Graphene-Based Metamaterial for On-Demand Spectral Absorption Tailoring in the Mid-Infrared

We propose a graphene-based metamaterial to achieve electrically-tunable spectral absorptivity in the infrared. The metamaterial comprises of a periodic array of coupled metal-insulator-metal resonator pairs. Each of these has an electrically tunable resonance wavelength owing to the presence of graphene. The structural parameters of the two resonators in each unit cell are chosen to implement a dark-bright mode coupling scheme in the context of temporal coupled-mode theory. The relative spectral position, and in turn the coupling between consecutive resonators, can be tuned by modulating the Fermi energy of graphene. Using our metamaterial absorber, we demonstrate the ability to modulate the amplitude of spectral features in the infrared. The spectral response of the metamaterial can be tuned from single-peaked to double-peaked absorption or vice versa by tuning the bright resonator towards or away from the dark resonator, respectively. Our results thus suggest the possibility of achieving tunable multi-band absorption using metamaterials composed of multiple coupled resonators. This ability to dynamically modulate spectral absorptivity can potentially benefit several applications such as infrared imaging and thermal management.