Growth, spectroscopy, and tunable laser operation of the disordered crystal LiGd(MoO_4)_2 doped with ytterbium

The disordered crystal LiGd0.936Yb0.064(MoO4)2 was grown with high optical quality by the flux method using Li2MoO4 as a solvent. The crystal possesses tetragonal symmetry belonging to the space group I4¯, with two nonequivalent sites occupied by the dopant. Spectroscopic studies at 5 and 300 K provided information on the Stark energy-level splitting and the absorption and emission cross sections of the Yb3+ ion. Laser operation of Yb3+ was obtained for the first time in such a Li-containing double tungstate or molybdate. The tuning range with a Ti:sapphire laser pumping extended over ∼32nm for the σ polarization and 23nm for the π polarization. Without a tuning element the laser performance was similar for the two polarizations. By using a 10% transmission output coupler, a maximum output power of ≈470 mW was obtained with a slope efficiency η=64.5% and the absorbed pump power at threshold was 520 mW. Laser operation was also achieved by pumping with a tapered diode laser and a fiber-coupled diode laser module, with a Yb laser output power of 0.66W in the latter case.