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

Physical Review A

Polarization-gradient cooling in a strong doughnut-mode dipole potential

S. J. M. Kuppens, M. Rauner, M. Schiffer, K. Sengstock, W. Ertmer, F. E. van Dorsselaer, Gerard Nienhuis

Published Oct 1, 1998• 54 citations
Publisher

Abstract

We present experimental and theoretical studies of polarization-gradient cooling of metastable neon atoms confined to the dark center of a ${\mathrm{TEM}}_{01}^{*}$ (doughnut) mode. A slow beam of neon atoms is guided and focused inside a blue-detuned and focused doughnut-mode laser beam to a spot size below 10 \ensuremath{\mu}m. The transverse motion inside this doughnut mode is cooled by means of two-dimensional optical molasses. We observed non-Gaussian two-component velocity distributions of which the cold component has a width of down to three recoil velocities. These results are found to be in qualitative agreement with a quantum Monte Carlo simulation of cooling in one dimension in the presence of an external light-shift potential. For the simulation we apply the recently developed technique of quantum-state diffusion with adaptive noise.

DOI
10.1103/physreva.58.3068

Related papers

Many-particle effects in laser cooling of one-dimensional optical molasses

K. Ellinger, J. Cooper

We analyze the influence of long-range dipole-dipole interactions between atoms with Zeeman substructure on atomic polarization-gradient cooling at low laser power. The system we consider is a cloud of N atoms driven by two counterpropagating linear cross-polarized laser beams (lin\ensuremath{\perp}lin configuration) on a -- transition. In the semiclassical regime we derive analytical results for the change of the cooling force due to collisions and for the diffusion coefficient in the far-field approximation. For the energy regime where the center-of-mass motion is characterized by oscillations in the optical potentials, we estimate the effect of these far-field collisions on the motion-induced sideband structure of the resonance fluorescence spectrum by using a white-noise approximation for the background light field. This gives a qualitative signature of the heating mechanism in such systems.

Physical Review A•Jun 1, 1997•6 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.

Quantum Electronics and Laser Science Conference•Nov 13, 2002•0 citations

Numerical experiments in semiclassical laser-cooling theory of multistate atoms

Juha Javanainen

We describe a numerical implementation of our semiclassical laser-cooling theory [J. Javanainen, Phys. Rev. A 44, 5857 (1991)] for an arbitrary multilevel atom and light field. There is satisfactory agreement between experiments and temperatures obtained from Langevin-equation simulations of the motion of an atom subject to light-pressure force and the accompanying diffusion in three-dimensional (3D) optical molasses in which there are three orthogonal pairs of counterpropagating waves with a common linear polarization for the two beams in a pair, but orthogonal polarizations between the pairs. However, the velocity distribution of the atoms is anisotropic and may deviate strongly from a Gaussian, heterodyne spectra may have a sideband, and the atomic density may be a maximum at the maximum of the potential of the dipole forces of the molasses beams. Subsequent velocity-linearized analysis of atomic damping and diffusion shows that the damping tensor may have a negative eigenvalue corresponding to heating in large regions of space, even though the light is red tuned for cooling. It is also found that the position-averaged damping and diffusion tensors make a poor predictor of the temperature obtained in Langevin-equation simulations and real experiments. Based on additional simulations of a simple 1D model, we formulate a hypothesis that connects our findings. The key idea is that an atom trapped in a minimum of the potential of the dipole forces is subject to a weaker-than-average damping, and therefore tends to boil out of the trap.

Physical Review A•Nov 1, 1992•54 citations

Doughnut-beam-induced Sisyphus cooling in atomic guiding and collimation

Jianping Yin, Yifu Zhu

We propose a simple atomic-beam collimator consisting of a blue-detuned cylindrical-hollow (doughnut) laser beam. Cold atoms from a magneto-optical trap are loaded into the doughnut beam and guided in the propagation direction of the doughnut beam. The cold atoms experience efficient Sisyphus cooling induced by the doughnut beam and a weak repumping beam and are collimated in the transverse direction. In the longitudinal direction the cold atoms experience small accelerations that are due to the absorption-induced heating of the doughnut beam and the repumping beam. The cooling, heating, and loss mechanisms in this atomic collimator are analyzed. Our study shows that an intense cold atomic beam with a minimum transverse velocity of ∼2 cm s-1 (a minimum transverse temperature of ∼1.4 μK) and a brightness of approximately 2×1013 atoms (sr-1 cm-2 s-1) can be obtained from the collimator.

