Ultrafast optical nonlinearities in CdS nanocrystalline thin films prepared by chemical bath deposition

The dynamics of absorption bleaching in CdS nanocrystalline thin films were studied in the temperature interval 10-300 It and three distinct decay tim e constants (sub-ps, ps, and ns) were identified. We interpreted the dynami cs in terms of three groups of nanocrystals with specific defects and showe d that two of them are related. A close link between the temperature behavi our of the photoluminescence efficiency and that of the relative amplitude of the nanosecond component was observed and an explanation based on a micr oscopical model was proposed. The optical nonlinearities were studied by se lf-diffraction technique. A dephasing time constant shorter than 80 fs and a value of /chi (3)/ approximate to 6 x 10(-16) m(2) V-2 were obtained.