EXCITED-STATE ABSORPTION AND 3RD-ORDER OPTICAL NONLINEARITIES IN SYMMETRICAL PI-ELECTRON ORGANIC-MOLECULES

Excited-State Absorption (ESA), Two-Photon Absorption (TPA) and the th ird-order polarizability gamma(omega; omega, omega, - omega) have been investigated for a model dichloride derivative of a symmetrically sub stituted benzylidene analine (SBAC), using a multielectron configurati on-interaction procedure. The calculations indicate that SBAC exhibits ESA across the visible region of the spectrum, but that it is not as extensive as for molecules such as the phthalocyanines. The magnitude of the third-order polarizability is dominated by resonance enhancemen t from a very strong A(g) --> B-u one-photon absorption. The calculate d off-resonance value for gamma(omega; omega, omega, - omega) suggests that SBAC is a potential candidate for ultrafast switching applicatio ns.