Aluminum Nanoantenna Complexes for Strong Coupling between Excitons and Localized Surface Plasmons

We study the optical dynamics in complexes of aluminum nanoantennas coated with molecular J-aggregates and find that they provide an excellent platform for the formation of hybrid exciton-localized surface plasmons. Giant Rabi splitting of 0.4 eV, which corresponds to ∼10 fs energy transfer cycle, is observed in spectral transmittance. We show that the nanoantennas can be used to manipulate the polarization of hybrid states and to confine their mode volumes. In addition, we observe enhancement of the photoluminescence due to enhanced absorption and increase in the local density of states at the exciton-localized surface plasmon energies. With recent emerging technological applications based on strongly coupled light–matter states, this study opens new possibilities to explore and utilize the unique properties of hybrid states over all of the visible region down to ultraviolet frequencies in nanoscale, technologically compatible, integrated platforms based on aluminum

Temporal Dynamics of Localized Exciton–Polaritons in Composite Organic–Plasmonic Metasurfaces

We use femtosecond transient absorption spectroscopy to study the temporal dynamics of strongly coupled exciton–plasmon polaritons in metasurfaces of aluminum nanoantennas coated with J-aggregate molecules. Compared with the thermal nonlinearities of aluminum nanoantennas, the exciton–plasmon hybridization introduces strong ultrafast nonlinearities in the composite metasurfaces. Within femtoseconds after the pump excitation, the plasmonic resonance is broadened and shifted, showcasing its high sensitivity to excited-state modification of the molecular surroundings. In addition, we observe temporal oscillations due to the deep subangstrom acoustic breathing modes of the nanoantennas in both bare and hybrid metasurfaces. Finally, unlike the dynamics of hybrid states in optical microcavities, here, ground-state bleaching is observed with a significantly longer relaxation time at the upper polariton band

Organic Photodiodes with an Extended Responsivity Using Ultrastrong Light–Matter Coupling

In organic photodiodes (OPDs), light is absorbed by excitons that dissociate to generate photocurrent. Here, we demonstrate a novel type of OPD in which light is absorbed by polaritons, hybrid light–matter states. We demonstrate polariton OPDs operating in the ultrastrong coupling regime at visible and infrared wavelengths. These devices can be engineered to show narrow responsivity with a very weak angle-dependence. More importantly, they can be tuned to operate in a spectral range outside that of the bare exciton absorption. Remarkably, we show that the responsivity of a polariton OPD can be pushed to near-infrared wavelengths, where few organic absorbers are available, with external quantum efficiencies exceeding those of our control OPD