6 mJ, high-average-power, all-fiberized Q-switched fiber master oscillator power amplifier with low repetition rate.

We report an all-fiberized, high-pulse-energy, high-average-power, Q-switched fiber master oscillator power amplifier (MOPA) oscillated at 1064 nm. The seed source is an acousto-optic Q-switched fiber laser, which is driven by an arbitrary waveform generator. A preamplifier is developed to boost the average power to about 3 W. Finally, we achieved an average output power of more than 62 W and a pulse energy of 6.2 mJ at 10 kHz repetition rate. The pulse duration is about 157 ns corresponding to the peak power of 37.1 kW. The optical-to-optical efficiency of the main amplifier is 61.3%. The beam quality factors (M2) are 3.1 in both directions.