Ultra-broadband tunable terahertz absorber of graphene and hierarchical plasmonic metamaterials

In this study, a novel tunable, ultra-broadband terahertz MPA of atomically thin monolayer graphene and hierarchically structured plasmonic metamaterials is proposed and studied. The metamaterial MPA comprises alternating T-shaped gold bars, a dielectric layaer and a graphene layer on the bottom gold layer. These near-perfect absorbers have an average absorption of nearly 90% over an ultra-broad frequency range from 21.8 to 40 THz (with a highest absorption of 99.1% at 25.5 THz), the bandwith is as high as 18.2 THz. The effects of geometrical parameters on the absorption spectra are analyzed quantitatively. The modulation of the absorption window by tuning the Femi level of graphene is investigated, and the potential applications are discussed.