Room-temperature dephasing time of intersubband transitions in heavily-doped InGaAs/AlAs/AlAsSb coupled quantum wells

Room-temperature dephasing time (T2) estimates of 1.55 μm intersubband transitions (ISBT) are presented in InGaAs/AlAs/AlAsSb coupled double quantum wells. In this material, optimized for ISBT at communication wavelengths for all-optic switching application, we also studied the doping-density dependence of the four-wave-mixing decay time as a function of incident excitation intensity. A T2 value of about 292±40 fs is estimated at an intensity corresponding to the saturation intensity in samples that are doped to 2×1019 cm−3. This value is in good agreement with the value estimated from earlier calculations.