Talk:Metamaterial cloaking

Cleaning up

Okay, it is a good start to have this material moved to a separate page. However I think invisibility science is not a good choice of name, as it is overly broad. I assume that this page should focus on metamaterial-based and plasmonic cloaking (which have also been implemented with metamaterials at microwaves). Therefore I would suggest "Metamaterial Cloak", "Material Cloaking" or something similar. ShiftyDave (talk) 00:19, 29 December 2009 (UTC)

Well, these are both appropriate and good names. As you said, and I have discovered, metamaterial is not exactly defined, so plasmonic cloaking could fit with Metamaterial in the title. Material cloaking is also a good name because it also expresses the process. At the moment, I prefer Metamaterial cloaking, because it will relate to the other articles by name. However, I'll go with whatever you prefer, ShiftyDave. Steve Quinn (formerly Ti-30X) (talk) 03:43, 29 December 2009 (UTC)

Metamaterial cloaking (if the article aims at processes and technologies) or Metamaterial cloak (for specific realizations) sound more appropriate than the present title, to my ear. Dave, WP style recommendations are to capitalize only proper names, trade marks or alike (there are few more exceptions), thus cloaking instead of Cloaking. Materialscientist (talk) 03:49, 29 December 2009 (UTC)

I just made some minor spelling corrections. The only one I wasn't sure about was changing "diploar" to "dipolar". I couldn't find "diploar" in the dictionary or wikipedia, and couldn't tell whether its occurrences on the web were correct or also misspellings, given that "dipolar scattering" also appeared. Someone below spells it "diploar" repeatedly, but again I don't know if that's correct or a repeated mistake. NoJoy (talk) 20:56, 27 March 2010 (UTC)

Transformation optics

Since this article has been a stub since Feb. 2008, I merged the content from Transformation optics. That article in its current state is better served at "Invisibility science" where it can be developed as part of another article which includes this topic. Steve Quinn (formerly Ti-30X) (talk) 04:39, 29 December 2009 (UTC)

Page move

I went ahead and renamed "Invisibility science" to "Metamaterial cloaking". Steve Quinn (formerly Ti-30X) (talk) 23:02, 29 December 2009 (UTC)

Change name to Transformation optics

I reccomend changing the title of this article to Transformation optics, since there are other sections (and research) which utilize transformation optics besides cloaking. This would probably be a more accurate title (or something similar). Steve Quinn (formerly Ti-30X) (talk) 06:29, 30 January 2010 (UTC)

On second thought this article still needs to be developed, and there are other forms of cloaking. It may be better to simply spin off the other sections on metamaterial celestial mechanics later (including black holes etc.). It may be best to just wait and see, for now. Steve Quinn (formerly Ti-30X) (talk) 19:03, 30 January 2010 (UTC)

I'm surprised transformation optics isn't a separate article. TO-based cloaking is a subset of invisibility cloaking, but it is also a subset of TO-based devices. I have to imagine it's better to have a separate article including info about developments like beam benders, concentrators, super absorbers, and the like, with a link to the TO section of the cloaking article, than a half-sentence mention of all the other applications. 19:40 15 March 2010 —Preceding unsigned comment added by 152.3.196.93 (talk) 19:41, 15 March 2010 (UTC)

Thank you for your interest in this article. If you notice the banner on the top, the article is still under construction (being worked on). The other cloaking sections will be expanded, for sure. I see where Transformation optics has devices that are worth considering in another article. However, transformation optics plays a big role in this article. Hopefully, for now I have covered the intent to cover these areas in the introduction. Also, I think it is worth discussing the articles that are also included in TO but not explicity mentioned until the cloaking demonstration in 2006. These are "Controlling EM fields" and "Optical conformal mapping." I am working on these for some background to the actual cloaking in 2006, and then I go from there. There will probably a seperate article for TO, I am just not sure how, yet. Thanks. Steve Quinn (formerly Ti-30X) (talk) 06:48, 18 March 2010 (UTC)

(same unsigned user as before) I did note the construction tag, yes. I don't think a separate TO article would be very complicated. The meat could include:

