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Laser controls ultra-fast water switch

Researchers present a completely new concept for switches with unprecedented speed.

Researchers at Ruhr-Universität Bochum have developed an ultra-fast circuit based on water. With a short but strong laser pulse, the water can be put into a conductive state within less than a trillionth of a second (10 -12 seconds) and behaves almost like a metal during this time. This means that the circuit is faster than the previously known switching speed of a semiconductor. Adrian Buchmann, Dr. Claudius Hoberg and Dr. Fabio Novelli from the Cluster of Excellence Ruhr Explores Solvation, RESOLV for short , report in the magazine APL Photonics from December 6, 2022.

Laser makes the water act like a fast switch
All computing operations of computers are based on circuits. The speed with which a component can switch between the states zero and one ultimately also determines the speed of the computer. In current computers, semiconductors are installed that enable electrical circuits. “They are naturally limited in their speed,” explains Claudius Hoberg.

He and his colleagues have introduced an entirely new approach to water-based circuits. The water, in which the researchers had dissolved iodide ions - one could speak of salt water - is fanned out by a specially developed nozzle so that it flows as a flat jet a few micrometers thick. “You can think of it like squeezing a hose, making the jet of water wide and flat, only much smaller,” explains Hoberg.

A short but strong laser pulse is then passed through this water fan. The laser frees electrons from the salt dissolved in the water, so that the water becomes conductive at terhertz frequencies and suddenly behaves like a metal. Due to the short pulse duration of the laser pulse of 10-14 seconds, the water becomes an ultra-fast switch. “The speed is in the terahertz range at 10-12 seconds,” says Claudius Hoberg. Another laser queries the condition of the water.

Adrian Buchmann, Claudius Hoberg, and Fabio Novelli: An ultra-fast liquid switch for terahertz radiation, in: APL Photonics, 2022, DOI: 10.1063/5.0130236”

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