Dynamical Franz-Keldysh effect in GaAs/AlGaAs multiple quantum wells induced by single-cycle terahertz pulses

We studied absorption spectra near the band gap of GaAs/AlGaAs multiple quantum wells subjected to strong single-cycle terahertz pulses. With an increasing terahertz electric field, the heavy-hole 1s exciton energy near the band gap redshifts, reaches a maximum, and turns to blueshift. The blueshift increases proportionally to the ponderomotive energy, i.e., the terahertz electric field squared, which differs from the response expected from the Frantz-Keldysh effect (FKE) in a dc electric field. This fact suggests that the observed ponderomotive energy dependence of the blueshift can be ascribed to the dynamical FKE. (C) 2010 American Institute of Physics. [doi:10.1063/1.3518483]