The three-photon absorption and multiphoton upconversion fluorescence spectra of star-shaped stilbene derivatives 2,5-bis{4-{2-N,N-bis[4-(2-N,N-diphenyl-amino-phenyl-vinyl)phenyl]aminostyryl} phenyl}-1,3,4-oxadiazole (DPASPO) and 1,2,4,5-tetra(4-N,N-diphenylaminostyryl)benzene (PASB) were measured using a femtosecond Ti:sapphire laser. The absorption, one-photon fluorescence and fluorescence lifetime have been investigated. When pumped with 800 nm femtosecond laser irradiation, chromophore DPASPO and PASB show strong two-photon excited yellow green fluorescence at 583 nm and 547 nm respectively. When pumped with 1260 nm femtosecond laser, DPASPO and PASB show strong three-photon excited fluorescence at 612 nm and 572 nm in the solution of dichloromethane, respectively. Three-photon absorption cross-sections determined by nonlinear transmission method are 16.69×10^－79 cm⁶•s² (1300 nm) for DPASPO and 6.81×10^－79 cm⁶•s² (1320 nm) for PASB, respectively. These stilbene derivatives show large 3PA cross-sections. In these star-shaped chromophores, the increasing the stilbene-branched moieties and an extended π-conjugation domain, and through-space delocalization results in a increase of three photon absorption.

Key words: star-shaped chromophores, three-photon absorption, two-photon excited fluorescence, three-photon excited fluorescence, three-photon absorption cross-sections, upconversion fluorescence