Symmetry-Engineered Magnetic Dipole Emission in Plasmonic Core-Satellite Resonators

TL;DR

This paper demonstrates that structural symmetry in plasmonic core-satellite resonators enhances magnetic dipole emission, achieving high Purcell factors and robustness by leveraging symmetry-enforced uniform magnetic modal confinement.

Contribution

It introduces a symmetry-based design principle for nanophotonic resonators that significantly improves magnetic dipole emission and robustness, advancing control over light-matter interactions.

Findings

Dodecapod configuration yields Purcell factors near 250.

Symmetry enforces uniform magnetic modal confinement.

High-symmetry structures suppress electric dipole contributions.

Abstract

Magnetic dipole (MD) transitions are intrinsically weak and highly sensitive to emitter orientation and position, making their controlled enhancement at optical frequencies particularly challenging. Here we show that structural symmetry provides a powerful route to robust magnetic light-matter interactions. We systematically investigate plasmonic core-satellite resonators composed of N metallic nanoparticles arranged on a dielectric core. We evaluate their performance using a unified figure of merit that accounts for magnetic Purcell enhancement, electric dipole suppression, quantum efficiency, and robustness to emitter orientation and fabrication tolerances. We find that the optimal structures correspond to the highest-symmetry geometries, which naturally produce spatially homogeneous and orientation-independent magnetic Purcell enhancement. In particular, the dodecapod configuration yields strong magnetic emission with Purcell factors approaching 250, high radiative efficiency, and suppressed electric dipole contributions. Quasinormal-mode and complex mode-volume analysis reveal that symmetry enforces uniform magnetic modal confinement within the core, explaining both the enhancement and its robustness. These results establish symmetry as a guiding principle for designing nanophotonic resonators with controlled multipolar light-matter interactions and provide a practical route toward bright and selective magnetic dipole emitters.