Polarized room-temperature polariton lasing in elliptical microcavities filled with fluorescent proteins

Organic exciton-polaritons, which arise from the strong light-matter coupling between excitons in organic molecules and cavity photons, have emerged as a versatile platform for the investigation of polariton lasing, Bose-Einstein condensation and many-body phenomena at ambient conditions. Here, we study the condensation of exciton-polaritons in fluorescent protein-filled microcavities with elliptical cross-sections. The structural anisotropy of these cavities yields a distinct optical polarization splitting, which we investigate both experimentally and numerically. In the high-density regime of exciton-polaritons, the pronounced polarization splitting of the fundamental polaritonic resonance enforces selective condensation in one linearly polarized polaritonic mode. Our findings constitute a solid basis for polarization engineering in room-temperature polariton condensates.