Dispersive heterodyne cavity ring-down spectroscopy exploiting eigenmode frequencies for high-fidelity measurements.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39879293.
- Also identified by DOI 10.1126/sciadv.adp8556 and PMC identifier 13108742.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Measuring low light absorption with combined uncertainty <1 per mil (‰) is crucial for many applications. Popular cavity ring-down spectroscopy can provide ultrahigh precision, below 0.01‰, but its accuracy is often worse than 5‰ due to inaccuracies in light intensity measurements. To eliminate this problem, we exploit optical frequency information carried by the ring-down cavity electromagnetic field. Instead of measuring only the decaying light intensity, we perform heterodyne detection of ring-downs followed by Fourier analysis to provide exact frequencies of optical cavity modes and a high-fidelity dispersive spectrum of a gas sample from them. We demonstrate the sub-per-mil accuracy of our method, confirmed by the best ab initio results for CO line intensity and for HD line shape, and the long-term repeatability of our dispersion measurements at 10<sup>-4</sup> level. We see potential for our approach in atmospheric remote sensing, isotope ratio metrology, thermometry, and establishment of primary gas standards.