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20th Biennial IEEE Conference on Electromagnetic Field Computation (CEFC)

作者： Zhu, Xiaojie Di Rienzo, Luca Ma, Xikui Codecasa, Lorenzo Xi An Jiao Tong Univ Sch Elect Engn State Key Lab Elect Insulat & Power Equipment Xian Peoples R China Politecn Milan Dipartimento Elettron Informaz & Bioingn Milan Italy

ISBN: (数字)9781665468336

ISBN: (纸本)9781665468336

We apply the multilevel Monte Carlo (MLMC) method with the finite-difference time-domain method (FDTD) to estimate the probability density function (PDF) and the cumulative distribution function (CDF) of any quantity of interest for uncertainty quantification in electromagnetic problems. It is shown that, compared with the standard Monte Carlo FDTD (MC-FDTD), the MLMC-FDTD method can provide accurate estimations with high computational efficiency. In addition, as opposed to the polynomial chaos FDTD (PC-FDTD) method that suffers the curse of dimensionality or failure, the MLMC-FDTD method is more reliable.

关键词： finite-difference time-domain method multilevel Monte Carlo method probability density function uncertainty quantification

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Research on Near-Field Propagation Characteristics of Partial Discharge Electromagnetic Wave Signal in Switchgear

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ENERGIES 2023年第8期16卷 3372页

作者： Suo, Chunguang Zhao, Jingjing Wang, Lifeng Xu, Zhipeng Luo, Ruikang He, Mingxing Zhang, Wenbin Kunming Univ Sci & Technol Coll Sci Kunming 650504 Peoples R China Kunming Univ Sci & Technol Fac Civil Engn & Architecture Kunming 650504 Peoples R China Kunming Univ Sci & Technol Coll Mech & Elect Engn Kunming 650504 Peoples R China

In the authors' previous research, a new method for partial discharge detection in the switchgear based on near-field detection was proposed. The content of this paper is the continuation of the authors' previous research. In order to realize the reasonable layout of the near-field magnetic field probe for partial discharge detection in the switchgear, this paper simulates and analyzes the influence of the internal structure of the switchgear on the near-field propagation characteristics of the electromagnetic wave signal generated by partial discharge, and determines the installation position of the near-field probe in the switchgear. Firstly, the propagation characteristics of electromagnetic wave signals in the different media of the switchgear are analyzed, and the switchgear model is established. Then, based on the finite difference time domain method, the influence of different devices in the switchgear on the near-field propagation of the partial discharge electromagnetic wave signal is simulated. The simulation results show that the current transformer, insulator, busbar and cabinet all obviously attenuate the amplitude of the near-field electromagnetic wave signals generated by partial discharge, and the insulator causes obvious signal distortion. Finally, it is determined that the near-field probe can be installed on the inner wall or the right wall near the bottom plate of the switchgear.

关键词： finite-difference time-domain method near-field propagation characteristics partial discharge signal switchgear

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Ultracompact all-optical full adders using an interference effect based on 2D photonic crystal nanoring resonators

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JOURNAL OF COMPUTATIONAL ELECTRONICS 2021年第1期20卷 409-418页

作者： Mohammadi, Masoud Fallahi, Vahid Seifouri, Mahmood Shahid Rajaee Teacher Training Univ Fac Elect Engn Tehran Iran

Given the special place of hybrid logic circuits such as all-optical full adders in next-generation digital systems, a new kind of these structures using two-dimensional (2D) photonic crystals (2D-PC) is designed and simulated herein. The proposed structure is made of a hexagonal nanoring resonator (NRR), a coupling rod, and several waveguides. In this all-optical full adder, the mechanism of the interference effect in the PCs is used to simplify and minimize the structure. To make the structure flexible, the radius of the dielectric rod in the whole structure and the NRR are considered based on a lattice constant of 0.2a and 0.04a, respectively. The structure is operated at a wavelength of 1550 nm, considering the value of the power entering the waveguides and that exiting the Carry and Sum ports. To analyze the all-optical full adder, the plane-wave expansion method and finite-difference time-domain method are applied respectively to calculate the bandgap diagram and obtain the transmission and propagation of the optical field. In the proposed structure, the contrast ratio at the Carry and is been investigated in a unique and novel way, yielding values of 10.68 and 9.03 dB, respectively. In addition, the maximum and minimum response time for the Carry and Sum are obtained as 1.6 and 0.75 ps, respectively. The total footprint of the structure is about 183 mu m(2). Due to its ultracompact size, low power consumption, fast response time, and simple structure, this all-optical full adder is suitable for use in low-power optical integrated circuits.

