INFLUENCE OF MOLECULAR ARCHITECTURE AND CHAIN-LENGTH ON THE NONLINEAR-OPTICAL RESPONSE OF CONJUGATED OLIGOMERS AND POLYMERS

Information technology is increasingly driving towards photonics, i.e. , exploiting light signals on the basis of nonlinear optical effects [ 1-3]. Progress in photonic devices requires the development of novel m aterials exhibiting strong optical nonlinearities, especially organic conjugated compounds. These are of interest, not only because of their large hyperpolarizabilities and very fast responses (that are electro nic in character), but also because of the possibilities of. tailored syntheses (adapting the molecular architecture at best for a given non linear optical process), multiple processing ways (namely in thin film s), high damage thresholds, and appearance of novel mechanisms for opt ical nonlinearities. Here, we present a review of some of our recent w ork on the nonlinear optical (NLO) response of conjugated oligomers an d polymers. We first briefly present the nature and merits of the comp utational techniques we have been using. We then discuss a novel type of second-order materials which by symmetry possess no dipole moment. We finally focus on third-order materials and examine the influence of molecular architecture and chain length on the nonlinear optical resp onse.