Investigations on the physical, structural, optical and photoluminescence behavior of Er3+ ions in lithium zinc fluoroborate glass system

Family of lithium zinc fluoroborate glasses with 15ZnF(2)-10BaO-8Al(2)O(3)-12Li(2)O-(55-x) B2O3-xEr(2)O(3) (x = 0.5, 0.7, 1.1, 1.3 and 1.5 mol%) composition were prepared by conventional melt-quench method. The glasses were characterized to study their structural, physical, optical and radiative properties. The amorphous characteristic of glass was noticed in X-Ray Diffraction pattern. A modification in structure was observed as density values increased with Er2O3 content. UV-Vis-NIR transitions of Er3+ in the host matrix were identified through absorption spectra. Covalent nature of bonding between Er3+ ions and their surrounding ligands was observed through bonding parameter and Judd-Ofelt parameters. Red shift of the fundamental absorption edge in the absorption spectra and decreasing indirect and direct band gaps with increasing Er3+ concentration jointly confirmed the role of Er3+ ions as network modifier. Hypersensitive transitions of Er3+ ion namely I-4(15)/2 -> H- 2(11)/2 & I-4(1)5/2 -> (4)G(11)(/2) were interpreted through their higher oscillator strengths when compared to other transitions. Emission spectra recorded at 980 nm excitation showed a peak corresponding to I-4(13)/2 -> I-4(15/2) NIR transition of erbium ion. Stimulated emission cross section of Er0.5 sample, gain bandwidth and Figure of Merit were found to be 16.79 x 10(-21) cm(2), 1225.83 x 10(-28) cm(3) and 37.36 x 10(-24) cm(2) s respectively. Photoluminescence decay curve of Er0.5 sample was well-fitted to single exponential first order function. The experimental decay lifetime tau(exp) for the I-4(13/2) level was measured to be 0.34 ms. The wide frequency range of FWHM (1.02-1.67 x 10(13) Hz) and high values of radiative parameters make the glass a suitable candidate as optical amplifier and NIR laser material.