Above threshold ionization in tightly focused, strongly relativistic laser fields

The dynamics of electrons ionized from high charge states by lasers with intensity >1020 W/cm2 have been studied. At these intensities vxB forces drive the electrons subsequent to ionization in a trajectory nearly parallel to the laser propagation direction. This gives rise to large energy gains as the electron rides in phase with the laser field over a long distance. Monte Carlo simulations illustrate that, unlike in case of ionization in sub- and near-relativistic intensity fields (<1019 W/cm2), the electron dynamics in the ultrarelativistic case are strongly influenced by the longitudinal electric fields found near the focus of a tightly focused laser