Measurements of the spectroscopic and energy transfer parameters for Er^3+-doped and Er^3+, Pr^3+-codoped PbO–Bi_2O_3–Ga_2O_3 glasses

Measurements of the absorption and emission spectra and the characteristics of the luminescent decay of the ${ }^4{I}_{11/2}$ and ${ }^4{I}_{13/2}$ energy levels of ${\mathrm{Er}}^{3+}$ are presented for ${\mathrm{Er}}^{3+}$ singly doped and ${\mathrm{Er}}^{3+},$ ${\mathrm{Pr}}^{3+}$-codoped $\mathrm{PbO}–{\mathrm{Bi}}_2{\mathrm{O}}_3–{\mathrm{Ga}}_2{\mathrm{O}}_3$ (PBG) glasses. The absorption cross sections were determined after accurate measurement both of glass component concentrations by use of electron probe analysis and of glass density. The characteristics of the luminescent decays were determined after direct pumping of the ${ }^4{I}_{11/2}$ and ${ }^4{I}_{13/2}$ energy levels of singly doped ${\mathrm{Er}}^{3+}$ PBG glass with a tunable pulsed optical parametric oscillator for calculation of the macroscopic rate parameters $(W_{\mathrm{ETU}})$ for energy transfer upconversion (ETU) for these energy levels. The values for $W_{\mathrm{ETU}}$ relevant to the ${ }^4{I}_{11/2}$ energy level were measured to be greater than the $W_{\mathrm{ETU}}$ values relevant to the ${ }^4{I}_{13/2}$ energy level within the range of ${\mathrm{Er}}^{3+}$ concentrations studied. The macroscopic rate parameter $(W_{\mathrm{Er}-\mathrm{Pr}})$ for energy transfer to the ${\mathrm{Pr}}^{3+}$ deactivator ion from the ${ }^4{I}_{13/2}$ energy level was also determined for a range of ${\mathrm{Pr}}^{3+}$ concentrations and for two fixed ${\mathrm{Er}}^{3+}$ concentrations. From a measurement of the energy-level lifetimes it was established that the rate of energy transfer from the ${ }^4{I}_{13/2}$ energy level to ${\mathrm{Pr}}^{3+}$ is greater than the corresponding rate of energy transfer from the ${ }^4{I}_{11/2}$ level to both the ${\mathrm{Pr}}^{3+}$ ion and the OH impurity. The overall results suggest that, to maximize the population inversion on the ${ }^4{I}_{11/2}{\to }^4{I}_{13/2}\sim 3 \mathit{\mu }\mathrm{m}$ transition, deactivation of the ${ }^4{I}_{13/2}$ level by way of small amounts of ${\mathrm{Pr}}^{3+}$ will be effective.