Theoretical Analysis of Terahertz-Emission from Asymmetric Double-Quantum Wells

Abstract

We theoretically investigate the coherent dynamics in an Al_xGa_1-xAs asymmetric double-quantum well structure optically excited by a short laser pulse. In such structures, states in the different wells can be brought into resonance by an applied electric field. In this case, the laser pulse excites a spatially oscillating electron wave-packet which yields an oscillating dipole moment and thus, as observed experimentally (Roskos et al., 1992), leads to the emission of electromagnetic radiation in the Terahertz range. However, it turned out that the measured frequency of this radiation does not agree with the splitting of the exciton ground states associated with the two subbands brought into resonance, as obtained from the absorption spectrum.