PHASE DIFFUSION AND THE OUTPUT PROPERTIES OF A CW ATOM-LASER

We study an output coupler for matter waves that could be used to deve lop a cw atom-laser, based on current Bose-Einstein-condensation exper iments with alkali-metal atoms. Assuming a cw pump mechanism for the c ondensate and taking into account losses due to outgoing atoms allows a description of the output by a coherently driven and damped Schrodin ger equation. By contrast to a pulsed atom-laser output the stationary outgoing matter wave is extremely monoenergetic. Phase fluctuations o f the condensate and technical noise limit the coherence length of the output beam. Using a Monte Carlo simulation we obtain the spatial cor relation function of the output wave function, also including the infl uence of gravity.