Tunable Multiresonant Microcavity Exciton-Polaritons in Colloidal Quantum Wells.

Optical microcavities are widely used to confine photons for exciton-polariton formation. However, their compact design often imposes limitations on spatial freedom, particularly in controlling the cavity length with the nanometer precision required for effective coupling with excitons. Existing methods for tuning resonances by integrating cavities with dynamic structures often lack sufficient resolution or a complex operation. Here, we introduce a multiresonant microcavity array that provides a full spectral selection of cavity resonances with a sub-5 nm cavity length variation. We employed this platform to investigate room-temperature polariton formation using gradient core-crown colloidal quantum wells that host highly stable excitons. The strong coupling system exhibits longevity of Rabi oscillations with a quality factor of = 3.3 and a large Rabi splitting exceeding twice the thermal losses. Notably, we achieved control of the polariton mixed properties across the cavity arrays on a single substrate. This platform is promising for the development of on-chip polaritonic devices.