• theory of coordinate transformations, including an example or two - constructing the Jacobian matrix from a general coordinate transformation
• theory underlying the invariant form of Maxwell's equations (how a spatial coordinate transform is equivalent to a material parameter transform) and how this can be used to engineer devices. That is, show that material parameters can be related to the Jacobian using form invariance
• specific example application of some sort, many of which are available
• list of examples of typical applications

The sections I propose could be written entirely without mentioning cloaking - examples could use subwavelength confinement, beam benders, or beam concentrators. I understand TO is important for metamaterial cloaking, but again - metamaterial cloaking using TO is a subset of TO applications, not vice versa. It doesn't make sense to me to have it structured this way - TO is a broader concept. There should be a brief description in a TO article about cloaking with a link to this one, and a link from this one to a more detailed and general TO article. Someone coming to this article is probably looking to see what's possible with current technology, and that's fine. If they want more detail about this transformation optics approach, especially noting that it's applicable to other devices/applications, they currently have nowhere to go. I'm not trying to be a pain, but as someone who actually deals with TO, the fact that there's no separate TO article seems silly to me. It's like having an MTI radar article but no general radar article, or a specific application of materials science without a general article on the same. —Preceding unsigned comment added by 66.57.254.204 (talk) 05:55, 19 March 2010 (UTC)

Sorry, I missed your last response until just now, I don't know how I overlooked it. I agree a seperate TO article makes sense, yes it is true that TO is a much broader category, and I have to agree with your general strategy for an article on this topic. So, coming very soon - an article entitled Transformation Optics. ----Steve Quinn (formerly Ti-30X) (talk) 03:54, 28 March 2010 (UTC)

Anonymous user: 66.57.254.204, or 152.3.196.93 - if you want want, feel free to leave a message on my talk page. Then I will be sure not to overlook your message. You can refer me to the talk page of the article or you can write your whole message on my talk page. If you are not familiar how to do this, just click on the "talk" adjacent to my User Name in my signature. It will take you to my "Wiki-personal" talk page. ----Steve Quinn (formerly Ti-30X) (talk) 04:05, 28 March 2010 (UTC)

I saw your suggestion at "Metamaterial" talk page. I have a response for you. Click on the link here: Sections development. -----Steve Quinn (formerly Ti-30X) (talk) 04:19, 28 March 2010 (UTC)

I'm finally coming back to this after a couple months. My ideas for the article are as follows:

• Disambiguation/introduction: specify that metamaterial cloaking deals with entirely passive methods to control the flow of radiation around objects (to be cloaked). There also exist active cloaking devices, such as ones that broadcast a captured video of the surroundings.
• Explanation of how entirely passive cloaking is theoretically difficult/important. It's easy to show (and has been many times in various literature) that placing a PEC cylinder around a 2D object will obscure any of its characteristics. Perhaps a small section/statement that this is true but does not provide invisibility, merely obscures the scattering signature of an object.
• Metamaterial cloaking should focus on the metamaterial aspect. The truly new thing with this is that, since we can effectively determine the material parameters of a region of space, we can redirect light around a region and - this is important - not provide a signature of the redirection. The article can also include explanation of how redirecting light in conventional ways introduces a signature. A PEC coating scatters, absorbing materials can be detected by bistatic means, etc. There could be an explanation that redirecting light entirely around an object without any signature requires extraordinary materials, which could be entirely derived from either the various original transformation optics papers (Leonhardt, Pendry, etc) or any of the many subsequent reviews. This section would also explain why metamaterials are necessary for cloaking devices of this sort. This naturally ties into the transformation optics regime closely, so we can include discussion of that. Moreover, the TO discussion can be split to different types of cloaking which are already present in this article:
• Coordinate expansion of a singularity/singular point in 1, 2, or 3 dimensions (the typical cylindrical cloak, including the one demonstrated by Smith et al)
• Coordinate expansion of a finite line segment (the broadband groundplane cloak and others)
• Other coordinate transformations
• Other types of transformations (the T-line cloak demonstrated by Tretyakov et al)
• Others, allowing room for expansion

I think something like this would focus the article on cloaking based on metamaterials and provide a good introduction to someone not familiar with the literature from a conceptual standpoint. RFenginerd (talk) 01:58, 25 May 2010 (UTC)

In order to keep this article simple and focused I merged blocks of content into two new articles. These are: Transformation optics and Varieties of cloaking theories. Take a look. At the moment I am really tired so I will re-read your newest response and comments later today or tomorrow - depending on your time zone. As additional note, I am trying to avoid being over-technical with the first sections of this article because it is a popular topic.

