Gold nano-antennae and ENZ metamaterials for nonlinear optical effects

Negative refraction is a phenomenon in which light exits the interface between two materials with different refractive indices at an angle negative relative to the normal. The coupling of Epsilon Near Zero (ENZ) thin films and gold nano-antennae show promise in creating metamaterials with negative effective refractive indices (neff) and strong nonlinear effects near the ENZ regime. The high surface energy density necessary for negative refraction is achieved when the localized surface plasmon polariton (LSPP) of the gold nano-antennae are tuned to the mode of an ENZ material. In this work, we simulated six gold nano-rod ENZ metamaterials near the ENZ wavelength, where the real part of the permittivity of the ENZ material crossed zero, using the finite-difference time-domain method. We found that well-coupled gold nano-rod metamaterial systems enhanced the surface energy density in the ENZ metamaterials by two orders of magnitude, whereas ENZ film alone saw no magnification of incident light. The large enhancement of energy density via LSPP in metamaterials makes negative refraction more likely to occur, making the system ENZ/nanoparticles the best candidates for near field super-lensing.