Graphene-based metamaterial absorber for refractive index sensing applications in terahertz band

A tunable triple-band absorption-based refractive index (RI) sensor with a combined graphene pattern in the terahertz (THz) band has been proposed in this paper. The proposed sensor has the potential to be used for biosensing applications. Graphene split-ring and patch resonators are combined and used as a metamaterial element. The combined array structures are used to localize the incident electromagnetic field. In the proposed absorber, using the surface plasmon resonance (SPR) phenomenon of graphene, three narrow absorption peaks arise at frequencies of 4.66 THz, 6.035 THz, and 8.72 THz with absorption efficiencies of 99.2 %, 99 %, and 89 %, respectively. The overall performance and the position of the resonance frequencies are adjustable using an external DC-bias voltage applied to the graphene. The RI sensor is based on detecting changes in the RI of the sample under test, has a maximum sensitivity, Q-factor, and figure-of-merit (FoM) of 1791 (GHz/RIU), 32.354 and 7.046 RIU−1, respectively. Therefore, according to the mentioned features, which are obtained based on numerical simulations, the designed sensor is a good choice for medical and biosensing applications.