Tunable Light Absorption And Lifetime Properties Of Graphene Based On Local Surface Plasmon Resonance

Surface plasmon,a kind of electromagnetic wave limited on the metal dielectric interface.It can break through the classical diffraction limit,and has the advantages of guiding,controlling and manipulating light in sub-wavelength size.Graphene,a two-dimensional honeycomb lattice material with a single atomic thickness,is very unique and has excellent photoelectric properties.In recent years,graphene surface plasmons(GSPS)have attracted great attention from researchers in various fields due to their dynamic tunability,strong field localization and low propagation loss.Based on the previous studies of surface plasmon and graphene,we have constructed several representative models.In order to study the optical properties of GSPS,we have carried out numerical calculation and theoretical analysis with the finite difference time domain(FDTD)and coupled mode theory(CMT):1.We has analyzed and studied the tunable surface plasmon based on graphene square ring structure.Due to the local field enhancement effect,the excited surface plasmon waves are strongly confined to the graphene grating region.Through the finite difference time domain simulation and coupled mode theory analysis,the change of resonant wavelength and the lifetime has been studied.The results show that with the change of Fermi energy and carrier mobility,lifetimes of GSPs can be adjusted.By analyzing the absorption spectrum,FDTD simulation results are in good agreement with CMT theoretical results.In addition,by changing the inner and outer diameter of the graphene square ring,as well as the refractive index of the substrate material,the band range of the resonant wavelength,the light absorption can also be adjusted.2.The structure of graphene dumbbell gratings have been established and simulated.By increasing the Fermi energy and carrier mobility,the absorption peak at the resonant wavelength is significantly increased,and the maximum value can reach53%.The corresponding resonant wavelengths have a blue shift,and the position of the absorption peak can be adjusted in a wide band.The number of resonant modes can be adjusted by changing the geometry,such as increasing the connecting band.In addition,the changing of other geometric parameters,such as radius and defect length,can adjust the resonant wavelengths and the light absorption.The proposed graphenenanostructures show good application prospects in the mid-infrared band,and provide the possibility and the design ideas for the future realization of the graphene based surface plasmon light modulators and absorbers.3.The designed cross-hole graphene array structure has three resonant modes,multiple absorption bands,and the corresponding high absorption peak.The structure shows that the light absorption of GSPs does not keep increasing with the increase of graphene proportion,so it is very important to choose the geometric parameters when designing and manufacturing devices.In addition,with the adjustment of Fermi energy,carrier mobility and some geometric parameters,the change of quality factor corresponding to resonant mode has been calculated and studied.The improvement of quality factor means that the bandwidth becomes smaller,which makes the designed filter and other devices more selective and have better stability in a smaller resonant range.