Terahertz waves (THz) sit between microwaves and infrared in the light frequency spectrum, but due to their low-energy scientists have been unable to harness their potential. The conundrum is known in scientific circles as the terahertz gap. Being able to detect and amplify THz waves (T-rays) would open up a new era of medical, communications, satellite, cosmological and other technologies.
One of the biggest applications would be a safe, non-destructive alternative to X-rays. However, until now, the wavelengths – which range between 3mm and 30μm – have proved impossible to utilise due to relatively weak signals from all existing sources. A team of physicists have created a new type of optical transistor – a working THz amplifier – using graphene and a high-temperature semiconductor.
The physics behind the simple amplifier replies on the properties of graphene, which is transparent and is not sensitive to light and whose electrons have no mass. It is made up of two layers of graphene and a superconductor, which trap the graphene massless electrons between them, like a sandwich.
The device is then connected to a power source.
When the THz radiation hits the graphene outer layer, the trapped particles inside attach themselves to the outgoing waves giving them more power and energy than they arrived with – amplifying them.
The breakthrough – made by researchers from Loughborough University, in the UK; the Center for Theoretical Physics of Complex Systems, in Korea; the Micro/Nano Fabrication Laboratory Microsystem and THz Research Center, in China and the AV Rzhanov Institute of Semiconductor Physics, in Russia – has been published in Physical Review Letters, in the journal, American Physical Society (APS).
The team is continuing to develop the device and hopes to have prototypes ready for testing soon. Prof Kusmartsev said they hope to have a working amplifier ready for commercialisation in about a year. He added that such a device would vastly improve current technology and allow scientists to reveal more about the human brain. “The Universe is full of terahertz radiation and signals, in fact, all biological organisms both absorb and emit it. I expect, that with such an amplifier available we will be able to discover many mysteries of nature, for example, how chemical reactions and biological processes are going on or how our brain operates and how we think.”
“The terahertz range is the last frequency of radiation to be adopted by humankind. Microwaves, infrared, visible, X-rays and other bandwidths are vital for countless scientific and technological advancement. It has properties which would greatly improve vast areas of science such as imaging, spectroscopy, tomography, medical diagnosis, health monitoring, environmental control and chemical and biological identification. The device we have developed will allow scientists and engineers to harness the illusive bandwidth and create the next generation of medical equipment, detection hardware and wireless communication technology.”
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