Tunable metasurfaces for independent control of linearly and circularly polarized terahertz waves

Metasurfaces provide an extraordinary way to control electromagnetic waves by abrupt change of optical properties within an optically thin interface. In this paper, by introducing vanadium dioxide (VO₂) into the metasurface, efficient tunable terahertz phase modulation is designed to realize independent control of linearly and circularly polarized terahertz waves. The working resonator of the metasurface can be adjustable by controlling the temperature of VO₂, resulting in the tunable function between resonant phase for linearly polarized waves and Pancharatnam-Berry phase for circularly polarized waves. As a proof of concept, two metasurfaces are designed for integrating two distinct functionalities in one structure, i.e. 1-bit metasurface switched between the abnormal THz deflector and the THz scatter and 3-bit metasurface switched between the vortex THz transmitter and the THz focusing mirror. The proposed tunable resonator structure provides a flexible way for extending the functionality of metadevice, which has a great potential value in integrated optics and wearable optics.