Publications (You can locate these works by entering H. Y.
Ling as author in the APS website: http://publish.aps.org
.)
1.
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Superfluid pairing in a mixture of a spin-polarized
Fermi gas and a dipolar condensate
Ben Kain and Hong Y.
Ling
Phys. Rev. A
85, 013631 (2012) Published January 23, 2012
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Abstract
A mixture of a spin-polarized Fermi
gas and a dipolar Bose-Einstein condensate is considered in which s-wave
scattering between fermions and the quasiparticles of the dipolar condensate
can result in an effective attractive Fermi-Fermi interaction long-range and
anisotropic in nature and tunable by the dipolar interaction. It is shown
that such an interaction can significantly increase the prospect of realizing
a superfluid with a gap parameter characterized with a coherent superposition
of all odd partial waves. In the spirit of the Hartree-Fock-Bogoliubov
mean-field approach, a theory is formulated that allows the estimation of the
critical temperature when the anisotropic Fock potential is taken into
consideration and the determination of the system parameters that optimize
the critical temperature at which such a superfluid emerges before the system
begins to phase separate.
[View PDF (334 kB)]
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2.
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Cosmological inhomogeneities with
Bose-Einstein condensate dark matter
Ben Kain and Hong Y.
Ling
Phys. Rev. D
85, 023527 (2012) Published January 23, 2012
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Abstract
We consider the growth of cosmological
perturbations to the energy density of dark matter during matter domination
when dark matter is a scalar field that has undergone Bose-Einstein
condensation. We study these inhomogeneities within the framework of both
Newtonian gravity, where the calculation and results are more transparent,
and General Relativity. The direction we take is to derive analytical
expressions, which can be obtained in the small pressure limit. Throughout we
compare our results to those of the standard cosmology, where dark matter is
assumed pressureless, using our analytical expressions to showcase precise
differences. We find, compared to the standard cosmology, that Bose-Einstein
condensate dark matter leads to a scale factor, gravitational potential and
density contrast that increase at faster rates.
[View PDF (230 kB)]
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3.
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Singlet and triplet superfluid competition
in a mixture of two-component Fermi and one-component dipolar Bose gases
Ben Kain and Hong Y.
Ling
Phys. Rev. A
83, 061603 (2011) Published June 22, 2011
Cited 1 time
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Abstract
We consider a mixture of
two-component Fermi and (one-component) dipolar Bose gases in which both
dipolar interaction and s-wave scattering between fermions of opposite
spins are tunable. We show that in the long-wavelength limit, the anisotropy
in the Fermi-Fermi interaction induced by phonons of the dipolar condensate
can strongly enhance the scattering in the triplet channel. We investigate in
detail the conditions for achieving optimal critical temperature at which the
triplet superfluid begins to compete with the singlet superfluid.
[View PDF (170 kB)]
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4.
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Measurement backaction on the quantum
spin-mixing dynamics of a spin-1 Bose-Einstein condensate
Keye Zhang, Lu Zhou,
Hong Y. Ling, Han Pu, and Weiping Zhang
Phys. Rev. A
83, 063624 (2011) Published June 20, 2011
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Abstract
We consider a small F=1
spinor condensate inside an optical cavity driven by an optical probe field,
and subject the output of the probe to a homodyne detection, with the goal of
investigating the effect of measurement backaction on the spin dynamics of
the condensate. Using the stochastic master equation approach, we show that
the effect of backaction is sensitive to not only the measurement strength
but also the quantum fluctuation of the spinor condensate. The same method is
also used to estimate the atom numbers below which the effect of backaction
becomes so prominent that extracting spin dynamics from this cavity-based
detection scheme is no longer practical.
[View PDF (892 kB)]
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5.
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Landau-Ginzburg perspective of
finite-temperature phase diagrams of a two-component Fermi-Bose mixture
Michael Fodor and
Hong Y. Ling
Phys. Rev. A
82, 043610 (2010) Published October 15, 2010
Cited 1 time
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Abstract
We consider a mixture of
two-component Fermi and (one-component) Bose gases under the repulsive
Bose-Fermi and attractive Fermi-Fermi interactions. We perform a systematic
study of the finite-temperature phase diagrams in the chemical potential
space, identifying, using the Landau-Ginzburg theory, the features generic to
the phase diagrams within the validity of our model. We apply the theory to
explore the physics of correlated BCS pairing among fermions in a tightly
confined trap surrounded by a large Bose-Einstein condensate gas.
