Graphene-based tunable multi-band metamaterial polarization-insensitive absorber for terahertz applications

This paper presents a graphene-based tunable polarization-insensitive metamaterial absorber (MMA) at terahertz (THz) frequencies. The absorber consists of top patterned gold (Au) layer followed by single layer of graphene, dielectric spacer, and Au layer at bottom. The proposed MMA demonstrates multi-band absorption with the characteristics of both broad- and dual-band absorption by optimizing dimensions (parametric analysis). Broad-band absorption reaches over 90% for the range of 4.57-6.45 THz with the relative absorption bandwidth of 34%, and the absorption peak at 6.86 and 7.20 THz having 98.9 and 95.2% absorption. The normalized impedance and constitutive electromagnetic parameters of the MMA are calculated using the Nicolson-Ross-Weir (NRW) method to validate the absorption rate. Furthermore, proposed absorber is polarization-insensitive upto 90 degrees for transverse electric wave. The tunable characteristic of MMA is achieved by tuning the Fermi energy of graphene with the application of bias voltage. Accordingly, the proposed multi- and broad-band absorbers find its potential applications in spectroscopy detection, imaging, and sensing.