Coherent control of Bloch oscillations by means of optical pulse shaping

Abstract

We excite excitonic wave packets in biased semiconductor superlattices with spectrally shaped ultrashort optical pulses. We tailor the shape and phase of the pulse spectrum in order to control the coherent dynamics of the excitonic wave packets formed from a superposition of three excitonic states. Via careful shaping, we are able to excite either wave packets that exhibit standard Bloch oscillations (BO's) or breathing-mode (BM) motion. These two types of motion are characterized by the presence (BO) or absence (BM) of an internal intraband polarization caused by the electron-hole separation within the excitonic wave packet. The wave packet evolution is monitored using spectrally resolved four-wave mixing. This ability to control the BO's provides a way to control the emitted THz radiation.