Achieving Peak Brightness in an Atom Laser

In this Letter we present experimental results and a simple analytic theory on the first continuous (long pulse) Raman atom laser. We analyze the flux and brightness of a generic two state atom laser with an analytic model that shows excellent agreement with our experiments. We show that, for the same source size, the brightness achievable with a Raman atom laser is at least 3 orders of magnitude greater than achievable in any other demonstrated continuously outcoupled atom laser.

Figure 1

A continuous Raman output coupler. (a) Transitions from the $5{}^{2}S_{1/2}F=2,m_F=0$ state to the $F=2,m_F=0$ state via the $5{}^{2}P_{3/2}$ transition of ${}^{87}\mathrm{Rb}$. (b) Absorption image ($0.7\mathrm{mm}\times 1.3\mathrm{mm}$) of an 8.5 ms continuous Raman atom laser produced with $60\mu \mathrm{W}$ per 1 mm beam. Inset shows a $200\mu \mathrm{m}$ slice through the transverse beam profile (longitudinal integration $200\mu \mathrm{m}$).

Figure 2

A comparison of the transit time of atoms through the output-coupling resonance $\Delta x$ for the rf and Raman output couplers. The inset shows a simple schematic of our model of continuous output coupling.

Figure 3

A comparison of experiment and theory for the output flux of an rf atom laser. Plotted is the number of atoms remaining trapped after 100 ms of continuous output coupling as a function of Rabi frequency.

Figure 4

Velocity distribution of the output coupled atoms after traversing the tightly confining longitudinal and transverse axes of the condensate, from an initial condition corresponding to a planar slice through the center of the condensate. The velocity due to gravity and/or the kick has been subtracted to show only the velocity contribution from the condensate mean field. (a) shows the transverse velocity distribution of the rf (solid) and Raman (dashed) atom laser, (b) the longitudinal distribution. The Raman atom laser is operated with the maximum $4\hslash k$ kick in the direction of gravity. Similar gains occur along the weakly confined transverse direction of the condensate.