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)-ethylidene]-4-isopropylidene-dihydrofuran-2,5-dione ( 1 ), a photochromic compound with λ max = 385 nm, using 775-nm femtosecond pulsed laser irradiation. The resulting photoisomer had λ 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 σ2 = 10.3 × 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.