21 research outputs found
Cavity-Controlled Collective Scattering at the Recoil Limit
We study collective scattering with Bose-Einstein condensates interacting
with a high-finesse ring cavity. The condensate scatters the light of a
transverse pump beam superradiantly into modes which, in contrast to previous
experiments, are not determined by the geometrical shape of the condensate, but
specified by a resonant cavity mode. Moreover, since the recoil-shifted
frequency of the scattered light depends on the initial momentum of the
scattered fraction of the condensate, we show that it is possible to employ the
good resolution of the cavity as a filter selecting particular quantized
momentum states.Comment: 4 pages, 4 figure
Spatial and temporal localization of light in two dimensions
Quasi-resonant scattering of light in two dimensions can be described either
as a scalar or as a vectorial electromagnetic wave. Performing a scaling
analysis we observe in both cases long lived modes, yet only the scalar case
exhibits Anderson localized modes together with extremely long mode lifetimes.
We show that the localization length of these modes is influenced only by their
position, and not their lifetime. Investigating the reasons for the absence of
localization, it appears that both the coupling of several polarizations and
the presence of near-field terms are able to prevent long lifetimes and
Anderson localization.Comment: 5 pages, 4 figures and Supplementary Informatio
Synchronization of Bloch oscillations by a ring cavity
We consider Bloch oscillations of ultracold atoms stored in a one-dimensional
vertical optical lattice and simultaneously interacting with a unidirectionally
pumped optical ring cavity whose vertical arm is collinear with the optical
lattice. We find that the feedback provided by the cavity field on the atomic
motion synchronizes Bloch oscillations via a mode-locking mechanism, steering
the atoms to the lowest Bloch band. It also stabilizes Bloch oscillations
against noise, and even suppresses dephasing due to atom-atom interactions.
Furthermore, it generates periodic bursts of light emitted into the
counter-propagating cavity mode, providing a non-destructive monitor of the
atomic dynamics. All these features may be crucial for future improvements of
the design of atomic gravimeters based on recording Bloch oscillations.Comment: 14 pages, 7 figure
Coherence effects in scattering order expansion of light by atomic clouds
We interpret cooperative scattering by a collection of cold atoms as a
multiple scattering process. Starting from microscopic equations describing the
response of atoms to a probe light beam, we represent the total scattered
field as an infinite series of multiple scattering events. As an application of
the method, we obtain analytical expressions of the coherent intensity in the
double scattering approximation for Gaussian density profiles. In particular,
we quantify the contributions of coherent backward and forward scattering.Comment: 10 pages, 6 figure
Interplay between radiation pressure force and scattered light intensity in the cooperative scattering by cold atoms
The interplay between the superradiant emission of a cloud of cold two-level
atoms and the radiation pressure force is discussed. Using a microscopic model
of coupled atomic dipoles driven by an external laser, the radiation field and
the average radiation pressure force are derived. A relation between the
far-field scattered intensity and the force is derived, using the optical
theorem. Finally, the scaling of the sample scattering cross section with the
parameters of the system is studied.Comment: 10 pages, 3 figures, article for special issue of PQE 201
Cavity-Controlled Collective Scattering at the Recoil Limit
We study collective scattering with Bose-Einstein condensates interacting
with a high-finesse ring cavity. The condensate scatters the light of a
transverse pump beam superradiantly into modes which, in contrast to previous
experiments, are not determined by the geometrical shape of the condensate, but
specified by a resonant cavity mode. Moreover, since the recoil-shifted
frequency of the scattered light depends on the initial momentum of the
scattered fraction of the condensate, we show that it is possible to employ the
good resolution of the cavity as a filter selecting particular quantized
momentum states.Comment: 4 pages, 4 figure
Photonic Band Gaps in One-Dimensionally Ordered Cold Atomic Vapors
We experimentally investigate the Bragg reflection of light at
one-dimensionally ordered atomic structures by using cold atoms trapped in a
laser standing wave. By a fine tuning of the periodicity, we reach the regime
of multiple reflection due to the refractive index contrast between layers,
yielding an unprecedented high reflectance efficiency of 80%. This result is
explained by the occurrence of a photonic band gap in such systems, in
accordance with previous predictions