Evaluation of spectroscopic properties ofYb3+-doped glasses

The absorption and emission properties of numerous glasses doped with ${\mathrm{Yb}}^{3+}$ ions have been investigated. The emission cross sections have been evaluated using the measured absorption spectra and principle of reciprocity, and again using the Fuchtbauer-Ladenburg formula. Agreement between the two methods is typically within 25% for most materials. The spectroscopic properties of the ${}_{}{}^2{}_{}{}^{}F_{\frac{7}{2}}^{}{}_{}{}^{}-{}_{}{}^2{}_{}{}^{}F_{\frac{5}{2}}^{}{}_{}{}^{}$ transition have been found to be very sensitive to the ${\mathrm{Yb}}^{3+}$ site environment as well as an hypersensitive transition, and their values increase as the asymmetry of the ${\mathrm{Yb}}^{3+}$ site becomes higher. High asymmetry of the ${\mathrm{Yb}}^{3+}$ site is essentially caused not only by large difference in the cationic field strengths between network formers around the [Yb${\mathrm{O}}_6$] coordination sphere, but also by difference in the coordination numbers of oxygens surrounding network formers that are associated with the ${\mathrm{Yb}}^{3+}$ through the oxygens. A system of $\mathrm{Yb}:(15-25)\mathrm{}{\mathrm{P}}_2{\mathrm{O}}_5-(10-20)\mathrm{}{\mathrm{Nb}}_2{\mathrm{O}}_5-(0-15)\mathrm{}{\mathrm{B}}_2{\mathrm{O}}_3-(48-55)R\mathrm{O}$ ($R=\mathrm{M}\mathrm{g},\mathrm{C}\mathrm{a},\mathrm{S}\mathrm{r},\mathrm{B}\mathrm{a},\mathrm{a}\mathrm{n}\mathrm{d}\mathrm{Z}\mathrm{n}$) glasses which possess higher asymmetry of ${\mathrm{Yb}}^{3+}$ ligands has been developed. These glasses exhibit the most useful laser properties, and are expected to be substantially superior to Yb: Si${\mathrm{O}}_2$ and Yb: ZBLAN glass fiber lasers in many key spectroscopic parameter values.