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Extended-localized transition in diffusive quasicrystals

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arXiv 2022年

作者： Liu, Zhoufei Cao, Pei-Chao Li, Ying Huang, Jiping Fudan University Shanghai200438 China State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China International Joint Innovation Center Key Laboratory of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang The Electromagnetics Academy of Zhejiang University Zhejiang University Haining314400 China Shaoxing Institute of Zhejiang University Zhejiang University Shaoxing312000 China

Compared to periodic systems, quasicrystals without translational invariance exhibit unexpected localization properties. The extended-localized transition in quasicrystals has been observed in both quantum and classical wave systems. However, its manifestation in diffusion systems, which serve as novel platforms for exploring phases of matter in condensed matter physics, remains unexplored. Here, we present the implementation of the extended-localized transition in a diffusive quasicrystal based on the coupled ring chain structure. By modulating the thermal conductivities of rings, we obtain the diffusive one-dimensional Aubry-André-Harper (AAH) model, which exhibits an extended-localized transition. Thanks to the ring-shaped chain, we clearly demonstrate the extended-localized transition under the uniform excitation through temperature field simulations. For the localized state, the temperature field clearly demonstrates a multiple localization centers phenomenon, which has no counterpart in wave systems. We also quantitatively investigate the temperature evolution and size effect of this transition. Furthermore, the local excitation has been adopted to demonstrate the temperature field for both the extended and localized states. Besides, we implement the non-Hermitian diffusive AAH model by rotating rings, whose temperature field shows a moving multiple localization centers phenomenon in the localized phase. Finally, we give the experimental suggestions for the diffusive AAH model and propose a potential application named as double-trace distributed generator. Our results can facilitate the design of flexible thermal devices and efficient heat management. © 2022, CC BY.

关键词： Temperature

Performing optical logic operations by a diffractive neural network

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Light(Science & Applications) 2020年第1期9卷 1448-1454页

作者： Chao Qian Xiao Lin Xiaobin Lin Jian Xu Yang Sun Erping Li Baile Zhang Hongsheng Chen Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical InstrumentationCollege of Information Science and Electronic EngineeringZhejiang University310027 HangzhouChina ZJU-Hangzhou Global Science and Technology Innovation Center Key Lab.of Advanced Micro/Nano Electronic Devices&Smart Systems of ZhejiangZhejiang University310027 HangzhouChina Department of Electrical Engineering California Institute of TechnologyPasadenaCAUSA ZJU-UIUC Institute Zhejiang University310027 HangzhouChina Division of Physics and Applied Physics School of Physical and Mathematical SciencesNanyang Technological UniversitySingapore 637371Singapore

Optical logic operations lie at the heart of optical computing,and they enable many applications such as ultrahighspeed information ***,the reported optical logic gates rely heavily on the precise control of input light signals,including their phase difference,polarization,and intensity and the size of the incident *** to the complexity and difficulty in these precise controls,the two output optical logic states may suffer from an inherent instability and a low contrast ratio of ***,the miniaturization of optical logic gates becomes difficult if the extra bulky apparatus for these controls is *** such,it is desirable to get rid of these complicated controls and to achieve full logic functionality in a compact photonic *** a goal remains ***,we introduce a simple yet universal design strategy,capable of using plane waves as the incident signal,to perform optical logic operations via a diffractive neural ***,the incident plane wave is first spatially encoded by a specific logic operation at the input layer and further decoded through the hidden layers,namely,a compound Huygens’*** is,the judiciously designed metasurface scatters the encoded light into one of two small designated areas at the output layer,which provides the information of output logic ***,after training of the diffractive neural network,all seven basic types of optical logic operations can be realized by the same *** a conceptual illustration,three logic operations(NOT,OR,and AND)are experimentally demonstrated at microwave frequencies.

