Ytterbium-doped large-core fibre laser with 1 kW of continuous-wave output power

A ytterbium-doped fibre laser with up to I kW of continuous-wave output power at 1.09 mum with a slope efficiency of 80% and a good beam quality (M-2 = 3.4) is reported. The fibre was pumped by two diode-stack sources launched through opposite ends. No undesirable roll-over was observed in output power with increasing pump power.