Depopulation and repopulation pumping in coherent population trapping

The role of the depopulation and repopulation pumping mechanisms in coherent population trapping (CPT) is discussed. The case of open $F_{\rm g}\to F_{\rm e}$ transitions resonant with polarized laser light of different polarizations is examined. The efficiency of the preparation of the atomic population into the dark state is studied both for exact Raman resonance and for small Raman detuning. Dependences of the CPT-preparation on the laser polarization are described