High efficiency and broad bandwidth terahertz vortex beam generation based on ultra-thin transmission Pancharatnam-Berry metasurfaces  

作　　者：Wenyu Li Guozhong Zhao Tianhua Meng Ran Sun Jiaoyan Guo 李文宇;赵国忠;孟田华;孙然;郭姣艳(Department of Physics,Capital Normal University,Beijing Key Laboratory for THz Spectroscopy and Imaging,Key Laboratory of THz Optoelectronics,Ministry of Education,Beijing 100048,China;Institute of Solid State Physics,Shanxi Datong University,Datong 037009,China)

机构地区：[1]Department of Physics,Capital Normal University,Beijing Key Laboratory for THz Spectroscopy and Imaging,Key Laboratory of THz Optoelectronics,Ministry of Education,Beijing 100048,China [2]Institute of Solid State Physics,Shanxi Datong University,Datong 037009,China

出　　处：《Chinese Physics B》2021年第5期667-672,共6页中国物理B（英文版）

基　　金：the National Natural Science Foundation of China(Grant No.62071312);the Important R&D Projects of Shanxi Province,China(Grant No.201803D121083);the Shanxi Scholarship Council(Grant No.2020-135).

摘　　要：The terahertz(THz)vortex beam generators are designed and theoretically investigated based on single-layer ultra-thin transmission metasurfaces.Noncontinuous phase changes of metasurfaces are obtained by utilizing Pancharatnam-Berry phase elements,which possess different rotation angles and are arranged on two concentric rings centered on the origin.The circularly polarized incident THz beam could be turned into a cross-polarization transmission wave,and the orbital angular momentum(OAM)varies in value by lh.The l values change from±1 to±5,and the maximal cross-polarization conversion efficiency that could be achieved is 23%,which nearly reaches the theoretical limit of a single-layer structure.The frequency range of the designed vortex generator is from 1.2 THz to 1.9 THz,and the generated THz vortex beam could keep a high fidelity in the operating bandwidth.The propagation behavior of the emerged THz vortex beam is analyzed in detail.Our work offers a novel way of designing ultra-thin and single-layer vortex beam generators,which have low process complexity,high conversion efficiency and broad bandwidth.

关 键 词：metasurface terahertz vortex beam Pancharatnam-Berry phase element conversion efficiency 

分 类 号：TB34[一般工业技术—材料科学与工程] O43[机械工程—光学工程]