  We study the non-equilibrium response of a 4x3 Hubbard model at U=8 under the
influence of a short electric field pulse, with the main focus on multiple
photon excitations and on the change of double occupancy after the pulse. The
behavior mainly depends on the driving frequency of the electric field. The
largest change of double occupancy occurs during the pulse. For frequencies
below the Mott gap, we observe multiphoton excitations at large field
intensities. For frequencies beyond the gap energy, there is a region where
Auger recombination reduces the double occupancy after the pulse. Impact
ionization (Multi Exciton Generation), namely a growing double occupancy after
the pulse, occurs for frequencies larger than twice the Mott gap. From the
Loschmidt amplitude we compute the eigenstate spectrum of the quantum state
after the pulse, observing multiple distinct photon excitation peaks, in line
with expectations from a quasiparticle picture. We introduce a technique with
which we analyze the time evolution of double occupancy in each peak
individually. The long-term behavior of the double occupancy almost only
depends on the absorbed energy, and we explore the connection of this property
to the Eigenstate Thermalization Hypothesis.
