New Metamaterial Transmits Light With No Energy Loss
by Alfredo Carpineti
Photo credit: New zero-index material made of silicon pillar arrays embedded in a polymer matrix and clad in gold film creates a constant phase of light, which stretches out in infinitely long wavelengths, by Peter Allen/Harvard SEAS
Very soon we might be able to say good riddance to the overheating laptops, phones and tablets that we deal with every day. Electrons carry information around circuits but lose energy as heat during transmission. Electrons are the best thing we have right now for computing, but in the near future we could wave goodbye to electronics and welcome photon, or light, communication that will be both faster and cooler. There are still few hurdles before we can get this technology in every home and every pocket, but one of its limitations was just solved by the development of a new metamaterial.
A metamaterial is a substance that has properties not observed in nature. In this case, the special property is its refractive index, a value that describes how light propagates through a medium. Take water or glass, for example, which cause light rays to bend as they travel through them. This is why pools always look shallower than they actually are.
The new metamaterial has a refractive index of zero, which means that the light phase in the material can travel infinitely fast. This doesn’t mean that relativity is violated by this material, though. Light has a “group velocity,” the velocity at which the wave propagates into space, and a “phase velocity,” the velocity at which the peaks of the waves move with respect to the wave.
Special relativity puts limits on the group velocity, as it’s the one that carries information. Nothing can go faster than the group velocity of light in vacuum. Phase velocity affects the shape of the wave; a higher refractive index will squish all the peaks closer together.
The new material eliminates the phase advancement completely – the peaks and the valleys of the wave don’t move through space anymore, they only oscillate in time. This perfectly uniform phase allows the light to be twisted, turned, stretched and squeezed without energy loss.
Applied on chips, this material allows for the emission of photons that are always in phase with one another.
“Integrated photonic circuits are hampered by weak and inefficient optical energy confinement in standard silicon waveguides,” said Yang Li, a postdoctoral fellow and first author on the paper, in a statement. “This zero-index metamaterial offers a solution for the confinement of electromagnetic energy in different waveguide configurations because its high internal phase velocity produces full transmission, regardless of how the material is configured.”
The new material was developed at Harvard’s School of Engineering and Applied Sciences, and details are published in Nature Photonics.