Hybrid KTP-Plasmonic Nanostructures for Enhanced Nonlinear Optics at the Nanoscale

The search for miniaturized components for nonlinear optical processes needs a way to overcome the efficiency loss due to the effective size reduction of the active medium. Here we investigate a combination of a nanosized nonlinear dielectric crystal and metallic nanoantennas that benefits from both the intrinsic nonlinear conversion efficiency of the nonlinear medium and the local field enhancement of plasmonic resonances in metallic nanostructures. Careful comparison between experiments and numerical simulations reveals that the observed 10- to 1000-fold enhancement in second harmonic generation intensity in the hybrid structure relative to the isolated elements is attributed unequivocally to the field enhancement effect of plasmonic resonances on the nonlinear crystal for gold-crystal structures, while the enhancement observed in aluminum-based hybrid structures can be attributed to the linear dielectric effect on the plasmonic antennas.