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Cold atom dynamics in atomic waveguides and optical lattices.

Boon-Keng Kevin Teo

Published Jan 1, 2002• 0 citations
OpenAlex

Abstract

We have constructed a tapered magnetic atom guide that is integrated with a magneto-optical trap. We have observed atom guiding over distances of up to 20 cm. This integrated strategy is useful for loading atoms into wire guides. We have shown that tapered sections in atom guides. i.e. sections with a variable steepness of the transverse guiding potential, can reflect atoms propagating in the guide. The reflection arises from the adiabatic conservation of the action of the transverse motion; the latter can be used as a control parameter for the atom reflectivity. A method of producing a slow, dark atomic beam of atoms is demonstrated. Atoms that are extracted from a magneto-optical trap using a push beam are quickly pumped into a dark state, which does not interact with the push laser beam. This method is capable of producing atoms with a velocity of order 1 m/s. The slow atoms can be coupled into atom guides. In related research, we observe tunneling resonances of atoms in a 1D optical lattice through the measurement of the magnetization. These resonances manifest themselves as modulations in the magnetization curves. The resonances are shown to be related to the coherence properties of the atoms, and exist only under conditions where the coherence time exceeds the tunneling period of the atoms.

Related papers

Atom reflection in a tapered magnetic guide

Boon-Keng Kevin Teo, Georg A. Raithel

We have constructed a two-wire magnetic atom guide incorporating a tapered section, in which the transverse guiding potential steepens as a function of the position along the guide axis. Atoms are slowed as they move into the tapered section and can become reflected. A classical adiabatic model is used to explain the behavior. The model shows and we experimentally observe that the action of the transverse motion, which is an adiabatic invariant, can be used as a control parameter for the atom reflectivity, allowing us to selectively reflect and trap atoms with large transverse action.

Physical Review A•May 2, 2002•13 citations

Loading of a cold atomic beam into a magnetic guide

P. Cren, Christian F. Roos, Aclan, A. +2 more

We demonstrate experimentally the continuous and pulsed loading of a slow and cold atomic beam into a magnetic guide. The slow beam is produced using a vapor loaded laser trap, which ensures two-dimensional magneto-optical trapping, as well as cooling by a moving molasses along the third direction. It provides a continuous flux larger than $10^9$ atoms/s with an adjustable mean velocity ranging from 0.3 to 3 m/s, and with longitudinal and transverse temperatures smaller than $100 \mu$K. Up to $3 10^8$ atoms/s are injected into the magnetic guide and subsequently guided over a distance of 40 cm.

•Jan 1, 2002•33 citations

A Source of Cold Atoms for a Continuously Loaded Magnetic Guide

Christian F. Roos, P. Cren, Jean Dalibard +1 more

We present an intense source of 87 Rb atoms that has been set up to produce a continuous, slow and cold beam in a magnetic guide. It consists of a two-dimensional magneto-optical trap whose cooling laser power is provided by a master-oscillator tapered-amplifier system. This trap produces an atomic beam with a flux of over 10 10 atoms/s and a mean velocity of 40 m/s. The beam is recaptured by a second trap whose purpose consists in reducing the beam's velocity, in further cooling the atoms and injecting them into the magnetic guide. The article focusses on the first stage of the process described above.

arXiv:cond-mat/0212060•Physica Scripta•Jan 1, 2003•4 citations

Long, high -gradient magnetic atom guide and progress towards an atom laser.

Spencer E. Olson

The continuous injection and propagation of a cold atomic beam in a 1.7 m long high-gradient (up to 2.7 kG/cm) magnetic guide is demonstrated. Continuous injection is accomplished by side-loading a magnetic guide with atoms from a sequence of two modified magneto-optical traps. In the high-gradient portion of the guide, the guided atomic beam has a transverse temperature of 420 muK +/- 40 muK, a longitudinal temperature of 1 mK, and an average velocity of order 1 m/s. Essential for the characterization of this steady-state atomic beam, imaging methods compatible with the high field-gradients associated with this magnetic guide have been investigated and developed. By utilizing a probe laser tuned to an open transition, the fluorescence yield per atom is largely fixed throughout the trap volume, independent of the trapping field. This enables a reliable conversion of fluorescence images into atomic-density profiles. Using a fixed radio-frequency (nurf) current coupled directly onto the guide wires, continuous and selective removal of atoms with a transverse energy exceeding hnurf is demonstrated. This removal scheme is the essence of an rf filter, where the number of modes occupied by the atomic flow is reduced. Through sufficient rf-filtering, a near-single-mode guided atomic beam should be achievable, enabling basic atom-interferometric experiments. The extension of this fixed-frequency removal of atoms for continuous position-resolved evaporative cooling in a long magnetic guide is outlined. Employing an innovative gridless technique for performing Direct Simulation of rarefied gas dynamics via Monte Carlo (DSMC), the evaporative cooling process in a guided atomic beam has been simulated. Both fixed-frequency as well as variable-frequency evaporative cooling layouts have been explored and the results of these simulations are presented. The implementation of this gridless technique is presented and its benefits are briefly outlined. In parallel with the development of a continuous-wave atom laser, tools suited to manipulate cold atomic beams in atom guides have been explored. An atomic guide with a tunable aspect ratio, using rf-dressed state potentials, is presented.

