Terahertz refractive index sensor based on tunable patterned graphene absorber

Abstract

We introduce an ultrasensitive refractive-index sensor based on a patterned graphene dual-band absorber operating in the terahertz band. COMSOL Multiphysics software was employed to model and quantitatively assess the suggested micro-nano structure. The structure exhibits two perfect absorption peaks in the 1–9 THz band with theoretical absorptions of 99.4 % and 99.4 %. According to the properties of graphene, the positions of the absorption peaks can be adjusted using the applied bias voltage. Owing to the high symmetry of the proposed structure, it is insensitive to polarization and incident angle variations. Moreover, this study explored the effect of different parameters on the absorption peak by varying the structural parameters. Based on the simulation results, the refractive index sensor has a maximum sensitivity of 3 THz/RIU with a figure of merit (FOM) and can detect small refractive index changes. Therefore, we believe that this structure has promising applications in marine refractive index change determination. • The structure exhibits two perfect absorption peaks in the 1–9 THz band. • The positions of the absorption peaks can be adjusted using the applied bias voltage. • It is insensitive to changes in polarization and angle of incidence. • It has better sensitivity and FOM than most sensors of the same type.