Skoltech researchers and their colleagues from KTH Royal Institute of Technology, Sweden, have created an important building block for future 6G communication technology, which will make wireless data transfer at superior transmission rates possible. The newly developed piece of the 6G puzzle is not a device component, but a carbon nanotube-based black paint of sorts that thoroughly absorbs electromagnetic radiation wherever its transmission would be detrimental. The study was reported in an open-access paper in the journal Nature Communications.
Occupying the middleground between infrared light, used in night vision, and microwaves, used to heat your lunch, terahertz radiation is a promising band of electromagnetic waves for 6G communication, advanced biomedical imaging, and sensing.
“The ultrathin single-walled carbon nanotube films we synthesized for this study are similar to those we used previously to create small-scale components such as lenses and antennas. This time it’s not about standalone components. Instead, we show how that same carbon-based material can be leveraged to control electromagnetic radiation in 2D integrated optical circuits, eliminate interference, and enable additional functionality,” said study co-author Associate Professor Dmitry Krasnikov of Skoltech Photonics.
The carbon nanotube-based coating is deployed via aerosol chemical vapor deposition and functions as a thoroughly black paint absorbing terahertz radiation and preventing its propagation in undesirable directions. This comes in handy, for example, for insulating silicon waveguides — structures designed to efficiently transmit electromagnetic signals between various components within a device. The coating serves as a compact way to confine the signal to the waveguide and doubles as a shield for keeping external interference at bay, with the thickest coating exhibiting record-high absorption.
The team evaluated the degree of unwanted signal termination by films ranging in thickness from 2 to 53 nanometers. Films approaching the thicker end of this range proved so effective at insulating the waveguides that even advanced scientific devices could barely detect any signal.
“We have shown that ultrathin coatings based on carbon nanotubes can serve as an effective tool for controlling terahertz radiation. They can be synthesized rapidly and are easily integrated into photonic circuits, making this technology promising for the development of new generations of terahertz devices — from 6G communication systems to sensing and medical technologies,” the director of Skoltech Photonics and study co-author Professor Albert Nasibulin summed up.
Professor Dmitry Lioubtchenko from KTH Royal Institute of Technology, who co-authored the study, emphasized the termination coating’s other applications beyond the realm of 6G: “Electromagnetic shielding can be used to insulate a room or building from telecommunication signals, only allowing electromagnetic radiation of specific wavelengths to pass through. This is relevant for the design of prisons, among other places. Also, considering the prospects of terahertz radiation use in medicine as a safer but probably not entirely harmless alternative to X-rays, we will increasingly need ways to manipulate terahertz waves so as to confine the body’s exposure to a narrow region that is being examined and protect medical personnel.”
