Watt-level diode-pumped thulium lasers around 2.3 µm

We report on efficient diode-pumped mid-infrared lasers based on Tm:LiYF4, Tm:Y3Al5O12, and Tm:YAlO3 crystals. These lasers operate in the continuous-wave (CW) regime and deliver watt-level output power at the wavelengths of 2.2–2.3 µm (the 3H4→3H5Tm3+ transition). In particular, a 1.8 at. % Tm:YAlO3 laser pumped at 789 nm generates a maximum CW output power of 1.32 W at 2272–2277 nm with a slope efficiency of 33.1% (with respect to the absorbed pump power), a linear laser polarization (E∥b), and a fundamental transverse output mode (the measured Mx2=1.26, My2=1.68). In the quasi-CW regime, the output peak power is scaled up to 2.69 W. The pump quantum efficiency and the fractional heat loading are estimated and discussed.