlo simulations. The chosenanomalous photon transport model also includes the classic and the “generalized” Lambert-Beer’s law(depending on parameters’ choice). A numerical algorithm allowing to generate the related anomalousrandom photon steps is also given. The clear influence of anomalous transport on the field autocorrelationfunction is shown and discussed, for the proposed specific examples, by comparing the general resultswith the classical case (Lambert-Beer’s law).

Semi-analytical model for the electromagneticenhancement by a rectangular nano-wire opticalantenna on metallic substrate

Jianing Wan, Junda Zhu, Ying Zhong, and Haitao Liu

Doc ID: 318757 Received 29 Dec 2017; Accepted 13 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: The electromagnetic enhancement by a metallic nano-wire optical antenna on metallic substrate is investigatedtheoretically. By considering the excitation and multiple scattering of surface plasmon polaritons (SPPs) in thenano-gap between the antenna and the substrate, we build up an intuitive and comprehensive model that providessemi-analytical expressions for the electromagnetic field in the nano-gap to achieve an understanding of themechanism of electromagnetic enhancement. Our results show that antennas with short lengths that support thelowest order of resonance can achieve a high electric-field enhancement factor over a large range of incidenceangles. Two phase-matching conditions are derived from the model for predicting the antenna lengths atresonance. Excitation of symmetric or anti-symmetric localized surface plasmon resonance (LSPR) is furtherexplained with the model. The model also shows superior computational efficiency compared to full-wavenumerical method when scanning the antenna length, the incidence angle or the wavelength.

An approach for sequential image interpretation usinga priori binary perceptual topological and photometricknowledge and k-means based segmentation.

Jean-Baptiste Fasquel and nicolas delanoue

Doc ID: 321377 Received 02 Feb 2018; Accepted 13 Apr 2018; Posted 16 Apr 2018  View: PDF

Abstract: The proposed approach exploits a priori known qualitative inclusion and photometric relationships betweenimage regions, represented by oriented graphs. Our work assumes a sequential image segmentationprocedure where regions are progressively segmented and recognized by associating them with correspondingnodes in graphs related to the prior knowledge. The main contribution concerns the parameterizationof the k-means clustering algorithm, to be used during the segmentation procedure, and thegraph-matching-based identification of resulting clusters, corresponding to regions declared in graphs.The parameterization of k-means is based on known relationships as well as on regions which have beensegmented and recognized at previous steps. Parameters are the region of interest within which k-meansclustering is constrained, the number of clusters and seeding constraints. Photometric relationships builtfrom resulting clusters are matched with a priori known relationships to identify each cluster, this beingformulated as an exact graph matching problem. The potential of this approach is studied on four usecases involving real grayscale and color images with dedicated sequential analysis procedures. Processingresults are compared with those obtained without the proposed parameterization of k-means, as wellas with some other clustering approaches. Results show the relevance of our approach, in particular interms of segmentation accuracy, computation time and seeding reliability.

Analysis of the Yule-Nielsen effect with themultiple-path point spread function in a frequencymodulated halftone

Geoffrey Rogers

Doc ID: 314742 Received 04 Dec 2017; Accepted 11 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: The Yule-Nielsen effect is an influence on halftone color caused by the diffusion of light within the paperupon which the halftone ink is printed. The diffusion can be characterized by a point spread function. Inthis article a point spread function for paper is derived using the multiple-path model of reflection. Thismodel treats the interaction of light with turbid media as a random walk. Using the multiple-path pointspread function a general expression is derived for the average reflectance of light from an FM halftone,in which dot size is constant and the number of dots is varied, with the arrangement of dots random.It is also shown that the line spread function derived from the multiple-path model has the form of aLorentzian function.

Lens magnification affects the estimates of refractiveerror obtained using eccentric infrared photorefraction

Shrikant Bharadwaj, Praveen Bandela, and Vinay Nilagiri

Doc ID: 318770 Received 29 Dec 2017; Accepted 10 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: Positive and negative powered ophthalmic lenses are used in eccentric infrared photorefraction to calibrate the device,correct the subject’s baseline refractive error before an experimental manipulation or stimulate blur-drivenaccommodation. Through theoretical modeling of luminance gradients formed across the pupil and empiricalmeasurements of the eye’s refractive error using a commercial photorefractor, this study shows that imagemagnification by positive lenses and image minification by negative lenses under- and overestimates the refractiveerror, respectively, all independent of image defocus. The impact of image magnification/minification therefore appearsnon-trivial in experimental paradigms involving ophthalmic lenses to manipulate the eye’s optics duringphotorefraction.

