Back to reality. Of course, I was never abducted, but I found a few articles {India Times, Geekologie, BBC} that describe lasers as the key to creating tractor beams. The first article describes a Bessel laser that has the ability to pull small objects toward the laser source. However, the physics behind the phenomenon was poorly described in the article. I find this to be a result of the scientist-journalist communication gap. Apparently the author of the article did not deem the specifics behind the Bessel laser to be of much importance, or he simply did not understand it. For a reader like myself, I had a hard time believing the vague explanation that was provided.
The first article left me wanting. I needed to learn more about the physics behind lasers as tractor beams. I found my way to the second article, which describes not a Bessel laser, but a hollow, or ring, laser. Particles in the center of the ring can be kept in the center of the ring due to the higher temperature surrounding the particles. This method can be used to create an "optical trap" for particles. Optical traps are used in many experiments, such as ones involving Bose-Einstein condensates. The trap can be translated to move the trapped particles. Nevertheless, I found the trap is less like a tractor beam than the Bessel laser was claimed to be, so I moved on.
I finally arrived at the BBC website that mentioned both technologies but gave more detail and analogies for the Bessel laser. In the end, it seems that Bessel lasers can only pull small particles tiny distances. The optical trap method has been able to move a cluster of particles over longer distances, like five feet.
Tractor beams? Not yet.
Someday? Maybe.
Hype? Absolutely.
The technology and idea is very cool, but its applications as of yet extend only to a few feet for a small mass. The titles of the articles I researched gave the impression of a large scale, UFO style tractor beam. Even the content said the beam would soon be used for large scale applications. That's hype if I've ever seen it.
Now let's go kick some alien butt!
What's limiting the mass/size/number of particles moved? I'm rather interested in this. Have you found any scholarly journal articles documenting this?
ReplyDeleteI love how you framed this article! Getting back at aliens gives me a more motivation to learn how lasers are being used in such ways! Very nicely done.
ReplyDeleteWhat exactly is meant by a Bessel laser? Do they actually exist or is this just a type of laser that the article was talking about?
Dan,
ReplyDeleteI found an article: "Backward Pulling Force from a Forward Propagating Beam" by Chen et al.
The article describes a polystyrene particle of about 4 um in diameter being pulled by a Bessel beam. The limit on the backward force depends on wavelength, intensity, position of the particle in the beam, and I think some other factors.
Aaron,
A Bessel beam is a laser that has a transverse spatial intensity profile like a Bessel function. A Bessel beam is tricky to make, but it has some interesting properties, like core regeneration (after the core of the beam is blocked by something) and that the core does not diverge as with Gaussian beams.
Thanks for the comments and questions!
Great post--as noted, an entertaining beginning.
ReplyDeleteFor me, the interesting comment is about the scientist-journalist gap. This seems particularly hard to overcome when it comes to physics. Wonder if you have any thoughts on this.
Yeah. Like we have discussed before, scientific journalists are getting the boot and sensational journalists are in. We all know how hard it is to communicate science to laypeople. That's part of the gap. The other part may be the experts trying to communicate to the communicators (journalists). Lots of places for confusion to occur.
ReplyDelete