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Bessel Beam 'Tractor Beam' Concept Theoretically Demonstrated

Soulskill posted about 2 years ago | from the finally-asked-wil-wheaton-for-help dept.

Technology 54

cylonlover writes "Last year, NASA revealed it was evaluating three potential 'tractor beam' technologies to deliver planetary or atmospheric particles to a robotic rover or orbiting spacecraft. At the time, the third of these, which involved the use of a Bessel beam, only existed on paper. Researchers at Singapore's Agency for Science, Technology and Research (A*STAR) have now proven the theory behind the concept, demonstrating how a tractor beam can be realized in the real world – albeit on a very small scale (abstract)."

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"theoretically demonstrated" (4, Funny)

noh8rz3 (2593935) | about 2 years ago | (#40113295)

Bessel Beam 'Tractor Beam' Concept Theoretically Demonstrated

theoretically demonstrated? does not compute... pc load letter... explode!

Re:"theoretically demonstrated" (3, Informative)

Anonymous Coward | about 2 years ago | (#40113539)

Better (and longer) form:
Physical property demonstrated that (if extrapolated infinitely) would do cool things.

Apparently a "Bessel Beam" is a perfectly parallel laser. They demonstrated tiny amounts of net pull from hitting very small things with a sufficiently parallel laser. So if you could perfect the parallel aspect and put about 6 giga-universes of energy behind one, you'd get a Star Trek style tractor beam.

Re:"theoretically demonstrated" (1)

noh8rz3 (2593935) | about 2 years ago | (#40115351)

also, if you tried to use the tractor beam on anything, it would evaporate.

Re:"theoretically demonstrated" (0)

Anonymous Coward | more than 2 years ago | (#40123473)

So REALLY they've just invented a line of sight disassembly beam for a transporter/replicator. Now you just have to figure out how to reconstitute the material back into it's original shape at the other end :)

Re:"theoretically demonstrated" (1)

camperdave (969942) | about 2 years ago | (#40114727)

Bessel Beam 'Tractor Beam' Concept Theoretically Demonstrated

theoretically demonstrated? does not compute... pc load letter... explode!

What's the matter, my good chum? Have you never heard of a simulation?

Re:"theoretically demonstrated" (2)

noh8rz3 (2593935) | about 2 years ago | (#40115307)

if somethign is simulated you say it was simulated or modeled.

the headline should have read, "Theory Behind Bessel Beam 'Tractor Beam' Concept Demonstrated in Lab'

So how long until the drones can be armed by this? (3, Funny)

Eightbitgnosis (1571875) | about 2 years ago | (#40113433)

"Civilian No. 955,436,725, you have been found in a restricted area. You have no more points on your criminal record. You will now be taken the camp for wayward patriots to receive reeducation!"

Re:So how long until the drones can be armed by th (1)

X0563511 (793323) | more than 2 years ago | (#40116487)

Stanley Tweedle, Number 476329-43 Department 511 Level 4! Report to security!

Re:So how long until the drones can be armed by th (1)

bejiitas_wrath (825021) | more than 2 years ago | (#40117999)

Stanley Tweedle, Number 476329-43 Department 511 Level 4! Report to security!

Former assistant deputy backup courier for the Austral B Heretics.

Any experts out there? (2)

mykepredko (40154) | about 2 years ago | (#40113459)

The article isn't very helpful and the paper is only available for sale.

In the article it states that Bessel beams are unlike laser beams which "diffract or spread out as they propagate". I know laser beams diffract but I didn't think they spread out (and that was the whole point of them).

Can anybody explain exactly what's going on here and why are the Bessel beams imparting force/energy on the objects toward the beam source?

Thanx,

myke

Re:Any experts out there? (1)

Anonymous Coward | about 2 years ago | (#40113597)

I know laser beams diffract but I didn't think they spread out (and that was the whole point of them).

Since you don't understand that those are the same thing*, I suggest you go read wikipedia until you understand what diffraction is.

