Showing papers on "Atomic coherence published in 1995"
TL;DR: In this paper, an electromagnetically induced transparency is observed at one arm of a three-level ε-Lambda-type system in a rubidium D1 line (794.8 nm) with an 85% reduction in absorption, when a pumping field is present at the other arm.
Abstract: An electromagnetically induced transparency is observed at one arm of a three-level \ensuremath{\Lambda}-type system in a rubidium D1 line (794.8 nm) with an 85% reduction in absorption, when a pumping field is present at the other arm. This reduction in absorption for the weak probe field is due to the atomic coherence produced by the strong pumping field. This experiment is done in a Rb vapor cell at room temperature with cw diode lasers for both pumping and probe beams in a Doppler-free configuration. A simple theoretical treatment including Doppler broadening is in good qualitative agreement with the experimental measurement.
175 citations
TL;DR: Sodium atoms have been stored in a blue-detuned dipole trap based on sheets of argon ion laser light which support against gravity, resulting in a large reduction in the perturbation of the atomic levels due to the trapping potential.
Abstract: Sodium atoms have been stored in a blue-detuned dipole trap based on sheets of argon ion laser light which support against gravity. In this trap, the atoms spend most of their time in free fall, resulting in a large reduction in the perturbation of the atomic levels due to the trapping potential. This reduction enabled us to probe the ground state hyperfine splitting with a measurement time of 4 s, yielding a linewidth of 0.125 Hz and a Ramsey fringe contrast of 43%. The coherence time was $\ensuremath{\sim}$300 times longer than achieved in a red-detuned Nd:YAG laser dipole trap with comparable depth.
157 citations
TL;DR: The transient behavior of an electromagnetically induced transparency in three-level atomic systems is described and Transient gain without population inversion and enhancement of dispersion are discussed.
Abstract: We describe the transient behavior of an electromagnetically induced transparency in three-level atomic systems. When the coupling f ield is switched on, the absorption for the probe field is oscillatorily damped to its new steady-state (transparent) value. Transient gain without population inversion and enhancement of dispersion are discussed. A realistic system for experimental testing of these effects is presented.
90 citations
TL;DR: The Rabi oscillation frequency and the collapse and revival times of the atomic coherence are found to have strikingly different photon-intensity dependence than those found previously.
Abstract: Starting from a three-level atom coupled to two modes of radiation field, we derive a Raman-coupled Hamiltonian by a unitary transformation, evaluated perturbatively in coupling constants The Rabi oscillation frequency and the collapse and revival times of the atomic coherence are found to have strikingly different photon-intensity dependence than those found previously
75 citations
TL;DR: A 64.4% reduction in absorption at the rubidium D2 line is observed when a pumping field at 775.8 nm is tuned on resonance to the transition between the excited states 5-5/2.
Abstract: A 64.4% reduction in absorption at the rubidium D2 line is observed when a pumping field at 775.8 nm is tuned on resonance to the transition between the excited states 5${\mathit{P}}_{3/2}$ and 5${\mathit{D}}_{5/2}$. As the pumping field is tuned off resonance, an absorption peak appears at the side of the Doppler-broadened D2 line. This modification in absorption is related to pumping-induced atomic coherence in this three-level ladder-type system. This experiment is done in a Rb vapor cell at room temperature and with cw diode lasers for both pumping and probe beams in a Doppler-free configuration.
51 citations
45 citations
TL;DR: In this paper, the hyperfine structures of highly-excited atomic states can be determined by electromagnetically-induced transparency experiment based on atomic coherence, and a theoretical model is presented and is in good agreement with the experimental results.
23 citations
TL;DR: In this article, the effect of increasing buffer gas pressure on optical pumping and coherent population trapping was investigated and it was shown that decreasing atomic coherence with increasing buffer pressure enhances the effect.
Abstract: In the early experiments on optical pumping and coherent population trapping (``dark resonances'') increasing buffer gas pressure enhances the effect. In our recent lasing-without-inversion experiments, based on population trapping, we find the opposite behavior, namely, decreasing atomic coherence with increasing buffer gas pressure. We provide a theoretical explanation of this result in agreement with experiment.
19 citations
TL;DR: In this paper, the dynamics induced by a seed pulse, resonant with the upper to intermediate levels transition, propagating in an ensemble of homogeneously broadened three-level atomic systems initially pumped by a two-photon excitation is analyzed in the presence of a very weak cw background field that is resonant at intermediate to lower levels transition.
6 citations
TL;DR: In this article, a new approach to the experimental search for P and T violating permanent electric dipole moments (EDMs) in atoms is proposed, where high dispersion of a phase coherent atomic medium at a point of electromagnetically induced transparency is used to detect linear Stark-shifts associated with an atomic EDM in a highly sensitive interferometric measurement.
Abstract: A new approach to the experimental search for P and T violating permanent electric dipole moments (EDMs) in atoms is proposed. The high dispersion of a phase coherent atomic medium at a point of electromagnetically induced transparency is used to detect linear Stark-shifts associated with an atomic EDM in a highly sensitive interferometric measurement. Possible noise sources are analysed and estimates are given for the device sensitivity.
5 citations
TL;DR: The master equations for the fields in the one-mode {Lambda}-type micromaser and laser with injected atoms in a superposition of their states are derived and the generation of field states with sub-Poissonian photon statistics is possible in the micromasers without the need for a population inversion.
