When a stick is dipped in water, it looks as if it is bent because of the change in the direction of light at the surface of the water.
The beam of light enters the metal and is refracted into the opposite direction (left) compared to the usual behavior of light in materials (right)
This tilting is due to the so-called refractive index. For several years, researchers have been working to form unique materials exhibiting a negative refractive index whose optical properties differ from the usual materials. TU Vienna scientists have proved that even normal metals can exhibit a negative refractive index when kept inside a magnetic field.
According to Andrei Pimenov, Professor at the TU Vienna’s Institute for Solid State Physics, the intensity of deflected light can be measured using the refractive index. Researchers trust that studying the properties of specific materials having negative refractive index can pave the way for entirely new technologies and optical effects.
It was recently discovered 'meta-materials' will help to attain these effects. These materials made from tiny intricate structures that can diffract light in a unique manner at a microscopic scale. However, the TU Vienna research team discovered that by simple manipulations even normal metals, for example, iron or cobalt can show a negative refractive index. Andrei explained that a metal was kept in a high-strength magnetic field and used light of accurate wavelength to irradiate it.. Microwave radiation was used because it is capable of penetrating thinner metal foils. At the surface, due to the metal’s magnetic resonance effects, the light bends significantly. However, it changes its direction inside the metal as though the metal had a mirror embedded inside it.
In recent times, materials exhibiting negative diffractive index are gaining attention because of their unique behavior that enables the development of novel types of optical lenses. The light’s wave length restricts the resolution of common lenses. Andrei stated that by utilizing a material showing negative refractive index, a substantially high resolution can be obtained. The fact that simple metals can be used instead of complex metamaterials to obtain a negative refractive index is a major breakthrough.