High-power passively Q-switched thulium fiber laser with distributed stimulated Brillouin scattering.

We report a novel passively Q-switched 2 μm Tm(3+) fiber laser simply by distributed stimulated Brillouin scattering with an all-fiber configuration. The maximum output power is 2.49 W with an optical-to-optical slope efficiency of 12%, and the laser wavelength is centered at ~1991 nm with a spectral width of >10 nm. The single pulse energy can be over 50 μJ with a pulse width of about 20 ns, and the pulse repetition rate can be tuned from several kilohertz to tens of kilohertz by changing the pump power. To the best of our knowledge, this is the highest-average-power passively Q-switched 2 μm Tm(3+) fiber laser in the nanosecond regime.