Spin-decoupled metasurface based on vanadium dioxide for four-channel terahertz wavefront control

Here, the terahertz reflective multilayer metasurface incorporating vanadium dioxide phase-change materials is studied. By integrating the properties of phase change with spin-decoupling mechanisms, dynamic wavefront control across four channels is achieved. The metasurface is arranged with three layers of metal/vanadium dioxide and two layers of dielectric materials in an alternating configuration. When vanadium dioxide is in its metallic state, the intermediate layer can be treated as a metal plate, allowing resonance generation from the top C-shaped ring. Conversely, when vanadium dioxide transitions to an insulating state, the structure at the top layer becomes disordered. The resonant characteristics are exhibited by the intermediate layer through its metallic C-shaped ring. Based on the theories of the geometric phase and the transmission phase, spin-decoupled wavefront control was achieved by optimizing the structural parameters of each resonant ring. The proposed metasurface utilizes a dual-degree-of-freedom control mechanism, and four-channel beam steering is independently manipulated through temperature variations and spin polarization of incident waves. Based on this architecture, we have successfully designed a tunable metalens featuring four distinct focal lengths, along with a dynamic holographic imaging system capable of operating across four channels. Simulation results indicate that our proposed four-channel metasurface effectively fulfills its intended functionality while maintaining minimal crosstalk between channels. The proposed metasurface holds significant potential for applications in dynamic imaging, wireless communication, and other fields.