Abstract

We present a comparative study of Amplification Without population Inversion (AWI) in folded and cascade three-level schemes driven by an on-resonance coherent field in terms of Dressed States Quantum Interference (DSQI) and Quantum Jump (QJ) analyses [1], Using the DSQI analysis, we identify the elements that contribute to destructive or constructive dressed state quantum interference in the probe field absorption spectrum We are able to show in a very simple way that conditions for AWI in closed folded schemes are different from those for close cascade schemes. In particular, they involve two-photon (one-photon) coherence relaxation rates for folded (cascade) schemes. This suggests that AWI has a different physical origin in these configurations, a point not stressed before in the ample literature on the subject. We determine analytically the conditions for AWI at the probe field line center (closed folded schemes) and at the wings of the resonance region (closed cascade schemes). For this last case, we explicitly locate the position of the maximum gain as a function of the probe field detuning.

© 1998 IEEE