Lasers can guide dangerous lightning strikes to a safer path, study shows

Using a car-size prototype assembled atop a Swiss peak, an international group of researchers demonstrated for the first time that it was possible to use a laser to guide lightning.

The results, published Monday in the journal Nature Photonics, mark a major milestone in developing a novel lightning protection strategy—one of the most ambitious since Benjamin Franklin came up with the lightning rod.

“It is the first realization of something that we’ve been dreaming of for decades," said Matteo Clerici, a University of Glasgow physicist who wasn’t involved in the research. “The fact that they managed to do it in an outdoor environment is a very big step."

Dr. Clerici called the demonstration a “game-changer," but said the technology is still in its infancy, and that commercialization isa distant prospect requiring further investment.

The idea of trying to make a lightning rod with a laser has been around since the laser was first conceptualized more than 50 years ago, according to Aurélien Houard, a research scientist at École Polytechnique in Palaiseau, France, and a co-author of the new study. Short, high-power pulses from a laser can super heat the air, which helps the air become electrically conductive along the path of the laser.

But experiments have mostly been restricted to the laboratory, as scientists worked to divert electrical discharges over distances of several meters, rather than “guiding real lightning," Dr. Houard said. Until now, experiments in the field were unsuccessful.

Lightning, a natural discharge of electricity between clouds, the air, or the ground, can be highly destructive due to its unpredictability—causing thousands of casualties annually. Lightning also causes forest fires and power outages, as well as damages to electronic systems and infrastructure, with associated costs of billions of dollars each year, the study authors previously wrote.

Lightning can also delay rocket launches, some of which aren’t permitted if there has been a strike recently observed within 10 nautical miles of the launchpad or the flight path, according to certain National Aeronautics and Space Administration launch weather criteria.

The most common lightning protection device—often used in city skylines—remains the Franklin rod, devised by the American inventor nearly three centuries ago. These electrically conductive metallic rods can intercept lightning and help provide a path for strikes to safely follow to the ground. But such devices can only offer protection over limited areas directly abutting them, making them ineffective for more sprawling locations like airports, wind farms, power plants or rocket launchpads, said Jean-Pierre Wolf, a professor of physics at the University of Geneva and another study co-author.

“So, if you have a 10-meter-high traditional lightning rod, it protects a region with a radius of about 10 meters, which is fine for your house, but clearly not enough for an airport that is probably a few kilometers long," Dr. Wolf said. “So the idea is we replace this metallic stick with a laser that is kind of a longer, virtual rod that can be put in the direction you want, and be switched on or off at any time."

Each of the laser’s pulses can create electrically conductive channels that lightning is more likely to follow, which can guide strikes to either the ground or a traditional rod below.

“You reduce the probability of having a lightning strike that can go anywhere, basically," Dr. Wolf said. “Because you prepare a preferred path for the lightning."

For the new study, Dr. Wolf and his colleagues used a laser, built for their experiments, that could shoot 1,000 high-energy pulses per second. They situated the laser near a telecommunications tower, which has a Franklin rod affixed to it, at the summit on Säntis Mountain in northeastern Switzerland. During the research period, in the summer of 2021, they turned the laser on and directed it toward the clouds above the tower during more than six hours of thunderstorm activity that occurred within about two miles of the tower.

They observed that, when it was on, the laser diverted four lightning strikes to the rod atop the tower. One of those strikes, which the researchers photographed using two high-speed cameras, followed the laser’s path for a distance of nearly 200 feet.

The key to this demonstration’s success, according to several scientists who weren’t involved in the study, was the high frequency of the laser’s pulses. Dr. Houard said the laser shot 100 times more pulses during one second than previous attempts at similar demonstrations, which meant the technology was “100 times more likely to catch lightning" as it was forming and then guide it.

The next step for the technology, according to Dr. Clerici, is increasing the distance that the laser can guide the lightning to hundreds of meters. That is theoretically possible with a bigger, more powerful laser, Dr. Houard said, but he added that commercialization is at least 10 years away. The prototype laser used in the recent demonstration cost 2 billion euros, or roughly $2.17 billion, he said.