110 W All Fiber Actively Q-Switched Thulium-Doped Fiber Laser

We report a 100-W-level, repetition rate and pulsewidth tunable, all-fiber, thulium-doped master oscillator power amplifier system. The master oscillator was actively Q-switched by a fiber-coupled acousto-optic modulator. The generated pulsewidth could be tuned from 1.16 μm to 46.3 ns by adjusting modulation repetition rate from 1 kHz to 2 MHz, and the pulse repetition rate (PRR) can also be tuned from 1 kHz to 2 MHz, correspondingly. The maximum output power could be boosted to > 110 W (slope efficiency of 55%) through three-stage thulium-doped fiber (TDF) amplifiers at PRR from 100 kHz to 2 MHz. The spectrum bandwidth was about 0.8 nm at the maximum output power without obvious indication of nonlinear effects. To the best of our knowledge, this is the first demonstration of > 110-W, all-fiber, actively Q-switched TDF laser, and it has realized the largest tuning ranges both with the pulsewidth and the PRR.