Structural and fluorescence properties of Ho3+/Yb3+ doped germanosilicate glasses tailored by Lu2O3

Highlights: • Structural and fluorescence properties of germanosilicate glasses were researched. • The addition of Lu₂O₃ increases ΔT to improve the thermal stability of glass host. • The increase of NBO can decrease the cross relaxation effect among RE-RE ions. • Fluorescence properties of Ho³⁺ have been improved due to the increase of NBO. Structural and fluorescence properties of Ho³⁺/Yb³⁺ co-doped germanosilicate glasses have been modified by tailoring the composition using lanthanide additive Lu₂O₃. Raman spectra and X-ray Photoelectron spectra reveal that the addition of Lu₂O₃ can change the structure by increasing non-bridging oxygens (NBO) in this glasses. Meanwhile, an improved thermal stability (ΔT: from 110 to 187 °C) has also been obtained via Lu³⁺ 'lanthanide contraction'. Futhermore, the positive effect of changed glass structure gives excellent fluorescence properties by the decreasing cross relaxation process which are proved by the experimental upconversion, near-infrared and mid-infrared fluorescence spectra. Additionally, a double enhancement of a 2.0 μm emission has been achieved successfully in this silica-germanate glass with 7 mol% Lu³⁺ addition, which possesses a larger emission cross section (4.41 × 10⁻²¹ cm²) at 2022 nm. These results indicate that the optimized emission of Ho³⁺ for optical fiber laser can be achieved by tuning the glass structure using lanthanide additive Lu₂O₃.