93 research outputs found
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
An optical phase-locking with large and tunable frequency difference based on vertical-cavity surface-emitting laser
We present a novel technique to phase-lock two lasers with controllable
frequency difference. In our setup, one sideband of a current modulated
Vertical-Cavity Surface-Emitting Laser (VCSEL) is phase locked to the master
laser by injection seeding, while another sideband of the VCSEL is used to
phase lock the slave laser. The slave laser is therefore locked in phase with
the master laser, with a frequency difference tunable up to about 35 GHz. The
sideband suppression rate of the slave laser is more than 30dB at 30 uW seed
power. The heterodyne spectrum between master and slave has a linewidth of less
than 1 Hz. A coherent population trapping resonance of rubidium is achieved
using such beams.Comment: 4 pages, 4 Encapsulated PostScript figure
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
Resonant sequential scattering in two-frequency-pumping superradiance from a Bose-Einstein condensate
We study sequential scattering in superradiance from a Bose-Einstein
condensate pumped by a two-frequency laser beam. We find that the distribution
of atomic side modes presents highly different patterns for various frequency
difference between the two pump components. A novel distribution is observed,
with a frequency difference of eight times the recoil frequency. These
observations reveal that the frequency overlap between the end-fire modes
related to different side modes plays an essential role in the dynamics of
sequential superradiant scattering. The numerical results from a semiclassical
model qualitatively agree with our observations.Comment: Submitted to PR
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
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
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