Making objects invisible is no longer the stuff of fantasy but a fast-evolving science. ‘Invisibility cloaks’ using metamaterials now exist, and are beginning to be used to improve the performance of satellite antennas and sensors. Many of the proposed metamaterials, however, only work at limited wavelength ranges such as microwave frequencies.
Now, scientists report a way of making a cylinder invisible without a cloak for monochromatic illumination at optical frequency.
Scientists determined that invisibility would occur when the refractive index of the cylinder ranges from 2.7 to 3.8. Some useful natural materials fall within this range, such as silicon (Si), aluminum arsenide (AlAs) and germanium arsenide (GaAs), which are commonly used in semiconductor technology. By taking a close look at the magnetic field profiles, they inferred that “the invisibility stems from the cancellation of the dipoles generated in the cylinder.”
Although rigorous calculations of the scattering efficiency have so far only been possible for cylinders and spheres, Kajikawa notes there are plans to test other structures, but these would require much more computing power. (1)
A world full of things we see.
A world full of invisible things.
Right next to you, a table.
It is clearly there. Is it?
Deep inside yourself, you.
You do clearly exist, don’t you?
Extend your hand.
When I touch this table,
it feels like it is touching me…