Zybell, S.S.ZybellSchneider, H.H.SchneiderWinnerl, S.S.WinnerlWagner, M.M.WagnerKöhler, KlausKlausKöhlerHelm, M.M.Helm2022-03-042022-03-042011https://publica.fraunhofer.de/handle/publica/22541410.1063/1.36152982-s2.0-79961050393We investigate the time-resolved photoluminescence (PL) dynamics of an undoped GaAs/AlGaAs multiple quantum well under mid-infrared (MIR) irradiation. A time-delayed MIR laser pulse from a free-electron laser, tuned to the intersubband transition energy of the quantum well, induces temporal quenching of the PL intensity with subsequent recovery. The experimental data can be accurately described by a simple rate-equation model, which accounts for the cooling of the non-radiative states to radiative states. By performing polarization sensitive measurements, we are able to discriminate the contributions of free-carrier absorption from that of intersubband absorption, where the latter is about 50 times more efficient.en667621journal article