Novel Optical Trap of Atoms with a Doughnut Beam

Abstract

We have constructed a novel optical trap for neutral atoms by using a Laguerre-Gaussian (doughnut) beam whose frequency is blue detuned to the atomic transition. Laser-cooled rubidium atoms are trapped in the dark core of the doughnut beam with the help of two additional laser beams which limit the atomic motion along the optical axis. About 10 8 atoms are initially loaded into the trap, and the lifetime is 150 ms. Because the atoms are confined at a point in a weak radiation field in the absence of any external field, ideal circumstances are provided for precision measurements. The trap opens the way to a simple technique for atom manipulation, including Bose-Einstein condensation of gaseous atoms.[S0031-9007 (97)03456-X] PACS numbers: 32.80.Pj, 39.90. + d

A single hollow-beam optical trap for cold atoms

“…Geometric optics allows quantitative understanding of the shape and size of the trapping potential. The dark volume can be as large as 80 mm 3 and we have trapped up to one million atoms in it.…”

“…The first traps of this kind used multiple laser beams to provide a closed trapping volume for the atoms. Sodium atoms were captured in between sheets of laser light [1], cesium atoms were stored in a trap that uses gravity and a combination of an evanescent wave and a hollow beam [2], and rubidium atoms were trapped inside a doughnut beam closed by additional laser beams along the direction of propagation [3]. More recently, three far off resonant traps for cold atoms that use a single laser beam were demonstrated experimentally.…”

Airborne ultrasonic vortex generation using flexible ferroelectrets

“…In this sense, it has been demonstrated that a helical wavefront transports angular moment [4], which makes it possible to control the orientation of absorbent particles in an optical tweezer [5]. Applications to trap atoms have also been proposed [6].…”

Cavity-enhanced toroidal dipole force traps for dark-field seeking species

“…Single standing-wave cavity modes are however suitable only for reddetuned (high-field seeking) traps, for the exact cancellation of the forward and backward travelling beams produces nodal surfaces of zero intensity along which dark-field seeking species would escape. Laguerre-Gaussian modes of a travellingwave cavity allow confinement in two dimensions [20][21][22][23], although the translational symmetry prohibits intrinsic axial confinement, which must be provided by additional beams [14].…”

“…Zema anek and Foot [12] have shown how a line of www.elsevier.com/locate/optcom traps might be formed by the interference between counter-propagating Gaussian beams of differently sized but coincident waists. Other schemes use complex beams such as Laguerre-Gaussians and their superpositions, produced using cylindrical optics [13,14], waveplates [9] or, more robustly, holographic mode-converters [15,16].…”