CPT effect and its applications for weak electromagnetic field detection

Summary form only given. We have performed experimental investigations of the coherent population trapping (CPT) phenomenon at a single hyperfine transition at the D₁ and D₂ lines of Rb in a cell, inserted inside a magnetic shield. For observation of CPT dark resonances at a single hyperfine transition the Zeeman degeneracy has to be removed. This was achieved by applying a homogeneous magnetic field H₁, parallel to the laser beam and scanned in both directions around zero value. Additional coil produced constant magnetic or RF electromagnetic field H₂ perpendicular to the beam propagation. The fluorescence signal was registered in order to investigate the influence of the additional electromagnetic field on the dark line parameters. It was observed that the width and the contrast of the dark line are very sensitive to the applied field H_2. Increasing the value/amplitude of H₂ causes increase of the width and decrease of the contrast of the CPT resonances