基于二氧化钒复合超表面的太赫兹带宽可调极化转换器  

Tunable-Bandwidth Terahertz Polarization Converter Based on a Vanadium Dioxide Hybrid Metasurface

作　　者：杨朝晖 江明珠 刘永琛 张隆辉[1] 徐卫林 王月娥[1] 胡放荣[1] Yang Zhaohui;Jiang Mingzhu;Liu Yongchen;Zhang Longhui;Xu Weilin;Wang Yue’e;Hu Fangrong(College of Electronic Engineering and Automation,Guilin University of Electronic Technology,Guilin 541004,China;Guilin Institute of Information Technology,Guilin,Guangxi 541004,China)

机构地区：[1]桂林电子科技大学电子工程与自动化学院,广西桂林541004 [2]桂林信息科技学院,广西桂林541004

出　　处：《中国激光》2021年第17期184-191,共8页Chinese Journal of Lasers

基　　金：国家自然科学基金(62065005);广西自然科学基金(2020GXNSFDA238019,2018GXNSFAA050043);广西测试技术与仪器重点实验室项目(YQ21101);桂林电子科技大学研究生教育创新计划项目(2020YCXB04)。

摘　　要：设计了一种基于二氧化钒(VO_(2))复合超表面的太赫兹带宽可调极化转换器。该转换器由VO_(2)复合超表面、聚酰亚胺(PI)介质层和金属基底构成。其中,VO_(2)复合超表面的单元结构包含一个金属圆环、两根金属棒和嵌在其中的一小块VO_(2)。VO_(2)为绝缘态时,转换器在1.58~2.08 THz范围内交叉极化的反射率可达80%以上,极化转换率(PCR)大于95%,具有很强的极化转换效果。通过电触发使VO_(2)相变为金属态时,交叉极化的反射率在80%以上的频段缩小为2.04~2.08 THz,此频段的PCR大于95%。并且,VO2相变使PCR在95%以上的相对带宽由27%降低到1.9%。此外,还分析了PI介质层厚度与入射极化角度对器件PCR的影响。其中,当太赫兹波沿40°~55°极化方向入射时,PCR均高于80%。这种带宽可调的宽带极化转换器在未来太赫兹通信、成像等领域有潜在的应用价值。Objective Polarization is an important characteristic of terahertz(THz)waves and is widely applied in THz communications,imaging,sensing,detection,and other fields.Traditional THz polarization converters have large volumes,narrow bandwidths,and poor integration capabilities because they are based on the birefringence of materials.Metasurface polarization converters provide a potentially useful alternative.A metasurface is an ultrathin material comprising aplanar array of subwavelength unit cells that can control THz waves with high performance.However,conventional metasurface polarization converters have a single function and a fixed bandwidth;thus,they cannot provide dynamic modulation.In this paper,we propose a THz-bandwidth,tunable polarization converter based on a vanadium dioxide(VO_(2))hybrid metasurface.VO_(2)is a typical phase-transition material that can change from an insulating state to a metallic state under an external optical,electrical,or thermal stimulus when its temperature exceeds 68℃.During the phase transition,its electrical conductivity increases by about four orders of magnitude.Our proposed device can modulate the polarization of a THz wave by dynamically controlling the phase transition of VO_(2).Methods The proposed polarization converter comprises three layers:a metal substrate,an intermediate polyimide(PI)dielectric layer,and a VO_(2)composite metasurface.The resonant structure of the converter comprises a metal ring,with two metal rods crossing a diameter,and a piece of VO_(2)embedded in the middle of the two metal rods.We used the full-wave electromagnetic simulation software CST Microwave Studio 2019to simulate the performance of this converter.In the simulation,we used periodic boundary conditions in the x-and y-directions,and open boundary in the z-direction.The THz wave is incident normal to the surface from the-z-direction,and the polarization angle is set at a counterclockwise deflection ofθ=45°relative to the+x-axis.We obtained reflection amplitude spectra for co-polarizati

关 键 词：太赫兹技术 二氧化钒 复合超表面 极化转换器 带宽可调 相变材料 

分 类 号：O436[机械工程—光学工程]