关键词： Full adder Photonic crystals Contrast ratio Response time finite-difference time-domain method

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Influence of Different Crack Factors on Acoustic Wave Signals Using Orthogonal Analysis

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MATERIALS EVALUATION 2021年第2期79卷 136-148页

作者： Wang, Xianghong Liu, Jun Luo, Zhimin Hu, Hongwei Changsha Univ Sci & Technol Hunan Prov Key Lab Intelligent Mfg Technol High P Changsha 410004 Peoples R China Changsha Univ Sci & Technol Hunan Prov Res Ctr Safety Control Technol & Equip Changsha 410004 Peoples R China

The existence of cracks in key components of engineering equipment is a huge threat to the safe operation of the equipment. The influence of four factors (length, location, orientation, and width of the crack) on the attenuation characteristic of signal propagation is studied through simulation and experiment. The orthogonal experimental design is applied to design the simulation scheme, and the signal affected by the four factors is simulated by the finite-difference time-domain method. The degree of influence of the different factors is evaluated by conducting an analysis of range and an analysis of variance. The results show that the influence of crack length and location on signal relative attenuation is more remarkable according to the significance level alpha = 0.05, followed by crack orientation and crack width. The attenuation trend in the experimental results is similar to the simulation. Therefore, the longer the crack length is, the easier it is to be detected by the acoustic wave technique, while the effect of crack orientation and crack width on identifying cracks is limited. The study successfully establishes the relationship between signal parameters and crack factors and offers a theoretical foundation for evaluating the status of cracks in key components.

关键词： crack factors orthogonal experimental design finite-difference time-domain method wave propagation

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Electron vortex beams for chirality probing at the nanoscale

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Physical Review Applied 2024年第5期22卷 054017页

作者： Neli Laštovičková Streshkova Petr Koutenský Martin Kozák Department of Chemical Physics and Optics Faculty of Mathematics and Physics

In this work we propose a method for probing the chirality of nanoscale electromagnetic near fields utilizing the properties of a coherent superposition of free-electron vortex states in electron microscopes. Electron beams optically modulated into vortices carry orbital angular momentum, thanks to which they are sensitive to the spatial phase distribution and topology of the investigated field. The sense of chirality of the studied specimen can be extracted from the spectra of the electron beam with nanoscale precision owing to the short picometer de Broglie wavelength of the electron beam. We present a detailed case study of the interaction of a coherent superposition of electron vortex states and the optical near field of a golden nanosphere illuminated by circularly polarized light as an example, and we examine the chirality sensitivity of electron vortex beams on intrinsically chiral plasmonic nanoantennae.

关键词： Angular momentum of light Chirality Near-field optics Plasmonics Coherent control Electromagnetic wave theory Electron microscopy finite-difference time-domain method

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Enabling superresolution detection via dispersion-induced time diffraction of evanescent waves

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Physical Review B 2024年第19期110卷 195436-195436页

作者： Kedi Wu Neng Wang Guo Ping Wang State Key Laboratory of Radio Frequency Heterogeneous Integration College of Electronics and Information Engineering Shenzhen University Shenzhen 518060 China

We propose a method for far-field superresolution detection based on the time diffraction of evanescent waves, without any external driving or pumping. time diffraction is induced by the turn-on effect of a laser beam, which creates an intrinsic temporal boundary, and relies on the nonlinear dispersion relation of evanescent waves in free space. By extending classical angular spectrum (AS) theory into the space-time domain, we theoretically investigate the time evolution of waves diffracted by subwavelength gratings. In addition to the stationary solution of traditional evanescent waves, we discover a high-frequency transient solution that decays over time but plays a crucial role in enabling superresolution. This transient wave creates a beat frequency in the temporal spectrum, allowing the retrieval of the grating period from far-field measurements. Our findings lay a theoretical foundation for the application of time-diffracted electromagnetic waves, potentially driving advancements in superresolution imaging and photonic applications beyond the diffraction limit.

关键词： Evanescent waves Light-matter interaction Photonics finite-difference time-domain method Maxwell's equations

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Toward nanophotonic optical isolation via inverse design of energy transfer in nonreciprocal media

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Physical Review A 2024年第4期109卷 043533-043533页

作者： Claire M. Cisowski Madeline C. Waller Robert Bennett School of Physics and Astronomy University of Glasgow G12 8QQ Glasgow Scotland United Kingdom

In this paper we generalize the adjoint method of inverse design to nonreciprocal media. As a test case, we use three-dimensional topology optimization via the level-set method to optimize one-way energy transfer for pointlike source and observation points. To achieve this we introduce a suite of tools, chiefly what we term the “Faraday-adjoint” method which allows for efficient shape optimization in the presence of magneto-optical media. We carry out an optimization based on a very general equation that we derive for energy transfer in a nonreciprocal medium, and link finite-different time-domain numerics to analytics via a modified Born series generalized to a tensor permittivity. This paper represents a stepping stone towards practical nanophotonic optical isolation, often regarded as the “holy grail” of integrated photonics.

