Stimulated Raman forward scattering with a divergent or convergent pump beam

Stimulated Raman forward scattering is investigated for a divergent or convergent pump beam. The rate equations for this case are derived and analytically solved, including pump depletion. The solutions are compared to an experiment where the generation of a Stokes pulse from noise is investigated with a pump beam of variable divergence. Theoretical and experimental results are in good agreement. Stimulated Raman forward scattering thus may be controlled by the beam geometry, e.g., in Raman pulse compressors. An example is discussed in the Appendix.