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Phase-resolving spin-wave microscopy using infrared strobe light

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arXiv 2024年

作者： Xiong, Yuzan Christy, Andrew Mahdi, Muntasir Sun, Rui Li, Yi Geil, Robert D. Cahoon, James F. Tsui, Frank Yang, Binbin Kim, Tae Hee Hu, Jia-Mian Sun, Dali Hamilton, Michael C. Novosad, Valentine Zhang, Wei Department of Physics and Astronomy University of North Carolina at Chapel Hill Chapel HillNC27599 United States Department of Chemistry University of North Carolina at Chapel Hill Chapel HillNC27599 United States Department of Electrical and Computer Engineering Auburn University AuburnAL36849 United States North Carolina State University RaleighNC27695 United States Materials Science Division Argonne National Laboratory ArgonneIL60439 United States Department of Electrical and Computer Engineering North Carolina A&T State University GreensboroNC27411 United States Department of Physics Ewha Womans University Seodaemun Seoul Korea Republic of Department of Materials Science and Engineering University of Wisconsin-Madison MadisonWI53706 United States

The needs for sensitively and reliably probing magnetization dynamics have been increasing in various contexts such as studying novel hybrid magnonic systems, in which the spin dynamics strongly and coherently couple to other excitations, including microwave photons, light photons, or phonons. Recent advances in quantum magnonics also highlight the need for employing magnon phase as quantum state variables, which is to be detected and mapped out with high precision in on-chip micro- and nano-scale magnonic devices. Here, we demonstrate a facile optical technique that can directly perform concurrent spectroscopic and imaging functionalities with spatial- and phase-resolutions, using infrared strobe light operating at 1550-nm wavelength. To showcase the methodology, we spectroscopically studied the phase-resolved spin dynamics in a bilayer of Permalloy and Y3Fe5O12 (YIG), and spatially imaged the backward volume spin wave modes of YIG in the dipolar spin wave regime. Using the strobe light probe, the detected precessional phase contrast can be directly used to construct the map of the spin wave wavefront, in the continuous-wave regime of spin-wave propagation and in the stationary state, without needing any optical reference path. By selecting the applied field, frequency, and detection phase, the spin wave images can be made sensitive to the precession amplitude and phase. Our results demonstrate that infrared optical strobe light can serve as a versatile platform for magneto-optical probing of magnetization dynamics, with potential implications in investigating hybrid magnonic systems. Copyright © 2024, The Authors. All rights reserved.

关键词： Spin waves

STC-IDS: Spatial-Temporal Correlation Feature Analyzing based Intrusion Detection System for Intelligent Connected Vehicles

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arXiv 2022年

作者： Cheng, Pengzhou Han, Mu Li, Aoxue Zhang, Fengwei The Department of Electronic Information and Electrical Engineering Shanghai Jiao Tong University Shanghai201100 China The School of Computer Science and Communication Engineering Jiangsu Key Laboratory of Security Technology for Industrial Cyberspace Jiangsu University Zhenjiang212013 China The School of Automotive and Traffic Engineering Jiangsu University Zhenjiang212013 China The Department of Computer Science and Engineering Southern University of Science and Technology Shenzhen518000 China

Intrusion detection is an important defensive measure for automotive communications security. Accurate frame detection models assist vehicles to avoid malicious attacks. Uncertainty and diversity regarding attack methods make this task challenging. However, the existing works have the limitation of only considering local features or the weak feature mapping of multi-features. To address these limitations, we present a novel model for automotive intrusion detection by spatial-temporal correlation features of in-vehicle communication traffic (STC-IDS). Specifically, the proposed model exploits an encoding-detection architecture. In the encoder part, spatial and temporal relations are encoded simultaneously. To strengthen the relationship between features, the attention-based convolutional network still captures spatial and channel features to increase the receptive field, while attention-LSTM builds meaningful relationships from previous time series or crucial bytes. The encoded information is then passed to detector for generating forceful spatial-temporal attention features and enabling anomaly classification. In particular, single-frame and multi-frame models are constructed to present different advantages respectively. Under automatic hyper-parameter selection based on Bayesian optimization, the model is trained to attain the best performance. Extensive empirical studies based on a real-world vehicle attack dataset demonstrate that STC-IDS has outperformed baseline methods and obtains fewer false-alarm rates while maintaining efficiency. © 2022, CC BY.

