Soliton propagation of light under conditions of adiabatic tracking and of a one-photon resistance

A theoretical investigation is reported of the behavior of optical pulses under quasiresonant adiabatic tracking conditions. It is shown that dispersion of the group velocity and saturation of the populations of the resonant levels may give rise to soliton propagation of light. The exact solution for the envelope of a soliton is obtained for the first time subject to the saturation effect. Expressions are derived for the critical energy density in a soliton and for its duration. A study is made of the influence of the resonant saturation on the shape of a soliton envelope and its parameters. An analysis is reported of the behavior of light pulses of energies higher and lower than the critical value. It is shown that these pulses exhibit three types of quasisoliton propagation: weak, strong, and steady-state. The results for the pulses are generalized to two-dimensional light beams in a nonlinear waveguide.