Abstract

We investigate the charge oscillations in an asymmetric double well potential after creating a nonstationary exciton wave packet in a single well. Using time-resolved coherent detection of the submillimeter-wave radiation from this quantum dipole oscillator (Fig. 1), we directly observe the submillimeter-wave radiation from the charge oscillating between the two wells. Fig. 2 shows the terahertz signal emitted from the structure after resonant femtosecond excitation as a function of the field applied to the structure. This field can tune the two eigenstates of the system in and out of resonance. In our sample, the resonance occurs at a voltage of roughly -0.4 V. We observe two distinct contributions to the terahertz signal: (i) an oscillatory part with up to fifteen oscillations at 1.5 THz, and (ii) a field-induced, instantaneous contribution from the creation of polarized excitons in the individual wells.

© 1992 IQEC