April 19, 2014
Could A Dual Laser Beam Help Us Control The Weather?
Brett Smith for redOrbit.com - Your Universe Online
While controlling the weather may have been fodder for classic episodes of the G.I. Joe cartoons, researchers from the University of Central Florida have been researching just that and say they may have found a way to do it by using a dual laser beam.
Condensation, lightning and storm activity are all associated with considerable amounts of static charged particles. Exciting those particles with the proper kind of laser could possibly cause a shower in cases of extreme drought, according to the Florida team.
The researchers’ report in Nature Photonics describes how a laser beam dressed with a second beam prevents the dissipation of energy necessary to excite charged particles in a cloud.
While high-intensity lasers can travel millions of miles, "when a laser beam becomes intense enough, it behaves differently than usual – it collapses inward on itself," said study author Matthew Mills, a graduate student in the university’s Center for Research and Education in Optics and Lasers (CREOL).
“The collapse becomes so intense that electrons in the air's oxygen and nitrogen are ripped off creating plasma – basically a soup of electrons,” Mills added.
When this happens, the laser beam pushes back outward – creating a battle between the spreading and collapsing of an ultra-short laser pulse. Known as filamentation, the tension helps to create a filament or "light string" that only develops temporarily until the properties of air make the beam disperse.
"Because a filament creates excited electrons in its wake as it moves, it artificially seeds the conditions necessary for rain and lightning to occur," Mills said.
Previous efforts have generated "electrical events" in clouds, raising the threat of lightning strikes affecting any close-proximity effort to seed a cloud with a laser.
"What would be nice is to have a sneaky way which allows us to produce an arbitrary long 'filament extension cable.' It turns out that if you wrap a large, low intensity, doughnut-like 'dress' beam around the filament and slowly move it inward, you can provide this arbitrary extension," Mills said.
"Since we have control over the length of a filament with our method, one could seed the conditions needed for a rainstorm from afar,” Mills added. “Ultimately, you could artificially control the rain and lightning over a large expanse with such ideas."
Currently, the Florida researchers have only been able to extend their ‘dressed’ beam about 7 feet, but said they are planning to stretch the filament even farther.
"This work could ultimately lead to ultra-long optically induced filaments or plasma channels that are otherwise impossible to establish under normal conditions," said study Demetrios Christodoulides, a professor of optics who is overseeing work on the project.
"In principle such dressed filaments could propagate for more than 50 meters or so, thus enabling a number of applications,” Christodoulides said. “This family of optical filaments may one day be used to selectively guide microwave signals along very long plasma channels, perhaps for hundreds of meters."
The study team said other potential uses include long-distance sensors and spectrometers to identify chemical makeup of objects.