One Direction Visible Light-Passing Metamaterial Developed by NIST
3 July 2014
Scientists from the US National Institute of Standards and Technology (NIST) have developed a photonic diode that allows one-direction passing of visible light through a special metamaterial, the NIST said on its website.
The device uses a block of hyperbolic metamaterial, consisting of 20 alternating layers of silicon dioxide glass and silver that are tens of nanometers thick. The outside of the block is coated with chromium grates that have openings smaller than the wavelength of visible light, which is between 400 nanometers and 700 nanometers.
Because the structure is opaque to visible light from the outside, the behavior of light that enters it depends on the direction from which it approaches it. One side of the block is designed to stop red and green light by bending it, while the grate on the other side lets light out of the structure.
While similar devices have been demonstrated before, they allowed one-way passage only of microwave and infrared wavelengths of light - both of which are invisible. The NIST method is the first one that allows the same to be done with the much shorter wavelengths of visible light.
The breakthrough is significant, because it opens the door for photonics to eventually displace or supplement electronics in microprocessors. That would require photons to be manipulated in the same way that is currently possible with electrons - and photonic diodes that pass light in one direction do just that, not unlike diodes that do the same with electrons.
The NIST-developed metamaterial might also be applied in biosensing, where it would detect small amounts of light from a sample.