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Optical Fiber Communications Conference and Exhibition (OFC)

作者： Liu, Haijiao Hua, Nan Li, Yao Li, Yanhe Zheng, Xiaoping Tsinghua Natl Lab Informat Sci & Technol TNList Beijing 100084 Peoples R China Tsinghua Univ Dept Elect Engn Beijing 10084 Peoples R China

We establish an analytical model to analyze the impact of "information distortion" caused by concurrent rerouting after a network failure. The estimate values derived from the analytical model agree well wit... 详细信息

ISBN: (纸本)9781943580071

关键词： computation methods Distortion Network survivability Network topology Optical networks Silicon

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Filtering and unwrapping doppler optical coherence tomography velocity maps

Filtering and unwrapping doppler optical coherence tomograph...

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computational Optical Sensing and Imaging, COSI 2016

作者： Xu, Yang Darga, Donald Smid, Jason Zysk, Adam M. Teh, Daniel Boppart, Stephen A. Scott Carney, P. Beckman Institute for Advanced Science and Technology University of Illinois at Urbana-Champaign UrbanaIL61801 United States Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States Diagnostic Photonics Inc. 222 West Merchandise Mart Plaza Suite 1230 ChicagoIL60654 United States Department of Computer Science University of Illinois at Urbana-Champaign UrbanaIL61801 United States Department of Bioengineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States

In this abstract, we describe two computational methods for filtering and unwrapping Doppler optical coherence tomography velocity maps, which enable extended measurement range of fluid velocity. We further demonstrat... 详细信息

ISBN: (纸本)9781943580156

关键词： computation methods Near infrared radiation Optical coherence tomography Refractive index Spatial filtering Spatial frequency

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Complex band structures of transition metal dichalcogenide monolayers with spin-orbit coupling effects

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JOURNAL OF PHYSICS-CONDENSED MATTER 2016年第35期28卷 355301-355301页

作者： Szczesniak, Dominik Ennaoui, Ahmed Ahzi, Said Hamad bin Khalifa Univ Qatar Energy & Environm Res Inst Qatar Fdn POB 5825 Doha Qatar

Recently, the transition metal dichalcogenides have attracted renewed attention due to the potential use of their low-dimensional forms in both nano- and opto-electronics. In such applications, the electronic and transport properties of monolayer transition metal dichalcogenides play a pivotal role. The present paper provides a new insight into these essential properties by studying the complex band structures of popular transition metal dichalcogenide monolayers (MX2, where M = Mo, W;X = S, Se, Te) while including spin-orbit coupling effects. The conducted symmetry-based tight-binding calculations show that the analytical continuation from the real band structures to the complex momentum space leads to nonlinear generalized eigenvalue problems. Herein an efficient method for solving such a class of nonlinear problems is presented and yields a complete set of physically relevant eigenvalues. Solutions obtained by this method are characterized and classified into propagating and evanescent states, where the latter states manifest not only monotonic but also oscillatory decay character. It is observed that some of the oscillatory evanescent states create characteristic complex loops at the direct band gap of MX2 monolayers, where electrons can directly tunnel between the band gap edges. To describe these tunneling currents, decay behavior of electronic states in the forbidden energy region is elucidated and their importance within the ballistic transport regime is briefly discussed.

关键词： electronic properties computation methods tunneling currents

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Narrow-band wavelength tunable filter based on asymmetric double layer metallic grating

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OPTICS EXPRESS 2015年第11期23卷 14434-14445页

作者： Liang, Yuzhang Peng, Wei Lu, Mengdi Chu, Shuwen Dalian Univ Technol Coll Phys & Optoelect Engn Dalian 116024 Peoples R China

In this paper, the optical properties of asymmetric double layer metallic gratings are presented theoretically. The asymmetric structure is achieved by two main factors: one corresponding to moving alternatively metal nanowires of the top layer metallic grating, the other corresponding to possessing different thickness of the top and down layer metallic gratings. Our proposed structure shows one remarkable narrow-band transmission dip at normal incidence, which is distinct different from that of symmetric structure. The results are further confirmed by using different numerical computation methods, and explained by the analytical model of Fano-like resonance. We find that, only when the thickness of the down layer metallic grating has certain fixed value, transmission dip can be transformed from two to only one dip even if the existence of symmetry breaking. However, the wavelength position of the dip can be easily controlled by adjusting the thickness of the top layer metallic grating without the need to modify the structure period, and the width of metal nanowire. Moreover, the influence of other structure parameters on the dip is also investigated. Surprisingly, in order to keep the appearance of one dip in the transmission spectrum of designed structure, there is a good linear approximation between the refractive index of waveguide layer and the thickness of down layer metallic grating, and the relation of waveguide layer thickness and the thickness of down layer metallic grating satisfy secondary polynomial fitting. This work can be used to develop subwavelength metallic-grating-based and narrow-band tunable wavelength filters. (C) 2015 Optical Society of America

