World's smallest laser created by scientists

he breakthrough heralds a revolution in optical technology, paving the way to ''nanolasers'' that can probe and manipulate DNA, and super-fast computers and telecommunications.

''This work shatters traditional notions of laser limits, and makes a major advance toward applications in the biomedical, communications and computing fields,'' said Professor Xiang Zhang, who led the US team.

The new ''plasmon'' laser compresses light into a gap five nanometres wide, the size of a single protein molecule.

A key step forward was the ability to confine light in such a small space long enough for it to stabilise into a ''coherent'' laser state, with all its waves in step.

Plasmons are the wave-like motions of excited electrons on the surfaces of metals. Binding light to these oscillations allows it to be squeezed much further than would normally be the case.

''Plasmon lasers represent an exciting class of coherent light sources capable of extremely small confinement,'' said Prof Zhang, from the University of California (UC) at Berkeley.

''This work can bridge the worlds of electronics and optics at truly molecular length scales.''

The scientists hope one day to shrink light down to the size of an electron's wavelength, about a nanometre, or one billionth of a meter.

Nanolasers could replace electronic circuits with optical ones that are much faster and more efficient.

The research was reported in the online version of the journal Nature.

Co-author Dr Thomas Zentgraf, from the same laboratory at UC Berkeley's Nanoscale Science and Engineering Centre, said: ''The advantages of optics over electronics are multifold. For example, devices will be more power efficient at the same time they offer increased speed or bandwidth.''

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