Enhancement of plasma wakefield generation and self-compression of femtosecond laser pulses by ionization gradients

As lasers become progressively higher in power, optical damage thresholds will become a limiting factor. Using the non-linear optics of plasma may be a way to circumvent these limits. In this paper, we report on simulations showing an enhancement to plasma wakefield self-compression of femtosecond laser pulses due to an ionization gradient at the leading edge of the pulse. By operating in a regime where wakefield generation is driven by moderately relativistic (similar to 10(18) W cm(-2)) laser pulses and proper choice of gas species, the ionization front of the pulse can lead to a frequency shift that enhances the ponderomotive force and therefore both the wakefield generation and subsequent pulse compression