A well-collimated quasi-continuous atom laser

Abstract

Extraction of sodium atoms from a trapped Bose-Einstein condensate (BEC) by a coherent, stimulated Raman process is demonstrated. Optical Raman pulses drive transitions between trapped and untrapped magnetic sublevels, giving the output-coupled BEC fraction a well-deÞned momentum. The pulsed output coupling can be run at such a rate that the extracted atomic wave packets strongly overlap, forming a highly directional, quasi-continuous matter wave. The occupation of a single quantum state by a large number of identical bosons (1–5) is a matter-wave analog to the storage of photons in a single mode of a laser cavity. Just as one extracts a coherent, directed beam of photons from a laser cavity by using a partially trans-mitting mirror as an output coupler, one can analogously extract directed matter waves from a condensate. Such a source of matte