Advances In High-Brightness Fiber-Coupled Laser Modules For Pumping Multi-Kw Cw Fiber Lasers

High-power continuous wave (CW)fiber lasers with excellent beam quality continue to drive demand for higher brightness pump modules at 920 nm and 976 nm. Over the last decade, the brightness requirement for pumping state-ofthe-art CW fiber lasers (CWFLs)has risen from approximately 0.5 W/(mm-mR)(2) to similar to 2 W/(mm-mR)(2) for today's mutlikW CWFLs. The most advanced CWFLs demand even higher brightness pump modules in order to minimize design complexity, maximize efficiency, and maximize the stimulated Raman scattering threshold. This need has resulted in a reoptimization of the nLIGHT element (TM) line to enable a commercial 200 W, 18-emitter package with a 0.15 NA beam in a 105 mu m fiber, corresponding to a brightness of 3.2 W/(mm-mR)(2) and a 25 % increase in power over the existing element (TM) e14 at 155 W. Furthermore, we have demonstrated the further scalability of this reoptimized design with our next generation COS, resulting in a maximum of 272 W into 105 mu m fiber with a brightness of 3.8 W/(mm-mR)(2).