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arXiv 2023年

作者： Wang, Dong Chen, Hongsheng Qiu, Cheng-Wei Li, Ying 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 Jinhua Institute of Zhejiang University Zhejiang University Jinhua321099 China Department of Electrical and Computer Engineering National University of Singapore Singapore117583 Singapore

The Hamiltonian interprets how the system evolves, while the scattering coefficients describe how the system responds to inputs. Recent studies on non-Hermitian physics have revealed many unconventional effects. However, in all cases, the non-Hermiticity such as material loss is only considered for the Hamiltonian, even when studying scattering properties. Another important component-the scattering channel, is always assumed to be lossless and time-reversal symmetric. This assumption hinders the exploration on the more general and fundamental properties of non-Hermitian scattering. Here, we identify a novel kind of scattering channel that obeys time-reversal anti-symmetry. Such diffusive scattering channels overturn the conventional understanding about scattering symmetry by linking the positive and negative frequencies. By probing non-Hermitian systems with the diffusive channels, we reveal a hidden anti-parity-time (APT) scattering symmetry, which is distinct from the APT symmetry of Hamiltonians studied before. The symmetric and symmetry broken scattering phases are observed for the first time as the collapse and revival of temperature oscillation. Our work highlights the overlooked role of scattering channels in the symmetry and phase transition of non-Hermitian systems, thereby gives the diffusion the new life as a signal carrier. Our findings can be utilized to the analysis and control of strongly dissipative phenomena such as heat transfer and charge diffusion. © 2023, CC BY.

关键词： Hamiltonians

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Ultrawideband chromatic aberration-free meta-mirrors

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advanced Photonics 2021年第1期3卷 47-56页

作者： Tong Cai Shiwei Tang Bin Zheng Guangming Wang Wenye Ji Chao Qian Zuojia Wang Erping Li Hongsheng Chena Zhejiang University College of Information Science and Electronic EngineeringInterdisciplinary Center for Quantum InformationState Key Laboratory of Modern Optical InstrumentationHangzhouChina Air Force Engineering University Air and Missile Defend CollegeXi’anChina Zhejiang University ZJU-Hangzhou Global Science and Technology Innovation CenterKey Laboratory of Advanced Micro/Nano Electronic Devices and Smart Systems of ZhejiangHangzhouChina Ningbo University Department of PhysicsFaculty of ScienceNingboChina

Chromatic aberration-free meta-devices(e.g.,achromatic meta-devices and abnormal chromatic meta-devices)play an essential role in modern science and ***,current efforts suffer the issues of low efficiency,narrow operating band,and limited wavefront manipulation *** propose a general strategy to design chromatic aberration-free meta-devices with high-efficiency and ultrabroadband properties,which is realized by satisfying the key criteria of desirable phase dispersion and high reflection amplitudes at the target frequency *** phase dispersion is tuned successfully based on a multiresonant Lorentz model,and high reflection is guaranteed by the presence of the metallic *** proof of the concept,two microwave meta-devices are designed,fabricated,and experimentally *** achromatic meta-mirror is proposed within 8 to 12 GHz,and another abnormal chromatic meta-mirror can tune the reflection angle as a linear *** meta-mirrors exhibit very high efficiencies(85%to 94%in the frequency band).Our findings open a door to realize chromatic aberration-free meta-devices with high efficiency and wideband properties and stimulate the realizations of chromatic aberration-free metadevices with other functionalities or working at higher frequency.

关键词： chromatic aberration-free meta-devices ultrabroadband metasurface phase and dispersion control multiresonant Lorentz model

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Experimental observation of topological large-area pseudo-spin-momentum-locking waveguide states with exceptional robustness

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advanced Photonics Nexus 2024年第1期3卷 68-75页

作者： Liu He Zhihao Lan Bin Yang Jianquan Yao Qun Ren Jian Wei You Wei EISha Yuting Yang Liang Wu Tianjin University Ministry of EducationSchool of Precision Instruments and Opto-Electronics EngineeringKey Laboratory of Opto-Electronics Information Technology TianjinChina University College London Department of Electronic and Electrical EngineeringLondonUnited Kingdom University of Mining and Technology School of Materials Science and PhysicsXuzhouChina Tianjin University School of Electrical and Information EngineeringTianjinChina Southeast University School of Information Science and EngineeringState Key Laboratory of Millimeter WavesNanjingChina Zhejiang University College of Information Science and Electronic EngineeringKey Laboratory of Micro-Nano Electronic Devices and Smart Systems of Zhejiang ProvinceHangzhouChina

