Linear pulse propagation in stationary and nonstationary multilevel media in the transient regime

The effects of coherent propagation of an ultrashort pulse through an extended collection of multilevel systems is examined. It is found that the transmitted field shows significant deviation from both Beer’s law absorption and the conventional area theorem. In addition, when the system is in a nonstationary state it is found that additional frequencies can appear in the transmitted pulse spectrum. Such effects may be important in several areas of current interest, such as ultrafast pump–probe, coherent control, and inversionless amplification experiments in extended, multilevel media as well as in ultrafast-laser development.