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Engineers create 'optical cloaking' design for invisibility

 
"color keying"
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04/02/2007 09:19 PM
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Engineers create 'optical cloaking' design for invisibility
[link to www.physorg.com]

Researchers using nanotechnology have taken a step toward creating an "optical cloaking" device that could render objects invisible by guiding light around anything placed inside this "cloak."




The Purdue University engineers, following mathematical guidelines devised in 2006 by physicists in the United Kingdom, have created a theoretical design that uses an array of tiny needles radiating outward from a central spoke. The design, which resembles a round hairbrush, would bend light around the object being cloaked. Background objects would be visible but not the object surrounded by the cylindrical array of nano-needles, said Vladimir Shalaev, Purdue's Robert and Anne Burnett Professor of Electrical and Computer Engineering.

[link to www.physorg.com]
These two images (Cloak off, top. Cloak on, bottom) were taken from corresponding videos depicting scientific simulations performed at Purdue to show how objects might be "cloaked" to render them invisible. The new findings demonstrate how to cloak objects for any single wavelength, not for the entire frequency range of the visible spectrum. But the research represent a step toward creating an optical cloaking device that might work one day for all wavelengths of visible light. The videos show how light interacts with an uncloaked and cloaked object. When uncloaked, as depicted in the first image, light waves strike the object and bounce backward. As depicted in the second image, a cloaking device designed using nanotechnology guides light around anything placed inside this cloak. Credit: Birck Nanotechnology Center, Purdue University
The design does, however, have a major limitation: It works only for any single wavelength, and not for the entire frequency range of the visible spectrum, Shalaev said.

"But this is a first design step toward creating an optical cloaking device that might work for all wavelengths of visible light," he said.

Research findings are detailed in a paper appearing this month in the journal Nature Photonics. The paper, which is appearing online this week, was co-authored by doctoral students Wenshan Cai and Uday K. Chettiar, research scientist Alexander V. Kildishev and Shalaev, all in Purdue's School of Electrical and Computer Engineering.

Calculations indicate the device would make an object invisible in a wavelength of 632.8 nanometers, which corresponds to the color red. The same design, however, could be used to create a cloak for any other single wavelength in the visible spectrum, Shalaev said.

"How to create a design that works for all colors of visible light at the same time will be a big technical challenge, but we believe it's possible," he said. "It is clearly doable. In principle, this cloak could be arbitrarily large, as large as a person or an aircraft."

The research is based at the Birck Nanotechnology Center at Purdue's Discovery Park.

Other researchers published findings in 2006 describing the mathematics generally required for the optical cloaking device. Those researchers include: John Pendry at the Imperial College in London, along with David Schurig and David R. Smith at Duke University, and simultaneously, Ulf Leonhardt at the University of St. Andrews in Scotland.

"These mathematical requirements were very general, and then we determined how to fulfill the requirements with a specific design," Shalaev said.

Leonhardt, a professor of theoretical physics, wrote a commentary piece about the Purdue paper appearing in the same issue of Nature Photonics. In the commentary, he compares the Purdue design to the Roman creation of "the first optical metamaterial," a type of glass containing nanometer-scale particles of gold. In ordinary daylight, a cup made of the glass appeared green, but then it glowed ruby when illuminated from the inside.

The Purdue research, Leonhardt writes, represents " ... theoretical simulations that show that a modified Roman cup based on modern nanofabrication technology will act as an invisibility device ... Any object you put inside will disappear as if dissolved in air, provided it is viewed through polarizing tinted glasses of precisely that colour."

Other researchers have developed concepts for cloaking objects smaller than the wavelengths of visible light and for objects detected in the microwave range of the spectrum, which are much larger than the wavelengths of visible light. But the new design is the first for cloaking an arbitrary object in the range of light visible to humans.

"What we propose is the cloaking of objects of any shape and size," Shalaev said.

Two requirements are needed to render an object invisible: Light must not reflect off of the object, and the light must bend around the object so that people would see only the background and not the cloaked object itself.

"If you satisfied only the first requirement of preventing light from reflecting off of the object, you would still see the dark shadowlike shape of the object, so you would know something was there," Shalaev said. "The most difficult requirement is to bend light around the cloaked object so that the background is visible but not the object being cloaked. The viewer would, in effect, be seeing around, or through, the object."

The device would be made of so-called "non-magnetic metamaterials." Meta in Greek means beyond, so the term metamaterial means to create something that doesn't exist in nature. Unlike designs for invisibility in the microwave range, the new design has no magnetic properties. Having no magnetic properties makes it much easier to cloak objects in the visible range but also causes a small amount of light to reflect off of the cloaked object.


"But this could, in principle, be offset by other means, for example, with antireflective coatings," Shalaev said. "The big challenge is how to make rays bend around the object, which we have described how to do in this paper."

