https://www.sciencedaily.com/releases/2019/11/191120131327.htm

Plasmonics as a magic ingredient

To achieve this, the researchers used a magic ingredient known as "plasmonics." In this technology, light waves are squeezed into structures that are much smaller than the wavelength of the light -- which, according to the laws of optics, should be impossible to do. It can be made possible, however, by guiding the light along the boundary between a metal and a dielectric -- a substance, such as air or glass, that hardly conducts electric current.