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1.
N. Vujičić S. Vdović D. Aumiler T. Ban H. Skenderović G. Pichler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):447-454
We present direct observation of the velocity-selective optical pumping of
the Cs ground state hyperfine levels induced by the femtosecond (fs) laser
oscillator centered at either D2 (6 2S1/2↦6 2P3/2,
852 nm) or D1 (6
P1/2, 894 nm) cesium
line. We utilized previously developed modified direct frequency comb
spectroscopy (DFCS) which uses a fixed frequency comb for the excitation and
a weak cw scanning probe laser centered at the 133Cs 6
2S1/2↦6 2P3/2 transition (D2 line) for ground
levels population monitoring. The frequency comb excitation changes the
usual Doppler absorption profile into a specific periodic, comblike
structure. The mechanism of the velocity selective population transfer
between the Cs ground state hyperfine levels induced by fs pulse train
excitation is verified in a theoretical treatment of the multilevel atomic
system subjected to a pulse train resonant field interaction. 相似文献
2.
X.-J. Liu H. Jing M.-L. Ge 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(2):297-303
We examine in detail the quantum memory technique for photons in a
double Λ atomic ensemble in this work. The novel
application of the present technique to create two different
quantum probe fields as well as entangled states of them is
proposed. A larger zero-degeneracy class besides dark-state
subspace is investigated and the adiabatic condition is confirmed
in the present model. We extend the single-mode quantum memory
technique to the case with multi-mode probe fields, and reveal the
exact pulse matching phenomenon between two quantized pulses in
the present system. 相似文献
3.
A.V. Papoyan M. Auzinsh K. Bergmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(1):63-71
We report results of a theoretical and experimental study of the ground state nonlinear Hanle effect under strong laser excitation.
It is shown that besides the well-known zero-magnetic field suppression of absorption on F
g = F→F
e = F - 1 transitions caused by population trapping, an optical pumping induced enhanced absorption occurs on F
g = F→F
e = F + 1 transitions for small B-fields. The latter effect becomes more pronounced for high F values. The experiment with atomic vapor of Cs (D2 line, F
g = 4) confirms an increase of the spectrally unresolved fluorescence yield at zero magnetic field and 600 mW/cm2 laser intensity by 9% or 42%, when excitation occurs with linearly or circularly polarized light, respectively. The results
of the experiment agree with numerical simulation studies using equations of motion for a density matrix.
Received 24 November 2001 / Received in final form 25 March 2002 Published online 24 September 2002 相似文献
4.
J. H. Li X. X. Yang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):563-569
We theoretically investigate the features of two-photon absorption
in a five-level atomic system with interacting dark resonances. It
is found that two-photon absorption can be completely suppressed
at two different frequencies due to the application of two
coherent coupling fields and the atomic system exhibits double
electromagnetically induced transparency windows against
two-photon absorption. The position and width of the double
two-photon transparency windows can be controlled via properly
adjusting the frequency detuning and the intensities of the two
coupling fields. In addition, one enhanced narrow central line can
be observed in the two-photon absorption spectra, which may find
applications in high-precision spectroscopy. Form a physical point
of view, we explicitly explain these results in terms of quantum
interference induced by three different two-photon excitation
channels in the dressed-state picture. 相似文献
5.
J. -B. Liu X. -Y. Lü N. Liu P. Huang C. -L. Ding J. Li 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):479-484
Using the Schrödinger-Maxwell equations, we theoretically investigate the propagation properties of a transverse acoustic wave in a crystal of molecular magnets in the presence of two strong ac resonant magnetic fields and a weak acoustic wave. The acoustic wave can freely propagate in the magnetic molecule medium (under appropriate conditions) due to quantum interference. Furthermore, using the slowly varying envelope approximation, we discuss the propagation equation of the acoustic wave, which includes the high order nonlinear term. The results show that a crystal of molecular magnets can support the propagation of acoustic wave solitons via electromagnetically induced transparency. We also obtain the analytical expressions for the phase shift and absorption coefficient of the acoustic wave within certain parameters. 相似文献
6.
