Optical atomic clocks can help improve the precision of time and location accuracy for GPS systems and mobile phones – but they are too complex to be widely used in society.
A research team from Purdue University, USA, and Chalmers University of Technology, Sweden, has developed a technology that, with the help of on-chip microcomb chips for GPS systems, could make ultra-precise optical atomic clock systems significantly smaller and more accessible.
This will help with navigation, autonomous vehicles, and geo-data monitoring.
How Microcombs Solve Frequency Issues
Microcombs are small chip-based devices that can generate a spectrum of evenly distributed light frequencies.
“This allows one of the comb frequencies to be locked to a laser frequency that is in turn locked to the atomic clock oscillation,” says Minghao Qi, from Purdue University.
The researchers’ microcomb chips were able to solve the problem of frequency issues present in optical atomic clocks – while enabling the atomic clock system to shrink considerably.
Photonic Integration and Miniaturisation
“Fortunately, our microcomb chips for GPS systems can act as a bridge between the optical signals of the atomic clock and the radio frequencies used to count the atomic clock’s oscillations. Moreover, the minimal size of the microcomb makes it possible to shrink the atomic clock system significantly while maintaining its extraordinary precision,” says Victor Torres Company, Professor of Photonics at Chalmers and co-author of the study.
The new system also includes integrated photonics, which uses chip-based components rather than bulky laser optics.
“Photonic integration technology makes it possible to integrate the optical components of optical atomic clocks, such as frequency combs, atomic sources, and lasers, on tiny photonic chips in micrometre to millimetre sizes, significantly reducing the size and weight of the system,” says Dr. Kaiyi Wu.
Future Advancements and Mass Production
The innovation could pave the way for mass production, making optical atomic clocks more affordable and accessible for a range of applications in society and science. The system that is required to “count” the cycle of an optical frequency requires many components besides the microcombs, such as modulators, detectors, and optical amplifiers. This study solves an important problem and shows a new architecture, but the next steps are to bring all the elements necessary to create a full system on a chip.
"We hope that future advances in materials and manufacturing techniques can further streamline the technology, bringing us closer to a world where ultra-precise timekeeping is a standard feature in our mobile phones and computers," says Victor Torres Company.
Finally, the authors wish to pay tribute to the late Professor Andrew Weiner, who oversaw the research project upon which this work is based but passed away before the publication.
“Professor Weiner was a mentor for all of the authors in this publication and his dedication to scientific discovery, his vision for research direction, and his high standards for research results and ethics will be forever remembered,” says Minghao Qi.
