Glass Chip the Size of a Palm Links Two Telescopes in First On-Sky Test
Heriot-Watt's photonic chip replaced bulky mirrors and lenses at the CHARA Array in California, and picked up stars fainter than the system it replaced.
A glass chip small enough to fit in the palm of a hand has linked two telescopes so they act as one powerful instrument, researchers at Heriot-Watt University report. It marks a step toward a new generation of astronomical technology.
The CHARA Array in California is one of the world's leading facilities for high-resolution astronomy and consists of six telescopes that can be linked to study celestial objects in extraordinary detail. To make that work, the light collected by each telescope must be combined with extreme precision. The photonic chip, which guides light through thin glass channels the way integrated circuits guide electrons, has now been used for the first time in on-sky observations at the array.
The result shows the technology can do a job that has traditionally required much larger and more complex optical systems. Professor Robert Thomson of Heriot-Watt's Institute of Photonics and Quantum Sciences said astronomers get much sharper views by combining observations from several telescopes. 'Traditionally, combining the light from multiple telescopes requires bulky instruments with complex arrangements of mirrors and lenses,' he said. 'We have shown that much of that work can instead be carried out by a glass chip only a couple of centimeters in size.'
The channels are written directly inside a specially chosen glass using ultrafast-laser inscription, giving access to an unexplored spectral range for this fabrication process. The chip sits at the heart of an instrument called CHARIOT, designed as a testbed for new photonic technologies. During observing campaigns in 2024 and 2025, CHARIOT combined light from telescopes at the CHARA Array and recorded signals from a range of stars. It also detected stars fainter than those reached by the system it replaced.
The flexibility is part of the appeal. Different photonic chips can be swapped in within hours, so researchers can test improved designs quickly. Dr. Aurélien Benoît, who helped develop the chip, said, 'There is something very special about seeing a device that we conceived, designed, fabricated and characterized in the laboratory being used to efficiently collect and analyze light from real stars at one of the world's leading astronomical interferometers.'
The project brought together researchers from the U.K. (Heriot-Watt University), Germany (the universities of Cologne and Potsdam) and the United States (the CHARA Array of Georgia State University). Lead author Dr. Aline Dinkelaker, of the Leibniz Institute for Astrophysics Potsdam, said, 'Demonstrating this technology under real observing conditions is an important step forward.'
The work is published in Monthly Notices of the Royal Astronomical Society (DOI 10.1093/mnras/stag1745) and belongs to the growing field of astrophotonics. Thomson called it a milestone for a research program that began more than 15 years ago.
The researchers say the approach could eventually make astronomical instruments smaller, more robust and easier to upgrade, while supporting goals such as studying how planetary systems form and evolve and directly detecting and characterizing planets around other stars.
