VO 2 -tunable terahertz metasurface for broadband linear-to-linear polarization conversion

This paper presents a tunable terahertz metasurface based on vanadium dioxide (VO 2 ), in which broadband linear-to-linear tunable polarization conversion is achieved by regulating the conductivity of VO 2 . The unit cell consists of five layers arranged sequentially, including a gold backplane, a polyimide dielectric spacer, a thin VO 2 film, a second polyimide layer, and a hybrid metal–VO 2 patterned top layer. When VO 2 is in the insulating state, simulation results demonstrate that the proposed metasurface realize polarization conversion ratio (PCR) exceeds 90% from 3.50 to 8.00 THz under linear-to-linear polarized wave. As the conductivity of VO 2 changes, the polarization conversion response is flexibly tuned from broadband behavior to dual-band and triple-band high-efficiency conversion. The Jones-vector analysis, electric- and magnetic-field distributions, and surface-current distributions show that the broadband response arises from the overlap and coupling of multiple electric and magnetic resonant modes. Owing to its broadband conversion performance and conductivity-controlled tunability, the proposed metasurface shows promising potential for applications in terahertz communications, imaging and wavefront manipulation.