A novel approach of beam cleanup based on stimulated Brillouin scattering with a large core fiber is proposed to improve the laser beam quality. The fusion splice scheme from a single-mode fiber to a very large core fiber (105 µm) is first employed in stimulated Brillouin scattering to steadily excite the fundamental mode of the Stokes beam. As a result, the output beam achieves a measured M2 value of around 1.3 meanwhile the pump conversion efficiency is up to 90%, which is the best in the reports of stimulated Brillouin scattering cleanup to our knowledge.