Okay, they're not the same thing -- diffraction is only one mechanism by which a beam can spread. Shine a laser beam through a lens some time to see another one demonstrated...

Re:Any experts out there? (1)

noh8rz3 (2593935) | about 2 years ago | (#40115367)

you're a douche.

Re:Any experts out there? (0)

Anonymous Coward | more than 2 years ago | (#40116295)

Welcome to the new slashdot, being crude and wrong gets you modded up. At least one person should be very ashamed. In a vacuum laser light shouldn't spread out. AC is trying to sound like they know something but utterly fail on understanding what another person is asking.

Re:Any experts out there? (0)

Anonymous Coward | more than 2 years ago | (#40117029)

In a vacuum laser light shouldn't spread out.

And yet it does.
At this point you have two choices:
1. Get a new comic book to source your "facts".
2. Inhale.

Re:Any experts out there? (1)

ceoyoyo (59147) | more than 2 years ago | (#40117653)

Why shouldn't it spread out? Perfectly collimated laser light wouldn't spread out, but such a thing is impossible, so it does.

The AC you replied to isn't very nice, but he's right.

Re:Any experts out there? (0)

Anonymous Coward | more than 2 years ago | (#40121475)

Welcome to the new slashdot, being crude and wrong gets you modded up.

Well, I got modded up for being crude. But you didn't get modded up for being wrong.

At least one person should be very ashamed.

Yes, you should.

In a vacuum laser light shouldn't spread out.

Diffraction, bitches! It works. [wikipedia.org] Unless you meant an infinite-aperture laser, which "shouldn't" spread, but also shouldn't exist, since everybody would be tripping over it, and there's nowhere to plug it in?

AC is trying to sound like they know something but utterly fail on understanding what another person is asking.

Yes. Yes you are.

Re:Any experts out there? (1)

Intrepid imaginaut (1970940) | about 2 years ago | (#40113599)

And more importantly can we use them to produce real artificial gravity?

Re:Any experts out there? (4, Funny)

Jellodyne (1876378) | about 2 years ago | (#40113697)

It looks to me that we could use this technology to produce artificial gravity for say, a person. There are some minor limitations -- since the tech only works on very small particles, you'd have to use a very high energy Bessel beam or possibly a conventional laser to completely vaporize the person, and then the Bessel beam would be able to act on them, pulling their individual particles in the direction of the floor.

Re:Any experts out there? (0)

Anonymous Coward | about 2 years ago | (#40114167)

All light, even laser light, spreads out as it propagates. There is ONE solution to the equations of light that provides for zero diffraction: the Bessel beam (known as J0). Unfortunately, a J0 beam has two really difficult properties: it is infinitely wide, and it contains an infinite amount of energy. Approximations of a J0 beam can be created, and these approximations are free of diffraction within a limited region. Once they leave this area they begin to diffract.

Re:Any experts out there? (0)

Anonymous Coward | about 2 years ago | (#40115215)

All light, even laser light, spreads out as it propagates. There is ONE solution to the equations of light that provides for zero diffraction: the Bessel beam (known as J0). Unfortunately, a J0 beam has two really difficult properties: it is infinitely wide, and it contains an infinite amount of energy. Approximations of a J0 beam can be created, and these approximations are free of diffraction within a limited region. Once they leave this area they begin to diffract.

Although the J0 (bessel) solution is the most popular to study, there are others. For example, there are the super-oscillitory versions and the mathieu (that have bessel harmonics). There are even solutions that are based on the parabolic cylindrical functions.

Re:Any experts out there? (1)

c0lo (1497653) | about 2 years ago | (#40115749)

Can anybody explain exactly what's going on here and why are the Bessel beams imparting force/energy on the objects toward the beam source?

Thanx,

myke

Bessel beams [wikipedia.org] .
Optical tweezing [wikipedia.org]

Re:Any experts out there? (1)

ChatHuant (801522) | about 2 years ago | (#40115849)

I know laser beams diffract but I didn't think they spread out

They do spread out, but the divergence angle is really small, and it also depends on the type of laser - some of them don't produce very well focused light.

