Bose-Einstein condensation of polaritons at room temperature in a GaAs/AlGaAs structure

We report the observation of Bose-Einstein condensation (BEC) of polaritons in the weak coupling regime at room temperature in a GaAs/AlGaAs microcavity structure, demonstrating effects previously seen only at low temperatures. Although GaAs-based structures were believed unsuitable for room-temperature condensates due to the low exciton binding energy (∼10 meV) in quantum wells, we show that polaritons can still form through exciton-photon coupling, despite phonon-induced exciton broadening. In this experiment, we used a GaAs/AlGaAs microcavity where the cavity photon energy closely matches the quantum well exciton energy at room temperature and observed the signatures of polariton condensation. These include a nonlinear energy shift and significant line narrowing, with coherent emission exhibiting a spectral width of 0.24 meV. The lower polariton line has a half-width of 0.69 meV, and the system shows strong nonlinearity, opening the door to room-temperature optical transistors and nonlinear optical devices based on polariton condensation.