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arXiv · 2610.18470

Continuous-wave 148.4-nm generation in strontium tetraborate for nuclear absorption spectroscopy

Hanlin Wang·Zhouzhi Tan·Conghui Huang·Jinming Liu·Xuan Fan·Runzhe Yang·Meng Wang·Tung-Hsun Chung·Yong-Heng Huo·Yin Hang·Zhiwei Jiao·Heng Tu·Lei Zhang·Xu-Fei Yin·Pengfei Wang·Zhiqiang Zhang
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Abstract

Continuous-wave light near 148.4 nm enables direct absorption spectroscopy of the thorium-229 nuclear transition. We demonstrate single-pass frequency doubling in strontium tetraborate, delivering an estimated 8.1 nW at 920 mW pump power. At this power, oxygen admission leaves a background of 1.22 kHz, corresponding to an estimated signal-to-background ratio of 3.8 x 10^4 after current-integration calibration. Several crystals grown by top-seeded solution growth produce polarization-dependent VUV signals. Temperature scans reveal distinct maxima among specimens cut from one boule and among positions within a specimen. The source sustains operation over 33.3 h. In a separate 3-h record acquired with 1-ms gates, local referencing achieves near-Poisson averaging, reaching a fractional Allan deviation of 3.5 x 10^-5 at 1000 s. These results establish a practical VUV source for stable, long-duration spectroscopy of weak nuclear absorption.

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Hanlin Wang, Zhouzhi Tan, Conghui Huang, Jinming Liu, Xuan Fan, Runzhe Yang, Meng Wang, Tung-Hsun Chung, Yong-Heng Huo, Yin Hang, Zhiwei Jiao, Heng Tu, Lei Zhang, Xu-Fei Yin, Pengfei Wang, Zhiqiang Zhang. 2026-10-13. Continuous-wave 148.4-nm generation in strontium tetraborate for nuclear absorption spectroscopy. https://arxiv.org/abs/2610.18470

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