Enhanced Broadband and Harmonic Upconversion from Coupled Semiconductor and Metal Nanoparticle Films

The enhancement of the nonlinear optical properties of hybrid nanoparticle films by coupling between metallic and plasmonic semiconducting nanoparticles is shown. A heterostructure comprising CuS and Au nanoparticle films separated by a thin layer of insulating ligands enhanced the yield of second-harmonic light by a factor of 3.3 compared with the sum of the constituent nanoparticles on their own. Heterostructures were fabricated with scalable solution-processing techniques that can create devices of arbitrary geometry. In addition to harmonic generation, the multiple-photon photoluminescence response of Au, CuS, and heterostructured films is also explored.