NONLINEAR RESONANT OPTICAL RECTIFICATION IN A COUPLED-QUANTUM-WELL

We have measured the rectification of far-infrared radiation resonant with the lowest intersubband transition of an AlGaAs/GaAs asymmetric c oupled double-quantum well in which the subband spacing is 11 meV. Fro m these measurements we can extract an intersubband lifetime of 1.2 +/ - 0.4 ns at low excitation intensity and T = 10 K, which appears promi sing for devices which can operate at low excitation and temperature, such as FIR detectors or mixers. From simultaneous measurements of the optical rectification and of the intersubband absorption coefficient we can determine the intensity-dependent intersubband lifetime, which shows a strong decrease for increasing intensities.