THz radiation from coherent population changes in quantum wells

We identify the contributions to the terahertz (THz) signals from both the creation of polarized uncorrelated electron-hole pairs and polarized excitons in GaAs/${\mathrm{Al}}_{0.3}$ ${\mathrm{Ga}}_{0.7}$As quantum wells. We find that the THz radiation from the creation of polarized excitons is comparable in magnitude to that from the creation of polarized uncorrelated e-h pairs. Unlike the THz transient from uncorrelated e-h pairs, the signal from polarized excitons is also strongly influenced by the combined effects of detuning and finite pulse duration.