QUANTUM BEATS OF EXCITONS IN ZN1-XCDXSE/ZNSE MULTIPLE-QUANTUM-WELL STRUCTURES

We investigate the coherent dynamics of excitons in Zn1-xCd xSe/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. © 1995 American Institute of Physics.