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

European Quantum Electronics Conference (EQEC)

Evanescent-wave trapping of Cs at the crossover to two-dimensionality

D. Rychtarik, B. Engeser, M. Hammes, Hanns‐Christoph Nägerl, Rudolf Grimm

Published Jan 1, 2003• 0 citations
Publisher

Abstract

Summary form only given. Our experiment aims at investigating a two-dimensional degenerate quantum gas of cesium atoms. For this purpose, we exploit a double evanescent-wave trap (DEW trap) consisting of a repulsive and an attractive evanescent wave and providing a highly anisotropic dipole potential. Efficient loading is accomplished by a multi-stage sequence. Cesium atoms are laser cooled in a MOT and then transferred into a gravito-optical dipole trap that serves as a surface reservoir. In the next stage, the phase-space density is enhanced by creating a dimple in the potential with a far-detuned, attractive laser beam that is focused to the center of the reservoir. Finally, we transfer the atoms into the DEW trap. The vertical dipole potential provides a well close to the surface, and depends on the power of the attractive evanescent wave. Ramping down the power of the attractive evanescent wave leads to efficient evaporation. A situation at the crossover to two-dimensionality is reached when the thermal energy of k/sub B/ /spl times/ 100 nK equals the level spacing h/spl nu/; thus the vertical ground state is populated by over 60 percent. Since the final phase-space density is as high as 0.1, the creation of a degenerate two-dimensional quantum gas of Cs comes into experimental reach. In present experiments we polarize the atoms into the F = 3, m/sub F/ = 3 state. As a consequence of the resonant interaction properties of cesium, the scattering length can be tuned in a wide range by applying a magnetic field. We use the tunability of interactions to optimize the evaporation efficiency on the way to a two-dimensional degenerate quantum gas of cesium.

DOI
10.1109/eqec.2003.1314127

Related papers

Evanescent-Wave Trapping and Evaporative Cooling of an Atomic Gas at the Crossover to Two Dimensions

M. Hammes, D. Rychtarik, B. Engeser +2 more

A dense gas of cesium atoms at the crossover to two dimensions is prepared in a highly anisotropic surface trap that is realized with two evanescent light waves. Temperatures as low as 100 nK are reached with 20,000 atoms at a phase-space density close to 0.1. The lowest quantum state in the tightly confined direction is populated by more than 60%. The system provides atoms at a mean distance from the surface as low as 1 microm, and offers intriguing prospects for future experiments on degenerate quantum gases in two dimensions.

arXiv:physics/0208065•Physical Review Letters•Apr 29, 2003•60 citations

Inverstigation on loading of the Dimple optical trap based on a magnetically levitated large-volume crossed optical dipole trap

Wang Xiao-Feng, Yuqing Li, Guosheng Feng +4 more

Optical trapping techniques and the ability to tune the atomic interactions both have made the unprecedented progress in the quantum gas research field. The major advantage of the optical trap is that the atoms are likely to be trapped at various sub-levels of the electronic ground state and the interaction strength can be controlled by Feshbach resonance. Optical trapping methods in combination with magnetic tuning of the scattering properties directly lead to the experimental achievements of Bose-Einstein condensation (BEC) of Cesium, which at first failed by using magnetic trapping approaches due to the large inelastic collision rate. The rapid loss of cesium atoms due to the inelastic two-body collisions greatly suppresses the efficient evaporative cooling to obtain a condensate. For optical production of cesium atomic BEC, it is necessary to prepare a large number of Cs atoms at specified state in an optical trap for condensation, especially for an efficient forced evaporation cooling. In this paper, we demonstrate our research on enhancing the loading rate of the atoms by using a dimple trap combined with a large-volume optical dipole trap (reservoir trap). In our work, the cold cesium atoms are prepared by a three-dimensional degenerated Raman sideband cooling, and then loaded into a large-volume crossed dipole trap by using the magnetic levitation technique. Effective load of the dimple optical trap is realized by superposing the small-volume dimple trap on the center of the largevolume optical trap. The theoretical analyses are performed for the magnetically levitated large-volume crossed dipole trap in variable magnetic field gradients and uniform bias fields. Optimal experimental values are acquired accordingly. The combined potential curve of the dimple trap, which is superimposed on the magnetically levitated large-volume dipole trap, is also given. The loading of precooled atoms from Raman sideband cooling into the magnetically levitated large-volume optical trap is measured in variable magnetic field gradients and uniform bias fields. Different loading results of the dimple trap are investigated, including direct loading after Raman sideband cooling, the large-volume optical trap and the magnetically levitated large-volume dipole trap without anti-trapping potential. Comparatively, the atomic number density is enhanced by a factor of ~15 by loading the atomic sample from the magnetically levitated large-volume dipole trap into the dimple optical trap. The experimental results lay a sound basis for the further cooling and densifying the atomic cloud through the evaporating cooling stage. This method can be used to obtain more cold atoms or a large number of Bose-Einstein condensation atoms for atomic species with large atom mass.

