Investigation of visible emission and luminescence center evolution in Pr–La:CaF 2 single crystals for laser application

A series of Pr,La:CaF 2 single crystals grown using the temperature gradient technique (TGT) method were presented systematically with a detailed spectroscopic investigation. The results indicate that the distinct Pr 3+ –La 3+ cluster types have replaced the original Pr 3+ –Pr 3+ clusters after introducing La 3+ into the Pr:CaF 2 crystal, as demonstrated by density functional theory-based first principles calculation and spectral analysis. This cluster evolution has led to a drastic increase in the Pr 3+ emission quantum efficiency as the La 3+ concentration increases. Evaluation of the impacts of multiphonon relaxation and cross-relaxation processes on quantum yields also revealed that cross-relaxation processes persisted in the Pr, La co-doped samples, which led to not high quantum yields as expected. The incorporation of La 3+ substantially manipulated the local structure of Pr ions in the CaF 2 crystal lattice. Low temperature absorption and selective-site spectroscopy, and time resolved emission spectroscopy were applied to investigate the local structure symmetries of Pr ions in the Pr 3+ ,La 3+ :CaF 2 crystal. Despite a lower degree of discrepancy, two types of centers were observed in TRES, all of which showed cubic symmetry of these locations based on the cluster simulation.