Negative index meta-materials based on two-dimensional metallic structures

The electromagnetic properties of two-dimensional metallic nanostructures in the optical frequency range are studied. One example of such a structure is a periodic array of thin metallic strip pairs. The magnetic response of these structures is studied, as is the closely related emergence of the negative index of refraction propagation bands. The presence of such bands is found to critically depend on the proximity of electric and magnetic dipole resonances. It is demonstrated that the frequencies of those resonances are strongly dependent on the ratio of the structure thickness and the plasmonic skin depth. Electromagnetic structures that are much thicker than the plasmonic skin depth are shown to exhibit standard broad antenna resonances at the wavelength roughly twice the strip length. As the structures are scaled down to resonate in the visible/mid-infrared, electrostatic resonances determine the electromagnetic properties of such materials.