Dual-band tunable electromagnetically induced transparent graphene-based terahertz metamaterials with two coupling modes triggered by only two resonators

Abstract A novel design method, using only two graphene-based resonators formed by a circular split ring and a finger-circle ring, for achieving dual-band tunable terahertz electromagnetically induced transparent (EIT) is proposed. The structure could simultaneously excite two different coupling mechanisms, namely bright-bright mode coupling and bright-dark mode coupling, thereby generating two efficient transparent peaks with transmittance intensities of 84% and 86%, respectively. Surface current and electric field distributions are given to well explain the physical mechanisms of the dual-band EIT effect. The parameter changes and Fermi level variations of these two graphene sub-resonators have a significant regulatory effect on these two transparent peaks, with the maximum modulation depth of greater than 96%, and synchronous triple-frequency and asynchronous five-frequency switching could be further achieved by precisely controlling the Fermi energy levels. The proposed dual-band tunable terahertz graphene-based EIT metamaterial could be used for refractive index sensing, with a sensing sensitivity of up to 262.4 GHz/RIU. Our research may open a new avenue for designing multi-band EIT metamaterials, showcasing significant potential for advancing applications in optical modulators, slow light devices, and sensing.