A Novel THz Half-Wave Polarization Converter for Cross-Polarization Conversions of Both Linear and Circular Polarizations and Polarization Conversion Ratio Regulating by Graphene

Polarization converter is firstly proposed with the functions of simultaneously converting a linear polarization (LP) and a circular polarization (CP) to its corresponding cross polarizations, and polarization conversion ratio (PCR) of the converter with graphene strips is also controllable in this paper. A reflectiontype converter is designed based on a metasurface in the terahertz region. It consists of periodic unit cells with strip-loaded half elliptical rings, a dielectric spacer layer, and a gold layer. The converter with PCR regulating also includes graphene strips on the gold layer. Both the LP and CP incidences can be converted into their cross-polarized ones with good PCR performances in a 2-THz band (2.1-2.9 THz, 32%). The graphene strips on the gold layer that disturbs the gold layer currents can regulate the PCR, typically from 2% to 98% for LP illuminations and from 60% to 98% for CP illuminations by adjusting the chemical potential μ _c of the graphene. Also, the physical mechanisms of the polarization conversions were investigated.