Video

A “Star Wars” laser bullet – this is what it really looks like

Action-packed science-fiction movies often feature colourful laser bolts. But what would a real laser missile look like during flight, if we could only make it out? How would it illuminate its surroundings? The answers lie in a film made at the Laser Centre of the Institute of Physical Chemistry of the Polish Academy of Sciences in cooperation with the Faculty of Physics at the University of Warsaw. Continue reading A “Star Wars” laser bullet – this is what it really looks like

Physicists demonstrate acceleration of electrons by laser in vacuum

Each row of two frames represents one snapshot-pair of laser on (on the right side) and laser off (on the left side) with unchanged configuration. One can see a clear increase from these pictures, proof that the laser accelerates the 20 mega electron volts electron beam in vacuum. Pictures of the beam momentum spread after the spectrometer taken with the laser off (left column) and the laser on (right column). The length of the beam image reveals the energy spread of the beam. The experiment recorded 30 shots. Twenty shots were high intensity and showed effects of the laser on/laser off difference. Four shot examples are shown here. Pictures are taken from spectrometer on Beam Line #1 at BNL-ATF.

Each row of two frames represents one snapshot-pair of laser on (on the right side) and laser off (on the left side) with unchanged configuration. One can see a clear increase from these pictures, proof that the laser accelerates the 20 mega electron volts electron beam in vacuum. Pictures of the beam momentum spread after the spectrometer taken with the laser off (left column) and the laser on (right column). The length of the beam image reveals the energy spread of the beam. The experiment recorded 30 shots. Twenty shots were high intensity and showed effects of the laser on/laser off difference. Four shot examples are shown here. Pictures are taken from spectrometer on Beam Line #1 at BNL-ATF.

Accelerating a free electron with a laser has been a longtime goal of solid-state physicists. David Cline, a distinguished professor in the UCLA Department of Physics and Astronomy, and Xiaoping Ding, an assistant researcher at UCLA, have conducted research at Brookhaven National Laboratory in New York and have established that an electron beam can be accelerated by a laser in free space….

Read more at: http://phys.org

Squeezed laser will bring gravitational waves to the light of day

The new squeezed light laser of GEO600. A highly complex laser system produces light which particularly quiet in the gravitational wave detector. Credit: © Max Planck Institute for Gravitational Physics (Hannover)

A quantum phenomenon allows detectors which sense oscillations of space-time to measure with 50 percent more accuracy.

Measuring at the limits of the laws of nature – this is the challenge which researchers repeatedly take up in their search for . The interferometers they use here measure with such sensitivity that a particular of light – shot noise – limits the measuring accuracy. With the “squeezed light” method scientists from the Max Planck Society and the Leibniz University Hannover likewise use quantum physics in a countermove in order to remove the interfering effect. The new type of laser light improves the measuring accuracy of the gravitational wave detector GEO600 by around 50 percent and thus increases its effective sensitivity. This is the first time this technology has been used outside of a test laboratory anywhere in the world. The results will be published in the specialist journal Nature Physics, online on September 11, 2011….. Continue reading Squeezed laser will bring gravitational waves to the light of day

Laser Meets Lightning

On Thursday 18 August, the sky above the Allgäu Public Observatory in southwestern Bavaria was an amazing sight, with the night lit up by two very different phenomena: one an example of advanced technology, and the other of nature’s dramatic power.

As ESO tested the new Wendelstein laser guide star unit by shooting a powerful laser beam into the atmosphere, one of the region’s intense summer thunderstorms was approaching — a very visual demonstration of why ESO’s telescopes are in Chile, and not in Germany. Heavy grey clouds threw down bolts of lightning as Martin Kornmesser, visual artist for the ESO outreach department, took timelapse photographs of the test for ESOcast 34. With purely coincidental timing this photograph was snapped just as lightning flashed, resulting in a breathtaking image that looks like a scene from a science fiction movie. Although the storm was still far from the observatory, the lightning appears to clash with the laser beam in the sky.

Laser guide stars are artificial stars created 90 kilometres up in the Earth’s atmosphere using a laser beam. Measurements of this artificial star can be used to correct for the blurring effect of the atmosphere in astronomical observations — a technique known as adaptive optics. The Wendelstein laser guide star unit is a new design, combining the laser with the small telescope used to launch it in a single modular unit, which can then be placed onto larger telescopes.

The laser in this photograph is a powerful one, with a 20-watt beam, but the power in a bolt of lightning peaks at a trillion (one million million) watts, albeit for just a fraction of a second! Shortly after this picture was taken the storm reached the observatory, forcing operations to close for the night. While we may have the ability to harness advanced technology for devices such as laser guide stars, we are still subject to the forces of nature, not least among them the weather!
http://www.eso.org/public/images/potw1136a/

Firing laser beams into the sky could make it rain, say scientists

Water droplets have been created by shooting lasers into the air. The technique might be used to create or prevent rain

Ever since ancient farmers called on the gods to send rain to save their harvests, humans have longed to have the weather at their command.

That dream has now received a boost after researchers used a powerful laser to produce water droplets in the air, a step that could ultimately help trigger rainfall.

While nothing can produce a downpour from dry air, the technique, called laser-assisted water condensation, might allow some control over where and when rain falls if the atmosphere is sufficiently humid.

Researchers demonstrated the technique in field tests after hauling a mobile laser laboratory the size of a small garage to the banks of the Rhône near lake Geneva in Switzerland.

Records from 133 hours of firings revealed that intense pulses of laser light created nitric acid particles in the air that behaved like atmospheric glue, binding water molecules together into droplets and preventing them from re-evaporating.

Within seconds, these grew into stable drops a few thousandths of a millimetre in diameter: too small to fall as rain, but large enough to encourage the scientists to press on with the work.

“We have not yet generated raindrops – they are too small and too light to fall as rain. To get rain, we will need particles a hundred times the size, so they are heavy enough to fall,” said Jérôme Kasparian, a physicist at the University of GenevaA report on the tests appears in the journal Nature Communications.

With improvements, shooting lasers into the sky could either help trigger or prevent showers. One possibility might be to create water droplets in air masses drifting towards mountains. The air would cool as it rose over these, causing the water droplets to grow and eventually fall.

An alternative might be to stave off an immediate downpour by creating so many tiny droplets in the air that none grew large enough to fall. “Maybe one day this could be a way to attenuate the monsoon or reduce flooding in certain areas,” Kasparian said.

Efforts to bring the weather under control have become a matter of national pride in China, where the Beijing meterological bureau has an office devoted to weather modificationIn 2009, the department claimed success after 18 jets and 432 explosive rockets laden with chemicals were sent into the skies to “seed” clouds. The chemicals, usually dry ice or silver iodide, provide a surface for water vapour to condense on, and supposedly trigger downpours from pregnant skies.

Kasparian believes laser-assisted rainmaking has advantages over blasting chemicals into the sky. “The laser can run continuously, you can aim it well, and you don’t disperse huge amounts of silver iodide in the atmosphere,” he said.

“You can also turn the laser on and off at will, which makes it easier to assess whether it has any effect. When the Chinese launch silver iodide into the sky, it is very hard to know whether it would have rained anyway,” Kasparian added.

The team’s Teramobile laser can shoot beams of light several kilometres into the sky, putting within easy reach the regions of the atmosphere where water vapour normally condenses into raindrops.

One modification the team is considering involves sweeping the laser across the sky to produce water droplets over a greater area. “From a technical point of view, sweeping the laser is not an issue. They do it in nightclubs all the time,” Kasparian said.
http://www.guardian.co.uk/science/2011/aug/30/firing-laser-beams-atmosphere-rain?CMP=twt_fd