Cold Atoms


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  • 09/01: Welcome to our new PhD students: Ana Cipris, Marius Gaudesius and Florent Cottier.




Publications of the team





Research activities:


Wave propagation in diffusive media is an important subject for numerous fields (medical imaging, acoustics, seismology, stellar physics, …). The experiments that we pursue at INLN make use of an original medium: a cold-atom cloud. The peculiar properties of this diffusive medium (strong resonances, quantum internal structure of the scatterers, mechanical effects of light on the atoms, quantum effects…) give rise to a very rich physics. We study several subjects in this context. Our work is mainly experimental, using three cold-atom apparatus and several smaller hot-vapor setups, but also theoretical, in particular through many collaborations. We have also started some intrumental work in collaboration with astrophysicists.


Cooperative scattering

When a photon is sent onto an atomic ensemble, it interacts collectively with the N atoms of the cloud and not simply with one of them. This results in measurable modifications in the scattering rate, the emission diagram or the temporal dynamics. We study these cooperative effects experimentally and theoretically.
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Nonlinear optics

Atomic vapors have strong optical nonlinearities that we use in experiments with hot or cold vapors. In the latter case, the mechanical aspect plays also a role, with the spontaneous formation of atomic-density patterns.
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Fluctuations and correlations of light: from atoms to stars

We study the fluctuations and correlations of light after interaction with cold or hot atomic vapors, either after transmission through the atoms, or after scattering by the atoms, in the single and multiple scattering regimes. We also collaborate with astrophysicists of the Observatoire de la Côte d'Azur to work towards the revival of intensity interferometry (Hanbury Brown and Twiss technique) with modern photonic technologies.
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Random laser with cold atoms

A random laser is a laser without optical cavity, in which the feedback effect is provided by multiple scattering inside the gain medium. This kind of laser has been known for a few years and is currently an important topic in the photonics community. We have recently observed such a random-laser effect in a cold-atom cloud, in which we managed to combine gain and multiple scattering. We now want to study the properties of this random laser more precisely.
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When a wave propagates in a strongly disordered medium, it is predicted that above a certain level of disorder, interference effects completely block the wave diffusion. This so-called Anerderson localization has never been clealy observed for light. We study, at a theoretical level so far, if and how a cold atom cloud could be an appropriate medium for observing this effect.
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Light-induced long-range force

We also study the mechanical action of light on cold atoms during the multiple-scattering process. For example, it can give rise to mechanical instabilities, which we studied experimentally and theoretically. Moreover, it gives a force that is long-range, like Coulombian and gravitational interactions. As a consequence, there are interesting analogies with plasma physics and gravitational systems.
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Lévy flights in hot vapors

In hot vapors, Doppler effect induces a frequency redistribution, which changes the transport properties of light. We have experimentally evidenced that light makes “Lévy flights”, i.e., very long steps that dominate the system dynamics, which becomes superdiffusive. In relation to astrophysical problems, we also study the polarization of multiply-scattered light.
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Former projects

  • Radiative transport of light in cold atoms
  • Coherent backscattering of light by cold atoms
  • Laser cooling of strontium