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

arXiv:1511.08527 · Physical Review A

Propagation of light through small clouds of cold interacting atoms

Stephan Jennewein, Yvan R. P. Sortais, Jean‐Jacques Greffet, Antoine Browaeys

Published Nov 15, 2016• 37 citations
arXivHTMLPDF

Abstract

We demonstrate experimentally that a dense cloud of cold atoms with a size comparable to the wavelength of light can induce large group delays on a laser pulse when the laser is tightly focused on it and is close to an atomic resonance. Delays as large as $\ensuremath{-}10\phantom{\rule{0.28em}{0ex}}\mathrm{ns}$ are observed, corresponding to ``superluminal'' propagation with negative group velocities as low as $\ensuremath{-}300\phantom{\rule{0.28em}{0ex}}\mathrm{m}/\mathrm{s}$. Strikingly, this large delay is associated with a moderate extinction owing to the very small size of the dense cloud. It implies that a large phase shift is imprinted on the continuous laser beam. Our system may thus be useful for applications to quantum technologies, such as variable delay line for individual photons or phase imprint between two beams at the single-photon level.

DOI
10.1103/physreva.94.053828

Related papers

Coherent Scattering of Near-Resonant Light by a Dense Microscopic Cold Atomic Cloud

Stephan Jennewein, Mondher Besbes, Nick J. Schilder +6 more

We measure the coherent scattering of light by a cloud of laser-cooled atoms with a size comparable to the wavelength of light. By interfering a laser beam tuned near an atomic resonance with the field scattered by the atoms, we observe a resonance with a redshift, a broadening, and a saturation of the extinction for increasing atom numbers. We attribute these features to enhanced light-induced dipole-dipole interactions in a cold, dense atomic ensemble that result in a failure of standard predictions such as the "cooperative Lamb shift". The description of the atomic cloud by a mean-field model based on the Lorentz-Lorenz formula that ignores scattering events where light is scattered recurrently by the same atom and by a microscopic discrete dipole model that incorporates these effects lead to progressively closer agreement with the observations, despite remaining differences.

arXiv:1510.08041•Physical Review Letters•Jun 8, 2016•131 citations

Large negative and positive delay of optical pulses in coherently prepared dense Rb vapor with buffer gas

Eugeniy E. Mikhailov, Vladimir A. Sautenkov, Irina V. Novikova +1 more

We experimentally study the group time delay for a light pulse propagating through hot $^{87}\mathrm{Rb}$ vapor in the presence of a strong coupling field in a $\ensuremath{\Lambda}$ configuration. We demonstrate that the ultraslow pulse propagation is transformed into superluminal propagation as the one-photon detuning of the light increases due to the change in the transmission resonance line shape. Negative group velocity as low as $\ensuremath{-}c∕{10}^{6}=\ensuremath{-}80\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s}$ is recorded. We also find that the advance time in the regime of the superluminal propagation grows linearly with increasing laser field power.

arXiv:quant-ph/0402120•Physical Review A•Jun 14, 2004•66 citations

Superluminal and slow light propagation in cold atoms

Hoonsoo Kang, Gessler Hernandez, Yifu Zhu

The group velocity of a light pulse propagating through a four-level system exhibiting electromagnetically induced transparency can be manipulated by a pump laser. The pump laser induces the large optical nonlinearities with steep normal or anomalous dispersion. We present experimental measurements that demonstrate both slow and superluminal light propagation in cold Rb atoms.

Physical Review A•Jul 7, 2004•76 citations

Parametric phase shift in electromagnetically induced transparencies

M. Muller, R.-H. Rinkleff, K. Danzmann

Summary form only given. The field of atom manipulation using laser light has experienced a rapid growth in the recent years. By the interaction of the atoms with laser light it is possible to design media with desired optical properties such as transparent media showing negative or positive dispersion. Negative dispersive transparent media can be used e.g. to realize an optical cavity with large build up but broadband response (white light cavity) or to demonstrate superluminal light propagation. It has also been demonstrated that positive dispersive media can exhibit steep dispersion leading to small absolute values of the group velocity (slow light, see e.g.) or reducing e.g. the line width of a cavity relative to the line width of the empty resonator.We report on recent experiments on investigation the absorptive and dispersive properties of a coherent prepared media, that shows electromagnetically induced transparency on extremely narrow dark resonances. We have carried out the experimental study of a two-photon excitation via quantum interference in a three level Cs atomic system. The experiments were done on a Cs atomic beam.

