Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 13: Plasmonics and nanooptics: Light-matter interaction, spectroscopy I
O 13.11: Talk
Monday, March 12, 2018, 17:45–18:00, MA 041
Measuring the Orbital Angular Momentum of Plasmonic Vortex Fields — •Pascal Dreher1, David Janoschka1, Norman Dünne1, Bettina Frank2, Timothy J. Davis2,3, Harald Giessen2, Michael Horn-von Hoegen1, and Frank Meyer zu Heringdorf1 — 1Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, Duisburg, Germany — 24th Physics Institute and Stuttgart Center of Photonics Engineering (SCoPE), University of Stuttgart, Stuttgart, Germany — 3School of Physics, University of Melbourne, Parkville, Victoria, Australia
The ability of light to carry orbital angular momentum in addition to its spin angular momentum has been thoroughly investigated in the past. Recent efforts have shown that the combination of these angular momenta can be utilized to excite surface plasmon polaritons with helical wavefronts, i.e. plasmonic vortices. The angular momentum of the exciting light is completely transferred to the plasmon. Further angular momentum can be transferred to the plasmonic field in the form of a topological charge provided by helical nanostructures, e.g. Archimedean spirals. We will report on the imaging of plasmonic vortex fields employing pump-probe photoemission electron microscopy (PEEM) with sub-femtosecond time resolution. We show that the angular momentum state of plasmonic vortices can be extracted from time-integrated PEEM micrographs, by analyzing the plasmonic field distribution for Archimedean spirals with topological charges from one to ten. The presented results agree with the predictions of the Bessel theory for plasmonic vortices.