Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

International Laser Science Conference

Dipole laser trap for neutral atoms

P. L. Gould, Alan L. Migdall, H. Metcalf, William D. Phillips

Published Jan 1, 1986• 0 citations
Publisher

Abstract

We describe a relatively large volume dipole laser trap for the confinement of sodium atoms. Two counterpropagating beams, tuned below resonance, with foci separated by approximately one con focal parameter, provide radial confinement via the dipole force and axial confinement by balancing the radiation pressures of the two beams.1 Identical circular polarization for both beams prevents optical pumping and serves to maintain a two-state system. Alternation of the two beams2 is necessary to avoid the effects of standing-wave heating. Additionally, the trapping cycle is alternated with a Doppler cooling cycle2 to achieve low temperatures and long confinement times. Trapping beams of 100 mW focused to 50-μm spot radii and detuned ~2 GHz below the F = 2 to F′= 3 transition of the D2 line provide a well depth of 50 mK and a confinement volume of 10-4 cm3. Analysis of atomic motion and escape mechanisms as well as progress toward the experimental realization of this trap is presented.

DOI
10.1364/ils.1986.wf3

Related papers

Three-dimensional viscous confinement and cooling of atoms by resonance radiation pressure

Steven Chu, Leo W. Hollberg, John E. Bjorkholm +2 more

We report the viscous confinement and cooling of neutral sodium atoms in three dimensions via the radiation pressure of counterpropagating laser beams. These atoms have a density of about \ensuremath{\sim}${10}^{6}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ and a temperature of \ensuremath{\sim}240 \ensuremath{\mu}K corresponding to a rms velocity of \ensuremath{\sim}60 cm/sec. This temperature is approximately the quantum limit for this atomic transition. The decay time for half the atoms to escape a \ensuremath{\sim}0.2${\mathrm{cm}}^{3}$ confinement volume is \ensuremath{\sim}0.1 sec.

Physical Review Letters•Jul 1, 1985•852 citations

Laser cooling, stopping, and magnetic trapping of neutral atoms

William D. Phillips

A thermal atomic Na beam is opposed by a resonantly tuned laser beam. The radiation pressure decelerates and compresses the thermal velocity distribution, bringing the average velocity to zero and reducing the width from ~1000 m/s to a few tens of m/s or less.1 The density of stopped atoms is > 106/cm3 within a bandwidth of a few m/ s. These densities and velocities are suitable for trapping by a number of proposed optical and magnetic traps. Using these stopped atoms, we have demonstrated the first electromagnetic trapping of neutral atoms. The trap, a magnetic quadrupole formed by two separated, coaxial, opposed current loops, confines the atoms by virtue of the force exerted on the Na magnetic dipole moment by the inhomogeneous magnetic field. The time constant for exponential decay of the atomic population in the trap is 0.83(7) s and is limited mainly by collisions with fast background gas atoms. The maximum velocity of atoms contained in the trap is 3.5 m/s, corresponding to a maximum energy of 17 mK.

Annual Meeting Optical Society of America•Jan 1, 1985•0 citations

Novel dipole-force atom traps

Inka B. Manek-Hönninger, U. Moslener, Yu. B. Ovchinnikov +5 more

We discuss our recent experimental demonstrations of three novel atom traps which are all based on the optical dipole force in far-detuned laser light. In the gravito-optical surface trap (GOST), Cs atoms are trapped and cooled by means of an evanescent-wave mirror very closely above a dielectric surface. This trap allows for optical cooling at very high densities and provides good starting conditions for evaporative cooling to quantum degeneracy and the realization of a 2D quantum gas. The conical atom trap (CAT) uses a hollow blue-detuned laser beam in combination with gravity to trap atoms in a dark spatial region. This trap is experimentally simple and provides high loading efficiency, tight confinement, efficient sub-Doppler cooling, and strong suppression of collisional losses. The standing-wave red-detuned (STAR) trap allows one to confine atoms in a shallow optical potential at a very low photon scattering rate, and is thus an interesting tool for studies of the atomic ground-state dynamics in external electro-magnetic fields. We have studied atomic spin polarization in this trap.

