title: Optical nonlinear absorption and refraction of CdS and CdS-Ag core-shell quantum dots.
abstract: The CdS and CdS-Ag core-shell quantum dots (QDs) have been prepared. The nanostructures of the QDs were revealed by transmisson electron microscopy and absorption spectra, respectively. The third-order nonlinear optical properties of the core-shell QDs have been studied by using Z-scan technique with femtosecond pulses at the wavelength of 790 nm. The value of the effective nonlinear absorption coefficient beta(eff) of CdS-Ag QDs is measured to be about 16.8 cm/GW, which is about 400 times larger than that of bare CdS QDs of 3.9 x 10(-2) cm/GW. The nonlinear refraction index gamma of CdS-Ag QDs is about -2.3 x 10(-4) cm(2)GW, which is about 200 times larger than that of bare CdS QDs of 1.0 x 10(-6) cm(2)GW.
authors.affiliation: Department of Physics, Wuhan University, Wuhan 430072, China.
authors.forename: Hong-Mei
authors.initials: HM
authors.lastname: Gong
authors.forename: Xiao-Hui
authors.initials: XH
authors.lastname: Wang
authors.forename: Yu-Min
authors.initials: YM
authors.lastname: Du
authors.forename: Qu-Quan
authors.initials: QQ
authors.lastname: Wang