Tuning the dispersion relation of a plasmonic waveguide via graphene contact

Abstract

In this work, we have investigated experimentally and theoretically the dispersion relation of a plasmonic slab waveguide, where the thin gold film with nano-aperature arrays is sandwiched by graphene and a silica layer on a silicon chip. It is shown that the plasmonic slab waveguides are compatible with silicon technology. We have found that when the light waves irradiate the nanostructured waveguides with or without graphene, surface plasmon polaritons are always excited at the metal-dielectric interface due to the interaction between the surface charge oscillation and the electromagnetic field of the light. But in the slab waveguide with graphene, the resonant dips definitely shift in the reflection spectra, which indicates that the contact of graphene can tune the dispersion relation of the waveguide in the visible regime. Experimental measurements on optical reflections are in good agreement with calculated plasmonic band structures. Further calculations show that the dispersion relation of plasmonic slab waveguides can be tuned by electron doping and the nonlinear effect of graphene. The investigations provide a way to actively control the dispersion relation of plasmonic waveguides on silicon chips and benefit the development graphene-related active optical devices.