Bifunctional terahertz sensor based on tunable graphene metamaterial absorber

In this paper, we propose a tunable graphene metamaterial absorber (TGMA) as a bifunctional terahertz sensor. The TGMA can excite one peak with a maximum absorption of 99.9%, and the physical mechanism of the absorption is explained by introducing the coupled mode theory. The simulation results show that the absorptivity can be dynamically adjusted by changing the chemical potential of graphene. The TGMA exhibits excellent absorption performance under a wide range of incident angles for transverse-electric (TE) and transverse-magnetic (TM) polarizations, respectively. More importantly, the TGMA can operate as a temperature sensor with a sensitivity of 6.2 GHz/K and a refractive index sensor with a sensitivity of 1.43 THz/RIU in both TE and TM polarizations under normal incidence. In addition, the effect of polarization angle on the sensing sensitivity is investigated. The simulation results indicate that the sensitivity is completely independent of the polarization angle for temperature and refractive index sensing, respectively. In a word, the demonstration of this bifunctional terahertz sensor offers an alternative solution for developing multifunctional metamaterial devices in the THz range.