A key factor in the design is the ability to reduce the "index of refraction" to less than 1. Refraction occurs as electromagnetic waves, including light, bend when passing from one material into another. Refraction causes the bent-stick-in-water effect, which occurs when a stick placed in a glass of water appears bent when viewed from the outside. Each material has its own refraction index, which describes how much light will bend in that particular material and defines how much the speed of light slows down while passing through a material.

Natural materials typically have refractive indices greater than 1.The new design reduces a refractive index to values gradually varying from zero at the inner surface of the cloak, to 1 at the outer surface of the cloak, which is required to guide light around the cloaked object.

Creating the tiny needles would require the same sort of equipment already used to fabricate nanotech devices. The needles in the theoretical design are about as wide as 10 nanometers, or billionths of a meter, and as long as hundreds of nanometers. They would be arranged in layers emanating from a central spoke in a cylindrical shape. A single nanometer is roughly the size of 20 hydrogen atoms strung together.

Although the design would work only for one frequency, it still might have applications, such as producing a cloaking system to make soldiers invisible to night-vision goggles.

"Because night-imaging systems detect only a specific wavelength, you could, in theory, design something that cloaks in that narrow band of light," Shalaev said.

Another possible application is to cloak objects from "laser designators" used by the military to illuminate a target, he said.

Leonhardt says in his commentary that creating a cloak for rendering total invisibility in the entire visible spectrum would require "further advances in optical metamaterials, new combinations of nanotechnology with highly abstract ideas ..."


Source: Purdue University
» Next Article in Physics - Physics: Research on microfluidics widens the possibilities for electronic devices
to reveal another image ' (OP)
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Re: Engineers create 'optical cloaking' design for invisibility
Chroma key



A chroma key is the removal of a color (or small color range) from one image to reveal another image 'behind' it. The removed color becomes transparent. This technique is also referred to as "color keying", "colour-separation overlay" ("CSO") (primarily by the BBC[1]), "greenscreen" and "bluescreen". It is commonly used for weather forecast broadcasts, wherein the presenter appears to be standing in front of a large map, but in the studio it is actually a large blue or green background.


The process
[link to en.wikipedia.org]
Anonymous Coward (OP)
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04/02/2007 09:27 PM
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Re: Engineers create 'optical cloaking' design for invisibility
Re: The Two Humanitys a theoritical history
"The Blue Screen / Chroma Key Page"

What is Blue Screen Imaging?


[link to www.seanet.com]



Blue Krishna
As in more traditional depictions of Krishna, blue represents the vastness of the sea as infinity

[link to www.krishnaconcepts.com]
 Quoting: Anonymous Coward 90967

[link to www.godlikeproductions.com]
Anonymous Coward (OP)
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Re: Engineers create 'optical cloaking' design for invisibility
Chinese discovery casts doubt on 'Out of Africa' theory: study

The ancient remains of an early modern human found in Beijing suggests the "Out of Africa" theory of the dispersal of humans may be more complex than first thought, a study released Monday said.

The fossilized remains date to 38,000 to 42,000 years ago, making it the oldest modern human skeleton from eastern Eurasia, and one of the oldest modern humans from the region, the authors of the paper said.

[link to www.physorg.com]
Anonymous Coward (OP)
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Re: Engineers create 'optical cloaking' design for invisibility
oops
wing-ed

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04/02/2007 10:11 PM

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Re: Engineers create 'optical cloaking' design for invisibility
Chinese discovery casts doubt on 'Out of Africa' theory: study

The ancient remains of an early modern human found in Beijing suggests the "Out of Africa" theory of the dispersal of humans may be more complex than first thought, a study released Monday said.

The fossilized remains date to 38,000 to 42,000 years ago, making it the oldest modern human skeleton from eastern Eurasia, and one of the oldest modern humans from the region, the authors of the paper said.

[link to www.physorg.com]
 Quoting: Anonymous Coward 90967

Praise The Holy Of Holy :: They do not list a method of dating the bones! Who guessed? Praise The Lamb: Amen
Holy, holy,holy, Lord God Almighty, which was, and is, and is to come.Praise the one who gives you peace beyond all understanding Yes that scripture still sounds good !
Anonymous Coward (OP)
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04/03/2007 11:10 AM
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Re: Engineers create 'optical cloaking' design for invisibility
Praise The Holy Of Holy ::
:1dunno1`:
Anonymous Coward (OP)
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04/03/2007 11:11 AM
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Re: Engineers create 'optical cloaking' design for invisibility
hf-ed
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03/20/2009 02:48 PM
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Re: Engineers create 'optical cloaking' design for invisibility
New invisibility cloak allows object to 'see' out through the cloak
March 13th, 2009 By Miranda Marquit (PhysOrg.com) --

