Spectroscopy and laser test emission in Tm3+ : BaYLuF8 single crystal

A novel laser material BaYLuF8 (BYLF), doped with 12 at% of Tm3+, has been grown and optically investigated, in order to evaluate its potential performances as a 2 mu m laser. The BYLF crystal is interesting mainly because indications are that the mixed crystal would be sturdier than BaY2F8 (BYF). The addition of lutetium would improve the thermo-mechanical properties of the host. Absorption, fluorescence and lifetime measurements have been performed in the temperature range 10-300 K focusing on the H-3(4) and F-3(4) manifolds, those involved in the laser scheme at 2 mu m. The Stark sublevels structure of Tm3+ up to the D-1(2) manifold has been figured out. Diode-pumped CW laser emission at 2 mu m has been achieved obtaining a slope efficiency of about 28% with respect to the absorbed power, by pumping along the Z-axis. A maximum output power of 240 mW was achieved by pumping along the favourable Y-axis, with an incident power of about 800 mW