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

Abstract

Room-temperature cw laser operation on the ³ F ₄?³ H ₆ transition at 1.85 μm of Tm³⁺ ions in a KY₃F₁₀ single crystal is reported here for the first time. Using a cw Ti: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.