Generation and spectroscopic characterization of continuous-wave 148.4-nm light in strontium tetraborate
Abstract
Continuous-wave (CW) radiation at 148.4~nm is required to drive the 229Th isomeric transition of a solid-state nuclear clock, and frequency doubling of 296.8-nm light is its most direct source. We generate CW 148.4-nm light by random quasi-phase matching in strontium tetraborate and characterize it with a compact prism spectrometer built for the purpose. The spectrometer separates the harmonic from the pump on a CaF2 prism, reads the wavelength from the rotation angle of a solar-blind photomultiplier, resolves the two lines with δλ≈ 0.6 nm, and yields an absolute power calibration. At room temperature the source delivers 1.9 nW at 148.4~nm, rising to 5.7 nW at the optimum crystal temperature. The conversion efficiency is also strongly structured in temperature: between 30 degree and 50 degree it shows several pronounced maxima, with neighbouring extrema only a few degrees apart, so that a small temperature excursion moves the output from a maximum to a minimum. These results provide practical guidance for optimizing and stabilizing 148.4-nm sources for solid-state 229Th nuclear clocks.
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BibTeX
@misc{guan2026generation,
title = {{Generation and spectroscopic characterization of continuous-wave 148.4-nm light in strontium tetraborate}},
author = {Ming Guan and Yang Wang and Heng Tu and Kaifgeng Zhou and Zhengrong Xiao and Zhong Zuo and Songpo Xu and Shaogang Yu and Xin Tong and Linqiang Hua and Xiaojun Liu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.42055},
eprint = {2610.42055},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.42055},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Generation and spectroscopic characterization of continuous-wave 148.4-nm light in strontium tetraborate
AU - Ming Guan
AU - Yang Wang
AU - Heng Tu
AU - Kaifgeng Zhou
AU - Zhengrong Xiao
AU - Zhong Zuo
AU - Songpo Xu
AU - Shaogang Yu
AU - Xin Tong
AU - Linqiang Hua
AU - Xiaojun Liu
PY - 2026
DA - 2026/10/30
PB - arXiv
DO - 10.48550/arxiv.2610.42055
UR - https://arxiv.org/abs/2610.42055
AB - Continuous-wave (CW) radiation at 148.4~nm is required to drive the ^229Th isomeric transition of a solid-state nuclear clock, and frequency doubling of 296.8-nm light is its most direct source. We generate CW 148.4-nm light by random quasi-phase matching in strontium tetraborate and characterize it with a compact prism spectrometer built for the purpose. The spectrometer separates the harmonic from the pump on a CaF_2 prism, reads the wavelength from the rotation angle of a solar-blind photomultiplier, resolves the two lines with δλ≈ 0.6 nm, and yields an absolute power calibration. At room temperature the source delivers 1.9 nW at 148.4~nm, rising to 5.7 nW at the optimum crystal temperature. The conversion efficiency is also strongly structured in temperature: between 30 degree and 50 degree it shows several pronounced maxima, with neighbouring extrema only a few degrees apart, so that a small temperature excursion moves the output from a maximum to a minimum. These results provide practical guidance for optimizing and stabilizing 148.4-nm sources for solid-state ^229Th nuclear clocks.
ER -