PREPARATION OF ORGANIC DYE-DOPED SIO2 GELS BY THE SOL-GEL PROCESS AND EVALUATION OF THEIR OPTICAL NONLINEARITY

An organic dye, 4'-dimethylamino-N-methyl-4-stilbazolium iodide [DMSI], which has high third order optical non-linearity, was incorporated into SiO2 gel by the sol-gel method. The structure of DMSI in gel was studied on the basis of absorption spectrum. It was found that DMSI has preferentially cis form in the gel, and the trans-cis equilibrium could be controlled by selection of solvent. Third order non-linear susceptibility, chi(3), values of dye-doped gels were 4-5 x 10-(14) esu, which were twice as large as SiO2 glass. The chi(3) value of gel doped with the trans-form was clearly larger than that of the cis-form.