BaO-TiO₂-B₂O₃ガラスの構造と非線形光学特性

抄録

The third order nonlinear optical susceptibilities χ⁽³⁾ of BaO-TiO₂-B₂O₃ glasses have been measured by the third harmonic generation (THG) method. Raman spectroscopic investigation revealed that Ti⁴⁺ ions mainly exist as 4-coordinated. It was found that the addition of TiO₂ to BaO-B₂O₃ glass increases the χ⁽³⁾ as well as the refractive index. The positive effect of the TiO₂ on the χ⁽³⁾ was interpreted in terms of the empty d-orbital contribution. The largest χ⁽³⁾ obtained is 3.0×10^-13 esu for 35BaO⋅55TiO₂⋅10B₂O₃ glass, which is, however, only 10 times larger than that for SiO₂ glass. Such a small enhancement in χ⁽³⁾ is ascribed to the large fraction of 4-coordinated Ti⁴⁺ ions in BaO-TiO₂-B₂O₃ glasses. It is concluded that, for TiO₂-containing glasses, the higher χ⁽³⁾ values are attained when the optical basicity is low and the amount of Ti⁴⁺ ion is large. It was found that the modified Lines' relationship between χ⁽³⁾ and (n_ω²+2)³⋅(n_ω²-1)⋅E_d/E₀² is adopted for this system.