Excitation power dependence of nonlinear optical response of excitons in GaAs/AlAs superlattices

We studied effects of the miniband structure to control the nonlinear optical response of excitons in GaAs/AlAs superlattices. The excitation-power dependence of the degenerate four-wave-mixing signal shows different saturation power in the samples with the thinner and thicker barriers, while the dependence of dephasing time is almost independent of the barrier width. The analysis of the excitation-power dependence of the photoluminescence spectrum indicates the biexciton generation at lower excitation power in the sample with the thicker barrier width. These results demonstrate that the saturation of the four-wave-mixing signal intensity of the exciton comes from the contribution of the biexcitons. Our results support a possibility that the nonlinear optical response of excitons can be controlled by controlling the barrier width. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim