A proposal for a dual-band tunable plasmonic absorber using concentric-rings resonators and mono-layer graphene

A hybrid plasmonic absorber consisting of graphene and silica layers coated on a metal film with concentric-rings grooves is presented and numerically investigated in this paper. The proposed structure provides two absorption peaks at near-infrared region. The absorptivity of each peak can be tuned independently, by controlling the chemical potential of the graphene layer. Modulation of absorption per graphene Fermi energy about 85 %/eVand 51.25 %/eV can be obtained for the first and the second peaks, respectively. Simulation results also indicate that the absorption magnitudes of the peaks are independent of the polarization of the incident light. Hence, the proposed device can be utilized as a polarization insensitive optical modulator with two independently tunable bands. It is also shown that by splitting the silica filled rings (in this case, some parts of the silica inside the grooves are replaced by silver.), more individual peaks are appeared in the absorption spectrum of the device, whose absorptivity are dependent directly upon the positions of the silver gaps. Hence, the proposed device is a tunable light absorber with fully controllable absorption spectrum that can be used in a wide range of applications from photo-detectors to multi spectral tunable reflectors