810 W continuous-wave and singletransverse-mode fibre laser using 201 mu m core Yb-doped double-clad fibre

It is shown that continuous-wave kW-power fibre lasers can be built using double-clad fibres with relatively small cores. 810 W in a single-transverse-mode Output (M-2 = 1.27) is demonstrated experimentally with 20 mum core low-NA (NA = 0.06) Yb-doped double-clad fibre. A laser numerical model matches experimental results and predicts scalability of achievable powers into a multi-kW range.