MIT engineers have taken control of light emission by successfully coupling properties of two-dimensional materials. The researchers say their technique could pave the way for new light detection strategies, thermal-management systems and even high-resolution imaging devices.
The technique uses a layer of one-atom-thick graphene, which is placed on top of a hexagonal boron nitride (hBN) layer. Despite the structural similarities of the two materials, they each interact with light in different ways. These distinct interactions are actually complementary and offer the engineers control over light`s behavior.
The role of plasmons and phonons
How? Graphene produces particles known as plasmons when it interacts with light, while hBN produces phonons. Combining the materials in a specific way allows the plasmons and the phonons to couple, which produces a powerful resonance.
The combined material blocks light whenever a specific voltage is applied to it. In contrast, it produces a unique emission and propagation called “hyperbolicity” when a different voltage is used. This phenomenon allows the thin sheet of material to interact closely with light, guiding, funnelling and controlling it.
“This poses a new opportunity to send and receive light over a very confined space,” said Nicholas Fang, an MIT associate professor of mechanical engineering. This could lead to “unique optical material that has great potential for optical interconnects,” Fang added.
Improving optical and electronic components
According to his team, improving optical and electronic components is the key to higher-quality computation and imaging systems. “The combination of these two materials provides a unique system that allows the manipulation of optical processes,” said IBM researcher Phaedon Avouris.
Combining graphene with hBN creates an adjustable system that allows light of specific wavelengths or directions to propagate. “We can start to selectively pick some frequencies [to let through], and reject some,” explained graduate student Anshuman Kumar.
Creating tiny wavelengths
Fang says their technique might make it possible to create minuscule optical wavelengths (measuring approximately 20 nanometers). He adds that his research could be used to create microchips that integrate optical and electronic components in one device.
“Our work paves the way for using 2D material heterostructures for engineering new optical properties on demand,” said University of Minnesota researcher Tony Low.
A detailed account of the group`s research was recently published in the journal Nano Letters. For more information, visit MIT's website.