Nonlinear Optical Properties of Some New Conjugated Copolymers

The ground- and the excited-state nonlinearities of two new copolymers are investigated in nanosecond scale at 1064 nm. It is found that the excited-state susceptibility is dramatically larger than the corresponding ground-state susceptibility for each sample. The experimental results also give evidence that superlattice structure of the copolymers can enhance, especially for the excited state, the molecular hyperpolarizabilities significantly. This enhancement may be attributed to the confinement effect of the pump-induced carriers.