Influence of the width of a spectral line on the excitation of stimulated scattering in resonators

An analysis is made of the influence of the width of the pump line on the stimulated scattering in Fabry–Perot and ring resonators which are tuned both to the pump frequency and to the frequency of the Stokes component. It is shown that the excitation threshold of the stimulated scattering in dispersion-free media is independent of the width of the pump line, because of the parametric interaction between the modes, whereas in media with a considerable dispersion the threshold is Δω_p/Δω_sp greater than the stimulated emission threshold under monochromatic pumping conditions (the subscripts "p" and "sp" refer to the pump wave and to the spontaneous Raman scattering). Analytic expressions are given for the amplitudes of the pump and Stokes fields at the excitation threshold and under steady-state conditions.