Abstract

Aiming to observe quantum beats originating from zeeman coherences created in higher-lying sodium states we detected a forward scattered light of a beam probing the atomic sample.^[1] We applied three near colinear pulse laser beams which propagated perpendicularly to the vector of the magnetic field strength (for the set-up see Fig. 1). The first one, of the linear π polarization, excited the intermediate leve$\overrightarrow{B}$l 3² P_1/2 (or 3² P_3/2). The second, of linear σ polarization, excited stepwisely the level of 4² D_3/2 (or 4² D_3/2 and 4² D_5/2 together). Pulses of this laser created coherences between the Zeeman sublevels of magnetic numbers differing by 2 (Δm =2) in both lower and upper states. The third beam, much weaker and delayed of about 40 ns probed the time evolution state of the coherences. The probe beam was polarized linearly at the angle of 45° with respect to the $\overrightarrow{B}$ vector (Voigt configuration). The beam, before it was detected, passed through a crossed polarizer like in polarization spectroscopy.^[2] The signal registered revealed only the changes of the probe beam polarization induced by the opticaly active (mainly biréfringent^[3]) atomic sample.

© 1992 IQEC