Role ofEr3+concentration in high-resolution spectra ofBaY2F8single crystals

Abstract

Fourier transform absorption spectroscopy with a resolution as fine as $0.02\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ was applied to ${\mathrm{Er}}^{3+}$-doped monoclinic ${\mathrm{BaY}}_{2}{\mathrm{F}}_{8}$ laser crystals in a wide wave number range $(500--24\phantom{\rule{0.2em}{0ex}}000\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1})$ and in the temperature range 9--300 K. The careful analysis of the complex narrow line spectra induced by ${\mathrm{Er}}^{3+}$ allowed us to determine with high accuracy the crystal field splitting of the fundamental $^{4}\mathrm{I}_{15∕2}$ and of the excited $^{4}\mathrm{I}_{13∕2}$, $^{4}\mathrm{I}_{11∕2}$, $^{4}\mathrm{I}_{9∕2}$, $^{4}\mathrm{F}_{9∕2}$, $^{4}\mathrm{S}_{3∕2}$, $^{2}\mathrm{H}_{11∕2}$, $^{4}\mathrm{F}_{7∕2}$, $^{4}\mathrm{F}_{5∕2}$, and $^{4}\mathrm{F}_{3∕2}$ manifolds. On the basis of the experimental data, the crystal-field parameters were determined and Newman's superposition model was applied: in this way a slight displacement of ${\mathrm{Er}}^{3+}$ with respect to the ${\mathrm{Y}}^{3+}$ position was foreseen. The Judd-Ofelt parameters were evaluated: the lifetime values deduced from them were compared to the experimental ones and discussed. The effects caused by increasing ${\mathrm{Er}}^{3+}$ concentrations (0.5%, 2%, 12%, and 20% atomic fraction) were studied in detail. The new lines, the line broadening, and the line-shape changes were explained in terms of ${\mathrm{Er}}^{3+}\text{\ensuremath{-}}{\mathrm{Er}}^{3+}$ interaction.