Orientation of atoms and molecules under excitation by elliptically polarized light

Valery Milner, B. M. Chernobrod, Yehiam Prior

The interaction of laser light of arbitrary polarization with systems of high angular momentum is considered. We show that elliptically polarized light creates an anisotropic spatial distribution of atomic and molecular angular momentum which is qualitatively different from the alignment and orientation induced by light of circular or linear polarization. Multilevel coherent population trapping within a manifold of ground-state magnetic sublevels results in a nonclassical behavior of a high-$J$ molecular rotor. The classical approximation for the angular momentum distribution is compared with the exact quantum calculations, and is shown to fail in cases of long interaction times and high intensities of the exciting light. In these limits, the quantum uncertainty defines the spatial width of the angular distribution. The applicability of the classical treatment is analyzed and found to be different in the cases of $\stackrel{\ensuremath{\rightarrow}}{J}J\ensuremath{-}1$ and $\stackrel{\ensuremath{\rightarrow}}{J}J$ transitions. A biaxial spatial orientation with two preferential axes of rotation is experimentally created in sodium atoms via coherent population trapping by elliptically polarized light. A method for producing an arbitrary orientation of atomic angular momentum by magnetic field assisted coherent population trapping is proposed.

Anatolii M. Shalagin

M. Ya. Agre, Л. П. Рапопорт, M. E. Alferieff

A. V. Taǐchenachev, Anatolii M Tumaikin, Valeriy I. Yudin

A general approach to the problem of spontaneous transfer of light-induced anisotropy in the scheme of Raman scattering of resonance elliptically polarized light is developed. Depending on the type of the field-excited ( a )↔( b ) transition, the stationary distribution of atoms over the sublevels of the final level ( c ) coupled with the excited level only by the ( b )→( c ) spontaneous transition is either isotropic and does not depend on field parameters or anisotropic. In the latter case, the anisotropy is determined by both field polarization and (at fairly large level momentum values) field detuning and intensity.

W. Oberheim, W. Siegmund

G. S. Pati, Raghwinder Singh Grewal, Renu Tripathi

We report our investigations on the dependence of magnetic resonance spectrum on the light ellipticity and the polarization angle. A rubidium vapor cell with octade-cyltrichlorosilane (OTS) antirelaxation coating has been used in our experiment to produce narrow linewidth magnetic resonances. We show that excitation using elliptically polarized light can simultaneously produce the alignment and orientation resonances in a Bell-Bloom interaction geometry. We have developed a theoretical model to calculate the resonance spectrum using light with a varying degree of ellipticity. Amplitudes of the alignment and orientation resonances show a strong dependence on the light ellipticity. Our study shows that the duty cycle of light modulation can effectively control the amplitude variations of the alignment and orientation resonances with light ellipticity. We propose that the difference between the alignment and orientation resonance amplitudes can be used for in situ measurement of the light