title: Hyperpolarizability effects in a Sr optical lattice clock.
abstract: We report the observation of a higher-order frequency shift due to the trapping field in a (87)Sr optical lattice clock. We show that, at the magic wavelength of the lattice, where the first-order term cancels, the higher-order shift will not constitute a limitation to the fractional accuracy of the clock at a level of 10(-18). This result is achieved by operating the clock at very high trapping intensity up to 400 kW/cm(2) and by a specific study of the effect of the two two-photon transitions near the magic wavelength.
authors.affiliation: LNE-SYRTE, Observatoire de Paris, 61, Avenue de l'Observatoire, 75014 Paris, France.
authors.forename: Anders
authors.initials: A
authors.lastname: Brusch
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Le Targat
authors.forename: Xavier
authors.initials: X
authors.lastname: Baillard
authors.forename: Mathilde
authors.initials: M
authors.lastname: Fouché
authors.forename: Pierre
authors.initials: P
authors.lastname: Lemonde