T. Ya. Karagodova

Dispersion of populations of a multilevel system in a strong field of laser emission and a magnetic field

Using the theory and the calculation method developed previously, numerical experiments on the study of dispersion of populations of a multilevel atomic system in strong fields of laser radiation in resonance with adjacent transitions and in a constant magnetic field are conducted. The effect of the magnetic field strength on the character of coherent population trapping in a multilevel system is studied. It is shown that the effect, depending on the magnetic field strength, may be observed for both and for one of the magnetic sublevels of the level that is doubly degenerate in the magnetic quantum number, for which resonance fluorescence is studied. The possibility of obtaining population inversion for magnetic sublevels in the excited state of a multilevel atom under an appropriate choice of parameters is demonstrated.

The effect of experimental geometry and initial conditions on the shape of coherent population trapping resonances on the fine structure levels of thallium atoms

Specific features of the coherent population trapping effect are considered in the generalized Λ system whose lower levels are the magnetic sublevels of the fine structure levels of the thallium atom. Numerical experiments were performed aimed at examination of the coherent population trapping for the case of nontrivial, but feasible, initial populations of the upper metastable fine structure level. Such populations may be obtained, for example, due to the photodissociation of TlBr molecules. The possibility of reducing the number of resonances of the coherent population trapping in a multilevel system, which may be useful for high-resolution spectroscopy, is demonstrated. It is shown that the magnitude and shape of the resonances can be controlled by varying the orientation of the polarization vectors of the light field components with respect to each other and to a magnetic field. In addition, studying the shape of the coherent population trapping resonances for the atoms obtained by photodissociation of molecules may provide information about these molecules.

Faraday effect in alkali-metal vapors in a strong bichromatic field of laser light

Results of a numerical study of the Faraday effect arising upon propagation of the light beams with the frequencies ωL1 (resonant to the nS1/2-nP1/2, 3/2 transitions) and ωL2 (resonant to the nP1/2, 3/2-(n+2)S1/2 transitions) through alkali-metal vapors are presented. Characteristics of the magneto-optical rotation spectra at each of the frequencies are strongly affected by the second intense radiation field resonant to the adjacent transition. When the atoms interact with two strong light waves, resonant to adjacent transitions, and with a magnetic field, the shape of the Faraday rotation spectra depends on the energy shifts of the atomic states that arise due to the dynamic Stark effect and the Zeeman effect (the Paschen-Back or an intermediate-type effect), as well as due to the difference of populations of these states caused by the interaction of the atoms with the fields. The results obtained show that in the frequency selection method, based on the resonance Faraday effect, the frequency of the generated narrow-band beam can be tuned by the intensity of the strong wave, resonant to the transition between the excited states.

Features of two-photon resonances of nonlinear magnetooptical rotation of the plane of polarization for the initial population of fine-structure levels in alkali atoms

The features of nonlinear magnetooptical effects of fine-structure levels of an alkali atom, including effects in strong magnetic fields, as well as under conditions of two-photon resonance, are considered. The spectra of magnetooptical rotation and of magnetic circular dichroism have been obtained for the first time for the nontrivial initial population of magnetic sublevels of excited electronic states of an alkali atom, as well as under conditions of two-photon resonance. The decrease in the amplitude of resonances of initially populated fine-structure levels is explained by population transfer, taking place in strong fields. This transfer affects the rotation of the plane of polarization. The lower the initial population, the more pronounced the population transfer. Numerical experiments have shown that analysis of the resonance shapes in the spectra of magnetooptical rotation can yield information on the initial population of magnetic sublevels of excited electronic states of atoms.

Influence of the polarization of radiation on the shape of resonances of coherent population trapping on fine-structure levels

The dependence of the shape of resonances of coherent population trapping (CPT) on magnetic sublevels of thallium atoms, forming a generalized Λ-system with the magnetic sublevels of the fine-structure levels as lower ones, on the polarization of the radiation fields has been numerically studied. The cases of linear, elliptical, and circular polarizations have been considered. The shape and the number of CPT resonances for different polarizations have been compared. It has been concluded that the electromagnetically induced transparency can be changed by changing the polarization properties of the laser radiation. The possibility to decrease the number of observed resonances may be useful in high-resolution spectroscopy.

The influence of the orientation and strength of a magnetic field on the coherent population trapping in the Λ system

The influence of the orientation and strength of a magnetic field on the dynamics and dispersion of the populations of the multilevel Λ system upon spontaneous decay into thermostat levels is considered. The radiation field consists of two components and is specified by the vector-potential in the electric dipole approximation. From the solution of the Schödinger equation for a system consisting of an atom in a magnetic field + radiation field, the probability of populating a common level for the generalized Λ system is determined in the resonance approximation. The calculation of the dynamics and dispersion of the populations demonstrates their dependence on the orientation of the magnetic field vector with respect to the light field polarization vector and on the relationship between the magnetic field strength and radiation field intensities. The coherent population trapping occurs only in the case when Rabi frequencies either exceed or are comparable to the Zeeman splitting of magnetic sublevels. By varying the orientation of the magnetic field, it is possible to change the dynamics and dispersion of the populations, thus affecting the coherent population trapping.