关键词： Intrusion detection

High-efficiency optical frequency mixing in an all-dielectric metasurface enabled by multiple bound states in the continuum

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Physical Review B 2023年第7期107卷 075441-075441页

作者： Tingting Liu Meibao Qin Feng Wu Shuyuan Xiao Institute of Photonic Chips University of Shanghai for Science and Technology Shanghai 200093 China Centre for Artificial-Intelligence Nanophotonics School of Optical-Electrical and Computer Engineering University of Shanghai for Science and Technology Shanghai 200093 China School of Physics and Materials Science Nanchang University Nanchang 330031 China School of Optoelectronic Engineering Guangdong Polytechnic Normal University Guangzhou 510665 China Institute for Advanced Study Nanchang University Nanchang 330031 China Jiangxi Key Laboratory for Microscale Interdisciplinary Study Nanchang University Nanchang 330031 China

We present nonlinear optical four-wave mixing in a silicon nanodisk dimer metasurface. Under the oblique incident plane waves, the designed metasurface exhibits a multiresonant feature with simultaneous excitations of three quasi-bound states in the continuum (BIC). Through employing these quasi-BICs with maximizing electric field energy at the input bump wavelengths, significant enhancement of third-order nonlinear processes including third-harmonic generation, degenerate and nondegenerate four-wave mixing are demonstrated, giving rise to ten frequencies in the visible wavelengths. This work may lead to a new frontier of ultracompact optical mixer for applications in optical circuitry, ultrasensitive sensing, and quantum nanophotonics.

关键词： Nanophotonics Metasurfaces Finite-element method

Topological photonics: Frontiers in robust light manipulation

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Reviews in Physics 2025年 13卷

作者： Zhang, Yongliang Sha, Wei E.I. Tsukerman, Igor State Key Laboratory of Semiconductor Physics and Chip Technologies Institute of Semiconductors Chinese Academy of Sciences Beijing100083 China College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China Department of Electrical and Computer Engineering The University of Akron AkronOHOH 44325-3904 United States

Unconventional Spin-Orbit Torques from Sputtered MoTe2 Films

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arXiv 2024年

作者： Li, Shuchen Gibbons, Jonathan Chyczewski, Stasiu Liu, Zetai Ni, Hsu-Chih Qian, Jiangchao Zuo, Jian-Min Zheng, Jun-Fei Zhu, Wenjuan Hoffmann, Axel Department of Materials Science and Engineering Materials Research Laboratory University of Illinois Urbana-Champaign UrbanaIL61801 United States Department of Physics University of California La Jolla San DiegoCA92093 United States Department of Electrical and Computer Engineering University of Illinois Urbana-Champaign UrbanaIL61801 United States Entegris Inc. DanburyCT06810 United States

Materials with strong spin-orbit coupling and low crystalline symmetry are promising for generating large unconventional spin-orbit torques (SOTs), such as in-plane field-like (FL) torques and out-of-plane damping-like (DL) torques, which can effectively manipulate and deterministcally switch an out-of-plane magnetization without the need for additional external in-plane magnetic fields. Here, we report SOTs generated by magnetron-sputtered 1T′ MoTe2/Permalloy (Py;Ni80Fe20)/MgO heterostructures using both spin-torque ferromagnetic resonance (ST-FMR) and second harmonic Hall measurements. We observed unconventional FL and DL torques in our samples due to spins polarized normal to the interface of MoTe2 and Py layers, and studied the influence of crystallographic order and MoTe2 layer thickness on the SOTs. By comparing the Raman spectra of 1T′ MoTe2 samples prepared in different ways, we found a tensile strain in sputtered MoTe2 films, which might further enhance the generation of unconventional torques by reducing the symmetry of 1T′ MoTe2. Copyright © 2024, The Authors. All rights reserved.

关键词： Torque

Post-storm vehicle routing for distribution grid restoration: An OLUCT based learning approach

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Post-storm vehicle routing for distribution grid restoration...

2020 IEEE Power and Energy Society General Meeting, PESGM 2020

作者： Shuai, Hang He, Haibo Wen, Jinyu University of Rhode Island Department of Electrical Computer and Biomedical Engineering KingstonRI02881 United States Huazhong University of Science and Technology State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Wuhan China

ISBN: (纸本)9781728155081

Natural disasters such as storms usually bring significant damages to distribution grids. Many distribution grids are not equipped with sensors that can pinpoint the location of actual faults. This further complicated the outage restoration process in distribution grids. This paper focuses on the optimal routing of repair vehicles to restore outages in the grid as fast as possible after a storm. First, the vehicle routing problem is formulated as a sequential stochastic optimization problem. In the optimization model, the belief state of the power grid is updated according to the phone calls from customers and the information collected by the repair vehicles. Second, an Open Loop Upper Confidence Bound for Trees (OLUCT) algorithm based stochastic lookahead policy is utilized to achieve the realtime dispatching of the repair vehicles. Simulation results show that the proposed approach can effectively navigate the vehicle to repair all outages. © 2020 IEEE.

