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

A new method is developed using polymerized bicontinuous microemulsions to synthesize PbS–polymer nanocomposite having large nonlinear optical response. Besides a polymeric nonionic surfactant, ω-methoxy poly(ethylene oxide) 40 undecyl-α-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(NO 3) 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 ( γ) of 6.8×10 −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.