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.
© 1999 Optical Society of America
S. Hughes and D. S. Citrin, "Dynamic Franz-Keldysh effect: excitonic versus free-carrier excitation schemes," Opt. Lett. 24, 1068-1070 (1999)