How to mode-lock an atom laser

Summary form only given. In order to manufacture a modelocked, pulsed atom laser, we suggest the idea of making use of the atom-atom repulsion in a BEC to form a toroidal soliton which can then form a reproducible, coherent waveform. The relevant solitons have the form of a kink, or phase-singularity in the nonlinear Schrodinger equation. We suppose that the atoms are all trapped in a deep, toroidal magnetic trap with the central repulsive core potential induced by a blue-detuned laser. We investigate the case of an atom laser environment with a uniform gain provided by the super-saturation technique. We also assume that there is a periodic loss, provided by a synchronized Raman output coupling laser, and show that this combination of gain and periodic loss leads to stable circulating dark solitons.