Coherent Population Trapping in Multi-Level Atomic Systems

Coherent population trapping (CPT) is treated in multi–level systems, excited by two– or four–frequency laser light. The dynamics of filling non–absorbing (dark) states is investigated. In cases where all transitions involved are excited (closed systems), the effect becomes dependent on the relative phase of the light waves. Further electromagnetically induced transparency (EIT) is described in three– and four–level systems and used for effective side band generation