Speed and flexibility, Terahertz and visible light conversion for future communications
A study from Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Catalan Center for Nanoscience and Nanotechnology (ICN2), Center for Graphene Science at the University of Exeter and TU Eindhoven shows that materials based on graphene can be used to successfully convert high-resolution signals into visible light, Speed and flexibility that this process is critical and reflective, as the group shows their findings in Nano Letters (DOI: 10.1021 / acs. nanolett.3c00507).
Speed and flexibility, these results pave the way for exciting applications in the information and communication technologies of the near future.
The ability to convert signals from one frequency system to another is a key feature of various technologies, especially in communications, where for example, electronic data is often transmitted as optical signals through fiber optic cables.
In order to achieve higher data transfer rates, 6G wireless communication systems will need to extend frequencies beyond 100 gigahertz into the terahertz range.
Terahertz waves are part of the electromagnetic spectrum that lies between microwaves and infrared light.
However, terahertz waves can be used to transmit data over the air over very limited distances. “Therefore, a fast and controlled system will be needed to convert terahertz waves into visible or infrared light, which can be transmitted through optical fibers.
Imaging and detection technologies can also benefit from such a process,” explains Dr. Igor Ilyakov from the Institute of Radiation Physics at HZDR. What is missing now is a material that can convert the photon energy by about 1000.
The group has recently discovered a strong response that is not the so-called Dirac quantum material, for ex. graphene and topological insulators, with terahertz light. “This manifests itself in the efficient generation of high harmonics, i.e. light with a multiple of the original laser frequency.
These harmonics are still in the terahertz range, however, there is also the first discovered of light emitted from graphene during infrared and terahertz excitation,” recalls Dr. Sergey Kovalev of the HZDR School of Radiation Physics.
“So far, this effect is not very effective and the underlying physical mechanism is unknown.”
The process behind
The new results provide a physical explanation for this process and show how it is possible to increase the light intensity by using highly doped graphene or by using the graphene metamaterial lattice – a material with unique optical properties., special electric or magnetic.
The team also found that the conversion happens very quickly – on a sub-nanosecond timescale, and can be controlled by an electrostatic trigger.
“We say that the high-frequency conversion in graphene is a terahertz-induced radiation system, that is, the charge carriers receive electromagnetic energy from the incident terahertz field.
The applied energy is quickly distributed and material, causing the heating of the support; and finally this leads to the emission of photons in visible form, just as light is emitted by any heated object ,” says Prof. Klaas-Jan Tielrooij from the Ultrafast Dynamics and Nanoscale Systems group at ICN2 at Eindhoven University of Technology.
Optical and terahertz light transmission achieved in graphene-based materials has great potential for applications in information and communication technologies.
The underlying ultrafast thermodynamic processes can affect terahertz-telecom links, and any technology that requires modulation of frequency signals.
Source: Helmholtz-Zentrum Dresden-Rossendorf
