Propagation Properties Of Surface Plasmonic Optical Waveguide Coated With Graphene

In the THz regime,graphene has similar characteristics with metal materials,that it can support surface plasmons.Compared with the metal surface plasmons,graphene surface plasmons have extreme large mode confinement,the propagation distance is longer in the infrared region,and the propagation performance can be tuned by changing the chemical potential,exerting bias voltage and regulating the temperature.So graphene surface plasmons have been attracted considerable attention.The surface plasmon optical waveguides based on graphene can break through the diffraction limit,and realize the miniaturization and high integration of photonic devices,due to nanometer scale.Therefore the surface plasmon optical waveguides based on graphene can construct nano photonic integrated chip as the basic elements of photonic integrated circuits,and ultimately achieve all-optical communication.In this paper,we first introduce the optical properties of graphene in brief,then summary the research situations of plasmon waveguides based on graphene.On this basis,we design two surface plasmon waveguides based on graphene,and discuss the relationship of the propagation properties and structure parameters and electromagnetic parameters in detail.S.pecific work is as follows:(1)In this paper,a kind of surface plasmonic waveguide constructed with double elliptical nano dielectric parallel lines coated with graphene is proposed.The dependence of propagation properties on electromagnetic parameters and structure parameters are studied by using the finite element method.The results show that,when the distance between two ellipse increases,the real part of the effective refractive index decreases gradually,the propagation distance increases first and then it falls down,and the mode area increases gradually.The effective refractive index,the propagation distance and the mode area can be adjusted finely by the elliptical semi minor axis.The higher the working frequency is,the smaller the real part of the effective refractive index is,the shorter the propagation distance is,and the larger the mode area is.The higher the temperature is,the larger the real part of the effective refractive index is,the shorter the propagation distance is,and the smaller the mode area is.(2)In this paper,a kind of double elliptical hollow surface plasmonic waveguide coated with a single layer of graphene on the inner wall is proposed.The dependence of propagation properties on electromagnetic parameters and structure parameters are studied by using the finite element method.The results show that,when the distance between two ellipses and the elliptical semi minor axis increase,the real part of the effective refractive index decreases,the propagation distance increases,and the mode area decreases.When the radius of cohesive arc increases,the real part of the effective refractive index increases,the propagation distance decreases,and the mode area increases.When the working frequency is higher,the real part of the effective refractive index is smaller,the propagation distance is shorter,and the mode area is the smaller.When the temperature is higher,the real part of the effective refractive index is the larger then it is fallen down,the propagation distance is the shorter,and the mode area is the smaller.This work has a theoretical guiding significance for the design,fabrication and application of the surface plasmon waveguide based on graphene material.