Scientists control lightning with lasers

This is the first successful trial in 20 years of experiments explained research physicists Aurelien Houard and Jean-Pierre Wolf. The breakthrough could lead the way to using lasers to protect airports, rocket launchpads and other sensitive infrastructure.

A team of physicists and scientists have presented the first demonstration that laser-induced filaments – formed in the sky by short and intense laser pulses – can guide lightning discharges over considerable discharges.

“We believe that this experimental breakthrough will lead to progress in lightning protection and lightning physics,” stated the team.

In the UK, lightning strikes the ground 300,000 times a year. Lightning discharges between charged clouds ands the Earth’s surface are responsible for considerable damages and casualties. It is vital to develop better protection methods in addition to the traditional Franlkin rod.

To prevent damage, people rely on technology invented in 1752: the lightning rod. This consists of a pointed metal rode attached to a building’s roof, connected to the ground by a wire. The rod creates a strong electric field that draws lightning away from the building so that when the rod is hit, the wire safely ushers current to the ground.

If it isn’t broke, why fix it? A key drawback of a conventional lightning rod is that the radius of its area of protection is roughly equal to its height. Due to practical limits to how tall a lightning rod can be built, they may not prove useful at protecting large areas.

Since the first lasers emerged in the 1960s, scientists have considered using them to guide lightning. In principle, the laser beam would create a straight path of ionised air where current could flow more easily.

Early attempts with high-powered lasers failed because within a short distance the ionised air absorbed the laser light, leaving an air channel too short and broad to attract or affect lightning.

30 years later, physicists developed lasers that produced pulses just femtoseconds long. Despite being shorter and lower energy, the pulses proved more effective at opening conductive channels.

The laser light ionises air, which then works like a lens to further focus the light into a filament the width of a hair. The thin beam heats the air, driving away molecules and leaving a channel of lower density air capable of better conducting electricity. This was the case in laboratory experiments, however efforts to control natural lightning in New Mexico in 2004, and Singapore in 2011 still failed to influence the paths of bolts.

The trial

The research is the culmination of a five-year €4 million project.

In the summer of 2021, Scientists led by Hourard and Wolf placed a femtosecond laser on top of Säntis mountain, Switzerland next to a 124m tall telecommunications tower.

The Yb:YAG laser emitted pulse of picosecond duration and 500mJ energy at a wavelength of 1,030nm and at 1kHz repetition rate.

Acting as a giant lightning rod, the tower gets struck by lightning 100 times a year and is equipped with multiple sensors the record the lightning current, electromagnetic fields at various distances, X-rays and radiation sources from the lightning discharges.

The researchers shined their laser past the top of the tower from July September 2021 during a total of over six hours of thunderstorms. During this period the tower got hit at least 15 times, including four times when the laser system was running.

The researchers studied the strikes both with radio antennas bordering the mountain, which traced the lightning’s path, and with high-speed cameras. In all four lightning strikes taken with the laser on, the lightning followed the path of the laser beam before jumping to the tower, the team reported.

Thus, researchers steered about the last 50m of each bolt’s otherwise random trajectory.

The researchers succeeded where other’s haven’t before, in part because of the speed of their laser, which fired 1,000 times per second rather than 10. The success was also down to the specific location where the lightning always hit the same point.

Going forward

It remains unknown whether the million-dollar technology works better than the conventional lightning rod.

The researchers explained that the goal shouldn’t be to replace the conventional lightning rod, but to extend its range of coverage.

Researchers still have a long way to go to prove the technique captures lightning effectively. However, this work marks an excellent milestone.

Read the full research here.

Image credit to Nature Phonics (Nat. Photon.) ISSN 1749-4893.