Ultrashort Laser Pulses Squeezed Out of Graphene
Graphene’s hexagonal lattice of carbon atoms can take in laser light like a sponge and then launch it in bursts long lasting just a portion of a nanosecond.
Graphene, hailed as a single of the thinnest, strongest and most conductive supplies at any time located, looks to have bagged one particular much more wonderful residence. Experiments advise that it can be utilized to generate ultrashort laser pulses of any color, owing to an ability to take up mild more than a broad assortment of wavelengths.
The discovery could support scientists to create modest, low-cost and extremely flexible ultrashort-pulse lasers, with prospective applications ranging from micro-equipment to medicine.
Standard ultrashort-pulse lasers use a substance that absorbs light-weight like a sponge and then releases it again in rapid bursts, typically lasting for femtoseconds (1 femtosecond is 10−15 seconds, or one particular millionth of a billionth of a next). These “saturable absorbers” perform only at certain wavelengths, says Roy Taylor, a physicist at Imperial College London. Purposes such as checking pollutants in the atmosphere need to use multiple wavelengths to detect a assortment of molecules, so numerous separate lasers are required.
In 2009, physicist Andrea Ferrari of the College of Cambridge, United kingdom, and his collaborators initial confirmed that graphene— a a single-atom-thick sheet of carbon, with the atoms arranged in hexagons like chicken wire—can act as a mild sponge in the infrared spectrum. More just lately, Taylor, Ferrari and colleagues from the United Kingdom and Switzerland have coaxed the materials to make pulses of infrared radiation lasting tens of femtoseconds.
Now, the researchers have improved their gadget to make a wide spectrum of infrared wavelengths, which are useful in applications this sort of as fiber optic communications. Additionally, their outcomes, collectively with the acknowledged qualities of graphene, advise that the material should be able to generate related ultrashort pulses more than the total spectrum of seen light as effectively, claims Ferrari. The team’s most recent final results will be documented at the Meeting on Lasers and Electro-Optics in San Jose, Calif., in June.
Graphene’s capability to absorb mild of any coloration comes from the peculiar construction of the power stages of its electrons. In a typical sound non-metallic materials, electrons can exist in a low-energy condition, in which they are sure to atoms, or in a greater-vitality condition, in which they are in a position to go about and carry an electric powered existing. Amongst these two states is a “band hole,” which calls for a specified energy to be bridged. An electron can cross the band hole if the material absorbs light with that particular energy—which implies a particular wavelength. In the semiconductor supplies employed to make transistors in computer chips, electrons leaping more than the band hole change the present from “off” to “on.”
In graphene, by distinction, there is no band hole, and the electrons’ power can fluctuate alongside a continuum. That tends to make solitary-sheet graphene worthless in transistors, says Byung Hee Hong, a physicist at Seoul National College, but it offers the material an benefit in optics, enabling it to take in a vast variety of wavelengths of light.
“Usually, distinct resources are required for various wavelengths, and there are not many [standard] components that can be utilised for the in close proximity to-infrared location,” says Hong, who was not involved in the new review.
Graphene is also chemically and mechanically steady ample to avert thermal injury by powerful laser beams, Hong provides. And a significant edge of graphene-primarily based ultrashort-pulse lasers is that these devices can be as little as a pencil, producing them adaptable and easy to use.
This write-up is reproduced with permission from the journal Character. The report was initial released on May possibly 24, 2013.