On the Radiative Emission and Excitation Rate of Quantum Emitters in Plasmonic Nanostructures

Plasmonic nanocavities are usually formed by two tightly-coupled metallic structures and have been established as the ideal photonic environment to observe extreme lightmatter interactions. However, they support multiple modes of large bandwidth that can interfere with each other and often lead to unusual behaviours. Using a multipolar decomposition of the system’s modes we show that, for plasmonic structures beyond the quasi-static limit, an emitter radiates energy much more efficiently than a plane wave couples energy into the antenna. These results significantly impact our understanding and interpretation of the light-matter dynamics measured experimentally in the far-field.