Mechanisms for enhancement of two-photon absorption in donor-acceptor conjugated chromophores

Two-photon absorption (TPA) is a nonlinear optical process that is gaining increasing attention since it can be exploited in a number of optical applications. Here, on the basis of correlated quantum-chemical calculations, we investigate the structure-TPA property relationships for donor-acceptor pi-conjugated compounds. These relationships provide strategies to design dyes with large TPA cross-sections for fundamental photon wavelengths in the desired 0.6-1.0 mu m range of wavelengths. (C) 1998 Elsevier Science B.V. All rights reserved.