Broadband THz study of excitonic resonances in the high-density regime

摘要

We report the first terahertz study of the intra-excitonic 1s-2p transitionat high excitation densities in GaAs/AlGaAs quantum wells. A strong shift,broadening, and ultimately the disappearance of this resonance occurs withincreasing density, after ultrafast photoexcitation at the near-infraredexciton line. Densities of excitons and unbound electron-hole pairs arefollowed quantitatively using a model of the composite terahertz dielectricresponse. Comparison with near-infrared absorption changes reveals asignificantly enhanced energy shift and broadening of the intra-excitonicresonance.