New optical materials based on rare-earth doped oxyfluoride glasses and ceramics: structural and photophysical studies

Full text: The development of new solid state laser hosts for high optical quality rare-earth ion doped crystals, glasses, and ceramics remains an active area of materials research. There is a strong demand nowadays for active optical devices to be used in telecommunications. To facilitate the design of materials with optimized emission properties, detailed structural information at the atomic level is essential, regarding the local bonding environment (siting) of the rare earth ions, their second-nearest coordination sphere, and their extent of local clustering, as well as the distribution over separate micro- or nanophases in composite materials. An interesting host composition is based on glassy and ceramic fluorophosphate, which combines the advantages of fluoride and oxide glasses. Fluoride glass matrices in general present low phonon energy and low refractive index and wide optical windows while the phosphate glasses have higher mechanical and chemical stability fluoride glasses. Synergy associated with fluorophosphate matrices can be accomplished under the condition that the local environments are chemically ordered such that the short range order of the rare-earth emitter species is dominated by fluoride. To explore this question, detailed structural investigations are necessary. In this work, we explore the thermal, structural and photophysical properties of melt-prepared fluorophosphate glasses along the compositional series [80Ba(PO₃)₂-20Al(PO₃)₃]_x [80BaF₂-20AlF₃]_1-x (with x =0; 0,25 and 0,75), doped with variable amounts of Er³⁺, Yb³⁺ and Eu⁺³. Glasses are characterized by DSC, XRD, Raman spectroscopy, optical absorption and emission, excited state life time. In addition, important structure/properties relations are obtained from detailed multinuclear solid state ³¹ P, ¹⁹F, and ²⁷Al single- and double resonance NMR studies. These results indicate the potential of these glasses for photonic applications. (author)