Optical properties of erbium-doped fluorochlorozirconate glasses

We report the optical properties of a fluorochlorozirconate (FCZ) glass with the composition 53% ZrF4, 20% NaF, 3.5% AlF3, 3% LaF3, 0.5% InF3, (20 − x)% BaCl2, x% BaF2 with x varying from 0% to 2%, and doped with various amounts of trivalent erbium by the addition of ErCl3. Annealing of the as-prepared glass in inert (N2) or reducing (5%H2 + 95%Ar) atmospheres at temperatures that ensure the conversion of the glass into a glass-ceramic by the nucleation of BaCl2 nanocrystals, does not significantly change any of Er3+ related absorption and photoluminescence (PL) characteristics. We have carried out a Judd–Ofelt analysis of the absorption spectra and obtained Ω2 = (1.92 ± 0.3) × 10− 20 cm2, Ω4 = (0.88 ± 0.16) × 10− 20 cm2 and Ω6 = (0.59 ± 0.08) × 10− 20 cm2, and also the radiative lifetimes of the 4I13/2→4I15/2, 4I11/2→4I15/2 and 4S3/2→4I15/2 bands. The radiative lifetime from the Judd–Ofelt analysis for the 4I13/2→4I15/2 band is in good agreement with the experimentally measured PL decay time. The examination of the optical properties of powdered samples with different average particle size does not show any photon trapping effects. We have determined the spectral absorption and emission cross-sections and then estimated the possible spectral optical gain for varying degrees of relative populations of the 4I13/2 and 4I15/2 manifolds.

Research Highlights► Optical and thermal properties of Sm2+-doped fluorochlorozirconate glass-ceramics are studied. ► Photoluminescence and temperature-modulated differential scanning experiments are used. ► Long duration, low temperature annealing leads to the formation of orthorhombic BaCl2 nanocrystals. ► Hexagonal nanocrystals may be obtained by a simple one step annealing process. ► Photoluminescence depends on the resulting glass-ceramic structure from various annealing steps.