Electrically tunable graphene nanoribbon metasurface absorbers for multispectral infrared detection

Graphene, an atomically thin carbon sheet with a two-dimensional hexagonal lattice structure, has attracted attention because of its unique electronic and optical properties. Graphene has two promising optical applications: graphene photodetectors that can operate at various wavelengths, and resistive graphene sheets whose optical constants can be configured via an applied voltage. In particular, graphene is a candidate for plasmonic metamaterial absorbers and emitters because of its electrical tunability. We previously demonstrated the concept of multilayer graphene-based metasurfaces. In the present study, we developed a more accurate theoretical calculation model for graphene, and theoretically investigated graphene nanoribbon metasurface absorbers (GNRMAs) for single- or multi-band infrared detection. The GNRMAs consist of a top periodic graphene nanoribbon layer formed on a dielectric layer, which contains another periodic graphene nanoribbon layer and is formed on a back-reflector. High wavelength-selective absorption can be achieved because of the surface plasmon resonance (SPR) of the graphene nanoribbons and Fabry- Perot resonance of the dielectric layer. The wavelength of graphene SPR is determined mainly by the width of the graphene nanoribbon. The absorption wavelength can be electrically tuned via the chemical potential of graphene, which can be controlled by the voltage applied to the graphene nanoribbons. The gap between the graphene nanoribbon layers determines whether the absorption is single-band or multi-band. This electrical tunability can be enhanced by independently controlling the voltage applied to each graphene nanoribbon layer. These results will contribute to the development of electrically tunable graphene-based multispectral infrared detectors and emitters.