Absorption and emission spectral studies of Sm3+ and Dy3+ ions in PbO-PbF2 glasses

The optical properties of lanthanide ions, Sm3+ and Dy3+ doped in the PbO-PbF2 oxyfluoride glass matrix are similar to those of fluoride glasses as shown by the Judd-Ofelt parameters and emission spectral properties. The stimulated emission cross-sections (ob) indicative of potential for lasers have been obtained. They are an order of magnitude less than the values reported for transitions in other rare earth ions. For Dy3+ sigma(p) is found to be the highest (sigma(p) x 10(24) cm(2) = 1191 +/- 60) for the hypersensitive transition F-4(9/2) --> H-6(13/2). This transition also has the largest transition probability (A = 390 +/- 12 s(-1)) and branching ratio (beta(R) = 0.608 +/- 0.024) signifying most favored emission. The ratio (yellow/blue) of its intensity relative to the non-hypersensitive electric dipole transition is affected by the nature of the glass matrix and has the value of 1.58 +/- 0.02 for our glass sample. The quantum efficiencies for (4)G(5/2) of Sm3+ (0.2 wt%) and for F-4(9/2) of Dy3+ (0.2 wt%) are 52 +/- 2 and 49 +/- 2%, respectively. The fluorescent decay processes for both the ions follow single exponential at lower concentrations (0.2 wt%). At larger dopant concentrations (1.35 wt%) while Dy3+ exhibits a single exponential decay, Sm3+ does not, since energy transfer involving cross-relaxation becomes significant in the radiative decay process. Our studies show that for some applications oxyfluoride glasses can be a better substitute for fluoride glasses. (C) 1997 Elsevier Science B.V.