Abstract

Recently there has been considerable interest in realizing light amplification without atomic population inversion. Such ideas would be valuable in production of coherent short-wavelength radiation that generally require extremely strong and rapid pumping to create population inversion at the relevant transition. Several schemes have been investigated theoretically,¹ and recently some successful experimental results have also been reported.² Inversionless amplification is made possible by means of quantum interference that occur in a transition whose upper or lower state is coherently coupled doublet, in bare or dressed state basis. However, the amplification conditions in these previously proposed schemes depend on the atomic energy level structure, and so far the experimental demonstrations are limited to the visible spectral region. We propose in this paper a novel scheme for inversionless amplification utilizing coherence between the upper state and a virtual state created by intense bichromatic pumping, whose amplification condition are less restricted by atomic parameters than those in previously proposed schemes.

© 1995 IEEE