Temperature-dependent concentration quenching and site-dependent effects ofNd3+fluorescence in fluorophosphate glasses

The optical properties and temperature-dependent concentration quenching of ${\mathrm{Nd}}^{3+}$ fluorescence have been investigated in fluorophosphate glasses with different fluorine to oxygen ratios by using steady-state and time-resolved laser spectroscopy. Judd-Ofelt parameters were derived from the absorption spectra and used to calculate the ${}_{}{}^4{}_{}{}^{}F_{\frac{3}{2}}^{}{}_{}{}^{}\to {}_{}{}^4{}_{}{}^{}I_{\frac{11}{2}}^{}{}_{}{}^{}$ stimulated emission cross section and the ${}_{}{}^4{}_{}{}^{}F_{\frac{3}{2}}^{}{}_{}{}^{}$ radiative lifetime. For the samples doped with 1 wt% of ${\mathrm{Nd}}_2$ ${\mathrm{O}}_3$ the lifetimes were found to be linear dependent on the fluorine to oxygen ratio. From the thermal behavior of lifetimes, a linear temperature dependence for the nonradiative Nd-Nd relaxation processes has been found in the 4.2-100 K temperature range for samples with a molar fluorine to oxygen ratio of 6.04 doped with more than 1 wt% of ${\mathrm{Nd}}_2$ ${\mathrm{O}}_3$, which is in agreement with a one-phonon-assisted process. In order to investigate the influence of the local coordination ions on the optical properties of rare earths in these fluorophosphate glasses, fluorescence line-narrowing spectroscopy on ${\mathrm{Eu}}^{3+}$ has been performed. The influence of the local coordination ions on the optical properties of ${\mathrm{Eu}}^{3+}$ in these fluorophosphate glasses shows the existence of a clear crossover between the behavior of fluorinelike and oxygenlike coordination anions.