Multi-functional High-Efficiency Terahertz Polarization Converter Based on Graphene Metasurface

In this paper, we propose a multi-functional and switchable broadband polarization converter in the terahertz (THz) band, which can switch between linear-to-linear polarization conversion and linear-to-circular polarization conversion modes via artificially tuning the Fermi energy level of graphene (Ef). When Ef is set to 0 eV, the polarization converter can transform linear polarized (LP) wave into its cross-polarized counterpart within the 0.53–1.41 THz range, exhibiting a remarkable relative bandwidth of 91%. Conversely, when Ef is set to 1 eV, the polarization converter can convert LP wave into right-handed circularly polarized (RCP) wave within the 0.7–1.6 THz band and left-handed circularly polarized (LCP) wave within the 1.8–3.1 THz band, with relative bandwidths of 78% and 53%, respectively. With these exceptional capabilities, this graphene metasurface-based polarization converter holds significant promise for a wide array of THz applications, including optical switches, modulators, communication systems, and sensors.