Measurement and Control of Ultrashort Optical Pulse Propagation in Metal Nanoparticle-Covered Dielectric Surfaces

In this paper, we present a detailed study of localized two-photon photoluminescence from metal nanoparticles on a dielectric surface. An ultrafast (similar to 13 fs) near-infrared laser focused on a micrometer sized region is used to excite a silver nanoparticle covered quartz or mica substrate, and a pulse shaper is used to control and change the spectral phase of the excitation pulse, as well as allow for autocorrelation-type measurements. Spectra of the observed photoluminescence from individual localized regions remote from the focal spot are obtained. The spatial distribution of nonlinear photoluminescence is found to have characteristics very distinct from that of normal scatter. It is found that the excitation pulse propagates to the different remote regions by means of surface plasmon polariton (SPP) propagation. As the SPP propagates it accumulates different amounts of quadratic and cubic dispersion depending on the path taken. The quadratic and cubic dispersion for a number of such pathways is measured, and evidence of negative dispersion is observed. Photoluminescence is observed at locations where constructive interference and a localized resonance occurs, tens of micrometers from the incident laser pulse.