Terahertz VO2 metasurface for multi-functional control of circular and linear polarizations via frequency and directional selectivity

Abstract A multifunctional VO 2 -based terahertz metasurface is proposed for modulating circular and linear polarizations with frequency and directional selectivity. By virtue of the phase transition mechanism of VO 2 , a hybrid structure composed of two dielectric layers and three gold-VO 2 composite layers is designed, which can achieve reconfigurable wavefront modulation. In the insulating state of VO 2 , the transmission and reflection phases of the metasurface can be flexibly manipulated, enabling cross-polarized dual-beam deflection with pronounced circular dichroism and co-polarized four-beam splitting would be realized at 1.2 THz and 1.27 THz, respectively. Conversely, in the metallic state, benefiting from independent control of x - and y -polarized waves of the metasurface, highly tunable reflection-based functionalities could be implemented around 2 THz, including vortex beam generation (OAM states l = −1 and l = 2), as well as lensing-based beam focusing and deflection. The ability to dynamically switch between distinct functionalities within a single platform highlights the potential of the metasurface for advanced terahertz photonic applications, such as reconfigurable beam steering, holography, and high-capacity wireless communication.