Acta Physica Sinica•Jan 1, 2016•0 citations

Evaporative cooling of cesium in a surface trap

M. Hammes, D. Rychtarik, В. В. Дружиніна +1 more

Summary form only given. Optical dipole traps facilitate storage of atoms independent of their magnetic sub-state. Trapping at high densities is thus not limited by two-body collisions changing the spin state of the atom, which in the particular case of cesium have so far prevented the attainment of Bose-Einstein condensation in magnetic traps. For evaporative cooling of Cs we use the gravito-optical surface trap (GOST) which consists of a horizontal evanescent-wave (EW) atom mirror in combination with a blue-detuned hollow beam (HE) for transverse confinement. Starting conditions for evaporative cooling are prepared by optical cooling, based on inelastic reflections from the EW.

Conference on Lasers and Electro-Optics•Aug 29, 2005•0 citations

Crossover to 2D in a double-evanescent wave trap

D. Rychtarik, B. Engeser, M. Hammes +2 more

\nWe report the preparation of a dense gas of cesium atoms at the\ncrossover to two-dimensionality in a highly anisotropic surface\ntrap that is realized with two evanescent light waves.\nTemperatures as low as 100 nK are reached with 20.000 atoms at a\nphase-space density close to 0.1. The lowest quantum state in the\ntightly confined direction is populated by more than 60%. The\nsystem offers intriguing prospects for future experiments on\ndegenerate quantum gases in two dimensions.\n

Journal de Physique IV (Proceedings)•Oct 1, 2004•1 citation

Evaporative Cooling of Atoms to Quantum Degeneracy in an Optical Dipole Trap

Saptarishi Chaudhuri, Sanjukta Roy, C. S. Unnikrishnan

We discuss our experimental results on forced evaporative cooling of cold rubidium 87 Rb atoms to quantum degeneracy in an Optical Dipole Trap. The atoms are first trapped and cooled in a magneto-optical trap (MOT) loaded from a continuous beam of cold atoms [1]. More than 10 10 atoms are trapped in the MOT and then about 10 8 atoms are transferred to a Quasi-Electrostatic Trap (QUEST) formed by tightly focused CO2 laser (λ = 10.6μ m ) beams intersecting at their foci in an orthogonal configuration in the horizontal plane. Before loading the atoms into the dipole trap, the phase-space density of the atomic ensemble was increased making use of sub-doppler cooling at large detuning and the temporal dark MOT technique. In a MOT the phase-space density of the atomic ensemble is six orders of magnitude less than what is required to achieve quantum degeneracy. After transferring atoms into the dipole trap efficiently, phase-space density increases by a factor of 10 3 . Further increase in phase-space density to quantum degeneracy is achieved by forced evaporative cooling of atoms in the dipole trap. The evaporative cooling process involves a gradual reduction of the trap depth by ramping down the trapping laser intensity over a second. The temperature of the cold atomic cloud was measured by time-of-flight (TOF) technique. The spatial distribution of the atoms is measured using absorption imaging. We report results of evaporative cooling in a single beam and in a crossed double-beam dipole traps. Due to the large initial phase space density, and large initial number of atoms trapped, the quantum phase transition occurs after about 600 ms of evaporative cooling in our optimized crossed dipole trap.

