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Accepted papers to appear in an upcoming issue

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Tight focusing of femtosecond radially polarized light pulses through a dielectric interface

Jixiong Pu, Ziyang chen, Jianhua Shu, Haosen Pu, and Zhili LIN

Doc ID: 240024 Received 30 Apr 2015; Accepted 29 Jul 2015; Posted 30 Jul 2015  View: PDF

Abstract: Based on Richards-Wolf vector diffraction theory, we have derived the expressions for the electric field and the propagation velocity of femtosecond radially polarized light pulses focused by a high numerical aperture (NA) objective. The intensity distribution in the focus, the wavefront spacings and propagation velocity variation near the focus are investigated in detail by using numerical calculations. It is found that the propagation velocity of focused ultrashort light pulses changes dramatically near the focus, and the propagation velocity of the focused laser pulse is strongly dependent on the NA of an objective and the refractive index of media. Moreover, the usual propagation velocity of light pulses, as expected, decreases as the refractive index of media increases.

Overlap Relation Between Free Space Laguerre Gaussian Modes and Step Index Fiber Modes

Robert Brüning, Yingwen Zhang, Melanie McLaren, Michael Duparré, and Andrew Forbes

Doc ID: 243373 Received 19 Jun 2015; Accepted 29 Jul 2015; Posted 30 Jul 2015  View: PDF

Abstract: We investigated the overlap relation of the free space Laguerre Gaussian modes to the corresponding linearly polarized modes of a step index fiber. To maximize the overlap for an efficient coupling of the free space modes into a fiber, the scale dependent overlap was theoretically and experimentally determined. The presented studies paves the way for further improvement of free space to fiber optical connections.

Electrically thin at lenses and reflectors

Omar Ramahi, Miguel Ruphuy, and Omar Siddiqui

Doc ID: 242670 Received 10 Jun 2015; Accepted 28 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: We introduce electrically-thin dielectric lenses and reflectors that focus a plane wave based on the principles of phase compensation and constructive wave interference. Phase compensation is achieved by arranging thin rectangular slabs having different dielectric permittivity according to a permittivity profile obtained through analytic design equations. All incident rays parallel to the optical axis converge to a focal point with equalized optical paths resulting in constructive interference. Plane wave simulations indicate strong focusing even in the presence of impedance mismatch between free space and the dielectric layers comprising the lens. We demonstrate focusing at 9.45 GHz using a lens fabricated with commercially available dielectric materials. In addition to focusing, the at lens proposed here demonstrates relatively high power gain at the focal point. We also present a flat reflector based on the same concept. We believe that the proposed dielectric lens and reflector are strong candidates to replace heavy metallic dishes and reflectors used in a variety of applications especially satellites.

High-precision computation of optical propagation in inhomogeneous waveguides

Jianxin Zhu and Guanjie Wang

Doc ID: 237294 Received 07 Apr 2015; Accepted 26 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: In this paper, based on a new treatment for local base transformation, a modified operator marching method is provided to accurately compute optical propagation in the inhomogeneous waveguide terminated by a perfectly matched layer. Compared with the adjoint operator method (AOM), higher-precision results of the optical propagation can be obtained in numerical simulations, which demonstrate the new treatment is much better than AOM. This technique is helpful to optimize the designs of the optical waveguides and the integrated optics devices.

Vignetting and Negative Dysphotopsia with Intraocular Lenses in “Far Peripheral Vision”

Michael Simpson

Doc ID: 242089 Received 01 Jun 2015; Accepted 23 Jul 2015; Posted 27 Jul 2015  View: PDF

Abstract: At very large visual angles, vignetting can occur at the edge of an intraocular lens (IOL) because it is much smaller than the natural crystalline lens that it replaces. Raytrace calculations show that by 80-90 degrees of input visual angle it is possible that about half the light is no longer focused by the IOL. This may create curved, peripheral, shadowlike regions, which are a clinical characteristic of negative dysphotopsia. The imaging characteristics for this “far peripheral vision” region are different from those of a phakic eye, whether or not negative dysphotopsia is experienced.

Intensity and effective beam width of partially-coherent Laguerre Gaussian beams through a turbulent atmosphere

Yonggen Xu, Yude Li, and xile zhao

Doc ID: 241112 Received 18 May 2015; Accepted 22 Jul 2015; Posted 22 Jul 2015  View: PDF

Abstract: The propagation properties of partially-coherent elegant Laguerre Gaussian beam (PC-eLGB) and partially-coherent standard Laguerre Gaussian beam (PC-sLGB) through the turbulent atmosphere are studied. Analytical formulae for the intensity and effective beam width (EBW) of the PC-eLGB and PC-sLGB through the turbulent atmosphere are derived based on the extended Huygens-Fresnel principle. The propagation properties of PC-eLGB and PC-sLGB through the turbulent atmosphere are studied numerically and comparatively. It is shown that PC-eLGB and PC-sLGB are less affected by the turbulent atmosphere than fully-coherent Laguerre Gaussian beam. Spreading of PC-eLGB and PC-sLGB with the different mode orders (m,n) is slower in the free space than the turbulent atmosphere, and PC-sLGB spreads rapidly than PC-eLGB through the free space and the turbulent atmosphere. The study results will be useful for the free space optical communications.

