Enhanced universal absorption of graphene in a Salisbury screen

Abstract

As an emerging optoelectronic material, graphene's universal absorption of about 2.3% over a broad frequency range from infrared to visible, as determined by its interband transition, presents both a new opportunity and a limitation. Here we report on a multifold enhancement of the absorption using a simple strategy, often referred to as the Salisbury screen. It consists of a graphene sheet on top of a SiO2 dielectric layer backed with a copper metallic reflector. For a monolayer graphene, peak absorptions of 9% at near normal incidence and 40% at near grazing angle are experimentally demonstrated in the near-infrared region, in good agreement with calculations using transfer matrix method. The resultant absorption enhancement suggests a great potential for graphene to be used in infrared optoelectronic components.