Modulated ringdown comb interferometry for sensing of highly complex gases

• 成果类型: Article
• 署名作者: Liang, Qizhong; Bisht, Apoorva; Scheck, Andrew; Schunemann, Peter G.; Ye, Jun
• 署名单位: National Institute of Standards & Technology (NIST) - USA; University of Colorado System; University of Colorado Boulder; Bae Systems
• 刊物名称: Nature
• ISSN/ISSBN: 0028-1707
• DOI: 10.1038/s41586-024-08534-2
• 发表日期: 2025-02-27
• 关键词: optical frequency comb; fourier-transform; greenhouse gases; exhaled breath; spectroscopy; air; oxide; absorption; molecules; emissions

摘要

Gas samples relevant to health1, 2-3 and the environment4, 5-6 typically contain many molecular species that span a huge concentration dynamic range. Mid-infrared frequency comb spectroscopy with high-finesse cavity enhancement has allowed the most sensitive multispecies trace-gas detections so far2,7, 8, 9, 10, 11, 12-13. However, the robust performance of this technique depends critically on ensuring absorption-path-length enhancement over a broad spectral coverage, which is severely limited by comb-cavity frequency mismatch if strongly absorbing compounds are present. Here we introduce modulated ringdown comb interferometry, a technique that resolves the vulnerability of comb-cavity enhancement to strong intracavity absorption or dispersion. This technique works by measuring ringdown dynamics carried by massively parallel comb lines transmitted through a length-modulated cavity, making use of both the periodicity of the field dynamics and the Doppler frequency shifts introduced from a Michelson interferometer. As a demonstration, we measure highly dispersive exhaled human breath samples and ambient air in the mid-infrared with finesse improved to 23,000 and coverage to 1,010 cm-1. Such a product of finesse and spectral coverage is orders of magnitude better than all previous demonstrations2,7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19-20, enabling us to simultaneously quantify 20 distinct molecular species at above 1-part-per-trillion sensitivity varying in concentrations by seven orders of magnitude. This technique unlocks next-generation sensing performance for complex and dynamic molecular compositions, with scalable improvement to both finesse and spectral coverage.