High power Q-switched fiber laser system emitting 26 mJ pulses with near diffraction-limited beam quality

We demonstrate a high-power Q-switched fiber laser system emitting 26 mJ pulse energy with sub 60 ns pulses. In combination with a repetition rate of 5 kHz an average power of more than 140 W was achieved. These results were enabled by a Large-Pitch fiber, which allows effective single-mode operation with high beam quality (M
²
<; 13) and mode field diameters exceeding 100 μm.