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Optical absorption spectra of Nd 3+ -doped fluorophosphate glasses of the type 75NaPO 3 –24AF–1NdF 3 (A=Li, Na, K) and of the type 75NaPO 3 –24AF 2 –1NdF 3 (A=Ca, Sr, Ba, Zn, Cd) have been recorded. The dipole strengths are parameterised in terms of three phenomenological Judd–Ofelt intensity parameters Ω λ ( λ =2, 4 and 6). With the knowledge of these intensity parameters, the probability for spontaneous emission, the branching ratios and the radiative lifetime are calculated. The relation between the spectral intensities and the glass composition is discussed. The optical properties of the fluorophosphate glasses are compared with those of phosphate and fluoride glasses. It is shown that the choice of the cation only has a minor influence on the spectral intensities. The spectral behaviour of the fluorophosphate glasses is intermediate between the spectral behaviour of pure phosphate and fluoride glasses.

The magnetic circular dichroism (MCD) and optical absorption spectra are recorded for Ho3+ ions in fluorozirconate (ZBLAN) glass. The measurements cover the spectral region from 14 000 cm−1 to 40 000 cm−1. The dipole strengths of the optical transitions are given and compared with holmium ions in other matrices. The Faraday (or MCD) parameters are determined by the method of moment analysis. The most striking feature of the MCD spectrum is the dominance of the temperature-dependent C terms.

Fluoride glass optical fibres are characterized by a large optical window covering the range 0.4–5 μm which permits excitation and fluorescence spectroscopy in a much more extended domain than with silica-based fibres. The local ligand field acting on the rareearth ions affects the radiative lifetime, phonon relaxation, excited state absorption, and emission peak broadening. Finally, the fibre structure provides excellent optical confinement for observing laser emission in the visible and mid-IR regions at very low threshold power, permitting laser diode pumping. Multiphonon processes are also observed leading to the up-conversion of IR into the visible or UV and making possible the development of new laser sources for optical recording laser printing, optical amplification, medical and optical sensor applications.