title: Beam quality of a nonideal atom laser.
abstract: We study the propagation of a noninteracting atom laser distorted by the strong lensing effect of the Bose-Einstein condensate (BEC) from which it is outcoupled. We observe a transverse structure containing caustics that vary with the density within the residing BEC. Using the WKB approximation, Fresnel-Kirchhoff integral formalism, and ABCD matrices, we are able to describe analytically the atom-laser propagation. This allows us to characterize the quality of the nonideal atom-laser beam by a generalized M2 factor defined in analogy to photon lasers. Finally we measure this quality factor for different lensing effects.
authors.affiliation: Laboratoire Charles Fabry de l'Institut d'Optique, Centre National de la Recherche Scientifique et Université Paris Sud 11, Bât. 503, Campus Universitaire d'Orsay, 91403 Orsay Cedex, France. Jean-Felix.Riou@iota.u-psud.fr
authors.forename: J-F
authors.initials: JF
authors.lastname: Riou
authors.forename: W
authors.initials: W
authors.lastname: Guerin
authors.forename: Y
authors.initials: Y
authors.lastname: Le Coq
authors.forename: M
authors.initials: M
authors.lastname: Fauquembergue
authors.forename: V
authors.initials: V
authors.lastname: Josse
authors.forename: P
authors.initials: P
authors.lastname: Bouyer
authors.forename: A
authors.initials: A
authors.lastname: Aspect