High-power terahertz waves from a CMOS-compatible device

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By eeNews Europe

What’s more, their ability to carry vast quantities of data could hold the key to faster wireless communications. Hence, academics are racing to design low-cost and compact THz sources to expand their field of applicability beyond the expensive passenger scanning apparatuses found in some airports.

Now, a team of researchers at the Power and Wide-band-gap Electronics Research Laboratory (POWERlab) from Ecole Polytechnique Federale de Lausanne (EPFL) has built a nanodevice capable of generating extremely high-power signals in just a few picoseconds, producing high-power THz waves.

The nanoscale terahertz wave generator can be implemented
on flexible substrates. Credit: EPFL / POWERlab.

The compact and inexpensive device described in the Nature journal under the paper title “Nanoplasma-enabled picosecond switches for ultrafast electronics” consists of two metal plates situated very close to one another, separated by a gap as small as 20nm. When a voltage is applied, electrons surge towards one of the plates, where they form a nanoplasma. Once the voltage reaches a certain threshold, the electrons are emitted almost instantly to the second plate. This rapid movement enabled by such fast switches creates a high-intensity pulse (with a spiking voltage from 10V to 100V) that produces high-frequency waves. In contrast, conventional electronic devices are only capable of switching at speeds of up to one volt per picosecond, too low to produce high-power THz waves.

The new nanodevice is capable of generating this spark almost continuously, meaning it can emit. When hooked up to antennas, the system can produce and radiate high-power THz waves.

The authors reported an ultrafast switching speed up to 50 million signals every second, higher than 10 volts per picosecond, which is about two orders of magnitude larger than that of field-effect transistors and more than ten times faster than that of conventional electronic switches, they wrote.

“Normally, it’s impossible to achieve high values for both variables,” explains Prof. Elison Matioli who led the research. “High-frequency semiconductor devices are nanoscale in size but they can only cope with a few volts before breaking out. High-power devices, meanwhile, are too big and slow to generate terahertz waves. Our solution was to revisit the old field of plasma with state-of-the-art nanoscale fabrication techniques to propose a new device to get around those constraints.”

The nanodevices are simple to design and can be integrated with other electronic devices such as transistors, so the researchers anticipate they will find many more use cases beyond generating THz waves.

Ecole Polytechnique Federale de Lausanne –

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