We have investigated the rf output coupling of a 87Rb condensate from a Ioffe-Pritchard magnetic trap. Multiple condensates in different Zeeman states are produced, their population being varied by playing with the duration and the amplitude of the rf pulse. Both pulsed and continuous outputs (atom laser) have been observed.
Summary form only given. We report results concerning both theoretical and experimental studies of collective excitations in connection with the atom laser operation. We use a radio-frequency field to out-couple a coherent matter-wave beam, either continuous or pulsed, from a /sup 87/Rb condensate. The latter scheme itself induces collective excitations in the atom laser. Starting from a condensate in the F=2, m/sub F/=2 state the radio-frequency field populates both trapped and untrapped Zeeman sublevels. A rich phenomenology arises including the production of multiple condensates exhibiting different dynamical behaviour, which make clear evidence of mutual interactions. The use of a static very elongated Ioffe trap allows a precise experimental investigation which can be compared with the predictions based on the solution of the time-dependent Gross-Pitaevskii equation. In the pulsed regime, the sudden change of the internal energy produces collective oscillations in the shape both for the m/sub F/=2 and the m/sub F/=1 trapped condensate. Preliminary results for the m/sub F/=2 atom laser show that the experimental behaviour is likely to be reproduced by the simulations only if mutual interactions are taken into account.
We present a theory to derive the output rate of an atom laser consisting of an interacting Bose-Einstein condensate in a magnetic trap and two additional rf fields transferring trapped atoms to a repelled Zeeman sublevel via an intermediate untrapped Zeeman sublevel. We explicitly obtain the dependence of the output rate ${\ensuremath{\Gamma}}_{\mathrm{out}}$ on various characteristic parameters such as a coupling parameter (the Rabi frequency), the atom number density in the center of the condensate, and the strength of the atom-atom interaction.
This thesis describes the development and construction of a machine for producinghigh atom-number Bose-Einstein Condensates (BECs). Emphasis is given to thenovel Ioe-Pritchard magnetic trap used, that consists exclusively of circular coils.This allowed us to achieve higher gradients and thus tighter connements [1].This thesis also describes a novel atom-laser output-coupler based on time dependentadiabatic potentials (TDAP) [2]. In this method strong rf elds are usedto deform the trapping potential. Contrary to the traditional weak rf methods thatextracts the atoms from the center of the BEC, the TDAP atom lasers emerge fromthe edge of the condensate. This provides the atom lasers with low divergence.Furthermore, the atoms are outcoupled from the BEC at an arbitrarily large rateleading to uxes per trapped atom sixteen times higher compared to the brightestquasi-continuous atom laser.Finally, presented is the coldest thermal atom beam to date. Using the TDAPoutcoupling, we produced thermal atom beams with temperatures as low as 200 nK,which makes it, by two orders of magnitude, the coldest thermal beam ever observed.Something like that would be very useful for high-resolution spectroscopy of ultracoldcollisions.