"Coherent Light Scattering in Percolative Metallodielectric Nanoshells"
Miriam Deutsch
Oregon Center for Optics and Department of Physics
University of Oregon, Eugene, Oregon
Wednesday, April 27, 2005 -11 AM - 12:00 Noon in 375 LeConte Hall
Abstract
Nanometer-sized metal particles have been the focus of extensive
studies owing to their greatly amplified nonlinear optical (NLO) response. These amplifications
are attributed mainly to large enhancements of surface-induced electric fields at
the nanoparticles' plasma resonance. Additionally, localization of plasmon fields
into 'hot-spots' in semi-continuous metal films manifests in extremely large local
EM fields and giant enhancements of surface NLO phenomena. These novel optical
features may be accurately controlled by design of nanoparticle geometry. In
particular, noble metal shells (typically 10-30nm) surrounding dielectric core
particles. These systems exhibit unique optical extinction spectra, tunable through
appropriate design of their core-shell thickness ratios.
We have developed a new chemical deposition technique to fabricate silver-on-silica
core/shell mondisperse colloidal spheres. These nanoshells are unique in that they
do not consist of the usual smooth and continuous metal shell, but are rather
incomplete and often fractal. I will present our recent linear light scattering
experiments and their modeling using a percolation-based approach for the metal
shells, as well as first results demonstrating nonlinear frequency conversion
processes in these materials. The prospects for using these systems in engineered
optical sensor beds or self-assembled metallodielectric photonic crystals will be
discussed.
