Effect of Ga2O3 on the spectroscopic properties of erbium-doped boro-bismuth glasses

The spectroscopic properties and thermal stability of Er3+-doped Bi2O3–B2O3–Ga2O3 glasses are investigated experimentally. The effect of Ga2O3 content on absorption spectra, the Judd-Ofelt parameters Ωt (t = 2, 4, 6), fluorescence spectra and the lifetimes of Er3+:4I13/2 level are also investigated, and the stimulated emission cross-section is calculated from McCumber theory. With the increasing of Ga2O3 content in the glass composition, the Ωt (t = 2, 4, 6) parameters, fluorescence full width at half maximum (FWHM) and the 4I13/2 lifetimes of Er3+ first increase, reach its maximum at Ga2O3 = 8 mol.%, and then decrease. The results show that Er3+-doped 50Bi2O3–42B2O3–8Ga2O3 glass has the broadest FWHM (81 nm) and large stimulated emission cross-section (1.03 × 10−20 cm2) in these glass samples. Compared with other glass hosts, the gain bandwidth properties of Er3+-doped Bi2O3–B2O3–Ga2O3 glass is better than tellurite, silicate, phosphate and germante glasses. In addition, the lifetime of 4I13/2 level of Er3+ in bismuth-based glass, compared with those in other glasses, is relative low due to the high-phonon energy of the B–O bond, the large refractive index of the host and the existence of OH− in the glass. At the same time, the glass thermal stability is improved in which the substitution of Ga2O3 for B2O3 strengthens the network structure. The suitability of bismuth-based glass as a host for a Er3+-doped broadband amplifier and its advantages over other glass hosts are also discussed.