Higher Order Optical Magnetic Modes in Dynamic Metamolecules.

Dynamic metamolecules (DMMs) are composed of a dielectric core made of hydrogel surrounded by plasmonic beads that display magnetic resonances when excited by light at optical frequencies. Their optical properties can be controlled by controlling their core diameter by varying temperature. We have recently shown that DMMs display strong optical magnetism, including magnetic dipole and magnetic quadrupole resonances, offering significant potential for novel applications. Here, we use a T-matrix approach to characterize the high order magnetic modes of model metamolecules and confirm the presence of these modes in experiments. We show that higher order modes become prominent as the bead size and the overall structure size grows larger, and when the core size or the inter-bead distance is decreased. We also show that in this limit, mode mixing among these higher order magnetic modes becomes significant in the directional scattering spectrum. We discuss trends in magnetic modes observed in both experiments and simulations and provide suggestions for experimental design and verification of high-order optical magnetic resonances. We demonstrate that the angular scattering of higher-order magnetic modes display Fano-like interference patterns that should be experimentally detactable.