140 research outputs found
Coherent backscattering of light by atoms in the saturated regime
We present the first calculation of coherent backscattering with inelastic
scattering by saturated atoms. We consider the scattering of a
quasi-monochromatic laser pulse by two distant atoms in free space. By
restricting ourselves to scattering of two photons, we employ a perturbative
approach, valid up to second order in the incident laser intensity. The
backscattering enhancement factor is found to be smaller than two (after
excluding single scattering), indicating a loss of coherence between the doubly
scattered light emitted by both atoms. Since the undetected photon carries
information about the path of the detected photon, the coherence loss can be
explained by a which-path argument, in analogy with a double-slit experiment.Comment: 16 pages, 10 figure
Saturation induced coherence loss in coherent backscattering of light
We use coherent backscattering (CBS) of light by cold Strontium atoms to
study the mutual coherence of light waves in the multiple scattering regime. As
the probe light intensity is increased, the atomic optical transition starts to
be saturated. Nonlinearities and inelastic scattering then occur. In our
experiment, we observe a strongly reduced enhancement factor of the coherent
backscattering cone when the intensity of the probe laser is increased,
indicating a partial loss of coherence in multiple scattering
Transport Mean Free Path for Magneto-Transverse Light Diffusion
We derive an expression for the transport mean free path
associated with magneto-transverse light diffusion for a random collection of
Faraday-active
Mie scatterers. This expression relates the magneto-transverse diffusion in
multiple scattering directly to the magneto-transverse scattering of a single
scatterer.Comment: 5 pages, 1 figure, Latex, accepted for publication in Europhysics
Letter
Observation of coherent backscattering of light by cold atoms
Coherent backscattering (CBS) of light waves by a random medium is a
signature of interference effects in multiple scattering. This effect has been
studied in many systems ranging from white paint to biological tissues.
Recently, we have observed CBS from a sample of laser-cooled atoms, a
scattering medium with interesting new properties. In this paper we discuss
various effects, which have to be taken into account for a quantitative study
of coherent backscattering of light by cold atoms.Comment: 25 pages LaTex2e, 17 figures, submitted to J. Opt. B: Quant. Semicl.
Op
Corrections to the Boltzmann mean free path in disordered systems with finite size scatterers
The mean free path is an essential characteristic length in disordered
systems. In microscopic calculations, it is usually approximated by the
classical value of the elastic mean free path. It corresponds to the Boltzmann
mean free path when only isotropic scattering is considered, but it is
different for anisotropic scattering. In this paper, we work out the
corrections to the so called Boltzmann mean free path due to multiple
scattering effects on finite size scatterers, in the s-wave approximation, ie.
when the elastic mean free path is equivalent to the Boltzmann mean free path.
The main result is the expression for the mean free path expanded in powers of
the perturbative parameter given by the scatterer density.Comment: 12 page
Coherent Backscattering of light in a magnetic field
This paper describes how coherent backscattering is altered by an external
magnetic field. In the theory presented, magneto-optical effects occur inside
Mie scatterers embedded in a non-magnetic medium. Unlike previous theories
based on point-like scatterers, the decrease of coherent backscattering is
obtained in leading order of the magnetic field using rigorous Mie theory. This
decrease is strongly enhanced in the proximity of resonances, which cause the
path length of the wave inside a scatterer to be increased. Also presented is a
novel analysis of the shape of the backscattering cone in a magnetic field.Comment: 27 pages, 5 figures, Revtex, to appear in Phys. Rev.
Green function Retrieval and Time-reversal in a Disordered World
We apply the theory of multiple wave scattering to two contemporary, related
topics: imaging with diffuse correlations and stability of time-reversal of
diffuse waves, using equipartition, coherent backscattering and frequency
speckles as fundamental concepts.Comment: 1 figur
Transverse Momentum Transfer in Atom-Light Scattering
We predict a photon Hall effect in the optical cross-section of atomic
hydrogen, which is caused by the interference between an electric quadrupole
transition and an electric dipole transition from the ground state to
and . This induces a magneto-transverse acceleration
comparable to a fraction of . In atoms with a two level electric dipole
transition, a much smaller transverse force is generated only when the atom is
moving
Coherent Backscattering of Light by Cold Atoms
Light propagating in an optically thick sample experiences multiple
scattering. It is now known that interferences alter this propagation, leading
to an enhanced backscattering, a manifestation of weak localization of light in
such diffuse samples. This phenomenon has been extensively studied with
classical scatterers. In this letter we report the first experimental evidence
for coherent backscattering of light in a laser-cooled gas of Rubidium atoms.Comment: 4 pages REVTEX, 1 page color image GIF, accepted for publication in
Phys. Rev. Let
Mesoscopic scattering of spin s particles
Quantum effects in weakly disordered systems are governed by the properties
of the elementary interaction between propagating particles and impurities.
Long range mesoscopic effects due to multiple scattering are derived by
iterating the single scattering vertex, which has to be appropriately
diagonalized. In the present contribution, we present a systematic and detailed
diagonalisation of the diffuson and cooperon vertices responsible for weak
localisation effects. We obtain general expressions for eigenvalues and
projectors onto eigenmodes, for any spin and arbitrary elementary interaction
with impurities. This description provides a common frame for a unified theory
of mesoscopic spin physics for electrons, photons, and other quantum particles.
We treat in detail the case of spin-flip scattering of electrons by freely
orientable magnetic impurities and briefly review the case of photon scattering
from degenerate dipole transitions in cold atomic gases.Comment: published version, with a new figure and new section
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