Functionally switchable terahertz metasurface under linearly polarized and circularly polarized waves incidence

Currently, most reported terahertz metasurfaces can only respond to terahertz waves with a single polarization state (linearly polarized or circularly polarized wave), which poses a problem of limited degrees of freedom in regulation. Facing this challenging issue, we design a functionally switchable terahertz metasurface that can achieve independent control of linearly polarized and circularly polarized terahertz waves. It comprises a top layer photosensitive silicon and metal composite structure, a middle polyimide medium, and a bottom layer metal plate. By changing the conductivity of photosensitive silicon, the same metasurface structure can achieve two different functional mode switching under different polarization wave incidences, such as switching between beam splitting and vortex beam, switching between RCS and multi vortex beams, switching between single focus and multi focus. This structure provides a new idea for the flexible regulation of terahertz waves.