Optical nonlinearity of monodispersed, capped ZnS quantum particles

Abstract

ZnS quantum dots are synthesized by a high-temperature chemical route with narrow size distribution at diameters of 1.4 and 1.8 nm. Significantly small size dispersion of 1.4-nm-sized ZnS quantum dots is vivid from the transmission electron microscopic measurements. The nonlinear absorption is measured at wavelengths 532 and 520 nm using a picosecond laser in an open aperture z -scan setup. The measured two-photon absorption coefficients are 0.08 and 0.2 cm/GW for smaller and larger nanoparticles. Two photon absorption cross sections for nanoparticles are about six orders of magnitude larger than bulk ZnS.