Effect of radiative trapping on measurement of the spectroscopic properties of Yb3+:phosphate glasses

The effect of radiative trapping on measurement of the spectroscopic properties of Yb3+-doped phosphate glasses was investigated as a function of Yb3+ concentration at different thicknesses. It was found that radiative trapping exists generally in Yb3+:phosphate glasses, even at low concentration. As a result, the measured lifetime of Yb3+ in phosphate glasses is usually larger than the calculated one. The maximum discrepancies between them at high concentration are found to be <42%. The calculated lifetime should be used as a reference in determining the true value of the measured lifetime because of it being lengthened largely by radiative trapping. On the other hand, the shape of fluorescence spectrum exhibits remarkable changes due to the radiative trapping. What is more, the intensity increase of Δλeff at high concentration is greater than that of low doping. The Δλeff increases 36% from 53 to 72 nm with thickness increasing from 0.3 to 4 mm at 6 mol% Yb2O3 content, while Δλeff increases only 11% when Yb2O3 content was fixed at 0.2 mol%.