Theoretical research of a dual-function terahertz metasurface based on graphene and VO ₂ : from electromagnetically induced transparency to multi-band absorption

In this study, a tunable terahertz metasurface is designed to regulate electromagnetically induced transparent windows and absorbers utilizing graphene and vanadium dioxide. The cell structure features periodically arranged graphene composed of two square rings, which facilitates electromagnetically induced transparency, resulting in an 82.7% transparent window at 2.65 THz. By adjusting the graphene Fermi energy level, the operational frequency of the transparent window can be dynamically modulated, achieving a maximum group delay of 2.81 ps. The three-level principle and electric field distribution are employed to elucidate the physical mechanism, and the simulation results are validated using the dual oscillator model. Increasing the operating temperature harnesses the phase transition characteristics of vanadium dioxide, allowing it to exhibit metallic properties and effecting the transformation from electromagnetically induced transparency to a three-band narrowband absorber. Absorption peaks of 99.7%, 89.5%, and 86.7% were observed at 1.76, 2.86, and 3.99 THz, respectively. Additionally, we investigated the sensitivity of the absorber to variations in the refractive index of the medium, achieving a maximum sensitivity of 0.65 THz/RIU. Given these exceptional properties, the metasurface holds significant potential for applications in slow-light devices, absorbers, sensors, and multifunctional devices.