Polarization rotation of photon echoes in cesium vapor in a magnetic field

Abstract

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 $6S_{\frac{1}{2}}$ to $7P_{\frac{1}{2}}$ transition in cesium (4593 Å) 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.