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Quantum Electronics and Laser Science Conference

Channeling of cold atoms along a Laguerre-Gaussian light beam

Gavin P. T. Lancaster, M. A. Clifford, Kishan Dholakia

Published May 12, 2000• 0 citations
OpenAlex

Abstract

Summary form only given. Extracting cold atoms from a magneto-optical trap (MOT) has been the subject of central interest in recent years. This has seen the emergence of the area of atom guiding along hollow core optical fibers and also along light beams. The guiding and the extraction of cold atoms is of central importance in generating bright, high flux atomic sources for various experiments in atom optics. In this paper we describe and experimentally realize a scheme for extracting cold atoms directly from a magnetooptical trap along a Laguerre-Gaussian light beam.

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Summary form only given. Recent advances in cold atom physics have seen the emergence of the area of atom guiding along hollow core optical fibres and also along light beams. Both employ the optical dipole force which for suitably tuned light can restrict the atoms to the dark hollow region of the fibre or the light beam. In this work, we discuss and analyse a novel scheme of channelling cold atoms into a high-order Bessel beam (via a high-order Laguerre-Gaussian beam) and demonstrate an efficient method of producing such beams.

Quantum Electronics and Laser Science Conference•Jan 20, 2003•0 citations

Optimized coupling of cold atoms into a fiber using a blue-detuned hollow-beam funnel

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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.

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Experimental studies of cold atom guiding using hollow light beams

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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

Atom motion in Laguerre-Gaussian doughnut beams

M. E. J. Friese, J.A. Andersen, Halina H. Rubinsztein-Dunlop

Summary form only given. Preparation of slow atomic beams has applications in experiments such as lithography, atom interferometry and in general for transporting atoms, for example from one vacuum chamber to another. Optical methods together with hollow fibers have been successfully employed to transport atoms, and all-optical methods using far off-resonant dipole forces have recently attracted much interest. Such all-optical methods have advantages in that far off-resonant dipole traps have potentially very low scattering rates, especially blue detuned hollow beam traps where atoms are restricted to low intensity regions where perturbations due to the light field are minimum. Optical atom guides also have practical advantages in that they can be switched, and can be easily introduced into high vacuum apparatus. Blue detuned hollow laser beams generated from a hollow optical fiber have been used to guide atoms (Xu et al, 1999; Babiker et al, 1994), and holographically generated doughnut beams have been used to guide and focus a cold beam of metastable neon atoms. In our experiments, we investigate the motion of cold rubidium atoms in far-detuned and near-resonant doughnut beams.

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All optical guiding and splitting of a cold atomic beam

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Summary form only given. The widespread use of magneto-optical traps (MOT) and the development of BEC over the last 10 years have led to the field of atom optics. This field requires the use of equivalent elements to optical mirrors, lenses and beam splitters. The generation of a large deviation atomic beam splitter is one of the most important goals, as it allows the construction of atom interferometers. Optical methods for achieving these elements are enticing, as the use of laser beams would make it easier to alter parameters of your guides within a vacuum chamber. Recent work has demonstrated the use of optical beams to guide and split atoms from a cold atom source. Here we present novel experimental studies of the optical guiding (in both the red- and blue-detuned regime) of a low-velocity intense source (LVIS) of atoms emanating from a rubidium MOT.

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Long-distance channeling of cold atoms exiting a 2D magneto-optical trap by a Laguerre–Gaussian laser beam

Vincent Carrat, Citlali Cabrera-Gutiérrez, Marion Jacquey +3 more

Using a blue-detuned laser, shaped into a nearly Laguerre-Gaussian (LG) donut mode, we channel atoms exiting a two-dimensional magneto-optical trap (2D-MOT) over a 30 cm distance. Compared to a freely propagating beam, the atomic flux (∼10(10) at/s) is conserved whereas the divergence is reduced from 40 to 3 mrad. So, 30 cm far the 2D-MOT exit, the atomic beam has a 1 mm diameter and the atomic density is increased by a factor of ∼200. The LG-channeled-2D-MOT has been studied versus the order of the LG mode (from 2 to 10) and versus the laser-atom frequency detuning (from 2 to 120 GHz).

Optics Letters•Jan 30, 2014•24 citations
Summary form only given. Extracting cold atoms from a magneto-optical trap (MOT) has been the subject of central interest in recent years. This has seen the emergence of the area of atom guiding along hollow core optical fibers and also along light beams. The guiding and the extraction of cold atoms is of central importance in generating bright, high flux atomic sources for various experiments in atom optics. In this paper we describe and experimentally realize a scheme for extracting cold atoms directly from a magnetooptical trap along a Laguerre-Gaussian light beam.
Summary form only given. Recent advances in cold atom physics have seen the emergence of the area of atom guiding along hollow core optical fibres and also along light beams. Both employ the optical dipole force which for suitably tuned light can restrict the atoms to the dark hollow region of the fibre or the light beam. In this work, we discuss and analyse a novel scheme of channelling cold atoms into a high-order Bessel beam (via a high-order Laguerre-Gaussian beam) and demonstrate an efficient method of producing such beams.
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.
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.
Summary form only given. Preparation of slow atomic beams has applications in experiments such as lithography, atom interferometry and in general for transporting atoms, for example from one vacuum chamber to another. Optical methods together with hollow fibers have been successfully employed to transport atoms, and all-optical methods using far off-resonant dipole forces have recently attracted much interest. Such all-optical methods have advantages in that far off-resonant dipole traps have potentially very low scattering rates, especially blue detuned hollow beam traps where atoms are restricted to low intensity regions where perturbations due to the light field are minimum. Optical atom guides also have practical advantages in that they can be switched, and can be easily introduced into high vacuum apparatus. Blue detuned hollow laser beams generated from a hollow optical fiber have been used to guide atoms (Xu et al, 1999; Babiker et al, 1994), and holographically generated doughnut beams have been used to guide and focus a cold beam of metastable neon atoms. In our experiments, we investigate the motion of cold rubidium atoms in far-detuned and near-resonant doughnut beams.
Summary form only given. The widespread use of magneto-optical traps (MOT) and the development of BEC over the last 10 years have led to the field of atom optics. This field requires the use of equivalent elements to optical mirrors, lenses and beam splitters. The generation of a large deviation atomic beam splitter is one of the most important goals, as it allows the construction of atom interferometers. Optical methods for achieving these elements are enticing, as the use of laser beams would make it easier to alter parameters of your guides within a vacuum chamber. Recent work has demonstrated the use of optical beams to guide and split atoms from a cold atom source. Here we present novel experimental studies of the optical guiding (in both the red- and blue-detuned regime) of a low-velocity intense source (LVIS) of atoms emanating from a rubidium MOT.
Using a blue-detuned laser, shaped into a nearly Laguerre-Gaussian (LG) donut mode, we channel atoms exiting a two-dimensional magneto-optical trap (2D-MOT) over a 30 cm distance. Compared to a freely propagating beam, the atomic flux (∼10(10) at/s) is conserved whereas the divergence is reduced from 40 to 3 mrad. So, 30 cm far the 2D-MOT exit, the atomic beam has a 1 mm diameter and the atomic density is increased by a factor of ∼200. The LG-channeled-2D-MOT has been studied versus the order of the LG mode (from 2 to 10) and versus the laser-atom frequency detuning (from 2 to 120 GHz).