A new method capable of sending high-intensity laser beams through the atmosphere, could one day be used to guide lightning away from buildings. Eight Lightning Bolts Striking San Francisco. Image © Phil Mcgrew
Optical scientists at the University of Arizona and the University of Central Florida have developed a technology, still in the laboratory phase, capable of sending high-intensity laser beams through the atmosphere much farther than was possible before.
This new technique could one day guide electrical discharges from the lightning, away from buildings.
Maik Scheller, an assistant research professor in the UA College of Optical Sciences, who led the experimental work, said:
“Think of two airplanes flying together, a small fighter jet accompanied by a large tanker. Just like the large plane refuels the fighter jet in flight and greatly extends its range, our primary, high-intensity laser pulse is accompanied by a second laser pulse – the “dress” beam – which provides a constant energy supply to compensate for the energy loss of the primary laser beam as it travels farther from its source.
Usually, if you shoot a laser into the air, it is limited by linear diffraction. But if the energy is high enough and condensed into a few femtoseconds, creating a burst of light of extremely high intensity, it propagates through the air in a different way due to self-focusing. The problem is that as it also ionizes the air and creates a plasma, so the laser loses energy.
In other words, at some point the airplane runs out of fuel.
We use two different kinds of beams: One is a focused central beam of high intensity that creates the filament. The other that surrounds it has a long range of almost constant intensity. As a result, the dress beam propagates in a nearly linear manner.”