Metamaterial

Terahertz metamaterial

Metamaterials are artificial materials engineered to have properties that may not be found in nature, such as the ability to interact with and control electromagnetic waves. Naturally occurring matter exhibits behavior based on the molecules that make it up — the atomic material that composes the finished product determines what properties the product will have.

For instance, take the relationship between wood and light. Wood, like all natural matter, reflects and refracts light. But just how much light it reflects and refracts depends on how the electromagnetic waves of the light interact with the particles — like electrons — that make up the wood. With metamaterials, the sum of the parts, not the parts themselves, determines how the material behaves.

Metamaterials usually gain their properties from structure rather than composition, using small inhomogeneities to create effective macroscopic behavior. The primary research in metamaterials investigates materials with negative refractive index (which bend or refract light in unusual and unnatural ways). Negative refractive index materials appear to permit the creation of superlenses (lenes which uses metamaterials to go beyond the diffraction limit – the maximum resolution of an optical system).

In other work, a form of ‘invisibility’ has been demonstrated at least over a narrow wave band with gradient-index materials (accomplished by manipulating the paths traversed by light through a novel optical material). Although the first metamaterials were electromagnetic, acoustic, and seismic metamaterials are also areas of active research.

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