Physicists develop optical components for 6G

A joint team of physicists from Skoltech, MIPT and ITMO has developed an optical component that helps to manage the properties of a terahertz beam and split it into multiple channels. The new device can be used as a modulator and generator of terahertz vortex beams in medicine, 6G communications and microscopy. The paper is published in the journal Nature. Advanced Optical Materials.

Terahertz technology is a rapidly evolving technology that transmits signals at about one trillion hertz (1 THz), halfway between the microwave and infrared frequency bands. The technology has applications in medicine as an alternative to X-rays, as well as in high-speed 6G communications. Researchers are currently focusing on creating optics suited to these frequencies, as well as generators that can be used to transmit such signals.

Physicists from MIPT and Skoltech have jointly developed a variable-focus Fresnel zone plate based on carbon nanotubes, which can focus THz radiation and tune its properties by stretching and contracting the plate. In a recent study, the researchers collaborated with ITMO to synthesize an optical component that works in the THz range.

“Together with Skoltech and ITMO, we won the Clover competition for a collaborative research project in photonics to create a spiral zone plate. ITMO made the design calculations for the plate’s shape and behavior, Skoltech synthesized nanomaterials to manufacture plates of the desired shape, and MIPT experimentally tested the plates using facilities of the General Physics Institute of the Russian Academy of Sciences,” said Maria Burdanova, senior researcher at MIPT’s Laboratory of Nano-Optics and Plasmonics.

The new plate, made from a thin film of carbon nanotubes, twists the wavefront of the THz beam passing through it. In their experiments, the team placed two plates side-by-side and rotated them relative to each other, changing the distribution of radiation intensity and splitting the beam into several regions (modes) of different radiation intensity, which can be used as a channel for information transfer.

The team experimentally tested the plate’s properties using a THz imaging method: they aimed a powerful radiation source at the plate and detected the intensity distribution of the electromagnetic field using a 2D raster scanning system based on subwavelength apertures and Golay cells. The researchers used the resulting images to confirm that the plate was generating twisted beams and to check the intensity pattern.

The new modulator is suitable for a variety of applications, including THz microscopy and biomedical, that require beam focusing and repositioning.

“Due to the lack of unified measurement instruments and device standards, exploiting the THz band is a major challenge. At the same time, it opens the door to competitive research and the creation of original solutions. One of the key features that highlights the promising future of carbon nanotubes is the possibility to create multifunctional devices whose properties can be fine-tuned by different effects through responses at the atomic, supramolecular and micron levels.

“For the first time, our joint team has succeeded in introducing an additional effect: the interaction of different nanotube patterns, which paves the way for future devices. Remarkably, this research took less than nine months from the initial idea to proof-of-concept, making it one of the fastest projects of my career so far.”

“This breakthrough would not have been possible without the joint efforts of ITMO, MIPT and Skoltech. It highlights the potential of the SEED program to enhance domestic cooperation among Russian research teams,” commented Dmitry Krasnikov, Associate Professor of Skoltech Photonics.

“Our Clover project has been extended this year. We plan to produce a THz adaptive varifocal device based on the same spiral zone plate with enhanced manipulation capabilities. We also plan to file a patent for the device we already have,” Burdanova added.

In 2023, Skoltech, MIPT and ITMO University launched the Clover Initiative to support joint research and foster cooperation between the country’s three largest universities in the field of photonics. Clover targets students, researchers and postdocs at the start of their scientific careers, engaging them in cutting-edge research projects and facilitating mobility between top research teams.

The long-term goal is to launch a large-scale program in photonics and related fields in Russia. The Clover Competition attracted top researchers working in the fields of biophotonics, advanced photonic materials, topological photonics, optical computing, and laser physics and technology.