title: Ultrafast and large third-order nonlinear optical properties of CdS nanocrystals in polymeric film.
abstract: We report the ultrafast and large third-order nonlinear optical properties of CdS nanocrystals (NCs) embedded in a polymeric film. The CdS NCs of 2 nm radius are synthesized by an ion-exchange method and highly concentrated in the two layers near the surfaces of the polymeric film. The two-photon absorption coefficient and the optical Kerr coefficient are measured with laser pulses of 250 fs duration at 800 nm wavelength. The one-photon and two-photon figures of merit are determined to be 3.1 and 1.3, respectively, at irradiance of 2 GW/cm(2). The observed nonlinearities have a recovery time of approximately 1 ps. The two-photon-generated free carrier effects have also been observed and discussed. These results demonstrate that CdS NCs embedded in polymeric film are a promising candidate for optical switching applications.
authors.affiliation: Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Republic of Singapore.
authors.forename: J
authors.initials: J
authors.lastname: He
authors.forename: W
authors.initials: W
authors.lastname: Ji
authors.forename: G H
authors.initials: GH
authors.lastname: Ma
authors.forename: S H
authors.initials: SH
authors.lastname: Tang
authors.forename: E S W
authors.initials: ES
authors.lastname: Kong
authors.forename: S Y
authors.initials: SY
authors.lastname: Chow
authors.forename: X H
authors.initials: XH
authors.lastname: Zhang
authors.forename: Z L
authors.initials: ZL
authors.lastname: Hua
authors.forename: J L
authors.initials: JL
authors.lastname: Shi