Influence of One Monolayer Thickness Variation in GaAs/AlGaAs Five-Layer Asymmetric Coupled Quantum Well upon Electrorefractive Index Change

Abstract

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 Δ n is theoretically studied. The thickness variation of two thicker GaAs layers has a considerable influence on Δ n of the FACQW, while the thickness variation of thin AlAs and AlGaAs barrier layers has a smaller influence on Δ n . The ratio of the thicknesses of the two GaAs well layers significantly affects the Δ n characteristics of the FACQW. The change Δ n 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 Δ n characteristics of the FACQW is also discussed. Even when Δ n 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 Δ n than conventional rectangular quantum wells do.