title: Intensity-dependent reversal of nonlinearity sign in a gold nanoparticle array.
abstract: The optical nonlinearities of a Au nanoparticle array were determined by performing Z-scan measurements with a femtosecond laser (800 nm, 50 fs). As the exciting energy increased, the nonlinear absorption of the Au nanoparticle array changed from reverse-saturable absorption to saturable absorption, while the nonlinear refraction changed from self-defocusing to self-focusing, which implies competition between ground-state bleaching and two-photon absorption. One- and two-photon figures of merit of W=5.1 and T=0.11, respectively, were obtained that satisfy the demand, W>1 and T<1, for all-optical switching.
authors.affiliation: Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Wang
authors.forename: Hua
authors.initials: H
authors.lastname: Long
authors.forename: Ming
authors.initials: M
authors.lastname: Fu
authors.forename: Guang
authors.initials: G
authors.lastname: Yang
authors.forename: Peixiang
authors.initials: P
authors.lastname: Lu