Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 64: Plasmonics and nanooptics III

O 64.2: Vortrag

Donnerstag, 29. März 2012, 10:45–11:00, MA 005

Near-Field Investigation of Nanostructures with Normal Incidence Photoemission Electron Microscopy — •Pascal Melchior¹, Ernst Jan Vesseur², Alexander Fischer¹, Markus Rollinger¹, Daniela Bayer¹, Christian Schneider¹, Albert Polman², and Martin Aeschlimann¹ — ¹Fachbereich Physik and Research Center OPTIMAS, Technische Universität Kaiserslautern, Germany — ²FOM Institute AMOLF, Amsterdam, The Netherlands

Photoemission electron microscopy (PEEM) enables the mapping of the near-field distribution of nanostructures under broadband laser excitation with a subwavelength spatial resolution. The combination with ultrafast laser pulses makes PEEM to an excellent technique to address the electron dynamics of nanoantennas by means of nonlinear photoemission. In standard PEEM systems, a grazing angle of incidence is used for illumination. However, the asymmetric illumination causes phase retardation effects and complex intensity distributions because of the superposition of higher order plasmonic modes. The complexity of the observed photoemission behavior under grazing angle makes the interpretation of static near-field distributions as well as time-resolved measurements challenging. With a new PEEM configuration we now excite the sample under normal-incidence and are thus able to eliminate these effects. We show first results of phase-resolved normal-incidence (NI) measurements on gold ring resonators that enable us to distinguish the resonance behavior of individual nanostructures with a subwavelength spatial resolution. The results are corroborated with FDTD calculations of the near-field properties of the structures.