Optical Stark effect in an active medium

The semiclassical approximation is used in an analysis of the nonlinear shift of the frequency of an electric dipole transition in a high-power radiation field. It is shown that the shift can only increase the frequency. The magnitude of the shift is proportional to the field intensity but independent of its frequency. Secondapproximation relationships are derived for the calculation of the parameters of the interaction of the field with an active medium. Numerical estimates of the Stark effect are obtained for some gaseous active media.