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Broadband delay lines and nonreciprocal resonances in unidirectional waveguides

Physical Review B 2019年第2期100卷 020303(R)-020303(R)页

作者： Sander A. Mann Dimitrios L. Sounas Andrea Alù Photonics Initiative Advanced Science Research Center City University of New York New York 10031 USA Department of Electrical and Computer Engineering The University of Texas at Austin Austin Texas 78712 USA Department of Electrical and Computer Engineering Wayne State University Detroit Michigan 48202 USA Physics Program Graduate Center City University of New York New York 10016 USA Department of Electrical Engineering City College of The City University of New York New York 10031 USA

Slow-light waveguides play an important role in optical pulse delay lines, but are practically limited by disorder-induced attenuation. Topological edge states, unidirectional and robust against disorder, have been proposed as a way to address this issue. Here, we study the transmission phase and pulse propagation dynamics through unidirectional systems in the presence of strong discontinuities. We first investigate a magnetically biased slow-light channel, demonstrating broadband pulse delays in small footprints. We uncover a nonreciprocal etalonlike resonance, sustained by propagating forward and evanescent backward modes, affecting pulse propagation and delay. We then show the existence of these features in topologically protected edge states, highlighting their universality. These exotic resonances provide a new degree of freedom in unidirectional waveguides to engineer their response, and they may therefore prove highly useful in various nanophotonic applications.

关键词： Plasmonics Topological effects in photonic systems Topological insulators Topological materials Waveguides Lorentz symmetry

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Optomechanically Induced Birefringence and Optomechanically Induced Faraday Effect

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Physical Review Letters 2019年第2期123卷 023602-023602页

作者： Robert Duggan Javier del Pino Ewold Verhagen Andrea Alù Department of Electrical and Computer Engineering The University of Texas at Austin Austin Texas 78712 USA Center for Nanophotonics AMOLF Science Park 104 1098 XG Amsterdam The Netherlands Photonics Initiative Advanced Science Research Center City University of New York New York 10031 USA Physics Program Graduate Center City University of New York New York 10016 USA Department of Electrical Engineering City College of The City University of New York New York 10031 USA

We demonstrate an optomechanical platform where optical mode conversion mediated by mechanical motion enables the arbitrary tailoring of polarization states of propagating light fields. Optomechanical interactions are realized in a Fabry-Pérot resonator, which naturally supports two polarization-degenerate states while an optical control field induces rotational symmetry breaking. Applying such principles, the entire Poincaré sphere is spanned by just optical control of the driving field, realizing reciprocal and nonreciprocal optomechanically induced birefringence for linearly polarized and circularly polarized control driving. A straightforward extension of this setup also enables all-optical tunable isolation and circulation. Our findings open new avenues to exploit optomechanics for the arbitrary manipulation of light polarization.

关键词： Nonlinear optics Optomechanics

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Atomic-Scale Defect Detection by Nonlinear Light Scattering and Localization

arXiv

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arXiv 2020年

作者： Shafiei, Farbod Orzali, Tommaso Vert, Alexey Miri, Mohammad-Ali Hung, P.Y. Wong, Man Hoi Alù, Andrea Bersuker, Gennadi Downer, Michael C. Department of Physics University of Texas at Austin AustinTX United States SEMATECH AlbanyNY United States Sunny Polytechnic Institute AlbanyNY United States Department of Electrical and Computer Engineering University of Texas at Austin AustinTX United States Department of Physics Queens College of the CUNY QueensNY United States Photonics Initiative Advanced Science Research Center CUNY New YorkNY United States Physics Program Graduate Center CUNY New YorkNY United States Aerospace Corporation Los AngelesCA United States

Hetero-epitaxial crystalline films underlie many electronic and optical technologies but are prone to forming defects at their hetero-interfaces. Atomic-scale defects such as threading dislocations that propagate into a film impede the flow of charge carriers and light degrading electrical/optical performance of devices. Diagnosis of sub-surface defects traditionally requires time-consuming invasive techniques such as cross–sectional transmission electron microscopy. Using III-V films grown on Si, we have demonstrated noninvasive, bench-top diagnosis of sub-surface defects by optical second-harmonic scanning probe microscope. We observed a high-contrast pattern of sub-wavelength "hot spots" caused by scattering and localization of fundamental light by defect scattering sites. Size of these observed hotspots are strongly correlated to the density of dislocation defects. Our results not only demonstrate a global and versatile method for diagnosing sub-surface scattering sites but uniquely elucidate optical properties of disordered media. An extension to third harmonics would enable irregularities detection in non-χ(2) materials making the technique universally applicable. Copyright © 2020, The Authors. All rights reserved.

