Realization of lasing without inversion in the system with lower-level coherence

摘要

Abstract: It is shown that the ladder system with lower-level coherence may be used to obtain lasing without inversion. The present model system has several important features. (1) No requirement is placed on atomic decay rates. (2) The Rabi frequency of coherence-driving field must exceed a lower threshold. (3) An unidirectional pumping is indispensable. (4) A dressed-state-coherence origin of gain is proved without strong coherence-driving field approximation.!18