A research team from the National Time Service Center of the Chinese Academy of Sciences has to the development of compact optical clock. This revolutionary device employs quantum interference enhanced absorption spectroscopy to operate. This novel technology will revolutionize μPNT systems. First, it will not only offer better frequency stability but the future frequency stability needed for applications such as 5G.
The atoms in Rubidium are used by taking advantage of their two-photon transition. This somewhat tedious process illustrates its surprising talent for creating extreme frequency stability. The researchers successfully locked the laser beat-note with a fractional frequency stability of 1.8 x 10−12 at one second and below 10−11 at 10,000 seconds. This impressive stability enhancement goes beyond prior records by over two orders of magnitude compared to traditional free-running architectures.
Key Technical Innovations
Even using laser powers as low as 100 µW, the team still got impressive results. They maintained cell temperatures near 40℃ to maximize their productivity. This is a big step forward. Classic techniques need to be operated at elevated cell temperature approaching 100℃ and laser powers of tens of mW, which are incompatible with miniaturized, low-power optical clocks.
In their experiments, the researchers utilized monochromatic light while carefully controlling polarization configurations when utilizing counterpropagating pump and probe beams. They implemented this approach to achieve improved absorption. This impressive effect was due to the constructive or destructive interference of two dark states formed by the two pump and probe beams. This new and advanced way of doing things may one day lead the way for even smaller and more efficient optical clocks.
“Theoretically calculated (left) and experimentally observed (right) spectroscopic signals in proposed method.” – Peter Yun
Collaborative Research Efforts
The project represents a collaboration with Prof. Rodolphe Boudot from the Franche-Comté Électronique Mécanique Thermique et Optique—Sciences et Technologies (FEMTO-ST) Institute in France. Jointly, they proposed a theoretical model showing the essential role played by Zeeman dark states in this new spectroscopic scheme. Their findings are now available in the journal Physical Review Applied. This research provides a real world, long term, performance reference for this new clock design.
“Compact optical clocks implemented with enhanced-absorption of sub-Doppler resonances, experimental setup (left) and measured laser frequency stability (right).” – Peter Yun
The impacts of this research go well past WCU’s campus and outside the confines of scholarly pursuit. As technology matures, the portable, compact optical clock will shake precision to its foundations. It would dramatically advance telecommunications, global positioning systems, and many other disciplines.
Implications for Future Technologies
The development of such a small, portable optical clock would revolutionize the performance expectations for precision timing and navigation applications. In addition to increasing accuracy, enhanced frequency stability allows for more reliable micro-positioning applications.
This new technology solves the previous limitations of power and footprint. It is poised to change the field’s view of how easy it can be to integrate timing devices within today’s complex systems. And scientists are continuing to improve upon these breakthroughs. This project has the potential to make paradigm-shifting advances across multiple industries that rely on highly accurate timing systems.