Manipulation of cold atoms by an adaptable magnetic reflector |
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Authors: | P Rosenbusch BV Hall IG Hughes CV Saba EA Hinds |
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Institution: | (1) Sussex Centre for Optical and Atomic Physics, University of Sussex, Brighton BN1 9QH, UK, UK |
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Abstract: | Adaptive optics for cold atoms has been experimentally realized by applying a bias magnetic field to a static magnetic mirror.
The mirror consist of a 12-mm-diameter piece of commercial videotape, having a sine wave of wavelength 25.4 μm recorded in
a single track across its width, curved to form a concave reflector with radius of curvature R=54 mm. We have studied the
performance of the mirror by monitoring the evolution of a 24 μK cloud of 85Rb atoms bouncing on it. A uniform static external magnetic field was added to the mirror field causing a corrugated potential
from which the atoms bounce with increased angular spread. The characteristic angular distribution of the surface normal is
mapped at the peak of the bounce for atoms dropped from a height of R/2 and at the peak of the second bounce for a drop height
of R/4. In a second experiment a time-dependent magnetic field was applied and the angular distribution of the cloud was measured
as a function of field frequency. In this scheme we demonstrate a corrugated potential whose time-dependent magnitude behaves
like a diffraction grating of variable depth. Finally a rotating field was added to generate a corrugated potential that moves
with a velocity given by the product of the external field rotation frequency and the videotape wavelength. This travelling
grating provides a new method of manipulation as cold atoms are transported across the surface by surfing along the moving
wave. Two theoretical methods have been developed to predict the behaviour of atoms reflecting from these stationary, variable
magnitude and moving corrugated potentials. A simple analytic theory provides excellent agreement for reflection from a stationary
corrugated potential and gives good agreement when extended to the case of a travelling grating. A Monte Carlo simulation
was also performed by brute force numeric integration of the equations of motion for atoms reflecting from all three corrugated
potential cases.
Received: 1 December 1999 / Revised version: 3 February 2000 / Published online: 5 April 2000 |
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Keywords: | PACS: 32 80 Pj 03 75 Be 39 10 +J |
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