关键词： Bandpass filters computation methods Fano resonance Guided mode resonance Refractive index Tunable filters

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Quantitative evaluation on internal seeing induced by heat-stop of solar telescope

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OPTICS EXPRESS 2015年第15期23卷 19980-19995页

作者： Liu, Yangyi Gu, Naiting Rao, Changhui Chinese Acad Sci Inst Opt & Elect Lab Adapt Opt Chengdu 610209 Peoples R China Chinese Acad Sci Key Lab Adapt Opt Chengdu 610209 Peoples R China Chinese Acad Sci Grad Univ Beijing 100049 Peoples R China

heat-stop is one of the essential thermal control devices of solar telescope. The internal seeing induced by its temperature rise will degrade the imaging quality significantly. For quantitative evaluation on internal seeing, an integrated analysis method based on computational fluid dynamics and geometric optics is proposed in this paper. Firstly, the temperature field of the heat-affected zone induced by heat-stop temperature rise is obtained by the method of computational fluid dynamics calculation. Secondly, the temperature field is transformed to refractive index field by corresponding equations. Thirdly, the wavefront aberration induced by internal seeing is calculated by geometric optics based on optical integration in the refractive index field. This integrated method is applied in the heat-stop of the Chinese Large Solar Telescope to quantitatively evaluate its internal seeing. The analytical results show that the maximum acceptable temperature rise of heat-stop is up to 5 Kelvins above the ambient air at any telescope pointing directions under the condition that the root-mean-square of wavefront aberration induced by internal seeing is less than 25nm. Furthermore, it is found that the magnitude of wavefront aberration gradually increases with the increase of heat-stop temperature rise for a certain telescope pointing direction. Meanwhile, with the variation of telescope pointing varying from the horizontal to the vertical direction, the magnitude of wavefront aberration decreases at first and then increases for the same heat-stop temperature rise. (C) 2015 Optical Society of America

关键词： Astronomical telescopes computation methods Geometric optics Large telescopes Solar telescopes Wavefront aberrations

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Light-extraction efficiency control in AlGaN-based deep-ultraviolet flip-chip light-emitting diodes: a comparison to InGaN-based visible flip-chip light-emitting diodes

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OPTICS EXPRESS 2015年第16期23卷 20340-20349页

作者： Lee, Keon Hwa Park, Hyun Jung Kim, Seung Hwan Asadirad, Mojtaba Moon, Yong-Tae Kwak, Joon Seop Ryou, Jae-Hyun LG Innotek Co Dept LED Business Paju 413901 South Korea Univ Houston Dept Mech Engn Houston TX 77204 USA Sunchon Natl Univ Dept Printed Elect Engn Jeonnam 540742 South Korea Univ Houston Mat Sci & Engn Program Houston TX 77204 USA Univ Houston Texas Ctr Superconduct Houston TX 77204 USA

We study light-extraction efficiency (LEE) of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) using flip-chip (FC) devices with varied thickness in remaining sapphire substrate by experimental output power measurement and computational methods using 3-dimensional finite-difference time-domain (3D-FDTD) and Monte Carlo ray-tracing simulations. Light-output power of DUV-FCLEDs compared at a current of 20 mA increases with thicker sapphire, showing higher LEE for an LED with 250-mu m-thick sapphire by similar to 39% than that with 100-mu m-thick sapphire. In contrast, LEEs of visible FCLEDs show only marginal improvement with increasing sapphire thickness, that is, similar to 6% improvement for an LED with 250-mu m-thick sapphire. 3D-FDTD simulation reveals a mechanism of enhanced light extraction with various sidewall roughness and thickness in sapphire substrates. Ray tracing simulation examines the light propagation behavior of DUV-FCLED structures. The enhanced output power and higher LEE strongly depends on the sidewall roughness of the sapphire substrate rather than thickness itself. The thickness starts playing a role only when the sapphire sidewalls become rough. The roughened surface of sapphire sidewall during chip-separation process is critical for TM-polarized photons from AlGaN quantum wells to escape in lateral directions before they are absorbed by p-GaN and Au-metal. Furthermore, the ray tracing results show a reasonably good agreement with the experimental result of the LEE. (C) 2015 Optical Society of America

关键词： computation methods Light propagation Photonic crystals Quantum wells Ray tracing Spontaneous emission

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A time delay correction technique for SS-OCT

