title: Dynamic Franz-Keldysh effect: excitonic versus free-carrier excitation schemes.
abstract: We theoretically investigate the dynamic Franz-Keldysh effect for subpicosecond optical pulses on quantum wells as a function of detuning from the bandgap. For specific spectral excitation regimes we find dramatic nonlinear enhancement effects that are due to the preferential creation of terahertz- (THz-) field-driven propagating excitons and free electron-hole pairs in the THz and the optical domains, respectively. Our results explain why previous measurements of THz sidebands in the optical domain were so weak; we suggest and demonstrate a remarkably better experiment.
authors: S
authors: S
authors: Hughes
authors: D S
authors: DS
authors: Citrin