QUADRATIC ELECTROOPTIC EFFECT IN MOLECULES WITH LARGE OPTICAL HYPERPOLARIZABILITIES

We report quadratic electrooptic derived third-order optical polarizabilities, gamma, on two thiazole azo dyes that we have previously demonstrated to possess large optical hyperpolarizabilities, beta. We demonstrate that the data are consistent with our previously introduced restricted three-level model for gamma. Specifically we show that the susceptibility can be accounted for by two perturbative terms and that we are also possibly observing the predicted enhancement in gamma for molecules with large beta when the peak narrows. We also suggest that this mechanism offers an approach to systematic improvements for the ratio Re[gamma]/Im[alpha].