[View PDF (312 kB)]
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6.
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Vortices in Bose-Einstein condensate dark matter
Ben Kain and Hong Y.
Ling
Phys. Rev. D
82, 064042 (2010) Published September 30, 2010
Cited 5 times
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Abstract
If dark matter in the galactic halo is
composed of bosons that form a Bose-Einstein condensate, then it is likely
that the rotation of the halo will lead to the nucleation of vortices. After
a review of the Gross-Pitaevskii equation, the Thomas-Fermi approximation and
vortices in general, we consider vortices in detail. We find strong bounds
for the boson mass, interaction strength, the shape and quantity of vortices
in the halo, the critical rotational velocity for the nucleation of vortices
and, in the Thomas-Fermi regime, an exact solution for the mass density of a
single, axisymmetric vortex.
[View PDF (1,173 kB)]
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7.
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Spin dynamics and domain formation of a spinor
Bose-Einstein condensate in an optical cavity
Lu Zhou, Han Pu,
Hong Y. Ling, Keye Zhang, and Weiping Zhang
Phys. Rev. A
81, 063641 (2010) Published June 30, 2010
Cited 5 times
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Abstract
We consider a ferromagnetic spin-1
Bose-Einstein condensate (BEC) dispersively coupled to a unidirectional ring
cavity. We show that the ability of the cavity to modify, in a highly
nonlinear fashion, matter-wave phase shifts adds an additional dimension to
the study of spinor condensates. In addition to demonstrating strong
matter-wave bistability as in our earlier publication [ L. Zhou et al.
Phys. Rev. Lett. 103 160403 (2009)],
we show that the interplay between atomic and cavity fields can greatly
enrich both the physics of critical slowing down in spin-mixing dynamics and
the physics of spin-domain formation in spinor condensates.
[View PDF (761 kB)]
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8.
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Achieving ground-state polar molecular condensates by chainwise atom-molecule adiabatic passage
Jing Qian, Weiping Zhang, and Hong
Y. Ling
Phys. Rev. A
81, 013632 (2010) Published January 29, 2010
Cited 3 times
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Abstract
We generalize the idea of chainwise
stimulated Raman adiabatic passage (STIRAP) [ Kuznetsova et al. Phys.
Rev. A 78 021402 (2008)] to a photoassociation-based chainwise
atom-molecule system, with the goal of directly converting two-species atomic
Bose-Einstein condensates (BEC) into a ground polar molecular BEC. We pay
particular attention to the intermediate Raman laser fields, a control knob
inaccessible to the usual three-level model. We find that an appropriate
exploration of both the intermediate laser fields and the stability property
of the atom-molecule STIRAP can greatly reduce the power demand on the
photoassociation laser, a key concern for STIRAPs starting from free atoms
due to the small Franck-Condon factor in the free-bound transition.
[View PDF (317 kB)]
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9.
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Matter-wave bistability in coupled
atom-molecule quantum gases
Lei Jiang, Han Pu,
Andrew Robertson, and Hong Y. Ling
Phys. Rev. A
81, 013619 (2010) Published January 20, 2010
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Abstract
We study the matter-wave bistability
in coupled atom-molecule quantum gases, in which heteronuclear molecules are
created via an interspecies Feshbach resonance involving either two-species
Bose or two-species Fermi atoms at zero temperature. We show that the
resonant two-channel Bose model is equivalent to the nondegenerate parametric
down-conversion in quantum optics, while the corresponding Fermi model can be
mapped to a quantum optics model that describes a single-mode laser field
interacting with an ensemble of inhomogeneously broadened two-level atoms.
Using these analogies and the fact that both models are subject to the Kerr
nonlinearity due to the two-body s-wave collisions, we show that under
proper conditions, the population in the molecular state in both models can
be made to change with the Feshbach detuning in a bistable fashion.
[View PDF (390 kB)]
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10.
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Cavity-Mediated Strong Matter Wave Bistability in a Spin-1 Condensate
Lu Zhou, Han Pu,
Hong Y. Ling, and Weiping Zhang
Phys. Rev. Lett. 103, 160403 (2009) Published
October 15, 2009
Cited 13 times
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Abstract
We study matter-wave bistability in
a spin-1 Bose-Einstein condensate dispersively coupled to a unidirectional
ring cavity. A unique feature is that the population exchange among different
modes of matter fields is accomplished via spin-exchange collisions. We show
that the interplay between the atomic spin mixing and the cavity light field
can lead to a strong matter-wave nonlinearity, making matter-wave bistability
in a cavity at the single-photon level achievable.
