Obstacle-passing bending laser to fish for lightning

By | April 25, 2009

Airy beamA special laser beam that can curve and pass obstacles may be used to direct lightning and make future particle accelerators smaller.

A team of scientists at the University of Arizona headed by Professor Pavel Polynkin combined a high energy pulse laser beam, which can be used to ionize gases in the atmosphere to create a plasma channel, with a special beaming technique. The technique called Airy beam – named after George Biddell Airy, a 19th century astronomer who discovered the mathematics behind the phenomenon – allows bending laser, reports Nature journal.

An Airy beam is actually created by complicated interference of a light pattern, created by a laser passing through a digital screen, carefully phasing the light waves. The resulting beam, or rather a pattern of one bright area surrounded by small dim patches, has several curious characteristics.

For one, it bends by several millimetres for every several dozen centimetres it travels. Combined with an intensive laser, the technology can create curved plasma channels.

via Obstacle-passing bending laser to fish for lightning | SciTech from 2009-04-10 | RT.

This is from focus, November 2007:

A new optics experiment makes a light beam appear to bend in air. The brightest patch of the beam also appears to travel with almost no spreading, unlike ordinary laser beams, as a team reports in the 23 November Physical Review Letters. The so-called Airy beam may lead to new kinds of optical engineering.

Any ordinary beam of light spreads as it travels, thanks to the wave effect known as diffraction. Even a laser pointer’s beam gets wider and dimmer on the way to a distant screen. But in 1987 a team introduced the Bessel beam, whose intensity remains constant as you move away from the source [1]. The “trick” is that light doesn’t actually travel along the beam axis; the intensity at any location in the beam results from the complicated interference of light emerging from all points in a large, ring-shaped slit at the source. Other researchers have devised variations on the Bessel beam that have other surprising properties. … focus.aps.org

This from PhysOrg, Nov 2007

Scientists have made the first observation of an unusual class of optical waves called Airy beams. Unlike most types of light waves, Airy beams have the ability to resist diffraction over long distances, and can also freely accelerate during propagation.
The researchers, Georgios Siviloglou, John Broky, Aristide Dogariu, and Demetrios Christodoulides from CREOL-University of Central Florida (UCF), hope that these unusual features may enable Airy beams to be used in applications such as particle manipulation and in nonlinear media. The group’s study, published in a recent issue of Physical Review Letters, reports the observation of Airy beams in both one- and two-dimensional configurations.

Airy beams take their name from the “airy integral,” introduced by Sir George Biddell Airy in the 1830s to explain optical caustics such as those appearing in a rainbow. Airy beams were initially predicted in 1979 by two scientists, Michael Berry and Nandor Balazs, within the context of quantum mechanics. The scientists theorized the existence of a free particle described by the Schrödinger equation that could exhibit an Airy wave packet that doesn’t spread out as it propagates—in other words, it is diffraction-free. Remarkably, an Airy wave packet has the unusual ability to freely accelerate even in the absence of an external stimulus.

“We are not sure why this absolutely fascinating prediction went unnoticed for so long given the fame of Michael Berry,” Christodoulides told PhysOrg.com. “We think that it is partly due to the fact that it was initially published in a relatively ‘obscured’ journal. The second issue has to do with experimental implementation. It is only very recently that we realized that exponentially truncated Airy beams have a Gaussian power spectrum and can thus be easily synthesized from standard Gaussian beams.” – physorg

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