Source: thznetwork.net

Electromagnetic metamaterials are artificial structures that can be engineered to exhibit customizable or conventionally unobtainable electromagnetic properties, such as propagation with near-zero or even negative refractive index. In a material with a negative index, the flow of energy is opposite to the movement of the wavefronts, an effect known as backward-wave or left-handed propagation (so named because the electric field, magnetic field, and wavevector form a left-handed triple). At IR and optical frequencies, left-handed materials can be made by incorporating plasmonic structures into a dielectric. Provided the size and periodicity of the structures is sufficiently small compared to the wavelength, waves propagate as if the medium were uniform with new values for the refractive index (or other bulk properties). Current research in this area investigates electromagnetic metamaterials for novel antenna concepts, sub-wavelength resonators and waveguides, superlenses that beat the diffraction limit, and even cloaking from electromagnetic radiation.

A research group from UCLA has demonstrated a composite left-/right-handed metamaterial waveguide implemented within a THz quantum cascade waveguide. In this way, stimulated emission of THz photons from intraband transitions in the gallium-arsenide-based medium compensates for losses and allows active devices.

Learn more about this from their SPIE News Article.