Broadly tunable continuous-wave Tm,Ho:SrF2 and Tm,Ho:BaF2 lasers

We report on the first, to our knowledge, room-temperature continuous-wave laser operation of Tm3+,Ho3+-codoped barium and strontium fluoride crystals at similar to 2.1 mu m. The 3 at.% Tm, 0.5 at.% Ho:BaF2 laser generated 160 mW at 2073 nm with a slope efficiency of 31.0% and a laser threshold of 43 mW. The continuous wavelength tuning of this laser from 2010 to 2090 nm (tuning range, 80 nm) was demonstrated. The spectroscopic properties of Tm,Ho:SrF2 and Tm,Ho:Ba(2 )crystals were also determined, showing enhanced Tm3+ -> Ho3+ energy transfer in rare-earth clusters. For Ho3+ ions in BaF2, the stimulated-emission cross section is 0.40 x 10(-20) cm(2) at 2044 nm, and the thermal equilibrium luminescence lifetime is as long as 14.1 ms. .