Growth, spectroscopic, and laser properties of Yb^3+-doped Lu_3Al_5O_12 garnet crystal

We have grown high-quality LuAG:Yb3+ crystals with 0.75, 3.8, 10, 12, 15, 20, and 50 at. % concentrations by the vertical Bridgman method. With low-temperature spectroscopy the Stark sublevel structure of the 2F7/2 ground state and the 2F5/2 excited state has been determined. With room-temperature spectroscopy, the emission cross section was found to be 3×10−20 cm2, being 1.5 times the YAG:Yb3+ emission cross section. The luminescence quantum efficiency was measured in samples with different Yb3+ concentrations. Its value was found to be 90% for 3.8 and 10 at. %, 84% for 20 at. %, and 70% for 50 at. % Yb3+. The laser-emission tunability under diode pumping was found to extend from 1045 up to 1095 nm in a 12 at. % sample with 3.15 mm thickness.