Tiny photonic chip links telescopes together to view the universe in ‘astonishing’ details

A tiny glass chip developed by researchers at Heriot-Watt University has linked two telescopes together to enable them to act as a single powerful instrument, marking an important step towards a new generation of astronomical technology.

The CHARA Array is one of the world's leading facilities for high-resolution astronomy and consists of six telescopes that can be linked together to study celestial objects in extraordinary detail. To make this possible, the light collected by each telescope must be combined with extreme precision. The photonic chip – which guided light through thin glass channels in the manner of integrated circuits guiding electrons – has been successfully used for the first time in on-sky observations at the CHARA Array in California. The results show that the technology, small enough to fit in the palm of a hand, can perform a task that has traditionally required much larger and more complex optical systems.

The achievement could help transform the way future astronomical instruments are designed, making them smaller, more robust and easier to upgrade while still delivering the precision needed to study distant stars and planetary systems.

The study appears in Monthly Notices of the Royal Astronomical Society (MNRAS), one of the most respected journals in astronomy.

Researchers believe the technology could eventually support some of astronomy's most ambitious goals, including studying how planetary systems form and evolve while helping scientists directly detect and characterise planets around other stars.

The international project brought together researchers from the UK (Heriot-Watt University), Germany (Cologne and Potsdam Universities) and the United States (The CHARA array of Georgia State University). The photonic chip at the heart of the instrument was developed at Heriot-Watt University's Institute of Photonics and Quantum Sciences by Professor Robert Thomson and Dr Aurélien Benoît. The team also played a central role in the observing campaigns that demonstrated the technology on the telescope array.

Professor Robert Thomson from Heriot-Watt University’s School of Engineering & Physical Sciences said: “This is a significant milestone for a research programme that began more than 15 years ago. Astronomers can achieve much sharper views of the universe by combining observations from several telescopes at the same time. Doing this allows the telescopes to work together as though they were one much larger telescope.

“Traditionally, combining the light from multiple telescopes requires bulky instruments with complex arrangements of mirrors and lenses. We have shown that much of that work can instead be carried out by a glass chip only a couple of centimetres in size.

“Seeing this technology progress from fundamental research and early laboratory demonstrations to successful operation at one of the world’s leading facilities is a particularly significant outcome and a demonstration of the power of international collaboration.”

The Heriot-Watt photonic chip performs that role. Tiny channels are written directly using an ultrafast-laser inscription technique inside an innovative glass to provide access to an unexplored spectral range for this fabrication process. The channels combine the incoming light enabling the separate telescopes to work together as a single telescope.

The chip sits at the heart of an instrument called CHARIOT, which was designed as a testbed for new photonic technologies. During observing campaigns in 2024 and 2025, CHARIOT successfully combined light from telescopes at the CHARA Array and recorded signals from a range of stars, demonstrating the precision required for advanced astronomical research. The instrument also detected signals from stars fainter than those reached by the system it replaced.

Dr Aurélien Benoît, from Heriot-Watt University’s Institute of Photonics and Quantum Sciences, said: “There is something very special about seeing a device that we conceived, designed, fabricated and characterised in the laboratory being used to efficiently collect and analyse light from real stars at one of the world’s leading astronomical interferometers.

“The great advantage of our approach is that we can integrate complex optical functions into a remarkably small and stable glass chip. Combined with the flexibility of CHARIOT, this gives us a powerful platform for rapidly testing and validating increasingly advanced photonic technologies as we develop them.”

Dr Aline Dinkelaker, lead author of the study from the Leibniz Institute for Astrophysics Potsdam, said: “Demonstrating this technology under real observing conditions is an important step forward. These first observations show that photonic technologies can deliver the performance needed for frontline astronomical research.

“As the technology develops, it could help astronomers study planetary systems around other stars in greater detail and support some of the most ambitious goals in modern astronomy.”

One of CHARIOT’s biggest advantages is flexibility. Different photonic technology chips can be removed and replaced within hours, allowing researchers to test improved designs quickly and efficiently.

The work is part of the growing field of astrophotonics, which uses advanced light-based technologies to tackle some of astronomy's most challenging problems.