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Description
A detailed understanding of polariton composition is essential for unraveling the mechanisms underlying polaritonic chemistry. This work addresses vibropolaritons formed by infrared-active molecules in Fabry-Pérot cavities. In most theoretical descriptions, the polariton composition is modeled using the Jaynes–Cummings framework, or its extension to many emitters, the Tavis–Cummings model. However, the dispersive nature of the cavity modes is often neglected. We present a model that explicitly incorporates multiple cavity normal modes together with their dispersion relations within a single Hamiltonian framework. This treatment reveals a significantly richer polariton composition than predicted by conventional models. In particular, individual lower and upper polariton states within the polariton bands are shown to arise from coherent superpositions of several cavity modes. Remarkably, the contributing modes may originate from different dispersion branches. Our findings suggest that individual polariton states can be selectively accessed under different external illumination angles. Moreover, our results indicate that photon absorption and re-emission between cavity modes plays an important role in the formation of vibropolaritons in Fabry-Pérot cavities. This mechanism leads to a more intricate polariton composition.
In addition, the multimode character of the polaritonic states manifests itself in nontrivial spatial structures of the electromagnetic field, governed by the underlying cavity mode functions. The coherent superposition of modes with distinct wavevectors and dispersion branches gives rise to spatial interference patterns, including speckle-like intensity distributions.