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 Cr2O3-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 4A2g(F) → 2Eg(G) transition, indicating the presence of Cr6+. Cr3+ was observed in the bands at 446 and 620 nm, which were attributed to 4A2g (F) → 4T2g (F) and 4A2g (F) → 4T1g (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 Cr6+ to Cr3+ disturbs the local symmetry and adds coordinated bond defects, which affect the surroundings of Er3+ ions.