Studies On Optical Absorption Characteristics Of Photonic Crystal With Graphene-based Defect

Graphene is a two-dimensional material consisted of hybridizd carbon atoms arranged in hexagonal honeycomb crystal lattice.A unique electronic band structure exists in graphene because of the special lattice structure,which leads to many excellent material properties such as high electron mobility,excellent thermal conductivity,high mechanical strength,broadband light absorption,long carrier life,chemical inertness and etc.Therefore,graphene presents great value in application of many fields such as photoelectric detection,solar cell,sensing,biomedicine and so on.However,a monolayer graphene absorbs only 2.3%of the incident light under the condition of vertical irradiation due to its single-atom-layer thickness and low photoconductivity in the visible and near-infrared regions.The weak interaction between light and graphene limits the application prospect of graphene in the field of photoelectric detection.As a result,one of the prominent challenges is how to enhance the optical response of graphene,and then regulate the light absorption of graphene.In order to increase the optical absorptance of graphene,three kinds of one-dimensional photonic crystal with graphene-based defect are proposed in this paper.The optical properties of these structures in the visible to near_infrared regions are theoretically calculated by using this transfer matrix method and numerically simulated through software.The effects of internal parameters and external conditions on the absorption characteristics of the three structures are mainly studied,and the causes of the results are analyzed.Simulation results show that the micro-cavity structure is formed to localize the light when graphene is embedded in photonic crystal,thus the absorption of graphene is significantly improved to 100%in the visible to near-infrared regions and even dual-band perfect absorption can be realized.Besides,the position and number of the resonant wavelengths can be controlled by varying the relevant structural parameters,incident angle and the applied voltage so as to achieve the purpose of manually regulating the absorption of graphene.This paper provides the theoretical basis and design concept for the study of graphene absorber and provides guidance for future applications in optical detectors,filters,and sensors.