关键词： High resolution transmission electron microscopy

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The application of an extracellular vesicle-based biosensor in early diagnosis and prediction of chemoresponsiveness in ovarian cancer

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Cancer Letters 2024年 581卷 216533-216533页

作者： Tsang, Benjamin K. Asare-Werehene, Meshach Hunter, Rob Gerber, Emma Reunov, Arkadiy Brine, Isaiah Chang, Chia-Yu Chang, Chia-Ching Shieh, Dar-Bin Burger, Dylan Anis, Hanan Departments of Obstetrics & Gynecology and Cellular & Molecular Medicine Centre for Infection Immunity and Inflammation Interdisciplinary School of Health Sciences University of Ottawa Ottawa ON K1N 6N5 Canada Chronic Disease Program Ottawa Hospital Research Institute The Ottawa Hospital Ottawa ON K1Y 4E9 Canada Department of Biology St. Francis Xavier University 2320 Notre Dame Avenue Antigonish NS B2G 2W5 Canada School of Electrical Engineering and Computer Science Ottawa-Carleton Institute for Biomedical Engineering University of Ottawa Ottawa ON K1N 6N5 Canada Department of Biological Science and Department of Electrophysics Technology Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B) National Yang Ming Chiao Tung University Hsinchu 30068 Taiwan Institute of Basic Medical Science Institute of Oral Medicine and Department of Stomatology Advanced Optoelectronic Technology Center and Center for Micro/Nano Science and Technology National Cheng Kung University Hospital National Cheng Kung University Tainan 704 Taiwan Institute of Physics Academia Sinica Taipei 10529 Taiwan

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Nonreciprocal Willis Coupling in Zero-Index Moving Media

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Physical Review Letters 2019年第6期123卷 064301-064301页

作者： Li Quan Dimitrios L. Sounas Andrea Alù Department of Electrical and Computer Engineering The University of Texas at Austin Austin Texas 78712 USA Department of Electrical and Computer Engineering Wayne State University Detroit Michigan 48202 USA Photonics Initiative Advanced Science Research Center City University of New York New York New York 10031 USA Physics Program Graduate Center City University of New York New York New York 10016 USA Department of Electrical Engineering City College of The City University of New York New York 10031 USA

Mechanical motion can break the symmetry in which sound travels in a medium, but significant nonreciprocity is typically achieved only for large motion speeds. We combine moving media with zero-index acoustic propagation, yielding extreme nonreciprocity and induced bianisotropy for modest applied speeds. The metamaterial is formed by an array of waveguides loaded by Helmholtz resonators, and it exhibits opposite signs of the refractive index sustained by asymmetric Willis coupling for propagation in opposite directions. We use this response to induce nonreciprocal positive-to-negative sound refraction, and we propose a nonreciprocal metamaterial lens focusing only with excitation from one side based on asymmetric Willis coupling.

关键词： Acoustic metamaterials Acoustic wave phenomena Acoustics

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scTenifoldXct: A semi-supervised method for predicting cell-cell interactions and mapping cellular communication graphs

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Cell systems 2023年第4期14卷 302-311.e4页

作者： Yongjian Yang Guanxun Li Yan Zhong Qian Xu Yu-Te Lin Cristhian Roman-Vicharra Robert S Chapkin James J Cai Department of Electrical and Computer Engineering Texas A&M University College Station TX 77843 USA. Department of Statistics Texas A&M University College Station TX 77843 USA. Key Laboratory of Advanced Theory and Application in Statistics and Data Science-MOE School of Statistics East China Normal University 3663 North Zhongshan Road Shanghai 200062 China. Department of Veterinary Integrative Biosciences Texas A&M University College Station TX 77843 USA. Graduate Institute of Biomedical Electronics and Bioinformatics National Taiwan University Taipei Taiwan. Department of Nutrition and the Program in Integrative Nutrition & Complex Diseases Texas A&M University College Station TX 77843 USA. Electronic address: r-chapkin@tamu.edu. Department of Electrical and Computer Engineering Texas A&M University College Station TX 77843 USA Department of Veterinary Integrative Biosciences Texas A&M University College Station TX 77843 USA Interdisciplinary Program of Genetics Texas A&M University College Station TX 77843 USA. Electronic address: jcai@tamu.edu.

We present scTenifoldXct, a semi-supervised computational tool for detecting ligand-receptor (LR)-mediated cell-cell interactions and mapping cellular communication graphs. Our method is based on manifold alignment, using LR pairs as inter-data correspondences to embed ligand and receptor genes expressed in interacting cells into a unified latent space. Neural networks are employed to minimize the distance between corresponding genes while preserving the structure of gene regression networks. We apply scTenifoldXct to real datasets for testing and demonstrate that our method detects interactions with high consistency compared with other methods. More importantly, scTenifoldXct uncovers weak but biologically relevant interactions overlooked by other methods. We also demonstrate how scTenifoldXct can be used to compare different samples, such as healthy vs. diseased and wild type vs. knockout, to identify differential interactions, thereby revealing functional implications associated with changes in cellular communication status.

