Cavity Or Grating Enhanced Graphene Surface Plasmons And Its Microscopic Mechanism

Surface plasmons(SPs)have the ability to overcome the diffraction limit and manipulate optical signals in the nanometer range,and thus have extraordinary application value in the field of highly miniaturized and integrated optoelectronic devices.Conventional noble metal surface plasmons have been faced with problems such as short lifetime and short propagation distance,which greatly limits the application value of micro-nano optoelectronic devices based on surface plasmons.Compared with metal surface plasmons,graphene surface plasmons have many advantages,and have been highly valued by research organizations at home and abroad.However,the microscopic mechanism and enhancement mechanism of graphene surface plasmon,especially the study of its life,is not enough.Therefore,according to the finite difference time domain method(FDTD)and coupled mode theory(CMT),this paper uses cavity and grating to enhance the surface plasmon of graphene,and conducts in-depth research on its micro-mechanism,enhancement mechanism and mode attenuation factor(lifetime).The main contents include:1.The transmission characteristics of the graphene-cavity coupled waveguide system were analyzed.It has been explored on the microscopic mechanism of the surface plasmon and the link between the geometric parameters and physical parameters of the system in-depth.The results show that there are three transmission troughs in the system due to the coupling between the graphene mode and the cavity mode.And the resonant wavelength of the transmission spectrum can present red shift with reducing the fermi level of graphene.In addition,we incorporate kerr nonlinear material into the cavity and find that the resonant mode is affected by the linear refractive index of the core,the polarizability of the nonlinear material,and the intensity of the incident light.The results show that the graphene-cavity structure is a candidate for designing an active graphene surface plasmon device.2.The absorption and mode attenuation(lifetime)characteristics of the double rectangular graphene array structure were analyzed.The effects of fermi level,carrier mobility and structural physical parameters of graphene sheets on the absorption rate and mode attenuation(lifetime)characteristics of graphene were investigated.The results show that the absorption rate of single-layer graphene can be increased from 2.3% to about 40%.This absorption enhancement is derived from the excitation of the surface plasmon resonance mode of graphene.By increasing the fermi level of graphene,the wavelength of the absorption peak will present blue-shift,the absorption rate will increase,and the mode attenuation rate will change accordingly.By increasing the carrier mobility of graphene,the wavelength of the absorption peak is basically unchanged,and the absorption rate will increase,the mode decay rate also changes.The absorption enhancement and resonant mode adjustability of the graphene array can be widely applied to high performance adjustable graphene surface plasma devices.3.The absorption and mode attenuation(lifetime)characteristics of the double rectangular-porous graphene array structure were analyzed.The results show that when the fermi level and carrier mobility of graphene are changed,the resonant wavelengths of the three resonance modes of the structure will change,and the structural parameters will be adjusted to the resonance mode.This study provides a theoretical basis for the application of graphene optoelectronic devices.