Over 2 kW peak power quasi-continuous-wave thulium-doped fiber oscillator

High-performance quasi-continuous-wave fiber lasers are highly sought after for numerous applications. In this work, a high power quasi-continuous-wave thulium-doped fiber oscillator is demonstrated. The arc-fusion parameters of the gain fiber were systematically optimized to minimize splice loss, leading to a slope efficiency improvement from 35% to 53.6%. At a 10% duty cycle, the laser delivered a maximum average output power of 210 W. Under different operating conditions, it generated pulses with various durations and repetition rates, all exhibiting peak powers above 2 kW, with a maximum of 3088.2 W. To the best of our knowledge, this is the first demonstration of a QCW 1940-nm thulium-doped fiber laser achieving a peak power exceeding 2 kW, offering new prospects for future application-oriented research on 2-µm fiber lasers.