Invisibility cloak is about to come true

The witch's invisibility cloak in the Harry Potter series may appear in the future, thanks to two new materials capable of bending the path of light made by American scientists.

In optics, "meta material" is the term for artificial materials designed to have negative refractive index, which means that it can refract visible light. This property is obtained through the structure of the material and not its composition. Therefore, a negative refractive material can cause an object to become invisible by bending light waves so that they 'circle' around the object and then converge in the back, just like a water flow around a rock.

'Stealth is the topic that people care about, but our research results are not merely focused on that ability. We explore the ability to create features that never existed in nature. With these characteristics we can do many things and stealth is just one of them, 'said Xiang Zhang, a professor at the University of California (USA).

Negative refractive materials can also increase the ability of microchips, antennas and allow the creation of 'super lenses' to observe objects smaller than the wavelength of light.

The image enlarges the mesh structure of the material manufactured by the University of California expert team.It is made up of an alternating arrangement of nano-sized silver fibers with magnesium fluoride layers.Photo: National Geographic.

A new material - called Negative Refraction One - is made up of a combination of silver wires about 20 times smaller than a human hair and aluminum oxide (Al ₂ O ₃ ). To create the second material, the team placed silver strands of nanoscale diameter interspersed with magnesium fluoride layers (MgF ₂ ). They then acted so that it had a grid-like structure.

Experimental results show that both new materials bend the path of light within the visible wavelength range. Many scientists have created invisibility effects, but they only do so in two-dimensional space with light waves that cannot be seen by the human eye.

In addition to producing three-dimensional negative refractive indices for larger wavelengths of light (including visible waves), the discovery of Xiang Zhang and colleagues helps the scientific community to overcome energy loss of light.

Materials with a previous negative refractive index absorb most of the light wave and do not bend them. Two new materials are designed so that light does not lose energy even when they meet materials with the highest absorption of light waves.

David Schurig, a material specialist with negative index of University of North Carolina (USA), commented that the two products of Xiang Zhang group are 'the most interesting negative refractive index materials'. 'In the current state, these two materials can be used in video recording or light communication technology,' he said.

However, David stressed that University of California scientists have a long way to conquer before being able to stealth objects larger than nanoscale.