Spectroscopic and photoluminescence properties of Sm3+ ions in Pb-K-Al-Na phosphate glasses for efficient visible lasers

The Sm3+-doped lead phosphate glasses (PKAPbNSm:44P2O5-17K2O-9Al2O3-(24−x) PbO-6Na2O-xSm2O3, where x=0.1, 0.5, 1.0 and 2.0 mol%) have been prepared by conventional melt quenching technique and are characterized through absorption and emission spectra and decay rate analysis. The partial energy level structure of Sm3+ ions in these glasses have been evaluated from the measured absorption and emission spectra using free-ion Hamiltonian model. The emission spectra of Sm3+ ions in these glasses have been measured using 488 nm line of Ar+ laser as an excitation source. The decay rates for 4G5/2 level of Sm3+ ions have been measured and are found to exhibit single exponential nature at lower concentration (0.1 and 0.5 mol% Sm2O3-doped glass) and turns into non-exponential at higher concentrations (≥1.0 mol% Sm2O3-doped glasses). The experimental lifetimes for 4G5/2 level of Sm3+ ions are found to decrease from 2.34 to 1.24 ms when the concentration is increased from 0.1 to 2.0 mol% Sm2O3 due to cross-relaxation energy transfer. The non-exponential decay rates are well-fitted to Inokuti-Hirayama model for S=6, indicates that the energy transfer is of dipole-dipole type.