Mid-infrared luminescence properties of erbium and dysprosium doped lanthanum titanate glasses

Glasses of composition xRE₂O₃-(17−x) La₂O₃-83 TiO₂ were prepared by levitation melting from x = 0.1 to 9 for RE=Er and at x =0.1 and 1 for RE=Dy. The glasses have high transition temperature, exhibit low OH, and 1 mm thick discs are transparent out to 6 µm. Mid-infrared emission lineshapes and lifetimes are comparable to what is seen in tellurite glasses containing Er³⁺ and Dy³⁺. For x fixed at 1, the Er³⁺:⁴I₁₁/₂ → ⁴I₁₃/₂ transition at 2716 nm has a fluorescence lifetime of 254 µs and the Dy³⁺:⁶H₁₃/₂ → ⁶H₁₅/₂ transition at 2957 nm has a fluorescence lifetime of 9.09 µs. The results indicate that doped lanthanum titanate glasses offer the thermal stability of a’hard’ glass with the host properties typically associated with’soft’ glasses. Problems with the measurement of spectral features in the mid-infrared that could erroneously be assigned as resulting from rare-earth ion emissions are presented and discussed.