High Power Two-Micron Fibre Lasers

A double-clad thulium-doped silica fibre laser, pumped by two beam-shaped diode-bars operating at 787-790nm, has yielded 14W of single-mode output at similar to2mum, with a slope efficiency with respect to launched power of 46%. Using a tunable laser configuration, comprising an external cavity with a diffraction grating, a maximum output power of 10.5W at 1921nm has been obtained, and wavelength tuning at multi-watt power levels over 215nm from 1855 to 2070nm has been demonstrated. The prospects for further improvement in performance will be discussed. In addition, a simple approach for further scaling of power levels from fibre lasers in the two-micron regime, based on intracavity wavelength combining of multiple fibre lasers is described. In a preliminary demonstration, four cladding-pumped thulium-doped silica fibre lasers are wavelength-combined yielding an output power >14W. The prospects for further increase in output power via this approach will be discussed.