Southampton researchers help bring optical fibre performance onto a chip

Researchers from the University of Southampton have contributed to a major advance in integrated photonics, working with scientists at the California Institute of Technology to bring the exceptional performance of optical fibre closer to compact chip scale devices. 

The work, published in Nature, demonstrates a new way of guiding light through tiny glass pathways made on silicon wafers. These pathways are formed from germanosilicate glass, a material closely related to that used in optical fibre. The result is a compact optical platform that can carry light with extremely low loss, including at visible wavelengths where this has historically been very difficult. 

Optical fibre underpins the modern internet because it can transmit light over long distances with remarkably little signal loss. Translating that performance into much smaller devices has been a major goal in photonics, with potential benefits for precision measurement, quantum technologies, optical clocks, advanced sensing, navigation systems and future communications. 

The new approach uses advanced wafer scale fabrication to create smooth glass waveguides that guide light around compact structures. A key part of the breakthrough is a thermal smoothing process, which reduces microscopic roughness on the waveguide surfaces. This is important because even tiny imperfections can scatter light and reduce performance, especially at shorter wavelengths such as blue and violet light. 

The platform achieved exceptionally low optical losses across a broad range of wavelengths, from violet to near infrared. The Nature paper reports resonator quality factors exceeding 180 million across this range, with the potential to bring fibre like optical loss into compact integrated devices. 

Professor Christopher Holmes, co-author of the study, said: ‘This work is exciting because it takes one of the great strengths of optical fibre, its exceptionally low loss, and brings it into a compact, manufacturable platform. It is a powerful reminder that glass remains one of the most important materials in photonics.’ 

Professor James Gates said: ‘We’re delighted with the outcomes of this collaboration, which builds on long-standing discussions between Southampton and Caltech around a shared ambition of achieving the lowest-loss chip-based photonics in the world. The exceptional performance of the resulting devices underscores just how crucial reducing optical loss is for next-generation applications. Importantly, this work opens the door to integrated photonics at shorter visible wavelengths, particularly in the blue, where loss has historically been a major obstacle. I’m especially pleased to see glass, a material that has shaped the entire field of optics yet has been somewhat overlooked in recent decades, re-established as a leading platform for integrated photonics.’ 

The research highlights the renewed importance of glass in advanced photonics. By combining the optical quality of fibre materials with the scalability of wafer-based manufacturing, the platform could support a new generation of smaller, more robust and more precise optical systems.  

Read the full paper: Towards fibre-like loss for photonic integration from violet to near-infrared.