PICOSECOND-INDUCED NONLINEAR ABSORPTION IN LIQUID-CRYSTAL MEDIA

The contributions to the nonlinear absorption of liquid crystal media in their isotropic phase are measured using a picosecond pump/probe technique at 587 nm. Good agreement between the experimental data and theory is obtained by assuming that two-photon absorption and excited state absorption dominate the nonlinear optical response. The important parameters are extracted from the experimental data and it is shown that the nonlinear absorption depends strongly on the molecular structure. The lifetime of the excited state is measured and found to compare well with the fluorescence lifetime.