Propagation of intense, ultrashort laser pulses through preionized plasma slabs

Relativistic self-focusing and channel formation induced by intense, ultrashort laser pulses in preionized targets is modeled for accessible experimental parameters. The stability of channel formation is limited by the nonparaxiality of the laser beam in regions of tight self-focusing. This issue is examined with recently developed nonparaxial theory. Channel formation is also characterized in terms of the transmitted pulse spectrum, the transmitted laser intensity profile, and the radial electron density distribution. Calculations indicate a signature spectral shift in transmission biased toward longer wavelengths, which is attributed to the rapid expulsion of electrons away from the propagation axis.