The field of cloaking or hiding or shielding an object from visible light has so far been the stuff of science fiction with everything from "Star Trek" to "Harry Potter" having their own versions of a cloaking device, obscuring the wearer from potential view and harm. Of course, the possible real-world applications of such a device can be both commercial as well as militaristic and researchers from across the world are busy working away at trying to develop a viable prototype.
And according to a recent study, the latest breakthrough by researchers has managed to cloak a rainbow. Of course, the rainbow in question is not a life-sized one but one that was created in a laboratory by scattering white light after passing it through a prism, but the researchers were able to effectively "trap" this rainbow, bringing the light in it to a near complete stop, using more than 25,000 invisibility cloaks. Researchers from Towson University in Maryland were for the first time able to cloak all the colors of the visible spectrum. Previous invisibility cloaks only had limited effect on the range of colors and angels of light, while the Towson University cloak is the first to cover all the colors of the visible spectrum.
The team, taking their cue from a study published in the journal, Physical Review B, used a micro-lens array, an array that uses lenses are only 50 millionths of a metre across. The array itself was coated with a thin film of gold and then placed above gold-sheeted plate of glass. Light was then allowed to enter from the side, between the micro-lens array and the gold-sheeted glass, and it was here, when the light passed between the lenses, that a "cloaked" area was created and the colored light was made invisible.
This “trapped rainbow” effect was first predicted in an article published in 2007 in the journal Nature by Ortwin Hess and colleagues.
Vera Smolyaninova, a researcher who worked on the project, said that the technique developed had applications in "biomedicine and sensing, as well as traditional camouflage," with the press release adding, “The trapped rainbow could be utilised in tiny biosensors to identify biological materials based on the amount of light they absorb and then subsequently emit, which is known as fluorescence spectroscopy. Slowed-down light has a stronger interaction with molecules than light travelling at normal speeds, so it enables a more detailed analysis.”
Dr. Smolyaninova added, “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, you could test for multiple genetic conditions in a person’s DNA in just one go.”