Scientists suppress plasmon losses with boron nitride
Graphene encapsulated in BN enables light control in tiny circuits with reduced energy loss
Above: Simulations and observations of propagating plasmons in BN heterostructure
One way of squeezing light into tiny circuits and controlling its flow electrically is to use graphene to guide plasmons, in which electrons and light move together as one coherent wave. However, the plasmons lose energy quickly, limiting the range over which they can travel. Now scientists have shown that combining graphene with the 2D semiconductor boron nitride (BN), can control light in tiny circuits and suppress losses.
The research was carried out by researchers from ICFO (Barcelona), in a collaboration with CIC nanoGUNE (San Sebastian), and CNR/Scuola Normale Superiore (Pisa), all members of the EU Graphene Flagship, and Columbia University (New York).
When graphene is encapsulated in BN, electrons can move ballistically for long distances without scattering, even at room temperature. This research now shows that the graphene/BN material system is also an excellent host for extremely strongly confined light and suppression of plasmon losses.
ICFO Frank Koppens comments: "it is remarkable that we make light move more than 150 times slower than the speed of light, and at lengthscales more than 150 times smaller than the wavelength of light. In combination with the all-electrical capability to control nanoscale optical circuits, one can envision very exciting opportunities for applications."
The research, carried out by PhD students Achim Woessner (ICFO) and Yuando Gao (Columbia) and postdoctoral fellow Mark Lundeberg (ICFO), is just the beginning of a series of discoveries on nano-optoelectronic properties of new heterostructures based on combining different kinds of 2D materials.
The material heterostructure was first discovered by the researchers at Columbia University. James Hone comments: "Boron nitride has proven to be the ideal 'partner' for graphene, and this amazing combination of materials continues to surprise us with its outstanding performance in many areas".
Rainer Hillenbrand from CIC nanoGUNE comments: "Now we can squeeze light and at the same time make it propagate over significant distances through nanoscale materials. In the future, low-loss graphene plasmons could make signal processing and computing much faster, and optical sensing more efficient."
The research team also performed theoretical studies. Marco Polini, from CNR/Scuola Normale Superiore (Pisa) and the IIT Graphene Labs (Genova), laid down a theory and performed calculations together with his collaborators. He explains:"According to theory, the interactions between light, electrons and the material system are now very well understood, even at a fully microscopic level. It is very rare to find a material that is so clean and in which this level of understanding is possible".
The researchers believe ther findings pave the way for miniaturised optical circuits and devices that could be useful for optical and/or biological sensing, information processing or data communications.