I just noticed that you mentioned coordinate transformations. This might fit best with Transformation optics. What you are discussing seems to be a really good fit in that article. Take a look and let me know what you think.  :>) ----Steve Quinn (formerly Ti-30X) (talk) 06:04, 25 May 2010 (UTC)

Good stuff. I've added a few things to a couple of the articles, primarily an increase in the conceptual part of the broadband/carpet cloak sections.

• OK I am back momentarily. The "active cloaking device" you are descrbing, at first, is actually active camouflage, apparently also known as adaptive camouflage. That is where you mention "broadcasting video", etc. If you have literature available regarding this topic I am sure your editing would be welcome in that article. Personally, I am trying to stay with metamaterials regarding cloaking devices. Also, I tend to stay in the Physics area, because many of these articles relate to all of the metamaterials.

I do have a few recent ones which I'll add in the near future, which are focused on the RF/microwave side more than optics.

This article "Metamaterial cloaking" now focuses on the metamaterial aspect. The actual scientific theory begins with the papers published by Pendry et. al, and Leonhardt respectively. Both papers published in Science (the journal) in 2006, both volume 312 (see references in this article and Transformation optics. This is followed by the actual demonstration, also in 2006. Then broad band cloak, then cloaking at infrared. That pretty much sums up this article so far. Also I like this phrase that you use: "merely obscures the scattering signature of an object". It is a good description, and useful. "Perhaps a small section/statement that this is true but does not provide invisibility" is a good idea, I agree. It is an accurate description of the current state of this research.

Sounds good to me. There is another Pendry paper from the 90s, actually, which shows the coordinate invariance of Maxwell's equations - I think the Pendry Science paper references it. I'll dig around and add it, including a bit of the background - that theoretically it was shown earlier that a spatial change was equivalent to a material change, but this was entirely theoretical until implemented/demonstrated using metamaterials.

You wrote: "The article can also include explanation of how redirecting light in conventional ways introduces a signature. A PEC coating scatters, absorbing materials can be detected by bistatic means, etc. There could be an explanation that redirecting light entirely around an object without any signature requires extraordinary materials, which could be entirely derived from either the various original transformation optics papers." Yes, this is very good. The only descrepancy I see is that Leonhardt notes that a perfect cloak is not possible in his article. However, he goes on to say that a small amount of imperfection is acceptable.

OK I will contiue to read the rest of what you wrote and respond here. I am taking it line by line - because so far so good. Hopefully, you understand it will take a little more time to respond to your suggestions above, but I will do so. Thanks for your interest. ----Steve Quinn (formerly Ti-30X) (talk) 18:46, 25 May 2010 (UTC)

Absolutely. I can add in plenty of text/references focused more on the conceptual side, or work on structure more, whatever's helpful. I haven't used the wiki templates a ton, so structural editing might take longer. I'm actually currently a grad student in one of the groups working on cloaking/transformation optics right now, so I'm very familiar with the literature/current state of the art. I'll help as I can with this and other metamaterial articles, and will definitely add extensively to the transformation optics article. RFenginerd (talk) 04:42, 27 May 2010 (UTC)

RFenginerd wrote: "It's easy to show (and has been many times in various literature) that placing a PEC cylinder around a 2D object will obscure any of its characteristics."

This is interesting, and I haven't come across this before, at least not that I recall. But, it would also be useful in the article. In fact I might look this up myself. In addition, I am wondering how much of a predecessor this phenomenon is to present day metamaterial cloaking research. One more thing, I just noticed that Wikipedia has a "stub" article on Perfect electric conductor. I have looked for this before, on Wikipedia, and for some reason was unable to come across it. If you have anything to add to this article, feel free. This term does show up in the metamaterial literature from time to time. ----Steve Quinn (formerly Ti-30X) (talk) 17:47, 27 May 2010 (UTC)

• You wrote: Explanation of how entirely passive cloaking is theoretically difficult/important.