The Frequency Shift Between Near and Far-Field Scattering Resonances in Dielectric Particles

Alex Yuffa, Yael Gutierrez, Juan Sanz, Rodrigo alcaraz, Francisco González, Fernando Moreno, Gorden Videen, and Juan Sanz

Doc ID: 238568 Received 29 Apr 2015; Accepted 18 Jul 2015; Posted 20 Jul 2015  View: PDF

Abstract: The near-field electromagnetic scattering intensity resonances are redshifted in frequency with respect to their far-field counterparts. We derive simple, approximate, analytical formulas for this shift in the case of a plane wave interacting with a dielectric sphere. Numerical results comparing the approximate formulas to the numerically exact solutions show that the two are in good agreement. We also consider the Rayleigh limit of the formulas in order to gain more insight into the phenomenon.

Infrared and visible image fusion with spectral graph wavelet transform

Xiang Yan, Hanlin Qin, Jia Li, Huixin Zhou, and Jing-guo Zong

Doc ID: 234547 Received 11 Feb 2015; Accepted 16 Jul 2015; Posted 17 Jul 2015  View: PDF

Abstract: Infrared and visible image fusion technique is a popular topic in image analysis because it can integrate complementary information and obtain reliable and accurate description of scenes. Multiscale transform (MST) theory as a signal representation method is widely used in image fusion. In this paper, a novel infrared and visible image fusion method is proposed based on spectral graph wavelet transform (SGWT) and bilateral filter. The main novelty of this study is that SGWT is used for image fusion. On the one hand, source images are decomposed by SGWT in its transform domain. The proposed approach not only effectively preserves the details of different source images, but also excellently represents the irregular areas of the source images. On the other hand, a novel weighted average method based on bilateral filter is proposed to fuse low- and high-frequency subbands by taking advantage of spatial consistency of natural images. Experimental results demonstrate that the proposed method outperforms seven recently proposed image fusion methods in terms of both visual effect and objective evaluation metrics. 2015 Optical Society of America

Prediction of the spectral reflectance of laser-generated color prints by combination of an optical model and learning methods

David NEBOUY, Mathieu Hébert, Thierry Fournel, Nina Larina, and Jean-Luc Lesur

Doc ID: 237463 Received 03 Apr 2015; Accepted 15 Jul 2015; Posted 15 Jul 2015  View: PDF

Abstract: Recent color printing technologies based on the principle of revealing colors on pre-functionalized achromatic supports by laser irradiation offer advanced functionalities, especially for security applications. However, for such technologies the color prediction is challenging, compared to classic ink-transfer printing systems. The spectral properties of the coloring materials modified by the lasers are not precisely known and may strongly vary, depending on the laser settings, in a nonlinear manner. We show in this study, through the example of the Color Laser Marking technology based on laser-bleaching of a mixture of pigments, that the combination of an adapted optical reflectance model and learning methods to get the model’s parameters enables predicting the spectral reflectance of any printable color with rather good accuracy. Even though the pigment mixture is formulated from three colored pigments, an analysis of the dimensionality of the spectral space generated by CLM printing, shows that at least four spectral primaries are needed for accurate spectral reflectance predictions. By studying the influence of the number of calibration patches on the prediction accuracy, we can conclude that a reasonable number of 130 patches are enough to achieve good accuracy in this application.

Necessary and sufficient conditions for the appearance of a reflectance minimum at oblique incidence when unpolarized or circularly polarized light is reflected at a dielectric-conductor interface

Rasheed Azzam

Doc ID: 242459 Received 09 Jun 2015; Accepted 13 Jul 2015; Posted 14 Jul 2015  View: PDF

Abstract: For unpolarized or circularly polarized light incident at a dielectric-conductor interface, a reflectance minimum appears at oblique incidence if the normal-incidence intensity reflectance R0 is > 1/3 [Azzam and Alsamman, Appl. Opt. 53, 7885-7890 (2014)]. However, R0 > 1/3 is only a necessary but insufficient condition for the reflectance minimum to appear at non-normal incidence. The second condition, the subject of this study, restricts the normal-incidence reflection phase shift δ0 for incident s-polarized light to one of two non-overlapping bands: (I) 0 < δ0 < δ0max and (II) δ0min < δ0 < 180° that are associated with internal and external reflection, respectively. The dependence of δ0max and δ0min on R0 within each band is determined analytically.

Two-time coherence of pulse trains and the integrated degree of temporal coherence

Rahul Dutta, Ari Tapio Friberg, Goëry Genty, and Jari Turunen

Doc ID: 243129 Received 16 Jun 2015; Accepted 13 Jul 2015; Posted 17 Jul 2015  View: PDF

Abstract: We examine the temporal coherence properties of trains of non-identical short optical pulses in the framework of the second-order coherence theory of non-stationary light. Considering Michelson's interferometric measurement of temporal coherence, we demonstrate that time-resolved interferograms reveal the full two-time temporal coherence function of the partially coherent pulse train. We also show that the result given by the time-integrated Michelson interferogram equals the true degree of temporal coherence only when the pulse train is quasi-stationary, i.e., the coherence time is a small fraction of the pulse duration. True two-time and integrated coherence functions produced by specific models representing perturbed trains of mode-locked pulses and supercontinuum pulse trains produced in nonlinear fibers are illustrated.

