Abstract

Organic materials are important to photonic applications due to their fast response times and the possibility of optimizing molecular structures to maximize nonlinear responses as well as other device required properties.^1,2 In organic molecules the easy electronic delocalization due to π electrons may result in high (microscopic) hyperpolarizabilities that manifest themselves, macroscopically, as nonlinear susceptibilities. Consequently, the first stage in a search for a promising material is to look for a lead molecule with large hyperpolarizabilities. This is usually done by using a polyene bridging two substituent groups: one, electron-donor, and the other, electron-acceptor. In a recent theoretical study, first-order hyperpolarizabilities of organic compounds with nolvene bridees were comnared to mesoionic ones³ indicating larger values to the later. Mesoionic rings are cyclic dipolar structures in which the positive and negative charges are both separated and delocalized within the tr electron system. By choosing adequate donor and acceptor substituents, one can obtain high hyperpolarizabilities and, hence, high χ⁽²⁾ and χ⁽³⁾ values.

© 1998 Optical Society of America