Clusters dissolution of Yb3+ in codoped SiO2-Al2O3-P2O5 glass fiber and its relevance to photodarkening.

Using a combination of pulse electron paramagnetic resonance and photoluminescence spectroscopy, we demonstrate the major role of phosphorous rather than aluminium in the rare-earth dissolution process, an essential advance in telecommunication and solid laser fields. Our results also provide new insight into the micro-structural origin of the photodarkening process occurring in Yb doped fiber.