Incoherent And Coherent Optical Absorption Enhancement In Graphene

As a typical example of 2D materials,graphene has promising potentials in optoelectronics due to its excellent optical and electronic properties(such as ultrabroad spectrum response,linear energy-momentum relation,high carrier mobility).However,limited by its ultrathin thickness,graphene absorbs only 2.3% of the incident light,thus enhancing the interaction between graphene and light is of great importance.In this paper we proposed and studied several ways to enhance the light absorption in graphene by theoretical analysis and numerical simulation.Firstly,we studied graphene absorption enhancement by surface plasmonic light trapping of the metallic material and found that the absorption of graphene can be enhanced more than 20 times over a wide band.Then we studied absorption enhancement of graphene by coherent illumination in metallic and dielectric nanostructures.The results show that great absorption enhancement can be achieved and coherent illumination brings an extra flexible control over its absorption.In the third part of this paper,we studied the coherent absorption of suspended graphene and found that it can realize broadband perfect absorption by coherent glancing incident,and after the suspended graphene,we use the dielectric slabs to biuld a F-P cavity,then we can realize perfect absorption of graphene at acceptable incident angle.Apart from these,as a research expand,we studied the surface plasmons of black phosphorus(another 2D material)and achieved its anisotropic absorption enhancement in the middle-far infrared wavelength which showed great ability in polarization control.