For centuries, artists mixed silver and gold powder with glass to fabricate colorful windows to decorate buildings. The results were impressive, but they didn’t have a scientific reason for how these ingredients together made stained glass. In the early 20th century, the physicist Gustav Mie figured out that the color of a metal nanoparticle is related to its size and the optical properties of the metal and adjacent materials.
Researchers have only recently figured out the missing piece of this puzzle. Medieval glass workers would be surprised to find out they were harnessing what scientists today call plasmonics: a new field based on electron oscillations called plasmons.
Concentrating Light
Plasmonics demonstrates how light can be guided along metal surfaces or within nanometer-thick metal films. It works like this: on an atomic level, metal crystals have a very organized lattice structure. The lattice contains free electrons, not closely associated with the metal atoms, that interact with the light that hits them.
