| Date | 11th, Sep 2019 |
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The image depicts a schematic of terahertz (THz) heterodyne detection with graphene. In this, two THz waves (red) are coupled into graphene, where they are combined or mixed. One of the waves is a high intensity signal generated by a local THz light source (i.e. a local oscillator), at a known THz frequency. The other signal is a faint THz wave that mimics the waves coming from space. Credit: Hans He
Researchers from Chalmers University of Technology have demonstrated a detector made from graphene that could revolutionize the sensors used in next-generation space telescopes. The findings were recently published in the scientific journal Nature Astronomy.
Beyond superconductors, there are few materials that can fulfill the requirements needed for making ultra-sensitive and fast terahertz (THz) detectors for astronomy. Chalmers researchers have shown that engineered graphene adds a new material paradigm for THz heterodyne detection.
“Graphene might be the only known material that remains an excellent conductor of electricity/heat even when having, effectively, no electrons. We have reached a near zero-electron scenario in graphene, also called Dirac point, by assembling electron-accepting molecules on its surface. Our results show that graphene is an exceptionally good material for THz heterodyne detection when doped to the Dirac point”, says Samuel Lara-Avila, assistant professor at the Quantum Device Physics Laboratory and lead author of the paper.
“Graphene might be the only known material that remains an excellent conductor of electricity/heat even when having, effectively, no electrons. We have reached a near zero-electron scenario in graphene, also called Dirac point, by assembling electron-accepting molecules on its surface. Our results show that graphene is an exceptionally good material for THz heterodyne detection when doped to the Dirac point”, says Samuel Lara-Avila, assistant professor at the Quantum Device Physics Laboratory and lead author of the paper. Credit: J O Yxell / Chalmers
In detail, the experimental demonstration involves heterodyne detection, in which two signals are combined, or mixed, using graphene. One signal is a high intensity wave at a known THz frequency, generated by a local source (i.e. a local oscillator). The second is a faint THz signal that mimics the waves coming from space. Graphene mixes these signals and then produces an output wave at a much lower gigahertz (GHz) frequency, called the intermediate frequency, that can be analyzed with standard low noise gigahertz electronics. The higher the intermediate frequency can be, the higher bandwidth the detector is said to have, required to accurately identify motions inside the celestial objects.
Sergey Cherednichenko, professor at the Terahertz and Millimetre Wave Laboratory and co-author of the paper, says:
“According to our theoretical model, this graphene THz detector has a potential to reach quantum-limited operation for the important 1-5 THz spectral range. Moreover, the bandwidth can exceed 20 GHz, larger than 5 GHz that the state-of-the-art technology has to offer.”
