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Pancharatnam–Berry metasurface for terahertz wave radar cross section reduction

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Chinese Physics B 2019年第9期28卷 220-226页

作者：李绍和李九生 Center for THz Research China Jiliang University

The digital coding metasurfaces need several kinds of meta-particle structures to obtain corresponding electromagnetic wave responses and require time-consuming optimization.In this paper, we present train-symbol-shaped meta-particles with various orientations utilizing Pancharatnam-Berry(PB) phase to achieve 1-, 2-, and 3-bit digital coding metasurfaces.Terahertz wave scattering patterns of the coding metasurfaces with regular and random sequences are given and discussed.They have strongly suppressed backward scattering with approximately-13.5 dB radar cross section(RCS) reduction in a wide band range from 0.85 THz to 1.6 THz.The proposed digital coding metasurfaces provide a simple way and new opportunities for manipulating terahertz wave scattering with polarization independence.

关键词： terahertz metasurface terahertz optics terahertz polarization

Aperture efficiency and mode constituent analysis for OAM vortex beam generated by digital metasurface

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Chinese Physics B 2019年第3期28卷 185-191页

作者：张迪曹祥玉杨欢欢高军吕世奇 Air Force Engineering University Xi’an 710077China

A systematic study of the aperture efficiency and mode constituent for orbital angular momentum(OAM) vortex beam generated by digital metasurface is presented. The aperture efficiency and OAM spectrum are computed for different bit numbers. It is found that the aperture efficiency declines for digital metasurface due to the phase quantization error,especially for 1-bit device. Fortunately, the OAM spectrum is barely affected by phase quantization and the designated main mode keeps dominant for different bit numbers, indicating that high purity OAM vortex beam can be generated by digital metasurface. Besides, the influence of topological charge l is also investigated. For a fixed metasurface, the radiation performance deteriorates sharply with the growing of l and the parasitic OAM mode becomes dominant at certain angle.At last, a prototype of 1-bit metasurface was simulated, fabricated and measured in anechoic chamber. The simulation and experiment results verify the correctness of the numerical analysis.

关键词： orbital angular momentum(OAM) efficiency mode constituent metasurface

A reconfigurable terahertz polarization converter based on metal–graphene hybrid metasurface

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Chinese Optics Letters 2020年第1期18卷 105-109页

作者：黄俊翔傅涛李海鸥首照宇高喜 School of Information and Communication Guilin University of Electronic TechnologyGuilin 541004China Key Laboratory of THz Technology Ministry of EducationChengdu 610054China

A metal-graphene hybrid metasurface polarization converter is designed in this Letter.The unit cell of the hybrid metasurface is composed of a butterfly-shaped structure whose branches are connected by multi-layer graphene sheets.The proposed device can be reconfigured from linear-to-circular polarization to cross-polarization by changing the Fermi energy of graphene.The simulation results show that for three-layer graphene,the device acts as a linear-to-circular polarization converter when EF=0 eV and switches to a cross-polarization converter when EF=0.5 eV.Compared with single-layer graphene,the device with three-layer graphene can maintain the cross-polarization conversion performance under low Fermi energy.Furthermore,two equivalent circuits in the x and y directions are developed to understand the working mechanism of the device.

关键词： graphene metasurface polarization converter THz

Shared aperture metasurface antenna for electromagnetic vortices generation with different topological charges

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Chinese Physics B 2021年第8期30卷 337-344页

作者：王贺李勇峰屈绍波 Department of Basic Sciences Air Force Engineering UniversityXi'an 710051China

Vortex beams carrying orbital angular momentum(OAM)have aroused great interest of both scientific and engineering communities.Encouragingly,generating OAM with different topological charges in a shared aperture is regarded as a potential route to expanding the communication capacity,which yet is an academic challenging task.In this work,a paradigm of designing metasurface-based shared aperture antenna for generating polarization-dependent vortex beams with distinct topological charges is proposed.Anisotropic unit cells that can tailor different resonance phase profiles in two orthogonal orientations are used to assemble a metasurface reflector.As a proof-of-concept,a planar reflector antenna is designed with two Vivaldi sources,which can generate x-and y-polarized vortex beams with topological charges of l=-1 and l=-2,respectively.Both the simulation results and the measurement results are in good agreement,which demonstrates the feasibility of our design.Significantly,this work provides a new route to achieving vortex beams carrying different topological charges in the same frequency band,which may have potential applications in communication systems.

