Time-of-flight measurement of excitonic polaritons in a GaAs/AlGaAs quantum well

Abstract

We report the first experimental observation of excitonic polaritons in a GaAs/AlGaAs quantum well with incident light propagating parallel to the quantum well layer. We have built a time-of-flight measurement system which allows us to investigate low-temperature optical properties of semiconductor waveguides with picosecond time resolution. This system has been used to measure propagation delay time of an incident light pulse transmitted through the quantum well. The delay time increases drastically near the photon energies resonant to the optical absorption lines of the quantum well excitons. This behavior shows that the group velocity of the light pulse decreases as a result of the formation of quantum well excitonic polaritons. The group velocity drops to 7×104 m/s at a heavy-hole exciton absorption line at 6.0 K.