Dual-band, Dynamically Tunable Plasmonic Metamaterial Absorbers Based on Graphene for Terahertz Frequencies

In this paper, a compact plasmonic metamaterial absorber for terahertz frequencies is proposed and simulated. The absorber is based on metamaterial graphene structures, and benefits from dynamically controllable properties of graphene. Through patterning graphene layers, plasmonic resonances are tailored to provide a dual band as well as an improved bandwidth absorption. Unit cell of the designed structure is made of four complementary square rings, on a thin grounded SiO2 layer of 5 µm thickness. Four splits are included in the square rings to provide continuity of graphene layer. Dual band absorption of 90% is provided, which frequency of peak absorption increases with increasing chemical potential of graphene layer. It is shown that with varying dimensions of the split rings an improved bandwidth absorber is also achieved, where absorption band increases with increasing graphene's chemical potential either. To better understand excitation of plasmonic resonances on the proposed structure, electric field distribution on the graphene layer as well as at the unit cell’s cross section is investigated and graphically demonstrated. Dependence of absorption on incidence and polarization angles of the incoming wave is studied and also graphically presented.