The world’s smallest laser, contained in a silica sphere just 44 nanometres across, and about 10 times smaller than the wavelength of light, has been unveiled.
According to a report in Nature News, the laser has been named as the ‘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,” said Mark Stockman of Georgia State University in Atlanta, who with David Bergman of Tel Aviv University in Israel proposed the spaser concept in 2003.
“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,” he added.
According to Nikolay Zheludev, a physicist at the Optoelectronics Research Centre at Southampton University, UK, “I can think of applications in tagging large biochemical assays and in security marking, where the spaser’s narrow spectral output gives better tagging capacity than existing semiconductor quantum dot emitters.”
Such applications are not far off, according to the US team.
But, Noginov thinks that the spaser’s ability to generate coherent surface plasmons may be even more important than its uses as a nanolaser, and could herald a new generation of ultrafast nanoelectronics.
So far, researchers have made plasmonic circuit elements that serve as wires, resistors and capacitors, but the spaser should enable the development of amplifiers and generators.
For the spaser to have realistic applications in computing, however, researchers need to find a way to make it work electrically using a semiconductor, rather than using light to pump an organic dye.
That would allow the spaser to be integrated with photonic nanocircuitry. According to Stockman, such devices are about a year away.
“There is already a nanolaser with electrical pumping, and its extension to the spaser is very realistic,” he said.