Controllable structural tailoring for enhanced luminescence in highly Er-doped germanosilicate glasses.

Higher concentrations of rare earth (RE) ions in glass materials would be favorable for the output of single-frequency fiber lasers. In this Letter, we adjusted the topological structure of glass networks through controlling the numbers of non-bridging oxygens (NBOs) and bridging oxygens (BOs) by tuning the composition of the glasses, hence increasing the RE doping concentration of germanosilicate glasses. The increased flexibility of the glass networks favors the distribution of clusters of RE ions to decrease fluorescence quenching, which was validated by both our experimental and theoretical results. To the best of our knowledge, for the first time, a highly Er-doped (up to 7 mol. %) heavy metal oxide glass was fabricated without quenching by tuning the components of the glass. In addition, we have demonstrated an approach to enhance the fluorescence properties of heavily RE-doped glass materials by tailoring network topology.