Giant enhancement of the third harmonic in graphene integrated in a layered structure

Graphene was shown to have strongly nonlinear electrodynamic properties. In particular, being irradiated by an electromagnetic wave with the frequency $\omega$, it can efficiently generate higher frequency harmonics. Here we predict that in a specially designed structure "graphene -- dielectric -- metal" the third-harmonic ($3\omega$) intensity can be increased by more than two orders of magnitude as compared to an isolated graphene layer.