Subfemtosecond and Nanometer Plasmon Dynamics with Photoelectron Microscopy: Theory and Efficient Simulations

We develop a theoretical model of
the excitation and interference
of surface plasmon polariton (SPP) waves with femtosecond laser pulses
and use the model to understand the features in images from subfemtosecond
time-resolved two-photon photoelectron microscopy (2PPE–PEEM).
The numerically efficient model is based on the optics of SPP modes
on multilayer thin films and takes account of the excitation and interference
by the incident light, its polarization, the boundary shape on the
film where the plasmons are generated, the pulsed form of the excitation
and the time integration associated with the PEEM method. The model
explains the dominant features observed in the images including the
complex patterns formed in experiments involving orbital angular momentum.
The model forms the basis of an efficient numerical method for simulating
time-resolved 2PPE–PEEM images of SPP wave propagation. The
numerics is extremely fast, efficient, and accurate, so that each
image can take as little as a few seconds to calculate on a laptop
computer, enabling entire PEEM movies to be calculated within minutes.