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 materials 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 electronic in character), but also because of the possibilities of: tailored syntheses (adapting the molecular architecture at best a given nonlinear optical process), multiple processing ways (namely in thin films), high damage thresholds, and appearance of novel mechanisms for optical nonlinearities. Here, we present a review of some of our recent work on the nonlinear optical (NLO) response of conjugated oligomers and polymers. We first briefly present the nature and merits of the computational techniques we have been using. We then discuss a novel type of second-order materials which by symmetry process no dipole moment. We finally focus on third-order materials and examine the influence of molecular architecture and chain length on the nonlinear optical response.