metamaterial gives Visible light negative refraction

The race to build an exotic material with a negative refractive index for visible light has been won by a team of researchers in Germany. The demonstration could open the door to a new generation of optical devices such as superlenses able to see details finer then the wavelength of visible light.

Dolling’s metamaterial is made by depositing a layer of silver on a glass sheet, covering this with a thin layer of nonconducting magnesium fluoride, followed by another silver layer, forming a sandwich 100 nm thick. Dolling then etched an array of square holes through the sandwich to create a grid, similar to a wire mesh.

Dolling determined the refractive index of the material by measuring the “phase velocity” of light as it passed through. His measurements show the structure has a negative refractive index of -0.6 for light with a wavelength of 780 nm.

This value drops to zero at 760 nm and 800 nm, and becomes positive at longer and shorter wavelengths. Previously, the shortest wavelength at which a negative refractive index had been demonstrated was 1400 nm.

The team has not yet observed some of the other exotic effects possible with a negative refractive index, such as the ability to bend light backwards. However, simulations show that negative-index lenses should produce exotic effects over a limited range of wavelengths. For now, Dolling is concentrating on studying the new effects rather than attempting to build devices such as superlenses.

metamaterial
superlenses
visible light metamaterial
negative index of refraction

Subscribe on Google News