Near-field-coupled lighting-rod effect for emissivity or absorptivity enhancement of 2-D (1, 2) magnetic plasmon mode by rotating the square resonators array

Comparing to the 1-D resonators like strips, the 2-D resonators, such as squares, can excite the higher-order 2-D magnetic plasmon (MP) modes in addition to the fundamental and higher-order 1-D MP modes. However, the low absorptivity of 2-D MP modes greatly limits its applications. We propose and demonstrate an idea utilizing the near-field coupling of electromagnetic fields accumulated around the tips of 2-D square resonators (near-field-coupled lighting-rod effect) to enhance the electromagnetic fields intensity and the emissivity or absorptivity of 2-D MP modes. The tip-tip coupling structure is formed by rotating the square resonators array 45°. The experiment demonstrates the 4.5 times absorptivity enhancement of higher-order 2-D (1, 2) MP mode from 12.5% to 55.8% in addition to the fundamental MP₁₀ and higher-order 1-D MP₃₀ modes with high absorptivity. Our proposed near-field-coupled lighting-rod effect is strongly dependent on the formation of tip-tip coupling structure and the coupling distance.