Hyperspectral image denoising using the robust low-rank tensor recovery

Yong Ma, Li chang, Huang Jun, Mei Xiaoguang, and Jiayi Ma

Doc ID: 238296 Received 16 Apr 2015; Accepted 02 Jul 2015; Posted 02 Jul 2015  View: PDF

Abstract: Denoising is an important preprocessing step to further analyze the hyperspectral image (HSI), and many denoising methods have been used for the denoising of the HSI data cube. However, the traditional denoising methods are sensitive to outliers and non-Gaussian noise. In this paper, by utilizing the underlying low-rank tensor property of the clean HSI data and the sparsity property of the outliers and non-Gaussian noise, we propose a new model based on the robust low-rank tensor recovery (RLRTR), which can simultaneously remove the outliers and dierent types of noise: Gaussian noise, impulse noise, stripes, and so on. The proposed model can be solved by the alternating direction augmented Lagrangian (ADAL) method, and experiments on real hyperspectral images demonstrate that the proposed method is ecient for HSI denoising.

Detection of chromatic and luminance distortions in natural scenes

Ben Jennings, Frederick Kingdom, Samantha Menzies, and Karen Wang

Doc ID: 236440 Received 18 Mar 2015; Accepted 16 Jun 2015; Posted 17 Jun 2015  View: PDF

Abstract: A number of previous studies have measured visual thresholds for detecting spatial distortions applied to images of natural scenes. One of these measured sensitivity to sinusoidal spatial modulations of image scale (Bex, 2010). Here we consider the relative contribution of the chromatic and luminance layers of natural-scene images to sinusoidal scale distortion. We first report that when the distortion was applied to both luminance and chromatic layers, sensitivity did not depend on whether the undistorted comparison image was of the same or of a different scene. Next we report the effects of individually distorting one or other layer. When only the luminance layer was distorted, performance was the same irrespective of whether the chromatic layer was present, absent or phase scrambled, revealing that the chromatic layer in whatever form did not affect sensitivity. However when the chromatic layer was distorted, sensitivity was higher when the luminance layer was intact compared to when absent or phase-scrambled. Moreover, even when the chromatic layer was visibly distorted, it appeared to contribute little to the sense of distortion. We conclude (a) that observers have an in-built sense of how a normal image of a natural scene should appear, and (b) that both the appearance and detection of distortion is mediated predominantly by the luminance as opposed to chromatic layer.

Rigorous coupled wave analysis of acousto-optics with relativistic considerations

Guoqiang Xia, Weijian Zheng, Zhenggang Lei, and Ruolan Zhang

Doc ID: 235514 Received 25 Mar 2015; Accepted 11 Jun 2015; Posted 22 Jun 2015  View: PDF

Abstract: A relativistic analysis of acousto-optics is presented, and a rigorous coupled wave analysis is generalized for the diffraction of the acousto-optical effect. An acoustic wave generates a grating with temporally and spatially modulated permittivity, hindering direct applications of the rigorous coupled wave analysis for the acousto-optical effect. In a reference frame which moves with the acoustic wave, the grating is static and the medium moves and the coupled wave equations for the static grating may be derived. Floquet’s theorem is then applied to cast these equations into an eigen-problem. Using a Lorentz transformation, the electromagnetic fields in the grating region are transformed to the lab frame where the medium is at rest, and relativistic Doppler frequency shifts are introduced into various diffraction orders. In the lab frame, the boundary conditions are considered and the diffraction efficiencies of various orders are determined. This method is rigorous and general, and the plane waves in the resulting expansion satisfy the dispersion relation of the medium and are propagation modes. Properties of various Bragg diffractions are results, rather than preconditions, of this method. Simulations of an acousto-optical tunable filter made by paratellurite, TeO2, are given as examples.

(CV) Independence and interaction of luminance and chromatic contributions to spatial hyperacuity performance

Bonnie Cooper and Barry Lee

Doc ID: 198653 Received 30 Sep 2013; Accepted 02 Feb 2014; Posted 03 Feb 2014  View: PDF

Abstract: Here we test interactions of luminance and chromatic input to spatial hyperacuity mechanisms. First, we tested alignment with matching or mismatching (contrast polarity or modality) grating pairs that were adjusted to detection threshold. Thresholds with mismatched pairs were significantly elevated. Second, we determined alignment acuity as a function of luminance or chromatic contrast alone or in the presence of contrast pedestals. For in-phase pedestal conditions, performance followed the envelope of the more sensitive mechanism. However, polarity reversals revealed an asymmetric effect for luminance and chromatic conditions. This suggests that luminance can overrule chromatic mechanisms in hyperacuity; we interpret these findings in the context of spatial mechanisms.

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