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Bonding, antibonding and tunable optical forces in asymmetric membranes

OPTICS EXPRESS 2011年第3期19卷 2225-2241页

作者： Rodriguez, Alejandro W. McCauley, Alexander P. Hui, Pui-Chuen Woolf, David Iwase, Eiji Capasso, Federico Loncar, Marko Johnson, Steven G. MIT Dept Math Cambridge MA 02139 USA Harvard Univ Sch Engn & Appl Sci Cambridge MA 02138 USA MIT Dept Phys Cambridge MA 02139 USA

We demonstrate that tunable attractive (bonding) and repulsive (anti-bonding) forces can arise in highly asymmetric structures coupled to external radiation, a consequence of the bonding/anti-bonding level repulsion of guided-wave resonances that was first predicted in symmetric systems. Our focus is a geometry consisting of a photonic-crystal (holey) membrane suspended above an unpatterned layered substrate, supporting planar waveguide modes that can couple via the periodic modulation of the holey membrane. Asymmetric geometries have a clear advantage in ease of fabrication and experimental characterization compared to symmetric double-membrane structures. We show that the asymmetry can also lead to unusual behavior in the force magnitudes of a bonding/antibonding pair as the membrane separation changes, including nonmonotonic dependences on the separation. We propose a computational method that obtains the entire force spectrum via a single time-domain simulation, by Fourier-transforming the response to a short pulse and thereby obtaining the frequency-dependent stress tensor. We point out that by operating with two, instead of a single frequency, these evanescent forces can be exploited to tune the spring constant of the membrane without changing its equilibrium separation. (C) 2011 Optical Society of America

关键词： computation methods Guided mode resonance Optical force Planar waveguides Resonant modes Waveguide modes

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Vector radiative transfer in a multilayer medium by natural element method

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2016年第4期33卷 576-588页

作者： Zhang, Yong Kim, Yong-Jun Yi, Hong-Liang Tan, He-Ping Harbin Inst Technol Sch Energy Sci & Engn 92 West Dazhi St Harbin 150001 Peoples R China Kimchaek Univ Technol Dept Phys Sci Pyongyang 950003 South Korea

The vector radiative transfer problem in a vertically multilayer scattering medium with spatial changes in the index of refraction is solved by the natural element method (NEM). The top boundary of the multilayer medium is irradiated by a collimated beam. In our model, the angular space is discretized by the discrete ordinates approach, and the spatial discretization is conducted by the Galerkin weighted residuals approach. In the solution procedure, the collimated component for the Stokes parameters is first solved by NEM, and then it is embedded into the vector radiative transfer equation for the diffuse component as a source term. To keep the consistency of the directions in all the layers, angular interpolation of the Stokes parameters at the interfaces is adopted. The NEM approach for the collimated component is first validated. Then, the classical coupled atmosphere-water system irradiated by different states of collimated beam is examined to verify the numerical performance of the method. Numerical results show that the NEM is accurate, flexible, and effective in solving polarized radiative transfer in a multilayer medium. Finally, polarized radiative transfer in a four-layer system is investigated and analyzed. (C) 2016 Optical Society of America

关键词： Radiative transfer computation methods Scattering Scattering particles

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Photonic information processing beyond Turing: an optoelectronic implementation of reservoir computing

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OPTICS EXPRESS 2012年第3期20卷 3241-3249页

作者： Larger, L. Soriano, M. C. Brunner, D. Appeltant, L. Gutierrez, J. M. Pesquera, L. Mirasso, C. R. Fischer, I. Univ Franche Comte Dept Opt UMR CNRS FEMTO ST 6174 F-25030 Besancon France UIB CSIC IFISC E-07122 Palma De Mallorca Spain Vrije Univ Brussel Appl Phys Res Grp APHY B-1050 Brussels Belgium IFCA UNICAN CSIC Inst Fis Cantabria E-39005 Santander Spain

