  We explore the nonlinear response of plasmonic materials driven by ultrashort
pulses of electromagnetic radiation with temporal duration of few femtoseconds
and high peak intensity. By developing the Fokker-Planck-Landau theory of
electron collisions, we solve analytically the collisional integral and derive
a novel set of hydrodynamical equations accounting for plasma dynamics at
ultrashort time scales. While in the limit of small light intensities we
recover the well established Drude model of plasmas, in the high intensity
limit we observe nonlinear quenching of collision-induced damping leading to
absorption saturation. Our results provide a general background to understand
electron dynamics in plasmonic materials with promising photonic applications
in the manipulation of plasma waves with reduced absorption at the femtosecond
time scale.
