Optical properties of new low-phonon SnF2–PbF2–ZnF2 glasses

New fluoride glasses were developed in the SnF2–PbF2–ZnF2 system. Additions of 5 mol% of CsCl or 6–15 mol% of AlF3 were found to stabilize the glass formation. The IR absorption of the glasses and the optical properties of the europium ions doped in the glasses were compared with those of a fluorozirconate glass as a representative fluoride glass. The IR spectra showed that the new glasses have the peak of the phonon energy at 400 cm−1, which is about 100 cm−1 lower than that of the fluorozirconate glass. The results of the fluorescence measurement of the europium ions revealed that the multi-phonon relaxation rate in these glasses is smaller than that in the fluorozirconate glass.