Inversionless superradiance of an ensemble of three-level atoms in a high-Q cavity

We analyze the possibility of superradiance in an ensemble of three-level atoms in the absence of population inversion. We show that in the case of a Λ configuration of the active transitions this effect can occur for an initially coherent superposition of the states of the lower doublet. We also study how splitting of the lower levels influences this effect and discuss ways of creating low-frequency coherence. Zh. éksp. Teor. Fiz. 115, 505–520 (February 1999)     

Superradiance and superradiance without inversion of a thin layer of three-level atoms: The consideration of the sample extent

The effect of the sample extent in the process of superradiance and superradiance without population inversion of a thin (L ≤ λ) layer of three-level atoms (Λ-configuration of working transitions) is investigated. The limits of applicability of the spatially homogeneous approximation are determined. The consideration of the extent is shown to introduce new effects into the kinetics of populations and the field.     

Resonant interaction of light with a thin film of three-level atoms

Refraction of a double-frequency optical pulse at the interface between two linear dielectrics containing a thin film of resonant atoms is considered. The dynamics of the system is treated based on the model of three-level atoms with the V-type energy diagram. Refraction of short and long (compared with the Rabi oscillation period) pulses is analyzed with allowance for local-field effects. In both cases, the shape of the pulse corresponding to one carrier wave frequency is shown to depend on the energy of the pulse with the other carrier wave frequency. In particular, both the frequency and the depth of the amplitude modulation arising in the refracted pulse are changed.     

Autler-Townes doublet in the absorption spectra for the transition between excited states of cold cesium atoms

Autler-Townes splitting in absorption spectra of the excited states 6 2 P 3/2-8 2 S 1/2 of cold cesium atoms confined in a magneto-optical trap has been observed.Experimental data of the Autler-Townes splitting fit well to the dressed-atom theory,by which the fact of the cold atoms dressed by cooling/trapping laser beams is revealed.The results of the theoretical fitting with experiment not only told us the effective Rabi frequency cold atoms experienced,but also could be used for measuring the probability amplitudes of the dressed states.     

Probing the thermal atoms of a Bose gas through Raman transition

We explore the many body physics of a Bose condensed atom gas at finite temperature through the Raman transition between two hyperfine levels. Unlike the Bragg scattering where the phonon-like nature of the collective excitations has been observed, a different branch of thermal atom excitation is found theoretically in the Raman scattering. This excitation is predicted in the generalized random phase approximation (GRPA) and has a gapped and parabolic dispersion relation. The gap energy results from the exchange interaction and is released during the Raman transition. The scattering rate is determined versus the transition frequency ω and the transferred momentum q and shows the corresponding resonance around this gap. Nevertheless, the Raman scattering process is attenuated by the superfluid part of the gas. The macroscopic wave function of the condensate deforms its shape in order to screen locally the external potential displayed by the Raman light beams. This screening is total for a condensed atom transition in order to prevent the condensate from incoherent scattering. The experimental observation of this result would explain some of the reasons why asuperfluid condensate moves coherentlywithout any friction with its surrounding.     

Effect of the near-lying level on the kinetics of the field of superradiance of a thin layer

The effect of the local field on the competition of transitions in the superradiance of an incompletely excited thin layer of three-level atoms (Λ-diagram of working transitions) is studied. Analysis is made for the conditions when one of the sublevels of the lower doublet is initially unpopulated. For an initially unpopulated upper sublevel of the lower doublet, a new superradiance regime is found.     

利用受激Raman跃迁制备的原子激光的相干性

研究了利用原子玻色-爱因斯坦凝聚体与光相互作用产生受激Raman跃迁制备的原子激光二阶相干性质。结果表明,这种原子激光是反聚束的,在一定条件下,是二阶相干的。     

Coherent population trapping in an ensemble of three-level atoms in the presence of cooperative relaxation

We derive equations that describe the dynamics of three-level atoms with a cascade system of levels interacting with two resonant coherent fields in conditions where cooperative relaxation dominates over incoherent spontaneous emission. We calculate the temporal dynamics of the values of the atomic populations. The possibility of coherent population trapping in the presence of the cooperative decay is established. Finally, we calculate the averaged population of the intermediate level as a function of detuning for different values of the coupling constant. Zh. éksp. Teor. Fiz. 112, 869–876 (September 1997)     

利用受激Raman跃迁制备的原子激光的相干性

研究了利用原子玻色-爱因斯坦凝聚体与制备的原子激光的二阶相干性质. 结果表明,这种原子激光是反聚束的,在一定条件下,是二阶相干的.     

