Luminescence characterization of Sm3+-doped sodium potassium borate glasses for laser application

Sodium potassium borate glasses doped with different concentrations of Sm3+ ions (NKBSm) were prepared using a normal melt quench technique. Optical absorption, excitation, emission and emission decay measurements were performed to understand visible luminescence and lasing potentialities of the prepared glasses. The bonding parameters (δ) have been estimated from the absorption spectra to know about the bonding nature between Sm3+ ions and nearby ligands. The Judd-Ofelt (J-O) intensity parameters (Ωλ, λ = 2, 4, and 6), acquired from the experimental oscillator strengths of the absorption spectral features were used to estimate different radiative properties of the fluorescent transitions, 4G5/2→6HJ, J=5/2, 7/2, 9/2 and 11/2, of Sm3+ ions in NKBSm glasses to get knowledge about the potentiality of these materials as visible lasers. The asymmetric ratios (O/R) were calculated to know the local disorder of Sm3+ ions in the glass network. The experimental lifetimes (τexp) for 4G5/2 emission state were found to be decreasing with increasing Sm3+ ion concentration owing to energy transfer. The quantum efficiency (η) of NKBSm10 glass has been measured by coupling the experimental lifetime (τexp), measured from the decay profiles with radiative lifetimes (τR), obtained from J-O theory. The strong visible emission, large stimulated emission cross-section (σe), high branching ratios (βR) and good quantum efficiency (η) were observed for the most intense transition 4G5/2 → 6H7/2 (orange) in NKBSm10 glass, indicating the suitability of this glass for the development of laser and photonic devices operating in visible region.