Obtaining constant sub-25 ns pulse in a Q-switched Tm laser with around 100 kHz repetition frequency

Conventionally, pulse duration of Q-switched lasers changes dynamically with the lasing power and pulse repetition frequency (PRF). Especially in quasi-three level Tm lasers, owing to the small emission cross section, they should oscillate at a PRF of below 50 kHz for a short Q-switching pulse that generally limited at tens of nanosecond. In this paper, we demonstrate an unprecedented electro-optically Q-switching scheme with constant short pulse duration of sub -25 ns at high PRFs ranging from 75 kHz to 150 kHz. Maximum average output power of 22.4 W at 1936.8 nm is obtained at 75 kHz, where average pulse duration of 21 ns with a deviation below 0.8 ns is realized during the whole Q-switching process, corresponding to a maximum peak power of 14.2 kW. The results provide an efficient way to achieve constant short nanosecond pulse in the high-power Q-switched Tm lasers, which could work at a PRF of above 100 kHz and facilitate a variety of appealing applications in material processing, surgery, and nonlinear frequency conversion toward the mid- and far-infrared regions.