Spectroscopic Properties of $Yb^{3+}//Tb^{3+}$ Doped Germanate Glasses

In the article the cooperative energy transfer in GeO₂-GaO-BaO glass system doped with $Yb^{3+}//Tb^{3+}$ under 980 nm laser diode excitation was investigated. The influence of $Tb^{3+}$ concentration on the luminescent properties was determined. Measured strong luminescence at 489, 543, 586, 621 corresponds to $\text{}5D_4 \rightarrow \text{}^7 F_{J} $ (J = 6, 4, 3) transitions and luminescence at 381, 415, 435 nm results from $\text{}5 D_3, \text{}^5 G_6 \rightarrow \text{}^7 F_{J}$ (J = 6, 5, 4) transitions. Mechanism and energy diagram involved in observed emission were discussed. The highest upconversion emission intensity was obtained in the germanate glass doped with 0.7Yb₂O₃/0.7Tb₂O₃.