A graphene-based dual-band THz absorber design exploiting the impedance-matching concept

A THz wave absorber is designed by exploiting a unique concept and method. Three layers including dielectric and graphene patterns are incorporated on top of a thick gold surface to ensure zero transmission of THz waves through the structure. A favorable dual-bias scheme is used for the periodic arrays of graphene ribbons in the first layer, while the second layer consists of periodic arrays of graphene disks. Also, a top layer consisting of a continuous graphene sheet is used to enhance the overall absorption. All the components are modeled via a circuit model approach developed based on passive circuit elements. This leads to an explicit impedance calculation for the structure, paving the way to fully predict the device behavior. By applying impedance-matching theory, the structural parameters are tuned to obtain perfect dual-band absorption at frequencies of 5.5 and 8.5 THz. Extensive simulations verify the robustness of the structure versus variations in its geometrical parameters, while a great ability to tune the absorption peaks is achieved via variation of the chemical potentials. Such robust and tunable absorbers are attractive for the design of optical sensors, detectors, and modulators.