© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

PHYSICS & ASTRONOMY COLLOQUIUM UNIVERSITY OF WISCONSIN - STEVENS POINT

P. Kulatunga

Published Jan 1, 2012• 0 citations

Abstract

Weak localization of light or coherent backscattering (CBS) of light is a phenomena in which partial waves traversing momentum-reversed (time-reversed) scattering paths interfere constructively in the backscattering direction leading to an enhancement of scattered light intensity. The enhancement of intensity is proportional to a reduction of light transported in the scattering medium. Thus the CBS signal is a measure of localization of light in the scattering medium. We are building an apparatus to observe weak localization of photons in a high density sample of ultra-cold atoms. First we slow the atoms from room temperature (300 m/s) to less than 10 cm/s in a magneto-optical trap (MOT) where the atom number density is 10 11 atoms/cm 3 . In order to increase the atomic density the atoms in the MOT are transferred to a far detuned microscopic dipole trap created by a laser focused to a waist of approximately 5m. We have successfully loaded the MOT and are now in the process of loading the high density microscopic dipole trap. Once this is achieved we will look at the CBS signal as a function of the atom number density and the scattering cross section. The goal of the project is to reach the Joffe-Regel region where mean free path length is about the wavelength of the scattering radiation.

Related papers

Probing the mesoscopic coherence length of light in cold atoms

G. Labeyrie, David Wilkowski, Robin Kaiser +4 more

We employed the so-called coherent backscattering effect (CBS) to study the coherence length of light in a cloud of cold atoms obtained from a magneto-optical trap. The CBS signal is due to the constructive interference between waves following the same multiple scattering path in reverse order.

European Quantum Electronics Conference (EQEC)•Jan 18, 2006•0 citations

Coherent backscattering of light by cold atoms

Christian Miniatura, G. Labeyrie, Cord Axel Müller +2 more

Summary form only given. A wave propagating in a strongly scattering medium experiences many scattering events which rapidly erase the memory of its initial direction on a typical scale length known as the transport mean free path. It is now known that interference can profoundly alter the wave transport, a spectacular manifestation being weak and strong localisation of waves. We shall briefly review the basics of coherent backscattering (CBS) and the results obtained with classical scatterers. We shall then describe our experiment using cold atoms and discuss the experimental data. The non trivial role of the atomic quantum internal structure in the enhancement reduction will be singled out in a simple situation and results of analytical calculations will be presented.

Conference on Lasers and Electro-Optics•Aug 29, 2005•2 citations

Weak localization of light by cold atoms: The impact of quantum internal structure

Cord Axel Müller, Thibaut Jonckheere, Christian Miniatura +1 more

Since the work of Anderson on localization, interference effects for the propagation of a wave in the presence of disorder have been extensively studied, as exemplified in coherent backscattering (CBS) of light. In the multiple scattering of light by a disordered sample of thermal atoms, interference effects are usually washed out by the fast atomic motion. This is no longer true for cold atoms where CBS has recently been observed. However, the internal structure of the atoms strongly influences the interference properties. In this paper, we consider light scattering by an atomic dipole transition with arbitrary degeneracy and study its impact on coherent backscattering. We show that the interference contrast is strongly reduced. Assuming a uniform statistical distribution over internal degrees of freedom, we compute analytically the single- and double-scattering contributions to the intensity in the weak-localization regime. The so-called ladder and crossed diagrams are generalized to the case of atoms and permit to calculate enhancement factors and backscattering intensity profiles for polarized light and any closed atomic dipole transition.

arXiv:quant-ph/0107030•Physical Review A•Oct 2, 2001•62 citations

Observation of coherent backscattering of light by cold atoms

G. Labeyrie, Cord Axel Müller, D S Wiersma +2 more

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.

arXiv:cond-mat/0004359•Journal of Optics B Quantum and Semiclassical Optics•Oct 1, 2000•54 citations

Coherent Backscattering of Ultracold Atoms

Fred Jendrzejewski, Kilian Müller, Jérémie Richard +5 more

We report on the direct observation of coherent backscattering (CBS) of ultracold atoms in a quasi-two-dimensional configuration. Launching atoms with a well-defined momentum in a laser speckle disordered potential, we follow the progressive build up of the momentum scattering pattern, consisting of a ring associated with multiple elastic scattering, and the CBS peak in the backward direction. Monitoring the depletion of the initial momentum component and the formation of the angular ring profile allows us to determine microscopic transport quantities. We also study the time evolution of the CBS peak and find it in fair agreement with predictions, at long times as well as at short times. The observation of CBS can be considered a direct signature of coherence in quantum transport of particles in disordered media. It is responsible for the so called weak localization phenomenon, which is the precursor of Anderson localization.

