Mode Analysis Of The Graphene-coated Double Elliptical Dielectric Nanowires

Graphene is a single-layer structure formed by densely arranged carbon atoms into a benzene ring structure.With the deepening of study on graphene,its unique optical and electromagnetic properties have captured the attention of researchers in many fields.Studies show that under the certain condition,graphene has metallic properties and can be used as a two-dimensional material that supports surface plasmons.Take advantage of the feature,if the dielectric are coated graphene on its surface,we will get the waveguides with good transmission characteristics.Moreover,compared with the traditional noble metal-based surface plasmon waveguide,the graphene-coated surface plasmon waveguide is greatly tunable,and the transmission characteristics of the waveguide can be changed by adjusting the Fermi level of the graphene.Research results show that if a single layer of graphene is coated on the surface of an elliptical dielectric nanowire,the transmission characteristics of the waveguide can be improved.If two elliptical nanowires with different parameters are placed on the same horizontal line at a certain interval,the changes of the wavelength of the waveguide,the Fermi energy of graphene and the distance between two nanowires can greatly affect the mode confinement ability and the propagation length.The specific work of this article is as follows:(1)A graphene-coated asymmetric elliptical dielectric nano-parallel wire waveguide is designed,and the corresponding structure model is established in the elliptical cylindrical coordinate system.The Mathieu function is used to express the electric field and magnetic field at any point in the field with the help of coordinate transformation.Bring them into Maxwell Equations to solve,we will obtain the field distributions of the six lowest-order modes.On the basis,the relevant parameters are constantly changed,and the dependence of these modes characteristics on the waveguide geometric parameters and electromagnetic parameters is explored to obtain a set of optimization the structural parameters of the waveguide in order to improve the overall transmission efficiency of the waveguide.The results reveal that,compared with adjusting the parameters of the nanowires,the changing of the working wavelength of the waveguide,the graphene Fermi energy and the spacing between the nanowires,the characteristics of these modes can be greatly altered.Under two conditions,by comparing the performance of the fundamental mode supported by graphene-coated single elliptical dielectric nanowires,symmetric elliptical dielectric nano-parallel wires and asymmetric elliptical dielectric nano-parallel wires,the performance of the proposed waveguide is found better than the other two waveguides.(2)The non-coaxial hollow elliptical dielectric nanowire waveguide being coated with graphene is designed.In the elliptical cylindrical coordinate system,with the help of Mathieu functions and coordinate transformation,the three lowest-order modes supported by the proposed waveguide are studied by the multi-pole method,and the dependence of the characteristics of these modes on the wavelength,the graphene Fermi energy,and the waveguide structure parameters are analyzed.Under the two conditions,by comparing the performance of the fundamental mode supported by graphene-coated single elliptical dielectric nanowires,asymmetric elliptical dielectric nanowires being coated by graphene and non-coaxial hollow elliptical dielectric nanowires,it is found that the transmission performance of the proposed waveguide is better than the other two,and the mode confinement ability and the propagation length are significantly improved.The results of this paper have great potential application value in the field of mode conversion,coupling devices and sensors.