"Many groups have been working devices that make objects invisible," Che Ting Chan tells PhysOrg.com. “Most of these devices, however, encompass the object to be cloaked.” Chan, a scientist at The Hong Kong University of Science and Technology, believes that it is possible to create a cloaking device that would be able to render an object invisible without encompassing it.
[link to www.physorg.com]
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Re: Engineers create 'optical cloaking' design for invisibility
With the devices that encompass the object,” Chan continues, “the cloaked subject is ‘blind’. It can’t ‘see’ out through the cloak. We can’t see the object, but the object can’t see us, either. We wanted to create a conceptual design that would let the object ‘see’ out through the cloak while hiding it from sight.” Along with Yun Lai, Huanyang Chen and Zhao-Qing Zhang, Chan believes that this could be accomplished. Their ideas are published in Physical Review Letters: “Complementary Media Invisibility Cloak that Cloaks Objects at a Distance Outside the Cloaking Shell.”

Right now, such a device exists only theory. “We haven’t built the device,” Chan says, “but we have shown mathematically how it could work. It is a very specific description of the materials needed. If you have the time and resources, we think it could be done.” He points out that it might have interesting possibilities in a number of fields where invisibility might be desirable.

Theoretically, a device such as Chan suggests, would work through complementary media. “Our strategy is to put the cloaking device and the object to be cloak next to each other. The cloaking device is a kind of anti-object. The way the light is gathered and scattered by the two objects - the cloaking device and the object it is making invisible - would cancel each other out.” Chan continues by explaining that the cloaking device would become invisible as well. “Both must be invisible in order for this to be effective, and I think we have shown in theory how this could work.”

[link to www.physorg.com]
Anonymous Coward
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Re: Engineers create 'optical cloaking' design for invisibility
Science is beginning to sound more like magic by the day.

More information: Yun Lai, Huanyang Chen, Zhao-Qing Zhang, and C. T. Chan, “Complementary Media Invisibility Cloak that Cloaks Objects at a Distance Outside the Cloaking Shell.” Physical Review Letters (2009). Available online: [link to link.aps.org] .

[link to images.google.com]
Anonymous Coward
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Re: Engineers create 'optical cloaking' design for invisibility
[link to images.google.com]



[link to www.eurekalert.org]

Animation of the Action Density in 4 Dimensions - 1543 kb
Half Size - 520 kb
[link to www.physics.adelaide.edu.au]
[link to www.physics.adelaide.edu.au]
Anonymous Coward
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03/20/2009 03:08 PM
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Re: Engineers create 'optical cloaking' design for invisibility
this is useful.

"I honestly didn't see those government agents trespassing on my property. I was just shooting at some targets out there in the field.
Anonymous Coward
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Re: Engineers create 'optical cloaking' design for invisibility
~jst [link to www.capca.ucalgary.ca]
three quarks
trick arcs
[link to etymology.vox.com]
Anonymous Coward
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Re: Engineers create 'optical cloaking' design for invisibility
this is useful.

"I honestly didn't see those government agents trespassing on my property. I was just shooting at some targets out there in the field.
 Quoting: Anonymous Coward 182970

"Magic on the Menu" is the other show by the Three Magicians
Sentient Primate

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03/20/2009 03:12 PM
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Re: Engineers create 'optical cloaking' design for invisibility
That was a line drawing. It ain't shit.

bsflag bsflag bsflag bsflag bsflag bsflag bsflag
That does not compute.
Anonymous Coward
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03/20/2009 03:15 PM
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Re: Engineers create 'optical cloaking' design for invisibility
[link to images.google.com]

~ bio in sl. means (he) was

[link to www.cosmicastronomy.com]

[link to images.google.com]
A neutron star consist of neutrons, which in turn is built up by quarks. The quarks are confined in the neutrons. In a quark star the quarks are deconfined, that is they are free particles that are not confined in nucleons. In addition, quark stars also include the strange quark.


[link to www.desy.de]
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SP s226
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Re: Engineers create 'optical cloaking' design for invisibility
[link to www.contracosta.cc.ca.us]
[link to www.fcps.edu]
[link to www.fcps.edu]
The Pythagorean Spiral Project
You will use compass constructions to create a poster of the Pythagorean spiral. The result needs to be colored and may be creatively decorated.
[link to www.fcps.edu]
You will need to turn in your poster and a separate piece of paper with all calculations.

Materials: + poster board + ruler + compass + pencil, colored pencils or markers



nibiruancouncil

orbs
[link to www.nibiruancouncil.com]
The 3 Earth Grand Experiments [link to www.nibiruancouncil.com]
"space time"
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Space-Time Cloak Possible, Could Make Events Disappear?

Material would adjust speed of light to hide actions, physicists say.


