Speaker
Description
Optical microcavities provide a versatile platform for tailoring light–matter interactions and thereby modifying excitation dynamics in molecular systems. In this presentation, we discuss how embedding excitonic materials in Fabry–Pérot microcavities reshapes their relaxation pathways through the formation of hybrid light–matter states, polaritons. Using photosynthetic light-harvesting complexes as a model system, we show how the cavity modifies excitation relaxation and inter-complex energy transfer. In the strong-coupling regime, population dynamics are governed by rapid redistribution between polaritonic branches and dark states, leading to altered lifetimes and transfer efficiencies. Remarkably, even in the weak-coupling regime, cavity-mediated connectivity between spatially separated complexes can enhance energy transfer. The relaxation dynamics can be quantitatively described using rate-equation approaches and Redfield theory, revealing how transfer rates scale with the square of the light–matter coupling strength in accordance with Fermi’s golden rule, while the role of dark states and wavefunction overlaps becomes crucial for understanding the dynamics.
We then turn to plexcitons, hybrid states formed by coupling molecular excitons to plasmonic resonances. We discuss how interference between electric and magnetic dipolar modes leads to Fano-like spectral features that can mimic or compete with genuine Rabi splitting. A rigorous treatment based on non-Hermitian Hamiltonians within the response-function formalism enables clear distinction between interference-dominated and strong-coupling regimes, both in linear and nonlinear
spectroscopy.
Finally, we present recent results on chiral plexcitonic systems based on helicoidal plasmonic nanostructures coupled to molecular J-aggregates. Here, helicity-dependent interference between electric and magnetic dipole channels governs both steady-state spectra and ultrafast relaxation dynamics.
Together, these examples illustrate how optical and plasmonic cavities provide powerful means to engineer excitation relaxation, energy transport, and nonlinear optical response.
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.
Wu, F.; Finkelstein-Shapiro, D.; Wang, M.; Rosenkampff, I.; Yartsev, A.; Pascher, T.; Nguyen- Phan, T. C.; Cogdell, R.; Börjesson, K.; Pullerits, T. Optical Cavity-Mediated Exciton Dynamics in Photosynthetic Light Harvesting 2 Complexes. Nat. Commun. 2022, 13, 6864
Rosenkampff, I.; Pullerits, T. Microcavity-Enhanced Exciton Dynamics in Light-Harvesting Complexes: Insights from Redfield Theory. J. Chem. Phys. 2025, 163, 044305