Search Menu
Photonics Media Photonics Buyers' Guide Photonics EDU Photonics Spectra BioPhotonics EuroPhotonics Industrial Photonics Photonics Showcase Photonics ProdSpec Photonics Handbook
More News
Email Facebook Twitter Google+ LinkedIn Comments

Light Polarization Reveals Chiral Side of Silicon

Photonics Spectra
Sep 2015
PHILADELPHIA, July 24, 2015 — Polarized light can bring out an unexpected electrical property in silicon, potentially unlocking new possibilities for computing.

University of Pennsylvania researchers examining a silicon device caused current to flow in one direction by shining clockwise-polarized light on it; counterclockwise-polarized light caused current to flow in the opposite direction.

Silicon device

A silicon-based photonic device exhibits unexpected topological effects when illuminated with clockwise- and counterclockwise-polarized light. Courtesy of the University of Pennsylvania.

The phenomenon is a function of the geometric relationship between the pattern of atoms on the surface of silicon nanowires and how electrodes placed on those wires intersect them. The interaction between the semiconducting silicon and the metallic electrodes produces an electric field at an angle that breaks the mirror symmetry that silicon typically exhibits, lending it chiral properties.

"Whenever you change a symmetry, you can do new things," said professor Ritesh Agarwal. "In this case, we have demonstrated how to make a photodetector sensitive to a photon's spin. All photonic computers need photodetectors but they currently only use the quantity of photons to encode information. This sensitivity to photon spin would be an extra degree of freedom, meaning you could encode additional information on each photon."

The discovery grew out of work on topological insulators — materials whose surfaces conduct electricity but whose interiors do not. As a light, highly symmetric material, silicon was not thought to be able to exhibit this property.

"We expected the control experiment to give a null result; instead we discovered something new about nanomaterials," said professor Eugene Mele.

Silicon is at the heart of the computer industry, so finding ways to produce these effects in that material is preferable to learning to work with the heavier, rarer elements that naturally exhibit them, the researchers said.

Funding came from the U.S. Army Research Office, Department of Energy and National Science Foundation.

The research was published in Science (doi: 10.1126/science.aac6275).

For more information, visit

Research & TechnologyAmericasPennsylvaniaUniversity of PennsylvaniaPennRitesh AgarwalEugene MelesiliconcomputingmaterialsnanoTech Pulse

Terms & Conditions Privacy Policy About Us Contact Us
back to top
Facebook Twitter Instagram LinkedIn YouTube RSS
©2018 Photonics Media, 100 West St., Pittsfield, MA, 01201 USA,

Photonics Media, Laurin Publishing
x Subscribe to Photonics Spectra magazine - FREE!
We use cookies to improve user experience and analyze our website traffic as stated in our Privacy Policy. By using this website, you agree to the use of cookies unless you have disabled them.