Anisotropic vanadium dioxide-based metasurfaces for polarization-multiplexed holograms in the terahertz region

Holography plays a significant role in optical research and has been utilized in numerous applications. Metasurface holograms are attracting more and more attention with the advancement of their efficient wavefront reshaping. However, the realization of multi-channel holograms and dynamic switching of them still remain challenging in the terahertz band. In this paper, anisotropic vanadium dioxide (VO2) metasurfaces are used to realize four-channel holograms at 1.5 THz. It is assembled by a set of VO2 meta-atoms with independent phase control for different channels. Depending on the polarization of incident wave and the state of VO2, four channels are independently selected. After optimization to eliminate crosstalk between top and bottom layers, two holograms are projected under x- and y-polarized incidences when VO2 is metallic. Similarly, two additional holograms are achieved as VO2 is insulating. As a novel solution to terahertz multi-channel holography, this work may be applied to compact optical system and high-volume optical encryption.