Sub-wavelength imaging of few-cycle nanoplasmonic near-fields using interferometric time-resolved photoemission electron microscopy

We present a first implementation of a novel perturbative autocorrelation technique for direct sampling of ultrafast electric fields with a photoemission electron microscope. Unlike conventional nonlinear autocorrelation, this method preserves the phase, providing a full characterization of the electric field without additional spectral information. This allows direct observation of sub-wavelength electric near-fields at plasmonic nanostructures on the shortest time scales, which we demonstrate at a monolayer of self-assembled 40-nm gold nanospheres with sub-100-nm spatial resolution.