Abstract

We report the first experimental investigation on the long standing, fundamental problem of QED intra-atom quantum correlations¹,²,³. It is well known that the quantum analysis of the problem of the interacting atoms in free-space, based on a Dicke Hamiltonian, shows an unexpected non causal intra-atom correlation transfer. We show theoretically that the problem is fully resolved by the use of the complete hamiltonian, i.e., including the anti-resonant contribution⁴. However, in spite of the existence of this satisfactory quantum-theoretical approach, the transfer of QED correlations within a single-mode, plane, Casimir microcavity still shows a somewhat puzzling noncausal behavior when the atoms are correlated by transverse interactions, i.e., taking place in direction parallel to the plane of the cavity and then orthogonal to the K - vector of the allowed mode. The "spatial" conterpart of this problem, the establishment of the transverse "size" of the mode, was already investigated by us in an early paper⁵. In that work it was demonstrated that the transverse correlation between two atoms inside a microcavity takes place within the coherence length l_c = 2λ(fm)^1/2, where f and m represent the finesse and the order of the microcavity respectively. By the present work, the investigation is carried out to the theoretical, as said, and the experimental analysis of the complete correlation problem in space-time, then fully implying the Einstein causality within the process. The experimental layout is shown in Fig.1. Two equal, mutually delayed, 50 fs, 10 Mw laser pulses generated by an amplified CPM laser are injected and focussed in a region of 15 μm of diameter in an active microcavity with a molecular solution of oxazine - 725 as active medium: the two pulses are then the "pump" of two identical, virtually "thresholdless" microlasers placed at a transverse distance d in the cavity plane, with d⩽l_c.

© 1994 Optical Society of America