Influence of one monolay er thickness variation in GaAs/AlGaAs five-layer asymmetric coupled quantum well upon electrorefractive index change

The five-layer asymmetric coupled quantum well (FACQW) is a new potential-tailored quantum well (QW) for ultrafast and low-voltage optical modulators and switches. First, the influence of one monolayer (ML) thickness variation of a single layer in the GaAs/AlGaAs FACQW on the electrorefractive index change Deltan is theoretically studied. The thickness variation of two thicker GaAs lavers has a considerable influence on Deltan of the FACQW. while the thickness variation of thin AlAs and AlGaAs barrier layers has a smaller influence on Deltan. The ratio of the thicknesses of the two GaAs well layers significantly affects the Deltan characteristics of the FACQW. The change Deltan does not vary appreciably as long as the ratio is kept constant. Second, the influence of the statistical fluctuation of the layer thickness by 1 ML in all of the layers on the Deltan characteristics of the FACQW is also discussed. Even when Deltan decreases with the increase of the occurrence probability of a layer being thicker or thinner by 1 ML, the FACQW still has a much larger Deltan than conventional rectangular quantum wells do.