A Tunable Ultrabroadband Ultrathin Terahertz Absorber Using Graphene Stacks

The concept of an ultrabroadband ultrathin terahertz (THz) absorber based on graphene stacks is presented. To realize dynamic tuning of the absorption band, we combine two concentric circular split-rings encircling a split circular resonator with graphene stacks embedded in a SiO2dielectric. The transmission line model for the proposed absorber has been theoretically investigated via the effective-medium method. The simulated results show a 0.9 absorption coefficient over the range 2.58-3.56 THz, and the central frequency of the absorption band can be tuned without absorption reduction by changing the gate voltage on the graphene stack. Furthermore, the absorption performance exhibits insensitivity to the angle of incidence. Thus, the proposed absorber is very promising for various THz applications.