The Raman gain coefficient for nonplanar pump wave is calculated. The gain dependence for wavefront reproducing Stokes conversion and for an injected plane Stokes wave on the pump beam quality is derived. The amount of plane Stokes wave injection required to generate a plane Stokes wave output is discussed. A comparison is given for the homogeneity requirement of the pump laser medium as reflected in the pump beam quality for the cases with and without Raman conversion for near diffraction limited output. The results indicate that with the appropriate plane Stokes wave injection, the medium homogeneity requirement of the laser can be relaxed.