Fabrication and characterization of nanoscale, Er3+-doped, ultratransparent oxy-fluoride glass ceramics

We show that oxy-fluoride glass ceramics, with typical composition, 32(SiO2):9(AlO1.5):31.5(CdF2):18.5(PbF2):5.5(ZnF2): 3.5(ErF3) mol % have potential applications in telecommunications. Upon heat treatment, Er3+ nucleates the growth of the nanocrystalline beta-PbF2, which acts as its host. Heat treatment at 440 degreesC for 5 h and at 390 degreesC for 3 h gave rise to similar to12 and similar to2.5 nm diameter crystals, respectively. The emission band of Er3+ in the 1.54 mum telecommunications window (I-4(13/2)-->I-4(15/2) transition, at the half-height width) was 75 nm in the former and 90 nm in the latter case, while I-4(13/2)<---->I-4(15/2) absorption and emission bands became wavelength divergent in both cases. Also in the latter case, the spectrum was flat from 1.53 to 1.56 mum. The evolution of spectral behavior is explained by changes in average site geometry of the Er3+ dopant, related to the alpha-->beta phase transition of PbF2, which is stimulated by heat treatment.