Thanks to the power of graphene, scientists have isolated light to the size of a single atom.
|Graphene sets a new record on squeezing light to one atom|
In a recent study published in Science, researchers at ICFO — The Institute of Photonic Sciences in Barcelona, Spain, along with other members of the Graphene Flagship, reached the ultimate level of light confinement. They have been able to confine light down to a space one atom, the smallest possible. This will pave the way to ultra-small optical switches, detectors and sensors.
Light can function as an ultra-fast communication channel, for example between different sections of a computer chip, but it can also be used for ultra-sensitive sensors or on-chip nanoscale lasers. There is currently much research into how to further shrink devices that control and guide light.
New techniques searching for ways to confine light into extremely tiny spaces, much smaller than current ones, have been on the rise. Researchers had previously found that metals can compress light below the wavelength-scale (diffraction limit), but more confinement would always come at the cost of more energy loss. This fundamental issue has now been overcome.
“Graphene keeps surprising us: nobody thought that confining light to the one-atom limit would be possible. It will open a completely new set of applications, such as optical communications and sensing at a scale below one nanometer,” said ICREA Professor Frank Koppens at ICFO — The Institute of Photonic Sciences in Barcelona, Spain, who led the research.
This team of researchers including those from ICFO (Spain), University of Minho (Portugal) and MIT (USA) used stacks of two-dimensional materials, called heterostructures, to build up a new nano-optical device. They took a graphene monolayer (which acts as a semi-metal), and stacked onto it a hexagonal boron nitride (hBN) monolayer (an insulator), and on top of this deposited an array of metallic rods. They used graphene because it can guide light in the form of plasmons, which are oscillations of the electrons, interacting strongly with light.
“At first we were looking for a new way to excite graphene plasmons. On the way, we found that the confinement was stronger than before and the additional losses minimal. So we decided to go to the one atom limit with surprising results,” said David Alcaraz Iranzo, the lead author from ICFO.
By sending infra-red light through their devices, the researchers observed how the plasmons propagated in between the metal and the graphene.