Mode properties of elliptical dielectric waveguide with nested eccentric hollow cylinder coated with graphene

Abstract

An elliptical dielectric nanowire waveguide with a nested eccentric hollow cylinder is designed, the inner and outer surfaces of the waveguide are coated with graphene. The transmission characteristics of the three lowest order modes supported by the waveguide, that is the field distribution, the real part of the effective refractive index, the propagation length and the quality factor, are obtained by multipole method. The results show that the three lowest order modes of the waveguide can be synthesized by the lowest order modes supported by a single cylinder and an elliptic cylinder coated with graphene. With the increase of the radius of the embedded cylinder, the three evaluation indexes of the waveguide increase slightly; The change of the semi major axis of the ellipse will slightly increase the real part of the effective refractive index, propagation length and quality factor of Mode0 and Mode1, while Mode2 will slightly decrease. When a=b=170nm, the performance of the circular nested circular waveguide is slightly worse than that of the structure in this paper; With the decrease of the semi minor axis of the ellipse, the real part of the effective refractive index, propagation length and quality factor of the three modes increase to a certain extent, and have the greatest impact on Mode 1. When b=a=190nm, the transmission performance of the circular nested circular waveguide is not as good as that of the structure in this paper; When the distance between the inner and outer rods on the right increases, the real part of the effective refractive index of the three modes decreases, the propagation length and quality factor of Mode0 and Mode1 gradually decrease, while the propagation length of Mode2 increases slightly, and the quality factor is basically unchanged. On the contrary, the mode transmission performance can be significantly improved by increasing the working wavelength, Fermi energy and reducing the dielectric constant of elliptical dielectric nanowires. Compared with the circular dielectric nanowire waveguide nested with an eccentric hollow cylinder coated with graphene, it can be found that the waveguide designed in this paper has better transmission performance. These results have been verified by the finite element method. This waveguide can provide a theoretical basis for the design, fabrication and application of nested waveguides of the same type.