Phase separated nanoparticles in optical fibers

Optical fibres are mostly based on silica glass for its interesting properties (reliability, low cost, ...). However, some of its characteristics (high phonon energy, low solubility of luminescent ions, ...) induce drawbacks in spectroscopic properties of rare-earth (RE)-doped fibre lasers and amplifiers. Here we investigate the growing of RE-doped dielectric oxide nanoparticles (DNP) in silica-based optical fibres. Through this, we keep the optical and mechanical advantages of silica glass, and we investigate the potential of engineering of RE spectroscopic properties through the choice of the DNP chemical composition. Among various synthesis routes, we focus on spontaneous phase separation, by implementing the strong immiscibility of some glass systems when they contain divalent metals oxides, such as SrO, CaO, FeO, ZnO, and MgO. For example when a silicate glass containing few mol% of CaO is heated during the manufacture process it may decompose in two phases : one silica-rich and one CaO-rich (present as spherical particles). In this contribution, we present the preparation and characterization of fibres containing nanoparticles. The role of alkaline-earth elements (Mg, Ca and Sr) on phase separation mechanisms will be discussed.