Generation of continuous-wave laser light at 148.4 nm using cavity-enhanced second harmonic generation in BaMgF₄

@misc{subramanian2026generation,
  title = {{Generation of continuous-wave laser light at 148.4 nm using cavity-enhanced second harmonic generation in $BaMgF_4$}},
  author = {Keerthan Subramanian and Hiroki Tanaka and Simon J. Herr and Nutan Kumari Sah and Gaurav Jha and Florian Zacherl and Srinivasa Arasada Pradeep and Valerii Andriushkov and Ke Zhang and Darius Fenner and Yumiao Wang and Milena Hugenschmidt and Frank Kühnemann and Gaetano G. M. Bonetti and Shoichi Ui and Matthias Bickermann and Chenxi Ma and Xian Zheng and Michael Zopf and Bettina Lommel and Jan C. Müller and Stephan Hannig and Dmitry Budker and Ferdinand Schmidt-Kaler and Lars von der Wense},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2606.25046},
  eprint = {2606.25046},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2606.25046},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Generation of continuous-wave laser light at 148.4 nm using cavity-enhanced second harmonic generation in BaMgF_4
AU  - Keerthan Subramanian
AU  - Hiroki Tanaka
AU  - Simon J. Herr
AU  - Nutan Kumari Sah
AU  - Gaurav Jha
AU  - Florian Zacherl
AU  - Srinivasa Arasada Pradeep
AU  - Valerii Andriushkov
AU  - Ke Zhang
AU  - Darius Fenner
AU  - Yumiao Wang
AU  - Milena Hugenschmidt
AU  - Frank Kühnemann
AU  - Gaetano G. M. Bonetti
AU  - Shoichi Ui
AU  - Matthias Bickermann
AU  - Chenxi Ma
AU  - Xian Zheng
AU  - Michael Zopf
AU  - Bettina Lommel
AU  - Jan C. Müller
AU  - Stephan Hannig
AU  - Dmitry Budker
AU  - Ferdinand Schmidt-Kaler
AU  - Lars von der Wense
PY  - 2026
DA  - 2026/10/12
PB  - arXiv
DO  - 10.48550/arxiv.2606.25046
UR  - https://arxiv.org/abs/2606.25046
AB  - The development of a nuclear optical clock based on \textsuperscript{229}Th is expected to influence the next generation of time and frequency standards. At its heart is the need for a continuous wave (CW) at laser at 148.4~nm to drive the clock transition between the ground and excited isomeric state. In this work we experimentally investigate the potential of BaMgF\textsubscript{4} crystals to create a CW solid state laser at the vacuum ultraviolet (VUV) wavelength of 148.4~nm via cavity-enhanced second harmonic generation. For this purpose, a BaMgF\textsubscript{4} crystal was grown, optically polished and periodically poled. The crystal was inserted into a power-enhancement cavity, resonant at the fundamental wavelength of 296.8~nm and the generated laser light at 148.4~nm was characterized. Within this proof-of-concept investigation, a VUV output power of typically (16±1)~pW is obtained. This marks the first time that this type of crystal is used to generate VUV laser light. The experimental findings are compared to theoretical expectations and provide a clear path for future improvements, which could have implications not only for compact laser sources in the VUV but also solid-state as well as single-ion based \textsuperscript{229}Th nuclear clocks.
ER  -