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Thin-film interference filters illuminated by tilted apertures

APPLIED OPTICS 2020年第5期59卷 A112-A122页

作者： Goossens, Thomas Van Hoof, Chris Katholieke Univ Leuven Dept Elect Engn B-3001 Leuven Belgium IMEC VZW Kapeldreef 75 B-3001 Leuven Belgium

Thin-film interference filters can be illuminated by a circular aperture at different angles. Each situation produces a different transmittance spectrum. We present an analytical model that, for small tilt angles, predicts the change in transmittance for an arbitrary position of the filter in three-dimensional space. The model is extended to take into account higher-order harmonics. We also derive a formula to predict the change in central wavelength, and we validate our results by comparison with thin-film transfer-matrix calculations. A key property of our approach is that the model can be combined with empirical data to predict the transmittance without knowing the filter design. (C) 2019 Optical Society of America

关键词： computation methods Effective refractive index Image sensors Interference filters Refractive index Spectral imaging

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Exponential fourth order schemes for direct Zakharov-Shabat problem

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OPTICS EXPRESS 2020年第1期28卷 20-39页

作者： Medvedev, Sergey Vaseva, Irina Chekhovskoy, Igor Fedoruk, Mikhail SB RAS Inst Computat Technol Novosibirsk 630090 Russia Novosibirsk State Univ Novosibirsk 630090 Russia

Nowadays, improving the accuracy of computational methods to solve the initial value problem of the Zakharov-Shabat system remains an urgent problem in optics. In particular, increasing the approximation order of the methods is important, especially in problems where it is necessary to analyze the structure of complex waveforms. In this work, we propose two finite-difference algorithms of fourth order of approximation in the time variable. Both schemes have the exponential form and conserve the quadratic invariant of Zakharov-Shabat system. The second scheme allows applying fast algorithms with low computational complexity (fast nonlinear Fourier transform). (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： computation methods Discrete Fourier transforms Fast Fourier transforms Fourier transforms Inverse problems Mathematical methods

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Numerical experiments for exploring propagation effects in high-harmonic generation from dielectric thin films

Numerical experiments for exploring propagation effects in h...

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Conference on Lasers and Electro-Optics (CLEO)

作者： S. Yamada T. Otobe D. Freeman A. Kheifets K. Yabana Kansai Photon Science Institute National Institutes for Quantum Science and Technology (QST) Kyoto Japan Research School of Physics Australian National University Canberra ACT Australia Center for Computational Sciences University of Tsukuba Tsukuba Japan

First-principles calculations for nonlinear light propagation in laser-irradiated silicon thin films unveiled physical mechanisms determining properties of HHG in reflected and transmitted waves. Frequency-resolved an... 详细信息

ISBN: (纸本)9781957171258

关键词： computation methods High harmonic generation Light propagation Photon counting Thin film applications Thin films

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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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First-principle calculation of Chern number in gyrotropic photonic crystals

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OPTICS EXPRESS 2020年第4期28卷 4638-4649页

作者： Zhao, Ran Xie, Guo-Da Chen, Menglin L. N. Lan, Zhihao Huang, Zhixiang Sha, Wei E., I Anhui Univ Key Lab Intelligent Comp & Signal Proc Minist Educ Hefei 230039 Peoples R China Dept Educ Anhui Prov Key Lab Electromagnet Environm Sensing Hefei 230039 Peoples R China Univ Hong Kong Dept Elect & Elect Engn Hong Kong Peoples R China UCL Dept Elect & Elect Engn London England Zhejiang Univ Coll Informat Sci Elect Engn Key Lab Micronano Elect Devices & Smart Syst Zhej Hangzhou 310027 Peoples R China

