Beam quality improvement at Raman conversion of multimode conical beam

The spatial structure of Raman-converted radiation was investigated numerically and experimentally for the case when the pump is a conical beam produced by an axicone from multimode laser radiation. Both conical and axial Stokes beam generation was found to be possible. The improvement of the laser beam quality was demonstrated numerically and supported by experiment on Raman conversion in barium nitrate crystal. The laser beam with the beam quality factor M2=11 was converted into the axial Stokes beam with M2=3.5 at the conversion efficiency of 20%. A two-times increase in the Stokes beam brightness was obtained.