High-power widely tunable Q-switched thulium fiber lasers

Based on acousto-optic modulation and grating diffraction, a high-power-pulsed ∼2 μm laser with a wide tunable wavelength is realized in double-clad Tm fibers. A maximum average output power of 35.6 W is obtained with the 6 m fiber, which also provides a maximum pulse energy and peak power of 1.58 mJ and 5.6 kW, respectively. For the 6 m fiber length, a  >20 W average power can be achieved over a 100 nm wavelength tuning range. Shortening the fiber length to 2 m and 1 m can extend the wavelength tuning range further to shorter spectral regimes (1892 nm and 1881 nm). Short fiber length also narrows the Q-switched pulse duration to 90 ns. This kind of high-power, high-pulse-energy, widely tunable, and narrow-bandwidth ∼2 μm fiber lasers can find wide applications in various regions. (letter)