Unlike conventional topological edge states confined at a domain wall between two topologically distinct media,the recently proposed large-area topological waveguide states in three-layer heterostructures,which consist of a domain featuring Dirac points sandwiched between two domains of different topologies,have introduced the mode width degree of freedom for more flexible manipulation of electromagnetic *** now,the experimental realizations of photonic large-area topological waveguide states have been exclusively based on quantum Hall and quantum valley-Hall *** propose a new way to create large-area topological waveguide states based on the photonic quantum spin-Hall system and observe their unique feature of pseudo-spin-momentum-locking unidirectional propagation for the first time in ***,due to the new effect provided by the mode width degree of freedom,the propagation of these large-area quantum spin-Hall waveguide states exhibits unusually strong robustness against defects,e.g.,large voids with size reaching several unit cells,which has not been reported ***,practical applications,such as topological channel intersection and topological energy concentrator,are further demonstrated based on these novel *** work not only completes the last member of such states in the photonic quantum Hall,quantum valley-Hall,and quantum spin-Hall family,but also provides further opportunities for high-capacity energy transport with tunable mode width and exceptional robustness in integrated photonic devices and on-chip communications.

关键词： large-area quantum spin-Hall waveguide states strong robustness against defects high-capacity energy transport mode width degree of freedom

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Ultrafast control of braiding topology in non-Hermitian metasurfaces

arXiv

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arXiv 2024年

作者： Hu, Yuze Tong, Mingyu Ren, Ziheng Chen, Fujia Chen, Qiaolu Chen, Hongsheng Jiang, Tian Yang, Yihao Interdisciplinary Center for Quantum Information State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China Institute for Quantum Science and Technology College of Science National University of Defense Technology Changsha410073 China International Joint Innovation Center The Electromagnetics Academy Zhejiang University Zhejiang University Haining314400 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 College of Advanced Interdisciplinary Studies National University of Defense Technology Changsha410073 China

The mathematical theory of braids, influential across scientific disciplines, has emerged as a compelling strategy for light manipulation. Existing approaches to creating braids in photonics, whether in momentum-space bandstructures or real-space fields, often face limitations associated with static nature of devices and lack of tunability. Here, we experimentally demonstrate ultrafast control of eigen-spectrum braids of Jones matrices within mere picoseconds, in reconfigurable non-Hermitian metasurfaces. The Jones matrices of the metasurface exhibit a complex eigen-spectrum that braids in the three-dimensional eigenvalue-frequency space, thereby creating arbitrary elements within the two-string braid group, 2. By exciting the photoconductive semiconductor terahertz metasurface with a femtosecond infrared pulse, we achieve ultrafast switching of the braids, transitioning from the Solomon link to either the Trefoil knot or Hopf link. Our approach serves as a pivotal tool for elucidating non-trivial topology of braids and studying ultrafast topological optoelectronics. © 2024, CC BY.

关键词： Topology

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Scattering-free plasmonic Brewster effect via metasurfaces

arXiv

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arXiv 2024年

作者： Zhang, Xinyan Cui, Xingshuo Cai, Tong Cai, Weiqi Low, Tony Chen, Hongsheng Lin, Xiao Interdisciplinary Center for Quantum Information State Key Laboratory of Extreme Photonics and Instrumentation College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China International Joint Innovation Center The Electromagnetics Academy at Zhejiang University Zhejiang University Haining314400 China Air and Missile Defense College Air Force Engineering University Xi’an710051 China AVIC Research Institute for Special Structures of Aeronautical Composites Jinan250023 China Department of Electrical and Computer Engineering University of Minnesota MinneapolisMN55455 United States 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

The Brewster effect, dating back to the pioneering work of Sir David Brewster in 1815, offers a crucial route to achieve 100% energy conversion between the incident and transmitted propagating waves at an optical interface and is of fundamental importance to many practical applications, such as polarization filtering, beam steering, and optical broadband angular selectivity. However, whether the Brewster effect of surface waves can be implemented without the involvement of negative-permittivity or negative-permeability materials remains elusive. This is due to the formidable challenge to fully suppress both the parasitic scattering into propagating waves and the reflection into surface waves under the incidence of surface waves. Here, we reveal a feasible route to achieve scattering-free plasmonic Brewster effect via isotropic metasurfaces, along with the usage of positive-permittivity and positive-permeability metamaterials with both anisotropic and magnetic responses. In essence, the anisotropic response of metamaterials is judiciously designed to fully suppress the parasitic scattering into propagating waves, while the magnetic response of metamaterials facilitates the full suppression of the reflection into surface waves supported by metasurfaces. Moreover, we find that this plasmonic Brewster effect via metasurfaces can be further engineered to occur for arbitrary incident angles, giving rise to the exotic phenomenon of all-angle scattering-free plasmonic Brewster effect. © 2024, CC BY.

