We demonstrate that dual dark magnetic-optical-traps (MOTs) have great importance in the two-species 87Rb and 40K mixture compared with dual bright MOTs. The dark MOT has a little improvement in the trapping of single-species 87Rb or 40K gases compared with bright MOT. For the case of loading two-species 87Rb and 40K simultaneously, the improvement of 40K in the dual dark MOTs is mainly from the reduction of light-assisted collision losses. The dual dark MOTs employ a pair of conical lenses to produce the hollow beam for repump laser with high efficiency. The number and density of 87Rb and 40K atoms after evaporative cooling in the hybrid magnetic trap with dark MOT loading are compared with those in bright MOT. The atoms with large number and high density make it easier to realize the quantum degenerate of Bose–Fermi mixture.
We present an efficient cooling scheme for fermionic
40K atoms, using laser light red and blue detuned with respect to the
D2 and
D1 principle flourescence lines, respectively. The cooling scheme is found to significantly increase the saturation level for loading of a
40K magneto-optical trap (MOT), resulting in increased atom numbers or decreased cycle times. While the attainable
40K atom number is approximately doubled if exclusively
40K atoms are cooled, the scheme is particularly powerful for dual-species MOTs, for example, if
40K and
87Rb atoms are cooled simultaneously in the same MOT configuration. The typical atom losses due to light-assisted hetero-nuclear collisions between
40K and
87Rb seem to be reduced giving rise to a threefold improvement of the
40K atom number as compared to that in a conventional dual-species MOT, operating merely with
D2 light. Our scheme can be a useful extension to most dual-species experiments, aiming to reach simultaneous degeneracy of both species.
We report on the simultaneous trapping of two fermionic species,
6Li and
40K, and a bosonic species,
87Rb, 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 $3.2\ifmmode\times\else\texttimes\fi{}{10}^{7}$ for
6Li, $1.5\ifmmode\times\else\texttimes\fi{}{10}^{7}$ for
40K, and $5.4\ifmmode\times\else\texttimes\fi{}{10}^{9}$ for
87Rb 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.
We present an efficient cooling scheme for fermionic
40K atoms, using laser light red and blue detuned with respect to the D2 and D1 principle fluorescence lines, respectively. The cooling scheme is found to significantly increase the saturation level for loading of a
40K magneto-optical trap (MOT), resulting in increased atom numbers or decreased cycle times. While the attainable
40K atom number is approximately doubled if exclusively
40K atoms are cooled, the scheme is particularly powerful for dual-species MOTs, for example, if
40K and
87Rb atoms are cooled simultaneously in the same MOT configuration. The typical atom losses due to light-assisted heteronuclear collisions between
40K and
87Rb seem to be reduced, giving rise to a threefold improvement of the
40K atom number as compared to that in a conventional dual-species MOT, operating merely with D2 light. Our scheme can be a useful extension to most dual-species experiments, aiming to reach simultaneous degeneracy of both species.
We report a compact experimental setup for producing a quantum degenerate mixture of Bose 23Na and Fermi 40K gases. The atoms are collected in dual dark magneto–optical traps (MOT) with species timesharing loading to reduce the light-induced loss, and then further cooled using the gray molasses technique on the D 2 line for 23Na and D 1 line for 40K. The microwave evaporation cooling is used to cool 23Na in | F = 2,mF = 2〉 in an optically plugged magnetic trap, meanwhile, 40K in | F = 9/2,mF = 9/2〉 is sympathetically cooled. Then the mixture is loaded into a large volume optical dipole trap where 23Na atoms are immediately transferred to |1,1〉 for further effective cooling to avoid the strong three-body loss between 23Na atoms in |2,2〉 and 40K atoms in |9/2,9/2〉. At the end of the evaporation in optical trap, a degenerate Fermi gas of 40K with 1.9 × 105 atoms at T/TF = 0.5 in the |9/2,9/2〉 hyperfine state coexists with a Bose–Einstein condensate (BEC) of 23Na with 8 × 104 atoms in the |1,1〉 hyperfine state at 300 nK. We also can produce the two species mixture with the tunable population imbalance by adjusting the 23Na magneto–optical trap loading time.