Design of terahertz metamaterial absorbers with switchable absorption functions utilizing thermal and electrical dual-modulation strategies.

This work demonstrates a dual-functional tunable terahertz metamaterial absorber based on thermally controllable vanadium dioxide (VO) and electrically tunable graphene. The switchable absorption functions could be obtained in the same metamaterial, which consists of alternating stacked cross-cut graphene disks (CGDs) and VO square rings (VSRs) separated by an ultra-thin dielectric film placed on a continuous gold mirror. The metallic state of VSRs is the dominant factor for the broadband absorption function, resulting in a broadband absorption of 4.746 THz. Based on this, the Fermi energy level of CGDs increases to 0.7 eV, which could broaden the absorption bandwidth to 5.398 THz. When the VSRs are in the insulating state, CGDs dominate the absorption, and the suggested device switches to the dual-band absorption function. These two absorption peaks appear to be larger than 97% and their frequencies could be dynamically controlled by the Fermi energy level of CGDs. In addition to the excellent absorption characteristics of dynamic switching of two different functions, polarization insensitivity and large-angle tolerance are also advantages of this work, which could provide new insights and guidance for the study of dynamically tunable metamaterial absorbers.