Cold atom confinement in hollow laser beams with high charge number

Xinye Xu, Kihwan Kim, Wonho Jhe

Hiroki Hirano, Kazuki Horiguchi, Hi Tou +1 more

Yitong Song, W. T. Hill

Summary form only given. One of the more promising proposals for guiding and focusing neutral atoms involves dark hollow laser beams. When detuned blue of resonance, the dipole force the atoms feel in the light confines them to the dark core of the beam where they can be transported with minimal interaction with the light. Dark hollow beams show promise for long distance transport of large numbers of ultra cold atoms, making them a strong competitor with hollow-core fiber atom guides. In this presentation we describe a simple way to construct an all-light atom tunnel with a series of axicons and a moderately powered diode laser beam.

Jérôme Poulin, P. S. Light, Raman Kashyap +1 more

We theoretically investigate the process of coupling cold atoms into the core of a hollow-core photonic-crystal optical fiber using a blue-detuned Laguerre-Gaussian beam. In contrast to the use of a red-detuned Gaussian beam to couple the atoms, the blue-detuned hollow beam can confine cold atoms to the darkest regions of the beam, thereby minimizing shifts in the internal states and making the guide highly robust to heating effects. This single optical beam is used as both a funnel and a guide to maximize the number of atoms into the fiber. In the proposed experiment, Rb atoms are loaded into a magneto-optical trap (MOT) above a vertically oriented optical fiber. We observe a gravito-optical trapping effect for atoms with high orbital momentum around the trap axis, which prevents atoms from coupling to the fiber: these atoms lack the kinetic energy to escape the potential and are thus trapped in the laser funnel indefinitely. We find that by reducing the dipolar force to the point at which the trapping effect just vanishes, it is possible to optimize the coupling of atoms into the fiber. Our simulations predict that by using a low-power (2.5 mW) and far-detuned (300 GHz) Laguerre-Gaussian beam with a 20-$\ensuremath{\mu}$m-radius core hollow fiber, it is possible to couple 11% of the atoms from a MOT 9 mm away from the fiber. When the MOT is positioned farther away, coupling efficiencies over 50% can be achieved with larger core fibers.

V. I. Balykin, Vladilen S Letokhov, Vladimir G. Minogin +1 more