Researchers at Penn’s school of engineering and applied science, professor Nader Engheta and student, Ashkan Vakil demonstrate how to achieve transformation optics using graphene, which is a lattice of carbon and measures only one atom thick.
They have developed innovative methods to fabricate and make changes to graphene as its exceptional conductivity makes it suitable in the field of electronics. The researchers showed interest in graphene, as it is capable of transporting and guiding EM waves and electrical charges.
Metamaterials research is based on the fact that design of materials is done in such a way that their overall wave qualities depend on the size, shape and pattern of irregularities also called ‘inclusions’. These properties arise by manipulating EM rays in the IR spectrum. Varying the speed, shape and direction of these waves is called transformation optics.
Researchers demonstrated achieving transformation optics by using graphene. The conductive nature of graphene can be varied with respect to EM waves by passing direct voltage to a graphene sheet and by placing a ground plate parallel to the graphene sheet. The conductivity can be altered by changing the voltage or the distance of the graphene sheet with respect to the ground plate.
In this relation between metamaterials and graphene, the various areas of conductivity on the 2D sheet versions with a thickness of one-atom act as the physical inclusions in 3D graphene sheet versions.
With the help of computer models, researchers have shown an example of a sheet of graphene having two regions with different conductivities of which one graphene sheet supports a wave, and another cannot. The boundary line between the two regions serves as a wall, which has the ability to reflect a guided EM wave on the graphene sheet just as in a 3D space.
Another example was demonstrated which showed a graphene sheet that has three distinct regions out of which only one can support a wave. This waveguide thus produced works like a fiber optic cable with a thickness of a single atom. A third example demonstrated dividing the waveguide into two portions, one of which is a non-supporting region.
Source: http://www.upenn.edu/pennnews/