Spectroscopy and cw operation of a 1.85 mu m 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 f irst time. Using a cwTi:sapphire laser as a pump source, a threshold absorb ed 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-quen ching and pump-absorption efficiencies as well as parasitic and intrinsic r eabsorption losses. The emission cross-section at the laser wavelength is d etermined using different methods, showing that the result of the J-O appro ach is, in this case, very uncertain.