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<p>Frequency comb spectroscopy has significantly advanced molecular spectroscopy across scientific research and diverse applications. Among its key performance metrics especially for time-resolved studies, sensitivity and measurement speed are paramount. However, a long-standing compromise between these parameters arises from the need for noise reduction. Here, we introduce a comb spectroscopy system that overcomes this limitation using a single frequency comb of non-uniformly spaced modes. The comb is generated using a simple optical setup, composed of a continuous-wave (CW) fiber laser and a single-sideband phase modulator (SSM). Our approach delivers optical-to-radio-frequency conversion comparable to dual-comb spectroscopy (DCS) but through a self-heterodyning architecture. By leveraging the intrinsic mutual coherence of the comb, this design achieves a noise-equivalent absorption (NEA) of 5.0×10<sup>−6 </sup>Hz<sup>−1/2</sup>—an order-of-magnitude improvement over state-of-the-art DCS, coupled with long-term stability. The system resolves weak molecular overtone spectra on nanosecond timescales, in a single-shot measurement, with absorption noise as low as 2%, markedly lower than prior demonstrations. This integration of high sensitivity and speed resolves the core trade-off that has long constrained time-resolved spectroscopic analysis.</p>

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Self-heterodyne spectroscopy via a non-uniformly spaced frequency comb

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月14日

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  • Bofeng Zhang,
  • Gang Zhao,
  • Xiaobin Zhou,
  • Xiaojuan Yan,
  • Jiaqi Yang,
  • Weiguang Ma,
  • Suotang Jia

摘要

Frequency comb spectroscopy has significantly advanced molecular spectroscopy across scientific research and diverse applications. Among its key performance metrics especially for time-resolved studies, sensitivity and measurement speed are paramount. However, a long-standing compromise between these parameters arises from the need for noise reduction. Here, we introduce a comb spectroscopy system that overcomes this limitation using a single frequency comb of non-uniformly spaced modes. The comb is generated using a simple optical setup, composed of a continuous-wave (CW) fiber laser and a single-sideband phase modulator (SSM). Our approach delivers optical-to-radio-frequency conversion comparable to dual-comb spectroscopy (DCS) but through a self-heterodyning architecture. By leveraging the intrinsic mutual coherence of the comb, this design achieves a noise-equivalent absorption (NEA) of 5.0×10−6 Hz−1/2—an order-of-magnitude improvement over state-of-the-art DCS, coupled with long-term stability. The system resolves weak molecular overtone spectra on nanosecond timescales, in a single-shot measurement, with absorption noise as low as 2%, markedly lower than prior demonstrations. This integration of high sensitivity and speed resolves the core trade-off that has long constrained time-resolved spectroscopic analysis.