Influence of parametric effects on the stimulated scattering of nonmonochromatic pump radiation

It is shown that when the intensity of broad-band pump radiation exceeds a critical value, phase locking of the interacting beams takes place. This can explain the reproduction of the temporal fluctuations of the pump pulse in the scattered radiation for an arbitrary active zone length and also the experimentally observed low threshold for laser action due to stimulated Raman scattering in a resonator pumped by nonmonochromatic radiation.