Improvement of Er emissions in oxyfluoride glass ceramic nano-composite by thermal treatment

In order to improve the 1.53 μm emission of Er³⁺-doped oxyfluoride glass ceramic containing CaF₂ nano-crystals, series of samples with same Er³⁺ doping lever thermal treated under different conditions were prepared. The UV-VIR-NIR absorption spectra, near-infrared and up-conversion emission spectra, and ⁴I_13/2 decay curves were measured. Based on Judd-Ofelt theory, the radiative transition probability, fluorescence branching ratio and radiative decay time of various metastable transitions of precursor glass and glass ceramics were evaluated. With the increasing of heating temperature, the Judd-Ofelt intensity parameter Ω₂ monotonously decreased from 4.39×10⁻²⁰ to 2.72×10⁻²⁰ cm²; the emission lifetime and quantum efficiency significantly increased from 5.9 to 8.0 ms and 70% to 98%, respectively. The wavelength dependence of gain cross-sections of oxyfluoride glass and glass ceramics were computed to be relatively flat in the range of 1530-1565 nm for population inversion from 0.7 to 1.0.