First laser-guided lightning

The first successful use of a laser to divert the path of a lightning strike took place on 24 July 2021 on the peak of Säntis, a 2,502 m (8,209 ft) mountain in northeastern Switzerland. A research team, led by Aurélien Houard (France) and Jean-Pierre Wolf (Switzerland), set up a high-repetition-rate terawatt laser to catch lightning strikes heading for the 124 m (407 ft) broadcast tower near the summit. Just after 4 pm local time, they managed to divert a strike, which followed the path of their laser for 50 m (164 ft) before turning back towards the tower, fitted with a lightning rod.

The concept of a laser lightning rod has been around since the 1960s, when it was theorized that a high-enough-power laser could create a path of ionized air, drawing lightning down a imperceptible "filament" of conductive plasma. The concept was validated by some small-scale experiments in the 1990s, but had not been demonstrated with real lightning until this test.

The metal-conductor lightning rods used on tall structures provide protection to an area with a radius equal to their height. So the lightning rod on a 100-metre-tall tower can protect an area of approximately 31,415 m2 (338,148 sq ft). This is enough to keep buildings safe from lightning strikes, but it means that protecting large areas such as airports, rocket launch complexes, and high-voltage electrical substations is difficult.

A beam of ionized air created by a laser lightning rod could, in theory, extend several kilometres into the atmosphere and protect a much larger area than a static lightning tower could. However, while this test represents an important breakthrough by proving the technique works, it still requires more research. The laser system cost more than $2 billion (£1,583,540,000) to develop, weighed 10 tonnes (10,000 kg), and could only divert lightning for a very short distance.

The details of this experiment were published in Nature Photonics on 16 January 2023.