A German-Spanish research team has used gold-covered graphene to generate terahertz pulses more effectively. This is key step for the next generation 6G radio systems as the technology could potentially be integrated into a CMOS chip process.
Researchers working on the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) accelerator found they could use graphene can act as a frequency multiplier. When the two-dimensional carbon graphene is irradiated with light pulses in the low terahertz frequency range, these are converted to higher frequencies. Until now, the problem has been that extremely strong input signals, which in turn could only be produced by a full-scale particle accelerator, were required to generate such terahertz pulses efficiently.
"This is obviously impractical for future technical applications," said Jan-Christoph Deinert of the Institute of Radiation Physics at HZDR. "So, we looked for a material system that also works with a much less violent input, i.e., with lower field strengths."
So the HZDR team worked with researchers at the Catalan Institute of Nanoscience and Nanotechnology (ICN2), the Institute of Photonic Sciences (ICFO), the University of Bielefeld, TU Berlin and the Mainz-based Max Planck Institute for Polymer Research on a new approach, covering the graphene with tiny gold lamellae, or flakes.
"These act like antennas that significantly amplify the incoming terahertz radiation in graphene," said project coordinator Klaas-Jan Tielrooij from ICN2. "As a result, we get very strong fields where the graphene is exposed between the lamellae. This allows us to generate terahertz pulses very efficiently."
To test the idea, team members from ICN2 in Barcelona produced samples. First, they applied a single graphene layer to a glass carrier. On top, they deposited an ultra-thin insulating layer of aluminium oxide, followed by a lattice of gold strips.
The samples were then taken to the TELBE terahertz facility in Dresden-Rossendorf, where they were hit with light pulses in the low terahertz range (0.3 to 0.7 THz). During this process, the team used special