Pursuing Near-Zero Response

A class of metamaterials designed with low permittivity provides a platform for developing optical devices with unconventional properties. In most wave phenomena, the interplay between the spatial and temporal features of a wave is influenced by the medium in which the wave propagates. For example, the wavelength λ (a spatial feature) and the frequency f (a temporal feature) of a propagating signal are related via the phase velocity v of the wave in the medium as v = f λ. For electromagnetic waves such as radio, microwave, and optical waves, the phase velocity is determined by the medium's electromagnetic parameters of permittivity ε and permeability µ, which is then given as √εμ. When a wave interacts with a structure embedded in a host medium, both these temporal and spatial features play key roles in determining the scattering response of the structure. The recent development of a class of metamaterials in which the electric (ε) and magnetic (µ) properties can be tuned by design is providing a platform to engineer optical devices with unconventional properties.