Surface Plasmon Transmission And Control In Graphene Nanostructures

Graphene is a honeycomb-shaped sheet of carbon atoms arranged one-atomthick.Since it was found in 2004,graphene has attracted significant attention due to its unique electronic and optical properties.In recent years,with the development of terahertz technology and the discovery of surface plasmons polaritons(SPP)on graphene,the optoelectronic devices based on graphene has wide scientific and technological applications.Compared with traditional metallic SPP,graphene SPP has significant advantages: the higher wave vector of momentum;stronger sub-wavelength confiniment;the tunability is most important for graphene SPP.Its properties can be dynamically tuned by electrical doping in terahertz to infrared wavelengths.For the above reasons,we design and research on two kinds of nano structures based on graphene SPP,realizing the control of graphene SPP in nano scale.The main research content is as follows:(1)The basic theories of surface plasmon resonance and waveguide of SPP are introduced briefly.The wave vector matching condition and advantages of metal-dielectric-metal waveguide are analyzed.(2)A detailed analysis for the properties of graphene are performed,including the conductivity of graphene and the equivalent refractive index.Based on these,we also theoretically analyze the excitation conditions,dispersion relationship and propagation parameters of graphene SPP.(3)A waveguide structure consisting of graphene and Prague gratings is proposed.With help of leaky-mode resonance,highly confined plasmonic waves in monolayer graphene are efficiently excited using an sub-wavelength diractive gratings.By means of COMSOL,the numerical calculation software based on finite element method(FEM),the material parameters of graphene and geometric parameters of grating structure are optimized.The local characteristics of the SPP are further improved.(4)A nano structure comprising graphene sheet and series of stub resnoators is studied.Based on the phase-coupled effect,the Fabry-Perot resonator is formed betweentwo adjacent stub resonators.The SPP oscillates back and forth in the cavity,resulting in a significant enhancement of the transmitted light in a narrow band.The transmission spectrum can be adjusted in a wide range by changing material parameters of graphene and geometric parameters of stub resnoators.The calculation results of COMSOL are consistent with the results of scattering matrix theory.