Tunable passively Q-switched Dy3+-doped fiber laser from 2.71 to 3.08 μm using PbS nanoparticles

We present the first widely tunable passively Q-switched Dy3+-doped ZBLAN fiber laser around 3 mu m pumped at 1.1 mu m using PbS nanoparticles as the saturable absorber (SA) to our knowledge. At 2.87 mu m, the modulation depth and saturation intensity of the SA were measured to be 12.5% and 1.10 MW/cm(2), respectively. Stable Q-switching was achieved over a wavelength range of 2.71-3.08 mu m (similar to 370 nm), which is a record tuning range from a pulsed rare-earth-doped fiber laser, to our knowledge. A maximum output power of 252.7 mW was obtained, with a pulse energy of 1.51 mu J, a pulse width of 795 ns, and a repetition rate of 166.8 kHz. This demonstration implies that Dy3+ is a promising gain medium for tunable pulsed sources in the 3 mu m band and shows for the first time, to the best of our knowledge, the potential of PbS as a mid-infrared SA. (C) 2019 Optical Society of America