In this work, deuterium loaded Yb-doped fiber has been proposed to mitigate mode instability in laser oscillator. Experimental results reveal that mode instability threshold power rises from ~459W to ~533W and ~622W at the condition of pristine fiber and fiber loaded with deuterium for 2 weeks and 4 weeks respectively. Mode instability threshold power is raised by more than 16% and 35% after 2 and 4 weeks deuterium loading compared to pristine fiber respectively, and laser slope efficiency is not affected by deuterium loading. The experimental results indicate that deuterium loading is effective in mode instability mitigation and showing potentials in further power scaling of high power fiber lasers.
We have demonstrated a kW continuous-wave ytterbium-doped all-fiber laser oscillator with 7×1 fused fiber bundle combiner, fiber Bragg grating (FBG) and double-clad gain fiber fabricated by corresponding technologies. The results of experiment that the oscillator had operated at 1079.48nm with 80.94% slope efficiency without the influence of temperature and non-linear effects indicate that fiber components and gain fiber were suitable to high power environment. No evidence of the signal power roll-over showed that this oscillator possess the capacity to highest output with available pump power.