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Velocity-comb modulation transfer spectroscopy

Xiaolei Guan1, Zheng Xiao1, Zijie Liu1, Zhiyang Wang1, Jia Zhang1, Xun Gao1, Pengyuan Chang2, Tiantian Shi3,*, and Jingbiao Chen1,4,5

  • 1State Key Laboratory of Photonics and Communications, Institute of Quantum Electronics, School of Electronics, Peking University, Beijing 100871, China
  • 2Institute of Quantum Information and Technology, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
  • 3National Key Laboratory of Advanced Micro and Nano Manufacture Technology, School of Integrated Circuits, Peking University, Beijing 100871, China
  • 4Hefei National Laboratory, Hefei 230088, China
  • 5Peking University Handan Innovation Institute, Handan 056107, China

  • *Contact author: tts@pku.edu.cn
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Phys. Rev. Applied 24, 064018 – Published 4 December, 2025

DOI: https://doi.org/10.1103/rwzv-p2fj

Abstract

Sub-Doppler laser spectroscopy is crucial for laser-frequency stabilization, playing a significant role in atomic physics and precision measurement. However, despite decades of development, inefficient atomic utilization remains a widespread issue. Most existing methods rely on single-frequency lasers, and due to the Doppler effect, only a small fraction (<1%) of atoms with near-zero longitudinal velocities are utilized, severely limiting improvements in the spectral signal-to-noise ratio (S/N). Here, we propose a velocity-comb modulation transfer spectroscopy (VC-MTS) solution that leverages the velocity-selective resonance of modulated N-frequency lasers, seeming as an optical comb, to enhance the utilization of nonzero-velocity atoms, which optimizes the spectral amplitude and frequency instability by N and N times, respectively. Unlike traditional MTS, in this work, each pair of counterpropagating lasers interacts with atoms from different longitudinal velocity groups, independently contributing to the amplitude and S/N. Preliminary proof-of-principle results show that the frequency stability of the triple-frequency laser is improved by 3 times compared to the single-frequency laser. With more frequency components, VC-MTS stabilized lasers are expected to achieve order-of-magnitude breakthroughs in frequency stability, taking an essential step toward next-generation compact optical clocks. This method also applies to quantum systems with wide velocity distributions, offering an innovative perspective on laser spectroscopy and inspiring further intriguing applications.

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Phys. Rev. Applied 24, 064018– Published 4 December, 2025
  • Received 12 May 2025
  • Revised 14 October 2025
  • Accepted 17 November 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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