Microjoule-level nanosecond pulse generation from a 1.7 µm all-fiber Tm-doped fiber laser amplification system

We report a 1.7 µm all-fiber Tm-doped fiber (TDF) amplification system delivering nanosecond pulse with microjoule-level energy. The seed laser is a 1.7 µm mode-locked TDF laser operating in the regime of a noise-like rectangular pulse. The width of the nanosecond rectangular pulse can be flexibly tuned by adjusting the intra-cavity polarization state. After the two-stage TDF amplifier, the maximum output average power of 3.24 W can be obtained with a pulse width of 10 ns. Taking into account the 288.4 kHz repetition rate, the pulse energy after the TDF amplification system can be up to 11.2 µJ. These results demonstrate a simple but effective method for generating high-energy nanosecond pulse at the 1.7 µm waveband, exhibiting significant potential as a high-performance laser source for biomedical imaging and material processing.