From Star Trek to Harry Potter, invisibility cloaks are a popular theme in science fiction.
And now researchers have developed a new technique that could turn the futuristic technology into a reality.
The technique involves disrupting the way that light waves pass through opaque objects, and could lead to active camouflage.
While researchers are yet to demonstrate it in practice, they are confident that experiments will soon confirm the idea.
Researchers from the Technical University in Vienna are behind the new idea for a cloaking technology.
Professor Stefan Rotter, one of the researchers working on the technology, said: ‘Complex materials such as a sugar cube are opaque, because light waves inside them are scattered multiple times.
‘A light wave can enter and exit the object, but will never pass through the medium on a straight line.
‘Instead, it is scattered into all possible directions.’
The researchers’ technique is attempting to outwit this kind of light scattering.
Dr Andre Brandstötter, one of the authors of the study, said: ‘We did not want to reroute the light waves, nor did we want to restore them with additional displays.
‘Our goal was to guide the original light wave through the object, as if the object was not there at all.
‘This sounds strange, but with certain materials and using our special wave technology, it is indeed possible.’
The concept involves shining a laser onto a material from above to pump it full of energy.
This can alter the material’s properties, making it transparent to other wavelengths of light coming in from the side.
Professor Konstantinos Makris, who is also working on the study, explained: ‘The crucial point is to pump energy into the material in a spatially tailored way such that light is amplified in exactly the right places, while allowing for absorption at other parts of the material.
‘To achieve this, a beam with exactly the right pattern has to be projected onto the material from above – like from a standard video projector, except with much higher resolution.’
But in order to render an object invisible, the pattern that is projected onto it must correspond perfectly to the inner irregularities of that item that usually scatters light.
Professor Rotter said: ‘Mathematically, it is not immediately obvious that it is at all possible to find such a pattern.
‘Every object we want to make transparent has to be irradiated with its own specific pattern – depending on the microscopic details of the scattering process inside.
‘The method we developed now allows us to calculate the right pattern for any arbitrary scattering medium.’
So far, computer simulations have suggested the method works, although it is yet to be shown in practice.
Professor Rotter added: ‘We are already discussing with experimentalists how this could be done.
‘As a first step, we may test this technology with sound instead of light waves.
‘Experimentally, they are easier to handle, and from a mathematical point of view, the difference does not matter significantly.’