Giant Second Harmonic Generation from Metastable BaTi2O5

Giant second harmonic generation (SHG) was observed while metastable $\alpha$-BaTi 2 O 5 crystallized from BaTi 2 O 5 glass. The observed SHG confirmed that $\alpha$-BaTi 2 O 5 had a large polarization and a non-centrosymmetric structure. The optical anomaly suggested that the alignment of polar nanocrystals of $\alpha$-BaTi 2 O 5 was the cause of the observed giant dielectric response. Furthermore, the giant SH intensity of $\alpha$-BaTi 2 O 5 could be obtained at room temperature by quenching the crystallized $\alpha$-BaTi 2 O 5 . The thermal stability of $\alpha$-BaTi 2 O 5 was evaluated by in situ monitoring of the SH intensity above the crystallization temperature. These results demonstrate that $\alpha$-BaTi 2 O 5 is a promising material for electro-optical applications, even at high temperatures.