Self-Hybridized Multimodal Exciton-Polaritons in All-Inorganic Lead Halide Perovskite Microcrystals

Exciton-polaritons are potential avenues for quantum fluids of light and hold great promise for future all-photonic integrated circuits and devices. Herein, self-hybridized multimodal exciton polaritons are investigated in all-inorganic lead halide perovskite microplatelets grown via the space-limited antisolvent crystallization method. Interestingly, the as-grown microcrystals not only exhibit robust excitons at room temperature but also form a photonic microcavity, providing a self-sufficient platform for strong exciton-photon coupling. Resultantly, multiple parabolic dispersions were observed in the angle-resolved photoluminescence mappings, each with a characteristic curvature flattening at large momentum, signifying multimodal polariton formation. The corresponding theoretical fits reveal considerably large Rabi-splitting values of ∼360, 336, and 320 meV for microplatelets of various thicknesses. Such large splitting is attributed to the high (∼perfect) spatial overlap between the excitonic medium and the photonic mode’s electric field. In addition, the variation in the Rabi-splitting as a function of microcrystal thickness demonstrates the facile modulation of exciton-photon coupling strength in self-hybridized systems. Besides, the distinct excitonic and photonic contents of the individual parabolic dispersions suggest the coexistence of polaritons with different compositions. Thus, our results demonstrate a straightforward platform for the realization and manipulation of strong coupling phenomenon crucial for polariton device applications.