There is some text in one or two of the sections where I have explained the current "drawbacks" or "limitations" involved with this work. If there are more that you would like to add, that would be good also. I think it is always best to be realisitic, and give an accurate description of the current state of metamaterial cloaking. In another vein, I am not sure that it is neccessary to emphasize that these are passive materials. I think, that by doing this it gives undue weight to unrelated research such as active camoflauge, which is entirely another approach and technique. When giving any emphasis to unrelated research this could dilute the focus of this article, and/or simply be off topic. Similarly, any kind of focus on stealth technology could have the same result. Also, stealth technology, is a well developed technology. Metamaterial cloaking is not developed at all. So, constrasting this research with stealth technology could be somewhat misleading. Cloaking with metamterials is not yet ready to steal the show, if you know what I mean. Ok I will respond to your other suggestions later. See ya. ----Steve Quinn (formerly Ti-30X) (talk) 17:47, 27 May 2010 (UTC)

Organization needed

The lead section of this article does not accurately convey the current content. It implies that, at the very least, the following topics will be described and discussed:

• Anomalous localized resonance
• Diploar scattering
• Tunneling light transmittance
• Sensors and active sources
• Transformation optics

Just skimming over this article, this doesn't appear to be the case. In fact, transformation optics seems to pervade more of the article than its heading suggests, while none of the other terms are defined or even used in an easily recognized form in the remainder of the article. And, of course, there's the ever-present problem of jargon-dense information without any more readily accessible introductions to each subtopic.

It seems to me that the chief problem of this article is that it has no organization; i.e., a well-defined subject that can be broken down into subtopics and arranged in a logical flow. I only ever got as far as an physics minor in college (not optics!), and my head spins trying to assess the content as it is. But I suspect that it might be assembled into something like this:

• [Lead section] – mostly done, although (A) metamaterial is not defined (anywhere in the article, in fact; a link is not enough), and (B) the last sentence is jarringly specific and should be moved elsewhere
• Science of cloaking – what it means to "cloak" something, or render it invisible; why it's a challenge (it could even be called "Quest for invisibility" if you want to get dramatic)
• Theoretical approaches – introduce subject, with at least a few sentences on why metamaterial is part of this article's title (i.e., why they're part of these cloaking approaches), then provide sections in the order described in the lead section
  • Anomalous localized resonance
  • Diploar scattering
  • Tunneling light transmittance
  • Sensors and active sources
  • Transformation optics
  • Broadband ground-plane cloak (?)
• Proposed applications
• Institutional research
• See also, etc.

Assuming this is a reasonable organization of the content, all the remaining material should go under one of these headings. (Even if transformation optics winds up being a huge subsection, the other approaches should have at least summary paragraphs as placeholders. The structure will show potential editors what's needed.) If they don't fit, then my suggestion isn't adequate, but some logical order and flow needs to be imposed. Also, the current "In the news" section doesn't belong here at all. If there is meaningful information to contribute from these media sightings, it should be incorporated into the text of the article with appropriate citations.

I realize that this article has gone through a few major transformations, which no doubt contributed to the problems. I hope my suggestions are of some use in fixing them. ~ Jeff Q (talk) 04:12, 24 February 2010 (UTC)

Jeff, thank you for your interest in this article, and your willingness to suggest a structure for organization. Yes, your suggestions are a very reasonable regarding organization of the content. In fact, from your suggestions I have gained insight into the need for the following:

• further defining a metamaterial,
• what it means to "cloak" something,
• why cloaking is a challenge,
• make the "jargon' more understandable,
• and try to specify why metamaterial is in the title of the article.

These are very good points, I will work on them one by one. Also, intergrating current news into the content, or sections of the article, sounds like a good idea as well.

You are correct in "saying" that most of the stuff in the second sentence, of the second paragraph, of the introduction - is not in the article. You are also correct that "Transformation optics" heavily dominates this article, at this time. You are noticing this because this article is currently in a state of flux, and is currently being rewritten from top to bottom (or bottom to top). When I first wrote this article it started with the metamaterial cloak (of Transformation optics) that you see here now. I am trying to finish this first.

The topics mentioned in the second sentence are subjects that I have just recently come across with the intention of adding them to the article once cloaking related to "transformation optics" is done, or at least written for editing later. You could say it is a matter of awareness. The more research I do, the more material I come across - if that makes sense.

