Optical properties of ${\mathrm{Cr}}^{3+}$ and ${\mathrm{Nd}}^{3+}$ in singly- and doubly-doped barium-indium-gallium-based fluoride glass investigated by time-resolved laser spectroscopy

The optical properties of ${\mathrm{Cr}}^{3+\mathrm{-}}$, ${\mathrm{Nd}}^{3+\mathrm{-}}$, and ${\mathrm{Cr}}^{3+}$:${\mathrm{Nd}}^{3+\mathrm{-}}$doped fluoride glass (${30\mathrm{B}\mathrm{a}\mathrm{F}}_{2\mathrm{-}}$ ${18\mathrm{I}\mathrm{n}\mathrm{F}}_{3\mathrm{-}}$ ${12\mathrm{G}\mathrm{a}\mathrm{F}}_{3\mathrm{-}}$ ${20\mathrm{Z}\mathrm{n}\mathrm{F}}_{2\mathrm{-}}$ ${10\mathrm{Y}\mathrm{F}}_{3\mathrm{-}}$ ${6\mathrm{T}\mathrm{h}\mathrm{F}}_{4\mathrm{-}}$ ${4\mathrm{Z}\mathrm{r}\mathrm{F}}_4$) have been investigated in the 4.2–300-K temperature range at several concentrations by using steady-state and time-resolved laser spectroscopy. The luminescence of trivalent chromium in singly-doped glass shows a strong thermal quenching and can be analyzed on the basis of two broad statistical site distributions. The luminescence quenching of the ${}_{}{}^4{}_{}{}^{}$ ${\mathit{F}}_{3/2}$ ${\to }^4$ ${\mathit{I}}_{11/2}$ laser transition of ${\mathrm{Nd}}^{3+}$ in singly-doped glass has been studied by investigating the thermal and concentration dependence of lifetimes. A ${\mathit{T}}^3$ dependence for the nonradiative ${\mathrm{Nd}}^{3+\mathrm{-}}$ ${\mathrm{Nd}}^{3+}$ relaxation has been found in the 15–100-K temperature range at high ${\mathrm{Nd}}^{3+}$ concentrations, which is in agreement with a two-site nonresonant process. ${\mathrm{Cr}}^{3+}$-to-${\mathrm{Nd}}^{3+}$ radiative and nonradiative energy transfer in codoped glass has been demonstrated from the emission spectra and the decrease of ${\mathrm{Cr}}^{3+}$ fluorescence lifetimes. The comparison between the time-resolved emission spectra of