Characterization of Yb3+ clusters in silica glass preforms

The aim of this study is the optimisation of Yb doped silica preforms which are used for the realization of high power laser fibres. A spectroscopic study has thus been carried on using a stable setup conducing to quantify in the same time the Yb3+ emission in the visible and in the infrared spectral ranges. In this way, the impact of the Al ions on the silica solubility as well as the low Yb3+ doping levels reachable when the silica preforms are simply doped with Yb ions, have been clearly put in evidence.