Ultrashort laser-produced optical microcavities and ionization fronts

A class of nonlinear optical effects related to fast field ionization in an interference pattern is investigated by numerical simulations. Interference between counter-propagating ultra-short pulses slightly below the ionization threshold produces a layered distribution of free-electron density. In a dense dielectric target, this effect allows us to trap light between plasma layers creating a sort of optical microcavity. Other peculiar features include frequency upshift, pulse lengthening and self-generated relativistic ionization fronts.