Nonlinear optical properties of lead sulfide nanocrystals in polymeric coatings

Lead sulfide (PbS) nanocrystals with a particle size of 3.3 ± 0.7 nm have been synthesized in a poly vinyl alcohol (PVA) coating on fused silica glass substrates. The coating was dip-coated from a PVA aqueous solution, in which PbS nanocrystals were precipitated and stabilized in the polymer matrix. Third-order nonlinear optical susceptibility of PbS nanocrystals is dependent on the wavelength with its maximum located near the first excitonic absorption peak resulting from the quantum confinement effect, according to the results of degenerate four wave-mixing. This suggests an enhancement of the nonlinear optical property by excitonic resonance. The maximum figure of merit, χ⁽³⁾ /α, is as high as 2.91 × 10⁻¹² esu m as measured at 595 nm.