Abstract

The measurement of cyclotron resonance absorption is a well-established technique in the study of the properties of charge carriers in semiconductors. There are many ways of observing coupling between cyclotron resonance and other phenomena, such as plasmon modes. Recently, femtosecond optoelectronic techniques have been developed, permitting the generation and detection of ultrafast terahertz, electromagnetic transients (TEMT), which have been applied to the study of dynamical conductivity of a high-mobility 2-D electron gas.² Here we report the observation of subpicosecond electric field oscillations due to coherent cyclotron motion of electrons in high-mobility GaAs/AlGaAs heterostructures. The duration of these oscillations can be several times as long as the exciting terahertz pulse, and over 10 full periods have been seen, depending on the sample and the magnetic field. In addition, we have generated additional electrons (and holes) by means of femtosecond photopumping and have observed the coherent emission of cyclotron (and magnetoplasmon) radiation.

© 1994 Optical Society of America