Scaling of average power in sub-MW peak power Yb-doped tapered fiber picosecond pulse amplifiers

Prospects for average power scaling of sub-MW output peak power picosecond fiber lasers by utilization of a Yb-doped tapered fiber at the final amplification stage were studied. In this paper, it was shown experimentally that a tapered fiber allows the achievement of an average power level of 150 W (limited by the available pump power) with a peak power of 0.74 MW for 22 ps pulses with no signs of transverse mode instability. Measurements of the mode content using the S-2 technique showed a negligible level of high order modes (less than 0.3%) in the output radiation even for the maximum output power level. Our reliability tests predict no thermal issues during long-term operation (10 5 hours) of the developed tapered fiber laser up to kilowatt output average power levels. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement