Strong exciton-photon coupling in self-hybridized organic-inorganic lead halide perovskite microcavities.

Controlling coherent light-matter interactions in semiconductor microcavities is at the heart of the next-generation solid-state polaritonic devices. Organic-inorganic hybrid perovskites are potential materials for room-temperature polaritonics owing to their high exciton oscillator strengths and large exciton binding energies. Herein, we report on strong exciton-photon coupling in the micro-platelet and micro-ribbon shaped methylammonium lead bromide single crystals. Owing to high crystallinity and large refractive index, the as-grown perovskite microcrystals serve as self-hybridized optical microcavities along different orientations due to their distinct physical dimensionalities. In this regard, the perovskite micro-platelet forms a simple Fabry-Perot microcavity in out-of-plane orientation, while the micro-ribbon functions as a Fabry-Perot type waveguide microcavity within the plane of the perovskite sample. Consequently, excitons in these microcavities strongly interact with their corresponding uncoupled cavity modes, yielding multimode exciton-polaritons with Rabi splitting energies ∼205 and 235 meV for micro-platelet and micro-ribbon geometry, respectively. Furthermore, micro-ribbon geometry displays Young's double-slit-like interference patterns, which together with the numerical simulation readily reveals the parity and the mode order of the uncoupled cavity modes. Thus, our results not only shed light on strong exciton-photon coupling in various morphologies of methylammonium lead bromide microcrystals but also open an avenue for advanced polaritonic devices.