Optical properties of borate glasses containing chromium and erbium oxide

Abstract Borate glass samples containing chromium and erbium were prepared. According to the density and molar volume, the Cr 2 O 3 -free glass sample had an expanded glass structure. Cr has three distinct absorption bands, and according to the measured optical absorption characteristics, a band was observed at 688 nm due to the 4 A 2g (F) → 2 E g (G) transition, indicating the presence of Cr 6+ . Cr 3+ was observed in the bands at 446 and 620 nm, which were attributed to 4 A 2g (F) → 4 T 2g (F) and 4 A 2g (F) → 4 T 1g (F). Using the absorption spectra of the glass samples, the Judd–Ofelt theory was used to calculate the three parameters for glass: Ω2, Ω4, and Ω6. The slow transformation of chromium ions in these glasses from Cr 6+ to Cr 3+ disturbs the local symmetry and adds coordinated bond defects, which affect the surroundings of Er 3+ ions.