Pulsed pumping of a Bose-Einstein condensate

In this work, we examine a system for coherent transfer of atoms into a Bose-Einstein condensate. We utilize two spatially separate Bose-Einstein condensates in different hyperfine ground states held in the same dc magnetic trap. By means of a pulsed transfer of atoms, we are able to show a clear resonance in the timing of the transfer, both in temperature and in number, from which we draw conclusions about the underlying physical process. The results are discussed in the context of the recently demonstrated pumped atom laser.

Figure 1

(Color online) Sequential illustration of the experiment. (a) The setup includes a source and a lasing condensate trapped in the same quadrupole-Ioffe configuration trap. (b) A pulse of atoms is output coupled from the source cloud and is accelerated downward due to gravity. (c) As the atoms fall, a variable delay pulse of $\pi$-polarized light is applied. (e) The atoms in the transfer pulse continue to fall and are detected via absorption imaging.

Figure 2

(Color online) Remaining atom number in the transfer pulse as a function of the time delay of the pumping pulse. The absorption pictures show the remaining atoms in the transfer pulse after the pumping process. The inset depicts the efficiency of the pumping process as a function of the size of the lasing condensate.

Figure 3

(Color online) Width of the lasing condensate (normalized to the width with no pumping light applied) as a function of the time delay of the pumping pulse. The two insets show the integrated density profile of the (expanded) lasing condensate for two different time delays of the pumping pulse.

Figure 4

(Color online) Spectroscopic results for the source ($F=2$, red crosses) and the lasing ($F=1$, blue circles) condensates. The solid lines are Gaussian fits to the data. The operating region (shaded area) is clearly separated from the overlap region between the two condensates.

Figure 5

Theoretical results for the remaining atom number in the transfer pulse as a function of the time delay of the pumping pulse.