W.-H. Sun S.-D. Du X.-S. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(2):397-404
We investigate the phase probability distribution (PPD) of a single-mode
micromaser pumped by atoms injected in the most general case, i.e. in the
superposition of the upper, intermediate and lower states by the Monte
Carlo wave function approach. The phase properties of the cavity mode are
greatly influenced by the relative phases and the amplitudes of the
polarized atoms, and the detunings between the atom and cavity. The cavity
field has a single preferred phase if the cavity is pumped by the atoms in
the superposition of the upper and intermediate states or of the
intermediate and lower states. However, a double-peak feature appears in the
PPD of the cavity field when the cavity is pumped by the atoms in the
superposition of the upper and lower states. With appropriate detunings, the
double peaks become narrower and more remarkable, which shows the better
defined phase of the cavity field, as compared to the resonant case. The PPD
displays complicated characteristics when the cavity is pumped by the atoms
in the superposition of the upper, intermediate and lower states. The phase
distribution changes from a single peak to double peaks and to another
single peak when we modulate the phase of the intermediate state, which has
been explained in the semi-classical radiation theory. 相似文献
7.
E.A. Korsunsky T. Halfmann J.P. Marangos K. Bergmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(1):167-180
Four-wave mixing in resonant atomic vapors based on maximum coherence induced by Stark-chirped rapid adiabatic passage (SCRAP)
is investigated theoretically. We show the advantages of a coupling scheme involving maximum coherence and demonstrate how
a large atomic coherence between a ground and an highly excited state can be prepared by SCRAP. Full analytic solutions of
the field propagation problem taking into account pump field depletion are derived. The solutions are obtained with the help
of an Hamiltonian approach which in the adiabatic limit permits to reduce the full set of Maxwell-Bloch equations to simple
canonical equations of Hamiltonian mechanics for the field variables. It is found that the conversion efficiency reached is
largely enhanced if the phase mismatch induced by linear refraction is compensated. A detailed analysis of the phase matching
conditions shows, however, that the phase mismatch contribution from the Kerr effect cannot be compensated simultaneously
with linear refraction contribution. Therefore, the conversion efficiency in a coupling scheme involving maximum coherence
prepared by SCRAP is high, but not equal to unity.
Received 16 August 2002 Published online 4 February 2003
RID="a"
ID="a"e-mail: korsunsky@physik.uni-kl.de 相似文献
8.
M. M. Hossain S. Mitra S. Chakrabarti D. Bhattacharyya B. Ray P. N. Ghosh 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(2):141-146
We report the experimental observation of electromagnetically induced transparency (EIT) in a Doppler broadened rubidium vapour
at room temperature for different probe intensities at a fixed pump intensity in a five-level Λ-type system formed by the
D2 transition of 85Rb. For a constant pump intensity, we find that the EIT width and height change with the variation of probe intensity. We
observe a nonlinear variation of the height of the EIT peak and a linear variation of the width (FWHM) of the EIT signal with
probe intensity. In the Doppler broadened multilevel system, we also observe the velocity selective dips along with the EIT
signal. A numerical simulation of the probe response signal based on density matrix representation in a five-level system
is carried out to reproduce the experimentally observed spectra. 相似文献
9.
K. I. Osman S. S. Hassan A. Joshi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(1):119-130
The effects of spontaneously generated coherence (SGC) and phases of
optical fields on the phenomenon of electromagnetically induced
transparency (EIT) are investigated in a four-level inverted-Y
system and in a five-level K-type system under various parametric
conditions in order to demonstrate controllability of the EIT,
dispersion properties, and group velocity in such systems. Non-zero
second-order susceptibility in both systems is due to the SGC
effect. The experimental viability of the model in semiconductor
quantum well systems is also discussed. 相似文献
10.
