Spectral analysis of RE³⁺ (RE = Er, Nd, Pr and Ho):GeO ₂-B₂O₃-ZnO-LiF glasses

This paper reports on the absorption, visible and near-infrared luminescence properties of Er³⁺, Nd³⁺, Pr³⁺ and Ho³⁺-doped alkali fluoride zinc boro germanate glasses. The x-ray diffraction (XRD) and differential thermal analysis (DTA) profiles of the host glass have been carried out, to confirm its structure and thermal stability. From the measured absorption spectra, Judd-Ofelt (JO) intensity parameters (Ω₂, Ω₄ and Ω₆) have been calculated for all the studied ions. For Pr³⁺ and Ho ³⁺-doped glasses, upconversion emission spectra have also been measured. Decay curves were measured for the visible emissions of Er ³⁺, Pr³⁺ and Ho³⁺ ions at 547nm (Er ³⁺:green), 604nm and 641nm (Pr³⁺:orange and red) and 658nm (Ho³⁺:red), respectively. The near-infrared emission spectra of Er³⁺/Yb³⁺ and Nd³⁺-doped glasses have shown full width at half maximum (FWHM) around 95nm (for the transition) and 63nm (for the transition), respectively. The measured maximum decay times of transition (at wavelength 1.51νm) are about 5.72ms and 6.14ms for 1.0Er³⁺ and 1.0Er³⁺/ 2Yb³⁺(mol%)-codoped glasses, respectively. The maximum stimulated emission cross sections for transition of Er³⁺ and Er³⁺/Yb³⁺ are 5.447 × 10^-21cm ² and 4.540 × 10^-21cm². These glasses with better thermal stability, bright visible emissions and broad near-infrared emissions should have potential applications in broadly tunable laser sources, interesting optical luminescent materials and broadband optical amplification in low-loss telecommunication windows.