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We studied alignment-to-orientation conversion caused by excited-state level crossings in a nonzero magnetic field of both atomic rubidium isotopes. Experimental measurements were performed on the transitions of the D2 line of rubidium. These measured signals were described by a theoretical model that takes into account all neighboring hyperfine transitions, the mixing of magnetic sublevels in an external magnetic field, the coherence properties of the exciting laser radiation, and the Doppler effect. In the experiments, laser-induced fluorescence components were observed at linearly polarized excitation and their difference was taken afterwards. By observing the two oppositely circularly polarized components, we were able to see structures not visible in the difference graphs, which give deeper insight into the processes responsible for these signals. We studied how these signals are dependent on intensity and how they are affected when the exciting laser is tuned to different hyperfine transitions. The comparison between experiment and theory was carried out fulfilling the nonlinear absorption conditions. The theoretical curves described the experimental measurements satisfactorily, reproducing even small features in the shapes of the curves. [ABSTRACT FROM AUTHOR]

We have measured magneto-optical signals obtained by exciting the D1 line of cesium atoms confined to an extremely thin cell (ETC), whose walls are separated by less than 1 μm, and developed an improved theoretical model to describe these signals with experimental precision. The theoretical model was based on the optical Bloch equations and included all neighboring hyperfine transitions, the mixing of the magnetic sublevels in an external magnetic field, and the Doppler effect, as in previous studies. However, in order to model the extreme conditions in the ETC more realistically, the model was extended to include a unified treatment of transit relaxation and wall collisions with relaxation rates that were obtained directly from the thermal velocities of the atoms and the length scales involved. Furthermore, the interactions of the atoms with different regions of the laser beam were modeled separately to account for the varying laser beam intensity over the beam profile as well as saturation effects that become important near the center of the beam at the relatively high laser intensities used during the experiments in order to obtain measurable signals. The model described the experimentally measured signals for laser intensities for magnetic fields up to 55 G and laser intensities up to 1 W/cm² with excellent agreement. [ABSTRACT FROM AUTHOR]

We studied magneto-optical resonances caused by excited-state level crossings in a nonzero magnetic field. Experimental measurements were performed on the transitions of the D2 line of rubidium. These measured signals were described by a theoretical model that takes into account all neighboring hyperfine transitions, the mixing of magnetic sublevels in an external magnetic field, the coherence properties of the exciting laser radiation, and the Doppler effect. Good agreement between the experimental measurements and the theoretical model could be achieved over a wide range of laser power densities. We further showed that the contrasts of the level-crossing peaks can be sensitive to changes in the frequency of the exciting laser radiation as small as several tens of megahertz when the hyperfine splitting of the exciting state is larger than the Doppler broadening. [ABSTRACT FROM AUTHOR]

Nonlinear magneto-optical resonances on the hyperflne transitions belonging to the Z)2 line of rubidium were changed from bright to dark resonances by changing the laser power density of the single exciting laser field or by changing the vapor temperature in the cell. In one set of experiments atoms were excited by linearly polarized light from an extended cavity diode laser with polarization vector perpendicular to the light's propagation direction and magnetic field, and laser-induced fluorescence was observed along the direction of the magnetic field, which was scanned. A low-contrast bright resonance was observed at low laser power densities when the laser was tuned to the Fg =2 --· Fe = 3 transition of 87Rb and near to the Fg = 3 --> Fe = 4 transition of 85Rb. The bright resonance became dark as the laser power density was increased above 0.6 mW/cm2 or 0.8 mW/cm2, respectively. When the Fg = 2 -->· Fe = 3 transition of 87Rb was excited with circularly polarized light in a second set of experiments, a bright resonance was observed, which became dark when the temperature was increased to around 50°C. The experimental observations at room temperature could be reproduced with good agreement by calculations based on a theoretical model, although the theoretical model was not able to describe measurements at elevated temperatures, where reabsorption was thought to play a decisive role. The model was derived from the optical Bloch equations and included all nearby hyperfine components, averaging over the Doppler profile, mixing of magnetic sublevels in the external magnetic field, and a treatment of the coherence properties of the exciting radiation field. [ABSTRACT FROM AUTHOR]

We show that it is possible to model accurately optical phenomena in intense laser fields by taking into account the intensity distribution over the laser beam. We present an extension of an earlier theoretical model that divides an intense laser beam into concentric regions, each with a Rabi frequency that corresponds to the intensity in that region, and solve a set of coupled optical Bloch equations for the density matrix in each region. Experimentally obtained magneto-optical resonance curves for the Fg=2 → Fe = 1 transition of the D1 line of 87Rb agree very well with the theoretical model up to a laser intensity of around 200 mW/cm² for a transition whose saturation intensity is around 4.5 mW/cm². We examine the spatial dependence of the fluorescence intensity in an intense laser beam experimentally and theoretically. We present and discuss the results of an experiment in which a broad, intense pump laser excites the Fg = 4 → Fe = 4 transition of the D2 line of cesium while a narrow probe beam scans the atoms within the pump beam and excites the D1 line of cesium, whose fluorescence is recorded as a function of probe beam position. Experimentally obtained spatial profiles of the fluorescence intensity agree qualitatively with the predictions of the model. [ABSTRACT FROM AUTHOR]