Theoretical studies on several TPA materials with three different pi electron centers

Using density functional theory and ZINDO method, the two-photon absorption (TPA) cross-section (delta) and nonlinear third-order optical hyperpolarizabilities (gamma) of several TPA materials with three different pi electron centers (diphenylacetylene, stilbene and azobenzene) were theoretically investigated. On the basis of correct geometry and UV-Vis spectrum, the position and strength of the one-photon absoorption (OPA) and two-photon (TPA) were studied and compared systematically.