The influence of cation additives on the NIR luminescence intensity of Er³⁺-doped borate glasses

Er³⁺-doped 25BaO-(25-x)SiO₂-xAl₂O₃-25B₂O₃ transparent glasses are prepared with x=0, 12.5 and 25 by a solid-state reaction. The Er-related NIR luminescence intensity, which corresponds to the transition of ⁴I_15/2-⁴I_13/2, is obviously altered with different silicon/aluminum ratios. The Judd-Ofelt parameters of the Er³⁺ ions are adopted to explain the intensity change in the NIR fluorescence, and the Raman scattering intensity versus the amount of Al and/or Si components are discussed. The spectra of the three samples are quite similar in the peak positions, but different in intensity. The maximal phonon density of state for the samples is calculated from the Raman spectra and is correlated to the NIR luminescence efficiency.