Invisibility has long occupied a special place in the fantastical imaginings of humankind. Our deep desire to become completely invisible at some point of time in our lives has manifested itself in various books and movies. But as those wishes have appeared more and more unrealistic, we seemed to have almost made a pact with the fact that becoming completely invisible like Harry Potter is a dream not meant for muggles.
But fear not, because scientists have not given up, and thanks to their unflinching desire to achieve a level of full invisibility, they are remarkably close to finding a way to do it. According to News18, a study published in the light journal Optica by a team of researchers claims to have found a way to make 3D objects completely invisible -- even in the presence of natural light.
The biggest stumbling block in rendering an object invisible is the failure of existing cloaking techniques to work in natural light. The existing cloaking techniques use structures called metamaterials, which basically bend the light around an object. But while it works when an object is subjected to light with a single frequency, objects subjected to natural light or broadband illumination appear distorted -- giving up on not only the object, but such a cloak itself.But now the special cloaking technique invented by this team of researchers, called "spectral cloaking," manipulates the frequency of light to make a 3D object fully invisible. This cloak transfers energy from certain colors of the spectrum to others. So, for example, if an object was blue in color, the cloak would turn any wavelength of blue light into green light, thus masking its presence completely invisible.
As explained by professor Jose Azana, one of the researchers in the team, the development marks a major breakthrough in the quest for complete invisibility.
"We have made a target object fully invisible to observation under realistic broadband illumination by propagating the illumination wave through the object with no detectable distortion, exactly as if the object and cloak were not present."Luis Romero Cortés, another member of the team, said that the new spectral technique would allow light to go through an object but still avoid it so as not to distort its appearance.
"Conventional cloaking solutions rely on altering the propagation path of the illumination around the object to be concealed; this way, different colours take different amounts of time to traverse the cloak, resulting in easily detectable distortion that gives away the presence of the cloak.The breakthrough is still in its nascent stages and has only been tested in laboratory conditions, but if the spectral cloaking technique proves a success, invisibility could soon be a reality. Scientists believe that apart from concealing actual objects and even people, this invention could also be massively useful for telecommunications, defense, and information processing technologies.
"Our proposed solution avoids this problem by allowing the wave to propagate through the target object, rather than around it, while still avoiding any interaction between the wave and the object."