关键词： cell-cell interaction cellular communication gene regression network machine learning manifold alignment neural networks scRNA-seq single-cell RNA sequencing

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General-to-detailed GAN for infrequent class medical images

arXiv

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arXiv 2018年

作者： Koga, Tatsuki Sakuma, Jun Nonaka, Naoki Seita, Jun Medical Sciences Innovation Hub Program RIKEN Center for Advanced Intelligence Project RIKEN Medical Sciences Innovation Hub Program RIKEN Center for Advanced Intelligence Project RIKEN Department of Computer Science University of Tsukuba Medical Sciences Innovation Hub Program RIKEN

Deep learning has significant potential for medical imaging. However, since the incident rate of each disease varies widely, the frequency of classes in a medical image dataset is imbalanced, leading to poor accuracy for such infrequent classes. One possible solution is data augmentation of infrequent classes using synthesized images created by Generative Adversarial Networks (GANs), but conventional GANs also require certain amount of images to learn. To overcome this limitation, here we propose General-to-detailed GAN (GDGAN), serially connected two GANs, one for general labels and the other for detailed labels. GDGAN produced diverse medical images, and the network trained with an augmented dataset outperformed other networks using existing methods with respect to Area-Under-Curve (AUC) of Receiver Operating Characteristic (ROC) curve. Copyright © 2018, The Authors. All rights reserved.

关键词： Generative adversarial networks

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Nonreciprocal hyperbolic propagation over moving metasurfaces

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Physical Review B 2019年第4期99卷 045407-045407页

作者： Yarden Mazor Andrea Alù Department of Electrical and Computer Engineering The University of Texas at Austin Austin Texas 78712 USA Photonics Initiative Advanced Science Research Center City University of New York New York New York 10031 USA Physics Program Graduate Center City University of New York New York New York 10026 USA Department of Electrical Engineering City College of New York New York New York 10031 USA

Hyperbolic propagation offers exciting opportunities in nanophotonics, from subdiffraction imaging to enhanced local density of states. This transport regime is typically induced by strong modulation of conductivity, i.e., with alternating metallic and dielectric material properties. Here, we analyze a moving impedance surface, showing that suitably tailored homogeneous metasurfaces can support one-way hyperbolic propagation when in motion, adding nonreciprocity to hyperbolic propagation phenomena, and without suffering from nonlocal effects stemming from discretization or finite granularity of the surface.

关键词： Electromagnetism Metamaterials Photonics

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Angular-momentum selectivity and asymmetry in highly confined wave propagation along sheath-helical metasurface tubes

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Physical Review B 2019年第15期99卷 155425-155425页

Highly confined surface waves present unique opportunities to enhance light interactions with localized emitters or molecules. Hyperbolic dispersion in metasurfaces allows us to tailor and manipulate surface waves, enhancing the local density of states over broad bandwidths. So far, propagation on this platform was mainly studied in planar geometries, which facilitates the analysis but somehow limits the realm of possibilities. Here we show that “wrapping” hyperbolic metasurfaces into tubes may greatly enrich the wave propagation dynamics along their axis. This system shows strong interaction with fields and sources carrying optical angular momentum and pronounced field asymmetries, and opens pathways to valley-specific excitation and routing. In addition, we demonstrate that various parameter regimes enable strong spin/helicity momentum locking.

关键词： Angular momentum of light Hyperbolic metamaterials Light-matter interaction Surface plasmons Surfaces

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Passive Acoustic Metasurface with Unitary Reflection Based on Nonlocality

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Physical Review Applied 2019年第5期11卷 054077-054077页

作者： Li Quan Andrea Alù Department of Electrical and Computer Engineering The University of Texas at Austin Austin Texas 78712 USA Photonics Initiative Advanced Science Research Center City University of New York New York New York 10031 USA Physics Program Graduate Center City University of New York New York New York 10026 USA Department of Electrical Engineering City College of New York New York New York 10031 USA

Metasurfaces have introduced large flexibility in manipulating the impinging wavefront for light and sound by locally engineering the reflection and transmission coefficients based on generalized Snell’s laws. Local phenomena in each unit cell, however, are fundamentally limited in the level of efficiency with which anomalous wavefront transformations can be achieved. Here, we explore acoustic metasurfaces with suitably engineered nonlocality, obtained by coupling neighboring cells. We demonstrate that nonlocal passive metastructures can overcome the limitations of local designs, and mimic balanced gain and loss distributions, enabling unitary efficiency for extreme beam steering.

关键词： Acoustic metamaterials Acoustic wave phenomena Beam control Beam optics Light propagation, transmission & absorption

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