Giant nonlinear optical rectification at 8–12 μm in asymmetric coupled quantum wells

We report giant, nonlinear optical rectification in asymmetric quantum wells weakly coupled by an intermediate potential barrier. This phenomenon originates from (i) macroscopic displacements (30 nm) of carriers during optical transitions and (ii) large storage times of excited electrons because of a slow transfer mechanism between the wells (≊6 ps at 77 K). The resulting rectification coefficient is 1.62×10−3 m/V per well, more than six orders of magnitude higher than in bulk GaAs. These structures really behave as giant ‘‘quasimolecules’’ optimized for infrared optical nonlinearities and their use may be envisioned for a new class of infrared detectors.