130 research outputs found
Cooperative atomic scattering of light from a laser with a colored noise spectrum
The collective atomic recoil lasing is studied for an ultra-cold and
collisionless atomic gas in a partially coherent pump with a colored noise.
Compared to white noise, correlations in colored noise are found to be able to
greatly enhance or suppress the growth rate, above or below a critical
detuning. Effects on cooperative scattering of light for noise correlation
time, noise intensity and pump-probe detuning are discussed. This result is
consistent with our simulation and linear analysis about the evolution
equations in the regions of instability.Comment: 6 pages; 5figure
High Order Momentum Modes by Resonant Superradiant Scattering
The spatial and time evolutions of superradiant scattering are studied
theoretically for a weak pump beam with different frequency components
traveling along the long axis of an elongated Bose-Einstein condensate.
Resulting from the analysis for mode competition between the different resonant
channels and the local depletion of the spatial distribution in the
superradiant Rayleigh scattering, a new method of getting a large number of
high-order forward modes by resonant frequency components of the pump beam is
provided, which is beneficial to a lager momentum transfer in atom manipulation
for the atom interferometry and atomic optics.Comment: 7 pages, 7 figure
Density Operator Description of Atomic Ordered Spatial Modes in Cavity QED
We present a quantum Monte-Carlo simulation for a pumped atom in a strong
coupling cavity with dissipation, where two ordered spatial modes are formed
for the atomic probability density, with the peaks distributed either only in
the odd sites or only in the even ones of the lattice formed by the cavity
field. A mixed state density operator model, which describes the coupling
between different atomic spatial modes and the corresponding cavity field
components, is proposed, which goes beyond the pure state interpretation. We
develop a new decomposition treatment to derive the atomic spatial modes as
well as the cavity field statistics from the simulation results for the steady
state. With this treatment, we also investigate the dynamical process for the
probabilities of the atomic spatial modes in the adiabatic limit. According to
the analysis of the fitting error between the simulation results and the
density operator model, the latter is a good description for the system
A simplified method for calculating the ac Stark shift of hyperfine levels
The ac Stark shift of hyperfine levels of neutral atoms can be calculated
using the third order perturbation theory(TOPT), where the third order
corrections are quadratic in the atom-photon interaction and linear in the
hyperfine interaction. In this paper, we use Green's function to derive the
method which can give close values to those of TOPT for the
differential light shift between two hyperfine levels. It comes with a simple
form and easy incorporation of theoretical and experimental atomic structure
data. Furthermore, we analyze the order of approximation and give the condition
under which method is valid.Comment: 7 pages, 5 figure
A momentum filter for atomic gas
We propose and demonstrate a momentum filter for atomic gas based on a
designed Talbot-Lau interferometer. It consists in two identical optical
standing wave pulses separated by a delay equal to odd multiples of the half
Talbot time. The one dimensional momentum width along the long direction of a
cigar shape condensate is rapidly and greatly purified to a minimum, which
corresponds to the ground state energy of the confining trap in our experiment.
We find good agreement between theoretical analysis and experimental results.
The filter is also effective for non-condensed cold atoms and could be applied
widely.Comment: 9 pages, 6 figures, accepted by New Journal of Physic
Rapid non-adiabatic loading in an optical lattice
We present a scheme for non-adiabatically loading a Bose-Einstein condensate
into the ground state of a one dimensional optical lattice within a few tens of
microseconds typically, i.e. in less than half the Talbot period. This
technique of coherent control is based on sequences of pulsed perturbations and
experimental results demonstrate its feasibility and effectiveness. As the
loading process is much shorter than the traditional adiabatic loading
timescale, this method may find many applications.Comment: 5 pages, 4 figure
Imprinting Light Phase on Matter Wave Gratings in Superradiance Scattering
Superradiance scattering from a Bose-Einstein condensate is studied with a
two-frequency pumping beam. We demonstrate the possibility of fully tuning the
backward mode population as a function of the locked initial relative phase
between the two frequency components of the pumping beam. This result comes
from an imprinting of this initial relative phase on two matter wave gratings,
formed by the forward mode or backward mode condensate plus the condensate at
rest, so that cooperative scattering is affected. A numerical simulation using
a semiclassical model agrees with our observations.Comment: 6 pages, 11 figure
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