Estimation of Camera Spectral Sensitivity FunctionUsing a Neural Learning and Architecture

sedigheh chaji, Alireza Pourreza, hamidreza Pourreza, and Modjtaba Rouhani

Doc ID: 321339 Received 05 Feb 2018; Accepted 09 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: In this paper, we propose a robust method to estimate the camera spectral sensitivity function using a neuralnetwork based model and a custom learning algorithm. A new and specially designed architecture for training ourneural network model is presented to estimate the spectral sensitivity as a function of wavelength. The sensitivityfunction is modeled as the sum of few Gaussian functions and a radial basis function (RBF) neural network istrained to approximate this function over the visual wavelengths. No constraints are imposed on the illuminationdistribution and spectral sensitivity as similar methods usually do. Experimental results show that proposedmethod produces superior results with much lower Root Mean Square Error (RMSE) compared to the methodsusing basis functions or constraint optimization approaches. Study of the reproduced colors also verifies theaccuracy of our method.

Predictive dynamic digital holography and imagesharpening

Sennan Sulaiman, Steve Gibson, and Mark Spencer

Doc ID: 317916 Received 18 Dec 2017; Accepted 09 Apr 2018; Posted 10 Apr 2018  View: PDF

Abstract: Digital holography is often combined with image sharpening for wavefront estimation and correction,and this combination has received recent attention for many imaging and sensing applications. A significantobstacle for digital holography and image sharpening in high-speed real-time applications is thefact that the process is computationally intensive, requiring iterative virtual wavefront propagation andhill-climbing algorithms to optimize sharpness criteria. This paper introduces a method for acceleratingdynamic digital holography and image sharpening by wavefront prediction. The approach here integratesoptimal state-space prediction filters with digital holography and image sharpening to short circuit thecomputationally intensive process of virtual wavefront propagation and sharpness optimization.

Orthonormal vector general polynomials derived fromthe Cartesian gradient of the orthonormal Zernikebasedpolynomials

Cosmas Mafusire and Tjaart Krüger

Doc ID: 312360 Received 03 Nov 2017; Accepted 05 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: The concept of orthonormal vector circle polynomials is revisited by deriving a set from the Cartesian gradient ofZernike polynomials in a unit circle using a matrix-based approach. The heart of this model is a closed-form matrixequation of the gradient of Zernike circle polynomials expressed as a linear combination of lower-order Zernikecircle polynomials related through a gradient matrix. This is a sparse matrix whose elements are two-dimensionalstandard basis transverse Euclidean vectors. Using the outer product form of the Cholesky decomposition, thegradient matrix is used to calculate a new matrix which we used to express the Cartesian gradient of the Zernikecircle polynomials as a linear combination of orthonormal vector circle polynomials. Since this new matrix issingular, the orthonormal vector polynomials are recovered by reducing the matrix to its row echelon form usingthe Gauss-Jordan elimination method. We extend the model to derive orthonormal vector general polynomialswhich are orthonormal in a general pupil by performing a similarity transformation on the gradient matrix to giveits equivalent in the general pupil. The outer form of the Gram-Schmidt procedure and the Gauss-Jordanelimination method are then applied to the general pupil to generate the orthonormal vector general polynomialsfrom the gradient of the orthonormal Zernike-based polynomials. The performance of the model is demonstratedwith a simulated wavefront in a square pupil inscribed in a unit circle.

What is a troland?

Larry Thibos, Norberto López-Gil, and Arthur Bradley

Doc ID: 321431 Received 07 Feb 2018; Accepted 02 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: Trolands are a widely used measure of retinal illuminance in vision science and visual optics, but disagreements exist for the definition and interpretation of this photometric unit. The purpose of this communication is to resolve the confusion by providing a sound conceptual basis for interpreting trolands as a measure of angular flux density incident upon the retina. Using a simplified optical analysis, we show that the troland value of an extended source is the intensity in micro-candelas of an equivalent point source located at the eye’s posterior nodal point that produces the same illuminance in the retinal image as does the extended source. This optical interpretation of trolands reveals that total light flux in the image of an extended object is the product of the troland value of the source and the solid angle subtended by the source at the first nodal point, independent of eye size.

