基于双箭头超表面宽带太赫兹涡旋光束的产生  

Generation of Broadband Terahertz Vortex Beam Based on Double-Arrow Metasurface

作　　者：郭姣艳 李文宇 孙然[1,2,3] 赵国忠 Guo jiaoyan;Li Wenyu;Sun Ran;Zhao Guozhong(Department of Physics,Capital Normal University,Beijing 100048,China;Beijing Advanced Innovation Center for Imaging Theory and Technology,Beijing 100048,China;Key Laboratogy of Terahertz Optoelectronics,Ministry of Education,Capital Normal University,Beijing 100048,China)

机构地区：[1]首都师范大学物理系,北京100048 [2]北京成像理论与技术高精尖创新中心,北京100048 [3]首都师范大学太赫兹光电子学教育部重点实验室,北京100048

出　　处：《中国激光》2021年第20期188-194,共7页Chinese Journal of Lasers

基　　金：国家自然科学基金(62071312)。

摘　　要：涡旋光束在提高通信能力方面的巨大潜力日益受到人们的青睐,而宽带特性是提高信道容量的关键。此外,当前涡旋光束产生器件存在着带宽窄、效率低等缺点。因此,设计了一种基于Pancharatnam-Berry相位的超宽带反射超表面,该超表面由13×13单层旋转反射单元结构组成,在频率范围为0.9~1.8 THz内可产生太赫兹涡旋光束。结果表明,该涡旋光束产生器件可以实现高效率(工作效率在90%以上)和较宽的工作频率,这为高性能宽带涡旋光束产生器的设计开辟了一条新途径。Objective An electromagnetic wave with a spiral wavefront is a vortex beam with an orbital angular momentum(OAM).The OAM vortex beam has a phase factor exp(i lφ),φis the azimuth angle,and l is the topological charge(integer or non-integer).The vortex beam’s wavefront propagates in a spiral forward,and the intensity of the beam center is close to zero.This unique electromagnetic characteristic has potential applications in optics,atomic physics,and communications.In recent years,the massive capability potential has benefited humans,and the broadband characteristics are the key to effectively improving the channel capacity.Most of the current vortex beam generating devices have shortcomings such as narrow bandwidth and low working efficiency.Methods like spiral phase plates and spatial light modulators are employed in previous studies to generate vortex beams.These methods produce optical devices with issues such as large size and high price.Because metasurfaces can control the phase,amplitude,and polarization of electromagnetic wavefronts,using metasurfaces to generate vortex beams has become a novel method.This method is simple in structure and low in loss,making it ideal for integration development.Methods This paper proposes a terahertz broadband vortex beam generator based on the metasurface of a singlelayer double-arrow unit structure.The device is composed of a three-layer metasurface-dielectric-metal structure.The top layer is a metasurface consisting of double-arrow metal structural units,the middle layer is a polyimide,and the bottom metal layer is gold.CST MICROWAVE STUDIO is employed to simulate the reflection performance of the unit structure.Better performance is obtained after optimizing the structural parameters,and a set of optimized structural parameters is determined(Fig.2).The reflection characteristics of the top single-layer double-arrow unit with its center as the origin and the z-axis as the rotation axis are analyzed when the incident light is set as a circularly polarized wave.Reflecti

关 键 词：光通信 太赫兹 涡旋光束 宽带 超表面 

分 类 号：O436[机械工程—光学工程]