Abstract

It is known that asymmetric coupled quantum wells (ACQW's) can exhibit peculiar nonlinearities, such as a third-order nonlinearity,¹ and nonlinear photoluminescence.² Here we report the large optical nonlinearity in the photocurrent response of narrow ACQW structures. The ACQW sample (see Fig. 1) was grown by molecular-beam expitaxy on a Si-doped (100) n⁺ GaAs substrate. It has 25 ACQW periods, each of which consists of two GaAs quantum wells (QW's) with thicknesses of 18 Å and 32 Å, separated by a 15-Å Al_0.4Ga_0.6As barrier. Thick barriers of 100 A isolate the coupled QW's from each other. Two 3000-Å undoped Al_0.4 Ga_0.45Ga_0.55As layers have been incorporated into the structure designed for the waveguiding experiments, but we found that they are important even in the case of transverse light propagation.

© 1991 Optical Society of America