Mega three-photon absorption cross-section enhancement in pseudoisocyanine J-aggregates

Herein we report an extraordinary three-photon absorption cross-section (sigma(')(3)) enhancement in J-aggregates supramolecular systems. The much higher value of sigma(')(3) in PIC J-aggregate (2.5x10(-71) cm(6) s(2) ph(-2)) compared to typical values obtained in organic molecules (10(-80) cm(6) s(2) ph(-2)) is attributed to the strong molecular transition dipole moment coupling in the supramolecular assembly. Three-photon absorption of PIC J-aggregates and monomer aqueous solutions were measured using the well known open aperture Z-scan technique pumping with a 25 ps pulse laser-OPG system at 1720 nm. This novel result opens new expectations for applications of supramolecular systems in bioimaging and medicine. (c) 2005 American Institute of Physics.