Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 34: Poster Session I (Graphene; Plasmonics and nanooptics; Coherence and coherent control in nanophotonics and plasmonics)
O 34.54: Poster
Dienstag, 27. März 2012, 18:15–21:45, Poster E
Near-Field of Strongly Coupled Plasmons - Uncovering Dark Modes Using PEEM — •Florian Schertz1, Marcus Schmelzeisen2,3, Reza Mohammadi2,4, Maximilian Kreiter2, Hans-Joachim Elmers1, and Gerd Schönhense1 — 1Insitut für Physik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany — 2Max-Planck-Institut für Polymerforschung, D-55128 Mainz, Germany — 3Center of Smart Interfaces, TU Darmstadt, D-64287 Darmstadt, Germany — 4Department of Physics, Payame Noor University, Tehran, Iran
Strongly coupled plasmons in a system of individual Au nanoparticles placed at sub-nm distance to a Au film (nanoparticle-on-plane, 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 non-linear electron emission process. To our knowledge, this is the first time that both far-field and near-field spectroscopy are carried out for identical individual nanostructures interacting via a sub-nm gap. Strongly resonant electron emission occurs at excitation wavelengths far off-resonant in the scattering spectra. Simulations based on classical electrodynamics confirm the observed differences of near- and far-field characteristics for a strongly coupled plasmonic model system. We thank DFG EL172/16-1 for financial support.