Tunable terahertz perfect absorber using vanadium dioxide-based metamaterial for sensing applications

We present a design of terahertz (THz) perfect absorber (TPA) based on thermotropic phase change material vanadium dioxide (VO2). The TPA device is composed of a metal-insulator-metal (MIM) structure, and the top metal layer is tailored to form an inner VO2-based disk structure and an outer Au-based connected-ring structure. The electromagnetic responses of TPA device with different geometric parameters operated in the THz band are investigated, and the perfect absorption is achieved at 2.51 THz. Furthermore, by increasing the temperature applied on VO2 from 313 K to 363 K with an interval of 10 K, the disk structure changes from an insulating phase to a metallic phase. There is an extra resonance mode arises, which induces the resonance of TPA device can be switched from single to dual. Additionally, being exposed to an ambient environment with different refraction indices, the TPA device shows a high-efficient sensing capability with a sensitivity of up to 398 GHz per refractive index unit (RIU). These results indicate that the proposed design opens an avenue for tunable absorbers, actively controllable switches, THz logic devices, and high-efficiency sensors.