Enhanced Nonlinearities in Double-fishnet Negative-index Photonic Metamaterials

We numerically analyze the optical response and nonlinear susceptibilities of fishnet metamaterials with the holes infiltrated by a third-order nonlinear dielectric. Through full-wave simulations and employing a nonlinear parameter retrieval method, we confirm and quantify the enhanced nonlinearities, showing bulk third-order nonlinear susceptibilities that are up to two orders of magnitude larger than the nonlinear dielectric. We also use the retrieved parameters to calculate the material figure of merits and the conversion efficiencies, showing material figure of merits up to two orders of magnitude larger and conversion efficiencies up to four orders of magnitude larger than the nonlinear dielectric alone. Though these results are calculated using one-unit-cell thick structures, the large magnitude of the enhancement still makes these structures attractive, allowing reasonable conversion efficiencies supported by even subwavelength slabs.