Absorption spectroscopy of cold caesium atoms confined in a magneto-optical trap

Absorption spectra of cold caesium atoms confined in a magneto-optical trap are measured around D_2 line at 852nm with a weak probe beam. Absorption reduction dip due to electromagnetically induced transparency (EIT) effect induced by the cooling/trapping field in a V-type three-level system and a gain peak near the cycling transition are clearly observed. Several mechanisms mixed with EIT effect in a normal V-type three-level system are briefly discussed. A simple theoretical analysis based on a dressed-state model is presented for interpretation of the absorption spectra.