The impact of local resonance on the enhanced transmission and dispersion of surface resonances

We investigate the enhanced transmission through the square array of metallic coaxial annular apertures (MCAAs) in microwave frequency by varying the inner diameter of the apertures. The impact of local resonance is thoroughly embodied in the even-mode surface resonances, while the odd-mode surface resonances, invisible in measurements, are only scaled by periodicity. For MCAAs with smaller inner diameters, the transmission extrema are measured at specific incident angles matching the folded degenerate resonant states. The results are well understood in terms of the dispersion of surface resonances.