A reconfigurable terahertz polarization converter based on metal-graphene hybrid metasurface

A metal-graphene hybrid metasurface polarization converter is designed in this Letter. The unit cell of the hybrid metasurface is composed of a butterfly-shaped structure whose branches are connected by multi-layer graphene sheets. The proposed device can be reconfigured from linear-to-circular polarization to cross-polarization by changing the Fermi energy of graphene. The simulation results show that for three-layer graphene, the device acts as a linear-to-circular polarization converter when E-F = 0 eV and switches to a cross-polarization converter when E-F = 0.5 eV. Compared with single-layer graphene, the device with three-layer graphene can maintain the cross-polarization conversion performance under low Fermi energy. Furthermore, two equivalent circuits in the x and y directions are developed to understand the working mechanism of the device.