Tunable Nearly Perfect Absorber Based on Graphene Metamaterials at the Mid-Infrared Region

We propose the idea of a tunable nearly perfect absorber based on graphene metamaterial consisting of a periodically arranged graphene ribbons (bright mode) and the inverse slots in the thin graphene film (dark mode). The absorption peak has a narrow linewidth of 160 nm and the absorbance approaching to 97.12%. The fascinating absorption feature not merely due to plasmonically induced absorption arising from destructive interference between the bright and dark mode but also the metamaterial absorption. We have testified numerically that the electric fields are highly confined inside the slot. The mid-IR absorption spectrum can be dynamically tuned by a small change in the chemical potential of graphene, in addition to varying geometrical parameters. Our paper considers a situation that represents an intermediate plasmonic coupling regime, between near-field and far-field coupling. Such absorber possesses potential for applications in mid-IR nanophotonic devices.