| In this dissertation, the properties of the energy transport in thin films of silver nanoparticles on dielectric surfaces are explored. Specifically, this dissertation will present experiments in which an ultrafast laser (∼ 13 fs) centered at 800 nm is focused at normal incidence on a thin film of polydisperse silver nanoparticles on a quartz substrate. Upon excitation, discrete regions of polarized emission are observed as far as 100 micrometers from the focal spot. The intensity of these regions of emission can be controlled by the polarization and spectral phase of the laser used for excitation.;Studies into the properties of emission show that the emission is a two-photon induced luminescence, enhanced by localization of the electric field by the silver nanoparticles. The spatial distribution of the nonlinear photoluminescence is found to have characteristics very distinct from that of normal scatter.;Further studies suggest 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, explaining the dependence on spectral phase. 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.;The results presented in this dissertation regarding the nature and control of energy transport has great implications in the field of "plasmonics," which seeks to bridge the realms of electronics and photonics with specially designed waveguides. Such waveguides, which could potentially support both plasmon and electrical signals have been designed and experimentally tested by several groups, and work has been done to design nanoscale structures that act as mirrors and beamsplitters for SPPs. However, these groups continue to face reduced propagation lengths, restricting propagation to a few tens of micrometers. The approach presented here, in contrast, shows propagation and control over a 100 micrometer range. |
