Near-diffraction-limited output from confined-doped ytterbium fibre with 41 μm core diameter

A confined-doped ytterbium fibre with a 41 μm core diameter has been fabricated by direct nanoparticle deposition process. Near-diffraction-limited beam quality (M² ~ 1.3) was experimentally demonstrated from an amplified spontaneous emission source setup. Owing to the large core size and the confined Yb doping, the mode area is significantly enlarged while good beam quality is maintained. Such fibres have great potential for mitigating the detrimental nonlinear effects and for power scaling of fibre lasers and amplifiers.