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, we directly observe the submillimeter-wave radiation from the charge oscillating between the two wells. Figure 1 shows the terahertz signal emitted from the structure after resonant femtosecond excitation as 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 -0,4V, We observe two distinct contributions to the terahertz signal: (i) an oscillatory part with up to 15 oscillations at 1.5 THz, and (ii) a field- induced, instantaneous contribution from the creation of polarized excitons in the individual wells.

© 1992 Optical Society of America