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-t ailored quantum well (QW) for ultrafast and low-voltage optical modulators and switches. First, the influence of one monolayer (ML) thickness variatio n of a single layer in the GaAs/AlGaAs FACQW on the electrorefractive index change Deltan is theoretically studied. The thickness variation of two thi cker GaAs lavers has a considerable influence on Deltan of the FACQW. while the thickness variation of thin AlAs and AlGaAs barrier layers has a small er influence on Deltan. The ratio of the thicknesses of the two GaAs well l ayers significantly affects the Deltan characteristics of the FACQW. The ch ange Deltan does not vary appreciably as long as the ratio is kept constant . Second, the influence of the statistical fluctuation of the layer thickne ss 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 occu rrence probability of a layer being thicker or thinner by 1 ML, the FACQW s till has a much larger Deltan than conventional rectangular quantum wells d o.