中国物理B ›› 2021, Vol. 30 ›› Issue (5): 58103-058103.doi: 10.1088/1674-1056/abd75c

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

Wenyu Li(李文宇)1,2, Guozhong Zhao(赵国忠)1,†, Tianhua Meng(孟田华)2, Ran Sun(孙然)1, and Jiaoyan Guo(郭姣艳)1   

  1. 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
  • 收稿日期:2020-10-20 修回日期:2020-12-02 接受日期:2020-12-30 出版日期:2021-05-14 发布日期:2021-05-14
  • 通讯作者: Guozhong Zhao E-mail:guozhong-zhao@cnu.edu.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 62071312), the Important R&D Projects of Shanxi Province, China (Grant No. 201803D121083), and the Shanxi Scholarship Council (Grant No. 2020-135).

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

Wenyu Li(李文宇)1,2, Guozhong Zhao(赵国忠)1,†, Tianhua Meng(孟田华)2, Ran Sun(孙然)1, and Jiaoyan Guo(郭姣艳)1   

  1. 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
  • Received:2020-10-20 Revised:2020-12-02 Accepted:2020-12-30 Online:2021-05-14 Published:2021-05-14
  • Contact: Guozhong Zhao E-mail:guozhong-zhao@cnu.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 62071312), the Important R&D Projects of Shanxi Province, China (Grant No. 201803D121083), and 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 $l\hbar$. The $l$ values change from $\pm 1$ to $\pm 5$, 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

Abstract: 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 $l\hbar$. The $l$ values change from $\pm 1$ to $\pm 5$, 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.

Key words: metasurface, terahertz vortex beam, Pancharatnam-Berry phase element, conversion efficiency

中图分类号:  (Metamaterials for chiral, bianisotropic and other complex media)

  • 81.05.Xj
74.25.Uv (Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)) 03.65.Vf (Phases: geometric; dynamic or topological) 07.05.Tp (Computer modeling and simulation)