See the Light

A new discovery links the spin and momentum of light waves, and could mean a major advance in the development of new photonic and spintronic devices.

Scientists from Purdue University have discovered a property of light waves called “spin-momentum locking,” which means that a rotating electric field accompanying light moves in a certain direction according to the photons’ momentum.  In other words, light waves spinning counterclockwise move only “forward,” those spinning clockwise move only “backward.”

It’s a significant discovery, because it means that light—formerly used in technology merely for communication purposes—can now be harnessed for memory and logic operations in computers, for instance, by using photonic spin.

Photonic technology could also be coupled with “spintronics,” in which the spin as well as charge of electrons is utilized. To understand photonics, and how it can be used, check out the video below from Prof. David Lancaster from IPAS at the University of Adelaide.

Unfolding the Research

“The question,” explains Zubin Jacob, one of the authors of the new study appearing in the journal Optica, “is how to interface photonics and spintronics.  We would have to use some of these spin properties of light to interface with spintronics so that we might use both photons and electrons in devices.”

"Researchers had noticed intriguing effects related to directional propagation of light coupled to its polarization," Jacob continues. "What we have shown is that this is a unique effect related to the spin and momentum of light analogous in many ways to the case of spin-momentum locking which occurs for electrons. We showed there is a very simple rule that governs this spin and momentum locking. And it's a universal property for all optical materials and nanostructures, which makes it potentially very useful for photonic devices. This universality is unique to light and does not occur for electrons."

Further research remains to be done, but it’s a promising development for a brand new technology.

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