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Magnonic bandgap openings and in-gap propagating states in domain-wall waveguides induced by periodic modulations

Physical Review B 2024年第18期109卷 184401-184401页

作者： Qiyun Yi Zhenhua Tang Daoyun Zhu Xiangjun Xing Wei Zhang Yan Zhou School of Physics and Optoelectronic Engineering Guangdong University of Technology Guangzhou 510006 China Guangdong Provincial Key Laboratory of Information Photonics Technology Guangdong University of Technology Guangzhou 510006 China Experimental Teaching Department Guangdong University of Technology Guangzhou 510006 China School of Science and Engineering The Chinese University of Hong Kong Shenzhen Guangdong 518172 China

Magnonic waveguides based on magnetic domain walls surpass conventional magnonic waveguides, which typically feature single magnetic domains, in nearly all critical aspects. Consequently, they are considered pivotal for the development of future nanomagnonic circuits. A distinctive feature of these waveguides is the complete absence of a bandgap, known as the vanishing magnon barrier. This feature is of great theoretical importance and has practical relevance for several applications, but it has received limited attention thus far. In our research, we employ micromagnetic simulations to investigate the spin-wave propagation in a domain-wall based magnonic waveguide, which includes reconfigurable periodic modulations. The magnonic band structure within the domain-wall waveguide can be significantly altered based on the magnetization configuration of the modulating magnets, resulting in the creation of bandgaps or leaving the structure unchanged, as though no modulation were applied. The bandgaps arise from the Bragg reflection of spin waves due to an induced periodic potential. A resonance-enhanced propagation state of the waveguide and modulation magnets, indicative of mode matching, results in the emergence of an allowed band within each bandgap under specific conditions. This study may open an effective route to control the band structure of domain-wall waveguides.

关键词： domain walls Micromagnetism Spin waves Multilayer thin films Nanowires finite-difference time-domain method Landau-Lifschitz-Gilbert equation Micromagnetic modeling

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Completion of model validation experiments at the Princeton starshade testbed

Completion of model validation experiments at the Princeton ...

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Conference on Space Telescopes and Instrumentation - Optical, Infrared, and Millimeter Wave

作者： Shaklan, Stuart Harness, Anthony Kasdin, N. Jeremy Galvin, Michael Balasubramanian, K. White, Victor Yee, Karl Muller, Richard Willems, Phillip Dumont, Philip Vuong, Simon Lisman, Doug CALTECH Jet Prop Lab 4800 Oak Grove Dr Pasadena CA 91109 USA Princeton Univ Dept Mech & Aerosp Engn Princeton NJ 08544 USA

ISBN: (纸本)9781510653429

Following the results of Starshade Milestone 1 in which we demonstrated broadband contrast better than 10-10, we have performed model validation experiments to show that diffraction models accurately predict the contrast due to perturbations representing the building blocks of the instrument error budget. The perturbations include the displacement of petal edge segments, sinusoidal petal edge shape deformations, global petal position errors, and random petal radial placement errors. We also show that the model accurately predicts the combined effects of two errors. The experiments result in a measured Model Uncertainty Factor (MUF) that is then applied to the starshade instrument contrast error budget.

关键词： Diffraction Data modeling Photomasks Polarization Telescopes Manufacturing Etching Error analysis finite-difference time-domain method Optical instrument design

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Submillimeter-Wave Multiphase Oscillation Using Traveling Pulses in a Resonant-Tunneling Diode-Oscillator Lattice

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JOURNAL OF INFRARED MILLIMETER AND TERAHERTZ WAVES 2021年第4期42卷 426-445页

作者： Sawai, Shinya Narahara, Koichi Kanagawa Inst Technol Dept Elect & Elect Engn 1030 Shimoogino Atsugi Kanagawa 2430292 Japan

We recently proposed a multiphase oscillator utilizing a periodic pulse train generated and propagated in a closed one-dimensional lattice of resonant-tunneling diode (RTD) oscillators, each of which establishes the neighbor-to-neighbor coupling through lossy inductors. In this work, we develop the design criteria for the bias dependence of oscillation frequency through the bifurcation analysis based on the quasi-continuous model of the lattice. We then model the lattice in the full-wave scheme using the finite-difference time-domain method and validate the multiphase oscillation in submillimeter-wave frequencies. Finally, several experimental observations conducted in MHz frequencies using tunnel diodes in place of RTDs are presented to validate several synchronization properties of the pulse train in the lattice including the direction-specified transmission of pulse train and its application to the multiphase oscillator.