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

Super- and subradiance in a dilute cloud of cold atoms

M. Araujo

The problem of the interaction of N atoms with a laser beam and vacuum modes can give rise to many interesting phenomena concerning the spontaneous emission of light and its propagation in the medium. The cooperative effects, for example, such as superadiance and subradiance, are effects related to the coherence created between the atoms when a photon is emitted spontaneously by a single excited atom. Superradiance can be defined as the enhancement of the spontaneous emission due to constructive interference of the scattered light. Its counterpart, subradiance, is the trapping of some remaining light due to destructive interference. In cold atoms, some previous theoretical works predict and characterize these two cooperative effects in a large and diluted atomic cloud, in the regime of low intensities and large detunings of the incident laser. The theoretical model is a coupled-dipole model for two-level atoms driven by a low-intensity field and in the scalar approach. The experiment consists in measuring the super- and subradiant decay rates from the temporal emitted intensity after the switch off of the incident laser in the steady state. Our experimental setup consists in a magneto-optical trap of rubidium 87 atoms at large resonant optical thicknesses. A probe beam excites the atoms close to the D2 line. The intensity emitted is detected by a single photon detector with no afterpulsing and a calibration procedure allows us to determine the resonant optical thickness of the cloud and its temperature. In this work, we report the experimental observation of super- and subradiance in a large cloud of cold atoms. For subradiance, the main result is the linear evolution of the characteristic time with the resonant optical thickness of the cloud and its independence of the detuning. For superradiance, we observe superradiance out of the forward direction. We verify the validity of our interpretations with the predictions of the coupled-dipole model. Finally, we discuss the interplay of subradiance and radiation trapping, as well as theoretical predictions for: a setup of a phased cloud, to control the subradiant amplitude emission; and temperature effects, where subradiance is shown to be robust in a large range of temperatures.

•Dec 11, 2018•0 citations

Collective resonance fluorescence in small and dense atom clouds: Comparison between theory and experiment

S. D. Jenkins, Janne Ruostekoski, Juha Javanainen +5 more

We study the emergence of a collective optical response of a cold and dense $^{87}\mathrm{Rb}$ atomic cloud to a near-resonant low-intensity light when the atom number is gradually increased. Experimental observations are compared with microscopic stochastic simulations of recurrent scattering processes between the atoms that incorporate the atomic multilevel structure and the optical measurement setup. We analyze the optical response of an inhomogeneously broadened gas and find that the experimental observations of the resonance line shifts and the total collected scattered light intensity in cold atom clouds substantially deviate from those of thermal atomic ensembles, indicating strong light-induced resonant dipole-dipole interactions between the atoms. At high densities, the simulations also predict a significantly slower decay of light-induced excitations in cold than in thermal atom clouds. The role of dipole-dipole interactions is discussed in terms of resonant coupling examples and the collective radiative excitation eigenmodes of the system.

