A compact vapor-cell optical frequency reference with fractional frequency instability around $10^{-16}$

Siqi Wu; Zhenqi Zhang; Xingyue Liu; Chuanshuai Zhu; Zhiyuan Wang; Zhiyu Ma; Hongli Liu; Wenhao Yuan; Xiaochi Liu; Pengfei Wang; Feng Zhao; Jan Hrabina; Jie Zhang; Zehuang Lu; Ke Deng

arXiv · 2603.00424

A compact vapor-cell optical frequency reference with fractional frequency instability around $10^{-16}$

Siqi Wu·Zhenqi Zhang·Xingyue Liu·Chuanshuai Zhu·Zhiyuan Wang·Zhiyu Ma·Hongli Liu·Wenhao Yuan·Xiaochi Liu·Pengfei Wang·Feng Zhao·Jan Hrabina·Jie Zhang·Zehuang Lu·Ke Deng

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Abstract

Compact optical frequency reference with high stability is essential for field applications such as navigation and geodesy, yet vapor cell systems have remained confined to fractional instabilities over $10^{-15}$. Here, we report a molecular iodine reference that reaches an instability of $7 \times 10^{-16}$ at 1000 s and operates at the $10^{-16}$ level from 200 to 2000 s, surpassing the best reported vapor cell standards by approximately a factor of three. This achievement is enabled by a monolithic, drift immune spectroscopic unit bonded to an ultra low expansion glass substrate with precision control of key parameters.The entire system occupies only 25 L.The system achieves $5 \times 10^{-15}$ instability at 1 s and reaches the $10^{-16}$ level over the 200 to 2000 s averaging-time range, representing the first medium term stability at the $10^{-16}$ level from a compact, field ready vapor-cell reference. Our work demonstrates that $10^{-16}$ instability can be engineered into portable systems, opening a path to high precision time-keeping beyond the laboratory.

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Siqi Wu, Zhenqi Zhang, Xingyue Liu, Chuanshuai Zhu, Zhiyuan Wang, Zhiyu Ma, Hongli Liu, Wenhao Yuan, Xiaochi Liu, Pengfei Wang, Feng Zhao, Jan Hrabina, Jie Zhang, Zehuang Lu, Ke Deng. 2026-02-28. A compact vapor-cell optical frequency reference with fractional frequency instability around $10^{-16}$. https://arxiv.org/abs/2603.00424

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