Talk:Metamaterial

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Help with this template Comments: edit – history – watch – refresh The first metamaterials were developed by W.E. Kock in the late 1940's Metal-lens antennas, IRE Proc., 34 November 1946, pp. 828-836 and Metallic delay lenses, Bell. Sys. Tech. Jour.,27, January 1948, pp. 58-82. The book Antennas Theory and Practice by Sergi A. Schelkunoff copyright 1952 by Bell Labs describes metal lens antennas in chapters 19.9 through 19.12.

Is the diagram correct? It appears to contradict the later statement in the article "but rays are refracted away from the normal on entering the material" whereas the diagram has the rays being refracted closer to the normal, and more surprisingly, on the other side of the normal. If the diagram is wrong can someone delete it please.

The diagram is correct; I've corrected the text. See, if N1 sin theta1 = N2 sin theta2 and N1 and N2 have opposite signs, then theta1 and theta2 must have opposite signs as well; following the usual sign convention, this means that they are on the same side of the normal. User:Ben Standeven as 70.129.35.107 06:17, 13 July 2006 (UTC)

Can/should we talk about superlenses here? Can someone at least answer some of the basic questions? Like do the concave/convex lenses work opposite from a regular lens?

Why is it that the only meta-material that is talked about is negative refractive index? Shouldn't that get its own page then?

As long as there's enough information on "metamaterial" to justify a page with that heading, negative index lenses should probably be under here. Way too easy to get a horde of small pages for many topics otherwise. As for non-NI materials, the only other case that comes to mind at present is the use of comb-shaped structures to polarize microwaves (reflects waves polarized in one direction, transmits waves polarized perpendicularly to that). Probably other examples for microwave-frequency use that I'm overlooking, but NI materials are popular because they're potentially so useful (lenses that are allegedly not diffraction-limited). --Christopher Thomas 04:36, 25 May 2005 (UTC)

Question for optics people out there - do photonic crystals (photonic band-gap structures) count as metamaterials? They seem to satisfy the definition written in metamaterial, but I might be missing some subtle distinction. --Christopher Thomas 04:37, 25 May 2005 (UTC)

No, one basic properties of metamaterials is that they are homogeneous on a wavelength scale. The interaction of the material with light must come from sub-wavelength scaled features. Photonic crystals, on the other hand, are structure with features of about one wavelength long; diffraction around these features is the main effect here. The definition of metamaterials in the article should maybe be modified to refelect this.

Contents 1 2nd and 3rd intro paragraphs 2 Superlens 3 Theoretical Models, 2nd and 3rd Paragraphs 4 Pop Sci 5 Size ambiguity 6 Example of Negative refraction index 7 NRIs -1 < N < 0? 8 Breakthrough? 9 Possible Factual Error

[edit] 2nd and 3rd intro paragraphs

Hi, I couldn't follow the connection between the 2nd and 3rd paragraphs. Could some one in the know edit this article and make these two paragraphs flow better ? Thanks -kg

I took a stab at this. How does it look now? --Christopher Thomas 05:43, 26 May 2005 (UTC)

Much better! thanks! --Kaushik

[edit] Superlens

The superlens created at Berkley did not have a negative index of refraction. All materials with a negative index of refraction are for microwave frequencies. See Superlens —This unsigned comment was added by 67.189.113.62 (talk • contribs) on 03:04, 20 March 2006.

[edit] Theoretical Models, 2nd and 3rd Paragraphs

It says that a 'C' ring with is axis in the propogation direction (I assume this means the ring is flat to oncoming radiation) would produce negative permeability. In fact, this only creates negative permitivitty. Negative permeability is created when propagation is in the plane of the ring and the B field then acts perpendicular to the loop. This is not possible if the axis of the ring is alined with the propogation vector of the light. See "Stefan Linden et. al., Magnetic Response of Metamaterials at 100 Terahertz, www.sciencemag.org, Vol 306, 19th Nov 2004, pg 1351-1353" for diagrams of permeability and permitivity with different orientations in respect to the incoming light.

Although it does say that "an induced current is created and the generated field is perpendicular to the magnetic field of the light. The magnetic resonance results in a negative permeability; the index is negative as well.", this is not magnetic resonsnace; the B field would have to be in the same direction of the normal of the loop (or have a component thereof) to create a current and then the induced field could not possibly be perpendicular to the driving field (just think Lenz's Law). If I'm missing something pleae feel free to enlighten me. —The preceding unsigned comment was added by 137.132.3.12 (talk • contribs) on 07:48, 31 August 2006.

[edit] Pop Sci

According to the article "Unveiling the first invisibility shield" in Popular Science, light travels faster through a metamaterial than a vacuum. Was this a mistake? — Daniel 04:31, 21 September 2006 (UTC)

[edit] Size ambiguity

The phrase in the first line of the 2nd paragraph that reads "at least as small" is strange wording. Does that mean "at most as small"? In other words, as small or smaller? Please clarify. Unclepea 05:44, 20 October 2006 (UTC)

[edit] Example of Negative refraction index

Is the example at the end of the Nri paragraph correct?

"consider the following: a person submerged in a swimming pool filled with a hypothetical liquid with negative N would appear to float above the pool instead of appearing to be beneath the surface."

If the positive refraction index would make the submerged body look closer than it is, then the negative will make them appear "underneath" or even behind the view point. I think you have the idea of the Plane and the Normal the wrong way around in this example. Otherwise it's been explained very well.

Daniel --80.195.237.107 22:18, 30 October 2006 (UTC)

I see that my example of the person in the swimming pool has been removed. It was from a Scientific American article, so I'm pretty sure it was right.Rotiro 11:02, 14 March 2007 (UTC)

[edit] NRIs -1 < N < 0?

Can somebody explain how Snell's Law holds for NRIs between minus one and zero?

If we take N₁ to be 1 and Theta₁ to be 45 degrees, then use a negative N₂, say -0.2, then solving Sin(Theta₂) = Sin(45) / (-0.2) = -3.53~ has no solutions for N₂.

I ask because a metamaterial was recently produced with refractive index -0.6 for visible (780nm, red) light, and I'm still trying to figure out what it would 'look' like. The swimming pool discussions don't make much sense to me because, how on earth can something appear to be 'below me' when I'm standing on concrete. Wouldnt I just see concrete? 222.154.97.61 09:59, 19 December 2006 (UTC)

[edit] Breakthrough?

http://www.newscientisttech.com/article/dn10816.html 195.210.210.217 12:39, 19 December 2006 (UTC)

[edit] Possible Factual Error

In the subsection "Negative refractive index", there's a list of some cool properties of metamaterials with negative n. The last point in the list is: "Higher frequencies have longer, not shorter, wavelengths in such a material ". I've added a citation needed flag to this, as I haven't encountered it in the literature on this topic, and I have the feeling it might be incorrect. (It runs contrary to the definition of frequency, which is phase velocity/wavelength.)

Can anyone find the proper reference for this fact? (Otherwise, I think it should be deleted as a precaution...) GameGod 02:26, 2 January 2007 (UTC)

I was just wondering about that before you changed it. What would be the relationship between wavelentgh and frequency in that case, lambda = nw/c ?

18.95.7.45 20:58, 7 January 2007 (UTC) Matthieu