Greatly enhanced ultrabroadband light absorption by monolayer graphene

We demonstrate greatly enhanced light absorption by monolayer graphene over a broad spectral range, from visible to near IR, based on the attenuated total reflection. In the experiment, graphene is sandwiched between two dielectric media referred to as superstrate and substrate. Based on numerical calculation and experimental results, the closer the refractive indices of the superstrate and the substrate are, the higher the absorption of graphene is. The light absorption of monolayer graphene up to 42.7% is experimentally achieved.