Numerical Analysis on Tunable Multilayer Nanoring Waveguide

We propose a multilayer nanoring waveguide with ultrahigh refractive indices in this letter. The field confinement of the multilayer nanoring waveguide is stronger than the same outside radius of graphene-coated nanowire waveguide from the comparison of the normalized mode area. The influence of changing structure parameters on the properties of nanoring waveguide is analyzed. Based on the characteristic of the tunable surface conductivity of graphene, the effective refractive indices and propagation lengths of graphene plasmons modes can be tuned by the chemical potential of graphene. Furthermore, the geometry of the multilayer nanoring waveguide is compact and the method of chemical vapor deposition can be used to manufacture the proposed waveguide.