International Conference on Atomic Physics (ICAP)•Jan 1, 1999•0 citations

Confinement of neutral atoms

P. van der Straten, Harold J. Metcalf

In order to confine any object, it is necessary to exchange kinetic for potential energy in the trapping field, and in neutral atom traps, the potential energy must be stored as internal atomic energy. Thus practical traps for ground-state neutral atoms are necessarily very shallow compared with thermal energy because the energy level shifts that result from conveniently sized fields are typically considerably smaller than k B T , even for T = 1 K. Neutral atom trapping therefore depends on substantial cooling of a thermal atomic sample, and is often connected with the cooling process. In most practical cases, atoms are loaded from magneto-optical traps, where they have been efficiently accumulated and cooled to mK temperatures (see Sec. 20.3), or from optical molasses, where they have been optically cooled to μK temperatures (see Sec. 19.4). The small depth of typical neutral atom traps dictates stringent vacuum requirements, because an atom cannot remain trapped after a collision with a thermal energy background gas molecule. Since these atoms are vulnerable targets for thermal energy background gas, the mean free time between collisions must exceed the desired trapping time. The cross-section for destructive collisions is quite large because even a gentle collision (i.e. large impact parameter) can impart enough energy to eject an atom from a trap. At pressure P sufficiently low to be of practical interest, the trapping time is ~(10 -8 / P ) s, where P is in torr. This chapter begins with a discussion of ordinary, single-center traps, but also considers arrays of traps. Such “optical lattices” are playing an increasingly important role in research in atomic physics, so discussion of their properties is an appropriate part of the education of a student of the subject. Dipole force optical traps Single-beam optical traps for two-level atoms The simplest imaginable optical trap consists of a single, strongly focused Gaussian laser beam (see Fig. 20.1) [214, 215] whose intensity at the focus varies transversely with r as where is the beam waist size. Such a trap has a well-studied and important macroscopic classical analog in a phenomenon called optical tweezers (see App. 1.C) [216–218].

Cambridge University Press eBooks•Dec 31, 2015•0 citations

Observation of Focusing of Neutral Atoms by the Dipole Forces of Resonance-Radiation Pressure

John E. Bjorkholm, Richard R. Freeman, Arthur Ashkin +1 more

For sodium atoms in an atomic beam, we demonstrate focusing, defocusing, and steering caused by the transverse dipole forces exerted by the radial intensity gradient of a superimposed and co-propagating resonant cw light beam. Dipole radiation-pressure forces differ from the forces due to spontaneous emission and are needed to achieve optical traps for neutral atoms.

Physical Review Letters•Nov 13, 1978•266 citations

Theory of an optical dipole trap for cold atoms

B. M. Garraway, Vladimir G. Minogin

The theory of an atom dipole trap composed of a focused, far red-detuned, trapping laser beam, and a pair of red-detuned, counterpropagating, cooling beams is developed for the simplest realistic multilevel dipole interaction scheme based on a model of a (3+5)-level atom. The description of atomic motion in the trap is based on the quantum kinetic equations for the atomic density matrix and the reduced quasiclassical kinetic equation for atomic distribution function. It is shown that when the detuning of the trapping field is much larger than the detuning of the cooling field, and with low saturation, the one-photon absorption (emission) processes responsible for the trapping potential can be well separated from the two-photon processes responsible for sub-Doppler cooling atoms in the trap. Two conditions are derived that are necessary and sufficient for stable atomic trapping. The conditions show that stable atomic trapping in the optical dipole trap can be achieved when the trapping field has no effect on the two-photon cooling process and when the cooling field does not change the structure of the trapping potential but changes only the numerical value of the trapping potential well. It is concluded that the separation of the trapping and cooling processes in a pure optical dipole trap allows one to cool trapped atoms down to a minimum temperature close to the recoil temperature, keeping simultaneously a deep potential well.