关键词： metasurface electromagnetic vortex antenna orbital angular momentum

Metamaterials:From fundamental physics to intelligent design

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Interdisciplinary Materials 2023年第1期2卷 5-29页

作者： Ji Chen Shanshan Hu Shining Zhu Tao Li National Laboratory of Solid State Microstructures Key Laboratory of Intelligent Optical Sensing and ManipulationsJiangsu Key Laboratory of Artificial Functional MaterialsCollege of Engineering and Applied SciencesSchool of PhysicsNanjing UniversityNanjingChina National Mobile Communications Research Laboratory School of Information Science and EngineeringFrontiers Science Center for Mobile Information Communication and SecuritySoutheast UniversityNanjingChina

Metamaterials are artificial structures with the ability to efficiently control light-field,attracting intensive attention in the past few decades.People have studied the working principles,design strategies,and fabrication methods of metamaterials,making this field cross and combine with many disciplines,including physics,material science,electronics,and chemistry.In recent years,with the rapid development of high-efficiency and multifunctional metasurfaces,which are a two-dimensional version of metamaterials,great efforts have been made to push this material to practical applications.In particular,the introduction of artificial intelligent(AI)algorithms enables metamaterials-based photonic devices that exhibit excellent performances and intelligent functionalities.In this review,we first introduce the basic concepts,working principles,design methods,and applications of metamaterials,and then focus on the rapidly developing metamaterials research combined with AI algorithms.Finally,we conclude this review with personal perspectives on the current problems and future directions of metamaterials research and developments.

关键词： artificial intelligence artificial neural network inverse design metamaterial metasurface

Manipulation of acoustic wavefront by transmissive metasurface based on pentamode metamaterials

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Chinese Physics B 2019年第2期28卷 306-312页

作者：刘颖李义丰刘晓宙 College of Computer Science and Technology Nanjing Tech University Key Laboratory of Modern Acoustics Ministry of EducationNanjing University Key Laboratory of Modern Acoustics Ministry of EducationInstitute of Acoustics and School of PhysicsNanjing University

An underwater acoustic metasurface with sub-wavelength thickness is designed for acoustic wavefront manipulation.In this paper, a pentamode lattice and a frequency-independent generalized acoustic Snell's law are introduced to overcome the limitations of narrow bandwidth and low transmittance. The bulk modulus and effective density of each unit cell can be tuned simultaneously, which are modulated to guarantee the achievement of refractive index profile and high transmission. Here, we actualize anomalous refraction, generation of non-diffracting Bessel beam, sub-wavelength flat focusing,and surface wave conversion by constructing inhomogeneous acoustic metasurface. This design approach has potential applications in medical ultrasound imaging and underwater acoustic communications.

关键词： metasurface frequency-independent pentamode high transmission

A waveguide metasurface based quasi-far-field transverse-electric superlens

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Opto-Electronic Advances 2021年第10期4卷 24-29页

作者： Yechuan Zhu Xiaolin Chen Weizheng Yuan Zhiqin Chu Kwok-yin Wong Dangyuan Lei Yiting Yu Shaanxi Province Key Laboratory of Micro and Nano Electro-Mechanical Systems Northwestern Polytechnical UniversityXi’an 710072China Key Laboratory of Micro/Nano Systems for Aerospace(Ministry of Education) Northwestern Polytechnical UniversityXi’an 710072China Shaanxi Province Key Laboratory of Thin Films Technology and Optical Test Xi’an Technological UniversityXi’an 710021China Department of Optical Engineering School of Electronic Science&Applied PhysicsHefei University of TechnologyHefei 230601China Department of Applied Biology and Chemical Technology The Hong Kong Polytechnic UniversityHung HomHong Kong 999077China Department of Electrical and Electronic Engineering Joint Appointment with School of Biomedical SciencesThe University of Hong KongHong Kong 999077China Department of Materials Science and Engineering City University of Hong KongHong Kong 999077China

The imaging capability of conventional lenses is mainly limited by the diffraction of light,and the so-called superlens has been developed allowing the recovery of evanescent waves in the focal plane.However,the remarkable focusing behavi-or of the superlens is greatly confined in the near-field regime due to the exponential decay of evanescent waves.To tackle this issue,we design a waveguide metasurface-based superlens with an extraordinary quasi-far-field focusing capability beyond the diffraction limit in the present work.Specifically,we analyze the underlying physical mechanism and provide experimental verification of the proposed superlens.The metasurface superlens is formed by an array of gradient nanoslits perforated in a gold slab,and supports transverse-electric(TE)waveguide modes under linearly polar-ized illumination along the long axis of the slits.Numerical results illustrate that exciting such TE waveguide modes can modulate not only optical phase but also evanescent waves.Consequently,some high-spatial-frequency waves can con-tribute to the focusing of the superlens,leading to the quasi-far-field super-resolution focusing of light.Under 405 nm illu-mination and oil immersion,the fabricated superlens shows a focus spot of 98 nm(i.e.λ/4.13)at a focal distance of 1.49μm(i.e.3.68λ)using an oil immersion objective,breaking the diffraction limit ofλ/2.38 in the quasi-far field regime.The developed metasurface optical superlens with such extraordinary capabilities promises exciting avenues to nanolitho-graphy and ultra-small optoelectronic devices.