Journal of the Optical Society of America B•Aug 1, 1998•11 citations

Quantum motion of laser trapped atoms

Poul Jessen

In two recent experiments Verkerk et al. and our group have observed quantization of the center-of-mass motion of laser cooled atoms in sub-wavelength sized potential wells formed by the light field of a 1-dimensional optical molasses. Our 1-dimensional optical molasses consists of a pair of counterpropagating laser beams of orthogonal, linear polarization, creating a series of potential wells separated by {lambda}/4. Polarization gradient laser cooling reduces the thermal energy of the atoms until they are trapped in well resolved vibrational levels near the bottom of the wells. Transitions between these vibrational levels are seen in a high resolution spectrum of fluorescence, where they give rise to a Rayleigh peak centered at the laser frequency, and well resolved Raman sidebands shifted by a frequency {plus_minus}{omega}, typically on the order of 100 kHz. We find quantitative agreement between the measured level separation h{omega} and the results of a calculation of the bandstructure in the periodic optical potential. Based on the observed ratio of the strength of the blue to the red sideband we determine the temperature of the atoms, and find agreement with theoretical predictions. Based on the level spacing and temperature we find the atoms to be localized to {approx}/15, withmore » up to 50-60% of the population of the trapped atoms in the vibrational ground state. We observe intriguing differences between fluorescence radiated by localized atoms, and the fluorescence radiated by non-localized atoms in a 1-dimensional optical molasses composed of a pair of counterpropagating laser beams of opposite circular polarization. The prospect of observing quantum motion and spatial order in 2 and 3 dimensions, and the consequences for the spectrum of fluorescence, will be discussed.« less

Bulletin of the American Physical Society•May 1, 1993•0 citations

Laser cooling below the Doppler limit by polarization gradients: simple theoretical models

Jean Dalibard, Claude N. Cohen-Tannoudji

We present two cooling mechanisms that lead to temperatures well below the Doppler limit. These mechanisms are based on laser polarization gradients and work at low laser power when the optical-pumping time between different ground-state sublevels becomes long. There is then a large time lag between the internal atomic response and the atomic motion, which leads to a large cooling force. In the simple case of one-dimensional molasses, we identify two types of polarization gradient that occur when the two counterpropagating waves have either orthogonal linear polarizations or orthogonal circular polarizations. In the first case, the light shifts of the ground-state Zeeman sublevels are spatially modulated, and optical pumping among them leads to dipole forces and to a Sisyphus effect analogous to the one that occurs in stimulated molasses. In the second case (σ+−σ− configuration), the cooling mechanism is radically different. Even at very low velocity, atomic motion produces a population difference among ground-state sublevels, which gives rise to unbalanced radiation pressures. From semiclassical optical Bloch equations, we derive for the two cases quantitative expressions for friction coefficients and velocity capture ranges. The friction coefficients are shown in both cases to be independent of the laser power, which produces an equilibrium temperature proportional to the laser power. The lowest achievable temperatures then approach the one-photon recoil energy. We briefly outline a full quantum treatment of such a limit.

