Performance and wavelength tuning of green emitting terbium lasers

Wavelength tuning experiments in the green spectral range applying Tb 3+ -doped LiLuF 4 and Tb 3+ /Na + -codoped CaF 2 single crystals are presented. While in the former case almost 100 mW could be obtained throughout a total range of 7 nm, the inhomogeneously broadened emission features of Tb 3+ in the CaF 2 -matrix allowed for a continuous tuning range exceeding 10 nm. For initial characterization, free running continuous wave laser experiments using Tb 3+ -doped LiLuF 4 , Na + :CaF 2 , and stoichiometric TbF 3 crystals were carried out resulting in efficient continuous wave laser operation in the green spectral region. The density of active centers in TbF 3 is among the highest that can be obtained in solid state gain materials. Nevertheless, a slope efficiency as high as 32% was obtained from this crystal. High Tb 3+ -densities are essential to compensate for the adherent low absorption cross sections at useful pump-wavelengths.