China has reported a significant advance in continuous-wave vacuum ultraviolet (CW VUV) laser technology, overcoming what scientists have described as the final technical barrier in building a nuclear clock.

The team, led by Ding Shiqian, an associate professor at Tsinghua University and a researcher at the Beijing Academy of Quantum Information Sciences, developed a 148.4 nm CW laser.

The research published in Nature on Wednesday.

The advance extends ultra-stable laser technology into the vacuum ultraviolet band for the first time. Using four-wave mixing (FWM) in cadmium vapor, the team produced a CW VUV laser at 148.4 nm with an ultranarrow-linewidth well below 100 Hz and output power sufficient to support coherent nuclear interactions.

While atomic clocks are highly precise, they are vulnerable to electromagnetic interference and are mainly confined to laboratory use, researchers said.

Nuclear clocks are expected to offer higher precision and stronger resistance to interference, but progress has long been constrained by the lack of a 148-nanometer CW laser source.

This technique lays the foundation for ultra-stable laser systems in the vacuum ultraviolet band and completes a key technical step in related international research programs.

Beyond nuclear clock research, the platform could support applications in atomic clocks, quantum information and condensed matter spectroscopy, the researchers said.

The advance is also expected to underpin applications such as autonomous navigation, deep-space exploration and high-precision geophysical and gravitational measurements, as well as vacuum ultraviolet metrology and advanced testing equipment.

Meanwhile, the State Administration for Market Regulation announced a Chinese-developed optical clock named NIM-Sr1 has contributed to the calibration of International Atomic Time (TAI) on Tuesday.