arXiv:1606.02757•Physical Review A•Aug 24, 2016•86 citations
We demonstrate experimentally that a dense cloud of cold atoms with a size comparable to the wavelength of light can induce large group delays on a laser pulse when the laser is tightly focused on it and is close to an atomic resonance. Delays as large as \ensuremath−10ns\ensuremath{-}10\phantom{\rule{0.28em}{0ex}}\mathrm{ns}\ensuremath−10ns are observed, corresponding to ``superluminal'' propagation with negative group velocities as low as \ensuremath−300m/s\ensuremath{-}300\phantom{\rule{0.28em}{0ex}}\mathrm{m}/\mathrm{s}\ensuremath−300m/s. Strikingly, this large delay is associated with a moderate extinction owing to the very small size of the dense cloud. It implies that a large phase shift is imprinted on the continuous laser beam. Our system may thus be useful for applications to quantum technologies, such as variable delay line for individual photons or phase imprint between two beams at the single-photon level.
We measure the coherent scattering of light by a cloud of laser-cooled atoms with a size comparable to the wavelength of light. By interfering a laser beam tuned near an atomic resonance with the field scattered by the atoms, we observe a resonance with a redshift, a broadening, and a saturation of the extinction for increasing atom numbers. We attribute these features to enhanced light-induced dipole-dipole interactions in a cold, dense atomic ensemble that result in a failure of standard predictions such as the "cooperative Lamb shift". The description of the atomic cloud by a mean-field model based on the Lorentz-Lorenz formula that ignores scattering events where light is scattered recurrently by the same atom and by a microscopic discrete dipole model that incorporates these effects lead to progressively closer agreement with the observations, despite remaining differences.
We experimentally study the group time delay for a light pulse propagating through hot 87Rb^{87}\mathrm{Rb}87Rb vapor in the presence of a strong coupling field in a $\ensuremath{\Lambda}$ configuration. We demonstrate that the ultraslow pulse propagation is transformed into superluminal propagation as the one-photon detuning of the light increases due to the change in the transmission resonance line shape. Negative group velocity as low as $\ensuremath{-}c∕{10}^{6}=\ensuremath{-}80\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s}$ is recorded. We also find that the advance time in the regime of the superluminal propagation grows linearly with increasing laser field power.
Summary form only given. The field of atom manipulation using laser light has experienced a rapid growth in the recent years. By the interaction of the atoms with laser light it is possible to design media with desired optical properties such as transparent media showing negative or positive dispersion. Negative dispersive transparent media can be used e.g. to realize an optical cavity with large build up but broadband response (white light cavity) or to demonstrate superluminal light propagation. It has also been demonstrated that positive dispersive media can exhibit steep dispersion leading to small absolute values of the group velocity (slow light, see e.g.) or reducing e.g. the line width of a cavity relative to the line width of the empty resonator.We report on recent experiments on investigation the absorptive and dispersive properties of a coherent prepared media, that shows electromagnetically induced transparency on extremely narrow dark resonances. We have carried out the experimental study of a two-photon excitation via quantum interference in a three level Cs atomic system. The experiments were done on a Cs atomic beam.
The problem of the interaction of N atoms with a laser beam and vacuum modes can give rise to many interesting phenomena concerning the spontaneous emission of light and its propagation in the medium. The cooperative effects, for example, such as superadiance and subradiance, are effects related to the coherence created between the atoms when a photon is emitted spontaneously by a single excited atom. Superradiance can be defined as the enhancement of the spontaneous emission due to constructive interference of the scattered light. Its counterpart, subradiance, is the trapping of some remaining light due to destructive interference. In cold atoms, some previous theoretical works predict and characterize these two cooperative effects in a large and diluted atomic cloud, in the regime of low intensities and large detunings of the incident laser. The theoretical model is a coupled-dipole model for two-level atoms driven by a low-intensity field and in the scalar approach. The experiment consists in measuring the super- and subradiant decay rates from the temporal emitted intensity after the switch off of the incident laser in the steady state. Our experimental setup consists in a magneto-optical trap of rubidium 87 atoms at large resonant optical thicknesses. A probe beam excites the atoms close to the D2 line. The intensity emitted is detected by a single photon detector with no afterpulsing and a calibration procedure allows us to determine the resonant optical thickness of the cloud and its temperature. In this work, we report the experimental observation of super- and subradiance in a large cloud of cold atoms. For subradiance, the main result is the linear evolution of the characteristic time with the resonant optical thickness of the cloud and its independence of the detuning. For superradiance, we observe superradiance out of the forward direction. We verify the validity of our interpretations with the predictions of the coupled-dipole model. Finally, we discuss the interplay of subradiance and radiation trapping, as well as theoretical predictions for: a setup of a phased cloud, to control the subradiant amplitude emission; and temperature effects, where subradiance is shown to be robust in a large range of temperatures.
We study the emergence of a collective optical response of a cold and dense 87Rb^{87}\mathrm{Rb}87Rb atomic cloud to a near-resonant low-intensity light when the atom number is gradually increased. Experimental observations are compared with microscopic stochastic simulations of recurrent scattering processes between the atoms that incorporate the atomic multilevel structure and the optical measurement setup. We analyze the optical response of an inhomogeneously broadened gas and find that the experimental observations of the resonance line shifts and the total collected scattered light intensity in cold atom clouds substantially deviate from those of thermal atomic ensembles, indicating strong light-induced resonant dipole-dipole interactions between the atoms. At high densities, the simulations also predict a significantly slower decay of light-induced excitations in cold than in thermal atom clouds. The role of dipole-dipole interactions is discussed in terms of resonant coupling examples and the collective radiative excitation eigenmodes of the system.