Nonlinear Goos-Hanchen(G-H)Effect And Optical Multistable In Graphene System

In the past few years.Nonlinear graphene,a kind of plasmonic materials,provide a feasible and new way for manipulating light field in nanoscales,with their excellent optical properties widely used for the investigations of multistable switches,photoelectric sensors,electromagnetic resonance and so on.In this paper,we mainly study the Goos-Hanchen shift and optical multistability effect based on the optical properties of nonlinear graphene in the terahertz frequency range.The contents of this thesis includes the following aspects:1.Tunable bistability in Goos-Hanchen effect with nonlinear graphene in the terahertz rangeGoos-Hanchen(G-H)effect is a fundamental optical phenomenon in which the light of linear polarization undergoes a lateral displacement from the position predicted by geometry optics,when reflected.In this work,we present a planar model system of a silica covered with a monolayer of nonlinear graphene,for achieving a tunable GH shift in terahertz range.It is theoretically found that the transition between a negative shift and a large positive one can be realized by altering the intensity of incident light,moreover,by controlling the chemical potential of graphene and the incident angle of incident light,we can further control the tunable G-H shift dynamically.2.Tunable optical multistability in nonlinear Graphene-wrapped core-shell nanocylinderWe study the nonlinear optical response in a nanostructure of core-shell cylinder embedded with nonlinear graphene,by using quasi-static theory and self-consistent mean-field approach.Two configurations are considered:(a)one monolayer graphene only is introduced into the core or shell,respectively;(b)the nonlinear graphene is wrapped on both core and shell simultaneously.It is found that in one layer case,the graphene can lead to enhanced optical Kerr nonlinearity;in two layers case,the strong couplings between the surface plasmons in each graphene layers can produce optical multistability under a wide range of incident light intensity.The threshold values for this optical multistability is largely dependent of geometric sizes of nanostructure and the chemical potentials of graphene.Our proposal suggests a new way for designing optical multistability devices,such as all-optical switches,optical memories and optical transistors.