253 research outputs found
The Semiclassical and Quantum Regimes of Superradiant Light Scattering from a Bose-Einstein Condensate
We show that many features of the recent experiments of Schneble et al. [D.
Schneble, Y. Torii, M. Boyd, E.W. Streed, D.E. Pritchard and W. Ketterle,
Science vol. 300, p. 475 (2003)], which demonstrate two different regimes of
light scattering by a Bose-Einstein condensate, can be described using a
one-dimensional mean-field quantum CARL model, where optical amplification
occurs simultaneously with the production of a periodic density modulation in
the atomic medium. The two regimes of light scattering observed in these
experiments, originally described as ``Kapiza-Dirac scattering'' and
``Superradiant Rayleigh scattering'', can be interpreted as the semiclassical
and quantum limits respectively of CARL lasing.Comment: 10 pages, 5 figures - to appear in Journal of Optics
Microscopic theory of photonic band gaps in optical lattices
We propose a microscopic model to describe the scattering of light by atoms
in optical lattices. The model is shown to efficiently capture Bragg
scattering, spontaneous emission and photonic band gaps. A connection to the
transfer matrix formalism is established in the limit of a one-dimensional
optical lattice, and we find the two theories to yield results in good
agreement. The advantage of the microscopic model is, however, that it suits
better for studies of finite-size and disorder effects.Comment: 5 pages, 6 figure
Atomic interaction effects in the superradiant light scattering from a Bose-Einstein condensate
We investigate the effects of the atomic interaction in the Superradiant
Rayleigh scattering from a Bose-Einstein condensate driven by a far-detuned
laser beam. We show that for a homogeneous atomic sample the atomic interaction
has only a dispersive effect, whereas in the inhomogeneous case it may increase
the decay of the matter-wave grating.Comment: 12 pages, 4 figures, presented to the XII International Laser Physics
Workshop, August 24-29, Hamburg, to be published in Laser Physic
Theory of collective Raman scattering from a Bose-Einstein condensate
Recent experiments have demonstrated superradiant Raman scattering from a
Bose-Einstein condensate driven by a single off-resonant laser beam. We present
a quantum theory describing this phenomenon, showing Raman amplification of
matter wave due to collective atomic recoil from 3-level atoms in a
-configuration. When atoms are initially in a single lower internal
state, a closed two-level system is realized between atoms with different
internal states, and entangled atom-photon pairs can be generated. When atoms
are initially prepared in both the lower internal states, a fraction of atoms
recoiling in the backward direction can be generated.Comment: 5 pages, 2 figure
Quantum effects in the collective light scattering by coherent atomic recoil in a Bose-Einstein condensate
We extend the semiclassical model of the collective atomic recoil laser
(CARL) to include the quantum mechanical description of the center-of-mass
motion of the atoms in a Bose-Einstein condensate (BEC). We show that when the
average atomic momentum is less than the recoil momentum , the
CARL equations reduce to the Maxwell-Bloch equations for two momentum levels.
In the conservative regime (no radiation losses), the quantum model depends on
a single collective parameter, , that can be interpreted as the average
number of photons scattered per atom in the classical limit. When ,
the semiclassical CARL regime is recovered, with many momentum levels populated
at saturation. On the contrary, when , the average momentum
oscillates between zero and , and a periodic train of
hyperbolic secant pulses is emitted. In the dissipative regime (large radiation
losses) and in a suitable quantum limit, a sequential superfluorescence
scattering occurs, in which after each process atoms emit a hyperbolic
secant pulse and populate a lower momentum state. These results describe the
regular arrangement of the momentum pattern observed in recent experiments of
superradiant Rayleigh scattering from a BEC.Comment: submitted for publication on Phys. Rev.
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
Parametric optimization for an x-ray Free Electron Laser with a laser wiggler
In this paper we optimize the experimental parameters to operate a Free
Electron Laser with a laser wiggler in the Angstrom region. We show that the
quantum regime of the Self Amplified Spontaneous Emission (Quantum SASE) may be
reached with realistic parameters. The classical SASE regime is also discussed
and compared with the quantum regime.Comment: submitted to Phys.Rev.ST-A
Recoil-induced subradiance in a cold atomic gas
Subradiance, i.e. the cooperative inhibition of spontaneous emission by
destructive interatomic interference, can be realized in a cold atomic sample
confined in a ring cavity and lightened by a two-frequency laser. The atoms,
scattering the photons of the two laser fields into the cavity-mode, recoil and
change their momentum. Under proper conditions the atomic initial momentum
state and the first two momentum recoil states form a three-level degenerate
cascade. A stationary subradiant state is obtained after that the scattered
photons have left the cavity, leaving the atoms in a coherent superposition of
the three collective momentum states. After a semiclassical description of the
process, we calculate the quantum subradiant state and its Wigner function.
Anti-bunching and quantum correlations between the three atomic modes of the
subradiant state are demonstrated
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