Self-bending light boomerangs

[n2doc]

11 May 2012 by Justin Mullins

SELF-BENDING light beams capable of turning a corner like a boomerang are darting around an optics laboratory in France. The beams are just a few micrometres across, and could improve the way in which materials are carved on the microscopic scale, or help surgeons make curving incisions in the body that dodge specific regions or tissues.

Light normally travels in straight lines, but physicists have known for several years that superimposing a pattern on a laser beam can make it bend. The pattern is designed so that the individual light rays that make up the beam interfere with each other in a way that makes the beam curve.

However, a beam cannot normally bend by more than about 10 degrees without distorting. "The beam just doesn't keep its shape," says Mordechai Segev, at the Technion-Israel Institute of Technology in Haifa.

He and his colleagues took a deeper look at the problem by studying Maxwell's equations, fundamental laws covering the behaviour of electromagnetic waves. They calculated that it should be possible to make patterns that bend light beams by up to 180 degrees - an optical boomerang - without distorting them. The result, published in Physical Review Letters (DOI: 10.1103/PhysRevLett.108.163901), is purely theoretical.

Unknown to them, however, a team led by John Dudley at the University of Franche-Comté in Besançon, France, had been taking a practical approach to the same problem. Dudley's team began experimenting with bending beams and found that they could go beyond the 10-degree limit. "This gave us the idea that we could achieve much greater curves," says Dudley's colleague François Courvoisier.

more
http://www.newscientist.com/article/mg21428624.700-selfbending-light-boomerangs-could-help-surgeons.html

[ElboRuum]

1. I'll believe it when I have my lightsaber. n/t.

[DetlefK]

2. If you throw it, will it come back?

[laconicsax]

3. They do in Lucasarts-licensed video games.

[DetlefK]

4. Not in the movies.

In "Return of the Jedi", Darth Vader throws his lightsaber at Luke during their duel on board the Death Star. The lightsaber collapses the gangway Luke is standing on and Vader activates a spare lightsaber as he approaches.

EDIT: Damn, that's off-topic.

[ElboRuum]

5. Not really what I meant...

Last edited Wed May 16, 2012, 01:05 PM - Edit history (1)

At the risk of being perceived a person who has thought WAY WAY too much about this, I've put significant thought into what it would take to build an actual lightsaber.

Think about it.

Light goes straight as far as it can (putting aside bending around gravity wells), so what methodology could you use to cause it to just stop right in midair a sword's length from its emission point.

I find the following to be the best theory on "lightsaber tech" I can come up with.

Lightsaber is a misnomer. Plasmasaber might be a better name. It occurs to me that light in transit is not typically visible in midair unless it diffuses off of objects which can reflect the light into your eyes, so unless the lightsaber's emitter is pumping smoke or some other diffusive material into the light beam, we shouldn't really be seeing it.

Plasma can be "bottled" in magnetic fields and can emit light in wavelengths which can be visible to an observer. If one could create an open ended helical magnetic field to serve as a conduit for the plasma, it would look much like a lightsaber.

The strength of the helical field is proportional to the length of plasma from the emitter that can be effectively contained. The plasma which escapes past the point of effective containment interacts with the ostensibly cooler air around it, transferring its energy and losing its plasma state, making the plasma seem to "end" at some distance from the emitter.

The plasma itself would likely be very high temperature and act like a cutting torch when brought into contact with things, mimicking the behavior found in the movie lightsaber (instantly cauterizing the wounds it inflicts, being able to cut holes into blast shields and bulkheads, etc.)



What I meant was that with the capability to bend light back in on itself provides another possibility of lightsaber creation, although the blade itself would probably be invisible excepting to the hapless fool who ends up on the business end of it. However, as a safety feature to the person wielding it, one very well might pump a vapor into the light beams to make them visible so that you don't cut off your own bits by accident.

[DetlefK]

7. A plasma-lightsaber wouldn't work with just one hilt.

A magnetic bottle works by forcing the plasma to flow like spirals in a roughly cylindric volume. At the caps of the cylinder a magnetic field of high strength is needed, with the magnetic lines locally parallel to the axis of the cylinder, to reflect the plasma.

The hilt of the plasma-lightsaber could be one end of the magnetic bottle, but the other end would be open, as the magnetic field there would simply be too weak. Plasma would constantly leak out of your plasma-lightsaber and creating lethal amounts of plasma is technologically a real pain in the ass.

And as the article states, the "bending" is an interference-phenomenon.

[ElboRuum]

8. I am basing this on the premise...

...that the generation of energy in the Star Wars universe seems to be a rather child's-play thing. I believe some other person who thought way too much about things of this sort calculated the energy output of the Death Star's primary weapon reactor as greater than the energy output of a star.

So, I am assuming that scaling down the required high energy generation technology to a hand-held weapon would allow a relatively small device to generate an unexpectedly (by our standards) large amount of energy.

[DetlefK]

10. The problem isn't energy. Problem is, you can't build a magnetic bottle with just one magnet.

As I said, you need a magnetic field of a very specific configuration for a cylinder-like magnetic bottle: Each end where the plasma could leak out has to be capped by a locally strong magnetic field and it just doesn't work without another magnet. The plasma-lightsaber you proposed does not work with the laws of electromagnetism as we know them.

And for the plasma: Modern light-bulbs work with ionized gas. Please touch one while it's turned on and then tell me whether you want to wield a close-combat-weapon that's 1000 times hotter.

[laconicsax]

11. According to the lightsaber entry on Wookiepedia...

http://starwars.wikia.com/wiki/Lightsaber

The weapon consisted of a blade of pure plasma emitted from the hilt and suspended in a force containment field. The field contained the immense heat of the plasma, protecting the wielder, and allowed the blade to keep its shape.

Of course, the same entry states that the blade is massless, yet generates a strong gyroscopic effect...

[DetlefK]

12. So, it's a scifi-force-field, not a real-world magnetic bottle.

Wait a moment!!!!

The plasma of the blade is contained within the force-field, but there's still enough heat leaking out to cut metal?

And what happens, when the lightsaber is turned off? What happens to that plasma that's hot enough to set you accidently on fire?

What happens, if you wield a lightsaber near gasoline-fumes?

[laconicsax]

13. Well the question of what happens when you turn it off is answered in the movies.

The plasma retracts into the hilt, which is obviously made of fantastic meta-materials that can not only withstand the heat without melting, but completely protect the user from even minor burns.

[Hawkowl]

6. Light Sabers!

I've got dibs on the first ones!

[ElboRuum]

9. No Way!

Hey, Santa, I'd like a lightsaber for christmas!
No, you'll put an eye out!