Theoretical, numerical study of graphene sheets reveals property that may lead to novel opto-electric devices

Dec 05, 2012
Plasmon energy states in an array of four graphene sheets. Each plane represents different plasmon energy states resulting from different numbers of electrons in each sheet. Credit: 2012 A*STAR Institute of Materials Research and Engineering

One-atom-thick sheets of carbon—known as graphene—have a range of electronic properties that scientists are investigating for potential use in novel devices. Graphene's optical properties are also garnering attention, which may increase further as a result of research from the A*STAR Institute of Materials Research and Engineering (IMRE). Bing Wang of the IMRE and his co-workers have demonstrated that the interactions of single graphene sheets in certain arrays allow efficient control of light at the nanoscale.

Light squeezed between single graphene sheets can propagate more efficiently than along a single sheet. Wang notes this could have important applications in optical-nanofocusing and in superlens imaging of . In conventional , light can be controlled only by structures that are about the same scale as its wavelength, which for is much greater than the thickness of graphene. By utilizing , which are collective movements of electrons at the surface of such as graphene, scientists can focus light to the size of only a few nanometers.

Wang and his co-workers calculated the theoretical propagation of surface plasmons in structures consisting of single-atomic sheets of graphene, separated by an . For small separations of around 20 nanometers, they found that the surface plasmons in the graphene sheets interacted such that they became 'coupled' (see image). This theoretical coupling was very strong, unlike that found in other materials, and greatly influenced the propagation of light between the graphene sheets.

This video is not supported by your browser at this time.
The propagation of surface plasmons. The plasmons move from the bottom of the screen to the top as a function of the angle of incoming light.

The researchers found, for instance, that optical losses were reduced, so light could propagate for longer distances. In addition, under a particular incoming angle for the light, the study predicted that the refraction of the incoming beam would go in the direction opposite to what is normally observed. Such an unusual negative refraction can lead to remarkable effects such as superlensing, which allows imaging with almost limitless resolution.

As graphene is a semiconductor and not a metal, it offers many more possibilities than most other plasmonic devices, comments the IMRE's Jing Hua Teng, who led the research. "These graphene sheet arrays may lead to dynamically controllable devices, thanks to the easier tuning of graphene's properties through external stimuli such as electrical voltages." Graphene also allows for an efficient coupling of the plasmons to other objects nearby, such as molecules that are adsorbed on its surface. Teng therefore says that the next step is to further explore the interesting physics in graphene array structures and look into their immediate applications.

Explore further: A single molecule device for mobile phones

More information: Wang, B., Zhang, X., García-Vidal, F. J., Yuan, X. & Teng, J. Strong coupling of surface plasmon polaritons in monolayer graphene sheet arrays. Physical Review Letters 109, 073901 (2012). prl.aps.org/abstract/PRL/v109/i7/e073901

add to favorites email to friend print save as pdf

Related Stories

Seeing an atomic thickness

May 19, 2011

Scientists from NPL, in collaboration with Linkoping University, Sweden, have shown that regions of graphene of different thickness can be easily identified in ambient conditions using Electrostatic Force ...

Scientists first to observe plasmons on graphene

Jun 20, 2012

With a beam of infrared light, scientists have sent ripples of electrons along the surface of graphene and demonstrated that they can control the length and height of these oscillations, called plasmons, using ...

Writing graphene circuitry with ion 'pens'

Mar 27, 2012

The unique electrical properties of graphene have enticed researchers to envision a future of fast integrated circuits made with the one-carbon-atom-thick sheets, but many challenges remain on the path to commercialization. ...

Recommended for you

A single molecule device for mobile phones

20 hours ago

Researchers from the Delft University of Technology, Groningen University and the FOM Foundation have designed a single molecule which can act as a useful building block in nanometer-size circuits. They found ...

User comments : 0