As an important figure of merit for characterizing the quantized collective behaviors of the wavefunction, Chern number is the topological invariant of quantum Hall insulators. Chern number also identifies the topological properties of the photonic topological insulators (PTIs), thus it is of crucial importance in PTI design. In this paper, we develop a first principle computatioal method for the Chern number of 2D gyrotropic photonic crystals (PCs), starting from the Maxwell's equations. Firstly, we solve the Hermitian generalized eigenvalue equation reformulated from the Maxwell's equations by using the full-wave finite-difference frequency-domain (FDFD) method. Then the Chern number is obtained by calculating the integral of Berry curvature over the first Brillouin zone. Numerical examples of both transverse-electric (TE) and transverse-magnetic (TM) modes are demonstrated, where convergent Chern numbers can be obtained using rather coarse grids, thus validating the efficiency and accuracy of the proposed method. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： computation methods Condensed matter Electric fields Magnetic fields Material properties Photonic crystals

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Fast method for calculating a curved hologram in a holographic display

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OPTICS EXPRESS 2020年第8期28卷 11290-11300页

作者： Kang, Ruidan Liu, Juan Pi, Dapu Duan, Xinhui Beijing Inst Lechnol Sch Opt & Photon Beijing Engn Res Ctr Mixed Real & Adv Display Beijing 100081 Peoples R China

A curved hologram can increase the view angle in a holographic display. The huge data processing and curved computer-generated hologram (CCGH) computation time is still a challenge for real-time display. Here, we propose two fast methods to accelerate the computation. The first one is a diffraction compensation (DC) method where the diffraction calculation is from the wave-front recording plane (WRP) to a CCGH. The other is an approximate compensation (AC) method that adds a phase difference distribution to the WRP to obtain the CCGH. Numerical simulations and optical experiments are performed, which demonstrate that the two methods are feasible and the computation time is dramatically reduced. The AC method can further reduce time significantly compared with the DC method. And the image quality for proposed methods is similar. It is expected that these fast methods can be combined with curved display screen and flexible display materials in the future. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： computation methods Holographic displays Holographic recording Image quality Numerical simulation Phase modulation

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zOPT: an open source optical projection tomography system and methods for rapid 3D zebrafish imaging

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BIOMEDICAL OPTICS EXPRESS 2020年第8期11卷 4290-4305页

作者： Zhang, Hanqing Waldmann, Laura Manuel, Remy Boije, Henrik Haitina, Tatjana Allalou, Amin Uppsala Univ Div Visual Informat & Interact Dept Informat Mchnol S-75105 Uppsala Sweden SciLifeLab BioImage Informat Facil S-75105 Uppsala Sweden Uppsala Univ Dept Organismal Biol S-75236 Uppsala Sweden Uppsala Univ Dept Neurosci S-75124 Uppsala Sweden

Optical projection tomography (OPT) is a 3D imaging alternative to conventional microscopy which allows imaging of millimeter-sized object with isotropic micrometer resolution. The zebrafish is an established model organism and an important tool used in genetic and chemical screening. The size and optical transparency of the embryo and larva makes them well suited for imaging using OPT. Here, we present an open-source implementation of an OPT platform, built around a customized sample stage, 3D-printed parts and open source algorithms optimized for the system. We developed a versatile automated workflow including a two-step image processing approach for correcting the center of rotation and generating accurate 3D reconstructions. Our results demonstrate high-quality 3D reconstruction using synthetic data as well as real data of live and fixed zebrafish. The presented 3D-printable OPT platform represents a fully open design, low-cost and rapid loading and unloading of samples. Our system offers the opportunity for researchers with different backgrounds to setup and run OPT for large scale experiments, particularly in studies using zebrafish larvae as their key model organism. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： computation methods Image processing Image quality Image reconstruction Reconstruction algorithms Three dimensional imaging

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Characterization of natural frequencies from nanoscale tissue oscillations using dynamic optical coherence elastography

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BIOMEDICAL OPTICS EXPRESS 2020年第6期11卷 3301-3318页

作者： Lan, Gongpu Larin, Kirill, V Aglyamov, Salavat Twa, Michael D. Foshan Univ Sch Phys & Optoelect Engn Foshan 528000 Guangdong Peoples R China Univ Alabama Birmingham Sch Optometry Birmingham AL 35290 USA Univ Houston Coll Optometry Houston TX 77204 USA Univ Houston Biomed Engn Houston TX 77204 USA Univ Houston Mech Engn Houston TX 77204 USA

