Ultra-fast switches are essential devices for basic research and technology development. Circuits are the basis for all computer and smartphone activities. The speed of a computer’s operation is determined by how quickly a component can transition from zero to one. Electrical switching is made possible by semiconductors, which are used in modern computers.

German researchers at the Ruhr University in Bochum have created a water-based switch that works extremely fast. Within less than a trillionth of a second (10–12 seconds), a short but intense laser pulse transforms water into a conductive state, which behaves almost like a metal. This makes it faster than the known current fastest switching speed of semiconductors.

Claudius Hoberg of the Ruhr Explores Solvation Cluster of Excellence RESOLV and his colleagues have unveiled a possible new approach to water-based circuits. The water in which the researchers had dissolved iodide ions, i.e. salt water, is fanned out through a custom-made nozzle so that it flows as a flattened jet of just a few micrometres.

This water jet is then passed on a short but powerful laser pulse. The laser causes the water to become abruptly conductive at terahertz frequencies, exhibiting properties similar to a metal when it releases electrons from the salt dissolved in it. The water functions as an incredibly fast switch due to the short-lived laser pulse (10–14 seconds) length.

Claudius Hoberg said: “A speed of 10-12 seconds was observed in the terahertz range. A second laser scans the condition of the water.”

Magazine reference:

  1. Adrian Buchmann, Claudius Hoberg, Fabio Novelli: An ultrafast liquid switch for terahertz radiation, in APL Photonics, 2022, DOI: 10.1063/5.0130236