Strong coupling of polaritons at room temperature in a GaAs/AlGaAs structure

We report direct measurement of the dispersion relation of polaritons in GaAs/AlGaAs microcavity structures at room temperature, which clearly shows that the polaritons are in the strong-coupling limit. The Rabi splitting ranges from 12.3 to 15.2 meV depending on the detuning, significantly exceeding the heavy-hole exciton half width of 5.2 meV. As the polariton density increases, the Rabi splitting decreases; but even when the polariton gas becomes a coherent, Bose-condensate-like state, the polaritons retain a strong exciton component, as seen in the nonlinear energy shift of the light emission. This opens up the possibility of polaritonic devices at room temperature in a material system which can be grown with very high quality and uniformity.