Watt-level diode-pumped thulium lasers around 2.3 µm.

We report on efficient diode-pumped mid-infrared lasers based on :, :, and : 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 → transition). In particular, a 1.8 at. % : 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 (∥), and a fundamental transverse output mode (the measured 2=1.26, 2=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.