RELAXATION OF POLARIZED EXCITONS IN ASYMMETRIC DOUBLE-QUANTUM WELLS

We consider the intrawell and interwell relaxation of circularly polar ized excitons in an asymmetric double-quantum-well structure. For the intrawell case (photocreated light excitons coupled to the detected he avy excitons by an optical-phonon emission) the polarization changes s ign after a fast relaxation. For the interwell case (transfer of polar ization from the ground heavy exciton of the narrow well towards the g round heavy exciton of the wide well) we observe that the initial pola rization is recovered after energy relaxation only if a fast-relaxatio n path is available which involves only intermediate heavy exciton sta tes.