Tunable Dual-Band Perfect Absorber Based on L-Shaped Graphene Resonator

Abstract

We propose and investigate a tunable dual-band perfect absorber consisting of double asymmetric L-shaped graphene resonators (LSGRs) and a metal ground plane spaced by a thin SiO ₂ dielectric layer. The numerical results reveal that the presented absorber expresses two resonance peaks in the mid-infrared region, where their absorption coefficients are on average larger than 98.77%. The electromagnetic eigenmode resonances of a single LSGR can induce two absorption peaks with values about 50%. Assembling two LSGRs together, the absorptivity can reach up to almost 100% due to the plasmonic couplings. In addition, the design has the ability to tune the working wavelengths of the absorption peaks within a large wavelength range by changing geometric parameters and the Fermi level of the graphene layer. In addition, wavelength-selective dual-band perfect absorption peaks can be achieved in the wavelength range of interest by merely adjusting the polarization angle. This letter presents a unique route toward the realization of nanophotonic devices and has potential applications in filtering, sensing, and detecting.