Simultaneous magneto-optical trapping of three atomic species

We report on the simultaneous trapping of two fermionic species, ${}^6\mathrm{Li}$ and ${}^{40}\mathrm{K}$, and a bosonic species, ${}^{87}\mathrm{Rb}$, demonstrating the first three-species magneto-optical trap (“triple MOT”). The apparatus including the atom sources and the three laser systems is described, and the single-species MOTs and the triple MOT are characterized. In triple MOT operation, typical atom numbers of $3.2\times {10}^7$ for ${}^6\mathrm{Li}$, $1.5\times {10}^7$ for ${}^{40}\mathrm{K}$, and $5.4\times {10}^9$ for ${}^{87}\mathrm{Rb}$ were achieved. Trap loss due to interspecies collisions was observed. We describe our way to optimize the triple MOT and turn it into a suitable source for the goal to achieve quantum degeneracy by evaporative and sympathetic cooling.

Figure 1

Atomic energy levels and transitions used to slow and trap lithium, potassium, and rubidium atoms.

Figure 2

Laser systems for lithium, potassium, and rubidium. All three laser systems are based on semiconductor lasers. The frequencies are shifted with double pass (dp), quadruple pass (qp), and tandem (td) AOM lines.

Figure 3

Typical loading sequence of the $\mathrm{Li}+\mathrm{K}+\mathrm{Rb}$ triple MOT. Trapping of Rb and K is controlled by switching the corresponding repumping beam on or off. In the case of Li the atomic loading beam from the Zeeman slower is blocked and unblocked by a mechanical shutter. The atom numbers are monitored by calibrated fluorescence detection.