Bidirectional ultrawideband switchable multifunctional metasurface based on photosensitive silicon and VO₂

Abstract Multifunctional integration and dynamic reconfiguration of electromagnetic devices in the terahertz band is a current research hotspot in the frontier field. In this paper, a bi-directional terahertz wavefront manipulation multifunctional metasurface based on photosensitive silicon (photosensitive silicon) and vanadium dioxide (VO2 ) phase transition materials is proposed to realize ultra-wideband absorption, orbital angular momentum (OAM) beam generation, radar scattering cross-section (RCS) reduction and The dynamic switching of the four functional modes of ultra-broadband polarization conversion is achieved. When the linearly polarized terahertz wave is incident vertically along the -z direction, and the photosensitive silicon and VO2 are in the metallic phase, the electromagnetic wave is strongly absorbed in the frequency band of 6.68-16.88 THz, and the relative bandwidth can reach 86.58%. When the circularly polarized terahertz wave is incident along the -z direction and the photosensitive silicon is in the metallic phase, the metasurface can produce a high-purity vortex beam with an effective reduction of the radar scattering cross-section through the design of the cell sequence with full coverage of the 2π phase. Meanwhile, when the linearly polarized wave is incident along the + z direction and the VO2 is in metallic phase, the polarization conversion ratio (PCR) is close to 1 and the relative bandwidth is over 80% in the 4.6-10.78 THz band. The ultra-surface is characterized by fast multi-mode switching, excellent broadband performance, compact structure, and its dynamic reconfiguration mechanism based on phasechange materials provides a universal idea for the design of reconfigurable electromagnetic devices, which has a broad application prospect in the future in the fields of intelligent networking of terahertz high-speed communication networks, integrated design of multimodal electromagnetic stealth systems, and high-sensitivity intelligent sensing arrays.