Abstract

The interaction of coherent light with three-level systems has been the object of many fundamental studies in last years, with consequences ranging from nonlinear dynamics to quantum optics. Two-photon emission processes, for instance, have driven far-reaching investigations of quantum correlations in entangled two-photon states, and have also been shown to lead to rich and nontrivial dynamical scenarios. From a general standpoint, recent trends in the studies of instabilities in nonlinear optical systems, including lasers, point towards the analysis of transverse effects. The present communication investigates the transverse dynamics of broad-area three-level cascade lasers, for which one- and two-photon emission processes coexist under general conditions. When the two emitted electromagnetic fields have widely different intensities, the transverse spectrum of the weakest beam reveals the underlying ac-Stark splitting induced by the most intense one [1]. Under these conditions, spatial correlations between the two emitted transverse patterns can be clearly observed, in what provides, up to our knowledge, the first example of such a phenomenology in active optical media. In the parameter regime where both one- and two-photon emission are comparably important, the correlation far-field profile reflects this coexistence by displaying minima for wavevectors corresponding to the former emission processes and maxima for the latter ones.

© 2000 IEEE