To understand why it helps to look at a simplified laser design, like the one diagrammed here [wikipedia.org] , which uses a crystal rod for the resonating cavity (YAG in the diagram, or ruby in Maiman's original laser). The active medium is pumped by the flash lamp, and photons are generated randomly in the body of the crystal rod. Most of them exit immediately through the sides. Some happen to be emitted almost parallel to the long axis of the rod, and they get reflected by the mirrored ends. Most of those, emitted at a slight angle, end up exiting through the sides as well (maybe after a few reflections). A few happen to be moving very close to parallel to the axis, and get reflected between the mirrors again and again. Those photons cross the active medium many times and generate a lot of other photons with the same wavelength and phase (that's what's called "the LASER effect"). In the end, when some of them exit through the semi-transparent mirror at the end of the rod, they have ALMOST the same direction. That makes the laser ray so collimated, but a very small amount of divergence will still be present.

Re:Any experts out there? (3, Informative)

slew (2918) | more than 2 years ago | (#40115989)

The article isn't very helpful and the paper is only available for sale.

In the article it states that Bessel beams are unlike laser beams which "diffract or spread out as they propagate". I know laser beams diffract but I didn't think they spread out (and that was the whole point of them).

Diffract is the same as spread out over distance. The main thing about laser beams is that they are monochromatic (mostly), and with the proper construction, the beam that leaves the oscillation chamber is mostly in phase (other than laser "speckle"). The xy profile of the beam is another matter.

Most laser beams are constructed to have a mostly a gaussian profile which is really close to the diffraction-less bessel profile (both of which are unfortunately of infinite extent). The gaussian profile is a solution of the Helmholz harmonic oscillator pde in cylindrical coordinates using a paraxial (ray-tracing) approximation, and the Bessel profile is a solution that is a true plane wave (basically a better approximation). Of course you can't make either an gaussian or a bessel (they have infinite support), so it's only an approximation, and since it's an approximation, it will diverge (but slowly and bessel more slowly as it's a better approximation). Think of it as picking the goldilocks profile for the beam that's not too sharp on the edge (causing it to diffract away), and not too blurry and that the exact shape so that math works out so it has a constant envelope over time and distance.

Can anybody explain exactly what's going on here and why are the Bessel beams imparting force/energy on the objects toward the beam source?

From what I can tell it seems to be a bit complicated, but as I understand it the gist is that the laser beam creates an electromagnetic wave that interacts with the object's dielectric/magnetic permitivity and creates what is called a Poynting vector S = E x H (a cross product) which is a flux energy in a specific direction. By manipulating the relative polarlization of this laser beam (the Transverse Electric vs Transverse Magnetic components), you can create a situation where this cross-product vector is mostly pointing back to the source. So basically you set up a dipole in the object itself to help you. This effect is small, but if the time averaged beam profile is constant over distance so it doesn't have a z-gradient where it diverges so that the electric field is lower at greater distance (because you used a bessel beam profile), this small flux energy effect will have the tendency to drag the object towards the beam. If there was a z-gradient where the field was lower at greater distance because of diffraction, then that will probably counteract this effect and cause the object to be pushed out instead of tractor-ed in.

Re:Any experts out there? (0)

Anonymous Coward | more than 2 years ago | (#40116497)

A typical laser beam will either expand or shrink in beam width; for a typical Gaussian beam, there will be a beam waist where the beam is the thinnest. A theoretical Bessel beam is a beam that has an infinitely wide beam (although intensity drops off fairly fast from the center) and its beam profile (intensity of the cross section) is theoretically constant along propagation. It "diffracts" but while diffraction would shuffle around photon positions, the overall distribution of photons in a cross section remains constant and therefore it doesn't spread.

impossible to create (4, Interesting)

rbowen (112459) | about 2 years ago | (#40113477)

From the article:

  While true Bessel beams are impossible to create, as they would require an infinite amount of energy, ...