The last sentence of the introduction is also a pointer or a guide to help me focus the content of this article. It is really nothing more than that. I will probably move this when I am done with this cloaking section. The cloaking section related to "Transformation optics" is comprised of at least three core journal articles: "Controlling Electromagnetic Fields", "Optical conformal mapping", and "Electromagnetic cloaking at microwave frequencies". The last two sections still need to be re-written. Then I will see what more recent research has been accomplished in this area.

Hopefully, my explanation here has been helpful to you. Feel free to add further comments as the article progresses. Ciao.

Steve Quinn (formerly Ti-30X) (talk) 05:05, 24 February 2010 (UTC)

Other cloaking theories

Merged content, except for the introduction, from Metamaterial cloaking to a new article. See revision history of this article and the new article, "Variteites of cloaking theories". This really needs its own article because these sections tend to veer off topic from the 'Metamaterial cloaking' article.

Since the first cloak in 2006, produced with gradient-index metamaterials, other invisibilty cloaking theories have been developed. "Variteites of cloaking theories" discusses the various cloaking theories, which have been published in peer reviewed, scientific articles. This is a review article which describes various theories. Except for a small summary, Metamaterial cloaking will not be discussed here because it already has its own article. However, some of the theories discussed here employ metamterials, but, perhaps in a different manner than the original demonstation and its succesor, the broad-band cloak.

Invisiblity-cloaking, in this context, is the scientific theory of appearing to render objects invisible to the electromagnetic spectrum. Of course the objects are really there, and only appear invisible ----Steve Quinn (formerly Ti-30X) (talk) 16:50, 24 May 2010 (UTC)

Invisible but not undetectable.

If you place a surface lets say a mirror behind the cloaked object and a pulsating light source and an optical sensor (like a camera) hooked up to a computer in front of it. Because the light travels around the object (as opposed to pass trough it like in a fictional cloak) it must undoubtedly create a slight delay meaning that light wich missed the cloak would return slightly faster and a fast enough computer with sensitive enough equipment would realise that something is cloaked infront of it. My question is if this delay is significant enough to be spotted by the naked eye? 81.233.213.183 (talk) 18:26, 11 December 2010 (UTC)

Sci-Fi Science

In case this is considered notable enough for a future update, maybe to the "In the news" section: metamaterial cloaking was the primary focus of an episode of the TV series "Sci Fi Science: Physics of the Impossible", hosted by Michio Kaku. The episode in question was the fifth of the first season, titled "How to Become Invisible", and aired on December 22nd 2009 on the Science Channel. Further information is on IMDb. 84.227.137.89 (talk) 02:45, 2 March 2011 (UTC)

Metamaterial cloaking makes the news

Presumably these reports mean that the article can be expanded ?

BBC: 'Antimagnet' joins list of invisibility approaches

and

NewScientist: Invisibility cloak to hide magnetic fields

EdwardLane (talk)

Radiation coming from inside the cloak

What happens to radiation coming from inside the cloak? The cloaked object will emit thermal radiation (mostly in the infrared range), what happens when this radiation hits the layer of metamaterial? Will it bounce back (which would cook a living being or anything with a power source), or will it pass through (though perhaps scrambled) and be visible to an observer outside? I'd say that's a very important question if you are talking about building actual cloaking devices 89.99.122.33 (talk) 19:46, 21 February 2013 (UTC)

Metascreen microwave invisibility cloak

Someone created an article on Ultra-thin invisibility Cloak. I have cleaned it up, renamed it Metascreen microwave invisibility cloak and given it proper references. I do not know whether it should be merged into this article.--Toddy1 (talk) 17:35, 21 April 2013 (UTC)

Unbased statements in "Why metamaterials are used"

The statement: "Every natural material so far only allows for a positive refractive index. " is not true. Already in 1969 optical lines in the far infrared with negative dispersion have been observed: Pine, A. S., and G. Dresselhaus. "Linear Wave-Vector Shifts in the Raman Spectrum of α-Quartz and Infrared Optical Activity." Physical Review 188.3 (1969): 1489. — Preceding unsigned comment added by 79.251.7.55 (talk) 17:17, 10 March 2014 (UTC)

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