C. Ottaviani S. Rebić D. Vitali P. Tombesi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(2):281-296
The interaction of a five-level atomic system involving electromagnetically induced transparency with four light fields is
investigated.
Two different light-atom configurations are considered, and their efficiency in generating large nonlinear cross-phase shifts
compared.
The dispersive properties of those schemes are analyzed in detail, and the conditions leading to group velocity matching for
two of the light
fields are identified. An analytical
treatment based on amplitude equations is used in order to obtain approximate solutions for the susceptibilities, which are
shown to fit well
with the numerical solution of the full Bloch equations in a large parameter region. 相似文献
11.
Q. Xu X. M. Hu J. W. Yin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(2):267-273
The atomic coherence in a three-level Λ atom is studied, in which each optical transition is driven by a coherent field and
the metastable states are coupled to each other via a microwave field. It’s shown that the atomic coherence crucially depends
on the relative phase delay between the envelopes of the amplitudes of the three coupling fields. In particular, when the
phase delay is adjusted to 0 or π, the maximal atomic coherence arises, while the maximal atomic coherence doesn’t occur once
the phase delay is changed to π/2. The maximal atomic coherence is attributed to the trapping of the population in the lower
sublevels. 相似文献
12.
M. Gartz C. Keutgen S. Kuenneke U. Kreibig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(1):127-131
In this paper a detailed experimental study of Coherent Population Trapping (CPT) effect on sodium induced by a dye-laser
operating in a three-mode regime is presented and a detailed analysis of the role of velocity changing collisions is made.
These collisions show a very small relaxation effect on the dark resonances which are visible even at high pressures. For
the first time we demonstrate the persistence of the ground state coherence to pressures up to one atmosphere for a relatively
“heavy” buffer gas like argon. The experimental results have been compared with theory and a very good agreement has been
obtained. Preliminary results on the effect of Na-N2 collisions on Coherent Population Trapping are presented.
Received: 5 October 1998 / Received in final form: 3 December 1998 相似文献
13.
K. Jin Z. C. Wang Q. Zhang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):325-332
We study the absorption spectra of a degenerate V-type
atom, where a resonant driving field and a probe field drive
different branches of transitions and a dc field is applied to
drive the transition between two excited states. The effects of
vacuum induced coherence (VIC) on the absorption spectra are
investigated. It is demonstrated that in some special cases the
VIC can lead to the depression of absorption and narrow resonance.
The origin of these features are discussed. When the pump field
and the dc field have the same intensity, it is interesting to
find that the whole absorption spectrum comes mainly from the
absorptions induced by the interferences among different
transitions between dressed states. 相似文献
14.
J.-H. Wu J.-Y. Gao 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):315-319
In order to achieve the phase-sensitive probe gain without population inversion, we investigate a three-level Λ-type atomic system driven by a coherent field and a microwave field. It is shown that, by modulating the relative phase of
applied fields, we can obtain quite high inversionless gain at different probe detunings and change the gain behavior of the
probe correspondingly. We find that amplitudes of the coherent field and the microwave field are also important factors that
can result in different gain behavior of the probe. Here, we use the microwave field to induce the quantum coherence between
the two ground levels, which is necessary for phase-sensitive effects, since it can result in the interference between two
different transition channels.
Received 20 June 2002 / Received in final form 5 December 2002 Published online 4 March 2003 相似文献
15.
G. Huang C. Hang L. Deng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):437-444
We study stable propagation of multiple shape-preserving optical
pulses in an inhomogeneously broadened multi-level atomic medium.
By analytically solving the Maxwell-Schr?dinger equations
governing the evolution of N coupled optical fields and atomic
amplitudes we show that N pulsed optical waves coupling to
(N+1)-levels can be automatically matched with the same soliton
waveform and identical yet very slow propagation velocity. Several
sets of coupled soliton solutions for two different (N+1)-level
models are given and their stability is studied by using a
numerical simulation. 相似文献
16.
