Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 74: Plasmonics and nanooptics IV

O 74.3: Talk

Thursday, March 29, 2012, 16:30–16:45, MA 005

Normal Incidence Photoemission Electron Microscopy for the Observation of Surface Plasmon Polaritons — •P. Kahl¹, S. Wall¹, C. Witt¹, C. Schneider², D. Bayer², A. Fischer², P. Melchior², M. Horn-von Hoegen¹, M. Aeschlimann², and F.-J. Meyer zu Heringdorf¹ — ¹Faculty of Physics and CeNIDE, University of Duisburg-Essen — ²Department of Physics and OPTIMAS, University of Kaiserslautern

Up to now the imaging of surface plasmon polaritons (SPPs) has been achieved in photoemission electron microscopy (PEEM) in a 2PPE process by illuminating a sample with fs laser pulses under grazing incidence. Under such conditions the experimentally observed Moiré-patterns can be explained by a time-integrated superposition of the light pulse and the SPP, resulting from the simultaneous propagation of the two pulses with different velocities, wavelengths and directions. This prevents a direct observation of SPPs, for example is the wavelength of the Moiré-pattern one order of magnitude larger than the SPP wavelength.

In normal incidence PEEM (NI-PEEM) the contrast mechanism is easier to interpret, because the propagation directions of the light and SPP pulse are perpendicular to each other. Experimentally, however, normal incidence is difficult to obtain. We will discuss two approaches to achieve NI-PEEM, based on different instrument designs. We demonstrate that the observed wavelength corresponds to the real SPP wavelength and that the location of excitation of the SPP on a silver island is adjustable by turning the polarization of the laser pulse.