We've all seen the colorful laser bolts of science-fiction movies, but what would a real world laser bolt look like (if we could actually make it out)? According to engineering.com, a group of researchers 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 (IPC PAS and FUW) have managed to answer that question. Their tests of a new compact high-powered laser have given them the opportunity to film the passage of an ultrashort laser pulse through the air.
"If you wanted to film a single light impulse to move as slowly on film as in our recording, you would have to use a camera operating at a speed of a billion frames per second", says Dr. Yuriy Stepanenko, leading the team responsible for the construction of the laser.
Since cameras recording billions of frames per second do not exist, the researchers used an earlier known trick of synchronizing a camera with the laser generating the pulses at a rate of approx. 10 shots per second. The synchronization was such that with each shot the camera image was minimally delayed from the previous one.
"In fact, a different laser pulse can be seen in every frame of our film", explains Dr. Paweł Wnuk, (LC of IPC PAS and FUW) and adds: "Luckily, the physics always stays the same. So, on the film one can observe all the effects associated with the movement of the laser pulse in space, in particular, the changes in ambient light depending on the position of the pulse and the formation of flares on the walls when the light passes through the dispersing cloud of condensed water vapour".
The laser used in the test was powerful enough to immediately ionize the atoms around it resulting in a plasma fibre – filament – to be formed alongside the pulse. The laser was set up to balance the interactions between the pulse's electromagnetic field and the plasma filament so that the light beam did not disperse in air but instead underwent self-focusing, resulting in the pulse moving a much greater distance than low-power pulses while maintaining it's original parameters.
"It is worth noting that although the light we are shooting from the laser is in the near infrared range, a laser beam like this travelling through the air changes colour to white. This happens since the interaction of the pulse with the plasma generates light of many different wavelengths. Received simultaneously, these waves give the impression of white", adds Dr. Stepanenko.
(Score: 2) by RobotMonster on Saturday October 25 2014, @10:28PM
https://www.youtube.com/watch?v=SNTZ7MY2rl8 [youtube.com]
(Score: 3, Funny) by jcross on Saturday October 25 2014, @11:49PM
The dudes in white coats in the video seem to be pretty casual about walking alongside the path of this presumably deadly laser!
(Score: 0) by Anonymous Coward on Sunday October 26 2014, @03:32AM
This video is unavailable with Safety Mode enabled. To view this video, you will need to disable Safety Mode.
What's that all about?
(Score: 2) by maxwell demon on Sunday October 26 2014, @09:00PM
Of course, with safety mode enabled, potentially deadly lasers are not allowed. ;-)
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by FatPhil on Sunday October 26 2014, @09:40AM
http://www.youtube.com/watch?v=-fSqFWcb4rE
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 2) by RobotMonster on Sunday October 26 2014, @01:02PM
But but thats unpossible! The TFA clearly states "cameras recording billions of frames per second do not exist" !
:-)
(Score: 2) by FatPhil on Sunday October 26 2014, @03:01PM
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 2) by RobotMonster on Sunday October 26 2014, @09:19PM
What about this one that can capture chemical reactions?
http://gizmodo.com/the-worlds-faster-camera-can-picture-chemical-reactions-1619277582 [gizmodo.com]
Its optical shutter shoots images consecutively in less than one-trillionth of a second at a resolution of 450 x 450 pixels!
(Score: 2) by FatPhil on Sunday October 26 2014, @11:08PM
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 1) by Horse With Stripes on Saturday October 25 2014, @11:58PM
Imagine a shark the size of an oil tanker. Now strap a giant laser to its head. Mission accomplished.
(Score: 2) by Subsentient on Sunday October 26 2014, @01:30AM
A death-star-like laser weapon looks like a death star. Durr!
"It is no measure of health to be well adjusted to a profoundly sick society." -Jiddu Krishnamurti
(Score: 0) by Anonymous Coward on Sunday October 26 2014, @02:16AM
I was under the impression, from an ancient story on the now-crapulent green site, that there's a limit to how much power you can put into a laser beam. I'm unable to find any supporting information for this, but from what I read in that now-unknown story, beyond a certain power level, a laser beam will start to form crystals.
Given how half-remembered this is, I could be completely wrong. I'm quite interested to know for sure, though.
No, learning physics won't help, in my particular case. I have a non-verbal learning disability, which means that useful information doesn't coalesce for me, from equations.
(Score: 0) by Anonymous Coward on Sunday October 26 2014, @08:24AM
Crystals of what?
The theoretical maximum energy density for a laser beam is when the mass energy equivalent is enough to collapse into a black hole.
If it's not in a vacuum then a practical limit tends to be when it ionizes the gas it's passing through.
(Score: 2) by HiThere on Sunday October 26 2014, @07:39PM
The laser beam in the story was beyond the point at which it starts ionizing the air it passes through, so that suggestion is wrong.
FWIW I have a vague memory of crystallized photons being produced in some experiment involving lasers. Just what the conditions were, or what they meant by that I'm not sure, but one of the results was that the photons slowed down considerably. This was done somewhere in New England (possibly MIT) and reported in either Science News or the Scientific American within the last year. Trace it down if you're interested enough, but I don't think it relates to how strong a laser beam can get.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by VLM on Sunday October 26 2014, @08:28PM
"one of the results was that the photons slowed down considerably"
All transparent substances slow light down at a different rate. Its a simplification, but thats how lenses work. Probably you got a generic press release along the lines of some type of new substance being ridiculously slow.
(Score: 2) by HiThere on Monday October 27 2014, @05:43PM
No, this was a research report, but the popularization didn't mention the in detail conditions. However the slow down was related to the "crystalization" of the photons. I think they may have been using some sort of bose-concentrate. What the report said before popularization, however, may have been very different...I didn't check.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.