O. N. Prudnikov

Basis of polarization-dressed states of an atom in an elliptically polarized resonant field

A basis of polarization-dressed states is proposed for atomic energy levels degenerate in the total angular momentum projections in the case of interaction with elliptically polarized light. It is shown that instead of selection rules for the magnetic quantum number, the interaction in this basis can be presented as the sum of direct transitions between corresponding pairs of polarization-dressed states of the upper and lower levels. The explicit form of the basis is derived for ten possible combinations of dipole transitions between energy levels with angular momenta J = 0, 1/2, 1, 3/2, and 2. The problem of Rabi oscillations in such a system is considered as an application.

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.

Dissipative Light Mask Generated by a Nonuniformly Polarized Field for Atomic Lithography

The localization of atoms in a deep optical potential is analyzed in the framework of the completely quantum description of the motion of the atoms using the kinetic equation for the density matrix. It is shown that the laser cooling of the neutral atoms in the deep optical potential at a relatively large detuning of the light field from resonance can be used as a method for forming spatially localized atomic structures with a high contrast for atomic lithography. This method is alternative to nondissipative light masks.

The light pressure force and the friction and diffusion coefficients for atoms in a resonant nonuniformly polarized laser field

The motion of slow atoms with degenerate energy levels in a resonant, nonuniformly polarized laser field is described by the Fokker-Planck equation for the atomic distribution function in phase space in terms of the semiclassical approach. Field gradient expansions are used for the spatially nonuniform coefficients of the equation. For closed atomic transitions Jg=J→Je=J+1 (Jg and Je are the total angular momenta of the ground and excited states, respectively), new analytical results are presented for the light pressure force and the friction and diffusion coefficients in momentum space. These results allow the kinetic effects (laser cooling, localization in optical potential wells, etc.) in a field of arbitrary one-, two-, or three-dimensional configuration to be investigated. In several cases, the new contributions to the friction coefficient are interpreted qualitatively.

Three-dimensional theory of the magneto-optical trap

The kinetics of atoms in a three-dimensional magneto-optical trap (MOT) is considered. A three-dimensional MOT model has been constructed for an atom with the optical transition Jg = 0 → Je = 1 (Jg, e is the total angular momentum in the ground and excited states) in the semiclassical approximation by taking into account the influence of the relative phases of light fields on the kinetics of atoms. We show that the influence of the relative phases can be neglected only in the limit of low light field intensities. Generally, the choice of relative phases can have a strong influence on the kinetics of atoms in a MOT.

Polarization-gradient laser cooling as a way to create strongly localized structures for atom lithography

Generally, conditions for deep sub-Doppler laser cooling do not match conditions for strong atomic localization, that takes place in a deeper optical potential and leads to higher temperature. Moreover, for a given detuning in a deep optical potential the secular approximation, which is frequently used for a quantum description of laser cooling, fails. Here we investigate the atomic localization in optical potential, using a full quantum approach for atomic density matrix beyond the secular approximation. It is shown that laser cooling in a deep optical potential, created by a light field with polarization gradients, can be used as an alternative method for the formation of high contrast spatially localized structures of atoms for the purposes of atom lithography and atomic nanofabrication. Finally, we analyze possible limits for the width and contrast of localized atomic structures that can be reached in this type of light mask.

Study of laser cooling in deep optical lattice: two-level quantum model

We study a possibility of laser cooling of Mg atoms in deep optical lattice formed by intense off-resonant laser field in a presence of cooling field resonant to narrow (3s3s) S0 → (3s3p) P1 (λ = 457 nm) optical transition. For description of laser cooling with taking into account quantum recoil effects we consider two quantum models. The first one is based on direct numerical solution of quantum kinetic equation for atom density matrix and the second one is simplified model based on decomposition of atom density matrix over vibration states in the lattice wells. We search cooling field intensity and detuning for minimum cooling energy and fast laser cooling. Pacs 32.80.Pj, 42.50.Vk, 37.10.Jk,37.10.De

Deep laser cooling of Mg in dipole trap for frequency standard

We study deep laser cooling of ²⁴Mg atoms in dipole optical trap with pumping field resonant to narrow (3s3s)¹S<inf>0</inf> → (3s3p)³P<inf>1</inf> (λ, = 457nm) optical transition. We consider two quantum models: the first one based on direct numerical solution of quantum kinetic equation for atom density matrix and the second one is simplified model based on decomposition of atom density matrix on vibration states in dipole trap. Both models shows close results. We search pumping field intensity and detuning for minimum laser cooling energy of atoms and fast laser cooling.

New approaches in deep laser cooling of magnesium atoms for quantum metrology

We theoretically describe two approaches aimed at solving the existing problem of deep laser cooling of neutral magnesium atoms. The first approach based on using optical molasses with orthogonal linear polarizations of light waves, while the second one implies exploiting “nonstandard” magneto-optical trap composed of elliptically polarized (in general) light waves. The widely used semiclassical approximation based on the Fokker-Planck equation as well as the full quantum treatment (with full account of the recoil effect) are applied for theoretical analysis. The results are crucial for metrological and some other applications of cold atoms.

Quantum theory of the laser cooling of two-level atoms in the field of a standing light wave: A statistical description of dynamics

The time required for establishing a stationary distribution of two-level atoms in the field of a onedimensional standing light wave is studied with full allowance for recoil effects and spatial trapping. The dependences of the cooling time on the problem parameters are obtained, and their considerable deviance from semiclassical predictions is demonstrated.