Structural and luminescence behavior of the Er3 + doped alkali fluoroborate glasses

Er3 + doped alkali fluoroborate glasses B2O3 + xCO3 + NaF + Er2O3 (where x = Li2, Na2, K2, Ca and Mg) have been prepared by following a conventional melt quenching technique. The prepared glasses were investigated through X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), optical absorption and luminescence measurements made at room temperature. The fundamental stretching vibrations of BO3 and BO4 structural units in the borate network have been explored through the FTIR spectra. Absorption spectra of the glasses recorded in the ultraviolet–visible region suggest the ionic/covalent nature of the prepared glasses. Oscillator strengths were obtained for the observed absorption transitions. Judd–Ofelt (JO) theory was used to calculate the intensity parameters Ωλ to analyze the bonding of the Er3 + ions with its surrounding ligands. The JO parameters have been used to determine the various radiative parameters like transition probabilities (A), stimulated emission cross-section (σPE), radiative lifetimes (τrad) and branching ratios (βR) for the 2H9/2 → 4I15/2 and 2H11/2 + 4S3/2 → 4I15/2 excited levels of the Er3 + ions in the alkali fluoroborate glasses and these results were compared with literature on Er3 +:glasses reported earlier. Davis and Mott theory has been used to determine the optical band gap energy (Eopt) corresponding to the direct and indirect transitions along with the Urbach energy (ΔE) values for the title glasses. The spectroscopic properties of the prepared glasses have been studied by varying the alkali/alkaline earth elements and the results were discussed and compared with those reported in the literature.

► The higher fexp & fcal of the hypersensitive transitions confirm the lower asymmetry.
► The higher Ω2 JO parameter value further confirms the lower asymmetry.
► Higher σPE, βR values for the BLNEr glass are suitable for green laser applications.
► The variations in the Eopt, ΔE values are due to the change in alkali/alkaline oxides.