New material system for turning and generating terahertz waves – ScienceDaily

On the electromagnetic spectrum, terahertz light is positioned between infrared and microwave radiation. It has great potential for tomorrow’s technologies: Among other things, 5G could succeed by enabling high-speed mobile communications connections and wireless networks. The bottling in the transition from gigahertz to terahertz frequencies is caused by sources and inverters that are not efficient enough. A German-Spanish research team with the participation of Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has now developed a material system to generate terahertz beats much more efficiently than before. It is based on graphene, i.e., a thin carbon sheet, covered with a metabolic lamellar structure. The research group presented their findings in the journal ACS Nano.

Some time ago, a team of experts working on the accelerator HZDR ELBE was able to show that graphene can be a frequency multiplier: When the bilateral carbon is irradiated by light pulses in the low terahertz frequency range, they are that changed to a higher level. tricead. So far, the problem is that extremely strong input signals, which can be extracted with a full-scale accelerator only, were needed to deliver terahertz beats. thus effectively generated. “This is clearly inconvenient for future technical applications,” is the study’s lead author Jan-Christoph Deinert of the Institute of Radiation Physics at HZDR. “So we looked for a material system that will also work with much more violent inputs, ie, with lower field strengths.”

For this purpose, HZDR scientists, along with colleagues from the Catalan Institute of Geology and Nanotechnology (ICN2), the Institute of Photonic Sciences (ICFO), the University of Bielefeld, TU Berlin and the Max Planck Institute for Polymer Research are established in Mainz, a new idea came up: the frequency conversion could be greatly improved by covering the graphene with tiny gold lamellae, which have an interesting property: “They act as antennas which significantly increases the incoming terahertz radiation in graphene, ”explains 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 beats very efficiently.”

Incredibly effective frequency multiplication

To test the idea, team members from ICN2 in Barcelona made samples: First, they applied one layer of graphene to a glass carrier. On top, they deposited the ultra-thin protective coating of aluminum oxide, and then with a layer of gold strips. The samples were then taken to the TELBE terahertz facility in Dresden-Rossendorf, where they were struck by light pulses in the low terahertz range (0.3 to 0.7 THz). During this process, the experts used special detectors to study how effectively the graphene coated with gold lamellae can propagate the radiation of the event.

“It worked well,” Sergey Kovalev is pleased to report. It relies on HZDR’s TELBE facility. “Compared to untreated graphene, entry signals were much weaker enough to produce a frequency multiplication signal.” Expressed in numbers, only one-tenth of the field strength originally required was sufficient to observe frequency multiplication. And at technically relevant field strengths, the power of the converted terahertz beats is more than a thousand times stronger thanks to the new material system. The wider the individual lamellae and the fewer the areas of graphene left open, the greater the wonder. Initially, the experts were able to triple the incoming frequencies. Later, they achieved even greater effects – five times, seven times, and even nine times in interference frequency.

Compatible with chip technology

This offers a very interesting view, because so far, scientists have been using large, complex devices such as accelerators or large lasers to generate terahertz waves. Thanks to the new material, it may be possible to achieve the jump from gigahertz to terahertz just with electrical input signals, ie, with much less effort. “Our graphene-based metamaterial would be highly compatible with conventional semiconductor technology,” Deinert confirms. “In principle, it could be integrated into standard chips.” He and his team have proven the potential of the new process – now it may be possible to implement it in co-operation. special collections.

The applications could be quite large: Since terahertz waves have higher frequencies than the gigahertz mobile communication frequencies used today, they could be used to transmit much more data without wire distribution – 5G would become 6G. But the terahertz range is also interesting for other areas – from quality control in industry and security scanners at airports to a wide variety of scientific applications in materials research, for example.