L. Kalvans

F-resolved magneto-optical resonances in the D1 excitation of cesium: Experiment and theory

Bright and dark nonlinear magneto-optical resonances associated with the ground state Hanle effect have been studied experimentally and theoretically for D1 excitation of atomic cesium. This system offers the advantage that the separation between the different hyperfine levels exceeds the Doppler width, and hence transitions between individual levels can be studied separately. At the same time, the system retains the advantages offered by ordinary glass cells, including simplicity and subnatural width Hanle resonances. Experimental measurements for various laser power densities and transit relaxation times are compared with a model based on the optical Bloch equations, which averages over the Doppler contour of the absorption line and simultaneously takes into account all hyperfine levels, as well as mixing of magnetic sublevels in an external magnetic field. In contrast to previous studies, which could not resolve the hyperfine transitions because of Doppler broadening, in this study there is excellent agreement between experiment and theory regarding the sign bright or dark, contrast and width of the resonance. The results support the traditional theoretical interpretation, according to which these effects are related to the relative strengths of transition probabilities between different magnetic sublevels in a given hyperfine transition.

Cascade coherence transfer and magneto-optical resonances at 455 nm excitation of cesium

article i nfo We present an experimental and theoretical study of nonlinear magneto-optical resonances observed in the fluorescence to the ground state from the 7P3/2 state of cesium, which was populated directly by laser radiation at 455 nm, and from the 6P1/2 and 6P3/2 states, which were populated via cascade transitions that started from the 7P3/2 state and passed through various intermediate states. The laser-induced fluorescence (LIF) was observed as the magnetic field was scanned through zero. Signals were recorded for the two orthogonal, linearly polarized components of the LIF. We compared the measured signals with the results of calculations from a model that was based on the optical Bloch equations and averaged over the Doppler profile. The calculations agree quite well with the measurements, especially when taking into account the fact that some experimental parameters were only estimated in the model.

Dependence of the shapes of nonzero-field level-crossing signals in rubidium atoms on the laser frequency and power density

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

Conversion of bright magneto-optical resonances into dark resonances at fixed laser frequency forD2excitation of atomic rubidium

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Detailed studies of non-linear magneto-optical resonances at D1 excitation of 85 Rb and 87 Rb for partially resolved hyperfine F-levels

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.

Alignment-to-orientation conversion in a magnetic field at nonlinear excitation of theD2line of rubidium: Experiment and theory

Nonlinear magneto-optical resonances on the hyperfine transitions belonging to the D2 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 lights propagation direction and magnetic field, and laser induced fluorescence (LIF) 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 Rb-87 and near to the Fg=3 --> Fe=4 transition of Rb-85. The bright resonance became dark as the laser power density was increased above 0.6mW/cm2 or 0.8 mW/cm2, respectively. When the Fg=2 --> Fe=3 transition of Rb-87 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 50C. 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.

Relaxation mechanisms affecting magneto-optical resonances in an extremely thin cell: Experiment and theory for the cesiumD1line

transition of rubidium is a challeng-ing system to analyze theoretically because it contains transitions that are only partially resolvedunder Doppler broadening. The theoretical model took into account all nearby transitions, thecoherence properties of the exciting laser radiation, and the mixing of magnetic sublevels in anexternal magnetic field and also included averaging over the Doppler profile. Great care was takento obtain accurate experimental signals and avoid systematic errors. The experimental signals werereproduced very well at each hyperfine transition and over a wide range of laser power densities,beam diameters, and laser detunings from the exact transition frequency. The bright resonanceexpected at the F

Nonlinear magneto-optical resonances for systems with J ∼ 100 observed in K 2 molecules

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

Nonlinear magneto-optical resonances at D 1 excitation of Rb 85 and Rb 87 in an extremely thin cell

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Coherent and incoherent processes responsible for various characteristics of nonlinear magneto-optical signals in rubidium atoms

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 (LIF) 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 yields deeper insight into the processes responsible for these signals. We studied how these signals are dependent on laser power density 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.