Invisibility Cloak with Photonic Crystals

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Invisibility Cloak with Photonic Crystals
Photonic crystals open up possibilities for using more practical materials for invisibility cloaking.

Generally, metamaterials originally propose to develop invisibility cloak. But they did not solve some essential cloaking issues. Previously, you came to know about an invisibility cloak that makes 3D objects disappear. Till then, invisibility cloak was only featured in Hollywood movies like ‘Harry Potter’. Recently,  Elena Semouchkina, an associate professor of electrical and computer engineering with her students have developed some new approach to making cloak more practical. The team used photonic crystals to develop this novel approach.

Objects are apparent to us because a small cut of light that strike them is spread in the direction of our retinas. Making objects invisible is no magic trick.

Making objects invisible comes down to switching electromagnetic waves. The cloak medium requires bending the wave’s path around an area. It hides an object and accelerates waves along the bent trajectories. There are equations that can guess which structural material’s diffusion properties will cover electromagnetic waves. Its depend on the transformation optics principle.

Scientists then used metamaterials composed from dielectric resonators to provide arbitrary dispersions. Dielectric resonators make electromagnetic waves bounce back and forth. It is similar to a tuning fork that mimics like a sound resonator. Thus, this allows controlling wave propagation in the cloak medium.

With the help of properly structured crystals composed of dielectric rods, scientists now developing cloak medium from photonic crystals. The resonance in this crystal atoms does not specify wave transmission.

Photonic crystals in this cloak provide superluminal phase velocity of propagating waves. Thus, waves move faster as compared to light speed. Such kind of speed creates invisibility illusion.

Therefore, this type of velocity preserves the original wave front during waves curve past the cloaked object. These photic crystals also acquire the required anisotropy of their refractive indices. Thus, wave phase velocities are different between the various crystal faces.

According to scientists, it would become useful for both national security and industry.

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