Correlation between the temperature of molten state and the SH intensity of 30BaO-15TiO₂-55GeO₂ crystallized glass

We have examined the dependence of the optical nonlinearity of the 30BaO.15TiO₂.55GeO₂ (BTG55) crystallized glass on the temperature at which the BTG55 glass melts are held in a molten state (called the "melt temperature" in the present paper). The absorption coefficient and the refractive index of the BTG55 precursor glass, and the second harmonic efficiency of its crystallized glass increased with increasing melt temperature of the precursor glass. We have defined the local structure similar to that of a crystal, "embryos of crystallites", and the embryos are envisioned as the origin of precipitated Ba₂TiGe ₂O₈ crystallites. The second harmonic generation efficiency of the BTG55 crystallized glass increased with increasing melt temperature. This is explained as due to an increase of the number of embryos of Ba₂TiGe₂O₈ crystallites with increasing melt temperature.