| Scope and Method of Study. The objectives of this study are to investigate the optical properties of impurity ions in two fluoride hosts, crystalline RbMgF(,3) and fluorozirconate glass. The impurity ions are Er('3+), Eu('2+), and Mn('2+) in the crystalline host, and Er('3+) in the glass. Optical absorption, emission, and excitation spectra, as well as fluorescence lifetime measurements were used to study the effects of the surroundings on the impurities.;Energy transfer is shown to occur from Eu('2+) ions to Mn('2+) ions in RbMgF(,3):Eu,Mn. Integrated intensity and lifetime measurements, as well as comparison of calculated and measured energy transfer rates suggest that Eu('2+) ions pair with Mn('2+) ions. This pairing is greater than expected for a statistical distribution, and does not appear to be due to precipitates. This pairing most likely occurs to reduce the strain in the RbMgF(,3) lattice, which results from the introduction of either impurity alone, which suggests that this same process can occur for other sensitizer-activator combinations with the appropriate ionic radii.;Emission lifetimes for some transitions of Er('3+) ions in RbMgF(,3):Mn were much faster than normally observed and were quenched by 150 K, which is also unusual. This behavior is indicative of energy transfer. Absorption data for the two types of crystals indicate that Er('3+) ions are in two noncubic sites, most likely the two nonequivalent Mg('2+) sites. The Er('3+) ions in one site fluoresced in RbMgF(,3); in both sites in RbMgF(,3):Mn. These data, along with annealing studies, indicate that clustering of Er('3+) ions, possibily facilitated by the addition of Mn('2+), occurs.;Findings and Conclusions. Lifetimes of the Er('3+) emissions in the glass were measured over the temperature range 6-520K. The radiative rates for these transitions were calculated using the Judd-Ofelt theory and measured oscillator strengths. Differences between calculated and measured rates were due to multiphonon emission. The temperature dependence of this nonradiative process was in agreement with the behavior predicted by the Huang-Rhys theory, for coupling with the highest energy phonons. The near-exponentiality of the lifetimes indicate that site variations for this glass are small compared to oxide glasses. |
