COHERENT CONTROL OF TERAHERTZ CHARGE OSCILLATIONS IN A COUPLED-QUANTUM-WELL USING PHASE-LOCKED OPTICAL PULSES

We demonstrate that we can enhance, weaken, and also phase shift terah ertz (THz) radiation emitted by optically excited quantum beats in a c oupled quantum well. The changes in the evolution of the THz radiation are induced by exciting the sample with a second optical pulse, phase locked with the first. We observe phase shifts in the emitted THz rad iation of 330 fs for a change in the optical-pulse separation of only 1.33 fs.