Fabbing a chip that could encode data in a twisted vortex of light

Ars Technica » Scientific Method 2012-10-23

Scanning electron microscope image of a silicon device that twists photons into helical shapes. The light is sent into the 8-micron-diameter ring shown, which produces a twisted wave shape that is emitted perpendicular to the ring.
Michael J. Strain

Photons, in the form of optical pulses, radio waves, and the like, have been used to transmit data for decades. The next phase will probably involve using the quantum states of the photons themselves to carry information.

In terms of these quantum states, photons possess two distinct polarization orientations, along with a theoretically infinite number of helical wave forms, in which the photons rotate around the direction they're moving. The latter have garnered a lot of interest, as they could potentially carry a lot more data than other optical methods. Possible applications include quantum computing, improved fiber optic communication, point-to-point data transfer across free space, and microscopy.

Researchers have now developed a way to produce twisted light beams using silicon chips, the starting point for compact, efficient optical communication. Xinlun Cai and colleagues shaped photons using a microscopic, ring-shaped grating, which sent twisted light out in a specified pattern. Each ring was small enough to be fabricated into integrated circuits, and capable of emitting multiple vortexes of light simultaneously. The same type of chip could also serve as a receiver for twisted light, and manipulate waves that transit through it.

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