A Vanadium Dioxide Film-Based Polarization Switchable Sand-Clock Metasurface for THz Wireless Communications

Abstract

This paper introduces a polarization-switchable metasurface (MTS) utilizing a sand-clock-shaped unit cell integrated with vanadium dioxide (VO2) for terahertz (THz) communication. The structure comprises a metallic sand-clock resonator, a VO2 phase-change layer between dielectric substrates, and a continuous gold ground plane. The dynamic conductivity transition of VO2 between its insulating state and metallic state allows for controllable polarization state reflection. In the insulating state (<inline-formula> <tex-math notation="LaTeX">$\sigma = 200~\mathrm {S/m}$ </tex-math></inline-formula>), it achieves over 88% linear-to-linear (LP-LP) polarization conversion (1.08-1.80 THz), while in the metallic state (<inline-formula> <tex-math notation="LaTeX">$\sigma = 2 \times 10^{5}~\mathrm {S/m}$ </tex-math></inline-formula>), it enables linear-to-circular (LP-CP) conversion with a circularly polarized wave having an axial ratio below 3 dB (1.21-1.53 THz), ellipticity approaching unity (−1), and efficiency exceeding 95%. The study elucidates the phase relationship modification due to VO2 phase transition, positioning the proposed metasurface as a viable candidate for intelligent reflecting surfaces and future adaptive THz communication systems.