Cloaking technology : A step towards invisibility

Researches are going on since yore to make things invisible. There have a number of movies including StarTrek and others which shows the cloaking technology to make things invisible.

The basic requirements for being invisible are :

• It has to be able to bend light around itself, so that it casts no shadow.
• It must produce no reflection.

Bending waves using cloaking technology

Bending light around an object requires a material to have a negative refractive index. The refractive index is a property that dictates how light passes through a medium; it's the reason a stick will look bent when placed in water. If water had a negative refractive index, it would make the stick look as though it were bending back on itself. Designs have been developed and demonstrated both theoretically and practically made up of very thin conducting wires that could have an effect on the electric and magnetic fields of microwaves, causing them to bend in unnatural ways. Such materials are called metamaterials. Theoretically it has been proved that cloaking effect can bend lights for these metamaterials in such a matter that they become invisible to human eye.

Cloaking technology works majorly on plasmons - tiny electronic excitations on the surfaces of some metals to cancel out the visible light or other radiation coming from an object.

Though the idea was to hide the object completely but there are a few limitations to the technology which prevent it from attain complete invisibility. Cloaking ability widely depends on an object's size, so that only with very small thing, the visible light can be rendered in such a manner to make it impossible to detect. Larger objects like the one we use in  real life can also be made invisible using this technology but for the waves of larger wavelengths such as microwaves but not for the visible light. Similarly gigantic objects such as a spaceship can be made invisible for radiowaves or some other long wavelength detectors.

As we have seen, there are limitation to the current cloaking technology for making things invisible but the step is another milestones towards achieving the goal. Scientists are working are researches are going on to attain the complete invisibility.