This would seem like a good reason not to use them, even in a government project.

Re:impossible to create (0)

Anonymous Coward | about 2 years ago | (#40113699)

This would seem like a good reason not to use them, even in a government project.

How so? Our current government has an infinite amount of money, and therefore can buy an infinite amount of energy, especially if it is green.

Re:impossible to create (0)

Anonymous Coward | about 2 years ago | (#40114901)

Nah, orange energy works better for this. Trust me, I've tried it with green before, and the results were not pretty.

Re:impossible to create (0)

Anonymous Coward | about 2 years ago | (#40114105)

An abstract Bessel beam (also known as a J0 beam) consists of a bright central beam and an infinite number of concentric annular beams. In physical reality we obviously can't construct such a light field, but approximations can be constructed, and these approximations are diffraction-less within a limit region. Remember, the speed of light is finite, therefore you can trade time for space in these sorts of approximations. If you want diffraction-less propagation within a 100 meter zone, then you do not need to construct the concentric annular components of the Bessel beam which are far enough away from the propagation axis that light could not travel that distance in the time it takes the main beam to go 100 meters.

Re:impossible to create (1)

jmerlin (1010641) | about 2 years ago | (#40114377)

We already have a device running that requires an infinite amount of energy: corporate greed. We're still struggling to turn that one off.

TFA says (0)

Anonymous Coward | about 2 years ago | (#40113493)

Bessel beams cannot be used to pull human/car as the huge laser intensity is likely to damage them. What kind of intensity are we talking about here? Can we coat them in some sort material (or put them in a container made of some special material) that can withstand the laser?

Re:TFA says (1)

MrShaggy (683273) | about 2 years ago | (#40113959)

Thats what the sharks are fore.

Re:TFA says (1)

X0563511 (793323) | more than 2 years ago | (#40116541)

An infinite amount of energy in an infinity large space is impossible, but if you treat those as "approaching infinite" you'll find the net energy for a given area inside to be approaching zero.

experimentally demonstrated tractor beams (0)

Anonymous Coward | about 2 years ago | (#40113567)

An actual experimental demonstration of a tractor beam already has been published. Link:

http://www.opticsinfobase.org/oe/fulltext.cfm?uri=oe-18-7-6988&id=196738

The practical tractor beam is based on "solenoid beams" of light that are projected
with computer-generated holograms. It only moves micrometer-scale objects over a
fraction of a millimeter, but it's a start.

Re:experimentally demonstrated tractor beams (1)

c0lo (1497653) | about 2 years ago | (#40115829)

Optical tweezing [wikipedia.org] had already a Nobel prize back in 1997.

A-Ha! (1)

Anonymous Coward | about 2 years ago | (#40113583)

So my comment earlier today about using a tractor beam to haul in the SpaceX Dragon not so stupid after all!

Re:A-Ha! (1)

VortexCortex (1117377) | about 2 years ago | (#40113865)

So my comment earlier today about using a tractor beam to haul in the SpaceX Dragon not so stupid after all!

Not so fast there bub: "Bessel beams are impossible to create, as they would require an infinite amount of energy"
We know the Universe doesn't contain that amount of energy...

Re:A-Ha! (1)

Gerzel (240421) | about 2 years ago | (#40114431)

No we do not.

We do not know how much energy the Universe contains because we cannot observe the entire universe. Even if restricted to the "observable" universe we are unable to examine it all.

The observed universe is not finite either as we don't know how many humans there have been nor how much of the universe each one has observed.

Re:A-Ha! (1)

X0563511 (793323) | more than 2 years ago | (#40116555)

Pop quiz! What's infinity squared?

Beam up my dandruff Scotty. (1)

warewolfsmith (196722) | about 2 years ago | (#40113771)

The future of dandruff removal looks bright, the Besseltron beckons...

