High-efficiency 2.3 µm Tm:YLF laser based on 0.79 µm and 1.05 µm dual-wavelength pumping scheme.

A high-efficiency Tm:YLF laser at 2.3 µm is demonstrated based on a dual-wavelength pumping scheme with 790 nm LD and a tunable Yb:CALGO laser at around 1.05 µm. When employing single-wavelength pumping at 790 nm, a maximum output power of 3.1 W is obtained, while the maximum output powers of 0.35 W and 0.25 W are achieved for single-wavelength up-conversion pumping at 1055 nm and 1041 nm, respectively. By using 790 nm and 1055 nm dual-wavelength pumping regime, the maximum output power is enhanced to be 3.52 W, which is the highest output power ever achieved from the 2.3 µm Tm:YLF lasers, to the best of our knowledge. The output power of 3.52 W achieved by dual-wavelength pumping exceeds the sum of output powers obtained with the separate single-wavelength pumping at 790 nm and 1055 nm, which well shows that the ground state absorption process H→H under intense 790 nm pumping would induce a significant accumulation of Tm ions on metastable level F via cross-relaxation process, greatly promoting the excited-state absorption process F→F and enhancing the 2.3 µm radiation.