Photonic Circuits Get a Boost from Combination of 2-D Materials

Novel material can both squeeze light and propagate it over signficant distances

Illustration: ICFO

Recently the field of plasmonics—which exploits the surface plasmons generated when photons hit a metal structure—has opened up the real possibility that photonic circuits could duplicate what electronic ICs do.  Previously, photonic circuits were just too large to be functional because of their need to accommodate different wavelengths of light.

Despite several advances, the plasmons still lost energy too quickly, which reduced the distance they could travel.  Now researchers in Spain, Italy, and the United States have developed a solution to this issue by combining graphene and boron nitride.

It has been known that when graphene is encapsulated in boron nitride, electrons can move ballistically for long distances without scattering, even at room temperature.

In this latest research, the international team—representing the Institute of Photonic Sciences (ICFO) in Barcelona, CIC nanoGUNE in San Sebastian, Spain, CNR/Scuola Normale Superiore in Pisa, Italy (all members of the EU Graphene Flagship), plus Columbia University in New York City—discovered, somewhat surprisingly, that the combination of graphene sandwiched between two films of hexagonal ​boron nitride (h-BN) is an excellent host for extremely strongly confined light and quite capable of suppressing of plasmon losses.

"It is remarkable that we make light move more than 150 times slower than the speed of light, and at length scales more than 150 times smaller than the wavelength of light,” said ICFO’s Frank Koppens, in a press release. “In combination with the all-electrical capability to control nanoscale optical circuits, one can envision very exciting opportunities for applications."

Columbia University has been at the forefront of creating these heterostructures by combining graphene and boron nitride since 2013. This latest research is seen as just an initial step in investigating the nano-optoelectronic properties of combining different two-dimensional materials.

"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,” said Columbia University professor James Hone, in a press release.

In May of last year, researchers from CIC nanoGUNEand ICFO, along with the company Graphenea, demonstrated that an optical antenna made from graphene can capture infrared light and transform it into plasmons.

Rainer Hillenbrand from CIC nanoGUNE believes this latest research represents a significant advance in optoelectronics.

“Now we can squeeze light and at the same time make it propagate over significant distances through nanoscale materials, said Hillenbrand in the press release. “In the future, low-loss graphene plasmons could make signal processing and computing much faster, and optical sensing more efficient."

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