Amsterdam and US scientists create world’s thinnest lens

Researchers from the University of Amsterdam and Stanford University have constructed a lens that’s just a single atomic layer thick. Consisting of concentric tungsten disulfide (WS₂) rings, the so-called Fresnel lens focuses light through diffraction rather than refraction. The size of and distance between the rings determines the lens’s focal length. The researchers tested a design that focuses red light 1 millimeter from the lens.

The lens is particularly efficient at certain wavelengths because of the formation of excitons. These electron-hole pairs aid absorption and efficient re-emission of incoming photons. The scientists detected a clear peak in lens efficiency for the specific wavelengths of light sent out by the excitons. While the effect is already observed at room temperature, the lenses are even more efficient when cooled down.