We demonstrate the use of OCT-based elastography for soft-tissue characterization using natural frequency oscillations. Sub-micrometer to sub-manometer oscillations were induced in tissue phantoms and human cornea in vivo by perpendicular air-pulse stimulation and observed by common-path OCT imaging (sensitivity: 0.24 nm). Natural frequency and damping ratio were acquired in temporal and frequency domains using a single degree of freedom method. The dominant natural frequency was constant for different stimulation pressures (4-32 Pa) and measured distances (0.3-5.3 mm), and decreased as the sample thickness increased. The dominant natural frequencies of 0.75-2% agar phantoms were 127-774 Hz (mean coefficient of variation [CV]: 0.9%), and correlated with the square root of Young's moduli (16.5-117.8 kPa, mean CV: 5.8%). These preliminary studies show repeatable in vivo corneal natural frequency measurements (259 Hz, CV: 1.9%). This novel OCE approach can distinguish tissues and materials with different mechanical properties using the small-amplitude tissue oscillation features, and is suitable for characterizing delicate tissues in vivo such as the eye. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： computation methods Imaging techniques In vivo imaging Propagation methods Tissue Wave propagation

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Automatic estimation of human blood pressure based on the joint analysis of morphological and spectral parameters of the photoplethysmogram

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JOURNAL OF OPTICAL TECHNOLOGY 2020年第12期87卷 750-755页

作者： Zaluskaya, V. S. Karaseva, E. A. Lutsiv, V. R. ITMO Univ St Petersburg Russia Russian Acad Sci Pavlov Inst Physiol St Petersburg Russia St Petersburg State Univ Aerosp Instrumentat St Petersburg Russia

A method for the automatic assessment of the systolic and diastolic blood pressure of people by means of a joint analysis of spectral and morphological features of the pulse waveform on a photoplethysmogram is proposed. For extraction of the used features, algorithms have been developed for the preliminary processing of the original photoplethysmogram signal, its automatic division into periods corresponding to individual cardiac cycles, and the selection of characteristic features of the pulse waveform in each period. The selected signal periods are used to calculate the spectral characteristics of the photoplethysmogram, and the expediency of using triplets of successive cycles for this purpose is shown experimentally. The parameters calculated from the features of the pulse waveform and its calculated spectral characteristics are automatically analyzed using a specially trained artificial neural network, which forms an estimate of the patient's systolic and diastolic blood pressure at the output. The expediency of automatic determination of blood pressure based on the joint analysis of spectral and morphological characteristics of photoplethysmograms is shown experimentally. (c) 2021 Optical Society of America

关键词： Blood computation methods Electromagnetic radiation Light intensity Microoptical devices Neural networks

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On modeling of plasmonic devices: overview

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2020年第11期37卷 A163-A174页

作者： Said, Afaf Atia, Khaled S. R. Obayya, S. S. A. Zewail City Sci & Technol Ctr Photon & Smart Mat Giza 12578 Egypt Univ Ottawa Adv Res Complex Ottawa ON K1N 6N5 Canada

Plasmonics offers strong light localization into subwavelength dimensions beyond the diffraction limit. Therefore, plasmonics has a significant impact on realizing nanoscale photonic devices for a wide range of applications such as integrated optics, sensing, solar cells, and microscopy. The computational modeling of plasmonic devices provides a fundamental understanding of the relying physics. However, computational modeling of these devices is still a challenge as some of the existing modeling techniques fail to capture the correct behavior of plasmonic devices. In this regard, this paper focuses on reviewing the existing computational modeling tools for analyzing plasmonic devices and highlighting their salient features and shortcomings. (C) 2020 Optical Society of America

关键词： computation methods Computer simulation Diffraction limit Integrated optics Solar cells Surface plasmons

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