Ultrashort Laser Pulses Squeezed Out of Graphene

Experiments suggest that the carbon sheets can produce beams in broad range of colors

Graphene, hailed as one of the thinnest, strongest and most conductive materials ever found, seems to have bagged one more amazing property. Experiments suggest that it can be used to create ultrashort laser pulses of any color, owing to an ability to absorb light over a broad range of wavelengths.

The discovery could help researchers to build small, cheap and highly versatile ultrashort-pulse lasers, with potential applications ranging from micro-machinery to medicine.

Conventional ultrashort-pulse lasers use a material that absorbs light like a sponge and then releases it back in quick bursts, typically lasting for femtoseconds (one femtosecond is 10?15 seconds, or one millionth of a billionth of a second). These “saturable absorbers” function only at specific wavelengths, says Roy Taylor, a physicist at Imperial College London. Applications such as monitoring pollutants in the atmosphere need to use multiple wavelengths to detect a range of molecules, so several separate lasers are required.

In 2009, physicist Andrea Ferrari of the University of Cambridge, UK, and his collaborators first showed that graphene— a one-atom-thick sheet of carbon, with the atoms arranged in hexagons like chicken wire—can act as a light sponge in the infrared spectrum. More recently, Taylor, Ferrari and colleagues from the United Kingdom and Switzerland have coaxed the material to produce pulses of infrared radiation lasting tens of femtoseconds.

Now, the researchers have improved their device to produce a broad spectrum of infrared wavelengths, which are useful in applications such as fiber optic communications. Moreover, their results, together with the known properties of graphene, suggest that the material should be able to yield similar ultrashort pulses over the entire spectrum of visible light as well, says Ferrari. The team’s latest results will be reported at the Conference on Lasers and Electro-Optics in San Jose, Calif., in June.

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