关键词： Resonant-tunneling diodes finite-difference time-domain method Bifurcation Multiphase oscillation Voltage-controlled oscillation Self-injection locking

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An alternative amelioration of ME-based DZT-PML for truncating FDTD problems

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ELECTROMAGNETICS 2021年第2期41卷 83-97页

作者： Feng, Naixing Li, Xue-Shi Zhang, Yuxian Sun, Yanming Shenzhen Univ Inst Microscale Optoelect Shenzhen Peoples R China Guangdong Univ Technol Sch Automat Guangzhou 510006 Peoples R China

In order to further alleviate computational burdens and enhance accuracies, we propose an efficient amelioration on the complex-frequency-shifted perfectly matched layer (CFS- PML) via introducing both direct Z-transform (DZT) and matrix exponential (ME) methods for terminating the finite-difference time-domain (FDTD) region. The method is here referred as the DZT-ME-PML. Due to introducing the DZT method, the proposal can avoid the disadvantages of approximate bilinear and matched Z-transform in modeling fine and course structures, leading to achieving higher accuracies. Moreover, by employing the ME technique, the proposal develops into the compact first-order differential matrix form applied to evading the convolution manipulations, the variable replacements, and the formulation rearrangements during the mathematical derivations. Besides, the proposed DZT-ME-PML can not only flexibly terminate the arbitrary media when adding the DB constitutive relation, but efficiently attenuate evanescent waves, and reduce the late-time reflections due to the CFS scheme. Three-dimensional (3D) numerical examples have been carried out to illustrate the validity and accuracy of the proposed DZT-ME-PML. Eventually, applied to solving geophysical problem with the very low frequency (VLF) case, the DZT-ME-PML shows stronger absorption accuracy than the general ME-PML method.

关键词： Complex-frequency-shifted perfectly matched layer direct Z-transform finite-difference time-domain method matrix exponential very low frequency

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A three-point compact LOD-FDTD method for solving the 2D scalar wave equation

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MICROWAVE AND OPTICAL TECHNOLOGY LETTERS 2024年第5期66卷

作者： Pereda, Jose A. Grande, Ana Univ Cantabria Dept Ingn Comunicac Santander Cantabria Spain Univ Valladolid Dept Electr & Elect Valladolid Castilla y Leon Spain

This letter introduces an unconditionally stable finite-difference time-domain (FDTD) method, based on the locally one-dimensional (LOD) technique, for the solution of the two-dimensional scalar wave equation (WE) in homogeneous media. The second spatial derivatives in the WE are discretized by using a three-point compact (implicit) finite-difference formula with a free parameter. This formula has second-order accuracy and becomes fourth-order by properly selecting the parameter value. Moreover, the resulting algorithm only involves tridiagonal matrices, as when using standard (explicit) second-order finite differences. Additionally, a stability analysis is performed and the numerical dispersion relation of the method is derived. The proposed compact LOD-WE-FDTD technique has been applied to the calculation of resonant frequencies in a metallic ridge cavity. The accuracy of the results obtained has been studied as a function of the parameter value.

关键词： compact finite differences finite-difference time-domain method locally one-dimensional numerical dispersion stability wave equation

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Rotationally displaced electric field intensity distribution around square nanoantennas induced by circularly polarized light

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Physical Review B 2024年第3期109卷 035428-035428页

作者： Naoki Ichiji Takuya Ishida Ikki Morichika Tetsu Tatsuma Satoshi Ashihara Institute of Industrial Science The University of Tokyo 4-6-1 Komaba Meguro-Ku Tokyo 153-8505 Japan

An optical field around regular polygon metal nanostructures excited by circularly polarized light can exhibit rotationally displaced intensity distributions. Although this phenomenon has been recognized, its underlying mechanisms have not been sufficiently explained. Herein, finite-difference time-domain simulations and model analyses reveal that the rotationally displaced optical intensity distribution can be generated when each of the linear polarization components that constitute circular polarization excites a superposition of multiple modes. The proposed model reasonably explains the rotationally displaced patterns for a square nanoantenna and other regular-polygon nanoantennas.

关键词： Electric polarization Nano-oscillators Plasmons finite-difference time-domain method

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Light-matter interaction at rough surfaces: A morphological perspective on laser-induced periodic surface structures

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Physical Review B 2024年第11期110卷 115438页

作者： Vladimir Yu. Fedorov Jean-Philippe Colombier Université Jean Monnet Saint-Etienne CNRS IOGS Laboratoire Hubert Curien UMR 5516 Saint-Etienne F-42023 France

We use ab initio electromagnetic simulations to investigate light absorption by rough surfaces in the context of the formation of laser-induced periodic surface structures. Our approach involves modeling a rough surface using a statistical description of its continuous height distribution via a corresponding correlation function. We study the influence of incident light polarization and various statistical properties of surface roughness, such as root-mean-square height and correlation length, on the distribution of absorbed laser energy. By analyzing light absorption in different layers of the surface selvedge, we elucidate how different features of surface morphology influence the shape of the resulting periodic surface structures. We show that circularly polarized laser pulses are highly sensitive to initial or progressively developing asymmetries in surface roughness.