[View PDF (425 kB)]
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11.
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Detection of Fermi pairing via electromagnetically induced
transparency
Lei Jiang, Han Pu, Weiping Zhang, and Hong Y. Ling
Phys. Rev. A
80, 033606 (2009) Published September 9, 2009
Cited 3 times
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Abstract
An optical spectroscopic method
based on the principle of electromagnetically induced transparency (EIT) is
proposed as quite a generic probing tool that provides valuable insights into
the nature of Fermi paring in ultracold Fermi gases of two hyperfine states.
This technique has the capability of allowing spectroscopic response to be
determined in a nearly nondestructive manner and the whole spectrum may be
obtained by scanning the probe-laser frequency faster than the lifetime of
the sample without re-preparing the atomic sample repeatedly. A quasiparticle
picture is constructed to facilitate a simple physical explanation of the pairing
signature in the EIT spectra.
[View PDF (292 kB)]
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12.
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Phase separation in a two-species atomic Bose-Einstein condensate with
an interspecies Feshbach resonance
Lu Zhou, Jing Qian, Han Pu, Weiping Zhang,
and Hong Y. Ling
Phys. Rev. A
78, 053612 (2008) Published November 6, 2008
Cited 13 times
Show
Abstract
We consider a mixture of two-species
atomic Bose-Einstein condensates coupled to a bound molecular state at zero
temperature via an interspecies Feshbach resonance. The interspecies Feshbach
coupling precludes the possibility of doubly mixed phases while enables not
only the pure molecular superfluid but also the pure atomic superfluids to
exist as distinct phases. We show that this system is able to support a rich
set of phase separations, including that between two distinct mixed
atom-molecule phases. We pay particular attention to the effects of the
Feschbach coupling and the particle collisions on the miscibility of this
multicomponent condensate system.
[View PDF (605 kB)]
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13.
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Goos-Hδnchen-like shifts in atom optics
Jianhua
Huang, Zhenglu Duan, Hong
Y. Ling, and Weiping Zhang
Phys. Rev. A
77, 063608 (2008) Published June 11, 2008
Cited 7 times
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Abstract
We consider the propagation of a
matter wave packet of two-level atoms through a square potential created by a
super-Gaussian laser beam. We explore the matter wave analog of Goos-Hδnchen
shift within the framework of atom optics where the roles of atom and light
are exchanged with respect to conventional optics. Using a vector theory,
where atoms are treated as particles possessing two internal spin components,
we show that not only large negative but also large positive Goos-Hδnchen
shifts can occur in the reflected atomic beam.
[View PDF (281 kB)]
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14.
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Macroscopic Atom-Molecule Dark State and
Its Collective Excitations in Fermionic Systems
Andrew Robertson,
Lei Jiang, Han Pu, Weiping Zhang, and Hong Y. Ling
Phys. Rev. Lett. 99, 250404 (2007) Published
December 18, 2007
Cited 7 times
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Abstract
We show that a robust macroscopic
atom-molecule dark state can exist in fermionic systems, which represents a
coherent superposition between the ground molecular Bose-Einstein condensates
and the atomic BCS paired state. We take advantage of the tunability offered
by external laser fields, and explore this superposition for demonstrating
coherent oscillations between ground molecules and atom pairs. We interpret
the oscillation frequencies in terms of the collective excitations of the
dark state.
[View PDF (367 kB)]
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15.
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Properties of a coupled two-species atomheteronuclear-molecule
condensate
Lu Zhou, Weiping Zhang, Hong Y. Ling, Lei Jiang, and Han Pu
Phys. Rev. A
75, 043603 (2007) Published April 3, 2007
Cited 12 times
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Abstract
We study the coherent association of
a two-species atomic condensate into a condensate of heteronuclear diatomic
molecules, using both a semiclassical treatment and a quantum mechanical
approach. The differences and connections between the two approaches are
examined. We show that, in this coupled nonlinear atom-molecule system, the
population difference between the two atomic species plays a significant role
in the ground-state stability properties as well as in coherent population
oscillation dynamics.
[View PDF (453 kB)]
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16.