关键词： surface operations precise

Boundary-Induced Topological Chiral Extended States in Weyl Metamaterial Waveguides

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Physical Review Letters 2025年第19期134卷 196601-196601页

作者： Ning Han Fujia Chen Mingzhu Li Rui Zhao Wenhao Li Qiaolu Chen Li Zhang Yuang Pan Yuze Hu Mingyu Tong Lu Qi Jingwen Ma Zhi-Ming Yu Hongsheng Chen Yihao Yang State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou 310027 China International Joint Innovation Center The Electromagnetics Academy at Zhejiang University Zhejiang University Haining 314400 China Key Laboratory of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute of Zhejiang University Zhejiang University Jinhua 321099 China College of Optical and Electronic Technology China Jiliang University Hangzhou 310018 China School of Information and Electrical Engineering Hangzhou City University Hangzhou 310015 China School of Physical Science and Technology Yangzhou University Yangzhou 225002 China Faculties of Science and Engineering The University of Hong Kong Hong Kong China Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Beijing Institute of Technology Beijing 100081 China Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China

In topological physics, it is commonly understood that the existence of the boundary states of a topological system is inherently dictated by its bulk. A classic example is that the surface Fermi-arc states of a Weyl system are determined by the chiral charges of Weyl points within the bulk. Contrasting with this established perspective, here, we theoretically and experimentally discover a family of topological chiral bulk states extending over photonic Weyl metamaterial waveguides, solely induced by the waveguide boundaries, independently of the waveguide width. Notably, these chiral bulk states showcase discrete momenta and function as tunnels that connect Fermi-arc surface states living in different two-dimensional spaces via a third dimension. Our work offers an alternative mechanism for robust chiral bulk transport of waves and highlights the boundaries as a new degree of freedom to regulate bulk Weyl quasiparticles.

关键词： Degrees of freedom (mechanics)

Reconfigurable Three-Dimensional Thermal Dome

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arXiv 2023年

作者： Zhou, Yuhong Yang, Fubao Xu, Liujun Zhuang, Pengfei Wang, Dong Ouyang, Xiaoping Li, Ying Huang, Jiping Fudan University Shanghai200438 China Graduate School of China Academy of Engineering Physics Beijing100193 China School of Materials Science and Engineering Xiangtan University Xiangtan411105 China Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China International Joint Innovation Center Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang The Electromagnetics Academy of Zhejiang University Zhejiang University Haining314400 China

Thermal metamaterial represents a groundbreaking approach to control heat conduction, and, as a crucial component, thermal invisibility is of utmost importance for heat management. Despite the flourishing development of thermal invisibility schemes, they still face two limitations in practical ap plications. First, objects are typically completely enclosed in traditional cloaks, making them difficult to use and unsuitable for objects with heat sources. Second, although some theoretical proposals have been put forth to change the thermal conductivity of materials to achieve dynamic invisibility, their designs are complex and rigid, making them unsuitable for large-scale use in real three-dimensional spaces Here, we propose a concept of a thermal dome to achieve three-dimensional invisibility. Our scheme includes an open functional area, greatly enhancing its usability and applicability. It features a reconfigurable structure, constructed with simple isotropic natural materials, making it suitable for dynamic requirements. The performance of our reconfigurable thermal dome has been confirmed through simulations and experiments, consistent with the theory. The introduction of this concept can greatly advance the development of thermal invisibility technology from theory to engineering and provide inspiration fo other physical domains, such as direct current electric fields and magnetic fields. Copyright © 2023, The Authors. All rights reserved.

关键词： Metamaterials

Chiral and non-chiral swift mode conversion near an exceptional point with adiabaticity engineering

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arXiv 2023年

作者： Wang, Dong Huang, Wen-Xi Zhou, Bo Yu, Wenduo Cao, Pei-Chao Peng, Yu-Gui Zhou, Zheng-Yang Chen, Hongsheng Zhu, Xue-Feng Li, Ying State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China International Joint Innovation Center The Electromagnetics Academy Zhejiang University Haining314400 China Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute Zhejiang University Jinhua321099 China Shaoxing Institute Zhejiang University Shaoxing312000 China School of Physics and Innovation Institute Huazhong University of Science and Technology Wuhan430074 China Key Laboratory of Optical Field Manipulation of Zhejiang Province Department of Physics Zhejiang Sci-Tech University Hangzhou310018 China

