Smallest nanolaser 'built'

Scientists claim to have for the first time built the smallest room-temperature nanolaser to date and a "no-waste" laser, which require very low power for operation.

A team at the University of California says that the second one is a highly efficient "thresholdless" laser that funnels all its photons into lasing, without any waste, the 'Nature' journal reported.

A laser's threshold is the point where this coherent output is greater than any spontaneous emission produced.

Moreover, the two new lasers are a key breakthrough since lasers usually require greater and greater "pump power" to begin lasing as they shrink to nano sizes.

"The small size and extremely low power of these nanolasers could make them very useful components for future optical circuits packed on to tiny computer chips," Mercedeh Khajavikhan, who led the team, said.

The scientists claim that the thresholdless laser may also help develop new metamaterials, artificially structured materials that are already being studied for applications from super-lenses that can be used to see individual viruses.

"All lasers require a certain amount of 'pump power' from an outside source to begin emitting a coherent beam of light or 'lasing'," said team member Yeshaiahu Fainman.

Fainman said other applications for the new lasers could include tiny biochemical sensors or high-resolution displays, but the scientists are still working out the theory behind how these tiny lasers operate. They would also like to find a way to pump the lasers electrically instead of optically.