关键词： Integrated optics Non-reciprocal propagation Non-reciprocal transmission Optimization problems finite-difference time-domain method

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Experimental and numerical optimization modelling to reduce radiofrequency-induced risks of magnetic resonance examinations on leaded implants

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APPLIED MATHEMATICAL MODELLING 2021年 96卷 177-188页

作者： Corcoles, Juan Yao, Aiping Kuster, Niels Univ Autonoma Madrid Dept Elect & Commun Technol Escuela Politecn Super C Fco Tomas & Valiente 11 Madrid 28049 Spain Lanzhou Univ Sch Informat Sci & Engn 222 Tianshui South Rd Lanzhou Peoples R China Fdn Res Informat Technol Soc ITIS Zeughausstr 43 CH-8004 Zurich Switzerland Swiss Fed Inst Technol Dept Informat Technol & Elect Engn Raemistr 101 CH-8092 Zurich Switzerland

Convex formulations can be used to reduce the local specific absorption rate enhancement by active medical implants of radiofrequency fields in magnetic resonance examinations while minimizing the loss of image quality. This paper demonstrates that such an optimization methodology, previously presented for strictly computational models, can be extended to a hybrid scheme using experimentally determined implant models and pre computed fields, which can enable quasi real-time exposure optimization. The methodology determines the optimum radiofrequency field shimming condition by considering both the reduction of specific absorption rate enhancement at the tip of the implant lead, created by the interaction of the radiofrequency fields tangential to the implant trajectory with the characteristic response of the implant, and the preservation of magnetic field homogeneity, which correlates to image quality. The inputs to this workflow are those required for each implant by standard ISO 10974 evaluation, namely the validated piece wise transfer function of the implant, the clinical routing within the patient, and the pre-computed numerical estimation of patient exposure without the implant. Optimized incident field conditions were computed to meet a range of numerical targets for specific absorption rate reduction, stepping down percentagewise from the maximum field homogeneity to the minimum exposure enhancement, for a generic implant with a flexible wire in a standard benchtop radiofrequency coil and phantom. Measurements of the corresponding specific absorption rate enhancements validated the predictions from the optimization approach within the combined confidence interval. (c) 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license ( http://***/licenses/by-nc-nd/4.0/ )

关键词： Electromagnetic fields Electromagnetic medical applications Radiofrequency Radiofrequency-induced heating Numerical optimization finite-difference time-domain method

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Design of sandwich-type waveguide grating antenna with ultra-long transmission distance and high directionality

OPTICS CONTINUUM

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OPTICS CONTINUUM 2025年第4期4卷 879-887页

作者： Su, Hang Zhang, Bo Zhao, Yuanming Zhang, Fuling Zhang, Pengfei Feng, Zhihua Dong, Guangyan Harbin Inst Technol Sch Astronaut Harbin 150001 Heilongjiang Peoples R China Changchun Univ Sci & Technol Sch Optoelect Engn Changchun 130022 Jilin Peoples R China China Elect Technol Grp Corp Res Inst 27 Zhengzhou 450047 Henan Peoples R China

In order to make the silicon-based optical phased array(SOPA) have a small divergence angle and high directionality, and achieve high-resolution scanning, this paper proposes a sandwich-type waveguide grating antenna (SWGA) based on the Si-Si3N4-Si3N4 platform, which can achieve an effective transmission distance of 1.22cm and finally obtain a divergence angle of 0.0065 degrees. And it has a high upward directionality of 87.41%. Thanks to its large critical dimension, the proposed structure is suitable for manufacturing in complementary metal oxide semiconductor (CMOS) foundries with deep ultraviolet (DUV) lithography. (c) 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： finite-difference time-domain method Free space optics Grating coupler Phased arrays Waveguide design Waveguide gratings

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Assessment and extension of rapid design tools for modeling photonic crystal surface-emitting lasers

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2025年第5期42卷 1123-1130页

作者： Lang, Ben Sewell, Phillip D. Vukovic, Ana Boylan, Karl Rihani, Samir Moodie, David Spalding, Richard Hattasan, Nannicha Berry, Graham Univ Nottingham George Green Inst Electromagnet Res Fac Engn Nottingham England Huawei Technol Res & Dev Ipswich England

Rapid design tools are invaluable for the fast exploration of design space and optimization of photonic crystal surface-emitting lasers (PCSELs). This paper introduces an improved extension to the fast effective index type approach and compares it against a large number of numerical methods for simulating PCSELs. These methods include two varieties of the effective-index method, coupled mode theory, guided mode expansion, rigorous coupled wave analysis, and an iterated method we derive here. All are compared to one another and against results obtained using a 3D time domain solver and where possible, experimental measurements. We conclude that coupled mode theory, along with the iterated method presented here, are the best approximate methods for 2D modeling of PCSEL devices.

关键词： Bragg reflectors Coupled mode theory finite-difference time-domain method Photonic crystals Planar waveguides Rigorous coupled wave analysis

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