Active tuning of terahertz EIT in a graphene-integrated metasurface for slow light and sensing applications

Dynamic tuning of terahertz (THz) electromagnetically induced transparency (EIT) is of great significance for THz applications in slow light, switching, and sensing. In this study, we present a THz EIT metasurface that utilizes a combination of circular and U-shaped ring resonators (CRR and USRR) based on bright-quasi-dark mode coupling. Different from the conventional methods that only focus on the modulation of the EIT transparent window, this work achieves active control with both the EIT window and the nearby resonance after integration with graphene, which extends more THz modulation channels. The simulation results show that the hybrid metasurface has a modulation depth of 81.4% at the EIT window, and the resonance adjacent to the EIT peak achieves a remarkable modulation depth of 97.5%. In addition, the proposed EIT metasurface is capable of refractive index sensing with high sensitivity. This study not only elucidates the universal interaction between graphene and metallic metasurfaces but also paves the way for the development of compact and active THz slow light and sensor devices.