| Summary: | Borogermanate glasses singly doped with Dy<sup>3+</sup> ions were synthesized and then studied using the absorption and luminescence spectra. Spectroscopic changes of Dy<sup>3+</sup> ions have been examined for compositional-dependent glasses with various molar ratios GeO<sub>2</sub>:B<sub>2</sub>O<sub>3</sub>. In this work, several spectroscopic parameters of Dy<sup>3+</sup> ions were obtained experimentally and compared to the calculated values from the Judd–Ofelt theory. Luminescence spectra measured for borogermanate glasses consist of blue, yellow and red bands, which correspond to <sup>4</sup>F<sub>9/2</sub> → <sup>6</sup>H<sub>15/2</sub>, <sup>4</sup>F<sub>9/2</sub> → <sup>6</sup>H<sub>13/2</sub> and <sup>4</sup>F<sub>9/2</sub> → <sup>6</sup>H<sub>11/2</sub> transitions of Dy<sup>3+</sup>, respectively. Luminescence lifetimes for the <sup>4</sup>F<sub>9/2</sub> excited state are reduced, whereas the stimulated emission cross-sections for the most intense <sup>4</sup>F<sub>9/2</sub> → <sup>6</sup>H<sub>13/2</sub> yellow transition of Dy<sup>3+</sup> increase with increasing GeO<sub>2</sub> and decreasing B<sub>2</sub>O<sub>3</sub> concentrations in glass-hosts. Quantum efficiency of the <sup>4</sup>F<sub>9/2</sub> (Dy<sup>3+</sup>) excited state is nearly independent on molar ratios GeO<sub>2</sub>:B<sub>2</sub>O<sub>3</sub>. Attractive spectroscopic properties related to the <sup>4</sup>F<sub>9/2</sub> → <sup>6</sup>H<sub>13/2</sub> transition of Dy<sup>3+</sup> ions are found for borogermanate glasses implying their potential utility for yellow laser action and solid-state lighting technology.
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