The eigenvalue of a non-Hermitian Hamiltonian often forms a self-intersecting Riemann surface, leading to a unique mode conversion phenomenon when the Hamiltonian evolves along certain loop paths around an exceptional point (EP). However, two fundamental problems exist with the conventional scheme of EP encircling: the speed of mode conversion is restricted by the adiabatic requirement, and the chirality cannot be freely controlled. Here, we introduce a method which dynamically engineers the adiabaticity in the evolution of non-Hermitian Hamiltonians that allows for both chiral and non-chiral mode conversion on the same path. Our method is based on quantifying and controlling the instantaneous adiabaticity, allowing for non-uniform evolution throughout the entire path. We apply our method into the microwave waveguide system and by optimizing the distributed adiabaticity along the evolution loop, we achieve the same quality of mode conversion as conventional quasi-adiabatic evolution in only one-fourth of the time. Our approach provides a comprehensive and universal solution to address the speed and chirality challenges associated with EP encircling. It also facilitates the dynamic manipulation and regulation of non-adiabatic processes, thereby accelerating the operation and allowing for a selection among various mode conversion patterns. © 2023, CC BY.

关键词： Hamiltonians

Ideal type-Ⅱ Weyl points in topological circuits

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National Science Review 2021年第7期8卷 205-210页

作者： Rujiang Li Bo Lv Huibin Tao Jinhui Shi Yidong Chong Baile Zhang Hongsheng Chen Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation College of Information Science and Electronic Engineering Zhejiang University ZJU-Hangzhou Global Science and Technology Innovation Center Key Laboratory of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Zhejiang University Key Laboratory of In-Fiber Integrated Optics of Ministry of Education College of Physics and Optoelectronic Engineering Harbin Engineering University School of Software Engineering Xi'an Jiaotong University Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Centre for Disruptive Photonic Technologies Nanyang Technological University

Weyl points(WPs), nodal degenerate points in three-dimensional(3 D) momentum space, are said to be‘ideal' if they are symmetry-related and well-separated, and reside at the same energy and far from nontopological bands. Although type-II WPs have unique spectral characteristics compared with type-I counterparts, ideal type-II WPs have not yet been reported because of a lack of an experimental platform with enough flexibility to produce strongly tilted dispersion bands. Here, we experimentally realize a topological circuit that hosts only topological bands with a minimal number of four ideal type-II WPs. By stacking two-dimensional(2 D) layers of inductor-capacitor(LC) resonator dimers with the broken parity inversion symmetry(P), we achieve a strongly tilted band structure with two group velocities in the same direction, and topological surface states in an incomplete bandgap. Our results establish an ideal system for the further study of Weyl physics and other exotic topological phenomena.

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Plasmon hybridization induced by quasi bound state in the continuum of graphene metasurfaces oriented for high-accuracy polarization-insensitive two-dimensional sensors

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Chinese Optics Letters 2022年第4期20卷 65-70页

作者： Xiuyu Wang Jihong Xin Qun Ren Haocheng Cai Jiaqi Han Chengyi Tian Pengcheng Zhang Lijie Jiang Zhihao Lan Jianwei You Wei E.I.Sha Tianjin Key Laboratory of Imaging and Sensing Microelectronic Technology School of MicroelectronicsTianjin UniversityTianjin 300072China School of Electrical and Information Engineering Tianjin UniversityTianjin 300072China State Key Laboratory of Millimeter Waves School of Information Science and EngineeringSoutheast UniversityNanjing 210096China Key Laboratory of High Speed Circuit Design and EMC of Ministry of Education School of Electronic EngineeringXidian UniversityXi'an 710071China Huawei Technologies Company Ltd. Shanghai 518129China Department of Electronic and Electrical Engineering University College LondonLondon WC1E7JEUK Key Laboratory of Micro-Nano Electronic Devices and Smart Systems of Zhejiang Province College of Information Science and Electronic EngineeringZhejiang UniversityHangzhou 310027China

Plasmonics could provide compact and powerful solutions for manipulating light in deep-subwavelength dimensions,which is promising for a great range of nanophotonic technologies such as plasmonic rulers and ***,the effective area of enhanced localized field induced by surface plasmon polaritons is typically restricted to the structural *** this work,we propose a method to generate high quality-factor extended electromagnetic fields via hybridizing the superradiant state and the quasi bound state in the continuum of graphene *** coupling interaction involved operates as a three-level system with multiple sharp resonances immune to the polarization,which holds great promise for developing nanodevices with high sensing capacity in two dimensions.