Physical Review A•Sep 15, 2000•11 citations
We describe a relatively large volume dipole laser trap for the confinement of sodium atoms. Two counterpropagating beams, tuned below resonance, with foci separated by approximately one con focal parameter, provide radial confinement via the dipole force and axial confinement by balancing the radiation pressures of the two beams.1 Identical circular polarization for both beams prevents optical pumping and serves to maintain a two-state system. Alternation of the two beams2 is necessary to avoid the effects of standing-wave heating. Additionally, the trapping cycle is alternated with a Doppler cooling cycle2 to achieve low temperatures and long confinement times. Trapping beams of 100 mW focused to 50-μm spot radii and detuned ~2 GHz below the F = 2 to F′= 3 transition of the D2 line provide a well depth of 50 mK and a confinement volume of 10-4 cm3. Analysis of atomic motion and escape mechanisms as well as progress toward the experimental realization of this trap is presented.
We report the viscous confinement and cooling of neutral sodium atoms in three dimensions via the radiation pressure of counterpropagating laser beams. These atoms have a density of about \ensuremath{\sim}106{10}^{6}106 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ and a temperature of \ensuremath{\sim}240 \ensuremath{\mu}K corresponding to a rms velocity of \ensuremath{\sim}60 cm/sec. This temperature is approximately the quantum limit for this atomic transition. The decay time for half the atoms to escape a \ensuremath{\sim}0.2cm3{\mathrm{cm}}^{3}cm3 confinement volume is \ensuremath{\sim}0.1 sec.
A thermal atomic Na beam is opposed by a resonantly tuned laser beam. The radiation pressure decelerates and compresses the thermal velocity distribution, bringing the average velocity to zero and reducing the width from ~1000 m/s to a few tens of m/s or less.1 The density of stopped atoms is > 106/cm3 within a bandwidth of a few m/ s. These densities and velocities are suitable for trapping by a number of proposed optical and magnetic traps. Using these stopped atoms, we have demonstrated the first electromagnetic trapping of neutral atoms. The trap, a magnetic quadrupole formed by two separated, coaxial, opposed current loops, confines the atoms by virtue of the force exerted on the Na magnetic dipole moment by the inhomogeneous magnetic field. The time constant for exponential decay of the atomic population in the trap is 0.83(7) s and is limited mainly by collisions with fast background gas atoms. The maximum velocity of atoms contained in the trap is 3.5 m/s, corresponding to a maximum energy of 17 mK.
We discuss our recent experimental demonstrations of three novel atom traps which are all based on the optical dipole force in far-detuned laser light. In the gravito-optical surface trap (GOST), Cs atoms are trapped and cooled by means of an evanescent-wave mirror very closely above a dielectric surface. This trap allows for optical cooling at very high densities and provides good starting conditions for evaporative cooling to quantum degeneracy and the realization of a 2D quantum gas. The conical atom trap (CAT) uses a hollow blue-detuned laser beam in combination with gravity to trap atoms in a dark spatial region. This trap is experimentally simple and provides high loading efficiency, tight confinement, efficient sub-Doppler cooling, and strong suppression of collisional losses. The standing-wave red-detuned (STAR) trap allows one to confine atoms in a shallow optical potential at a very low photon scattering rate, and is thus an interesting tool for studies of the atomic ground-state dynamics in external electro-magnetic fields. We have studied atomic spin polarization in this trap.
In order to confine any object, it is necessary to exchange kinetic for potential energy in the trapping field, and in neutral atom traps, the potential energy must be stored as internal atomic energy. Thus practical traps for ground-state neutral atoms are necessarily very shallow compared with thermal energy because the energy level shifts that result from conveniently sized fields are typically considerably smaller than k B T , even for T = 1 K. Neutral atom trapping therefore depends on substantial cooling of a thermal atomic sample, and is often connected with the cooling process. In most practical cases, atoms are loaded from magneto-optical traps, where they have been efficiently accumulated and cooled to mK temperatures (see Sec. 20.3), or from optical molasses, where they have been optically cooled to μK temperatures (see Sec. 19.4). The small depth of typical neutral atom traps dictates stringent vacuum requirements, because an atom cannot remain trapped after a collision with a thermal energy background gas molecule. Since these atoms are vulnerable targets for thermal energy background gas, the mean free time between collisions must exceed the desired trapping time. The cross-section for destructive collisions is quite large because even a gentle collision (i.e. large impact parameter) can impart enough energy to eject an atom from a trap. At pressure P sufficiently low to be of practical interest, the trapping time is ~(10 -8 / P ) s, where P is in torr. This chapter begins with a discussion of ordinary, single-center traps, but also considers arrays of traps. Such “optical lattices” are playing an increasingly important role in research in atomic physics, so discussion of their properties is an appropriate part of the education of a student of the subject. Dipole force optical traps Single-beam optical traps for two-level atoms The simplest imaginable optical trap consists of a single, strongly focused Gaussian laser beam (see Fig. 20.1) [214, 215] whose intensity at the focus varies transversely with r as where is the beam waist size. Such a trap has a well-studied and important macroscopic classical analog in a phenomenon called optical tweezers (see App. 1.C) [216–218].
The theory of an atom dipole trap composed of a focused, far red-detuned, trapping laser beam, and a pair of red-detuned, counterpropagating, cooling beams is developed for the simplest realistic multilevel dipole interaction scheme based on a model of a (3+5)-level atom. The description of atomic motion in the trap is based on the quantum kinetic equations for the atomic density matrix and the reduced quasiclassical kinetic equation for atomic distribution function. It is shown that when the detuning of the trapping field is much larger than the detuning of the cooling field, and with low saturation, the one-photon absorption (emission) processes responsible for the trapping potential can be well separated from the two-photon processes responsible for sub-Doppler cooling atoms in the trap. Two conditions are derived that are necessary and sufficient for stable atomic trapping. The conditions show that stable atomic trapping in the optical dipole trap can be achieved when the trapping field has no effect on the two-photon cooling process and when the cooling field does not change the structure of the trapping potential but changes only the numerical value of the trapping potential well. It is concluded that the separation of the trapping and cooling processes in a pure optical dipole trap allows one to cool trapped atoms down to a minimum temperature close to the recoil temperature, keeping simultaneously a deep potential well.