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JOURNAL OF X-RAY SCIENCE AND TECHNOLOGY 2015年第6期23卷 783-789页

作者： Wang, Yi Chen, Xiaodong Chen, Xiaojie Yu, Daoyin Tianjin Univ Minist Educ Key Lab Optoelect Informat & Tech Sci Tianjin 300072 Peoples R China

BACKGROUND: K-trigger signals from light source or external Mach-Zehnder interferometer are commonly used in swept source optical coherence tomography (SS-OCT) to achieve interference signal sampling and resolution enhancement. But extra signal transmission time is required due to the increased complexity of interference system using k-trigger signals, resulting in a misalignment (a.k.a., time delay) between the k-trigger and the interference signals. OBJECTIVE: The objective of this paper is to propose a numerical technique to correct the time delay between these two signals. methods: The time delay is iterated in this technique and each iterated correction result is evaluated through calculating the full width at half maximum (FWHM) of peaks in time-domain. The precise alignment between the k-trigger and interference signals coincides with the minimum value of FWHM. RESULTS: The experimental results show that the FWHM can be improved by up to 50% using this time delay correction technique. CONCLUSIONS: The proposed technique assists to provide precise sample tomography, thus enhancing the way of understanding sample characteristic.

关键词： Optical coherence tomography (OCT) fourier optics and signal processing nonlinear optical signal processing resolution computation methods

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Fitting discrete aspherical surface sag data using orthonormal polynomials

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OPTICS EXPRESS 2015年第17期23卷 22404-22413页

作者： Hilbig, David Ceyhan, Ufuk Henning, Thomas Fleischmann, Friedrich Knipp, Dietmar Univ Appl Sci Bremen I3M D-28199 Bremen Germany ePholution GmbH D-28199 Bremen Germany Jacobs Univ Bremen Ctr Adv Syst Engn Elect Devices & Nanophoton Lab D-28759 Bremen Germany

Characterizing real-life optical surfaces usually involves finding the best-fit of an appropriate surface model to a set of discrete measurement data. This process can be greatly simplified by choosing orthonormal polynomials for the surface description. In case of rotationally symmetric aspherical surfaces, new sets of orthogonal polynomials were introduced by Forbes to replace the numerical unstable standard description. From these, for the application of surface retrieval using experimental ray tracing, the sag orthogonal Q(con)-polynomials are of particular interest. However, these are by definition orthogonal over continuous data and may not be orthogonal for discrete data. In this case, the simplified solution is not valid. Hence, a Gram-Schmidt orthonormalization of these polynomials over the discrete data set is proposed to solve this problem. The resulting difference will be presented by a performance analysis and comparison to the direct matrix inversion method. (C) 2015 Optical Society of America

关键词： computation methods Freeform surfaces Numerical analysis Optical surfaces Ray tracing Zernike polynomials

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Composite method for precise freeform optical beam shaping

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APPLIED OPTICS 2015年第31期54卷 9364-9369页

作者： Feng, Zexin Froese, Brittany D. Liang, Rongguang Univ Arizona Coll Opt Sci Tucson AZ 85721 USA Tsinghua Univ Dept Precis Instrument Beijing 100084 Peoples R China Univ Hts New Jersey Inst Technol Dept Math Sci Newark NJ 07102 USA

We present a composite freeform surface construction method for creating a high-accuracy irradiance distribution from a given incident beam under the influence of diffraction. The main idea is that we first determine a fully continuous freeform surface estimate by solving a standard Monge-Ampere equation and then refine it using an iterative Fourier-transform algorithm associated with over-compensation. Although this method can only be implemented in the paraxial approximation, it can significantly simplify the design and is applicable to many examples that fulfill this restriction. The resulting optical surface, unwrapped from the final phase, is an unusual discontinuous freeform surface that can produce very promising performances in terms of surface roughness and irradiance accuracy. (C) 2015 Optical Society of America

关键词： Diffractive optics Geometric optical design computation methods Nonimaging optics Inverse problems Phase retrieval

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High-precision computation of optical propagation in inhomogeneous waveguides

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2015年第9期32卷 1653-1660页

作者： Zhu, Jianxin Wang, Guanjie Zhejiang Univ Dept Math Hangzhou 310027 Zhejiang Peoples R China

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), high-precision results of the optical propagation can be obtained in numerical simulations, which demonstrate that the new treatment is much better than the AOM. This technique is helpful to optimize the designs of the optical waveguides and the integrated optics devices. (C) 2015 Optical Society of America

关键词： computational electromagnetic methods Wave propagation Inhomogeneous optical media computation methods Waveguides planar

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