Accurate recovery of the two linewidths hidden in laser beatnote statistics
Abstract
Photons from ultrastable lasers can remain coherent over distances approaching the Earth-Sun separation, enabling optical clocks projected to lose less than one second over the age of the Universe. Yet characterizing these photons poses an identifiability problem: a two-laser heterodyne measurement produces a single beatnote linewidth that conflates contributions from both lasers. For more than half a century, the standard solution has been the three-cornered-hat (TCH) method, which requires three independent ultrastable lasers. Here we derive the mathematical form and elucidate the physical origin of asymmetric beatnote-linewidth distributions arising from finite photon wave trains, a long-observed feature not captured by canonical Gaussian or Lorentzian statistics. This finding accurately recovers two linewidths hidden in laser beatnote statistics without a third laser. The framework consistently captures the observed coherence-length and coherence-time statistics of photons, while comparison with TCH measurements confirms the quantitative validity of the extracted individual linewidths across five independent ultrastable-laser datasets spanning nearly two orders of magnitude. Most notably, the method resolves the 7.8-mHz linewidth of a cryogenic silicon-cavity laser beating with a broader laser. This transformative function of beatnote-linewidth distributions, together with the resulting method, could fundamentally advance optical clocks and precision metrology.
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BibTeX
@misc{chen2026accurate,
title = {{Accurate recovery of the two linewidths hidden in laser beatnote statistics}},
author = {Jingming Chen and Yuanchen Qi and Yuzheng Pang and Jie Miao and Congyu Wang and Yuan Yao and Zhi-Ang Chen and Run-Qi Lei and Zheyi Ge and Yanyi Jiang and Xibo Zhang and Xiaopeng Xie and Jianjun Wu and Duo Pan and Jingbiao Chen},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.36592},
eprint = {2609.36592},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.36592},
}
RIS
TY - UNPB
TI - Accurate recovery of the two linewidths hidden in laser beatnote statistics
AU - Jingming Chen
AU - Yuanchen Qi
AU - Yuzheng Pang
AU - Jie Miao
AU - Congyu Wang
AU - Yuan Yao
AU - Zhi-Ang Chen
AU - Run-Qi Lei
AU - Zheyi Ge
AU - Yanyi Jiang
AU - Xibo Zhang
AU - Xiaopeng Xie
AU - Jianjun Wu
AU - Duo Pan
AU - Jingbiao Chen
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.36592
UR - https://arxiv.org/abs/2609.36592
AB - Photons from ultrastable lasers can remain coherent over distances approaching the Earth-Sun separation, enabling optical clocks projected to lose less than one second over the age of the Universe. Yet characterizing these photons poses an identifiability problem: a two-laser heterodyne measurement produces a single beatnote linewidth that conflates contributions from both lasers. For more than half a century, the standard solution has been the three-cornered-hat (TCH) method, which requires three independent ultrastable lasers. Here we derive the mathematical form and elucidate the physical origin of asymmetric beatnote-linewidth distributions arising from finite photon wave trains, a long-observed feature not captured by canonical Gaussian or Lorentzian statistics. This finding accurately recovers two linewidths hidden in laser beatnote statistics without a third laser. The framework consistently captures the observed coherence-length and coherence-time statistics of photons, while comparison with TCH measurements confirms the quantitative validity of the extracted individual linewidths across five independent ultrastable-laser datasets spanning nearly two orders of magnitude. Most notably, the method resolves the 7.8-mHz linewidth of a cryogenic silicon-cavity laser beating with a broader laser. This transformative function of beatnote-linewidth distributions, together with the resulting method, could fundamentally advance optical clocks and precision metrology.
ER -