Enhancing the Magnetic Resonance via Strong Coupling in Optical Metamaterials

Abstract Due to the lack of symmetry between electric and magnetic charges, the magnetic effect in optical materials is usually very weak. Recently, Fano type magnetic resonances have been proposed and experimentally realized by packaging the metallic nanoparticles into metamolecules. However, the corresponding experiments are hard to be realized and the enhancements of magnetic fields are relatively low. Here, a simple way is demonstrated experimentally to generate magnetic plasmon polaritons (MPPs) in optical metamaterials. By changing the period of the nanostructures, strong coupling between the magnetic resonance and the propagating surface plasmon polaritons (SPPs) with a Rabi‐splitting around 190 meV has also been observed. Interestingly, the hybrid modes around the avoided resonance crossing points are found to be mixtures of MPPs and SPPs. Consequently, the typical long‐lived SPPs are also well localized within the dielectric spacer layer and give an enhancement in magnetic field around 500 times. In addition, the dependence of MPPs has also been observed on the refractive index with a sensitivity around 470 nm RIU⁻¹, which is very close to the typical reports of electric resonances in plasmonic nanostructures. This research shall pave a new way to the developments of magnetic light sources and magnetic sensing.