Mode analysis of a confocal elliptical dielectric nanowire coated with double-layer graphene

Mode properties of a confocal elliptical dielectric nanowire coated with double-layer graphene are analyzed by using the separation of variables method (SVM). The graphene surface plasmon modes could be tuned by changing the working wavelength, the distance between semi-major axes, the Fermi energy level of graphene and the geometry parameters. The results show that the semi-analytical results of SVM are completely consistent with the numerical simulation results of finite element method (FEM). Compared with the elliptical dielectric nanowire coated with single-layer graphene, the novel waveguide structure has stronger mode confinement, lower propagation loss, larger propagation length, wider adjustable working wavelength and wider adjustable Fermi energy level of graphene. The waveguide may be exploited for many applications such as plasmon resonances, detectors and microstrip antennas.