A tunable graphene-based refractive index sensor for THz bio-sensing applications

In this paper, a sensitive graphene-based terahertz sensor is proposed. The proposed sensor consists of a patterned graphene geometry on top of a SiO₂ layer. To eliminate the transmission of proposed structure, a bottom gold layer is utilized. Moreover, a Polysillicon layer is located at a near distance under the graphene layer to provide all practical issues encountered with biasing the embedded graphene layer. According to utilized optimization procedure and resulting sensing performance, the designed sensor is sensitive to surrounding medium and can be used as a refractive index sensor with linear performance. The presented structure is based on enhancing electromagnetic fields confinement. This sensing mechanism can be used in biomedical applications for detecting different components of body fluids including blood glucose. Moreover, the proposed sensor can be used to distinguish between normal and cancerous cells. The obtained performance is investigated considering three different cells, namely Hela, basal, and MDA-MB-231 (breast cells). The simulation results show sensitivities of 3 and 3.23 THz/RIU together with figure of merits of 15 and 16.8 RIU-1 for cancer cells and blood components, respectively. The proposed structure results in an almost linear relation between resonance frequency shift and refractive index changes, which is an important property demanded by refractive index sensors. The proposed sensor benefits from simple structure resulting to an easy fabrication process.