Observation of strong coupling and optical nonlinearity in GaAs structures at room temperature

We present direct measurements of the dispersion relation of polaritons in GaAs/AlGaAs microcavity structures from 200 K to room temperature, demonstrating the strong coupling regime at room temperature despite the low exciton binding energy of 10 meV. While thermal energy at room temperature suggests a significant free carrier population that could screen excitonic effects, our results show that strong coupling persists at high excitation densities. As the polariton density increases, the Rabi splitting decreases, yet even in a coherent, Bose-condensate-like state, the polaritons maintain a strong exciton component, evidenced by the nonlinear energy shift of the emission. At higher densities, a threshold is reached where the system collapses to weak coupling, though exciton/electron-hole optical interactions remain significant. These findings highlight the potential for room-temperature polaritonic devices in a material system known for its high-quality growth and uniformity, as well as applications in nonlinear optical switching.