Propagation of an ultrashort light pulse in the region of zero second-order dispersion of group velocities

The propagation of a light pulse with a duration in excess of 100 fs is described by a generalised nonlinear Schrodinger equation with a derivative. At frequencies in the region of zero second-order dispersion of the group velocities this equation assumes the form of a complex modified (nonintegrable) Korteweg—de Vries equation. The adopted model is used to derive a system of ordinary differential equations that yield a small number of parameters of a light pulse as an alternative to the description of its evolution. The threshold energy, above which the dispersion broadening of such a pulse should be suppressed, is determined.