Effect of the near-lying level on the kinetics of populations in the superradiance of a thin layer: Local-field regime

The effect of the local field on the competition of transitions in the superradiance of an incompletely excited thin layer of three-level atoms Λ-diagram of working transitions) is studied. The analysis made proves that the upper sublevel of the lower doublet is initially unpopulated. It is shown that the Raman transition, in the local-field regime, is ahead of the development of the superradiance pulse and causes the transfer of populations between sublevels of the lower doublet.     

Λ型三能级原子系统中Raman跃迁增强的Kerr非线性效应

在理论上研究了Λ型三能级原子系统Raman跃迁中的线性和非线性极化率.研究表明: Raman 跃迁中，如果原子完全被抽运到与控制光作用的基态时，将导致介质对探针光的线性极化率 为零，而三阶非线性极化率不为零.通过减小原子两基态间的无辐射衰减速率γ_{12，可以极大地增强交叉Kerr非线性效应.}     

Raman spectrum of a layer or thin slice at a solid interface

If we use an experimental device with one plane parallel dielectric film and one plane parallel metallic film between two transparent media, we can amplify the luminous energy (homogeneous or inhomogeneous waves) in the dielectric medium, and obtain the Raman spectrum of the film or of a thin slice of 1000 Å thickness.     

Manipulating the phase of a single-mode micromaser by polarized three-level atoms

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.     

Control of the switch between optical multistability and bistability in three-level V-type atoms

We theoretically investigated a hybrid absorptive-dispersive optical bistability and multistability behaviour in a three-level V-type system using a microwave field driving a hyperfine transition between two upper excited states inside a unidirectional ring cavity. We find that the intensity and the frequency detuning of the coupling field as well as the intensity of the microwave field can affect the OM behaviour dramatically, which can be used to control the transition from OM to OB or vice versa without need to resort the effect of the quantum interference. The effects of the phase, the quantum interference and the atomic cooperation parameter on the OM are also studied. Our scheme may be used for building more efficient all-optical switches and logic-gate devices for optical computing and quantum information processing.     

原子间相互作用对V型三能级原子激光压缩性质的影响

研究了V型三能级原子玻色-爱因斯坦凝聚体与双模压缩相干态光场相互作用系统中原子激光的两个正交分量的压缩性质,并与三型三能级原子玻色-爱因斯坦凝聚体和双摸压缩相干态相互作用系中原子激光的压缩作了比较.结果表明:压缩相干态光场的初始压缩因子和凝聚体中原子间的相互作用强度对原子激光的两个正交分量的压缩有明显的影响,随光场压缩因子增大原子激光的压缩深度增加,而随原子间相互作用变强,对原子激光的正交分量的压缩的影响变浅.     

Dynamics of the collective spontaneous emission of two three-level atoms in a cavity

Based on the master equation for the density matrix, the collective spontaneous emission of two A-type three-level atoms interacting with two modes of a quantum electromagnetic field in a finite-Q cavity is studied. The evolution of the emission intensity for each mode is found for the case where both atoms are initially in the excited state.     

Self-consistent solutions of the problem of the interaction of a two-frequency field with a system of three-level atoms in the form of a phase-modulated simulton and a Raman soliton

This paper discusses features of the interaction of a system of three-level atoms with a bichromatic electromagnetic field. Steady-state solutions are found in the form of unimodal and nonunimodal solitary waves corresponding to a pair of pulses in the form of a simulton or a Raman soliton. An analytic form of the solutions is found, corresponding to a phase-modulated simulton and a Raman soliton. The conditions are determined for exciting them. The resulting solutions are of interest from the standpoint of the mechanism for forming the two-frequency coupled excitations observed in various experiments. Zh. éksp. Teor. Fiz. 113, 747–762 (February 1998)