关键词： superlens metasurface waveguide quasi-far-field super-resolution focusing breaking the diffraction limit

Broadband terahertz rotator with an all-dielectric metasurface

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Photonics Research 2018年第11期6卷 1056-1061页

作者： QUANLONG YANG XIEYU CHEN QUAN XU CHUNXIU TIAN YUEHONG XU LONGQING CONG XUEQIAN ZHANG YANFENG LI CAIHONG ZHANG XIXIANG ZHANG JIAGUANG HAN WEILI ZHANG Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering Tianjin University and the Key Laboratory of Optoelectronics Information and Technology Tianjin Ministry of Education of China Physical Science and Engineering Division King Abdullah University of Science and Technology Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Research Institute of Superconductor Electronics (RISE) School of Electronic Science and Engineering Nanjing University School of Electrical and Computer Engineering Oklahoma State University

Polarization manipulation is essential in developing cutting-edge photonic devices ranging from optical communication displays to solar energy harvesting. Most previous works for efficient polarization control cannot avoid utilizing metallic components that inevitably suffer from large ohmic loss and thus low operational efficiency.Replacing metallic components with Mie resonance-based dielectric resonators will largely suppress the ohmic loss toward high-efficiency metamaterial devices. Here, we propose an efficient approach for broadband, highquality polarization rotation operating in transmission mode with all-dielectric metamaterials in the terahertz regime. By separating the orthogonal polarization components in space, we obtain rotated output waves with a conversion efficiency of 67.5%. The proposed polarization manipulation strategy shows impressive robustness and flexibility in designing metadevices of both linear-and circular-polarization incidences.

关键词： Broadband terahertz rotator THz all-dielectric metasurface

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metasurface反射效率研究与应用

Metasurface反射效率研究与应用

作者：陈龙电子科技大学

学位级别：硕士

当metasurface被提出以后,基于其不同反射效率或传输效率的应用就获得了快速发展。其中,反射型metasurface由于体积小、重量轻及加工工艺成熟等优点在不同领域都有广泛应用。本文主要围绕不同反射效率的反射型metasurface进行了深入探... 详细信息

当metasurface被提出以后,基于其不同反射效率或传输效率的应用就获得了快速发展。其中,反射型metasurface由于体积小、重量轻及加工工艺成熟等优点在不同领域都有广泛应用。本文主要围绕不同反射效率的反射型metasurface进行了深入探索和研究,更进一步,通过结合设计其反射相位特征拓展了metasurface反射阵列应用范围。第一章主要介绍了研究背景及意义,同时,对不同电磁现象的人工复合材料进行了区别定义。然后,回顾了metasurface的起源、发展历程以及国内外研究动态。最后,详细给出了本文主要研究内容和相关结构安排。第二章主要介绍了四种metasurface反射效率理论研究方法并指出了各自的优缺点。同时,在太赫兹频段,提出了一种双环结构阵列组成的metasurface的等效电路模型并进行了分析讨论,为后面设计不同反射效率的metasurface应用提供了理论基础和指导。第三章分别在太赫兹频段研究了基于双环结构贴片单元调谐的两种不同反射效率的metasurface应用:一种低反射效率的metasurface吸波材料;一种高反射效率的metasurface反射阵列。其中,metasurface吸波材料具有对入射波极化不敏感特性并在大角度斜入射下仍能保持良好性能;metasurface反射阵列能够在太赫兹频率表现出较高天线效率。最后,分别加工和测试了它们的实物样品,并详细讨论了在该频段下加工和测试中出现的相关问题,为其它太赫兹设备加工测试提供了重要参考价值。第四章提出了metasurface反射阵列的调制电磁波轨道角动量应用。采用双环和一个偶极子谐振结构,在较宽的频带内实现了接近平行的反射相移曲线。基于该单元设计并加工了两款20×20的metasurface反射阵列,成功实现了轨道角动量模式为1和2的调制效果,能有效提高频谱利用率。第五章为总结和展望。

关键词： metasurface 反射效率吸波材料反射阵列轨道角动量