We report using a Raman fiber laser (RFL) based on a multimode graded-index fiber as a novel method for beam combination of two continuous wave pump beams. Due to stimulated Raman scattering, the RFL generates a Stokes beam which can be up to 300% brighter than the pump beams. Up to 5.8 W of Stokes power is generated with an optical conversion efficiency of 56%.
Nathan B. Terry, Kevin T. Engel, Thomas G. Alley, and Timothy H. Russell, "Use of a continuous wave Raman fiber laser in graded-index multimode fiber for SRS beam combination," Opt. Express 15, 602-607 (2007). https://doi.org/10.1364/OE.15.000602