Dynamics of the energy relaxation in a parabolic quantum well laser

We explore two parabolic quantum well (PQW) samples, with and without Bragg mirrors, in order to optimize the building blocks of a bosonic cascade laser. The photoluminescence spectra of a PQW microcavity sample is compared against that of a conventional microcavity with embedded quantum wells (QWs) to demonstrate that the weak coupling lasing in a PQW sample can be achieved. The relaxation dynamics in a conventional QW microcavity and in the PQW microcavity was studied by a nonresonant pump-pump excitation method. Strong difference in the relaxation characteristics between the two samples was found. The semiclassical Boltzmann equations were adapted to reproduce the evolution of excitonic populations within the PQW as a function of the pump power and the output intensity evolution as a function of the pump-pump pulse delay. Fitting the PQW data confirms the anticipated cascade relaxation, paving the way for such a system to produce terahertz radiation.