Résumé
We propose a new experimental technique for the optical study of dark and bright spatially indirect excitons in coupled quantum wells. We demonstrate that indirect excitons strongly contribute to nonlinear optical effects: photoinduced reflectivity and Kerr rotation, detected at the direct exciton transition frequency. In contrast to conventional photoluminescence measurements which are sensitive only to optically active |±1> states inside the light cone, the proposed technique allows to access yet hidden dark components of excitonic systems.