Making optical computing a possibility again? (Image: Jeffrey Coolidge/Getty)

IT’S a laser, but not as we know it. For a start, you need a microscope to see it. Gleaming eerily green, it is a single spherical particle just a few tens of nanometres across.

Tiny it might be, but its creators have big plans for it. With further advances, it could help to fulfil a long-held dream: to build a super-fast computer that computes with light.

Dubbed a “spaser”, this minuscule lasing object is the latest by-product of a buzzing field known as nanoplasmonics. Just as microelectronics exploits the behaviour of electrons in metals and semiconductors on micrometre scales, so nanoplasmonics is concerned with the nanoscale comings and goings of entities known as plasmons that lurk on and below the surfaces of metals.

To envisage what as plasmon is, imagine a metal as a great sea of freely moving electrons. When light of the right frequency strikes the surface of the metal, it can set up a wavelike oscillation in this electron sea, just as the wind whips up waves on the ocean. These collective electron waves – plasmons – act to all intents and purposes as light waves trapped in the metal’s surface. Their wavelengths depend on the metal, but are generally measured in nanometres. Their frequencies span the terahertz range – equivalent to the frequency range of light from the ultraviolet right through the visible to the infrared.

Gleaming eerily green, this laser is a single spherical particle just tens of nanometres across

In 2003, their studies of plasmons led theorists Mark Stockman at Georgia State University in Atlanta and David …