LOCAL-FIELD EFFECT IN THE 3-LEVEL ATOM

The density matrix evolution for a three-level cascade atom is general ised to high vapour densities by the inclusion of the local field effe ct, and thereby, nonlinear cross-coupling terms arise. Numerical resul ts show that these terms do not affect electromagnetically induced tra nsparency significantly at moderate densities. Opportunities for exper imental observation of the correction in this, and a resonantly-enhanc ed sum frequency mixing system, at very high densities, are indicated.