New laser technology could divert lightning strikes

Apr 01, 2014 by Daniel Stolte
Researchers hope that ultimately, the technology could be used to steer lightning away from buildings. Credit: David Aragon

(Phys.org) —Optical scientists at the University of Arizona and the University of Central Florida have developed a technology capable of sending high-intensity laser beams through the atmosphere much farther than was possible before. The research is still in the laboratory phase, but could one day guide electrical discharges, such as lightning, away from buildings.

Currently, high-intensity lasers, produced with modern technology essentially disappear over distances greater than a few inches or several feet at best when focused tightly, due to diffraction – the same effect that makes a stick seem to "bend" when dipped into water. This makes them too short-ranged for applications such as diverting lightning.

The breakthrough lies in embedding the primary, high-intensity inside a second beam of lower intensity. As the primary beam travels through the air, the second beam – called dress beam – refuels it with energy and sustains the primary beam over much greater distances than were previously achievable. The researchers' results were published on March 23 in the journal Nature Photonics.

"Think of two airplanes flying together, a small fighter jet accompanied by a large tanker," said Maik Scheller, an assistant research professor in the UA College of Optical Sciences, who led the experimental work leading to the publication. "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 of the primary laser beam as it travels farther from its source."

The development of the new technology was supported by a five-year, $7.5 million U.S. Department of Defense grant – awarded to a group of researchers led by Jerome Moloney, a UA mathematics and professor. Moloney is heading up the multidisciplinary, multi-institution research effort to investigate ultra-short laser pulses, focusing on their effects in the atmosphere and ways to improve their propagation over many kilometers.

The top image shows the case of the intense central beam alone. The beam is focused and a short filament results and the plasma channel dissipates rapidly. In the bottom figure, the beam is accompanied by the dress beam. The filament and the plasma channel is extended manifold.

Improved understanding of the pulses would create the groundwork for a new class of robust laser beams that are more effective in overcoming scattering caused by atmospheric turbulence, water droplets in clouds, mist and rain, according to Moloney. Such beams could be used in detection systems reaching over long distances.

Unlike conventional lasers, the laser bursts used in this research pack extremely high energy into very short timespans on the order of a femtosecond; a billionth of a millionth of a second.

"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," Scheller said. "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.

The filament doesn't go very far because of the energy loss that ultimately causes the laser to dissipate. The dress beam used in Scheller's research overcomes this limitation.

"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."

Similar to the principle of noise-canceling headphones, the energy loss of the primary laser beam and the energy supply from the dress laser beam cancel each other out. In the lab, the researchers were able to extend the range of filament lasers tenfold – from about 10 inches to 7 feet.

Simulations performed by Matthew Mills at the University of Central Florida have shown that by scaling the new laser technology to atmospheric proportions, the range of the filaments could reach 50 meters (165 feet) or more.

As the filaments travel through the air, they leave a channel of plasma in their wake – ionized molecules stripped of their electrons. Such plasma channels could be used as a path of least resistance to attract and channel lightning bolts. Ultimately, this technology could be used to control lightning bolts during a thunderstorm and steer them away from buildings.

Explore further: Scientists create light bullets for high-intensity optical applications

More information: "Externally refuelled optical filaments." Maik Scheller, et al. Nature Photonics 8, 297–301 (2014) DOI: 10.1038/nphoton.2014.47. Received 06 July 2013 Accepted 06 February 2014 Published online 23 March 2014

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User comments : 13

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AlexanderEden91
not rated yet Apr 01, 2014
I could have misread, but "controlling lightning" also seems to mean "creating lightning". In which case the DoD has probably already called the researchers.
I personally cannot wait to own my first lightning gun.
DistortedSignature
4.2 / 5 (5) Apr 01, 2014
@AlexanderEden, I believe you have misread. No where in the article does the phrase "controlling lightning" exist. The title is more of a click bait sort of implementation, or a possible practical use of the discovery. Attract might be an appropriate word as well as used in the last paragraph.

... Such plasma channels could be used as a path of least resistance to attract and channel lightning bolts. Ultimately, this technology could be used to control lightning bolts during a thunderstorm and steer them away from buildings.


