Light and sound strongly coupled in an optical fibre: a first for Erlangen researchers
Until now this required resonators in which light circulates many times. Researchers at the Max Planck Institute in Erlangen now show strong coupling in a fibre that light passes through only once.
Archive image · Photo: MPL Presse / Wikimedia Commons, CC BY 4.0 (cropped and resized)
Researchers at the Max Planck Institute for the Science of Light (MPL) in Erlangen and Leibniz University Hannover have for the first time strongly coupled light and long-lived sound vibrations in an optical fibre. Until now this was only possible with optical or mechanical resonators, in which light laps around many times like on a racetrack. In a fibre, by contrast, it passes through only once – like on a highway. The work by Laura Blázquez Martínez, Changlong Zhu and Birgit Stiller appeared in Nature Physics (DOI 10.1038/s41567-026-03458-2).
The team used stimulated Brillouin scattering in a fibre cooled to 4 kelvin, around minus 269 degrees Celsius. With a new measurement technique it observed a gap in the spectrum – a hallmark of strong coupling previously known only from resonators.
The group sees the result as a proof of concept for quantum interactions in optical fibres, the backbone of telecommunications. In the long run this could help link quantum computers and process quantum signals. "This result is a crucial step toward utilizing optical fibers as a powerful platform for quantum interactions," group leader Birgit Stiller said in the release.