Improving the absorption of a plasmonic absorber using a single layer of graphene at telecommunication wavelengths

In this paper, a plasmonic absorber composed of a single layer of graphene over a metal film and separated by a 5 nm thin silica layer has been proposed. The metal film consists of two L-shaped grooves and a ring groove between the silver rods, and surrounding the silver cylindrical ring is a square of silica. The absorption of the proposed structure without the graphene is 0.85, and it is enhanced to 0.98 with a single layer of graphene in the near-infrared region. This absorption enhancement is because of the light and graphene interaction, which is reinforced by the localized surface plasmon resonance in the grooves. Our structure has the ability to control the absorption wavelength by changing the grooves depth and the L-shaped arms length. Also, the effects of the chemical potential and the thicknesses of the graphene and silica layer on the absorption spectrum have been investigated. Furthermore, we have shown that the proposed absorber can be dual-band, if so desired, for optoelectronic components.