A meta-diffraction-grating for visible light (Vol. 44 No. 5)

Metamaterials — artificially engineered structures with building blocks smaller than the wavelength of light — have delivered a new way to design and make materials with exotic electromagnetic properties. The current challenge is to make these metamaterials into meta-devices that convert the promising research into practical applications. Nanotechnology has made it possible to fabricate ultrathin metamaterials – less than a 15^th of the wavelength – shrinking conventional optical devices into planar form. In the coming years, research in metamaterials, plasmonics and nanofabrication will revolutionize device form and function throughout the electromagnetic spectrum.

This paper reports experimental demonstration of a planar ultrathin (50 nm) gold diffraction grating, mimicking the function of a bulk dielectric grating but tens of times thinner. It uses the resonant properties of individual sub-wavelength meta-atoms to change the phase of the light passing through it, in the same way as a blazed diffraction grating. It functions throughout the visible region of the spectrum (400 – 900 nm), with peak efficiency at 736 nm, and exhibits asymmetric diffraction, sending 25 times more light to the left than the right.