Branching ratio of uv and blue upconversions ofTm3+ions in glasses

Abstract

${\mathrm{Tm}}^{3+}$ doped germanate, tellurite and heavy-metal fluoride glasses were prepared and their upconversion luminescence spectra were measured to investigate the effect of the host glass on the branching ratios, β of ${}_{}{}^1{}_{}{}^{}$ ${\mathit{D}}_2$ ${\to }^3$ ${\mathit{H}}_6$ at 0.36 μm and ${}_{}{}^1{}_{}{}^{}$ ${\mathit{D}}_2$ ${\to }^3$ ${\mathit{F}}_4$ at 0.45 μm. Because the radiative emission probabilities of these electric dipole transitions are functions of Judd-Ofelt intensity parameters ${\mathrm{\Omega }}_{\mathit{t}}$ and the sets of reduced matrix elements 〈∥${\mathit{U}}^{\left(\mathit{t}\right)}$∥〉(t=2,4,6), it was possible to vary the β of both transitions. The β of 0.45 μm luminescence increases slightly with increasing ${\mathrm{\Omega }}_2$ parameter, whereas β of 0.36 μm decreased. The ratio of ${\mathrm{\beta }}_{36}$/${\mathrm{\beta }}_{45}$ was largest in a fluorozincate glass and lowest in a tellurite glass. The result could be well explained by the smaller ${\mathrm{\Omega }}_2$/${\mathrm{\Omega }}_4$ ratio in fluoride glasses than those in oxide glasses. The correlation between the luminescence intensity ratio and the ${\mathrm{\Omega }}_{\mathit{t}}$ parameters shows that we can control the branching ratio by the ligand field design for ${\mathrm{Tm}}^{3+}$ in glass matrices. © 1996 The American Physical Society.