Journal of Physics Conference Series•Sep 1, 2007•12 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
Summary form only given. Our experiment aims at investigating a two-dimensional degenerate quantum gas of cesium atoms. For this purpose, we exploit a double evanescent-wave trap (DEW trap) consisting of a repulsive and an attractive evanescent wave and providing a highly anisotropic dipole potential. Efficient loading is accomplished by a multi-stage sequence. Cesium atoms are laser cooled in a MOT and then transferred into a gravito-optical dipole trap that serves as a surface reservoir. In the next stage, the phase-space density is enhanced by creating a dimple in the potential with a far-detuned, attractive laser beam that is focused to the center of the reservoir. Finally, we transfer the atoms into the DEW trap. The vertical dipole potential provides a well close to the surface, and depends on the power of the attractive evanescent wave. Ramping down the power of the attractive evanescent wave leads to efficient evaporation. A situation at the crossover to two-dimensionality is reached when the thermal energy of k/sub B/ /spl times/ 100 nK equals the level spacing h/spl nu/; thus the vertical ground state is populated by over 60 percent. Since the final phase-space density is as high as 0.1, the creation of a degenerate two-dimensional quantum gas of Cs comes into experimental reach. In present experiments we polarize the atoms into the F = 3, m/sub F/ = 3 state. As a consequence of the resonant interaction properties of cesium, the scattering length can be tuned in a wide range by applying a magnetic field. We use the tunability of interactions to optimize the evaporation efficiency on the way to a two-dimensional degenerate quantum gas of cesium.
A dense gas of cesium atoms at the crossover to two dimensions is prepared in a highly anisotropic surface trap that is realized with two evanescent light waves. Temperatures as low as 100 nK are reached with 20,000 atoms at a phase-space density close to 0.1. The lowest quantum state in the tightly confined direction is populated by more than 60%. The system provides atoms at a mean distance from the surface as low as 1 microm, and offers intriguing prospects for future experiments on degenerate quantum gases in two dimensions.
Optical trapping techniques and the ability to tune the atomic interactions both have made the unprecedented progress in the quantum gas research field. The major advantage of the optical trap is that the atoms are likely to be trapped at various sub-levels of the electronic ground state and the interaction strength can be controlled by Feshbach resonance. Optical trapping methods in combination with magnetic tuning of the scattering properties directly lead to the experimental achievements of Bose-Einstein condensation (BEC) of Cesium, which at first failed by using magnetic trapping approaches due to the large inelastic collision rate. The rapid loss of cesium atoms due to the inelastic two-body collisions greatly suppresses the efficient evaporative cooling to obtain a condensate. For optical production of cesium atomic BEC, it is necessary to prepare a large number of Cs atoms at specified state in an optical trap for condensation, especially for an efficient forced evaporation cooling. In this paper, we demonstrate our research on enhancing the loading rate of the atoms by using a dimple trap combined with a large-volume optical dipole trap (reservoir trap). In our work, the cold cesium atoms are prepared by a three-dimensional degenerated Raman sideband cooling, and then loaded into a large-volume crossed dipole trap by using the magnetic levitation technique. Effective load of the dimple optical trap is realized by superposing the small-volume dimple trap on the center of the largevolume optical trap. The theoretical analyses are performed for the magnetically levitated large-volume crossed dipole trap in variable magnetic field gradients and uniform bias fields. Optimal experimental values are acquired accordingly. The combined potential curve of the dimple trap, which is superimposed on the magnetically levitated large-volume dipole trap, is also given. The loading of precooled atoms from Raman sideband cooling into the magnetically levitated large-volume optical trap is measured in variable magnetic field gradients and uniform bias fields. Different loading results of the dimple trap are investigated, including direct loading after Raman sideband cooling, the large-volume optical trap and the magnetically levitated large-volume dipole trap without anti-trapping potential. Comparatively, the atomic number density is enhanced by a factor of ~15 by loading the atomic sample from the magnetically levitated large-volume dipole trap into the dimple optical trap. The experimental results lay a sound basis for the further cooling and densifying the atomic cloud through the evaporating cooling stage. This method can be used to obtain more cold atoms or a large number of Bose-Einstein condensation atoms for atomic species with large atom mass.
Summary form only given. Optical dipole traps facilitate storage of atoms independent of their magnetic sub-state. Trapping at high densities is thus not limited by two-body collisions changing the spin state of the atom, which in the particular case of cesium have so far prevented the attainment of Bose-Einstein condensation in magnetic traps. For evaporative cooling of Cs we use the gravito-optical surface trap (GOST) which consists of a horizontal evanescent-wave (EW) atom mirror in combination with a blue-detuned hollow beam (HE) for transverse confinement. Starting conditions for evaporative cooling are prepared by optical cooling, based on inelastic reflections from the EW.
We discuss our experimental results on forced evaporative cooling of cold rubidium 87 Rb atoms to quantum degeneracy in an Optical Dipole Trap. The atoms are first trapped and cooled in a magneto-optical trap (MOT) loaded from a continuous beam of cold atoms [1]. More than 10 10 atoms are trapped in the MOT and then about 10 8 atoms are transferred to a Quasi-Electrostatic Trap (QUEST) formed by tightly focused CO2 laser (λ = 10.6μ m ) beams intersecting at their foci in an orthogonal configuration in the horizontal plane. Before loading the atoms into the dipole trap, the phase-space density of the atomic ensemble was increased making use of sub-doppler cooling at large detuning and the temporal dark MOT technique. In a MOT the phase-space density of the atomic ensemble is six orders of magnitude less than what is required to achieve quantum degeneracy. After transferring atoms into the dipole trap efficiently, phase-space density increases by a factor of 10 3 . Further increase in phase-space density to quantum degeneracy is achieved by forced evaporative cooling of atoms in the dipole trap. The evaporative cooling process involves a gradual reduction of the trap depth by ramping down the trapping laser intensity over a second. The temperature of the cold atomic cloud was measured by time-of-flight (TOF) technique. The spatial distribution of the atoms is measured using absorption imaging. We report results of evaporative cooling in a single beam and in a crossed double-beam dipole traps. Due to the large initial phase space density, and large initial number of atoms trapped, the quantum phase transition occurs after about 600 ms of evaporative cooling in our optimized crossed dipole trap.
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.