Physical Review A
Effect of the upper-level decay on the resonantly enhanced four-wave mixing in a modified double- Λ system
Fam Le Kien, K. Hakuta
Abstract
We study the continuous resonant four-wave mixing in a medium of atoms with a modified double-$\ensuremath{\Lambda}$ level configuration. Under the far-off-resonance condition for a pair of levels, we reduce the five-level scheme to an effective three-level scheme, with a two-photon coupling between the two lower levels. We derive the exact steady-state solution to the density-matrix equations for the reduced scheme and obtain the wave-mixing equations for the fields in the continuous-wave regime. We show that the upper-level decay may substantially affect the resonantly enhanced wave-mixing process. We demonstrate that this decay shortens the conversion cycle rather than prolongs it.