title: Bound electronic and free carrier nonlinearities in Silicon nanocrystals at 1550nm.
abstract: We present a detailed investigation of the different processes responsible for the optical nonlinearities of silicon nanocrystals at 1550 nm. Through z-scan measurements, the bound-electronic and excited carrier contributions to the nonlinear refraction were measured in presence of two-photon absorption. A study of the nonlinear response at different excitation powers has permitted to determine the change in the refractive index per unit of photo-excited carrier density sigma(r) and the value of the real bound-electronic nonlinear refraction n(2be) as a function of the nanocrystals size. Moreover at high excitation power, a saturation of the nonlinear absorption was observed due to band-filling effects.
authors.affiliation: Nanoscience Laboratory, Dipartimento di Fisica, Università di Trento, Via Sommarive 14, I-38050 Povo-Trento,Italy. spano@science.unitn.it
authors.forename: R
authors.initials: R
authors.lastname: Spano
authors.forename: N
authors.initials: N
authors.lastname: Daldosso
authors.forename: M
authors.initials: M
authors.lastname: Cazzanelli
authors.forename: L
authors.initials: L
authors.lastname: Ferraioli
authors.forename: L
authors.initials: L
authors.lastname: Tartara
authors.forename: J
authors.initials: J
authors.lastname: Yu
authors.forename: V
authors.initials: V
authors.lastname: Degiorgio
authors.forename: E
authors.initials: E
authors.lastname: Giordana
authors.forename: J M
authors.initials: JM
authors.lastname: Fedeli
authors.forename: L
authors.initials: L
authors.lastname: Pavesi