Widely tunable, efficient 2 m laser in monocrystalline Tm3+:SrF2

We report on the growth, spectroscopy, and laser operation of monocrystalline Tm3+:SrF2. Spectroscopic investigations confirmed the presence of broad absorption and emission bands caused by inequivalent doped sites, introduced by charge compensation effects which also caused the clusterization of doping ions in the lattice. We obtained continuous-wave laser emission at about 2 ?m, with efficiencies comparable with other Tm-doped crystals. We also achieved an uninterrupted tuning range of 180 nm between 1.8 and 2 ?m. This characterization indicates that SrF2 enhances the cooperative mechanisms between Tm ions, helping to obtain remarkable laser performances at low doping concentrations.