Output coupling of Bose condensates from atomic tunnel arrays: a numerical study

We present an extensive numerical study of the transport properties of an interacting Bose-Einstein condensate subject to the forces induced by a periodic potential and by gravity. This system models a mode-locked, pulsed laser of matter waves, which was recently realized by Anderson and Kasevich [Science 781 (1998) 1686] with a condensate of Rb-87 atoms confined in an optical lattice. We solve the time-dependent Gross-Pitaevskii equation for this model by a novel fast algorithm and examine in detail the role of the atomic interactions in determining the existence, the shape, the period of formation and the size of the pulses. The transport behaviour of the system as a function of its governing parameters is summarized in a simple two-dimensional diagram, (C) 1999 Published by Elsevier Science B.V. All rights reserved.