A GPU implementation for Spline Based Wavefront Reconstruction

Elisabeth Brunner, Cornelis De Visser, Cornelis Vuik, and Michel Verhaegen

Doc ID: 320064 Received 19 Jan 2018; Accepted 30 Mar 2018; Posted 03 Apr 2018  View: PDF

Abstract: The paper presents an adaptation of the Distributed Spline based ABerration REconstruction method for Shack-Hartmann slope measurements to extremely large-scale adaptive optics systems and the execution on graphics processing units (GPUs). The introduction of a hierarchical multi-level scheme for the elimination of piston offsets between the locally computed wavefront estimates solves the piston error propagation observed for large number of partitions with the original version. In order to obtain a fully distributed method for wavefront correction, the projection of the phase estimates is locally approximated and applied in a distributed fashion, providing stable results for low and medium actuator coupling. An implementation of the method with the parallel computing platform CUDA exploits the inherently distributed nature of the algorithm. With a standard off-the-shelf GPU, the computation of the AO correction updates is accomplished in several milliseconds for the benchmark case of a 200 x 200 SH array.

A new optimization model for multiplicative noise and blur removebased on Gaussian curvature regularization

Fuquan Ren and Roberta Rui Zhou

Doc ID: 320014 Received 17 Jan 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: In this paper, we focus on the restorations of images that are simultaneously blurred andcorrupted by multiplicative noise. Firstly, we introduce a variational restoration model con-sisting of the convex data fitting term and the Gaussian curvature of the image as regularizerfor removing multiplicative Gamma noise, since it is able to minimize the staircase eectswhile preserving sharp edges, textures and other fine image details. Then, we propose com-puting the minimizers of our restoration functionals by applying the augmented Lagrangemultiplier method with a splitting techniques. The numerical results in this paper show thatour method has the potential to outperform the other approaches in multiplicative noiseremoval with deblurring simultaneously.

Optical Constants and Electrochromic Characteristics of HxMoO3 and LixMoO3 Bronzes

Zahid Hussain

Doc ID: 315557 Received 12 Dec 2017; Accepted 28 Mar 2018; Posted 03 Apr 2018  View: PDF

Abstract: Ellipsometric concentration dependent data of ZxMoO3 (Z=H+, Li+) bronze thin films areinterpreted from different prospects to unravel a detailed account of electrochromiccharacteristics. From the linear parts of the electronic energy loss functions (–1/ε), and from thedips in the optical density data, it is very difficult to decide about crystallographic phase shifts inthese bronzes, simply because of the difficulty of the structural determination of thesemicrocrystalline materials. MoO3 bronze thin films are found to have high electrochromicefficiency, and therefore require higher charge density, and less substoichiometry, to obtain thesame contrast ratio as observed in tungsten bronze thin films.The values of oscillator strengths, dipole strengths, and the degrees of delocalization of polaronwave functions have been calculated at different doping levels, and all are found to reveal thecharacteristics of localized in-band gap states of electrons, and do not give any symptom offormation of Bloch states in these bronzes even at higher values of concentration, x.

Temporal modes of stationary and pulsed quasistationary electromagnetic beams

Lutful Ahad, Jari Turunen, Ari Tapio Friberg, and Tero Setala

Doc ID: 319842 Received 15 Jan 2018; Accepted 14 Mar 2018; Posted 15 Mar 2018  View: PDF

Abstract: We present a novel time-domain coherent-mode representation for random, stationary electromagneticbeams. We subsequently introduce random, quasistationary pulsed electromagnetic beams and developan analogous (pseudo) mode decomposition for them as well. The former decomposition is valid providedthe time window in which the field is considered is much longer than the coherence time, while thelatter requires the field to vanish outside the window. For stationary beams the theory is demonstratedby an example illustrating the role of polarization in the representation. In both cases the data neededfor the construction of the mode decomposition is straightforward to measure. The formalisms enable totreat random vector-light beams in time domain in terms of deterministic fields. We expect that the modalrepresentations will find a wide range of applications in problems involving spatiotemporal propagationof temporally partially coherent light in optical systems.

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