Coherent Population Trapping and its Effects on Light-Induced Drift

Abstract

In closed three-level Λ-type systems, where two ground-state levels are coupled by laser fields to a single excited level coherent population trapping can occur. A stationary linear superposition of the two ground states then exists, that is immune to excitation by the combined laser fields1. Spontaneous emission provides a channel to populate this nonabsorbing state in which the atoms remain trapped. Thus no particles can reach the excited state; the fluorescence will vanish. Clearly, any phenomenon, which, in some way, measures the excited state population, will be sensitive to the effects of coherent population trapping.