Two-photon pumped exciton-polariton condensation

Two-photon absorption (TPA) allows accessing “dark” states of matter that are otherwise inaccessible to light, which serve as important building blocks for quantum information processing. In a semiconductor microcavity, TPA-driven condensation of strongly coupled light-matter exciton–polaritons can enable new solid-state quantum simulations of “dark” state-condensate interactions and was predicted to stimulate THz emission. Here, we report the first observation of two-photon-pumped polariton condensation, demonstrated by angle-resolved photoluminescence in a GaAs-based microcavity. TPA is evidenced in the quadratic emission dependence on pump power below and above the condensation threshold, and second-harmonic generation is ruled out by both this threshold behavior and by the emission peak energy showing no dependence on pump photon energy. Our results pave the way toward novel polariton-based sources and solid-state coherent control of collective quantum states with individual two-level systems.