During April 2151, humanity encountered the first cloaking incident when Suliban used their cloaking device to approach Startship Enterprise and managed to inflict a close fight. Yes, you heard it right, we are talking about Star Trek stories. Suliban’s cloaking device was a particle generator which absorbs all the light making it invisible. In the scenario of dark space it may be possible but when it comes to its application on earth there is a major practical difficulty. The cloaking material may absorb the light but in turn, it will create a black patch and will obstruct the background. That serves no purpose because the object can be identified by its dark patch.

The major idea of invisibility came into forth when the idea of light bending the across the object came into picture. The whole idea was to pass the light across the periphery of the object and then clubbing the light together. This helps in seeing the background behind the object thus making the object completely invisible.

Scientists has successfully tried this with a diamond-shaped cloak allowing the edges to match up. By this process, they were successful in bending light around their 1 centimeter high, 7.5 centimeter wide cylinder without reflections. When it comes to replicating such things with bigger objects it becomes almost achievable, let alone making a complete starship invisible.

In the picture above, the object wearing the cloak appears invisible because the background visual is being displayed onto the retro-reflective material. At the same time, all other light rays are allowed to reach the user’s eye, making the person in the front completely invisible. [image : Howstuffworks]

Bending of light across the periphery of the object sounds simple but difficult to achieve. Scientists have come out with various meta-material structure with intricate slits and cuts across the periphery of the object to channelize the light streams in proper direction and then clubbing the same behind the object. Manufacturing such accurate and intricate meta-material structure is always costly and challenging and sometimes almost impossible. On top of that, It is easier to hide objects from other waves like heat, magnetic fields or acoustics. Scientists are not that successful replicating these incidents with Light waves having longer wavelengths

Advent of 3D printer solves this problem and you can print such intricate structure accurately. You will not be surprised if you hear scientists are cloaking bigger materials with the 3D printed meta-materials.

Recently Scientists are successful in creating a cloak in entirely different way. This is done by creating a time hole/ time gap in the light stream. It is more like fast forwarding the front of the wavelength and pulling back the trail of the wavelength. This is even effective in cloaking a total incident. it can be explained like this:

The rays emanating from the slits combine on the other side to create an intricate interference pattern of peaks and troughs. Talbot discovered that this pattern repeats at regular intervals, creating what is now known as a Talbot carpet. There is also a temporal version of this effect in which you manipulate light over time to generate regular periods with zero light intensity, says Lukens. Data can be then be hidden in these holes in time. [Nature]

In simplistic term if you imagine the bus-scene in the movieSpeedin which the good guys use a short loop of camera footage of all the passengers sitting still to fool the bad guy into thinking that everything is going his way. During that time, the hero was helping everyone to escape. The invisibility cloak with time gap will be able to do that when it will be available in scaled up version.

• Coming to the usage of cloaking technology, it will have various utilities in the form of:
• Cloaking various vehicles during war or to hide the supply chain in hostile location
• Commando team can observe the hostage and the extremists beyond the wall in front and drive the operation accordingly
• In medical field, it will be extremely useful for surgeons to see the actual part of the body/ tissue beyond the tools and/or equipment that comes in front
• The time gap cloak will be extremely useful to hide events in future. In near future, we will see its practical application in secure data transmission by hiding the data partially or completely in time gap.

Possibilities are endless and endless are the practical challenges. But in all probability we have to wait a while before we see a flawless and practical demonstration of invisibility cloak.

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Author: Technology and Beyond