Transfer of coherent dynamics between discrete excitons and exciton Fano continua in quantum wells

Four-wave-mixing in semiconductor quantum wells with spectrally shaped broadband laser pulses demonstrates that the coherent dynamics of discrete excitons can be detected in the coherent emission from exciton Fano continua and vice versa. In particular, quantum beating between discrete heavy and light hole excitons is observed in the coherent emission from the continuum. The results can be understood in a common ground-state picture of strongly coupled transitions. This model shows that the transfer of the amplitude of the nonlinear coherent polarization is at the origin of the experimental results.