3-bit reconfigurable THz metasurface based on structured light illumination for vortex beams and holographic imaging

Metasurfaces have attracted widespread attention due to their excellent control ability of terahertz wavefronts. Terahertz metasurfaces have made rapid progress in areas such as biological detection, high-speed communication, and imaging. However, terahertz metasurfaces currently have a single function, and the primary goal of this research is to create a reconfigurable and multifunctional terahertz metasurface. In this work, we designed a novel eight-gaps-splits-ring resonator (EGSRR). The EGSRR is filled with photosensitive semiconductor material, and the metasurface unit's amplitude-phase characteristics are controlled by different encodings of structured light. Finally, under the incidence of right-handed circularly polarized (RCP) waves, 3-bit phase encoding of its reflected wave with cross-polarization is achieved. To verify the ability of metasurface to control terahertz wavefronts, the 3-bit metasurface units are assembled into an array to achieve different-order vortex beams and reconfigurable holographic images. The novel optically controlled reconfigurable metasurface not only has promising applications in generating vortex beams and holographic imaging, but it also represents a novel approach to designing multifunctional and programmable terahertz metamaterials.