posted on 2013-02-13, 00:00authored byBenjamin Gallinet, Thomas Siegfried, Hans Sigg, Peter Nordlander, Olivier J. F. Martin
Plasmonic modes with long radiative lifetimes combine
strong nanoscale
light confinement with a narrow spectral line width carrying the signature
of Fano resonances, making them very promising for nanophotonic applications
such as sensing, lasing, and switching. Their coupling to incident
radiation, also known as radiance, determines their optical properties
and optimal use in applications. In this work, we theoretically and
experimentally demonstrate that the radiance of a plasmonic mode can
be classified into three different regimes. In the weak coupling regime,
the line shape exhibits remarkable sensitivity to the dielectric environment.
We show that geometrical displacements and deformations at the Ångström
scale can be detected optically by measuring the radiance. In the
intermediate regime, the electromagnetic energy stored in the mode
is maximal, with large electric field enhancements that can be exploited
in surface enhanced spectroscopy applications. In the strong coupling
regime, the interaction can result in hybridized modes with tunable
energies.