Coherent control of phonon quantum beats

The coherent control of excitons coupled to longitudinal optical phonons is analyzed in the quantum kinetic regime. Different models allowing for diff erent levels of sophistication in the theoretical treatment are compared. W ithin a simple two-level model of the exciton system analytical results rel evant for short-time excitation in the low-density regime are derived, whic h are nonperturbative with respect to the exciton-phonon interaction. For p ulses of finite duration and high intensity, numerical calculations are pre sented realizing a nonperturbative treatment with respect to both the excit on-phonon as well as the exciton-photon coupling. It is shown that for two- level systems, the use of high intensity pulses opens new possible control scenarios that combine the effects of phase control with Rabi oscillations. These findings are compared with quantum kinetic calculations for a two-ba nd semiconductor model. Here we present results for one, two and three dime nsions. Within this model, the coupling to the continuum of states above th e band edge provides a dephasing mechanism missing in few-level models. It is shown that also the dephasing properties can be coherently controlled. F urthermore, it is demonstrated that the strength and controllability of pho non beats characteristically depend on the dimension of the system. (C) 199 9 Academic Press.