Terahertz broadband tunable reflective cross-polarization convertor based on complementary cross-shaped graphene metasurface

In this work, a broadband tunable reflective polarization convertor using a single layer complementary-cross-shaped (CCS) graphene metasurface was proposed and investigated numerically in terahertz (THz) region. The electric property of CCS graphene could be flexibly tuned through the Fermi energy level (Ef). When Ef = 0.9 eV, the proposed graphene metasurface can realize a relative high polarization conversion ratio (PCR) of over 80% from 2.15 THz to 4 THz with a relative bandwidth of 60.16%. Furthermore, the PCR peak can reach up to as high as 99%, 99.5% and 91.5% at 2.4 THz, 3.4 THz and 3.96 THz, respectively. The physical origins of this polarization conversion properties are turned out to be supported by field distributions and Fabry-Perot interference theory. Furthermore, the broadband polarization conversion properties will be regulated by varying the Fermi energy level.