Super-plasmonic cavity resonances in arrays of flat metallic nanoantennas

摘要

We show that when flat strip-like metallic nanoantennas are arranged in a one-dimensional array, coupling of their edge modes can lead to the formation of a super-plasmonic cavity resonance. Such a resonance is extended along the whole array and is characterized by anomalously high order standing waves in each nanoantenna. The super-plasmonic resonance is generated when the nanoantennas are close to each other along their long axes, forming a one-dimensional periodic gap array. When the incident light is polarized along the short axes of these nanoantennas (transverse polarization), at a certain wavelength, the edge modes of the neighboring nanoantennas are coupled to each other through routes that encircle the gaps. The super-plasmonic resonance occurs as such a process enforces a significantly high order collective mode which is not supported by isolated metallic nanoantennas. We demonstrate that when such an array is utilized as a unit cell in a lattice, the coherent light scattering between these cells can enhance such a resonance while forming a unique surface lattice mode with a sharp optical feature.