Cavity-induced coherence effects in spontaneous emissions from preselection of polarization

Spontaneous emission can create coherences in a multilevel atom having clos e-lying levels, subject to the condition that the atomic dipole matrix elem ents are nonorthogonal. This condition is rarely met in atomic systems. We report the possibility of bypassing this condition and thereby creating coh erences by letting the atom with orthogonal dipoles interact with the vacuu m of a preselected polarized cavity mode rather than the free-space vacuum. We derive a master equation for the reduced density operator of a model fo ur-level atomic system, and obtain its analytical solution to describe the interference effects. We report the quantum beat structure in the populatio ns. [S1050-2947(99)07203-0].