Gravito-optical atom trap based on a conical hollow beam

Abstract

We demonstrate a novel optical dipole-force trap, which uses an intense blue-detuned conical hollow laser beam together with gravity to confine an ensemble of cesium atoms in a dark spatial region. Efficient cooling is provided by a 3D optical molasses in combination with inelastic reflections from the trapping field. The particular advantages of the trap are its experimental simplicity, the high loading efficiency, and a strong suppression of losses caused by ultracold collisions.

Optimized coupling of cold atoms into a fiber using a blue-detuned hollow-beam funnel

“…Similar gravito-optical traps based on blue-detuned hollow-beams have been previously reported [39,40], although their intention was to trap the atoms whereas we are trying to avoid this. Under our set of conditions, the axial component of the blue-detuned repulsive force, opposing gravity, is only effective for atoms with higher transverse energy.…”

Dipole force trapping of caesium atoms

“…The laser light was far-blue detuned, thus ensuring a long trap lifetime against photon scattering. The use of an axicon lens as in the work of Ovchinnicov et al [5] was also considered, but numerical calculations of the diffraction integrals showed that this geometry gives interference fringes so that the light field beyond the focus consists of many concentric, coaxial tubes of light-this could be the reason why a long cigar-shaped cloud was observed by Ovchinnicov et al, rather than a conical shape defined by the geometrical ray path. This interference is somewhat like a Young's slit experiment with cylindrical symmetry, i.e.…”

“…A blue-detuned trap using near-resonant light has been realized for caesium atoms by Ovchinnicov et al [5]. The problem of heating during loading was overcome by using a Sisyphus cooling mechanism that produced inelastic reflections from the 'walls' of the light potential [6].…”

Projection of diffraction patterns for use in cold-neutral-atom trapping

“…The difference between the various pursuits within the field of trapping cold neutral atoms is determined by the optical methods employed to create laser light fields with localized maxima or minima. Various methods to create localized high-or low-intensity fields have included the focusing of a single laser beam [4] to create a single trap at the focal spot; using the periodic interference pattern of counterpropagating beams to create one-dimensional [5], two-dimensional [6], and three-dimensional [7] arrays of optical traps; using axicons [8] or Laguerre-Gaussian beams [9] to create localized dark regions; using evanescent-wave traps [10]; using the interference of different evanescent waves outside of a waveguide from different propagation modes within the waveguide to create one-and two-dimensional arrays of optical traps [11].…”