Signatures of plasmoemission in two photon photoemission electron microscopy

The imaging of surface plasmon polariton waves in two photon photoemission microscopy has been intensely studied during the past years, with a focus on contrast mechanisms and light-plasmon interaction. The possibility of photoemission from the plasmonic fields alone has so far not been addressed in such experiments. This was justified, since the intensity of the plasmonic fields at the surface was comparatively weak and nonlinear plasmonic effects were not to be expected. Here we discuss the properties of grating couplers for creation of intense and short plasmon polariton pulses for which the emission of electrons purely from the plasmonic field cannot be neglected any more. Two examples for signatures of such nonlinear plasmoemission effects in experimental two photon photoemission microscopy images are discussed.