Near Field of Strongly Coupled Plasmons: Uncovering Dark Modes
Florian Schertz, Marcus Schmelzeisen, Reza Mohammadi, Maximilian Kreiter, Hans-Joachim Elmers, Gerd Schönhense
Volume: 12, Issue: 4, 19 March 2012
1885 - 1890
Plasmon coupling, subnanometer gap, gap resonance, dark mode, near field, sphere-on-plane
Strongly coupled plasmons in a system of individual gold
nanoparticles placed at subnanometer distance to a gold film (nanoparticle-onplane, NPOP) are investigated using two complementary single particle spectroscopy techniques. Optical scattering spectroscopy exclusively detects plasmon modes that couple to the far field via their dipole moment (bright modes). By using photoemission electron microscopy (PEEM), we detect in the identical NPOPs near-field modes that do not couple to the scattered far field (dark modes) and are characterized by a strongly enhanced nonlinear electron emission process. To our knowledge, this is the first time that both farand near-field spectroscopy are carried out for identical individual nanostructures interacting via a subnanometer gap. Strongly resonant electron emission occurs at excitation wavelengths far off-resonant in the scattering spectra.
Back to References