关键词： plasmon hybridization quasi bound state in the continuum high-Q sensing

Non-Hermitian Dirac cones with valley-dependent lifetimes

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arXiv 2024年

作者： Xie, Xinrong Ma, Fei Rui, W.B. Dong, Zhaozhen Du, Yulin Xie, Wentao Zhao, Y.X. Chen, Hongsheng Gao, Fei Xue, Haoran State Key Laboratory of Extreme Photonics and Instrumentation International Joint Innovation Center The Electromagnetics Academy Zhejiang University Zhejiang University Haining314400 China ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute of Zhejiang University Zhejiang University Jinhua321099 China Shaoxing Institute of Zhejiang University Zhejiang University Shaoxing312000 China Department of Physics HKU-UCAS Joint Institute for Theoretical and Computational Physics at Hong Kong The University of Hong Kong Pokfulam Road Hong Kong HK Institute of Quantum Science & Technology The University of Hong Kong Pokfulam Road Hong Kong Department of Physics The Chinese University of Hong Kong Shatin Hong Kong

Relativistic quasiparticles emerging from band degeneracies in crystals play crucial roles in the transport and topological properties of materials and metamaterials. Quasiparticles are commonly described by Hermitian Hamiltonians, with non-Hermiticity usually considered detrimental. In this work, we show that such an assumption of Hermiticity can be lifted to bring quasiparticles into non-Hermitian regime. We propose a concrete lattice model containing two Dirac cones with valley-dependent lifetimes. The lifetime contrast enables an ultra-strong valley selection rule: only one valley can survive in the long-time limit regardless of the excitation, lattice shape and other details. This property leads to an effective parity anomaly with a single Dirac cone and offers a simple way to generate vortex states. Additionally, extending non-Hermitian features to boundaries generates valley kink states with valley-locked lifetimes, making them effectively unidirectional and more resistant against inter-valley scattering. All these phenomena are experimentally demonstrated in a non-Hermitian electric circuit lattice. Copyright © 2024, The Authors. All rights reserved.

关键词： Topology

High-Speed Efficient On-Chip Electro-Optic Modulator Based on Midinfrared Hyperbolic Metamaterials

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Physical Review Applied 2021年第3期16卷 034002-034002页

作者： Dongdong Li Hongbin Ma Qiwei Zhan Jie Liao Wen-Yan Yin Hongsheng Chen Haoliang Qian Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation College of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 China ZJU-Hangzhou Global Science and Technology Innovation Center Key Laboratory of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Zhejiang University Hangzhou 310027 China International Joint Innovation Center ZJU-UIUC Institute Zhejiang University Haining 314400 China

Integrated modulators are key components for on-chip optical communication and information processing, which have become leading technologies in the current information-growth era. Hence, high-speed, efficient, and compact integrated modulators are in high demand. However, the current integrated midinfrared modulators meet these requirements with difficulty. Here, we present a high-speed and efficient on-chip electro-optic modulator based on midinfrared hyperbolic metamaterials using stacking of graphene and hexagonal boron nitride. The length of the modulation region is only 60 nm, which is integrated on a plasmonic waveguide composed of hyperbolic metamaterials. The maximum modulation depth is up to 30 dB, and the 3-dB modulation speed can reach up to 50 GHz, which is supported by a detailed study of a small-signal frequency-response model. Our work provides an alternative scheme for the design of modulators with the requirements of sub-100-nm integration and 50-GHz modulation speed or even beyond, which can be directly implemented into a two-dimensional-materials-based photonic integrated circuits platform.

关键词： Hyperbolic metamaterials Integrated optics nanophotonics Optoelectronics Plasmonics 2-dimensional systems devices Infrared techniques