2-PHOTON CORRELATIONS IN THE INTERFERENCE OF A RESONANCE FLUORESCENCE AND A CLASSICAL FIELD

The joint probability P12 of detecting two photons at two different positions in the interference of a classical field with the resonance fluorescence field from a coherently driven two-level atom is investigated. We find that P12 shows a stronger modulation with detector separation than is predicted by a classical wave theory. Under stationary conditions and if the driving field is strong enough to saturate the atomic transition, the relative modulation amplitude a of the P12 pattern reaches its maximum possible value a = 1 for E-->0 (where E is the classical field amplitude), but simultaneously the whole phenomena vanishes, P12-->0. For equal intensities of the classical and the resonance fluorescent field we have a = 2/3. Compared with this, a classical wave theory predicts a possible maximum value of a = 1/2.