Two-photon photochromism of an organic material for holographic recording

We report the two-photon-induced photoisomerization of 3-[1-(1,2-dimethyl-1H-indol-3-yl)-etliylidene]-4-isopropylidene-dihydrofuran-2,5-dione (1), a photochromic compound with lambda(max) = 385 nm, using 775-nm femtosecond pulsed laser irradiation. The resulting photoisomer had lambda(max), = 582 nm. The kinetic rate constant for the two-photon-induced electrocyclic isomerization reaction was measured at two different intensities (two different powers), showing a quadratic dependence with respect to the pump intensity. Results of pump-probe solution phase experiments and guest/host polymer thin film interferometric imaging studies are reported. A two-photon absorption molecular cross section sigma2 = 10.3 x 10(-48) cm(4) (.)s/photon was measured using Z-scan, further supporting a two-photon-induced isomerization process. Two-photon-induced interferometric recording in a fulgide-containing polymer film was demonstrated.