Local excitation of strongly coupled exciton-surface plasmons polaritons by a single nanoantenna

We demonstrate experimentally local coupling of light from free space to exciton-surface plasmon polaritons (X-SPPs). This is achieved by using a single, sub-wavelength gold nanowire on top of a thin silver film which is covered with a 30 nm thick layer of J-aggregating dyes in polyvinyl alcohol. We show that the nanowire acts as an antenna that resonantly scatters light to X-SPPs states with a Rabi splitting of 0.1 eV. The locally excited X-SPPs properties are studied by angle resolved spectroscopy of the far-field leaky photons and are compared to the large-scale response through Kretschmann reflection measurements and to theoretical calculations. The nanowire scattering properties are studied by dark-field scattering measurements and finite-difference time-domain simulations. This method to locally excite X-SPPs can potentially be useful for future applications of hybrid light matter states.