Coherence vs incoherence in stepwise laser excitation

摘要

We demonstrate the manner in which solutions of the (coherent) Schrouml;dinger equation for multistep excitation approach those of an (incoherent) rate equation. For a twohyphen;level system, coherence produces oscillations about the mean ratehyphen;equation values. In more generalNhyphen;level sequences the two types of solutions agree in the limit described by Ackerhalt and Eberly. We point out instances in which a simple rate equation cannot duplicate results of the Schrouml;dinger equation.