Answers are grounded in this paper and cite their sources.
The theory of degenerate four-wave mixing using two-photon transitions is formulated. Two kinds of mechanisms compete in generating conjugate waves leading to two phenomena that do not occur in two-level media: (1) a double-peaked reflection spectrum and (2) coupled-mode oscillation in absorbing media. In addition, because of the dynamic Stark-shifted line center, the reflection coefficient approaches a constant value at large intensities, unlike the two-level coefficient, which bleaches to zero.
No takes yet. Share an insight, caveat, or question.
Fu et al. (1980) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: