Detailed simulations of plasma-induced spectral blueshifting.

A one-dimensional model, including pulse propagation and detailed ionization dynamics, is developed in order to calculate the spectrum of an intense femtosecond laser pulse transmitted through an atmospheric-density noble gas. The spectrum is broadened and blueshifted due to self-phase-modulation resulting from a combination of optical-field-induced ionization and collisional ionization. Different features in the spectrum can be used to indicate the relative importance of the two ionization mechanisms