Enhanced 3 μm emission in Ho3+/Yb3+ co-doped bismuth-fluoride glasses by Gd2O3

In this work, (100-b)(45Bi ₂O ₃-40GeO ₂-15BaF ₂)-bGd ₂O ₃-2Yb ₂O ₃-0.5Ho ₂O ₃ glass was prepared to use a high-temperature melting method(where b= 0, 2.5, 5, 7.5, 10). The absorption and fluorescence spectra indicate that the optimal Gd ₂O ₃ content is 7.5 mol% (BGBG7.5HY), with an Ω ₂ value of 6.20×10 ⁻²⁰ cm ² for the main glass, which is superior to that of BGBG0HY glass. This suggests that the incorporation of Gd ₂O ₃ enhances the mid-infrared emission capacity. Raman spectroscopy studies demonstrate that the introduction of Gd₂O₃ results in a substantial influx of oxygen atoms into the glass network, accompanied by a transition of [BiO₆] to [BiO₃] within the glass mesh. This is evidenced by a notable redshift of the characteristic peaks at 509 cm ⁻¹ and 677 cm ⁻¹ in comparison to BGB glass. The introduction of Gd ₂O ₃ also expands the distance between Ho ³⁺/Yb ³⁺ ions, inhibits rare earth ion clusters, improves the Ho ³⁺ luminescence center environment, and thus enhances the 3 μm emission performance of bismuth fluoride glass. The maximum emission cross section is 1.82 × 10 ⁻²⁰ cm ² and the maximum gain coefficient is 3.71 cm ⁻¹. The results show that the bismuth fluoride glass prepared in this paper is an excellent gain material for mid-infrared fiber lasers.