Analytical design of tunable disk, patch and ribbon-patterned graphene absorbers in the terahertz spectrum

Three topologies of periodic arrays of graphene consisting of disk, ribbon, and patch for realizing terahertz absorbers are proposed and analyzed in this work. The circuit model was utilized in the design of the absorbers. The main goal was to implement tunable bandwidth in terahertz absorbers by changing the chemical potential in graphene. In this respect, a novel method for calculating the relaxation time which is related to chemical potential of graphene is presented, of importance in the absorber design process. Absorbers have been designed and simulated in central frequencies of 8, 10, and 12 terahertz with bandwidths of 0.5, 0.8, and 1 THz at 95% absorption. The absorbers' key advantages are their simple structure (consisting of graphene arrays, dielectric spacer, and a bottom metal layer), bandwidth tuning via a backed-gate voltage of graphene, their independence of input wave polarization – in the case of disk and patch shape graphene arrays - and their extremely low sensitivity to angle of incidence.