Rice-Grain Chip Creates a Stable 'Rainbow' of Light to Power Future 6G

Physicists at Loughborough University, working with an international research team, have built a microchip about the size of a grain of rice that produces a highly organized "rainbow" of light — a set of precisely spaced light frequencies. The work, published in the peer-reviewed journal Nature Communications, could eventually support faster, higher-capacity 6G communications and precise timing for quantum technologies.

The chip is a microcomb, a device generating precise light frequencies arranged somewhat like the colors of a rainbow, though invisible to the human eye. A specialized antenna converts these frequencies into millimeter waves, high-frequency signals offering far more bandwidth than current networks. Earlier microcombs produced only a single millimeter-wave frequency; generating several at once, each serving as a separate data channel, needed exceptional stability.

Conventional microcombs work by shining laser light into a microresonator, a tiny chip structure that traps and circulates light. The Loughborough team instead connected the chip-based microresonator to a much larger loop of optical fiber, with light continuously travelling through both parts to help the optical states form and stay stable. "We've essentially created an incredibly precise and stable 'rainbow on a chip', where the loop keeps feeding the light back through the chip, allowing these states to build up efficiently, start on their own and remain stable even when the system is disturbed," said Dr. Luke Peters of Loughborough University's Emergent Photonics Research Centre. He added that the microcomb stayed stable when people jumped beside it.

The researchers also showed they could strengthen or weaken individual frequencies in the microcomb, and that its precision survived conversion into millimeter waves. The setup currently fills a tabletop laboratory, though future versions could shrink to fit inside a shoebox, including for possible satellite use. The team is now comparing the microcomb's timing accuracy with precision clocks, working with the National Physical Laboratory and the UK Hub for Quantum Enabled Position, Navigation and Timing (QEPNT).