Many information processing challenges are difficult to solve with traditional Turing or von Neumann approaches. Implementing unconventional computational methods is therefore essential and optics provides promising opportunities. Here we experimentally demonstrate optical information processing using a nonlinear optoelectronic oscillator subject to delayed feedback. We implement a neuro-inspired concept, called Reservoir Computing, proven to possess universal computational capabilities. We particularly exploit the transient response of a complex dynamical system to an input data stream. We employ spoken digit recognition and time series prediction tasks as benchmarks, achieving competitive processing figures of merit. (C) 2012 Optical Society of America

关键词： computation methods Diode lasers Neural networks Optical networks Optical neural systems Optical processing

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DATA-DEPENDENT SYSTEMS METHODOLOGY FOR NOISE-INSENSITIVE PHASE UNWRAPPING IN LASER INTERFEROMETRIC SURFACE CHARACTERIZATION

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 1994年第10期11卷 2584-2592页

作者： PANDIT, SM JORDACHE, N JOSHI, GA []Department of Mechanical Engineering–Engineering Mechanics Michigan Technological University 1400 Townsend Drive Houghton Michigan 49931

Phase unwrapping recovers the actual surface topography from a calculated phase map, which is often degraded by a combination of surface defects and measurement noise. Prevalent unwrapping techniques are unable to differentiate between the surface and noise-created discontinuities, resulting in an improper surface recovery. In our approach the stochastic nature of the phase map is used by the data-dependent systems (DDS) methodology to separate the surface from noisy measurements. The DDS methodology identifies an adequate autoregressive moving-average model representing the measured phase values. An adaptive thresholding scheme carries out the phase discontinuity removal from the model residuals, employing statistical outlier detection. We then recover the surface by using the model and clean residuals. The proposed technique is found useful for unwrapping especially noisy and degraded phase maps.

关键词： computation methods Industrial optical metrology Phase measurement Phase unwrapping Surface measurements Wavefronts

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Measurement of chromatic aberrations using phase retrieval

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2021年第12期38卷 1853-1865页

作者： Bergkoetter, Matthew D. Kruschwitz, Brian E. Bahk, Seung-Whan Fienup, James R. Univ Rochester Inst Opt Rochester NY 14627 USA NASA Goddard Space Flight Ctr Code 916 Greenbelt MD 20771 USA Univ Rochester Lab Laser Energet 250 East River Rd Rochester NY 14623 USA

We explore the feasibility of measuring chromatic aberrations using a technique based on phase retrieval, primarily for the purpose of diagnostics on the OMEGA EP laser. A computational model and optimization strategy are described, issues of numerical efficiency are addressed, and the potential limitations of the method are studied using mathematical analysis and Monte Carlo simulations. The algorithm performs well in simulation and yields encouraging results in a small-scale laboratory experiment. (c) 2021 Optical Society of America

关键词： Chromatic aberrations computation methods Computer simulation Fourier transforms Phase retrieval Picosecond pulses

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MULTILAYER MODAL METHOD FOR DIFFRACTION GRATINGS OF ARBITRARY PROFILE, DEPTH, AND PERMITTIVITY

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 1993年第12期10卷 2581-2591页

作者： LI, LF []Optical Sciences Center University of Arizona Tucson Arizona 85721

A numerically stable method is presented for the analysis of diffraction gratings of arbitrary profile, depth, and permittivity in conical mountings. It is based on the classical modal method and uses a stack of lamellar grating layers to approximate an arbitrary profile. A numerical procedure known as the R-matrix propagation algorithm is used to propagate the modal fields through the layers. This procedure renders the implementation of this new method completely immune to the numerical instability that is associated with the conventional propagation algorithm. Numerical examples including diffraction efficiencies of both dielectric and metallic gratings of depths that range from subwavelength to hundreds of wavelengths are presented. Information about the convergence and the computation time of the method is also included.

