SITE-SELECTIVE SPECTROSCOPY OF EU(3+) IONS IN FLUORIDE GLASSES

The optical properties of two Eu3+-doped fluoride glasses with the composition (in mol%), 30BaF2-18InF3-12GaF3-20ZnF2-9.5YF3-6ThF, 4ZrF4-0.5EuF3 and 57ZrF4-18BaF2-5.5LaF3-3AlF3-15NaF-0.5EuF3 were investigated by time-resolved site-selective spectroscopy in order to correlate the glass matrix composition with the Eu3+ spectral properties. The results established the presence of two main site distributions for the Eu3+ ions. The spectral evolution of the time-resolved line-narrowed excitation spectra shows the existence of discrete energy transfer between both sites. The fluorescence-narrowed spectra of the 5D0 --> F-7(1) emission at 10 K obtained under resonant excitation show inhomogeneous broadening due to the superposition of fluorescence from the two sites. The estimated average crystal field strength for both glasses grows monotonically with the F-7(0) --> 5D0 energy in agreement with other glasses studied. The results allow us to conclude that the degree of local order is high in both glasses producing a high site symmetry for the Eu3+ ions. As a consequence, the lifetimes are longer than those observed in other glasses.