关键词： Optimization

Thermalization of Interacting Quasi-One-Dimensional Systems

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Physical Review Letters 2023年第3期130卷 030401-030401页

作者： Miłosz Panfil Sarang Gopalakrishnan Robert M. Konik Faculty of Physics University of Warsaw ul. Pasteura 5 02-093 Warsaw Poland Department of Physics The Pennsylvania State University University Park Pennsylvania 16802 USA Department of Electrical and Computer Engineering Princeton University Princeton New Jersey 08544 USA Condensed Matter Physics and Materials Science Division Brookhaven National Laboratory Upton New York 11973 USA

Many experimentally relevant systems are quasi-one-dimensional, consisting of nearly decoupled chains. In these systems, there is a natural separation of scales between the strong intrachain interactions and the weak interchain coupling. When the intrachain interactions are integrable, weak interchain couplings play a crucial part in thermalizing the system. Here, we develop a Boltzmann-equation formalism involving a collision integral that is asymptotically exact for any interacting integrable system, and apply it to develop a quantitative theory of relaxation in coupled Bose gases in the experimentally relevant Newton’s cradle setup. We find that relaxation involves a broad spectrum of timescales. We provide evidence that the Markov process governing relaxation at late times is gapless; thus, the approach to equilibrium is generally nonexponential, even for spatially uniform perturbations.

关键词： Cold atoms & matter waves Nonequilibrium statistical mechanics Bose gases Boltzmann theory

Surface Acoustic Wave Sensor Interrogation Using Goubau Waves

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Surface Acoustic Wave Sensor Interrogation Using Goubau Wave...

Antennas and Propagation Society International Symposium

作者： David W. Greve Jagannath Devkota Paul Ohodnicki Ruishu Wright Department of Electrical and Computer Engineering Carnegie Mellon U. Pittsburgh PA USA ORISE Faculty Fellow National Energy Technology Laboratory Pittsburgh PA National Energy Technology Laboratory Pittsburgh PA USA NETL Support Contractor Pittsburgh PA USA Department of Mechanical Engineering & Materials Science Swanson School of Engineering University of Pittsburgh Pittsburgh PA USA

Electromagnetic waves on single conductors (Goubau waves) are investigated for the interrogation of wireless sensors. A demonstration of interrogation of a surface acoustic wave (SAW) sensor is presented, followed by ...

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Compressed CPD-Based Channel Estimation and Joint Beamforming for RIS-Assisted Millimeter Wave Communications

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arXiv 2022年

作者： Zheng, Xi Fang, Jun Wang, Hongwei Wang, Peilan Li, Hongbin The National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of China Chengdu611731 China The Department of Electrical and Computer Engineering Stevens Institute of Technology HobokenNJ07030 United States

We consider the problem of channel estimation and joint active and passive beamforming for reconfigurable intelligent surface (RIS) assisted millimeter wave (mmWave) multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. We show that, with a well-designed frame-based training protocol, the received pilot signal can be organized into a low-rank third-order tensor that admits a canonical polyadic decomposition (CPD). Based on this observation, we propose two CPD-based methods for estimating the cascade channels associated with different subcarriers. The proposed methods exploit the intrinsic low-rankness of the CPD formulation, which is a result of the sparse scattering characteristics of mmWave channels, and thus have the potential to achieve a significant training overhead reduction. Specifically, our analysis shows that the proposed methods have a sample complexity that scales quadratically with the sparsity of the cascade channel. Also, by utilizing the singular value decomposition-like structure of the effective channel, this paper develops a joint active and passive beamforming method based on the estimated cascade channels. Simulation results show that the proposed CPD-based channel estimation methods attain mean square errors that are close to the Cramér-Rao bound (CRB) and present a clear advantage over the compressed sensing-based method. In addition, the proposed joint beamforming method can effectively utilize the estimated channel parameters to achieve superior beamforming performance. Copyright © 2022, The Authors. All rights reserved.

关键词： Channel estimation