Spectral characterisation of Sm³⁺ ions doped Oxy-fluoroborate glasses for visible orange luminescent applications

Oxy-fluoroborate (OFB) glasses doped with different concentrations of Sm³⁺ ions have been prepared using conventional melt quenching technique and characterised for their lasing potentialities using spectroscopic techniques such as FTIR, optical absorption, emission and emission decay measurements. The FTIR spectrum has been recorded to determine the various functional groups present in the OFB base glass. From the absorption spectra, the bonding parameters (δ) were evaluated to find the bonding nature present between Sm³⁺ ions with its neighbouring ligands. The Judd–Ofelt intensity (J–O) parameters (Ω_λ, where λ=2, 4, and 6), measured from the experimental oscillator strengths of the absorption spectral futures, are used to evaluate the radiative parameters for the fluorescent transitions ⁴G_5/2→⁶H_5/2, ⁴G_5/2→⁶H_7/2, ⁴G_5/2→⁶H_9/2 and ⁴G_5/2→⁶H_11/2 of Sm³⁺ ions in OFB glasses. The asymmetric ratio has been evaluated to understand the local disorder of Sm³⁺ ions in the glass network. The experimental lifetimes (τ_exp) measured from the decay curves are coupled with radiative lifetimes (τ_rad) to measure quantum efficiency (η) of the prepared glasses. The experimental lifetimes (τ_exp) for ⁴G_5/2 emission state decrease with increase in Sm³⁺ ion concentration due to energy transfer. In order to elucidate the nature of energy transfer mechanism, the non-exponential decay curves are well fitted to the Inokuti–Hirayama model for S=6, which indicates that the energy transfer mechanism is of dipole–dipole type. The branching ratio (β_R), stimulated emission cross-section (σ_se) and quantum efficiency (η) values measured for the most intense emission transition ⁴G_5/2→⁶H_7/2 (598 nm) optimise the concentration of Sm³⁺ ions as 1 mol% to produce bright visible orange lasing emission from these OFB glasses. - highlights: • Sm³⁺ doped OFB glasses have been synthesised using melt quenching technique. • From the absorption spectra, J–O parameters have been calculated using the J–O theory. • Emission cross-sections and efficiencies are calculated for laser transitions. • CIE colour co-ordinates were evaluated using emission spectra. • OFBSm1.0 glass was found to be the best for laser action in the visible orange region