APS

Transverse heating due to nonadiabatic propagation of cold atoms in an atomic guide

Nathan Blanchard, Alex A. Zozulya

Published Mar 1, 2001• 0 citations

Abstract

We study propagation of cold atoms along a curved atomic guide following an arbitrary trajectory in space. Transverse energy of the atomic beam increases as the beam propagates along the guide. Our model explains results of recent experiments on optical and magnetic guiding of cold atoms.

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Transverse heating due to nonadiabatic propagation of cold atoms in an atomic guide

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APS

Transverse heating due to nonadiabatic propagation of cold atoms in an atomic guide

Nathan Blanchard, Alex A. Zozulya

Published Mar 1, 2001• 0 citations

OpenAlex

Abstract

Related papers

Transverse heating due to nonadiabatic propagation of cold atoms in an atomic guide

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Optics CommunicationsApr 1, 20014 citations

Beam propagation in magnetic atomic guides

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We study modal propagation of cold atomic gases in a straight magnetic waveguide consisting of a current wire and a uniform magnetic field. This configuration is known to generate a transverse confining potential for atoms with magnetic dipole moment oriented anti-parallel to the magnetic field. The potential has azimuthal symmetry to first order in powers of the atomic distance to the waveguide axis. We obtain the modal dispersion curves by means of the WKB quantization method, and introduce a parameter Q that characterizes symmetric atomic waveguides as the parameter V does in optical fibers. We simulate propagation of cold atomic beams by means of the BPM (Beam Propagation Method) and show the spatial evolution of transverse monomode and multimode profiles obtained for different values of Q and arbitrary input beam profiles. We demonstrate, analytically and numerically, the existence of a threshold Q-value for guidance of matter waves analogous to the V-threshold for propagation in a TE00 mode in optical fibers and obtain that, under the experimental conditions reported in the literature, the already observed Gaussian profile of guided atomic beams corresponds to multimode propagation. RIAO/OPTILAS'04.We study modal propagation of cold atomic gases in a straight magnetic waveguide consisting of a current wire and a uniform magnetic field. This configuration is known to generate a transverse confining potential for atoms with magnetic dipole moment oriented anti-parallel to the magnetic field. The potential has azimuthal symmetry to first order in powers of the atomic distance to the waveguide axis. We obtain the modal dispersion curves by means of the WKB quantization method, and introduce a parameter Q that characterizes symmetric atomic waveguides as the parameter V does in optical fibers. We simulate propagation of cold atomic beams by means of the BPM (Beam Propagation Method) and show the spatial evolution of transverse monomode and multimode profiles obtained for different values of Q and arbitrary input beam profiles. We demonstrate, analytically and numerically, the existence of a threshold Q-value for guidance of matter waves analogous to the V-threshold for propagation in a TE00 mode in optical fibers and obtain that, under the experimental conditions reported in the literature, the already observed Gaussian profile of guided atomic beams corresponds to multimode propagation. RIAO/OPTILAS'04.

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Continuous propagation and energy filtering of a cold atomic beam in a long high-gradient magnetic atom guide

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Jianping Yin, Yifu Zhu, Wonho Jhe +1 more

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Physical Review AJul 1, 1998107 citations

Effect of transverse guiding on the velocity distribution of an atomic beam

Mara Goff Prentiss, A. Cable, N. P. Bigelow

We have observed that the transverse guiding that results when an intense light field with a Gaussian intensity distribution is superimposed upon an atomic beam can increase the total number of atoms in the beam and select atoms according to transverse velocity. This guiding preferentially retains atoms with small longitudinal velocities; consequently the expected value of the longitudinal velocity will decrease, even though no particular atom is slowed. The density of cold atoms in an atomic beam that has been slowed and cooled by a strong standing-wave field can be enhanced by such a process since the standing wave provides its own transverse guide.We have observed that the transverse guiding that results when an intense light field with a Gaussian intensity distribution is superimposed upon an atomic beam can increase the total number of atoms in the beam and select atoms according to transverse velocity. This guiding preferentially retains atoms with small longitudinal velocities; consequently the expected value of the longitudinal velocity will decrease, even though no particular atom is slowed. The density of cold atoms in an atomic beam that has been slowed and cooled by a strong standing-wave field can be enhanced by such a process since the standing wave provides its own transverse guide.

Journal of the Optical Society of America BNov 1, 19899 citations

We demonstrate the continuous injection and propagation of a cold atomic beam in a high-gradient (up to

2.7\phantom{\rule{0.3em}{0ex}}\mathrm{kG}∕\mathrm{cm}

) magnetic guide of

1.7\phantom{\rule{0.3em}{0ex}}\mathrm{m}

length. Continuous injection is accomplished using a side-loading scheme that involves a sequence of two modified magneto-optic traps. Methods are developed to measure the atomic-flow temperatures and the flux under steady-state conditions. In the high-gradient portion of the guide, the guided atomic beam has a transverse temperature of $420\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}\ifmmode\pm\else\textpm\fi{}40\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$, a longitudinal temperature of

1\phantom{\rule{0.3em}{0ex}}\mathrm{mK}

, and an average velocity of order

1\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s}

. Using a radio-frequency current of a fixed frequency $\ensuremath{\nu}$ coupled directly into the guide wires, atoms exceeding a transverse energy of $h\ensuremath{\nu}$ can be continuously and selectively removed from the atomic beam.

We propose and analyze theoretically a scheme for atomic guiding and cooling in a dark hollow laser beam generated from the collimated output beam of a

{\mathrm{LP}}_{01}

mode in a micrometer-sized hollow optical fiber. In the scheme, cold atoms from a magneto-optical trap are loaded into the blue-detuned dark hollow beam, move down in the dark hollow beam, and experience transverse Sisyphus cooling induced by the dark hollow beam and a weak repumping beam. In the longitudinal direction, the guided atoms experience heating from the gravity field and cooling from the upward-propagating dark hollow beam and repumping beam. We estimate the transverse two-dimensional equilibrium temperature, the final longitudinal mean velocity, and the total loss of the guided atoms. Our calculations show that a transverse equilibrium temperature of $\ensuremath{\sim}1.2\ensuremath{\mu}\mathrm{K},$ a final longitudinal mean velocity of 0--4.41 m/s, and a guiding efficiency of 65--95 % may be obtained.