•Jan 1, 2006•0 citations

Experimental studies of cold atom guiding using hollow light beams

D. P. Rhodes

This thesis is concerned with the guiding of cold atoms using optical forces, which is of great importance in the field of atom optics. Atomic beams can be used for precision sensor equipment, building nano-scale structures, construction of quantum computers and to further the understanding of the properties of atoms. Atoms are guided along light beams using the dipole force; there are two regimes under which this force works. Typically red-detuned guides are used (atoms are attracted towards the light) such guides, however, require large detuning and high powers. In this thesis we investigate the use of blue-detuned (atoms are repelled from the light) hollow light beams of moderate power (a few hundred mW) and confine atoms in the dark centre of the beams. Several magneto-optical traps (MOTs) have been constructed to exploit different guiding geometries. Hollow beams have been generated using a variety of methods; in particular the use of a computer controlled spatial light modulator (SLM) has provided great versatility and simplicity to the experimental arrangements. First, experiments were performed with a low-velocity intense source (LVIS) of atoms. A co-linear LG beam significantly enhances the observed flux, however, considerable difficulties are encountered loading atoms into oblique guides. Imaging a hole in the walls of the light tube was used to improve the loading efficiency. Second, guiding a free-falling atom cloud is performed using a non-diffracting Bessel beam. It is found that while the potential of the Bessel beam is steeper than equivalent LG beams the power distribution across the beam severely limits its usefulness. The next study investigated higher-order LG guide beams generated with an SLM. High order modes have a narrower profile so confine the atoms with less interaction with the guide beam, leading to a more natural guide (as opposed to a pushing force). Finally the SLM was used to create non-trivial beam shapes for beam splitters and interferometers.

•Jan 1, 2005•0 citations

Injection of a cold atomic beam into a magnetic guide

Christian F. Roos, P. Cren, Thierry Lahaye +2 more

We report the continuous or pulsed loading of a slow and cold atomic beam into a magnetic guide. In order to optimize the transfer into the guide, we have studied two coupling schemes. The first one is based on an auxiliary two-dimensional MOT that confines the atoms transversally before they enter the guide. However, for low atomic velocities, the atoms are strongly heated in the longitudinal direction. This limitation does not occur in the second coupling scheme which relies on magnetic confinement in the transfer zone. For this purpose, we have constructed a miniature magnetic guide located between the atomic source and the long magnetic guide. The latter scheme allows to inject atoms with velocities down to 70 cm/s into the guide.

