Coherent control of the nonradiative decay of excitons in asymmetric quantum well structures - art. no. 045316

We theoretically propose coherent control of the nonradiative decay of exci tons in infrared-coupled asymmetric quantum wells. This is done by (i) indu cing intraband multiphoton quantum coherences between exciton states associ ated with three conduction subbands (E1, E2, and E3), and (ii) adjusting th e contributions of these coherences using competition between one- and two- photon coupling of these states. The intraband excitonic transitions are ca used by one or two infrared laser beams resonant with the intersubband tran sitions between E1, E2, and E3. We show that by tuning these beams to allow coupling of the E1-HH1, E2-HH1, and E3-HH1 excitons with different configu rations one can coherently manipulate the quantum efficiency of exciton emi ssion. In an asymmetric double GaAs/AlxGa1-xAs quantum well this could lead to nearly complete destruction of the emission spectrum, or to the immunit y of excitons from enhancement of their nonradiative decay rates via the in traband transitions. We discuss these effects in terms of coherent populati on trapping of excitons and show how field-coherent destruction effects inf luence the multiphoton excitonic coherences.