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arXiv · 2602.07337

Broadband terahertz comb with sub-Hz comb linewidth

Min Li·Yu Xia·Yuan Chen·Sinan Tao·Mingyang He·Kun Huang·Hua Li·Ming Yan·Heping Zeng
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Abstract

Terahertz (THz) frequency combs are increasingly essential for spectroscopy, metrology, and quantum science. However, generating a dense array of evenly spaced ultra-narrow THz comb lines is challenging. Here, we demonstrate broadband THz comb generation using a photoconductive antenna that transfers a noise-suppressed near-infrared electro-optical (EO) comb into the THz domain. Our noise-suppression strategy, leveraging soliton self-frequency shift and spectral filtering, effectively suppresses EO comb phase noise without requiring active stabilization. The resulting THz comb exhibits broad spectral coverage (0.05-4 THz), narrow comb linewidths (0.3 Hz at the Fourier-transform limit), and excellent frequency stability (8.6*10^-14 at 1-second integration). We further demonstrate asynchronous THz time-domain spectroscopy, resolving ~36,000 comb lines with 50 MHz spacing. Crucially, the inherent frequency agility of the EO comb enables rapid and wide-range tuning of the THz comb line spacing. These attributes position our THz comb as a versatile tool for high-resolution molecular spectroscopy and precision THz metrology.

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Min Li, Yu Xia, Yuan Chen, Sinan Tao, Mingyang He, Kun Huang, Hua Li, Ming Yan, Heping Zeng. 2026-02-07. Broadband terahertz comb with sub-Hz comb linewidth. https://arxiv.org/abs/2602.07337

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