Figure 1

(a) Exemplary potentials of the weak hybrid trap for ${}^{87}\mathrm{Rb}$ atoms in the three different substates $|F=1,m_F=-1;0;+1\rangle$ (from top to bottom) as a function of the distance in axial direction to the minimum beam radius $w_0=53\hspace{0.5em}\mu$m of the ODT. The minimum trap depth is $U_0=k_B\times 190$ $\mathrm{\mu }$K and the potentials were calculated for a gradient of the magnetic quadrupole field of 10 G/cm and a spatial offset between the centers of ODT and quadrupole field of 200 $\mathrm{\mu }$m. Absorption images of a cloud of $2\times {10}^6$ atoms (b) in the single-beam ODT and (c) in the weak hybrid trap after 1 ms of free expansion reveal the corresponding density profiles. The enhancement of the atomic density in the weak hybrid trap is clearly visible. Furthermore, the density distribution of the atomic cloud in the weak hybrid trap (c) is composed of two Gaussian density distributions, where the narrower distribution (lower blue line) represents atoms in $|m_F=-1\rangle$ experiencing the additional magnetic confinement. On the other hand, atoms in the magnetic-field-insensitive spin state $|m_F=0\rangle$ (upper green line) only experience the ODT potential and thus show a broader density distribution. Atoms in $|m_F=+1\rangle$ are repelled from the auxiliary magnetic field, as shown in (a). (d) Sketch of the experimental setup seen from the top with the two coils for generating the magnetic quadrupole field (1) and four of the six telescopes for shaping the cooling laser beams of the 3D MOT (2).Reuse & Permissions

Figure 2

Comparison of the evolution of phase-space density in the single-beam ODT (open circles) and in the weak hybrid trap (solid circles) during forced evaporative cooling. The power of the ODT laser beam is reduced using a Pockels cell and a subsequent Glan laser polarizer. Lines are guides to the eye.Reuse & Permissions

Figure 3

Absorption images and corresponding density profiles of atomic clouds at different temperatures released from the weak hybrid trap. The time-of-flight for each picture is 21 ms and the phase transition from a thermal gas in (a) to a bimodal density distribution in (b) to a quasipure BEC in (c) is clearly visible. The quasipure BEC consists of ${10}^4$ atoms.Reuse & Permissions