Experimental study of coupling Bose-Einstein condensates into weakly non-trapping and trapping states

We study the production of an atom laser from a Bose-Einstein condensate us ing radiofrequency out-coupling. Single frequency coupling from the Bose-Ei nstein condensate leads to unstable production of an atom laser due to the extreme sensitivity of this process to magnetic field fluctuations. The ext ent of this experimental instability is quantified. Stable, repeatable prod uction of an atom laser is achieved by the frequency modulation of the coup ling, which forms a frequency comb across the condensate. Different regimes of modulated coupling are discussed. In addition the coupling of atoms int o a weakly trapping state is studied. The oscillation frequency of this sta te in the vertical direction is measured. Preliminary results indicating qu alitative difference between condensate and thermal cloud coupling are pres ented. (C) 2001 Academie des sciences/Editions scientifiques et medicales E lsevier SAS.