Third-order nonlinear optical response in PbS-coated CdS nanocomposites

PbS-coated CdS nanocomposite particles were synthesized by an ion displacem ent method in an inverse microemulsion, Their growth kinetics were studied with UV-vis spectroscopy. Transmission electron microscopic characterizatio n shows that PbS-coated CdS particles are uniform in size with a mean diame ter of 6 nm, The electron diffraction patterns demonstrate their crystallin e nature, Third-order nonlinear optical properties in the samples were inve stigated using the Z-scan technique with femtosecond laser pulses at 780-nm wavelength, The nonlinear refractive index of PbS-coated CdS nanocomposite particles in microemulsion varied with the molar ratio of Cd/Pb ions and r eached a maximum of 5.3 x 10(-12) cm(2)/GW for the sample with a Cd/Pb ion ratio of 1 to 2. The observed large refractive nonlinearity in these nanoco mposite particles may be attributed to the optical Stark effect and strong interfacial and inter-nanoparticle interactions.