| We study the dynamics of localized and propagating surface plasmon polaritons in nanostructured Ag films on femtosecond temporal scale and nanometer spatial scale by means of interferometric time-resolved two-photon photoelectron emission microscopy (ITR-PEEM). Identical, phase correlated pump-probe pulses excite two-photon photoemission mediated by surface plasmon excitation in a silver film, and the resulting emission is imaged with electron optics. The combination of laser excitation an electron imaging provides <10 fs temporal and 50 nm spatial resolution. We record movies at a delay rate increment of 330 as/frame of surface plasmon propagation, dispersion, dephasing, interference and focusing in nanolithographically patterned metal films. The ITR-PEEM method provides a revolutionary advance in ultrafast electron microscopy for visualizing and controlling electromagnetic fields and ultrafast processes on the nano-femto scale. |
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