Laser-wielding boffins bend lightning to their will

Discovery could provide better protection for power stations, airports and launchpads

Video Scientists have for the first time demonstrated that a laser can act as a lightning rod to disperse these dangerous atmospheric discharges.

Although lab-based demos have proven the concept, an experiment conducted on the Säntis Mountain in northeastern Switzerland in late 2021 - and only detailed in Nature this week - showed it works in the wild when a high-repetition-rate terawatt laser was used to divert a lightning strike by over 50 meters.

A group led by Aurélien Houard, research engineer at ENSTA Paris, has shown over more than six hours of operation during thunderstorm activity, the laser diverted the course of four upward lightning discharges.

"From the first lightning event using the laser, we found that the discharge could follow the beam for nearly 60 meters before reaching the tower, meaning that it increased the radius of the protection surface from 120m to 180," said Professor Jean-Pierre Wolf, of the University of Geneva's Department of Applied Physics.

"When very high-power laser pulses are emitted into the atmosphere, filaments of very intense light form inside the beam. These filaments ionize the nitrogen and oxygen molecules in the air, which then release electrons that are free to move. This ionized air, called plasma, becomes an electrical conductor."

The laser was emitted in picosecond pulses at 500mJ, a wavelength of 1,030nm and a 1kHz repetition rate from the vicinity of a 124m telecommunications tower that is struck by lightning about 100 times a year.

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Covered by Nature Photonics this week, the result was confirmed using high-frequency electromagnetic waves generated by lightning to locate the strikes. An X-ray burst at the time of the strikes also backed up the findings.

Lightning rods were first detailed by Benjamin Franklin – US Founding Father and acclaimed polymath – who, through a series of experiments, produced a workable system around 1760. But since then the technology hasn't advanced much, and the team think the idea could be developed to protect areas at high risk from storms.

There are around 1.4 billion lightning strikes across the globe every year. The total costs from damage to industry and property are estimated to be between $8 billion and $10 billion annually in the US alone.

The researchers said the work could help in the study of laser physics in the atmosphere and lead to the development of new lightning protection systems.

"Although this research field has been very active for more than 20 years, this is the first field result that experimentally demonstrates lightning guided by lasers. This work paves the way for new atmospheric applications of ultrashort lasers and represents an important step forward in the development of a laser-based lightning protection for airports, launchpads or large infrastructures," they said. ®