Nanoantennas Can Change Phase of Light
Researchers at Purdue University found that arrays of plasmonic nanoantennas can be used to manipulate the phase, a wave shape, of light as it propagates.
The scientists now believe that they have found a path that could enable more powerful microscopes, telecommunications and computers. Specifically, the discovery is expected to have effects on technologies for "steering and shaping laser beams for military and communications applications, nanocircuits for computers that use light to process information, and new types of powerful lenses for microscopes."
The research builds on a previous modification how scientists have described how light reflects and refracts or bends while passing from one material into another, which is referred to as Snell's law. Each material has its own refraction index and all natural materials show positive refraction indexes. However, Purdue's nanoantennas can change the refraction and even achieve negative angles.
"Importantly, such dramatic deviation from the conventional Snell's law governing reflection and refraction occurs when light passes through structures that are actually much thinner than the width of the light's wavelengths, which is not possible using natural materials," said Vladimir Shalaev, scientific director of nanophotonics at Purdue's Birck Nanotechnology Center. "Also, not only the bending effect, refraction, but also the reflection of light can be dramatically modified by the antenna arrays on the interface, as the experiments showed."
According to the scientists, the nanoantennas feature V-shaped structures that are made of gold and are placed on top of a silicon layer. The antennas are 40 nm wide. Shalaev said that they are able to transmit light through an ultrathin "plasmonic nanoantenna layer" that is about 50 times smaller than the wavelength of light it is transmitting. "This ultrathin layer of plasmonic nanoantennas makes the phase of light change strongly and abruptly, causing light to change its propagation direction, as required by the momentum conservation for light passing through the interface between materials," Shalaev said.
Even tho in this case it would appear they just amended the law.
An angle greater than the angle of refraction, I would assume.
Refraction is based on the speed of light through a medium.
Snell's law was never "broken". Snell's law is based on classical models of the behavior of light at interfaces. Saying "Snell's law was broken (by Purdue researchers)" is a statement that shows a profound misunderstanding of physics being talked about. I'm not blaming people for misunderstanding, because much of the fault of scientific ignorance and confusing is a consequence of poor reporting and communication. Albeit things like this point to a gross lack of scientific literacy among the general public.
I'll come back to this article later to check.. meanwhile I'll check if TR and Wired for more info on this.
Negative refraction index:
http://www.rikenresearch.riken.jp/images/figures/hi_3837.jpg
Well, NASA is actually using that on a few probes out there !
They are building 'structures', functioning perfectly, that they will never be able to actually 'see'.
Imagine them at a party, some chick casually asks 'so what do you do for a living'. The response is likely to give her a migraine and she is off to the bar. :-)
I think it is cool that some scientists take this path, also a shame that it also means that most of your initial funding will likely be from various military concerns. You know, the 'defense' people...
The angle of refraction is what happens when light passes from one medium to another. They have to be two different materials with 2 different refractive indexes. The refraction is caused by light either slowing down or speeding up as a result of the medium change.
None of that explains how one acheives a negative angle.
I think what should be here instead of "negative angles" is "negative refraction indexes." Linking a relevant Wiki:
http://en.wikipedia.org/wiki/Refractive_index
Snell's Law says that Ni sin(theta_i) = Nr sin(theta_r), where i is for the incident ray (in air), r is for the refracted ray (in water), and the N's are the indices of refraction.
Since sin(-theta_r) = -sin(theta_r), I would think that a negative refraction angle should represent a ray going out with one component reversed, e.g. downward, but leftward. (The alternative would be upward and rightward, which would be a reflection back into the air.) The refracted ray would point in a different quadrant. For example, if you were standing on the moving end of a diving board and looked down into the water, you normally see the bottom of the pool in front of you; but, with a negative refraction angle, you would look forward and down and see the pool floor under the diving board and distorted.
An excellent picture. (I missed it before.)
(credit to Anonymous above)