Tunable Graphene Metasurfaces with Bound States in the Continuum for High-Sensitivity Terahertz Sensing Applications

A high-sensitivity terahertz refractive index sensor has been designed, featuring active tunability and control via the states in the continuum. The sensor utilizes a symmetric graphene double split-ring structure. The resonance can be shifted to a high-Q leaky-mode resonance by tuning the chemical potential of graphene, exhibiting strong sensitivity to changes in the refractive index of the surrounding environment. The effect of the target molecule's thickness and refractive index on the transmission spectrum was investigated by numerical simulations based on the finite element approach. The graphene metasurface exhibits a Q factor of 76, a sensitivity of 268 GHz/RIU, and a figure of merit (FOM) of 15, indicating its applicability for use in highly sensitive photonic sensors operating in the terahertz frequency range.