Multi-frequency terahertz coding metasurfaces based on vanadium dioxide

s. Drawing upon the principles of digital coding metasurfaces, we propose the double-split ring resonators coding metasurface that can switch between different frequency bands with varying amplitudes. Under transverse-magnetic (TM) polarized terahertz wave incidence, the same metasurface meta-atom structure utilizes amplitude coding to achieve spatial imaging functionality. Due to limitations in device size and fabrication techniques, actively controlled coding metasurfaces in the terahertz frequency range are rare. In order to enhance the flexibility of terahertz coding metasurfaces, a phase-change material, vanadium dioxide (VO2), is introduced for active control within the metasurface structure. The imaging functionality can be switched by a single switching metasurface, achieved by the phase transition characteristics between the insulating and metallic states of VO2. Therefore, the designed coding metasurface, which is based on the influence of VO2 on amplitude, provides a new approach for flexible control of terahertz waves. It holds great prospects for significant applications in terahertz transmission, communication, and other emerging terahertz-related fields.