How would you react if a tiny hole in a piece of foil let through more light after you had covered it – or painted the foil a different colour?
With surprise, probably, like the physicists who discovered that this is just what happens with some very small holes. Both findings could lead to light-based transistors and other components for high-speed optical computers.
Conventional optics forbids light from passing through holes that are much smaller than its wavelength, which for visible light means less than around 400 nanometres wide. But in 1998, Thomas Ebbesen at the University of Strasbourg, France, reported that some wavelengths of visible light stream through holes in gold foil that are less than 300 nanometres wide.
It turns out that this is due to ripples known as plasmons that are found on the surface of metals and formed by the oscillation of electrons.
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