Rare earths in lead-free oxyfluoride germanate glasses

• Rare earth-doped lead-free germanate glasses modified by BaF2 were prepared.
• Luminescence intensity ratio R/O (Eu3+) is reduced with increasing BaF2 content.
• Hypersensitive transitions of Pr3+ and Er3+ are blue shifted with increasing BaF2 content.
• Near-infrared luminescence of Er3+ for glass samples with low BaF2 content is long-lived.

Spectroscopic properties of rare earths in lead-free oxyfluoride germanate glasses were studied. The absorption and luminescence spectra of Eu3+, Pr3+ and Er3+ ions were examined as a function of BaF2 concentration and several spectroscopic parameters for rare earths were determined. The ratio of integrated luminescence intensity of the 5D0 → 7F2 transition to that of the 5D0 → 7F1 transition of Eu3+ decrease significantly with increasing BaF2 content. The absorption (Er3+) and emission (Pr3+) ‘hypersensitive transitions’ of rare earths are shifted in direction to shorter wavelengths with increasing BaF2 content in glass composition. Emission spectra and their decays corresponding to the main 4I13/2 → 4I15/2 laser transition of Er3+ were also analyzed. Quite long-lived NIR luminescence of Er3+ is observed for lead-free glass samples with low BaF2 concentration.

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