A high-efficiency wideband tunable polarization conversion metasurface assisted by localized surface plasmon resonances
Authors: Zhang Jian-Guo , Yi Zao , Kang Yong-Qiang , Ren Hao , Wang Wen-Yan , Zhou Jing-Fan , Hao Hui-Zhen , Chang Hui-Dong , Gao Ying-Hao , Chen Ya-Hui , Li Yan-Na ,   Department of Physics and Electronic Engineering, Jinzhong University, Jinzhong 030619, China,   School of Science, Southwest University of Science and Technology, Mianyang 621010, China,   School of Physical Science and Electronics, Shanxi Datong University, Datong 037009, China,   Institute of Theoretical Physics, State Key Laboratory of Quantum Optics and Quantum Optics Devices,Shanxi University, Taiyuan 030006, China,   College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, China,   Information Communication Branch Company, State Grid Shanxi Electric Power Company, Taiyuan 030001, China,   Department of Physics, College of Basic Medical Sciences, Army Medical University, Chongqing 400038, China
Published: June 2022

Combined with the Dirac semimetals (DSMs), which is a new type of material and also called 3D graphene, a tunable wideband terahertz polarization conversion metasurface based on an anisotropic configuration is studied, in which the DSM wire array is beneficial to the regulation of Fermi energy. The results show that the metasurface can realize wideband and highly efficient polarization conversion, and has the property of half wave plate at the resonant modes. These characteristics are derived from the excitation of localized surface plasmon resonance (LSPR) and the anisotropy of structure itself. When the incident angle changes in a range of <inline-formula><tex-math id="M2">\begin{document}$0^\circ $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220288_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220288_M2.png"/></alternatives></inline-formula>–<inline-formula><tex-math id="M3">\begin{document}$40^\circ $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220288_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220288_M3.png"/></alternatives></inline-formula>, the high efficiency of wideband polarization conversion can be maintained. When it is greater than <inline-formula><tex-math id="M4">\begin{document}$40^\circ $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220288_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220288_M4.png"/></alternatives></inline-formula>, the wideband polarization conversion gradually changes into the dual-band conversion or the multi-band conversion. Furthermore, it is found that in the process of increasing the Fermi energy of AlCuFe from 65 to 140 meV, the polarization conversion ratio can be maintained at a high level, and the conversion performance changes from single-band conversion into wideband conversion, and then into wideband conversion with wider band and single-band conversion with narrower band. At the same time, by discussing the metasurface combined with the different DSM, it is concluded that the better the metallic property of DSMs, the better the wideband polarization conversion performance of the corresponding metasurface is. Finally, the numerical results are verified by the multiple interference theory based on the Fabry-Pérot-like resonance cavity.