Condensed
Matter & Surface Sciences
COLLOQUIUM
Garnett W. Bryant
National
The Nanooptics of Metallic Nanoparticles
Understanding
the nanooptics of metallic nanoparticles
is critical for applications in nanometrology, nanosensors, near-field imaging, nanoantennas,
for nanooptical communication, and in new metamaterials. These are all applications where large
optical response by a nanoscale structure is needed.
This large optical response is provided by the surface plasmons
(charge oscillations) that can be excited in these confined metallic
structures. In this talk, I discuss the plasmonic
excitations of single and coupled metallic nanoparticles
based on fully retarded, (numerically) exact, classical calculations of their
electromagnetic response. Results are compared with experiment to show that
classical theory provides an excellent model for these systems.
Similar
resonances in isolated and coupled nanoparticles mask
significant differences in their response. For isolated particles, the response
is a dipole-like charge oscillation, governed by intraparticle
restoring forces. In coupled particles, the interparticle
gap breaks the intraparticle symmetry, strongly
distorts the intraparticle dipolar response and localizes
charges at the gap. Strong interaction between charges across the gap
significantly redshifts the response and dramatically
increases the near fields. These effects become “singular” in the limit of
nearly touching nanoparticles. Several examples are
discussed to illustrate these effects.