Nature of photoluminescence involving transitions from the ground to 4 _f^n-1 5d¹ states in rare-earth-doped glasses

Photoluminescence from Er³⁺ or Pr³⁺ ion-doped silica or ZBLAN (ZrF₄-BaF₂-LaF₃-AlF₃-NaF) glass, excited by high-energy photos such as excimer laser photons, was investigated mainly through the temperature dependence. When there are two emission states whose energy difference is small, as in the case of ²H_11/2 and ⁴S_3/2 in Er³⁺ or the ¹I₆/³P₁ mixing state and ³P₀ in Pr³⁺, the luminescence from the upper state and that from the lower state are found to depend inversely on temperature. This indicates that the thermalization or thermal equilibrium of electrons between the two emission states occurs.