关键词： Surface waves

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Multiple Brillouin Zone Winding of Topological Chiral Edge States for Slow Light Applications

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Physical Review Letters 2024年第15期132卷 156602-156602页

作者： Fujia Chen Haoran Xue Yuang Pan Maoren Wang Yuanhang Hu Li Zhang Qiaolu Chen Song Han Gui-geng Liu Zhen Gao Peiheng Zhou Wenyan Yin Hongsheng Chen Baile Zhang 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 Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute of Zhejiang University Zhejiang University Jinhua 321099 China Shaoxing Institute of Zhejiang University Zhejiang University Shaoxing 312000 China Department of Physics The Chinese University of Hong Kong Shatin Hong Kong SAR China Key Laboratory of Multi-spectral Absorbing Materials and Structures of Ministry of Education University of Electronic Science and Technology of China Chengdu 611731 China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore 637371 Singapore Centre for Disruptive Photonic Technologies The Photonics Institute Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore Department of Electrical and Electronic Engineering Southern University of Science and Technology Shenzhen 518055 China

Photonic Chern insulators are known for their topological chiral edge states (CESs), whose absolute existence is determined by the bulk band topology, but concrete dispersion can be engineered to exhibit various properties. For example, the previous theory suggested that the edge dispersion can wind many times around the Brillouin zone to slow down light, which can potentially overcome fundamental limitations in conventional slow-light devices: narrow bandwidth and keen sensitivity to fabrication imperfection. Here, we report the first experimental demonstration of this idea, achieved by coupling CESs with resonance-induced nearly flat bands. We show that the backscattering-immune hybridized CESs are significantly slowed down over a relatively broad bandwidth. Our work thus paves an avenue to broadband topological slow-light devices.

关键词： Light propagation, transmission & absorption Metamaterials Photonic crystals Polaritons Topological materials

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High Area Efficiency Bidirectional Scr for Low-Voltage Esd Protection

SSRN

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SSRN 2023年

作者： Zhou, Shicong Chen, Yipeng Zhu, Xinyu Dong, Shurong Wong, Hei Gao, Zhiliang Wang, Ruojue Wang, Bin Key Laboratory of Micro-nano Electronic Devices and Smart Systems of Zhejiang Province College of Information Science & Electronic Engineering Hangzhou310027 China Beijing Smartchip Microelectronics Technology Co. Ltd Shanghai China Department of Electrical Engineering City University of Hong Kong Hong Kong Beijing Orient Institute of Measurement and Test Beijing100094 China

An enhanced diode-triggered silicon-controlled rectifier (EDTSCR) is proposed to meet the requirement of bi-directional electrostatic discharge (ESD) protection for low-voltage Integrated circuits (ICs). Based on the conventional diode-triggered silicon-controlled rectifier (DTSCR), the newly proposed EDTSCR incorporates an additional PMOS and NMOS, respectively, in the N-Well and P-Well to offer additional current paths along the surface which enhances the robustness of the device significantly. TCAD simulation shows that the EDTSCR is still triggered by the diode strings but has a more uniform current distribution for the ON state because of the additional surface current paths. The proposed EDTSCR has excellent dual-directional ESD protection performance with a figure of merit (FOM) of 4.91 mA/um2 which results in about 75% improvement as compared with the conventional DTSCR realized with the same process. EDTSCR also has higher area efficiency, lower trigger voltage, lower current leakage and faster turn-on speed than the DTSCR. The proposed EDTSCR is an attractive ESD protection solution for ultralow voltage ICs. © 2023, The Authors. All rights reserved.

关键词： Diodes

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Localization of Chiral Edge States by the Non-Hermitian Skin Effect

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Physical Review Letters 2024年第11期132卷 113802-113802页

作者： Gui-Geng Liu (刘癸庚) Subhaskar Mandal Peiheng Zhou Xiang Xi Rimi Banerjee Yuan-Hang Hu Minggui Wei Maoren Wang Qiang Wang Zhen Gao Hongsheng Chen Yihao Yang Yidong Chong Baile Zhang Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore 637371 Singapore National Engineering Research Center of Electromagnetic Radiation Control Materials State Key Laboratory of Electronic Thin Film and Integrated Devices University of Electronic Science and Technology of China Chengdu 610054 China School of Electrical Engineering and Intelligentization Dongguan University of Technology Dongguan 523808 China School of Physics Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing Jiangsu 210093 China Department of Electrical and Electronic Engineering Southern University of Science and Technology Shenzhen 518055 China Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation ZJU-Hangzhou Global Science and Technology Innovation Center College of Information Science and Electronic Engineering Key Laboratory of Advanced Micro/Nano Electronic Devices and Smart Systems of Zhejiang ZJU-UIUC Institute Zhejiang University Hangzhou 310027 China Centre for Disruptive Photonic Technologies The Photonics Institute Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore

