Bifunctional Graphene-Graphite-Based THz Wave Metasurface Absorber for Sensing and Electromagnetic Shielding

The integration of various functions on a miniaturized device can reduce the complexity of the optical system and is therefore one of the emerging trends in the nanophotonic field. In this paper, a simple polarization-insensitive bifunctional metasurface absorber is designed for sensing as well as electromagnetic wave shielding applications. The multilayer (graphene-SiO2-graphite-SiO2-graphite) meta-atom of the designed metasurface consists of an annular graphite disk sandwiched between two SiO2 layers with graphene split ring resonator at the top of the meta-atom. The proposed device behaves like a wideband absorber in the frequency range of 2.37-9.37 THz and exhibits a high fractional bandwidth of 119.25% for absorptance greater than 90% when the graphene chemical potential is 0 eV. The shielding effectiveness of the wide band absorber has been found more than 40 dB in the desired frequency range which showed its potential for use in electromagnetic shielding. Furthermore, the wideband absorber turns into a narrow-band absorber when the chemical potential is tuned to 0.9 eV. The reliability of the narrow band absorber is determined for the sensing applications and a high sensitivity of 2.17 THz/RIU has been observed for the device. The absorber response has been verified by the transmission line equivalent circuit model.