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Scientists build a nanolaser using a single atomic sheet

25 March 2015

University of Washington (UW) scientists have built a new nanometre-sized laser using a tungsten-based semiconductor only three atoms thick.

The ultra-thin semiconductor stretches across the top of the photonic cavity (image: University of Washington)

Lasers play essential roles in countless technologies, but to meet modern needs in computation, communications, imaging and sensing, scientists are striving to create smaller laser systems that also consume less energy.

The UW nanolaser, developed in collaboration with Stanford University, uses a tungsten-based semiconductor only three atoms thick as the 'gain material' that emits light. The technology is described in a paper published in the March 16 online edition of Nature.

“This is a recently discovered, new type of semiconductor which is very thin and emits light efficiently,” says the paper's lead author, Sanfeng Wu. “Researchers are making transistors, light-emitting diodes, and solar cells based on this material because of its properties. And now, nanolasers.”

Nanolasers have the potential to be used in a wide range of applications from next-generation computing to implantable microchips that monitor health problems. But so far they have been confined to the research lab.

Other nanolaser designs use gain materials that are either much thicker or that are embedded in the structure of the cavity that captures light. That makes them difficult to build and to integrate with modern electrical circuits and computing technologies.

The UW version uses a flat sheet that can be placed directly on top of a commonly used optical cavity, a tiny cave that confines and intensifies light. The ultra-thin nature of the semiconductor — made from a single layer of a tungsten-based molecule — yields efficient coordination between the two key components of the laser.

The UW nanolaser requires only 27 nanoWatts to kick-start its beam, which means it is very energy efficient. Other advantages are that it can be easily fabricated, and can potentially work with silicon components common in modern electronics. Using a separate atomic sheet as the gain material offers versatility and the opportunity to more easily manipulate its properties.

With other materials, the gain medium is embedded and it can’t be changed. In the UW nanolasers, the monolayer can be removed or replaced. The researchers hope this and other recent innovations will enable them to produce an electrically-driven nanolaser that could open the door to using light, rather than electrons, to transfer information between computer chips and electronic circuit boards.

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