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Adiabatic theorem for a condensate system in an atom-molecule dark
state
Hong Y. Ling, Peter Maenner, Weiping Zhang, and Han
Pu
Phys. Rev. A
75, 033615 (2007) Published March 26, 2007
Cited 18 times
Show
Abstract
We consider the adiabatic evolution
of an atom-molecule dark state in a collisional two-color Raman
photoassociation condensate system. By linking nonadiabaticity with the
population growth in the collective excitations of the dark state, we develop
an adiabatic theorem where we have consistently addressed the issues related
to the Goldstone mode and the biorthonormality of the collective modes. We
apply this theorem to specific examples to demonstrate its use in designing
pulses that can optimize the yield of ground molecule production in the
stimulated Raman adiabatic passage process.
[View PDF (369 kB)]
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17.
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Adiabatic Condition for Nonlinear Systems
Han Pu, Peter Maenner, Weiping Zhang, and
Hong Y. Ling
Phys. Rev. Lett. 98, 050406 (2007) Published
February 2, 2007
Cited 41 times
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Abstract
The adiabatic approximation is an
important concept in quantum mechanics. In linear systems, the adiabatic condition
is derived with the help of the instantaneous eigenvalues and eigenstates of
the Hamiltonian, a procedure that breaks down in the presence of
nonlinearity. Using an explicit example relevant to photoassociation of atoms
into diatomic molecules, we demonstrate that the proper way to derive the
adiabatic condition for nonlinear mean-field (or classical) systems is
through a linearization procedure, using which an analytic adiabatic
condition is obtained for the nonlinear model under study.
[View PDF (166 kB)]
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18.
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Molecular vortex generated from an atom-molecule dark state
H. Y. Ling, S. Yi,
H. Pu, D. E. Grochowski, and Weiping
Zhang
Phys. Rev. A
73, 053612 (2006) Published May 26, 2006
Cited 4 times
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Abstract
We consider a Raman photoassociation
model in a field configuration in which a Gaussian and a first-order Laguerre
Gaussian laser field are applied between the bound-bound and free-bound
transitions, respectively. We show that such a configuration can lead to a
coherent population trapping superposition of an atomic condensate and a
ground molecular vortex of unit winding number. We develop stimulated Raman
adiabatic passages that minimize the effect of mean-field shifts due to
collisions, for optimal conversion of an atomic condensate into a ground
molecular vortex.
[View PDF (116 kB)]
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19.
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Coherent population trapping and dynamical instability in coupled
atom-molecule condensates
H. Y. Ling, P. Maenner, and H. Pu
Phys. Rev. A
72, 013608 (2005) Published July 18, 2005
Cited 10 times
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Abstract
Coherent population trapping (CPT)
is an important concept in many subfields of physics and chemistry. Here we analyze
the collective excitation spectrum of the CPT states in a coupled
atom-molecule condensate system. We find that collisions between particles
can cause the CPT state to be dynamically unstable, which is a unique feature
of the nonlinear system. We obtain a set of analytical criteria for
determining the stability properties of the CPT state in the long-wavelength
limit. We construct stability diagrams and provide a systematic
classification of various instabilities according to collisional interaction
strengths.
[View PDF (319 kB)]
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20.
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Creating a Stable Molecular Condensate
Using a Generalized Raman Adiabatic Passage Scheme
Hong Y. Ling, Han
Pu, and Brian Seaman
Phys. Rev. Lett. 93, 250403 (2004) Published
December 15, 2004
Cited 59 times
Show
Abstract
We study the Feshbach resonance assisted
stimulated adiabatic passage of an effective coupling field for creating
stable molecules from an atomic Bose condensate. By exploring the properties
of the coherent population trapping state, we show that, contrary to the
previous belief, mean-field shifts need not limit the conversion efficiency
as long as one chooses an adiabatic passage route that compensates the
collision mean-field phase shifts and avoids the dynamical unstable regime.
[View PDF (239 kB)]
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21.
