Er3+ doped calcium fluoroborate glasses for fiber amplifiers

Calcium fluoroborate glasses doped with Er₂O₃ (CFBEr) were prepared by the conventional melt quenching technique with molar compositions of (42-x) B₂O₃ + 20 CaF₂ + 15 CaO + 15 BaO + 8 Al₂O₃ + x Er₂O₃ (x = 0.05, 0.1, 0.5, 1.0, 2.0 and 4.0). Optical absorption spectrum in the region 250-2500 nm was recorded by using UV-Vis-NIR spectrophotometer for 1.0 mol % Er₂O₃ doped CFBEr10 glass. The absorption spectrum revealed thirteen absorption bands corresponding to transitions originating from ground (⁴I_15/2) state of erbium ions to various excited states. Judd-Ofelt (J-O) analysis has also been carried out from the experimental oscillator strengths (f_exp) to evaluate the JO intensity parameters (Ω₂, Ω₄ and Ω₆) and the calculated oscillator strengths (f_cal). Radiative parameters like radiative transition probabilities (A_R), total radiative transition probabilities (A_T), branching ratios (β_R) and radiative lifetimes (τ_R) were calculated for different excited states of Er³⁺ ion in CFB glasses. McCumber theory has been adapted to predict the emission cross-section of the NIR emission peak (⁴I_13/2 → ⁴I_15/2) at 1.53 μm. NIR luminescence spectra were recorded for all the glasses by exciting the samples with 980 nm diode laser and compared with that of the predicted emission cross-section. Variation of intensity as well as FWHM of the NIR emission transition has been studied for the utilization of these glasses in fiber amplifiers.