Ultrafast manipulation of the large Rabi splitting in metal-J-aggregate hybrid nanostructures

We study for the first time the effects of strong optical pumping on the optical properties of a strongly coupled hybrid nanostructure. A 50-nm-thick J-aggregated cyanine dye film deposited onto a gold grating, displaying strong exciton-SPP coupling with E_b >; 50 meV is chosen. The effects of the ultrafast pumping on the dispersion relations of the coupled modes are mapped by recording transient angle-resolved low temperature differential reflectivity spectra. Strong optical switching of the sample reflectivity by more than 60% on a 100-fs-timescale and essentially complete external control over E_b, which can be reversibly switched between 0 and 50 meV within 250 fs, is demonstrated. We anticipate that such a pronounced ultrafast control of the exciton-SPP coupling is of considerable interest for different applications such as all-optical switching or SPP amplification.