Unless you can discharge the same amount of energy as lightning I suppose you could point the laser at a target for lightning to follow to hit the target. But if we could create that sort of energy, a railgun sounds more practical. The US Navy has a 32MJ prototype railgun, while lightning bolts are estimated to produce near 5,000 MJ of energy. (Anyone knowledgeable in this, please correct me on anything I mispeak on)
Gimp
5 / 5 (2) Apr 01, 2014
I can see this as a great boon to channeling a lighting bolt to a specific location, if you could reliably predict where a bolt would hit, you could store the electricity for other uses. Tampa, FL would seem to be an ideal location for such a pilot program.
mzso
1 / 5 (1) Apr 01, 2014
Lightning doesn't have much energy, only high voltage.
Osiris1
1.3 / 5 (4) Apr 01, 2014
Guys get a grip, it is April 1...today! The airborne laser operated by the Air Force has been tested as shooting down missiles over a thousand miles away with a multi million watt beam of chemical iodine laser light. It sure as heck does not dissipate in 6 inches. Methinks the author of this April Fools joke knows how to BS verrry well. The 'six inches' should be a key !
Protoplasmix
5 / 5 (3) Apr 01, 2014
Guys get a grip, it is April 1...today! The airborne laser operated by the Air Force has been tested as shooting down missiles over a thousand miles away with a multi million watt beam of chemical iodine laser light. It sure as heck does not dissipate in 6 inches. Methinks the author of this April Fools joke knows how to BS verrry well. The 'six inches' should be a key !

Uh, it's real, no joke:
See: http://www.nature....47.html
dirk_bruere
not rated yet Apr 02, 2014
Old idea from the 1980s SDI projects. BTW, the Japanese demonstrated lightning control by laser years ago
11791
1 / 5 (2) Apr 02, 2014
7 feet. big deal
millsms
5 / 5 (1) Apr 02, 2014
@11791. You are certainly right to sneer at an prolongation of centimeters to meters. But keep in mind, this is a laboratory demonstration in order to prove that it works (you must do this before anybody gives you the money to make the kilometer stuff happen).

The beauty of my idea is that a dress beam becomes an extension cord and can accessorize any filament. There is a device called the Teramobile that can already make filaments which cover hundreds of meters. If you do the math, the dress concept actually works better the longer the filament is but the optical components needed to make it happen have tighter tolerances. - Matt Mills
daveca
not rated yet Apr 03, 2014
@AlexanderEden,

Unless you can discharge the same amount of energy as lightning I suppose you could point the laser at a target for lightning to follow to hit the target. )


Absolutely false. Its not energy equivalency. It is creating a conductive channel for cloud charges to be attacted to the ground through. It is choosing the channel instead of using cloud and ground conditions to choose it at more or less random.

It has nothing to do with conservation of energy.
daveca
not rated yet Apr 03, 2014
This is absolutely workable. Early arc discharge research proved that UV illumination of a plate decreases the potential needed for arc formation.. This follows that at a much more advanced level.

This intends to make a chosen path through the atmosphere through which a cloud, with a massive electrical charge, can send its charge to the ground through.

No, it cannot be used to store electricity. There is no such thing as storing electricity and certainly not a MV levels.

Most of the comments here show a total ignorance of electrical physics.

This also has significant communications systems uses which is probably why DoD is in on it.
daveca
not rated yet Apr 03, 2014
I can see this as a great boon to channeling a lighting bolt to a specific location, if you could reliably predict where a bolt would hit, you could store the electricity for other uses. Tampa, FL would seem to be an ideal location for such a pilot program.


It is impossible to store electricity:

Batteries do not, they store chemical reactions

Capacitors do not, they store electro-static energy, not free electron energy. Apples and different apples.

Your post violates most of the electrical physics book at once.

Guess why no ones done it?

Because it violates most of the physics book at once.
This is not a topic for conspiracy theorism.
adamcrume
not rated yet Apr 04, 2014
It is impossible to store electricity:

Batteries do not, they store chemical reactions

Capacitors do not, they store electro-static energy, not free electron energy. Apples and different apples.


Depends on how you define "storing electricity." Also, it's not impossible; what would you call current flowing in a superconducting ring? How is that not storing electricity?

Besides, you're being a bit pedantic. I imagine they just meant capturing and storing the energy and did not specifically mean storing it as electricity.