Enhanced hybrid optics by growing silver nanoparticles at local intensity hot spots

Silver nanoparticles (AgNPs) show an extraordinary strong interaction with light, which enables confinement and field enhancement at the nanoscale. However, despite their localized nature, such phenomena are often sought to be exploited on a larger device length scale, for example, in sensors, solar cells, or photocatalytic cells. Unfortunately, this is often limited by strong absorption. One way to reduce these losses is to first focus light with low loss dielectric optics and then to place the AgNPs in that focus. Here, we present a clear experimental proof that growth of AgNPs from the liquid phase at a substrate surface can be controlled by light. Violet light of 405 nm and 1.5 W/cm2 is coupled into thin film resonators and locally focused at their surface. The AgNPs grow at the focus position with sub-Abbe alignment accuracy. Numerical simulations confirm that this alignment causes an increased field enhancement within the AgNPs and is therefore expected to lead to an improved performance of the resulting hybrid devices.