Laser excitation of single ion and clustered ion sites in SrF2 : Er3+

Selective laser excitation has been used to study the optical properties of the charge compensated sites in 0.0001%, 0.01%, 0.05% and 0.2% concentrations of SrF₂ : Er³⁺. Using a pulsed, tunable, narrowband dye laser, nine crystallographically inequavalent sites were observed, and the fluorescence and excitation lines associated with each were identified. Concentration dependences, ion pair energy transfer, and crystal field splittings were used to classify these sites as arising from either a single charge compensated Er³⁺ ion or clustered pairs of Er³⁺ ions. At lower concentrations, the four single ion sites dominated the spectra while at higher concentrations the cluster sites weredominant. Several of these sites were found to be similar to sites previously observed in CaF₂ : Er³⁺, and several were correlated to spectra of SrF₂ : Er³⁺ published by other workers.