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Optical-cavity-assisted four-wave parametric amplification of atomic
fields
Hong Y. Ling
Phys. Rev. A
65, 013608 (2001) Published December 14, 2001
Cited 3 times
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Abstract
We consider a system composed of a
cavity field, a counterpropagating pump laser field, and a two-level Bose
condensate travelling along a direction normal to the optical fields. We reduce
the system, in the limit of first-order scattering approximation, to a
four-wave parametric amplifier involving three momentum modes and an
effective two-photon cavity mode. We treat this wave mixing as a multimode
laser operation, and discuss the mode-locking condition under which these
laser modes can be synchronized to operate in a continuous wave fashion. We
derive the threshold lasing condition and discuss it in analogy with the
Raman-anti-Stokes process in nonlinear optics. We develop a matrix formalism
that enables the longitudinal spatial degree of freedom to be integrated
analytically, leading to an efficient numerical algorithm for determining the
steady states and their stabilities. Numerical examples will be provided and
discussed. In particular, instability analysis seems to suggest Bose-Einstein
condensate holds a great promise for nonlinear instability studies because of
its unprecedented long interaction time with photons.
[View PDF (179 kB)]
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22.
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Theory of a collective atomic recoil laser
H. Y. Ling, H. Pu,
L. Baksmaty, and N. P. Bigelow
Phys. Rev. A
63, 053810 (2001) Published April 17, 2001
Cited 8 times
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Abstract
We perform a study of a collective
atomic recoil laser (CARL) that goes beyond the initial growth period. The
study is based on a theory that treats both internal and external degrees of
atomic freedom quantum mechanically but regards the laser light as a
classical field obeying Maxwells equations. We introduce the concepts of
momentum families and diffraction groups and organize the matter wave
equations in terms of diffraction groups. The steady-state lasing conditions
are discussed in connection with the probe gain in the recoil-induced
resonances. The nontrivial steady states and the linear stability analysis of
the steady states are both carried out by the method of two-dimensional
continued fractions. Both stable and unstable nontrivial steady states are
calculated and discussed in the context of regarding the CARL as multiwave
mixing involving many modes of matter waves and two optical fields.
[View PDF (229 kB)]
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23.
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Effect of atomic recoil on the absorption spectrum of driven V-type
atoms
Hong Y. Ling and
Anthony Williams
Phys. Rev. A
60, 4812 (1999) Published December 1, 1999
Cited 2 times
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Abstract
A numerical method is developed for
a V system driven by two counterpropagating laser fields in a momentum regime
where a full quantum-mechanical treatment of the atomic variables is
necessary. This method is based on a transformation by which integral
equations, reduced from steady-state optical-Bloch-type equations involving
the atomic center-of-mass momentum, can be transformed into inhomogeneous
tridiagonal vector recurrence equations. The effect of the atomic recoil on
the momentum distribution in the absence of the probe field, and, in
particular, the absorption spectrum in a copropagating spectrum configuration
is analyzed and discussed. Special attention is given to the Rayleigh
resonance of subnatural linewidth.
[View PDF (160 kB)]
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24.
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Several asymptotic subrecoil laser-cooling
behaviors in arbitrary degenerate Λ systems
Hong Yuan Ling
Phys. Rev. A
59, 3714 (1999) Published May 1, 1999
Cited 3 times
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Abstract
Subrecoil cooling can be achieved in
three-level Λ-type atoms subject to counterpropagating laser beams via
velocity-selective coherent population trapping [A. Aspect et al., J.
Opt. Soc. Am. B 6, 2112 (1989)]. This process leads to narrow peaks in
the ground but a flat structure in the excited atomic momentum distributions.
By taking advantage of this difference, we construct several analytical
functions from which the main cooling features (with the exception of the
scaling law about the fraction of subrecoil cooled atoms) can be approximated
under arbitrary parameters. This method allows us to generalize the
peak-momentum width from symmetric to arbitrary degenerate Λ systems,
and to discuss analytically the small dependence of the momentum
distributions on the laser detuning near the two-photon resonance.
[View PDF (192 kB)]
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25.
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Electromagnetically induced grating: Homogeneously broadened medium
Hong Yuan Ling,
Yong-Qing Li, and Min Xiao
Phys. Rev. A
57, 1338 (1998) Published February 1, 1998
Cited 55 times
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Abstract
A strong coupling standing wave,
interacting with three-level Λ-type (or ladder-type) atoms, can diffract
a weak probe field (propagating along a direction normal to the standing
wave) into high-order diffractions, a phenomenon which we name
electromagnetically induced grating (EIG). We develop in this work a theory
for studying EIG in a homogeneously broadened medium consisting of
three-level Λ-type atoms. We show that by taking advantage of the
absorption and dispersion properties of electromagnetically induced
transparency one can create an atomic grating that can effectively diffract
light into the first-order direction.
[View PDF (152 kB)]
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