[link to images.nationalgeographic.com]

Fiber optic cables (pictured) could help prove the theories behind the new "space time" cloak concept
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Re: Engineers create 'optical cloaking' design for invisibility
Space-Time Cloak Possible, Could Make Events Disappear?

Material would adjust speed of light to hide actions, physicists say.





Richard A. Lovett

for National Geographic News

Published July 11, 2011
[link to news.nationalgeographic.com]

It's no illusion: Science has found a way to make not just objects but entire events disappear, experts say.

According to new research by British physicists, it's theoretically possible to create a material that can hide an entire bank heist from human eyes and surveillance cameras.

"The concepts are basically quite simple," said Paul Kinsler, a physicist at Imperial College London, who created the idea with colleagues Martin McCall and Alberto Favaro.

Unlike invisibility cloaks—some of which have been made to work at very small scales—the event cloak would do more than bend light around an object.

(Also see "Acoustic 'Invisibility' Cloaks Possible, Study Says.")

Instead this cloak would use special materials filled with metallic arrays designed to adjust the speed of light passing through.

In theory, the cloak would slow down light coming into the robbery scene while the safecracker is at work. When the robbery is complete, the process would be reversed, with the slowed light now racing to catch back up.


If the "before" and "after" visions are seamlessly stitched together, there should be no visible trace that anything untoward has happened. One second there's a closed safe, and the next second the safe has been emptied.

Event Cloak "Fun" but Challenging

The concept of an event cloak "is definitely an interesting idea and great fun," said invisibility researcher Ulf Leonhardt, a physicist at the University of St. Andrews in the U.K. who wasn't part of the study team.

Steve Cummer, a cloaking specialist at Duke University, calls the concept "interesting and exciting," but he thinks that actually making such a cloak would be "really, really challenging."

"All of the material parameters need to be time-varying in a very specific way," Cummer said by email.

Currently, nobody knows how to do that except in fiber optics, in which the speed of a signal can be varied by a few percent by changing the intensity of the light. (Related: "Nobel Prize in Physics Goes to 'Masters of Light.'")

"You can use an intense control beam to slow a signal down," Kinsler said. In that way, an event occurring inside a fiber optic cable—such as an electrical signal moving from "on" to "off"—could be hidden from view.

"You would see the fiber, but some event occurring in the fiber could be cloaked," he said. Such a proof of concept, he added, could be possible within a few years.

(Related: "Long-Distance Quantum Message May Advance Code Making, Code Breaking.")

Powerful Laser Key to Cloaking?

There are still a few hitches to address, though, before attempting such an experiment, according to the University of St. Andrews's Leonhardt.

For instance, being able to cloak an event lasting more than a few femtoseconds—one-millionth of a nanosecond—would require light from an immensely powerful laser, he said.

"The experiment is not entirely impossible, but it is at the limit of what one can do with present technology in an ordinary university laboratory," Leonhardt said.

(Related: "Fusion Power a Step Closer After Giant Laser Blast.")

Study co-author Kinsler agrees that the fiber optics experiment is a technological stretch, but he counters that the problem can be eliminated by using a miles-long cable, as is routinely done in telecommunications.

"You can reduce the required power by using a longer fiber," he said. That's because the duration of the event you can hide depends on how long you can delay the light. A longer cable would allow you to get a longer delay from the same percentage slowdown, which would take less power.

Still, it may be a long while before police have anything to worry about—the materials needed for speeding and slowing light precisely enough for a bank heist have yet to be invented.

The event-cloak story and an accompanying article by Leonhardt appear in a special issue of Physics World magazine published June 30.









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preet_kalsana

4:23 AM on July 13, 2011



While making a new discovery or Research, we Humans give more priority to what we can do unfortunately we give almost zero priority to what we shouldn't do.



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Mike Andrews

9:53 PM on July 12, 2011



A physicist is one who will eternally divide a resultant in half and think the end can never be reached. An engineer is one who, when close enough, simply reaches out and touches it. Cloaking looks nice on paper - wait for the engineer's verdict before investing in it though...



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zombieduck

7:11 PM on July 12, 2011



The writer of this article in an attempt to inject humor has made the process more sci-fi than it really is. I read an article a few months ago by a person who worked on the project and it explains the device in a more realistic fashion. I need to find it again, it is really interesting but not as sci-fi as being presented here.
GeekOfTheWeek

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07/13/2011 11:14 AM
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Re: Engineers create 'optical cloaking' design for invisibility
Well it's a lot easier than that... Imagine this:

LCD screens all over the object to hide. At the corners of these LCD screens you have cameras. Now add a server to place whats viewable on the camera, displayed onto the other side of the object onto the LCD screens... Wouldn't that be a lot easier?
I love physics. It bonds us eternally, it's what makes our computers work, it's what's in my morning cup of coffee, it's the thing that keeps the universe from vanishing due to lack of belief...

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