Continuous-wave narrow-linewidth vacuum ultraviolet laser source

Qi Xiao; Gleb Penyazkov; Xiangliang Li; Beichen Huang; Wenhao Bu; Juanlang Shi; Haoyu Shi; Tangyin Liao; Gaowei Yan; Haochen Tian; Yixuan Li; Jiatong Li; Bingkun Lu; Li You; Yige Lin; Yuxiang Mo; Shiqian Ding

doi:10.1038/s41586-026-10107-4

Continuous-wave narrow-linewidth vacuum ultraviolet laser source

Nature. 2026 Feb;650(8103):852-856. doi: 10.1038/s41586-026-10107-4. Epub 2026 Feb 11.

Authors

Qi Xiao^#^{1

2}, Gleb Penyazkov^#¹, Xiangliang Li^#², Beichen Huang^{1

2}, Wenhao Bu^{1

2}, Juanlang Shi¹, Haoyu Shi¹, Tangyin Liao³, Gaowei Yan^{1

2}, Haochen Tian⁴, Yixuan Li¹, Jiatong Li¹, Bingkun Lu⁴, Li You^{1

2

5}, Yige Lin⁴, Yuxiang Mo¹, Shiqian Ding^{6

7

8}

Affiliations

¹ State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, China.
² Beijing Academy of Quantum Information Sciences, Beijing, China.
³ Department of Precision Instrument, Tsinghua University, Beijing, China.
⁴ Division of Time and Frequency Metrology, National Institute of Metrology, Beijing, China.
⁵ Frontier Science Center for Quantum Information, Beijing, China.
⁶ State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, China. dingshq@mail.tsinghua.edu.cn.
⁷ Beijing Academy of Quantum Information Sciences, Beijing, China. dingshq@mail.tsinghua.edu.cn.
⁸ Frontier Science Center for Quantum Information, Beijing, China. dingshq@mail.tsinghua.edu.cn.

^# Contributed equally.

PMID: 41673153
DOI: 10.1038/s41586-026-10107-4

Abstract

The exceptionally low-energy isomeric transition in ²²⁹Th at around 148.4 nm (refs. ^1-6) offers a unique opportunity for coherent nuclear control and the realization of a nuclear clock^7,8. Recent advances, most notably the incorporation of large ensembles of ²²⁹Th nuclei in transparent crystals^6,9-11 and the development of pulsed vacuum ultraviolet (VUV) lasers^12-14, have enabled initial laser spectroscopy of this transition^15-17. However, the lack of an intense, narrow-linewidth VUV laser has precluded coherent nuclear manipulation^8,18. Here we introduce and report a continuous-wave (CW) laser at 148.4 nm, generated by means of four-wave mixing (FWM)¹⁹ in cadmium vapour. The source delivers more than 100 nW of power with a projected linewidth well below 100 Hz and supports broad wavelength tunability. This represents a five-orders-of-magnitude improvement in linewidth over all previous single-frequency lasers below 190 nm (refs. ^12-14,20). We develop a spatially resolved homodyne technique that places a stringent upper bound on FWM-induced phase noise, thereby supporting the feasibility of sub-hertz VUV linewidths. Our work addresses the central challenge towards a ²²⁹Th-based nuclear clock and establishes a widely tunable, ultranarrow-linewidth laser platform for potential applications across quantum information science^21-24, condensed-matter physics²⁵ and high-resolution VUV spectroscopy²⁶.