Light scattering in gold nanorings

The optical response of gold nanoparticles of disk-like and ring-like shape is studied by analyzing their extinction cross section in the visible and near infrared regions. A strong dependence of the excitation modes on the actual geometry of the nanoparticles is found for particle diameters of approximate to120 nm. The nanorings exhibit pronounced extinction peaks at much larger wavelengths than the nanodisks. We present both experimental results and numerical calculations, which are in excellent agreement when the geometry is correctly described. Nanorings are also shown to enhance the spontaneous emission at the resonance, where the emission is focused primarily along the ring axis. Published by Elsevier Ltd.