Propagation of ultrashort electromagnetic pulses in a Kerr medium with impurity atoms under quasi-resonance conditions

The study of the propagation of an electromagnetic ultrashort pulse in a Kerr medium with impurity atoms under quasi-resonance conditions is reported, which demonstrates the efficiency of the unitary transformation method in nonlinear optics. An equation is derived, which differs from the known equations describing the evolution of a pulse envelope and takes into account the dispersion of the nonlinear response and the dispersion of group velocities.