We have studied the propagation of light in M- and W-systems, and have demonstrated the possibility of such propagation with nonlinear group velocity being either less than (slow light) or greater than (superluminal propagation) of the speed of light in vacuum without being distorted.
In this paper we have demonstrated coherent population trapping and Rydberg state excitation in the five level media. We have analysed the influence of non zero multiphoton detunings and the self-phase modulation on these processes.
We examine in detail the cyclic adiabatic population transfer methods for five-level diagrams in order to construct a four-bit universal reversible logic gate. We show that under certain conditions and sequence of turning on and off the laser pulses a five-level system may be reduced to an effective Λ-diagram.
Possibility of coherent control of spontaneous emission from four- and five-level systems in the laser radiation
field is studied. The four-level system consists of two levels resonantly driven by laser radiation where either of levels
may decay to a separate level. For such a system we show that the presence of the second decay channel may deteriorate
the destructive interference occurring because of Autler-Townes effect in case of one decay channel. The five-level
system represents two two-level resonantly driven systems with the upper levels decaying to a common level. For this
case, the interference between the two decay channels is partially or completely destructive or constructive depending on
the initial conditions and on the mutual orientation of the transition dipole moments. It is shown that population transfer
takes place by the same quantum vacuum via spontaneous emission. The populations are shown to have damping
Collisions of atoms with formation of Feshbach resonances in the presence of laser field are considered. The elastic and
inelastic scattering cross sections are calculated. The laser field leads to second resonance in elastic scattering,
broadening of resonances, and arising of interference between resonant and potential scattering. The effects associated
with interference of the two channels of decay of bound system of two atoms (a molecule) in laser field are studied. It is
shown that if the energy equals that of the lower stable Stark-shifted level plus the energy of two photons, the resonance
is quenched. It is also shown that with the increase in two-photon effective interaction the pattern of resonance scattering
The dynamics of interaction of laser radiation resonant with the transitions of D<sub>2</sub> line in atomic Cs<sup>133</sup> in the presence of
an external magnetic field is studied. Populations of levels and dynamics of resonant fluorescence at scanning frequency
of the laser radiation with linear and circular polarizations are considered.