High-Power Continuous-Wave Directly-Diode-Pumped Fiber Raman Lasers

We describe novel fiber Raman lasers pumped directly by spectrally combined high power multimode laser diodes at similar to 975 nm and emitting at similar to 1019 nm. With a commercial multimode graded-index fiber, we reached 20 W of laser output power with a record slope efficiency of 80 %. With an in-house double-clad fiber, the beam quality improved to M-2 = 1.9, albeit with lower output power and slope efficiency due to higher fiber loss. We believe this is the first publication of a fiber Raman laser cladding-pumped directly by diodes.