NON-RESONANT-TYPE-3RD-ORDER OPTICAL NONLINEARITY OF ALKALI SILICATE AND ALKALI ALUMINOSILICATE GLASSES - CONTRIBUTION OF INDIVIDUAL CHEMICAL-SPECIES IN THE GLASSES TO CHI((3))

The dependence of the non-linearity on the composition of alkali silicate and alkali aluminosilicate glasses was explored to investigate the contribution of bridging, non-bridging oxygens and alkali ions to third-order optical non-linearity. The glasses were prepared by the conventional melting and quenching technique, and composition ranges were x = 15-33 mol% for xR(2)O .(100 - x)SiO2 glasses (R: Na, K and Rb) and y = 10-30 mol% for 30R(2)O . yAlO(0.5).(70 - y)SiO2 glasses. From the hyperpolarizability, alpha((3)), calculated from third-order optical non-linear susceptibility, X((3)), the larger contribution of non-bridging oxygens (0.60 X 10(-35) esu cm(3)/ion) compared with bridging ones (0.43 X 10(-35) esu cm(3)/ion) was revealed. The influence of large polarizable alkali ions is 1-3.7 times larger than that of the non-bridging oxygens.