  We demonstrate that the interaction between excitons and a sea of incoherent
electrons does not preclude excitons dressing by light. We investigate the role
of exciton-electron scattering in the light dressing by measuring the dynamical
absorption spectrum of a modulation-doped CdTe quantum well, which shows a
clear evidence for significant electron scattering of the excitonic states. We
show the occurrence of dressed and correlated excitons by detecting quantum
coherent interferences through excitonic Autler-Townes doublet and ac Stark
splitting, which evolves to Mollow triplet with gain. We also evidence the
partial inhibition of the electron-exciton scattering by exciton-light
coupling.
