Nonlinear light mixing by graphene plasmons

Graphene is known to be a strongly optical nonlinear material. Its nonlinear response can also be enhanced by graphene plasmons. We report a new nonlinear electro-absorption effect observed in nanostructured graphene due to excitation of localized graphene plasmons. We experimentally detect and theoretically explain enhanced nonlinear mixing of near-infrared and mid-infrared light in arrays of graphene nanoribbons. Strong compression of light by graphene plasmons implies that the effect is non-local in nature and orders of magnitude larger than the conventional local graphene nonlinearity.