Local field dependent fluorescence properties of Eu3+ ions in a fluorometaphosphate laser glass

A fluorometaphosphate laser glass doped with Eu3+ ions has been synthesized and studied by broad band optical spectroscopy and time-resolved fluorescence line narrowing techniques in order to explore the local field dependent fluorescence properties of the lanthanide ions in this host. From the Raman and the vibronic spectra, various structural phosphate groups coupled to the Eu3+ ions have been identified. Local field dependent 5D0 → 7FJ (J = 0–6) emission spectra and the lifetimes of the 5D0 level have been measured under resonant excitation of the Eu3+ ions at different wavelengths within the 7F0 → 5D0 band at 16 K. From these data and using the Stark level positions of the 7F1 and 7F2 multiplets, a crystal-field analysis has been carried out assuming a C2v orthorhombic local symmetry. The radiative Judd–Ofelt parameters have been calculated for the different local fields found in the glass and their relative variation has been discussed. The results obtained suggest the existence of a relatively narrow distribution of local fields generated by successive distortions of a unique kind of site for all the Eu3+ ions in this fluorometaphosphate glass.

Research Highlights
► Fluorine ions participate in the immediate environment of the Eu3+ ions.
► Fluorometaphosphate glass has intermediate behavior for local structure of Eu3+.
► Migration of energy exists from Eu3+ ions in medium to weaker CF environments.
► Around 75% of Eu3+ ions occupy weak CF and 25% lie in medium CF environments.
► There exists a unique kind of site for all the local fields of the Eu3+ ions.