Vector Cooper pairs and coherent-population-trapping-like states in ensemble of interacting fermions
A. V. Taichenachev V. I. Yudin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(3):423-433
Using the standard Hamiltonian of the BCS theory, we
show that in an ensemble of interacting fermions with the spin 1/2
there exist coherent states |NC〉, which nullify the
Hamiltonian of the interparticle interaction (scattering). These
states have an analogy with the well-known in quantum optics the
coherent population trapping (CPT) effect. The structure of these
CPT-like states corresponds to Cooper pairs with the total spin
S = 1. The found states have a huge degree of degeneracy and carry
a macroscopic magnetic moment, that allows us to construct a new
model of the magnetism connected with the delocalized electrons in
metals (conductors). A principal possibility to apply the obtained
results to the superfluid 3He is also demonstrated. 相似文献
17.
S. Gozzini S. Cartaleva A. Lucchesini C. Marinelli L. Marmugi D. Slavov T. Karaulanov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(2):153-161
In this paper we report the first experimental observation of coherent population trapping (CPT) in thermal potassium vapor
in a three levels Λ scheme. We demonstrate that K presents the advantage of a reduced modulation frequency with a large resonance
contrast (up to 40%), in comparison to similar approaches with other alkalis. We report also the first evidence of electromagnetically
induced transparency (EIT) resonances in K in the so called Hanle configuration. We tested different kinds of cells, demonstrating
strong enhancement of the resonance contrast and amplitude for antirelaxation coated and buffered cells containing K vapor:
resonance contrast up to 90% (for coated cells) and 65% (for buffered cells) is achieved with a linewidth of about 13 mG,
while under similar conditions, the EIT resonance contrast in Cs vapor buffered by Ar gas is about 1%. Such relevant improvement
is due to the reduced optical pumping in K, because of the overlapping of the hyperfine levels Doppler profiles, which does
not occur in the case of Rb and Cs vapor. For this reason, K can be considered very promising for further CPT and EIT applications,
especially for those where optical pumping losses represent a major limiting factor, such as light slowing and magnetometry. 相似文献
18.
19.
Zhuan Li Li-Ping Deng Li-Sen Xu Kaige Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(1):147-156
We study a four-level double-Λ atomic ensemble interacting with two
time-dependent signal fields and two stationary control fields. Though, in
each Λ channel, a pair of signal and control fields couple
resonantly with the two lower levels of atoms, the occurrences of
electromagnetically induced transparency (EIT) is affected by the coherence
of the four fields. In the discussion of atomic susceptibilities, we show
that the quantum coherence between the two lower levels can be either formed
or released according to the phase matching of the four fields. We analyze
the propagation equation of the two signal fields, and find two
characteristic solutions: the stationary transmission wave and the transient
decay wave. The former corresponds to a correlated EIT effect in which two
signal pulses are shape-matched. The latter is an opposite effect to the
correlated EIT in which two pulses quench simultaneously, thus named as the
correlated two-signal absorption (CTSA). We propose the CTSA condition in
correspondence with the EIT condition. The numerical simulation shows that
the double-Λ configuration is capable of manipulating synchronous
optical signals and thus provides multiplicity and versatility in quantum
information process. 相似文献
20.
F. Plastina F. Piperno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(3):407-413
We examine the decay dynamics of a free four-level system in the -V configuration. Quantum interference strongly manifests itself in this system, as can be seen by looking at the combined spectral
distribution of the two emitted photons and at the time evolution of the intermediate-level populations, whose effective lifetimes
can become very long under certain conditions for the atomic parameters. This effect is attributable to a population transfer
mechanism induced in the time evolution equations by the Fano terms, also responsible for the strong modifications of the
spectral correlation between the emitted photons which we analyze in detail. Finally, population trapping can also occur when
the two intermediate levels are degenerate.
Received: 20 October 1998 相似文献