Soliton generation in stimulated Raman scattering and excitation of polar optical phonons

A theoretical analysis is made of the soliton regime in transient stimulated Raman scattering of light by polaritons. Conditions for soliton generation at the frequencies of the interacting waves are determined. It is found that the soliton regime is achieved for in-phase and antiphase configurations of the mechanical vibrations and oscillations of the infrared electromagnetic field. Destructive spatial-temporal modulation of the relative phase occurs in other cases. Analytic equations are derived to describe the main soliton parameters (amplitude, profile, dispersion law, velocity, and duration). It is found that the solitons have a Lorentzian profile and are π pulses, and their dispersion law corresponds to the center of the scattering line of stationary polaritons. An investigation is made of the frequency dependence of the soliton velocity near the lower and upper polariton branches and the ranges of polariton frequencies for which various types of solitons may be generated for given parameters of the problem are determined.