Subwavelength arrays of plasmonic nanoparticles allow us to control the behavior of light at the nanoscale. Here, we develop an eigenmode analysis, employing a coupled electromagnetic dipole formalism, which permits us to isolate the contribution to the far-field radiation of each array mode. Specifically, we calculate the far-field radiation patterns by bulk, edge, and corner out-of-plane eigenmodes in a finite 2D Su-Schrieffer-Heeger (SSH) array of plasmonic nanoparticles with out-of-plane dipolar resonances. The breaking of symmetries in multipartite unit cells is exploited to tailor the optical properties and far-field radiation of the resonant modes. We prove that the antisymmetric modes are darker and have higher Q factors than their symmetric counterparts. Also, the out-of-plane nature of the dipolar resonances imposes that all bulk $\mathrm{\Gamma }$ modes are dark, while corner and edge states need extra in-plane symmetries to cancel the far-field radiation; radiation patterns in turn become more complex and concentrated along the array plane with increasing array size.

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• Plasmonics
• Topological effects in photonic systems
• Nanoparticles
• Polarizability
• Band structure methods
• Bloch wave theory
• Dipole approximation
• Green's function methods
• Su-Schrieffer-Heeger model