Multiple Rabi Splitting in Terahertz Nano-Slots Integrated with Organic-Inorganic Hybrid Perovskites

In a strongly coupled light-matter hybrid system, increasing the coupling strength, thereby increasing the Rabi splitting, have profound impact on various nonlinear optical processes and quantum information processing applications. Among many photonic cavity structures, terahertz nano-slot antennas are found to be effective in squeezing the mode volume and increasing the coupling strength, thereby achieving Rabi splitting of record-high 0.48w₀ in an optical phonon mode of an organic-inorganic hybrid perovskite MAPbI₃ at 1 THz. In this study, we find that the nano-slots strongly coupled to the 1 THz phonon also strongly couples with another phonon at 1.85 THz, creating a unique one-light-two-matter polaritonic system with multiple Rabi splitting. Such peculiar phenomenon arises due to an interplay between (1) strong dispersion of MAPbI₃ and (2) dependence of resonance frequency of the nano-slots to the background permittivity of the gap-filling MAPbI₃. Our findings may enable more efficient and complex nonlinear or quantum optical processes in strongly coupled system, such as spontaneous parametric downconversion and quantum gating, etc..