关键词： Light-matter interaction Optical interactions with surfaces Roughness Ultrafast phenomena finite-difference time-domain method Maxwell's equations

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Nano-diffractive elements in BSI Pixel CMOS Image Sensors: Optical Design and Process Integration co-optimization with pixel Scaling 26

Nano-diffractive elements in BSI Pixel CMOS Image Sensors: O...

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Conference on Integrated Optics - Devices, Materials, and Technologies XXVI at SPIE OPTO Conference

作者： Barlas, M. Crocherie, A. Bardonnet, F. Abadie, Q. Sungauer, E. Vignetti, M. Mamdy, B. Nicholson, I D'Aillon, P. G. Bianchi, A. R. Mugny, G. Golanski, D. Domengie, F. Besson, P. Prevost, E. Parmigianni, L. Arnaud, J. Wehbe-Alause, H. Tournier, A. Noblanc, O. Rochereau, K. STMicroelectronics 850 Rue Jean Monnet F-38920 Crolles France CEA Leti 17 Ave Martyrs F-38054 Grenoble France

ISBN: (纸本)9781510648807;9781510648791

Next-generation BSI CMOS Imager Sensors are strongly driven by novel applications in depth sensing, mainly operating in the NIR (940nm) spectrum. As a result, the need for higher pixel sensitivity while shrinking pixel pitch is more present than ever. In this work, we present a new technology platform based on ad-hoc nano diffractor geometries, integrated in the Back Side of BSI CIS that allow to drastically improve the QE of the sensor for pitches varying from 10 mu m down to 2.2 mu m, co-optimized for both optical and electronic pixel performance

关键词： Quantum efficiency Silicon Photodiodes finite-difference time-domain method Optical design Near infrared Image sensors Infrared sensors Optoelectronics integration Very large scale integration

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Localized surface plasmons in disk supershape shell nanoparticles

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Journal of the Optical Society of America B 2025年第6期42卷 1366-1376页

作者： Parivash Hashemi Emadoddin Yaghooti Ferydon Babaei Department of Physics University of Qom Qom Iran

Here, we reported the excitation of multiple localized surface plasmons in disk supershape shell nanoparticles using the finite difference time domain method. All plasmon bands of disk supershape shell nanoparticles were extracted from extinction spectra. The characteristics of the plasmon bands were investigated as functions of the structural parameters of the shell nanoparticles and the refractive indices of the environment and substrate. The obtained results showed in general, two types of plasmon bands appear, one at longer wavelengths and the other at shorter wavelengths, which are, respectively, dependent on the excitation of dipoles and higher-order multipoles. The patterns of the electric field and charge distribution prove these points. The Purcell factor spectra revealed that the resonant modes corresponding to plasmonic bands occur in the emission spectra, although new modes appear between them due to the asymmetry of the nanoparticle geometry. This study could potentially have applications in sensors, thermal photonics, and energy harvesting.

关键词： finite-difference time-domain method Localized surface plasmon resonance Localized surface plasmons Metal nanoparticles Resonant modes Solar cell efficiency

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On the representation of reinforced concrete structures in FDTD-based simulations to compute lightning-induced magnetic fields

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ELECTRIC POWER SYSTEMS RESEARCH 2024年 230卷

作者： Naranjo-Villamil, Susana Guiffaut, Christophe Gazave, Julien Piedallu, Eric Reineix, Alain Marquois, Boris EDF Grp EDF Power Networks Lab Ave Renardieres F-77250 Moret Loing Et Orvanne Ile De France France XLIM Res Inst CEM & Diffract 123 Ave Albert Thomas F-87000 Limoges Haute Vienne France EDF Grp EDF DIPNN DITEGG 905 Ave Camp Menthe F-13090 Aix En Provence Provence Alpes France

Reinforced concrete structures are generally well protected against the adverse effects of a direct lightning strike. Nevertheless, when it occurs, the electromagnetic field generated by the lighting current flowing through their reinforcement can cause a malfunction of sensitive electronic devices. The electromagnetic field can be estimated using full-wave methods, although the accuracy of the estimation depends on the representatives of the model, which is why experimental validation is essential. This paper presents the numerical model of a reinforced concrete structure where a transient current was injected to emulate a direct lightning strike. Full-wave simulations are conducted using TEMSI-FD and the results are compared to the measurements made at the testing facility of EDF TEGG. The simulation results were in good agreement with the measurements, especially when the soil was used as the return path for the current.

关键词： Lightning Magnetic field Reinforced concrete Measurements finite-difference time-domain method

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