A quasi-monomode guided atom laser from an all-optical Bose-Einstein condensate

We report the achievement of an optically guided and quasi-monomode atom laser, in all spin projection states (mF=-1, 0 and +1) of F=1 in rubidium 87. The atom laser source is a Bose-Einstein condensate (BEC) in a crossed dipole trap, purified to any one spin projection state by a spin-distillation process applied during the evaporation to BEC. The atom laser is outcoupled by an inhomogenous magnetic field, applied along the waveguide axis. The mean excitation number in the transverse modes is ⟨n⟩=0.65±0.05 for mF=0 and ⟨n⟩=0.8±0.3 for the low-field seeker mF=-1. Using a simple thermodynamical model, we infer from our data the population in each excited mode.