Nonlinear Opt ical Propert ies of Conjugated Molecules

Due to their intrinsic orientational anisotropy and elevated polarizability n-conjugated polymers are widely perceived as promising materials for use in nonlinear optical devices. Advances in the development of practical systems have been impeded, however, by the difficulties in developing a realistic theoretical description of the experimental situation. In this paper we present several examples of theoretical progress towards this goal and discuss how the different effects contributing to the polarization response in the systems can be quanti fied