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Source: http://www.dailymail.co.uk/sciencetech/article-2150262/Scientists-capture-rainbow-using-25-000-miniscule-invisibility-cloaks.html
Scientists capture beams of light using 25,000 miniscule 'invisibility cloaks'
While the idea of an invisibility cloak may seem more science fiction than actual science, a group of American researchers are well on their way.
Researchers from Towson University and the University of Maryland used 25,000 individual cloaks 30 micrometres in diameter to slow down light to the point where it is stopped, causing a ‘trapped rainbow’ effect.
Placed on a gold sheet only 25mm per side, these ‘invisibility cloaks’ have the power to stop light, causing it to separate into different colour components.
Microscopic: Scientists used 25,000 individual cloaks 30 micrometres in diameter to slow down light to the point where it is stopped
Powerful: Placed on a gold sheet only 25mm per side, these ¿invisibility cloaks¿ have the power to slow or even stop light
Their findings, published in the New Journal of Physics, are by no means like a Harry Potter invisibility cloak that can make any object underneath vanish.
Nevertheless, researchers found that these tiny invisibility cloaks altered around 20 per cent of any given surface area.
Lead author of the study, Dr Vera Smolyaninova said: ‘In our array, light is stopped at the boundary of each of the cloaks, meaning we observe the trapped rainbow at the edge of each cloak.
‘The benefit of a biochip array is that you have a large number of small sensors, meaning you can perform many tests at once.
‘For example,’ she said, ‘you could test for multiple genetic conditions in a person’s DNA in just one go.’
Earlier this year, researchers cloaked a three-dimensional object standing in free space - bringing the idea of an 'invisibility cloak' a step closer.
The researchers used a hi-tech technique to 'hide' an 18-centimetre cylinder - and made it totally invisible.
So far, the researchers can use a hi-tech coating to make an object disappear - but can only hide it from microwave scanners.
It's still visible to the naked eye.
Findings: researchers found that these tiny invisibility cloaks altered around 20 per cent of any given surface area
The researchers say that the technique could be used to hide objects from visible light - but that it would only work on objects on the millimetre scale, ie ones close to invisible anyway.
Previous studies have either been theoretical in nature or limited to the cloaking of two-dimensional objects, this study shows how ordinary objects can be cloaked in their natural environment in all directions and from all of an observer's positions.
Published today, 26 January, in the Institute of Physics and German Physical Society's New Journal of Physics, the researchers used a method known as "plasmonic cloaking" to hide an 18-centimetre cylindrical tube from microwaves.
Some of the most recent breakthroughs in the field of invisibility cloaking have focussed on using transformation-based metamaterials — inhomogeneous, man-made materials that have the ability to bend light around objects .
This new approach uses a different type of artificial material — plasmonic metamaterials.
The research, at the University of Texas, is the first ever to 'hide' a 3D object - but it's not quite a Harry Potter-style cloak yet
When light strikes an object, it rebounds off its surface towards another direction, just like throwing a tennis ball against a wall. The reason we see objects is because light rays bounce off materials towards our eyes and our eyes are able to process the information.
Due to their unique properties, plasmonic metamaterials have the opposite scattering effect to everyday materials.
'When the scattered fields from the cloak and the object interfere, they cancel each other out and the overall effect is transparency and invisibility at all angles of observation.'
'One of the advantages of the plasmonic cloaking technique is its robustness and moderately broad bandwidth of operation, superior to conventional cloaks based on transformation metamaterials. This made our experiment more robust to possible imperfections, which is particularly important when cloaking a 3D object in free-space,' said study co-author Professor Andrea Alu.
In this instance, the cylindrical tube was cloaked with a shell of plasmonic metamaterial to make it appear invisible.
The system was tested by directing microwaves towards the cloaked cylinder and mapping the resulting scattering both around the object and in the far-field.
The researchers, from the University of Texas at Austin, have shown in previous studies that the shape of the object is irrelevant; oddly shaped and asymmetric objects can both be cloaked using this technique.
Moving forward, one of the key challenges for the researchers will be to demonstrate the cloaking of a 3D object using visible light.
'In principle, this technique could be used to cloak light; in fact, some plasmonic materials are naturally available at optical frequencies.
However, the size of the objects that can be efficiently cloaked with this method scales with the wavelength of operation, so when applied to optical frequencies we may be able to efficiently stop the scattering of micrometre-sized objects.
'Still, cloaking small objects may be exciting for a variety of applications. For instance, we are currently investigating the application of these concepts to cloak a microscope tip at optical frequencies. This may greatly benefit biomedical and optical near-field measurements," continued Professor Alu.
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WARNING FROM RAEL: For those who don't use their intelligence at its full capacity, the label "selected by RAEL" on some articles does not mean that I agree with their content or support it. "Selected by RAEL" means that I believe it is important for the people of this planet to know about what people think or do, even when what they think or do is completely stupid and against our philosophy. When I selected articles in the past about stupid Christian fundamentalists in America praying for rain, I am sure no Rael-Science reader was stupid enough to believe that I was supporting praying to change the weather. So, when I select articles which are in favor of drugs, anti-semitic, anti-Jewish, racist, revisionist, or inciting hatred against any group or religion, or any other stupid article, it does not mean that I support them. It just means that it is important for all human beings to know about them. Common sense, which is usually very good among our readers, is good enough to understand that. When, like in the recent articles on drug decriminalization, it is necessary to make it clearer, I add a comment, which in this case was very clear: I support decriminalizing all drugs, as it is stupid to throw depressed and sad people (as only depressed and sad people use drugs) in prison and ruin their life with a criminal record. That does not mean that there is any change to the Message which says clearly that we must not use any drug except for medical purposes. The same applies to the freedom of expression which must be absolute. That does not mean again of course that I agree with anti-Jews, antisemites, racists of any kind or anti-Raelians. But by knowing your enemies or the enemies of your values, you are better equipped to fight them. With love and respect of course, and with the wonderful sentence of the French philosopher Voltaire in mind: "I disapprove of what you say, but I will defend to the death your right to say it".
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"Ethics" is simply a last-gasp attempt by deist conservatives and
orthodox dogmatics to keep humanity in ignorance and obscurantism,
through the well tried fermentation of fear, the fear of science and
new technologies.
There is nothing glorious about what our ancestors call history,
it is simply a succession of mistakes, intolerances and violations.
On the contrary, let us embrace Science and the new technologies
unfettered, for it is these which will liberate mankind from the
myth of god, and free us from our age old fears, from disease,
death and the sweat of labour.
Rael
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