A. M. Tumaikin

Electromagnetically induced absorption and transparency in magneto-optical resonances in an elliptically polarized field

Using a 1 --> 2 transition as an analytically tractable model, we discuss in detail magneto-optical resonances of both electromagnetically induced absorption (EIA) and electromagnetically induced transparency (EIT) types in the Hanle configuration. The analysis is made for an arbitrary rate of depolarizing collisions in the excited state and an arbitrary elliptical field polarization. The obtained results clearly show that the main reason for the EIA subnatural resonance is the spontaneous transfer of anisotropy from the excited level to the ground level. In the EIA case we predict the negative structures in the absorption resonance at large field detuning. The role of the finite atom-light interaction time is briefly discussed. In addition we study nontrivial peculiarities of the resonance line shape related to the velocity spread in a gas.

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.

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).

Specific properties of the magnetooptical Hanle resonance under excitation of the transition F = 0 → F = 1 by a plane elliptically polarized light wave

The absorption of a traveling elliptically polarized wave as a function of an external static magnetic field (magnetooptical resonance) is studied theoretically. An expression for the zero-field level-crossing signal is derived for the transition F = 0 → F = 1 and it is shown that, in the presence of dephasing collisions, the resonance may have a double structure.

Kinetics of atoms in a bichromatic field

The kinetics of atoms in a bichromatic field is considered. Analytic solutions are obtained for the force, friction coefficient, and diffusion coefficient in the model of a two-level atom without limitations imposed on the intensity of light fields. This effect is observed in the domain of global minima and maxima of the optical potential (i.e., at points where the relative phase of two standing waves is ϕ = 0, π/2.

Generation of a pilot phase pulse during the propagation of slow elliptically polarized pulses in a medium under coherent population trapping

Propagation of elliptically polarized light pulses in a medium of two-level atoms with degenerate energy levels under coherent population trapping has been studied within the density-matrix formalism and reduced Maxwell’s equation. It has been shown that ellipticity pulses and the orientation angle of the polarization ellipse move with a deceleration. The analytical expression for the group velocity of an arbitrary J → J dark transition (J is an integer) has been derived. In addition, a previously unknown effect of forced phase modulation under the variation of the spatial orientation of the polarization ellipse has been discovered. This phase modulation includes a pilot pulse passing through the medium at the speed of light in vacuum and a slow pulse moving synchronously with the pulse of the orientation angle.

Steady-state light-induced forces in atomic nanolithography

An analysis of general characteristics of light-induced forces is presented for arbitrary monochromatic masks in which optical pumping of atoms and spontaneous emission play an important role. Dependence of regions of localization on detuning and ellipticity is determined for cyclic transitions of two types: J å J with half-integer J and J å J + 1 with arbitrary J. Numerical simulations of atomic beam focusing with one-and two-dimensional light masks show that spatial atom distributions with narrow features and high contrast can be formed in dissipative masks. In particular, spherical aberration is substantially reduced when the pumping field is tuned to a J å J + 1 transition with large J in lin ∼ lin configuration as compared to nondissipative masks.