[Flipside]

http://www.bbc.co.uk/news/science-environment-12620560

Apparently, a certain shaped Bessel laser can 'pull' objects towards the source...

[Mika]

Interesting stuff.

It's interesting to follow the recent works in the field of Optics. I expect to hear some kind of explanation for this in the upcoming conferences. The reason for the backwards pulling force is not immediately clear for me, and how this relates to radiation pressure is another thing.

At least they say it could, in principle, work with small pieces. That would be less than a nanometer, I would guess.

[headdie]

Very interesting in deed, be interesting to see how accurate these devices could be made in terms of positioning the affected particles

[Nuke]

id rather just use a john deere

[Klaustrophobia]

[T-LoW]

Always had this picture in mind

Pulling particles with lasers... hmmm. Sounds like a hell of a power consumption to even pull a grain of sand. But it's a start

[JCDNWarrior]

Well the actual level of technology we're at is far beyond what is advertised, so news like this shows that it is (almost) guaranteed to work, probably on a higher scale than a grain of sand.

Think of quantum mechanics based computers and the singularity experiments at CERN among others.

[Astronomiya]

Interesting stuff.

It's interesting to follow the recent works in the field of Optics. I expect to hear some kind of explanation for this in the upcoming conferences. The reason for the backwards pulling force is not immediately clear for me, and how this relates to radiation pressure is another thing.

At least they say it could, in principle, work with small pieces. That would be less than a nanometer, I would guess.

The article provides the mechanism.  Basically, from what I can tell, the Bessel beam's shape is such that when it is at glancing incidence to the object, pulls the object toward it.  As the article explains, the light that is radiated back at the beam (and some is, not a lot, but some) can be out of phase with the incoming beam and destructively interfere.  This interference creates a push towards the beam, since the reflected light is moving away from the beam source, so its momentum had to come from the object.  This mechanism would only work on a very small scale; as soon as macroscopic stuff got involved, even grains of sand, this effect would become negligible, as traditional reflection becomes dominant.  So no big tractor beams, sorry.

[watsisname]

What if we used REALLY HEUG wavelengths? D:

In seriousness, wouldn't the limiting size be increased by using longer wavelengths of light, since the diffraction pattern would be larger as well?  Then again I suppose the pulling force would be diminished as well since longer wavelengths supply less momentum.

[Mika]

The article provides the mechanism.  Basically, from what I can tell, the Bessel beam's shape is such that when it is at glancing incidence to the object, pulls the object toward it.  As the article explains, the light that is radiated back at the beam (and some is, not a lot, but some) can be out of phase with the incoming beam and destructively interfere.  This interference creates a push towards the beam, since the reflected light is moving away from the beam source, so its momentum had to come from the object.  This mechanism would only work on a very small scale; as soon as macroscopic stuff got involved, even grains of sand, this effect would become negligible, as traditional reflection becomes dominant.  So no big tractor beams, sorry.

Yeah, I read that article and how they explained it would work.

The listed size in the article is ~ 2 µm, after that the effect doesn't dominate. The work is purely theoretical, it will be interesting to hear if someone is able to do this experimentally.

[Flipside]

Yup, kind of guessed this happened at a minute scale, most interesting physics of this type usually lives in that sort of size-range, but still fascinating stuff