arXiv:1207.4775•Physical Review Letters•Nov 5, 2012•117 citations

Weak localization of photon noise

Paolo Scalia, Otto L. Muskens, Ad Lagendijk

We present an experimental study of coherent backscattering (CBS) of photon noise from multiple scattering media. We use a pseudothermal light source with a microsecond coherence time to produce a noise spectrum covering a continuous transition, from wave fluctuations to shot noise over several MHz. The angle-dependent Fano factor of backscattered light shows an enhancement due to CBS in the wave fluctuation regime. The CBS line shape and enhancement factor of the noise power is consistent with theory in the weak-scattering limit and for a large number of open reflection channels. These initial experiments on weakly scattering media demonstrate that sensitive noise measurements can be combined with the separation of path lengths present in CBS, opening up new experiments on noise transport in the localization regime.

New Journal of Physics•Oct 8, 2013•4 citations

Weak localization of light or coherent backscattering (CBS) of light is a phenomena in which partial waves traversing momentum-reversed (time-reversed) scattering paths interfere constructively in the backscattering direction leading to an enhancement of scattered light intensity. The enhancement of intensity is proportional to a reduction of light transported in the scattering medium. Thus the CBS signal is a measure of localization of light in the scattering medium. We are building an apparatus to observe weak localization of photons in a high density sample of ultra-cold atoms. First we slow the atoms from room temperature (300 m/s) to less than 10 cm/s in a magneto-optical trap (MOT) where the atom number density is 10 11 atoms/cm 3 . In order to increase the atomic density the atoms in the MOT are transferred to a far detuned microscopic dipole trap created by a laser focused to a waist of approximately 5m. We have successfully loaded the MOT and are now in the process of loading the high density microscopic dipole trap. Once this is achieved we will look at the CBS signal as a function of the atom number density and the scattering cross section. The goal of the project is to reach the Joffe-Regel region where mean free path length is about the wavelength of the scattering radiation.

Summary form only given. A wave propagating in a strongly scattering medium experiences many scattering events which rapidly erase the memory of its initial direction on a typical scale length known as the transport mean free path. It is now known that interference can profoundly alter the wave transport, a spectacular manifestation being weak and strong localisation of waves. We shall briefly review the basics of coherent backscattering (CBS) and the results obtained with classical scatterers. We shall then describe our experiment using cold atoms and discuss the experimental data. The non trivial role of the atomic quantum internal structure in the enhancement reduction will be singled out in a simple situation and results of analytical calculations will be presented.

Since the work of Anderson on localization, interference effects for the propagation of a wave in the presence of disorder have been extensively studied, as exemplified in coherent backscattering (CBS) of light. In the multiple scattering of light by a disordered sample of thermal atoms, interference effects are usually washed out by the fast atomic motion. This is no longer true for cold atoms where CBS has recently been observed. However, the internal structure of the atoms strongly influences the interference properties. In this paper, we consider light scattering by an atomic dipole transition with arbitrary degeneracy and study its impact on coherent backscattering. We show that the interference contrast is strongly reduced. Assuming a uniform statistical distribution over internal degrees of freedom, we compute analytically the single- and double-scattering contributions to the intensity in the weak-localization regime. The so-called ladder and crossed diagrams are generalized to the case of atoms and permit to calculate enhancement factors and backscattering intensity profiles for polarized light and any closed atomic dipole transition.

We report on the direct observation of coherent backscattering (CBS) of ultracold atoms in a quasi-two-dimensional configuration. Launching atoms with a well-defined momentum in a laser speckle disordered potential, we follow the progressive build up of the momentum scattering pattern, consisting of a ring associated with multiple elastic scattering, and the CBS peak in the backward direction. Monitoring the depletion of the initial momentum component and the formation of the angular ring profile allows us to determine microscopic transport quantities. We also study the time evolution of the CBS peak and find it in fair agreement with predictions, at long times as well as at short times. The observation of CBS can be considered a direct signature of coherence in quantum transport of particles in disordered media. It is responsible for the so called weak localization phenomenon, which is the precursor of Anderson localization.

We present an experimental study of coherent backscattering (CBS) of photon noise from multiple scattering media. We use a pseudothermal light source with a microsecond coherence time to produce a noise spectrum covering a continuous transition, from wave fluctuations to shot noise over several MHz. The angle-dependent Fano factor of backscattered light shows an enhancement due to CBS in the wave fluctuation regime. The CBS line shape and enhancement factor of the noise power is consistent with theory in the weak-scattering limit and for a large number of open reflection channels. These initial experiments on weakly scattering media demonstrate that sensitive noise measurements can be combined with the separation of path lengths present in CBS, opening up new experiments on noise transport in the localization regime.