A. V. Taichenachev

Steady state of a low-density ensemble of atoms in a monochromatic field taking into account recoil effects

A method has been developed for obtaining the steady-state solution of a quantum kinetic equation for the atomic density matrix in an arbitrarily polarized monochromatic field with the complete inclusion of recoil effects and degeneracy of atomic levels in the projection of the angular momentum. This method makes it possible to obtain the most general solution beyond the previously accepted approximations (semiclassical approximation, secular approximation, etc.). In particular, it has been shown that the laser cooling temperature is a function of not only the depth of the optical potential (as was previously thought), but also the mass of an atom.

Effect of the polarization of counterpropagating light waves on nonlinear resonances of the electromagnetically induced transparency and absorption in the Hanle configuration

A polarization method has been proposed for transforming the nonlinear electromagnetically induced transparency resonance into the electromagnetically induced absorption resonance (and vice versa) in the Hanle configuration in the field of counterpropagating waves. Numerical calculations have been performed for the Fg = 2 → Fe = 1 and Fg = 2 → Fe = 3 transitions in the 87Rb atom. The qualitative analysis of the effect has been performed for the three-level Λ scheme of the atomic energy levels. The main theoretical conclusions are in qualitative agreement with our experimental data for 87Rb. The results can be applied in magnetometry and nonlinear optics.

Kinetics of atoms in the field produced by elliptically polarized waves

The kinetics of atoms with degenerate energy levels in the field produced by elliptically polarized waves is considered in the semiclassical approximation. Analytic expressions for the force acting on an atom and for the diffusion coefficient in the momentum space are derived for the optical transition Jg=1/2→Je = 1/2 in the slow atom approximation. These expressions are valid for an arbitrary one-dimensional configuration of the light field and for an arbitrary intensity. The peculiarities of the atomic kinetics are investigated in detail; these peculiarities are associated with ellipticity of light waves and are absent in particular configurations formed by circularly or linearly polarized waves, which were considered earlier.

Electromagnetically induced absorption and electromagnetically induced transparency for optical transitions Fg → Fe in the field of elliptically polarized waves

Nonlinear laser spectroscopy is considered in the scheme of two collinear waves with arbitrary elliptical polarizations. Emphasis is placed on investigating the nonlinear corrections in the absorption spectrum of one of the waves. The spontaneous transfer of low-frequency Zeeman coherence is shown to affect the sign of the subnatural-width resonance. For a closed transition, the direction of the resonance profile has been found to depend only on the angular momenta Fe and Fg. On this basis, a classification has been developed for various transitions by the direction of the subnatural-width resonance profile.

Dual structure of saturated absorption resonance at an open atomic transition

Experiments on open transitions of the D1 line of alkali metals (Cs and Rb isotopes) reveal the dual structure of saturated absorption resonance in the signal of a high-intensity optical wave in the presence of a low-intensity counterpropagating wave. Theoretical analysis shows that the observed shape of the resonance is associated with the openness of the atomic transition as well as with the Doppler effect for atoms in a gas. The results are of general physical significance for nonlinear spectroscopy and can also find application in metrology (frequency and time standards on open transitions).

Study of field shifts of Ramsey resonances on ultracold atoms and ions

The effect of the finite laser radiation line width and spontaneous relaxation of levels on the efficiency of the suppression of the field shift of the central resonance for the generalized Ramsey scheme with pulses of different lengths and with a phase jump in the second pulse has been considered. The optimal parameters of the scheme corresponding to the minimum frequency shift and maximum amplitude of the resonance have been determined.

Generalized ramsey scheme for precision spectroscopy of ultracold atoms and ions: Inclusion of a finite laser line width and spontaneous relaxation of the atomic levels

Ramsey schemes with pulses of different lengths and with a composite pulse have been analyzed taking into account a finite width of the laser line and spontaneous relaxation of atomic levels. The optimal parameters of pulses corresponding to the maximum suppression of the excitation-related shift and the maximum resonance amplitude have been found for both schemes. According to the numerical results, spontaneous relaxation of the atomic levels and a finite width of the laser line must be taken into account in the calculation of the optimal parameters of the excitation pulses. The Ramsey scheme with a composite pulse is less sensitive to fluctuations of the Rabi frequency than the scheme with pulses of different lengths.

Anomalous spatial concentration of atoms in the field of a standing light wave

The stationary momentum and coordinate distributions of two-level atoms in the field of a one-dimensional standing light wave have been studied. A qualitatively new effect—the predominant concentration of atoms outside of the minima of the optical potential—has been detected in the regime of moderate saturation of an atomic transition and red frequency detuning. This effect has been qualitatively interpreted. Calculations have been performed using the quantum kinetic equation for the atomic density matrix with the complete inclusion of recoil and localization effects in an arbitrary-intensity light field. In addition to theoretical significance, the results can be useful for atomic nanolithography and frequency standards based on optical gratings.

Shift and asymmetry of the saturated absorption resonance in the field of counterpropagating elliptically polarized waves

The saturated absorption resonance in an atomic gas in the field of counterpropagating light waves with an arbitrary elliptical polarization is investigated. A conclusion about the peculiarities of the resonance shape is drawn from a general analysis of the symmetry of the problem. In particular, a new effect has been found: the polarization parameters of the light waves can lead to an asymmetry and shift of the resonance. These conclusions are corroborated by an approximate analytical solution for the Fg = 1 → Fe = 2 transition and by numerical calculations. Apart from their fundamental importance, the results obtained can have important applications in metrology (frequency and time standards).

Magneto-optical trap formed by elliptically polarised light waves for Mg atoms

We consider a magneto-optical trap (MOT) formed by elliptically polarised waves for 24Mg atoms on a closed optical 3P2 → 3D3 (λ = 383.8 nm) transition in the e – θ – configuration of the field. Compared with a known MOT formed by circularly polarised waves (σ+ – σ- configuration), the suggested configuration of the trap formed by fields of e – θ – configuration allows deeper sub-Doppler cooling of trapped 24Mg atoms, which cannot be implemented in a conventional trap formed by fields of σ+ – σ- configuration.