Ultra-low intersubband absorption saturation intensity in InGaAs/AlAs/AlAsSb coupled double quantum wells with AlAs diffusion-stopping layers

We have grown InGaAs/AlAs/AlAsSb coupled double quantum wells (C-DQWs) with AlAs diffusion-stopping layers by molecular beam epitaxy. Although the structural characterization of an obtained sample suggested a relatively poor structural quality, optical measurements revealed its high optical quality. The intersubband absorption saturation intensity in the C-DQW sample was extremely low, measuring 34 fJ/μm² at the optical communication wavelength of 1.62 μm, while ultrafast response times of less than 1 ps were maintained. This result clearly points to the potential for C-DQWs with AlAs diffusion-stopping layers to be used in all-optical switches that can be applied in ultrafast optical communication systems.