Nonlinear optical transmission of polyquinoline thin film at 532 nm

Optical nonlinearities of polyquinoline thin film were studied by measuring fluence-dependent transmission with nanosecond pulses from the second harmonic of an Nd: YAG laser. It is found that the origin of nonlinearity is due to the excited-state absorption in the nanosecond domain. To our knowledge, we report the first simultaneous determination of the decay time for the excited-state and the excited-state absorption cross-section of polyquinoline by analysing the linear slopes of the transmission versus fluence plot, which are dependent on pulsewidth.