Spectroscopy and cw operation of a 1.85 μm Tm:KY3F10 laser

Room-temperature cw laser operation on the F-3(4) --> H-3(6) transition at 1.85 mum of Tm3+ ions in a KY3F10 single crystal is reported here for the first time. Using a cwTi:sapphire laser as a pump source, a threshold absorbed pump power of 120 mW and a laser slope efficiency of 42.5% were achieved by using a 45% transmissive output coupler. Optimization of the activator concentration and crystal length is discussed taking into account self-quenching and pump-absorption efficiencies as well as parasitic and intrinsic reabsorption losses. The emission cross-section at the laser wavelength is determined using different methods, showing that the result of the J-O approach is, in this case, very uncertain.