Dresden 2017 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 39: Plasmonics and Nanooptics IV: Light-Matter Interaction

HL 39.8: Vortrag

Dienstag, 21. März 2017, 12:15–12:30, TRE Ma

Single-particle spectroscopy of bare and porphyrin-covered silver clusters with multi-photon photoemission electron microscopy — •Klaus Stallberg and Winfried Daum — Institute of Energy Research and Physical Technologies, TU Clausthal, Leibnizstraße 4, 38678 Clausthal-Zellerfeld, Germany

Coupling of optical excitations in dye molecules with plasmonic excitations in metallic nanostructures holds the potential to provide control over light-matter interaction at a nanoscale level. Plasmonic-excitonic coupling has been reported for dye-coated metallic nanoparticles by application of particle-averaging methods. We apply multi-photon photoemission electron microscopy (nP-PEEM) with tunable-laser excitation to study localized surface plasmon resonances (LSPR) of individual silver clusters, which are grown under UHV conditions on silicon substrates. Simulations elucidate the influence of the supporting substrate on the LSPR, most notably an amplification of LSP modes with a polarization normal to the substrate. For particles covered with porphyrin (ZnTPP) the simulations predict the appearance of a second LSPR near the optical absorption (Soret-) band of the ZnTPP molecules, a consequence of coupling between the plasmonic near-field and and the excitonic polarization inside the ZnTPP layer. Depending on their spectral positions, both LSP modes are predicted to spectrally repel each other as a result of additional coupling between the LSP modes. In our laser spectroscopic nP-PEEM experiments we observe such spectral shifts for silver particles covered with a ZnTPP layer of only four monolayers.