Intersubband Absorption Saturation in InGaAs-AlAsSb Quantum Wells

For realizing futuristic optical communications networks with greater than 100Gb/s transmission capability, highly efficient, ultra-fast all-optical devices are crucial at communication wavelengths (<2 mm). Such devices can be realized by making use of the large and fast intersubband transition (ISBT) non-linearity. However, for achieving ISBTs in the communication wavelength region, one requires a large conduction-band offset material. We reported the possibility of one of the crucial all-optical device, all-optical switch, based on ISBT absorption saturation, operating in the < 2 mm wavelength range using InGaAs-AlAsSb quantum well structures. The efficiency of such a device is defined in terms of the switching response time and the switching energy. While the relaxation time related to the switching response time can be estimated from a direct pump-probe measurement, estimation of the saturation intensity related to the switching energy is not that straightforward. In this work, we carry out a detailed study to estimate the saturation current in Sb-based quantum wells