Structure and nonlinear optical properties of BaO-TiO2-B2O3 glasses

The third order nonlinear optical susceptibilities chi((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 1-coordinated. It was found that the addition of TiO2 to BaO-B2O3 glass increases the chi((3)) as well as the refractive index, The positive effect of the TiO2 on the chi((3)) was interpreted in terms of the empty d-orbital contribution. The largest chi((3)) obtained is 3.0 x 10(-13) esu for 35BaO . 55TiO(2) . 10B(2)O(3) glass, which is, however, only 10 times larger than that for SiO2 glass. Such a small enhancement in chi((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 chi((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 chi((3)) and (n(omega)(2)+2)(3) .(n(omega)(2)-1). E-d/E-0(2) is adopted for this system.