Universal Aspects of Ultrafast Optical Pulse Scattering by a Nanoscale Asperity

We combine photoemission electron microscopy and electromagnetic simulations to describe the surface plasmon polariton dynamics following interaction of an ultrafast optical pulse with a slit coupling structure in a silver film. Through analysis of interference phenomena that lead to photoelectron emission from the silver film, we establish the universal contributions of a nanoscale asperity to the scattered surface field. Our results reveal the important role of surface cylindrical waves within the slit in the excitation of surface plasmon.