Tokyo University of Science Researchers Achieve Nanoscale Optical Spin Control Using Off-Center Electron Beam Excitation

Researchers at Tokyo University of Science use electron beams and gold nanorods to create spinning light, paving the way for advanced quantum communication.

By: AXL Media

Published: Apr 13, 2026, 8:09 AM EDT

Source: Information for this report was sourced from EurekAlert!

Breakthrough in Nanoscale Light Manipulation

Researchers at the Tokyo University of Science, in collaboration with the Institute for Molecular Science, have developed a novel technique to control the polarization of light at the nanoscale. While light typically moves in straight lines with fixed electric field oscillations, "spinning" or circularly polarized light is highly sought after for its ability to encode and transmit complex data. Producing this spin in confined volumes smaller than a human hair has historically been difficult because the physical geometry of nanostructures tends to force light into linear patterns. However, the team demonstrated that by precisely targeting a gold nanorod with an electron beam, they could overcome these structural limitations to create rotating light fields.

The Physics of Off-Center Excitation

The core of the discovery lies in the asymmetrical application of energy to a 150-nanometer-long gold nanorod. Professor Mark Sadgrove explained the phenomenon using the analogy of flicking the end of a pen on a table, which causes it to rotate as it moves forward. In the study, when the electron beam strikes the nanorod away from its center, it introduces a physical imbalance that forces the resulting light field to take on a rotating character. The researchers found that the farther the beam struck from the center of the rod, the more pronounced the optical spin became. This allows for circular polarization even in elongated materials that traditionally only produce linear polarization.

Innovative Detection via Ultra-Thin Optical Fibers

Verifying the presence of optical spin required a creative experimental setup, as standard sensors often only measure the brightness of light rather than its rotation. To solve this, the researchers coupled the gold nanorod to an ultra-thin optical fiber. This specific type of fiber possesses a unique property where the direction of light travel is determined by whether the light near the rod is spinning clockwise or counterclockwise. According to Sadgrove, his team’s familiarity with the directional properties of optical fibers was the key to confirming that the light was indeed rotating. By monitoring which end of the fiber the light emerged from, the team successfully detected the switch in rotation.