Enhanced Magnetic Fields at Optical Frequency by Diffraction Coupling of Magnetic Resonances in Lifted Metamaterials

By lifting metamaterials composed of periodic arrays of metallic nanodisk pairs to reduce the effect of substrate, we demonstrate theoretically the diffraction coupling phenomenon of magnetic plasmon (MP) resonances. A narrow-band hybridized mode is observed owing to the strong interactions between MP resonances in individual pairs of metallic nanodisks and a collective surface mode propagating in the array plane. When the hybridized mode is excited, a 5.6-fold enhancement of magnetic fields in nanodisk pairs is obtained as compared with the purely MP resonance. It is also found that for such a diffraction coupling, the magnetic field of the collective surface mode must be parallel to the magnetic moment induced in the paired metallic nanodisks. Our numerical results may find some promising potential applications, like magnetic nonlinearity and sensors.