Berlin 2012 – scientific programme
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O: Fachverband Oberflächenphysik
O 3: Plasmonics and nanooptics I
O 3.1: Talk
Monday, March 26, 2012, 10:30–10:45, MA 005
SHG imaging of gold nanocones in focused beams of different polarisations. — •Philipp Reichenbach1, Dominik Gollmer2, Monika Fleischer2, Dieter Kern2, and Lukas Eng1 — 1Institut für Angewandte Photophysik, Technische Universität Dresden, George-Bähr-Straße 1, 01069 Dresden — 2Institut für Angewandte Physik, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen
Nanostructures with sharp tips provide strong dipolar second-harmonic (SHG) light sources due to the combination of extreme field enhancement and breaking the centro-symmetry. We present second-harmonic measurements at gold nano-cones that are illuminated by a radially polarized, focused femtosecond beam at 800 nm in order to excite the tip. Nevertheless, we observe second-harmonic radiation emission either from the tip or from the cones’s bottom edges, depending on the cone size and surrounding medium. This behavior can be readily explained through numerical calculations of the field enhancement at the tip apex and the bottom face of the cones.
Furthermore, our measurements with a radially polarized focused beam are compared to measurements with linear or azimuthal polarization. Thus, the z-component of the electric field exciting the cone tip can be purposely switched on and off. Hence, we are able to clearly discriminate between SHG emission from the bottom edges and from the tip apex.