Bulg. J. Phys. vol.39 no.2 (2012), pp. 150-164



Modelling of Nonlinear Interaction of Rb87 Atoms with Polarized Radiation

V. Polischuk1, V. Domelunksen1, E. Alipieva2, G. Todorov2
1V.A. Fock Physics Institute, St. Petersburg State University, 198903 St. Petersburg, Russia
2Institute of Electronics "Acad. E. Djakov", Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia, Bulgaria
Abstract. The ultra narrow resonances, obtained by means of polarization spectroscopy of alkali atoms, originate from the destruction of the laser-induced coherence in the ground state. In the case of single-frequency, near resonance excitation and suitable geometry the well-known ground state Hanle effect is observed. Coherent population trapping in Hanle configuration is a nonlinear modification of this effect, observed in the fluorescence from the upper level. The ground state coherence is transmitted from the laser field and higher rank polarization moments are created. Using the irreducible tensor operator formalism programs for numerical modelling of this effect has been developed and presented here. The velocity distribution of the atoms, the Gaussian distribution of the laser beam, stray magnetic field, and the experimental geometry are taken into account. The scheme of conversion of the octupole (κ = 3) and hexadecapole (κ = 4) polarization moments (PM) through the laser and magnetic fields into the upper level quadropoles fq2 is proposed. The conversion of the high-rank polarization moments (PM) into observable components is also discussed. The results of the modelling are compared with the measured ones at different experimental conditions.

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