Visualization of Localized Intense Optical Fields in Single Gold−Nanoparticle Assemblies and Ultrasensitive Raman Active Sites

Abstract

We demonstrate visualization of localized intense electromagnetic fields in real space in well-tailored dimeric and trimeric gold nanospheres by using near-field optical techniques. With two-photon induced luminescence and Raman measurements, we show that the electric field is confined at an interstitial site in the aggregate. We also demonstrate optical switching operations for the electric-field localized sites in the trimer structure.