Optical rectification as a probe of quantum dynamics in a heterostructure

We have measured the rectification of far-infrared radiation resonant with the lowest intersubband transition of an AlGaAs/GaAs asymmetric coupled double-quantum well in which the subband spacing is 11meV. From these measurements we can extract an intersubband lifetime of 1.2±0.4 ns at low excitation intensity and T=10 K, which appears promising for devices which can operate at low excitation and temperature, such as FIR detectors or mixers. At high intensities saturation of the rectified signal is observed due to saturation of the two level system.