PbSe/polyvinyl alcohol composite film with third-order nonlinear optical property was prepared by wet-chemical method.The morphology of the PbSe nanocrystals was characterized by transmission electron microscope,and the surface morphology of the composite film was characterized by scanning electron microscope.The third-order optical nonlinearity of film was investigated by using the laser Zscan technique with 38ps pulses width at 532nm.The experimental results show that the diameter of PbSe nanocrystals is ...