Metamaterials

Metamaterials are a class of material with widely tunable optical properties and show promise for exotic applications such as negative refractive index materials. They are materials with contrasting permittivity (ε) and permeability (μ) arranged in discrete periods below the diffraction limit. The material period should be much smaller than the wavelength (or wavelength range) of interest such that the impingent radiation experiences effective material properties and can be periodic in one-dimension (1D), two-dimensions (2D), or three-dimensions (3D) to offer control over the effective index of refraction anisotropically.

Metamaterials are commonly characterized by their effective index of refraction, n, where n² = ε.μ. Many examples of metamaterials employ plasmonic metal shapes, using their resonance behaviors to fabricate selective absorbers, emitters, and waveguides.

Due to the nanometer-scale probe size, electron-based excitation, and the recent advent of angle-resolved (ARCL) and wavelength- and angle-resolved (WARCL) modes of operation, cathodoluminescence (CL) proves to be an ideal technique for investigating metamaterials. In the case of the Au-based asymmetric split ring (ASR) resonator metamaterial, CL is useful for observing their emission spectrum and directionality.

References

• Adamo, G.; et al. Phys Rev Let 109, 217401 (2012)