Second-Harmonic Generation in Optically Poled WO₃-TeO₂ Glasses Doped with Vanadium and Rare-Earth Elements

抄録

Second-harmonic generation (SHG) has been observed in optically poled TeO₂-WO₃ glasses doped with vanadium. The second-harmonic (SH) intensity depends on the concentration of vanadium; the glass doped with 0.1 mol% of V₂O₅ manifests the maximum SH intensity. The SH intensity is larger and the second-order nonlinearity is more stabile for 20WO₃ · 80TeO₂ glasses than for 15Nb₂O₅ · 85TeO₂ glasses reported previously. Besides, enhancement of SH intensity is observed in glasses co-doped with rare-earth element such as Tb, Pr, and Ce in addition to vanadium. We speculate that Tb⁴⁺, Pr⁴⁺and Ce⁴⁺ play a role of trap centers for electrons; a positive hole trapped at V⁴⁺ as well as the electron trapped at the tetravalent rare-earth ion forms internal dc field, the spatial periodic variation of which gives rise to SHG.