Relaxation dynamics of interminiband transitions and electron cooling in doped GaAs/AlGaAs superlattices

In this work we investigated the transient behavior of interminiband transitions in a doped GaAs/AlGaAs superlattice using the infrared picosecond pulses delivered by a free electron laser. We found a fast bleaching component, followed by relaxation and thermalization on a time scale of few ps. Thereafter the cooling of the electrons in the ground miniband is observed on a timescale of tens of ps. The cooling can show either positive of negative change in transmission, deriving from the temperature dependence of the absorption spectrum at the respective wavelength.