Integrated array of coupled exciton–polariton condensates

A central challenge for advancing polaritonbased circuits is the controlled and scalable coupling of individual condensates. Existing approaches based on etched
or epitaxially grown microcavities are fabrication-intensive and restrict in-plane coupling. To overcome these limitations, we introduce a lithographically defined silicon-
based platform of high-contrast grating (HCG) microcavities with a ladder-type π-conjugated polymer. In this system, doublet cavities exhibit mode hybridization into bonding and antibonding states, where coupling is mediated across shared HCG mirrors. Extending the design to arrays, N-coupled condensates exhibit systematic red-shifts of the condensate energy, due to delocalization, and a progressive threshold reduction, consistent with extended binding modes. Our experimental results are quantitatively sup-
ported by transition-matrix multi-scattering simulations, together with tight-binding modelling. First-order coherence measurements using Michelson interferometry con-
firm the existence of spatially extended condensates with exponentially decaying temporal coherence. Altogether, these results establish a scalable route toward integrated polariton devices and quantum photonic networks.