Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, Vol.370, 155-159, 2001
Fluorene-based organic molecule with high two-photon absorption activities
High two-photon absorption (TPA) molecule having a fluorene pi -center (TP-Flu-TP) was prepared by the Heck reaction of 2,7-dibromo-9,9-diethylhexyl-9H-fluorene and 4-(diphenylamino)benzstyrene. The linear absorption maximum of the TP-Flu-TP was observed at 410 nm. The dispersion of the TPA intensity for the chromophore was measured by nonlinear transmission using 7 ns laser pulse. Since the maximum wavelength of this molecule occurred at 740 nm, we fixed the pumping wavelength at 740 mn for TP-Flu-TP and measured the transmitted pulse energy versus the input pulse energy. From this experiment we observed a distinct nonlinearity from TP-Flu-TP demonstrating that it is a potential material for optical limiting. The calculated two-photon absorption cross section (delta) by the Hartree-Fock Hamiltonian with single configuration interaction formalism was 1.37x10(-47) cm(4) sec/photon.