AFSTAR (1)

Paul Carver (4555) | about 2 years ago | (#40113787)

I'm pretty sure that acronym should be AFSTAR, I've never heard of the word "for" being spelled with an asterisk.

Re:AFSTAR (1)

petsounds (593538) | about 2 years ago | (#40114533)

I guess someone just sees pathfinding algorithms wherever they go....

this is 6oatsex (-1)

Anonymous Coward | about 2 years ago | (#40113797)

Kill myself like the offici4l GAY obtain a copy of niggerness? And provide sodas, significantly Shouts To the

di3k (-1)

Anonymous Coward | about 2 years ago | (#40113879)

to be about doing myself. This isn't is busy infighting brain. It is the File was opened Ago, many of you a conscious stand

Re:di3k (1)

X0563511 (793323) | more than 2 years ago | (#40116567)

... did someone just divide by zero in here?

File with Perpetual Motion & Travel to the Pas (1)

VortexCortex (1117377) | about 2 years ago | (#40113907)

As, both require an infinite amount of energy.... Just like the damn Bessel Beam.

Re:File with Perpetual Motion & Travel to the (1)

X0563511 (793323) | more than 2 years ago | (#40116573)

Oh look, you tried to be a smartass and put body text into the subject, and you got truncated, bitch!

(seriously, don't do that.)

Simpler method (1)

ChrisMaple (607946) | more than 2 years ago | (#40115997)

Unfortunately, this won't work in a vacuum: In a uniform clear fluid medium with dielectric constant A, put a uniform clear flat object with dielectric constant B<A perpendicular to the light beam. Light shined through the object speeds up compared with its speed in the medium, and by conservation of momentum exerts a force toward the source of the light.
When the object moves through the medium, it is extracting energy/power from the beam. Because the object is moving, there are relativistic calculations that can be made predicting that the light on the backside will be redshifted by the amount of energy/power extracted.

But I'm pulling this all out of my @$$; I could easily be wrong.

Re:Simpler method (1)

samwichse (1056268) | more than 2 years ago | (#40116411)

Um, why wouldn't this work in a vacuum? They state that the beam hits particles and is scattered forward (as opposed to backward in regular scattering).

Thusly, individual particles are given momentum towards the source of the emitter. Seems like this would work best in a vacuum. imagine a probe uses a laser to vaporize part of an object, then this beam would shine on the vapor drawing it through the vacuum to a collector.

Sam

Re:Simpler method (1)

ceoyoyo (59147) | more than 2 years ago | (#40117707)

Because in a vacuum the beam is already travelling at the maximum possible speed. The photons can only slow down when they enter the object.

That's the reason according to the GP's explanation. I don't think his explanation is actually correct (although it would work in limited circumstances).

Re:Simpler method (1)

leromarinvit (1462031) | more than 2 years ago | (#40124589)

Wouldn't the photons exiting the object on the other side exert the same force in the opposite direction? Seems like this would only work for infinitely long objects. Or, if the object were at least long enough that it takes the photons a significant time to travel through it, one could maybe use it to pull it a little closer (while the front of the beam hasn't yet arrived at the end) and hold it there while the beam is active, and make it bounce back by stopping the beam.

(If this works at all; IANAP, I've pulled this out of the same orifice you did, and I didn't even think it through long enough to find any obvious flaws.)

Re:Simpler method (1)

leromarinvit (1462031) | more than 2 years ago | (#40124625)

One more thought, and sorry for replying to myself: If you constantly increased the intensity of the beam, you could probably keep pulling it. But to even maintain the position would require continuous power proportional to the distance you pulled the object in the first place.

bi73h (-1)

Anonymous Coward | more than 2 years ago | (#40117465)

FreeBSD went out GNAA (GAY NIGGER sales and so on, fucking confirmed: head spinning visit and shower. For and promotes our

The only problem with it is... (1)

bratwiz (635601) | more than 2 years ago | (#40128489)

The only problem with it is, it requires a good supply of Transparent Aluminum.

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