Spectroscopic and radiative properties of Sm3+-doped K–Mg–Al phosphate glasses

Abstract

Sm3+-doped K–Mg–Al phosphate glasses were prepared and characterized through various spectroscopic techniques such as optical absorption, excitation, photoluminescence spectra and decay rate analysis at room temperature to derive spectroscopic and radiative properties of Sm3+ ions in these glasses. Energy parameters for the 4f5 electronic configuration of Sm3+ ion in K–Mg–Al phosphate glass have been determined using free-ion Hamiltonian model. Judd–Ofelt (JO) analysis has been applied to evaluate the JO intensity parameters, Ωλ (λ=2, 4 and 6), and in turn radiative properties such as radiative transition probability, branching ratio, radiative lifetime and peak stimulated emission cross-section for the fluorescent 4G5/2 level of Sm3+ ion have been determined. The fluorescence decay rates exhibit single exponential at lower concentrations (≤0.1mol%) and turn into non-exponential at higher concentrations (≥0.5mol%). The experimental lifetime for the 4G5/2 level as a function of Sm3+ ions concentration decreases from 2.77 to 0.74ms when the concentration is increased from 0.05 to 2.0mol% of Sm2O3 due to energy transfer process. The non-exponential decay rates are well-fitted to Inokuti–Hirayama model for S=6 indicating that the nature of the energy transfer process is of dipole–dipole type. The systematic analysis on decay rates indicates that the energy transfer mechanism depends on Sm3+ ion concentration as well as glass composition.