NUMERICAL-SIMULATION OF STIMULATED-RAMAN- SCATTERING CONVERSION OF FEMTOSECOND UV PULSES

A numerical simulation is reported of transient parallel stimulated Ra man scattering (SRS) of femtosecond pulses in dispersive molecular gas es. The one-dimensional two-wave approximation is used and the self-in teraction as well as the cross-interaction of the pulses are taken int o account. The kinetics of formation of a Stokes pulse and the transfo rmation of the spectrum and temporal profile in the course of amplific ation to saturation are tackled for the first time. It is shown that a fundamental role is played by the influence of the difference between the group velocities, which governs the rate of passage of a Stokes p ulse along the pump pulse, on the SRS conversion parameters. Depending on this velocity difference, which is a characteristic of the active medium and proportional to its pressure, the SRS falls into three regi mes: (1) a Stokes pulse repeats the profile of a pump pulse; (2) pulse compression with optimal gain and strong peaking of the leading edge; (3) multi-spiking oscillation.