Coherent control of the nonradiative decay of excitons in asymmetric quantum well structures

Abstract

We theoretically propose coherent control of the nonradiative decay of excitons in infrared-coupled asymmetric quantum wells. This is done by ͑i͒ inducing intraband multiphoton quantum coherences between exciton states associated with three conduction subbands ͑E1, E2, and E3͒, and ͑ii͒ adjusting the contributions of these coherences using competition between one-and two-photon coupling of these states. The intraband excitonic transitions are caused by one or two infrared laser beams resonant with the intersubband transitions 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 configurations one can coherently manipulate the quantum efficiency of exciton emission. In an asymmetric double GaAs/Al x Ga 1Ϫx As quantum well this could lead to nearly complete destruction of the emission spectrum, or to the immunity of excitons from enhancement of their nonradiative decay rates via the intraband transitions. We discuss these effects in terms of coherent population trapping of excitons and show how field-coherent destruction effects influence the multiphoton excitonic coherences.

Matched slow optical soliton pairs via biexciton coherence in quantum dots

“…A more complete theoretical treatment taking into account coherent nonlinear optical processes for the dephasing rates induced by Coulomb correlations is thought to be interesting, but beyond the scope of this paper. The effects of Coulomb correlations on coherent nonlinear optical processes have been investigated extensively in earlier studies and can be described by microscopic theories based on dynamics controlled truncation schemes and also on the use of N -exciton many-body eigenstates [55][56][57][58]. We would rather take phenomenological values (available from earlier experiments) for the dephasing rates here since we are interested in showing applications of the this SQD system as an efficient device for generating optical solitons.…”