Strong Coupling of Exciton and High-Q Mode in All-Perovskite Metasurfaces

Recently developed halide perovskite semiconductors are viewed as an excellent platform to realize exciton-polariton at room temperature due to their large oscillation strength. Here, the optimized strong coupling between the exciton of perovskite and quasi-bound state in the continuum (QBIC) with high-quality factor (Q-factor), supported by all-perovskite metagrating, including magnetic dipole (MD)-QBIC and toroidal dipole (TD)-QBIC is demonstrated. By taking advantage of extreme electric field confinement enabled by a high-Q mode, it is found that the maximum Rabi splitting can be enhanced up to a record high value of 400 meV, almost twice the Rabi splitting reported in the same perovskite-based subwavelength metasurface. The simulation results reveal that both the Q-factor of QBIC mode and the thickness of the perovskite metasurface play dominant roles in the enhanced strong coupling. It is also demonstrated that adding a protection layer of poly(methyl methacrylate) on the top of the perovskite metagrating has a negligible effect on the maximized Rabi-splitting. These results suggest a new approach for studying exciton-polaritons and may pave the way toward flexible, large-scale, and low-cost integrated polaritonic devices and the realization of polariton lasing at room temperature.