Cascaded exciton-photon coupling in hybrid Tamm plasmon–Fabry-Pérot cavities embedded with perovskite quantum dots

We demonstrate a hybrid photonic architecture in which excitons from CsPbBr₃ quantum dots (QDs) strongly couple with both Tamm plasmon (TP) and Fabry-Pérot (FP) resonances, leading to the formation of hybridized exciton-polariton states. The QDs exhibit a binding energy of ∼61.5 meV, ensuring stable exciton states at room temperature. Reflectance spectrum reveals clear mode anti-crossings and large Rabi splittings exceeding 220 meV, unambiguously confirming strong light-matter coupling. By systematically tuning the cavity spacer thicknesses, the evolution of hybrid upper and lower polariton branches is experimentally mapped and quantitatively described by a coupled-oscillator model. Momentum-resolved spectroscopy further verifies a cascaded coupling process, wherein QD excitons first hybridize with the TP mode and subsequently with the FP mode. The resulting polaritonic states exhibit spectral narrowing, asymmetric emission, and accelerated radiative decay. These findings provide experimental evidence of exciton-polaritons in a TP-FP dual-cavity system and establish a compact, silicon-compatible platform for multifunctional photonic and photoelectronic applications.