Dual-function tunable metasurface for polarization-insensitive electromagnetic induction transparency and dual-band absorption

In this paper, we propose a dual-operating mode metasurface based on graphene and vanadium dioxide (VO2), which can switch operating modes by changing the temperature. At room temperature (25(degrees)C), the metasurface can generates a polarization-insensitive electromagnetically induced transparency (EIT)-like effect that can be modulated by changing the Fermi energy level (E-F) of graphene (through adding external voltage). In addition, the theoretical results derived from the two-particle model are in good agreement with the simulation results based on the finite element method. At high temperature (68(degrees)C), the metasurface mode of operation can be changed to a dual-band absorber, providing absorption of 78.6% and 99.9% at 1.13 THz and 2.16 THz, respectively. Both absorption peaks can be dynamically tuned by changing the E-F of graphene. The metasurface is also simultaneously polarization insensitive and has a wide incidence angle. The proposed metasurface can be used as a slow light device with a maximum group delay of 0.5 ps at room temperature and as a refractive index sensor with a maximum sensitivity of 0.5 THz/RIU at high temperature. The designed metasurface offers a new way for designing multifunctional terahertz devices, slow light devices, and refractive index sensors.