Quantum beats of excitons in Zn1−xCdxSe/ZnSe multiple quantum well structures

Abstract
We investigate the coherent dynamics of excitons in Zn1−x Cd x Se/ZnSe multiple quantum wells by means of spectrally integrated and spectrally resolved transient four‐wave mixing. When simultaneously exciting the heavy‐ and light‐hole exciton resonance, a beating of the spectrally integrated four‐wave mixing signal is observed. The measured beating period does not exactly correspond to the energetic split of the involved free‐exciton resonances. By including a bound‐exciton state in the calculation of the four‐wave mixing signal, quite a reasonable fit can be achieved yielding the dephasing times of the excitonic transitions. The spectrally resolved signal allows to determine the origin of the oscillation as a quantum beat between the light‐ and heavy‐hole exciton.