Fano resonances in the emission spectra of J-aggregate-covered plasmonic nanorods attached to a spherical cavity

We investigate, both experimentally and theoretically, photoluminescence (PL) spectra of J-aggregates (J-agg) covering silver nanorods (AgNRs). When these hybrid nanoparticles (h-NPs), J-agg@AgNRs, hereafter referred to as h-NPs, are deposited on the surface of a spherical microcavity (MC), their non-resonantly excited PL spectra show a series of sharp resonances in the broad spectral range of 550–650 nm, characterized by Fano-type lineshapes. We develop a semi-phenomenological model based on coupled-oscillator equations, which explains the observed spectra of the h-NPs/MC system. In particular, we show that the complex Fano-type lineshapes are due to effective interaction of various whispering gallery modes of the microsphere, coupled to the h-NP emitters. Our experimental results and their understanding qualify the investigated hybrid structure as a sensitive and controllable system, suitable for applications.