We report observations of the rotation of the plane of polarization of photon echoes by a weak axial magnetic field. The echoes are generated on the
6S21 to
7P21 transition in cesium (4593 \AA{}) by a sequence of two collinear laser pulses polarized in the same direction. When a magnetic field is applied along the propagation axis the polarization vector of the echo is rotated from that of the exciting pulses. We measure the intensity of the photon echo signal polarized orthogonal to the excitation pulse polarization as a function of magnetic field and pulse separation. The theoretical analysis decribes cesium atoms as a nondegenerate multilevel system, consisting of ground and excited Zeeman-split hyperfine-structure levels. The theory presented predicts the observed dependence on magnetic field strength, pulse separation, and excited- and ground-state
g factors. A novel method of observing photon echoes is described which uses the polarization rotation effect to replace electro-optical shutters often employed in photon echo experiments.
New studies of
Na2 hyperfine structure (hfs) by the laser-induced-fluorescence molecular-beam magnetic-resonance technique are described which show that state selection and detection by strong optical fields can produce rf-magnetic-resonance spectra which differ drastically from the Rabi shape, even though the optical and rf fields do not act simultaneously on the molecules. We suggest that in the case of optically unresolved ground-state sublevels these effects are due to the creation of ground-state coherence by absorption and stimulated-emission cycles in the laser field, and we present a model calculation which exhibits the essential features of the observed spectra. We also give a proof that no model based only upon populations can explain the negative signals we observe.
The effect of coherent population trapping related to quantum interference of states now is well investigated for (Lambda) -systems in which the lower levels are generated by the hyperfine structure sublevels of the ground state of the atom. At present time the majority of experimental researches of resonances of CPT are made with alkaline atoms, for which hyperfine components of the ground state have typical interval of several gigahertz. We consider CPT in (Lambda) -systems in which the fine structure sublevels of the atom generate the lower levels. Our computer simulations have been made for the thallium atom for which the distance between sublevels of fine structure components is approximately 7792 cm-1. Theoretical and computer simulations of dynamics and dispersions of population of the considered multilevel system allow to detect new peculiarities of effect and demonstrate the influence of orientation and strength of magnetic field.