Evidence of enhanced hypersensitive transition in erbium-doped fibers with different Al2O3 content

Precise spectroscopic absorption measurements of erbium-doped aluminosilicate fibers with different Al₂O₃ content were performed with the Judd-Ofelt analysis. From the Judd-Ofelt analysis, the Ω₂ parameters of Er³⁺ ions in these fibers were found to be about three times as large as those in aluminosilicate bulk glasses. The enhancement of the Ω₂ parameters led to much stronger line strength of hypersensitive transitions in a fiber form than in a bulk glass form. This indicates that the distortion of the ligand field around the Er³⁺ ions are more enhanced in a fiber form than in a bulk glass form. Furthermore, the Ω₆ and the Ω₂ parameters increased with an increase of q content up to 20 000 ppm. This Al₂O₃-content dependence of the Ω₆ parameter was consistent with that of the line strength and the spontaneous emission probabilities of the transition corresponding to the ⁴I₁₃2/→⁴I₁₅2/.