Abstract: We derive the master equations for the fields in the one-mode {Lambda}-type micromaser and laser with injected atoms in a superposition of their states. In terms of effective parameters, these equations are equivalent to those for a two-level micromaser and laser. The interference terms in the master equations may cancel the absorption terms independent of statistical properties of the field. Due to the atomic coherence between the two degenerate lower levels, the generation of field states with sub-Poissonian photon statistics is possible in the micromaser without the need for a population inversion. If an equivalent level system is used in a laser operating without population inversion it can produce field states with Poisson distributions of the photon number.
TL;DR: In this article, a full quantum treatment is given of suppression of absorption and lasing without inversion in a ∧-type three-level atom induced by a strong driving field resonant with the two lower levels.
Abstract: A full quantum treatment is given of suppression of absorption and lasing without inversion in a ∧-type three-level atom induced by a strong driving field resonant with the two lower levels. The nature of the quantum interference leading to the suppression of absorption and lasing without inversion and its relation to the initial state preparation are studied. Particular attention is given to the effects that arise specifically from the quantum nature of the driving field. It is shown that, because of the distinguishability of the states of the driving field that have different photon numbers, destructive interference is confined to occur within a finite region of the photon number space. A complete cancellation of absorption predicted in the semiclassical theory should thus be regarded as resulting from an ideal behavior achieved only in the classical limit when the driving field is given as a strong coherent field.
TL;DR: In this article, both stationary and time-dependent regimes of operation, instabilities, and phase squeezing are investigated in the off-resonant correlated-spontaneous-emission laser by numerical calculation.
Abstract: Both stationary and time-dependent regimes of operation, instabilities, and phase squeezing are investigated in the off-resonant two-photon correlated-spontaneous-emission laser by numerical calculation. Initial atomic coherence plays an essential role in lasing without population inversion, phase locking, and phase noise squeezing in the system. Under certain conditions, in the inverted and noninverted regimes alike, the output intensity exhibits bistable behaviors against the initial atomic coherence. Depending on the parameters, the whole or a portion of the upper or lower branch gives stable operations. In the inverted regime, even tristable behavior can be found in a narrow range of parameters. The field evolution and dynamics are studied. Furthermore, phase noise reduction near bistable areas is also investigated. In addition to the lower branch, where from previous studies, it has been known to exist, phase squeezing is also found on the upper branch both with and without population inversion, thus generating a bright source of phase noise squeezed light.
TL;DR: In this paper, the authors demonstrate the effect of atomic coherence on the generic example of two lossless micromasers coupled in series by a common pump beam of excited two-level atoms.
Abstract: The authors demonstrate the effect of atomic coherence on the generic example of two lossless micromasers coupled in series by a common pump beam of excited two-level atoms. The fields are studied via conditional measurements on the final state of the atoms. They consider the two simplest sequences: in the energy preserving (transferring) scheme they require each atom to be detected in its upper (lower) state. Due to the two paths that the atoms can follow to reach the same final state correlation between the two macroscopically separated fields can arise. The authors discuss a scheme which leads to the generation of entangled trapping states of the two fields of the form, mod n,n+M)+or- mod n+M,n), starting from number states mod n, n). Starting from initial coherent states arbitrary steady-state superpositions of the two fields can be generated by switching from the energy transferring to the preserving scheme at an optimum number of atoms. In the absence of dissipations, both methods can produce steady-state coherent superpositions of arbitrary number states of two macroscopically separated fields (nonlocal 'Schrodinger-cats'). A scheme is discussed where entanglement can be transferred from the fields to two atomic beams. Finally, the authors briefly discuss the effect of injected atomic coherence on lasers.
TL;DR: In this paper, the authors presented a numerical study of the regularly injected one-atom maser in the high-flux regime, namely, when the time spacing between two consecutive injected atoms is comparable with the atom-field interaction time.
Abstract: We present a numerical study of the regularly injected one-atom maser in the high-flux regime, namely, when the time spacing between two consecutive injected atoms is comparable with the atom–field interaction time Gain and losses are treated simultaneously in a general master equation that takes into account atomic incoherent decay At stroboscopic times the dynamics of photon-number probability distribution is given by a suitably reduced Green operator, which has the form of a Markoff matrix We perform a spectral analysis of the Green operator, showing the influence of photon traps on the eigenvalues A comparison with the opposite case of Poissonian injection and low flux is given for a wide range of the pumping parameter θ Regular injection leads to larger gain than Poissonian, but for high values of θ the opposite result can be found Anomalous behaviors occur in which the normalized field fluctuations are increased by regularization of pumping and decreased by atomic decay: these features confirm similar anomalies found by other authors and are ascribed to the occurrence of nonclassical multiple-peak photon distributions and to different responses of the peaks to dissipation and gain Atomic elastic collisions destroy any signature of trapping states on the stationary field A comparison with a previously studied semiclassical model is given
TL;DR: A unique atomic interferometer employing collective radiation from the atoms to measure the atomic phase is demonstrated and the 180° phase shift of a J = 0 atomic state that undergoes a 2π-rotation of the Bloch vector or a two-level optical transition is measured.
Abstract: We demonstrate a unique atomic interferometer employing collective radiation from the atoms to measure the atomic phase. Atomic coherence is detected by interference of a continuous free-induction decay field and a continuous photon-echo field that originate in spatially separated regions of an atomic beam. Using this system, we measure the 180° phase shift of a J = 0 atomic state that undergoes a 2π-rotation of the Bloch vector or a two-level optical transition.
TL;DR: In this paper, two micromaser coupled in series by sharing a common pumping atomic beam were considered and the correlation between the two spatially separated fields arises as atomic coherence is transferred from the first to the second cavity.
Abstract: We consider two micromasers coupled in series by sharing a common pumping atomic beam Quantum correlation between the two spatially separated fields arises as atomic coherence is transferred from the first to the second cavity