COHERENT DYNAMICS OF RADIATIVELY COUPLED-QUANTUM-WELL EXCITONS

The optical response of radiatively coupled semiconductor multiple-qua ntum-well structures is investigated theoretically. It is shown that t he transverse optical field leads to a coupling of exciton states with in each well which causes a radiative decay and a mixing of excitonic resonances. Simultaneously, the field-induced long-ranged coupling bet ween different wells leads to collective effects that are very sensiti ve to the detailed geometry of the structure. For a quantum-well spaci ng equal to an integer multiple of half the optical wavelength inside the medium, it is predicted that the collective effects cause a stimul ated decay of electronic excitations that should be observable in eith er transmission or reflection geometry. On the other hand, in a quarte r wavelength structure, the light-induced coupling causes an interwell energy transport and a splitting of the excitonic resonances, that sh ould be observable as quantum beats in the time-resolved transmitted o r reflected signal.