Strong coupling between excitons and light leads to the formation of hybrid states with mixed properties of light and matter. As a result, novel applications are emerging, such as low-threshold polariton lasing [1], ultrafast switching [2], nanoscale quantum devices [3], and the modifications of energy transfer pathways and chemical reactions [4]. In addition, the dynamics of hybrid states composed of molecular excitons include complex physical processes which are currently the subject of much interest [5]. Recently we showed [6] that metasurfaces of aluminum nanoantennas coated with molecular J-aggregates can provide a platform for the formation of strongly coupled exciton-localized surface plasmons. Those metasurfaces can be adapted to work all over the visible regime down to ultraviolet frequencies, can be engineered to control the polarization of the hybrid states and to decrease their mode volume. In order to examine their viability for future applications e.g. for ultrafast switching, the temporal dynamics of the coupled modes have to be studied. Here, we use femtosecond transient absorption spectroscopy to experimentally study the temporal dynamics of the hybrid states and optically induced nonlinearities. We observe that the hybridization with excitons introduces strong ultrafast nonlinearities in the composite metasurfaces, both the reflection and transmission can be manipulated efficiently and very rapidly, which can be useful to generate active metasurfaces-based devices. In the presentation, we will discuss the different decay mechanisms of the excited state dynamics and how detuning and excitation frequency modifies the temporal dynamics and the nonlinearity of the hybrid system.  

References

[1] Kéna-Cohen, S.; Forrest, S. R. "Room-temperature polariton lasing in an organic single-crystal microcavity" Nat. Photonics 4, 371−375 (2010). 

[2] Vasa, P. et al. "Ultrafast manipulation of strong coupling in metal− molecular aggregate hybrid nanostructures" ACS Nano 4, 7559-7565 (2010).

[3] Chikkaraddy, R, et al. "Single-molecule strong coupling at room temperature in plasmonic nanocavities" Nature 535, 127–130 (2016).

[4] Hutchison, J. A.; Schwartz, T.; Genet, C.; Devaux, E.; Ebbesen, T. W. "Modifying chemical landscapes by coupling to vacuum fields" Angew. Chem., Int. Ed. 51, 1592−1596 (2012).

[5] Schwartz, T.; Hutchison, J. A.; Léonard J.; Genet, C.; Haacke, S.; Ebbesen, T. W. " Polariton dynamics under strong light–molecule coupling" ChemPhysChem, 14, 125–131 (2013).

[6] Eizner, E.; Avayu, O.; Ditcovski, R.; Ellenbogen, T. "Aluminum nanoantenna complexes for strong coupling between excitons and localized surface plasmons" Nano Lett. 15, 6215-6221 (2015).