Heterodyned Femtosecond Optical Kerr Effect of Substituted Conjugated Polymers

The femtosecond optical heterodyne detected optical Kerr effect is described. The real and the imaginary parts of complex third-order optical nonlinearity can be effectively separated and their values and signs can be determined. Using this method, we have thoroughly investigated the substitution effect by adding side-groups on the -(-C=N-)- conjugated system, a new class of nonlinear optical material, and find that the polybenzonitrile (γ_r = -1.59 x10^-31 esu, m = 6 ) is an order of magnitude superior to poly-amino-nitrile. But when we further add substituents on benzoid rings, the enhancement is limited. We can say that for the series of polybenzonitrile, the benzoid ring can improve the x⁽³⁾ value more effectively than other substitutions.