A high-efficiency wideband tunable polarization conversion metasurface assisted by the localized surface plasmon resonances

Abstract

Combined with the Dirac semimetals (DSMs), which is a new type of material and also called as 3D graphene, a tunable wideband terahertz polarization conversion metasurface based on an anisotropic configuration is studied, in which the DSMs 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. This characteristics are derived from the excitation of Localized Surface Plasmon Resonances (LSPRs) and the anisotropy of structure itself. When the incident angle changes in the range of 0°~40°, the high efficiency of wideband polarization conversion can be maintained. When it is greater than 40°, the wideband polarization conversion gradually changes to the dual-band or the multi-band conversion. Furthermore, it is found that in the process of increasing the Fermi energy of AlCuFe from 65 meV to 140 meV, the polarization conversion ratio can be maintained at a high level, and the conversion performance changes from single-band conversion to wideband conversion, and then to wideband conversion with wider band and single-band conversion with narrower band. At the same time, by discussing the metasurface combined with the different DSMs, it is concluded that the better the metallic property of DSMs is, the better the wideband polarization conversion performance of the corresponding metasurface is. At last, the numerical results are verified by the Multiple Interference Theory (MIT) based on the Fabry-Pérot-like resonance cavity.