Optical microcavities provide a powerful platform to tailor light–matter interactions and control excitation dynamics in molecular systems. When excitonic materials are embedded in Fabry–Pérot cavities, hybrid light–matter states (polaritons) emerge and reshape relaxation pathways. Using photosynthetic light-harvesting complexes as a model system, we show that cavities modify excitation relaxation and inter-complex energy transfer. In the strong-coupling regime, population dynamics are governed by redistribution between polaritonic branches and dark states, altering lifetimes and transfer efficiencies, while even weak coupling can enhance transfer through cavity-mediated connectivity. We further discuss plexcitons formed by coupling molecular excitons to plasmonic resonances, where interference between electric and magnetic dipolar modes can mimic Rabi splitting. Examples including photonic crystal slabs and chiral plasmonic systems show how nanophotonic environments can enhance nonlinear responses and engineer excitation relaxation and energy transport.

1，Wu, F.; Nguyen- Phan, T. C.; Cogdell, R.; Pullerits, T. Efficient Cavity-Mediated Energy Transfer between Photosynthetic Light Harvesting Complexes from Strong to Weak Coupling Regime. Nat. Commun. 2025, 16, 1–9.

2，Wu, F.; Finkelstein-Shapiro, D.; Wang, M. et al., Optical Cavity-Mediated Exciton Dynamics in Photosynthetic Light Harvesting 2 Complexes. Nat. Commun. 2022, 13, 6864

3，Rosenkampff, I.; Pullerits, T. Microcavity-Enhanced Exciton Dynamics in Light-Harvesting Complexes: Insights from Redfield Theory. J. Chem. Phys. 2025, 163, 044305