Polariton-Polariton Interactions Revealed in a One-dimensional Whispering Gallery Microcavity.

Coulomb interactions are essential to the dynamics and optical properties of exciton-polaritons. Here, we report an experimental observation of polariton-polariton interactions far beyond theory in a one-dimensional whispering gallery microcavity. Based on the unique half-light half-matter nature, we were able to clarify the effects of excitons, quantum confinement, and nonthermalized polariton distribution in the measurements of the polaritonic interactions. Spectacularly, our position-scan and power-scan investigations both revealed that the polariton-polariton interaction strength is up to 2 orders of magnitude larger than theoretical predictions. These results suggest that polaritonic interactions are far more complicated than the expectation and should be re-examined in polariton physics and devices involving polaritonic interactions.