COHERENT POPULATION TRAPPING WITH LOSSES OBSERVED ON THE HANLE EFFECTOF THE D-1 SODIUM LINE

We consider the coherent-population-trapping phenomenon in a thermal s odium atomic beam. We compare the different coherent-population-trappi ng schemes that can be established on the D-1 line using the Zeeman su blevels of a given ground hyperfine state. The coherent-population-tra pping preparation is examined by means of a Hanle-effect configuration . The efficiency of the coherent-population-trapping phenomenon has be en examined in presence of optical pumping into hyperfine levels exter nal to those of the excited transition. We show that both the contrast and the width of the coherent population trapping resonance strongly decrease when the optical pumping rate is increased. In the experiment , the loss rate due to optical pumping has been controlled by means of a laser repump of variable intensity.