The world's smallest laser, contained in a silica sphere just 44 nanometres across, has been unveiled. At about 10 times smaller than the wavelength of light, however, this is no ordinary laser, it is the first ever 'spaser'.
Whereas a laser amplifies light, using a mirrored cavity to intensify it, a spaser amplifies surface plasmons — tiny oscillations in the density of free electrons on the surface of metals, which, in turn, produce light waves.
The spaser could be used as a light source for scanning near-field optical microscopes, which can resolve details beyond the reach of standard light microscopy, and in nanolithography, to etch patterns much smaller than the width of a human hair. The device also opens the door to nanoscale circuits that could process information thousands of times faster than the microelectronic chips inside today's computers.
"This work has utmost significance," says Mark Stockman of Georgia State University in Atlanta, who with David Bergman of Tel Aviv University in Israel proposed the spaser concept in 20031. "The spaser is the smallest possible quantum amplifier and generator of optical fields on the nanoscale — without it, nanoplasmonics is like microelectronics would have been without a transistor."
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