arXiv:cond-mat/0212147•Dec 6, 2002•5 citations
We have constructed a tapered magnetic atom guide that is integrated with a magneto-optical trap. We have observed atom guiding over distances of up to 20 cm. This integrated strategy is useful for loading atoms into wire guides. We have shown that tapered sections in atom guides. i.e. sections with a variable steepness of the transverse guiding potential, can reflect atoms propagating in the guide. The reflection arises from the adiabatic conservation of the action of the transverse motion; the latter can be used as a control parameter for the atom reflectivity. A method of producing a slow, dark atomic beam of atoms is demonstrated. Atoms that are extracted from a magneto-optical trap using a push beam are quickly pumped into a dark state, which does not interact with the push laser beam. This method is capable of producing atoms with a velocity of order 1 m/s. The slow atoms can be coupled into atom guides. In related research, we observe tunneling resonances of atoms in a 1D optical lattice through the measurement of the magnetization. These resonances manifest themselves as modulations in the magnetization curves. The resonances are shown to be related to the coherence properties of the atoms, and exist only under conditions where the coherence time exceeds the tunneling period of the atoms.
We have constructed a two-wire magnetic atom guide incorporating a tapered section, in which the transverse guiding potential steepens as a function of the position along the guide axis. Atoms are slowed as they move into the tapered section and can become reflected. A classical adiabatic model is used to explain the behavior. The model shows and we experimentally observe that the action of the transverse motion, which is an adiabatic invariant, can be used as a control parameter for the atom reflectivity, allowing us to selectively reflect and trap atoms with large transverse action.
We demonstrate experimentally the continuous and pulsed loading of a slow and cold atomic beam into a magnetic guide. The slow beam is produced using a vapor loaded laser trap, which ensures two-dimensional magneto-optical trapping, as well as cooling by a moving molasses along the third direction. It provides a continuous flux larger than 10910^9109 atoms/s with an adjustable mean velocity ranging from 0.3 to 3 m/s, and with longitudinal and transverse temperatures smaller than 100μ100 \mu100μK. Up to 31083 10^83108 atoms/s are injected into the magnetic guide and subsequently guided over a distance of 40 cm.
We present an intense source of 87 Rb atoms that has been set up to produce a continuous, slow and cold beam in a magnetic guide. It consists of a two-dimensional magneto-optical trap whose cooling laser power is provided by a master-oscillator tapered-amplifier system. This trap produces an atomic beam with a flux of over 10 10 atoms/s and a mean velocity of 40 m/s. The beam is recaptured by a second trap whose purpose consists in reducing the beam's velocity, in further cooling the atoms and injecting them into the magnetic guide. The article focusses on the first stage of the process described above.
The continuous injection and propagation of a cold atomic beam in a 1.7 m long high-gradient (up to 2.7 kG/cm) magnetic guide is demonstrated. Continuous injection is accomplished by side-loading a magnetic guide with atoms from a sequence of two modified magneto-optical traps. In the high-gradient portion of the guide, the guided atomic beam has a transverse temperature of 420 muK +/- 40 muK, a longitudinal temperature of 1 mK, and an average velocity of order 1 m/s. Essential for the characterization of this steady-state atomic beam, imaging methods compatible with the high field-gradients associated with this magnetic guide have been investigated and developed. By utilizing a probe laser tuned to an open transition, the fluorescence yield per atom is largely fixed throughout the trap volume, independent of the trapping field. This enables a reliable conversion of fluorescence images into atomic-density profiles. Using a fixed radio-frequency (nurf) current coupled directly onto the guide wires, continuous and selective removal of atoms with a transverse energy exceeding hnurf is demonstrated. This removal scheme is the essence of an rf filter, where the number of modes occupied by the atomic flow is reduced. Through sufficient rf-filtering, a near-single-mode guided atomic beam should be achievable, enabling basic atom-interferometric experiments. The extension of this fixed-frequency removal of atoms for continuous position-resolved evaporative cooling in a long magnetic guide is outlined. Employing an innovative gridless technique for performing Direct Simulation of rarefied gas dynamics via Monte Carlo (DSMC), the evaporative cooling process in a guided atomic beam has been simulated. Both fixed-frequency as well as variable-frequency evaporative cooling layouts have been explored and the results of these simulations are presented. The implementation of this gridless technique is presented and its benefits are briefly outlined. In parallel with the development of a continuous-wave atom laser, tools suited to manipulate cold atomic beams in atom guides have been explored. An atomic guide with a tunable aspect ratio, using rf-dressed state potentials, is presented.
This thesis is concerned with the guiding of cold atoms using optical forces, which is of great importance in the field of atom optics. Atomic beams can be used for precision sensor equipment, building nano-scale structures, construction of quantum computers and to further the understanding of the properties of atoms. Atoms are guided along light beams using the dipole force; there are two regimes under which this force works. Typically red-detuned guides are used (atoms are attracted towards the light) such guides, however, require large detuning and high powers. In this thesis we investigate the use of blue-detuned (atoms are repelled from the light) hollow light beams of moderate power (a few hundred mW) and confine atoms in the dark centre of the beams. Several magneto-optical traps (MOTs) have been constructed to exploit different guiding geometries. Hollow beams have been generated using a variety of methods; in particular the use of a computer controlled spatial light modulator (SLM) has provided great versatility and simplicity to the experimental arrangements. First, experiments were performed with a low-velocity intense source (LVIS) of atoms. A co-linear LG beam significantly enhances the observed flux, however, considerable difficulties are encountered loading atoms into oblique guides. Imaging a hole in the walls of the light tube was used to improve the loading efficiency. Second, guiding a free-falling atom cloud is performed using a non-diffracting Bessel beam. It is found that while the potential of the Bessel beam is steeper than equivalent LG beams the power distribution across the beam severely limits its usefulness. The next study investigated higher-order LG guide beams generated with an SLM. High order modes have a narrower profile so confine the atoms with less interaction with the guide beam, leading to a more natural guide (as opposed to a pushing force). Finally the SLM was used to create non-trivial beam shapes for beam splitters and interferometers.
We report the continuous or pulsed loading of a slow and cold atomic beam into a magnetic guide. In order to optimize the transfer into the guide, we have studied two coupling schemes. The first one is based on an auxiliary two-dimensional MOT that confines the atoms transversally before they enter the guide. However, for low atomic velocities, the atoms are strongly heated in the longitudinal direction. This limitation does not occur in the second coupling scheme which relies on magnetic confinement in the transfer zone. For this purpose, we have constructed a miniature magnetic guide located between the atomic source and the long magnetic guide. The latter scheme allows to inject atoms with velocities down to 70 cm/s into the guide.