Journal of the Optical Society of America B•Nov 1, 1989•1,272 citations
We present experimental and theoretical studies of polarization-gradient cooling of metastable neon atoms confined to the dark center of a TEM01∗{\mathrm{TEM}}_{01}^{*}TEM01∗​ (doughnut) mode. A slow beam of neon atoms is guided and focused inside a blue-detuned and focused doughnut-mode laser beam to a spot size below 10 \ensuremath{\mu}m. The transverse motion inside this doughnut mode is cooled by means of two-dimensional optical molasses. We observed non-Gaussian two-component velocity distributions of which the cold component has a width of down to three recoil velocities. These results are found to be in qualitative agreement with a quantum Monte Carlo simulation of cooling in one dimension in the presence of an external light-shift potential. For the simulation we apply the recently developed technique of quantum-state diffusion with adaptive noise.
We analyze the influence of long-range dipole-dipole interactions between atoms with Zeeman substructure on atomic polarization-gradient cooling at low laser power. The system we consider is a cloud of N atoms driven by two counterpropagating linear cross-polarized laser beams (lin\ensuremath{\perp}lin configuration) on a -- transition. In the semiclassical regime we derive analytical results for the change of the cooling force due to collisions and for the diffusion coefficient in the far-field approximation. For the energy regime where the center-of-mass motion is characterized by oscillations in the optical potentials, we estimate the effect of these far-field collisions on the motion-induced sideband structure of the resonance fluorescence spectrum by using a white-noise approximation for the background light field. This gives a qualitative signature of the heating mechanism in such systems.
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.
We describe a numerical implementation of our semiclassical laser-cooling theory [J. Javanainen, Phys. Rev. A 44, 5857 (1991)] for an arbitrary multilevel atom and light field. There is satisfactory agreement between experiments and temperatures obtained from Langevin-equation simulations of the motion of an atom subject to light-pressure force and the accompanying diffusion in three-dimensional (3D) optical molasses in which there are three orthogonal pairs of counterpropagating waves with a common linear polarization for the two beams in a pair, but orthogonal polarizations between the pairs. However, the velocity distribution of the atoms is anisotropic and may deviate strongly from a Gaussian, heterodyne spectra may have a sideband, and the atomic density may be a maximum at the maximum of the potential of the dipole forces of the molasses beams. Subsequent velocity-linearized analysis of atomic damping and diffusion shows that the damping tensor may have a negative eigenvalue corresponding to heating in large regions of space, even though the light is red tuned for cooling. It is also found that the position-averaged damping and diffusion tensors make a poor predictor of the temperature obtained in Langevin-equation simulations and real experiments. Based on additional simulations of a simple 1D model, we formulate a hypothesis that connects our findings. The key idea is that an atom trapped in a minimum of the potential of the dipole forces is subject to a weaker-than-average damping, and therefore tends to boil out of the trap.
We propose a simple atomic-beam collimator consisting of a blue-detuned cylindrical-hollow (doughnut) laser beam. Cold atoms from a magneto-optical trap are loaded into the doughnut beam and guided in the propagation direction of the doughnut beam. The cold atoms experience efficient Sisyphus cooling induced by the doughnut beam and a weak repumping beam and are collimated in the transverse direction. In the longitudinal direction the cold atoms experience small accelerations that are due to the absorption-induced heating of the doughnut beam and the repumping beam. The cooling, heating, and loss mechanisms in this atomic collimator are analyzed. Our study shows that an intense cold atomic beam with a minimum transverse velocity of ∼2 cm s-1 (a minimum transverse temperature of ∼1.4 μK) and a brightness of approximately 2×1013 atoms (sr-1 cm-2 s-1) can be obtained from the collimator.
In two recent experiments Verkerk et al. and our group have observed quantization of the center-of-mass motion of laser cooled atoms in sub-wavelength sized potential wells formed by the light field of a 1-dimensional optical molasses. Our 1-dimensional optical molasses consists of a pair of counterpropagating laser beams of orthogonal, linear polarization, creating a series of potential wells separated by {lambda}/4. Polarization gradient laser cooling reduces the thermal energy of the atoms until they are trapped in well resolved vibrational levels near the bottom of the wells. Transitions between these vibrational levels are seen in a high resolution spectrum of fluorescence, where they give rise to a Rayleigh peak centered at the laser frequency, and well resolved Raman sidebands shifted by a frequency {plus_minus}{omega}, typically on the order of 100 kHz. We find quantitative agreement between the measured level separation h{omega} and the results of a calculation of the bandstructure in the periodic optical potential. Based on the observed ratio of the strength of the blue to the red sideband we determine the temperature of the atoms, and find agreement with theoretical predictions. Based on the level spacing and temperature we find the atoms to be localized to {approx}/15, withmore » up to 50-60% of the population of the trapped atoms in the vibrational ground state. We observe intriguing differences between fluorescence radiated by localized atoms, and the fluorescence radiated by non-localized atoms in a 1-dimensional optical molasses composed of a pair of counterpropagating laser beams of opposite circular polarization. The prospect of observing quantum motion and spatial order in 2 and 3 dimensions, and the consequences for the spectrum of fluorescence, will be discussed.« less
We present two cooling mechanisms that lead to temperatures well below the Doppler limit. These mechanisms are based on laser polarization gradients and work at low laser power when the optical-pumping time between different ground-state sublevels becomes long. There is then a large time lag between the internal atomic response and the atomic motion, which leads to a large cooling force. In the simple case of one-dimensional molasses, we identify two types of polarization gradient that occur when the two counterpropagating waves have either orthogonal linear polarizations or orthogonal circular polarizations. In the first case, the light shifts of the ground-state Zeeman sublevels are spatially modulated, and optical pumping among them leads to dipole forces and to a Sisyphus effect analogous to the one that occurs in stimulated molasses. In the second case (σ+−σ− configuration), the cooling mechanism is radically different. Even at very low velocity, atomic motion produces a population difference among ground-state sublevels, which gives rise to unbalanced radiation pressures. From semiclassical optical Bloch equations, we derive for the two cases quantitative expressions for friction coefficients and velocity capture ranges. The friction coefficients are shown in both cases to be independent of the laser power, which produces an equilibrium temperature proportional to the laser power. The lowest achievable temperatures then approach the one-photon recoil energy. We briefly outline a full quantum treatment of such a limit.