Visible to near-infrared coherent perfect absorption in monolayer graphene

We show numerically and theoretically that coherent perfect absorption can be achieved in suspended monolayer graphene with ultra-broad bandwidth from visible to near-infrared range under oblique incidence. The absorption can be tuned from 0% to 100% by controlling the relative phase of the coherent incident light, showing great capacity in absorption modulation. We also studied tunable coherent absorption of graphene placed in high refractive index media with a gap (symmetrically based graphene), finding that graphene keeps high absorption (over 90%) with near-infrared light, and the maximum absorption wavelength is determined by the thickness of the gap. The broadband and high tunable absorption in graphene in the visible and near-infrared light will provide an efficient way to manipulate the interaction between light and graphene and serve applications in optical modulators, transducers, sensors and coherent detectors. Moreover, this absorption enhancement theory also applies to other 2D materials including black phosphorus, MoS2 and so on.