Spectroscopic and structural investigations of Er~(3+) doped zinc bismuth borate glasses

摘要

Erbium doped glasses having composition 20ZnO xBi_2O_3(79.5 - x)B_2O_3 (15 ≤ x ≤ 35, x in mol%) were prepared by melt-quench technique. The spectroscopic properties were investigated using optical absorption and fluorescence spectra. The Judd-Ofelt intensity parameters, Ω_λ (λ = 2,4,6) were determined from the spectral intensities of absorption bands in order to calculate the radiative transition probability (A_R), radiative life time (τ_R), branching ratio (β_R) for various excited luminescent states. Using the emission spectra, full width at half maximum (FWHM), stimulated emission cross-section (σ_e) and figure of merit [F0M] were evaluated. The high values of Judd-Ofelt parameters indicate a substantial mixing of other electronic configuration into the 4f~N configuration by the random crystal field in the glasses. All the intensity parameters (Ω_λ) decrease with increase in Bi_2O_3 content and the effect is found to be most pronounced for Ω_2 values. The structural investigations of the glasses were carried out by recording the IR transmission spectra. A correlation between the network forming units with the multi-phonon relaxation rate and hence with the possibility of radiative quantum efficiency has been made. In addition, various physical and optical parameters have been determined from the measured density and refractive index values.