Quantum Hall systems host chiral edge states extending along the one-dimensional boundary of any two-dimensional sample. In solid state materials, the edge states serve as perfectly robust transport channels that produce a quantized Hall conductance; due to their chirality, and the topological protection by the Chern number of the bulk band structure, they cannot be spatially localized by defects or disorder. Here, we show experimentally that the chiral edge states of a lossy quantum Hall system can be localized. In a gyromagnetic photonic crystal exhibiting the quantum Hall topological phase, an appropriately structured loss configuration imparts the edge states’ complex energy spectrum with a feature known as point-gap winding. This intrinsically non-Hermitian topological invariant is distinct from the Chern number invariant of the bulk (which remains intact) and induces mode localization via the “non-Hermitian skin effect.” The interplay of the two topological phenomena—the Chern number and point-gap winding—gives rise to a non-Hermitian generalization of the paradigmatic Chern-type bulk-boundary correspondence principle. Compared to previous realizations of the non-Hermitian skin effect, the skin modes in this system have superior robustness against local defects and disorders.

关键词： Edge states Photonic crystals Quantum Hall effect Chern insulators Non-Hermitian systems

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Type-II Dirac points and topological Fermi arcs in nonlocal metamaterials

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Physical Review B 2022年第23期106卷 235303-235303页

作者： Mingzhu Li Ning Han Liang Peng Shuang Zhang School of Information and Electrical Engineering Zhejiang University City College Hangzhou 310015 China 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 Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang ZJU-UIUC Institute Zhejiang University Hangzhou 310027 China Department of Physics University of Hong Kong Hong Kong China Department of Electrical & Electronic Engineering University of Hong Kong Hong Kong China

Dirac semimetals are topological materials with degenerated Dirac points in their band structures. In particular, the Dirac points play a central role in the topologically protected phases. Recently, it was reported that the peculiar type-II Dirac points could be realized in photonics by means of photonic crystals (PCs). Nevertheless, the practical implementation is rather challenging. In this paper, we demonstrate that the nonlocal effect in the interior of a homogeneous photonic metamaterial (HPM) enables the existence of type-II Dirac points in the HPM's band structure. With theoretical formulations and numerical evaluations, we discuss the evolution of the HPM's band type and present the interesting transition between type-I and type-II Dirac degeneracy of the HPMs. Remarkably, a pair of the type-II Dirac points can be generated at two different frequencies, which is supported by the mode overlapping in the HPMs with weak nonlocality. The Fermi arc surface states connect the projections of the type-II Dirac points at the boundary between the vacuum and HPMs. The topological protection of the Fermi arc surface states is verified by the reflectionless transmission with sharp corners. Our paper provides a fundamental understanding of topological photonics by type-II Dirac points in HPMs.

关键词： Surface states Topological phases of matter Dirac semimetal Topological materials

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Realizing transmitted metasurface cloak by a tandem neural network

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Photonics Research 2021年第5期9卷 I0062-I0068页

作者： ZHENG ZHEN CHAO QIAN YUETIAN JIA ZHIXIANG FAN RAN HAO TONG CAI BIN ZHENG HONGSHENG CHEN ERPING LI Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical InstrumentationCollege of Information Science and Electronic EngineeringZhejiang UniversityHangzhou 310027China ZJU-Hangzhou Global Science and Technology Innovation Center Key Laboratory of Advanced Micro/Nano Electronic Devices&Smart Systems of ZhejiangZhejiang UniversityHangzhou 310027China International Joint Innovation Center ZJU-UIUC Institute Zhejiang UniversityHaining 314400China College of Optical and Electronic Technology China Jiliang UniversityHangzhou 310018China

Being invisible at will has been a long-standing dream for centuries, epitomized by numerous legends;humans have never stopped their exploration steps to realize this dream. Recent years have witnessed a breakthrough in this search due to the advent of transformation optics, metamaterials, and metasurfaces. However, the previous metasurface cloaks typically work in a reflection manner that relies on a high-reflection background, thus limiting the applications. Here, we propose an easy yet viable approach to realize the transmitted metasurface cloak, just composed of two planar metasurfaces to hide an object inside, such as a cat. To tackle the hard-to-converge issue caused by the nonuniqueness phenomenon, we deploy a tandem neural network(T-NN) to efficiently streamline the inverse design. Once pretrained, the T-NN can work for a customer-desired electromagnetic response in one single forward computation, saving a great amount of time. Our work opens a new avenue to realize a transparent invisibility cloak, and the tandem-NN can also inspire the inverse design of other metamaterials and photonics.

关键词： inverse uniqueness breakthrough

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