| Popis: |
Recent experimental and theoretical work suggests that excitons in GaAs/AlGaAs multiple quantum wells may be localized by disorder, or delocalized with Bloch-type wavefunctions1. At low temperature, localized excitons are expected to be characterized by spectral diffusion and by long optical coherence times, while delocalized excitons have short coherence times and exhibit spatial mobility2. The short optical coherence time associated with delocalized excitons results in a linear absorption profile that is primarily homogeneously broadened, while the disorder associated with localized excitons leads to an inhomogeneously broadened profile. In this work, we investigate the energy and phase relaxation of HH1 excitons in GaAs/AlGaAs MQW's at low temperature, and provide evidence that, dependent on the exciton density, both localized and delocalized excitons contribute to the nonlinear optical response. |