关键词： computation methods Diffraction efficiency Diffraction gratings Evanescent waves Gradient index optics Propagation methods

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Fast FRFT-based method for estimating physical parameters from Newton's rings

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APPLIED OPTICS 2019年第14期58卷 3926-3931页

作者： Guo, Zhen Lu, Ming-Feng Wu, Jin-Min Jin, Xiao-Wei Zhang, Feng Tao, Ran Beijing Inst Technol Sch Informat & Elect Beijing 100081 Peoples R China Beijing Key Lab Fract Signals & Syst Beijing 100081 Peoples R China Univ Delaware Dept Elect & Comp Engn Newark DE 19716 USA

By analyzing Newton's rings, often encountered in interferometry, using fractional Fourier transform (FRFT), we can estimate the physical parameters, such as the curvature radius of the spherical surface and the rings' center. However, parameter estimation from large images using FRFT consumes considerable time. We introduce an improved method that resamples the image before applying FRFT. Because Newton's rings are sparse in the FRFT domain, this method reduces the computational time without decreasing the accuracy. Experimental results show that compared to traditional FRFT-based algorithms, this method can estimate parameters in about 1.3 s when processing 1920 x 1080 pixel images. (C) 2019 Optical Society of America

关键词： computation methods Fourier transforms Fractional Fourier transforms Fringe analysis Image processing Refractive index

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Multiscale optical simulation settings: challenging applications handled with an iterative ray-tracing FDTD interface method

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APPLIED OPTICS 2016年第9期55卷 2224-2229页

作者： Leiner, Claude Nemitz, Wolfgang Schweitzer, Susanne Kuna, Ladislav Wenzl, Franz P. Hartmann, Paul Satzinger, Valentin Sommer, Christian Joanneum Res Forsch mbH Inst Surface Technol & Photon Franz Pichler Str 30 A-8160 Weiz Austria

We show that with an appropriate combination of two optical simulation techniques-classical ray-tracing and the finite difference time domain method-an optical device containing multiple diffractive and refractive optical elements can be accurately simulated in an iterative simulation approach. We compare the simulation results with experimental measurements of the device to discuss the applicability and accuracy of our iterative simulation procedure. (C) 2016 Optical Society of America

关键词： Diffraction gratings computational electromagnetic methods computation methods Optical devices Optical engineering

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Constrained pupil balance compensation for specific lithographic illuminator settings

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APPLIED OPTICS 2020年第19期59卷 5837-5844页

作者： Rui, Dawei Yang, Huaijiang Changchun Natl Extreme Precis Opt Co Ltd Changchun 130033 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China

Pupil energy balances have always been considered significant elements for emersion lithography generally due to the large angle of incidence and offset imaging field. Those imbalances impact on exposure uniformity and decay pattern resolution. To overcome such shortcomings, a study on pupil compensation is discussed in this manuscript. A computational method based on a constrained optimization solution is proposed. By using a self-designed optical model of a zoomed system incorporating axicon lenses, a series of computations are developed and discussed. Also, the validity of our compensation method has been fully verified by simulations under multiple illumination settings. (C) 2020 Optical Society of America

关键词： computation methods Diffractive optical elements Laser beams Lithography Optical surfaces Pupil

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computational method for deriving the geometric point spread function of an optical system

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APPLIED OPTICS 2010年第1期49卷 126-136页

作者： Liu, Chien-Sheng Lin, Psang Dain Natl Cheng Kung Univ Dept Mech Engn Tainan 70101 Taiwan Ind Technol Res Inst Laser Applicat Technol Ctr Tainan 734 Taiwan

The distribution of the ray density of the spot diagram formed in the image plane is called the geometric point spread function (PSF). It plays an important role in the image formation theory, since it describes the impulse response of an optical system to a source point. However, the literature contains very few techniques for deriving the PSF of optical systems. Accordingly, this study presents a method based on an irradiance model for computing the geometric PSF of an optical system by considering the energy conservation along a single light ray. It is shown that the proposed method obtains a reliable and accurate estimate of the PSF and enables the computation of the centroid and root-mean-square radius of the focus spot on the image plane. In addition, compared to existing ray-counting methods presented in the literature, in which the quality of the PSF solution depends on the number of rays traced and the grid size used to mesh the image plane, the proposed irradiance-based method requires just one tracing operation. Overall, the results presented in this study confirm that the proposed method provides an ideal solution for calculating the merit function and modulation transfer function of an optical system. (C) 2009 Optical Society of America

关键词： computation methods Image formation theory Modulation transfer function Optical systems Point spread function Ray tracing

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