Intracavity stimulated Raman scattering with feedback at the Stokes frequency in a laser with active mode locking. I

Intracavity stimulated Raman scattering (STRS) in a cell containing compressed hydrogen placed inside a ruby laser resonator with active mode locking was investigated using an additional high-Q resonator locked to the frequency of the first Stokes component. A theoretical analysis of the dynamics of intracavity STRS and of its influence on mode locking in a master laser was made on the basis of a spectral–mode description of the field in the resonator. It was found that, depending on the nonlinear interaction between the modes governed by the hydrogen pressure and the length of a laser cell, it is possible to establish weak, optimal, or strong energy exchange between the laser and Stokes waves. An experimental study of STRS at various hydrogen pressures confirmed the calculations and showed that feedback at the Stokes frequency reduced the STRS threshold and increased the conversion efficiency.