8 research outputs found
Collapses and revivals of stored orbital angular momentum of light in a cold atomic ensemble
We report on the storage of orbital angular momentum of light in a cold
ensemble of cesium atoms. We employ Bragg diffraction to retrieve the stored
optical information impressed into the atomic coherence by the incident light
fields. The stored information can be manipulated by an applied magnetic field
and we were able to observe collapses and revivals due to the rotation of the
stored atomic Zeeman coherence for times longer than 15 .Comment: Submitted to Physical Review
Dynamics of a stored Zeeman coherence grating in an external magnetic field
We investigate the evolution of a Zeeman coherence grating induced in a cold
atomic cesium sample in the presence of an external magnetic field. The
gratings are created in a three-beam light storage configuration using two
quasi-collinear writing laser pulses and reading with a counterpropagating
pulse after a variable time delay. The phase conjugated pulse arising from the
atomic sample is monitored. Collapses and revivals of the retrieved pulse are
observed for different polarizations of the laser beams and for different
directions of the applied magnetic field. While magnetic field inhomogeneities
are responsible for the decay of the coherent atomic response, a five-fold
increase in the coherence decay time, with respect to no applied magnetic
field, is obtained for an appropriate choice of the direction of the applied
magnetic field. A simplified theoretical model illustrates the role of the
magnetic field mean and its inhomogeneity on the collective atomic response.Comment: To appear in J. Phys.
Dynamics of saturated Bragg diffraction in a stored light grating in cold atoms
We report on a detailed investigation of the dynamics and the saturation of a
light grating stored in a sample of cold cesium atoms. We employ Bragg
diffraction to retrieve the stored optical information impressed into the
atomic coherence by the incident light fields. The diffracted efficiency is
studied as a function of the intensities of both writing and reading laser
beams. A theoretical model is developed to predict the temporal pulse shape of
the retrieved signal and compares reasonably well with the observed results.Comment: Submitted to Phys. Rev.
Delayed four- and six-wave mixing in a coherently prepared atomic ensemble
We report on the simultaneous observation, by delayed Bragg diffraction, of
four- and six-wave mixing processes in a coherently prepared atomic ensemble
consisting of cold cesium atoms. For each diffracted order, we observe
different temporal pulse shapes and dependencies with the intensities of the
exciting fields, evidencing the different mechanisms involved in each process.
The various observations are well described by a simplified analytical theory,
which considers the atomic system as an ensemble of three-level atoms in
{\Lambda} configuration
All-optical 3D atomic loops generated with Bessel light fields
The propagation invariance of Bessel beams as well as their transversal
structure are used to perform a comparative analysis of their effect on cold
atoms for four different configurations and combinations thereof. We show that,
even at temperatures for which the classical description of the atom center of
mass motion is valid, the interchange of momentum, energy and orbital angular
momentum between light and atoms yields efficient tools for all-optical
trapping, transporting and, in general, manipulating the state of motion of
cold atoms.Comment: 13 pages, 9 figure