Physics > Waves > Metamaterials and the invisibility cloke

Invisibility has always been a dream technology and considered impossible by most physicists. But metamaterials are now offering a lot of hope...

War has been a constant part of human history and science and technology always played a decisive role in war. That is perhaps the main reason why science has been shaping human history. As an example we can consider the discovery of the processes to produce metals like copper , iron and steel which provided weapons and armour which were decisive in early wars, no t o mention bigger war machines. The discovery of gunpowder is another important example. More recently the invention of radar made a lot of difference in the world wars. In the future the invisibility cloke could be decisive in war.

Invisibility has been a subject of science fiction and fantasy for a long time. We can mention the Klingon starships, in Star Trek, Harry Potter´s cloke or the powerful ring in the Lord of the rings. There are also great books about the invisible man, like the one by H.G. Wells.

Invisibility is impossible today, yes, but apparently not for very long. Metamaterials offer a lot of hope in this direction.

negative refractive indexes

Physics textbooks mention only positive refractive indexes. Negative ones were considered impossible, but now they are a reality. Meta materials can have negative indexes of refraction and as a result they offer novel ways to manipulate light. The hope is that a metamaterial can be projected in such a way that light moves around it without being reflected , refracted or anything. That would be analogous to water moving around a stone in a river: it will follow afterwards its path as if the stone was not in there. That is the way invisibility will work one day. This effect has already been achieved for microwaves. For light the challenge is much bigger because its wavelength is much smaller so that the components must be very tiny. This is the technological challenge at the moment.

This process to achieve invisibility is very different from what has been used to make airplanes invisible to radar (but not invisible to be seen). Stealth technology involves absorbing and deflecting the microwaves of radar systems by a set of tricks involving the materials and the shapes of the airplane.

Beyond invisibility...

Although invisibility attracts a lot of attention, metamaterials can potentially bring many more benefits, like better lenses (with much higher resolutions). By increasing our power to manipulate light, the possibilities are huge. The wikipedia article in metamaterials discusses lots of them.

References:

Chang, Kenneth (June 12, 2007). "Light Fantastic: Flirting With Invisibility". New York Times. Retrieved 2010-05-21.

Michio Kaku, Physics of the impossible

https://www.wikiwand.com/en/Metamaterial_cloaking#/The_properties_of_optics_and_light