arXiv subjects

A. M. Tumaikin

Publications and source records attributed to A. M. Tumaikin.

9 recordsLinked to original sources

arXiv2007

Laser cooling of unbound atoms in nondissipative optical lattices

The semiclassical theory of laser cooling is applied for the analysis of cooling of unbound atoms with the values of the ground and exited state angular moments 1/2 in a one-dimensional nondissipative optical lattice. We show that in the low-saturation limit with respect to the pumping field a qualitative interpretation of the cooling mechanisms can be made by the consideration of effective two-level system of the ground-state sublevels. It is clarified that in the limit of weak Raman transitions the cooling mechanism is similar to the Doppler mechanism, which is known in the theory of two-level atom. In the limit of strong Raman transitions the cooling mechanism is similar to the known Sisyphus mechanism. In the slow atom approximation the analytical expressions for the coefficients of friction, spontaneous and induced diffusion are given, and the kinetic temperature is estimated.

physics.optics↗

arXiv2006

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

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

quant-ph↗

arXiv2006

Dissipative light field as a way to create strongly localized structures for atom lithography

Generally, the conditions for deep sub-Doppler laser cooling do not match the conditions for the strong atomic localization that takes a place in deeper optical potential and, in consequence, leads to larger temperature. Moreover, for a given detuning in a deep optical potential the secular approximation which is usually used for quantum description of laser cooling becomes no more valid. Here we perform an analysis of atomic localization in optical potential based on a full quantum approach for atomic density matrix. We also show that the laser cooling in a deep far-off detuned optical potential, created by a light field with a polarization gradient, can be used as an alternative method for forming high contrast spatially localized structures of atoms for the purposes of atom lithography and atomic nanofabrication. Finally, we perform an analysis of the possible limits for the width and the contrast of localized atomic structures that can in principle be reached by this type of the light mask.

physics.atom-ph↗

arXiv2006

Features of Magneto-Optical Resonances in an Elliptically Polarized Traveling Light Wave

The parameters of nonlinear absorption magneto-optical resonances in the Hanle configuration have been studied as functions of the ellipticity of a traveling light wave. It has been found that these parameters (amplitude, width, and amplitude-to-width ratio) depend strongly on the polarization of the light wave. In particular, the resonance amplitude can increase by more than an order of magnitude when the polarization changes from linear to optimal elliptic. It has been shown that this effect is associated with the Doppler frequency shift for atoms in a gas. The theoretical results have been corroborated in experiments in Rb vapor.

quant-ph↗

arXiv2005

Coherent population trapping in quantized light field

A full quantum treatment of coherent population trapping (CPT) is given for a system of resonantly coupled atoms and electromagnetic field. We develop a regular analytical method of the construction of generalized dark states (GDS). It turns out that GDS do exist for all optical transitions $F_g\to F_e$, including bright transitions $F\to F+1$ and $F''\to F''$ with $F''$ a half-integer, for which the CPT effect is absent in a classical field. We propose an idea to use an optically thick medium with a transition $F''\to F''$ with $F'' \ge 3/2$ a half-integer as a ''quantum filter'', which transmits only a quantum light.

quant-ph↗

arXiv2004

Steady state of atoms in a resonant field with elliptical polarization

We present a complete set of analytical and invariant expressions for the steady-state density matrix of atoms in a resonant radiation field with arbitrary intensity and polarization. The field drives the closed dipole transition with arbitrary values of the angular momenta $J_{g}$ and $J_{e}$ of the ground and excited state. The steady-state density matrix is expressed in terms of spherical harmonics of a complex direction given by the field polarization vector. The generalization to the case of broad-band radiation is given. We indicate various applications of these results.

quant-ph↗

arXiv2000

Two-dimensional sideband Raman cooling and Zeeman state preparation in an optical lattice

A method of sideband Raman cooling to the vibrational ground state of the $m=0$ Zeeman sublevel in a far-detuned two-dimensional optical lattice is proposed. In our scheme, the Raman coupling between vibrational manifolds of the adjacent Zeeman sublevels is shifted to the red sideband due to the ac Stark effect induced by a weak pump field. Thus, cooling and optical pumping to $m=0$ is achieved by purely optical means with coplanar cw laser beams. The optical lattice and cooling parameters are estimated in the framework of simple theoretical models. An application of the transverse sideband cooling method to frequency standards is discussed. Coherent population trapping for the sideband Raman transitions between the degenerate vibrational levels is predicted.

physics.atom-ph↗

arXiv1999

Four-state N-atom as a simple theoretical model for electromagnetically induced absorption

A simple theoretical model describing the positive sign of subnatural-width absorption resonances in the recent experiment of Akulshin and co-workers (Phys. Rev. A, {\bf 57}, 2996 (1998)) is proposed. An analytical expression for the linear response to the weak probe field is found in the low-saturation limit with respect to the control field. It is shown that the positive sign of subnatural resonance is caused by the spontaneous transfer of the light-induced coherence from the excited level to the ground one.

physics.atom-ph↗

arXiv1999

One and two dimensional Bose-Einstein condensation of atoms in dark magneto-optical lattices

The motion of atoms in a dark magneto-optical lattice is considered. This lattice is formed by a non-uniformly polarized laser field in the presence of a static magnetic field. Cold atoms are localized in the vicinity of points where dark states are not destroyed by a magnetic field. As a result the optical interaction tends to zero (dark or gray lattices). Depending on the field configuration such a lattice can exhibit one or two-dimensional periodicity. It is shown that in 1D and 2D dark magneto-optical lattices the effects connected with the Bose-statistics of particles can be observed under the temperature $10^{-5}-10^{-6}K$ and densities $10^{11}-10^{12} cm^{-3}$, those are usual for current experiments on laser cooling.

physics.atom-ph↗