Multi-functional dual-band polarization converter based on graphene and vanadium dioxide metasurfaces

In this work, a dual-band, functionally switchable terahertz polarization converter is designed based on patterned graphene and rectangular vanadium dioxide (VO2). By using FDTD solution, the functions and properties of the polarization converter are investigated. The converter can perform simultaneously multiple functions, including converting incident linearly polarized electromagnetic waves into its cross-polarization (LTL) or circular polarization (LTC) waves. By adjusting the Fermi level of graphene and the conductivity of VO2, the polarization conversion rate (PCR) of LTL and the ellipticity χ of LTC can be dynamically tuned, and the LTL conversion function can be switched to the LTC conversion function at the same operating frequency. In addition, the physical mechanism of the polarization converter is investigated by analyzing the magnetic field and current distribution of the converter. In polarization conversion (PC) process, the rectangular holes pattern and rectangular VO2 on graphene sheet play a crucial role. Plasmon resonance interacting with Fabry-Perot resonance realizes the PC function. The proposed polarization converter can be used in communication, sensing, and detection fields.