COHERENT CONTROL OF CYCLOTRON EMISSION FROM A SEMICONDUCTOR USING SUBPICOSECOND ELECTRIC-FIELD TRANSIENTS

We have demonstrated the excitation and control of coherent cyclotron emission from a semiconductor using a THz beam containing pairs of sub -picosecond electric field pulses closely spaced in time. The source o f THz radiation in these experiments is a biased coplanar stripline fa bricated on semi-insulating GaAs and edge illuminated with pairs of te mporally and spatially separated 70 fs pulses of near infrared light. A GaAs/AlGaAs two-dimensional electron gas was used in the experiments because of its long intraband phase relaxation time. Changes in the a mplitude and phase of the cyclotron emission are observed when varying the interpulse delay and are well described within the theoretical fr amework of a two level system. (C) 1997 American Institute of Physics.