Ashley N. Paddock, [email protected] PALAISEAU, France — With the help of a laser-based lightning rod, laboratory-generated lightning was coaxed to strike the same place not just twice but numerous times, and contrary to the path of least resistance. This advance demonstrates the potential of laser-based lightning rods for research and protection. In earlier experiments, femtosecond lasers were used to produce a virtual lightning rod from ultrashort filaments of ionized gas that act as electrical guide wires. Now, for the first time, researchers in France have used laser-induced atmospheric filaments to reroute an electrical discharge from its normal target toward a less attractive electrode. In other words, instead of striking the "highest tree," it struck a lower object over and over again. A team of scientists from Laboratoire d'Optique Appliquée, EADS France, CILAS and Astrium conducted a series of experiments to see how well lasers can harness and control lightning. The investigators sent a laser beam past a spherical electrode toward an oppositely charged planar electrode. The laser stripped away the outer electrons from the atoms along its path, creating a plasma filament that channeled an electrical discharge from the planar electrode to the spherical one. Integrated picture of the discharge and measurements of the voltage and current in the case of an unguided discharge (a, b) and laser-guided discharge (c, d). Courtesy of AIP Advances, American Institute of Physics. They added a longer, pointed electrode to their set of electrode shapes to see whether the filament had the ability to redirect an electrical discharge from its normal path and observed that, with no laser lightning rod, the discharge predictably hit the tall, pointed electrode first. However, when they used the laser filament to guide it, the electrical discharge followed the ionized path and hit the spherical electrode instead. The researchers found that they could divert the electrical discharge even after it was already on its way, meaning that they could change the lightning's path. "The laser lightning rod would be a valuable alternative to lightning rockets," said Dr. Aurélien Houard of Laboratoire d'Optique Appliquée. A lightning rocket is a device that controls the time and place of a lightning strike. The research was published online in the American Institute of Physics' journal AIP Advances (doi: 10.1063/1.3690961).