Chalmers University of Technology researchers have demonstrated a detector made from graphene that could revolutionize the sensors used in next-generation space telescopes, according to research published in the scientific journal Nature Astronomy.
The researchers believe engineered graphene could fulfill the requirements for making ultra-sensitive and fast terahertz (THz) detectors for astronomy. The material 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,” said Samuel Lara-Avila, assistant professor at the Quantum Device Physics Laboratory and lead author of the paper, in a statement. “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.”
The scientists found that graphene, when mixed with THz signals, produces an output wave at a much lower gigahertz (GHz) frequency, called an 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, said, "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."
The graphene THz detector also reduces the power needed for the local oscillator to reliably detect faint THz signals, several orders of magnitude lower than superconductors require. This could enable quantum-limited THz coherent detector arrays, thus opening the door to 3D imaging of the universe.
Sergey Kubatkin, professor at the Quantum Device Physics Laboratory and co-author of the paper, added, "The core of the THz detector is the system of graphene and molecular assemblies. This is in itself a novel composite 2D material that deserves deeper investigation from a fundamental point of view, as it displays a whole new regime of charge/heat transport governed by quantum-mechanical effects."