PbS-polymer nanocomposite with third-order nonlinear optical response in femtosecond regime

A new method is developed using polymerized bicontinuous rnicroemulsions to synthesize PbS-polymer nanocomposite having large nonlinear optical response. Besides a polymeric nonionic surfactant, omega -methoxy poly(ethylene oxide)(40) undecyl-alpha -methacrylate (C-1-PEO-C-11-MA-40), a system consisting of methyl methacrylate (MMA), acronitrile (AN), ethylene glycol dimethacrylate (EGDMA), aqueous solutions of Pb(NO3)(2)/thioacetamide (TAA) was selected. High-resolution transmission electron microscopy (HRTEM) results indicated PbS nanocrystals with a width of 5 nm and a cubic structure is formed in water domains. A single-beam Z-scan measurement showed that the nanocomposite polymer has a nonresonant and negative nonlinear refractive index (gamma) of 6.8 x 10(-12) cm(2)/W at 780 nm. The origin of the large nonlinear optical response based on the contribution of surface recombination owing to high surface-to-volume ratios of PbS nanoparticles to the optical nonlinearity is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.