Excitation of intersubband transitions by THz pulses

Summary form only given. When intersubband transitions are excited in semiconductor heterostructures, the charge carriers follow the driving field in an oscillatory motion. THz time-domain spectroscopy is an attractive tool to study the polarization following an exciting THz pulse. A time resolution which is shorter than the oscillation time of the driving field enables the observation of the coherent electron motion for the first time. The investigated GaAs/AlGaAs heterostructures are modulation doped parabolic quantum wells.