Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 52: Photonics and Nanooptics II: Nonlinear Response
O 52.3: Talk
Wednesday, March 9, 2016, 11:00–11:15, S051
Nonlinear Emission of Electrons in a Strong Plasmonic Field — Daniel Podbiel1, Philip Kahl1, Bettina Frank1, Harald Giessen2, and •Frank Meyer zu Heringdorf2 — 1Faculty of Physics and CENIDE, University of Duisburg-Essen, 47048 Duisburg, Germany — 24th Physics Institute and Research Center SCoPE, University of Stuttgart, 70550 Stuttgart, Germany
Observing surface plasmon polaritons (SPPs) in a photoemission electronmicroscope (PEEM) is possible via nonlinear photoemission if ultra-short laser pulses (<20fs) of a suitable wavelength are directed onto the surface of a plasmonic material. We study the time-resolved propagation and interaction of SPPs by means of a direct conceptual visualization of the SPPs in a "normal incidence geometry". This experimental setup allows us to observe transient phenomena that exist for only a few femtoseconds during the coherent interaction of the ultrashort SPP pulses. In focusing structures for SPPs we find an unexpected time-signature of the nonlinear photoemission signal at the focus point that must be explained by emission of electrons from the SPP alone. The energy distribution of these 'plasmoelectrons' shows that the SPP fields are sufficiently high to make nonlinear photoemission pathways of higher orders the dominant contribution to the PEEM signal.