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arXiv · 2209.09902

Mid-infrared supermirrors with finesse exceeding 400 000

G. -W. Truong·L. W. Perner·D. M. Bailey·G. Winkler·S. B. Cataño-Lopez·V. J. Wittwer·T. Sudmeyer·C. Nguyen·D. Follman·A. J. Fleisher·O. H. Heckl·G. D. Cole
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Abstract

For trace gas sensing and precision spectroscopy, optical cavities incorporating low-loss mirrors are indispensable for path length and optical intensity enhancement. Optical interference coatings in the visible and near-infrared (NIR) spectral regions have achieved total optical losses below 2 parts per million (ppm), enabling a cavity finesse in excess of 1 million. However, such advancements have been lacking in the mid-infrared (MIR), despite substantial scientific interest. Here, we demonstrate a significant breakthrough in high-performance MIR mirrors, reporting substrate-transferred single-crystal interference coatings capable of cavity finesse values from 200 000 to 400 000 near 4.5 um, with excess optical losses (scatter and absorption) below 5 ppm. In a first proof-of-concept demonstration, we achieve the lowest noise-equivalent absorption in a linear cavity ring-down spectrometer normalized by cavity length. This substantial improvement in performance will unlock a rich variety of MIR applications for atmospheric transport and environmental sciences, detection of fugitive emissions, process gas monitoring, breath-gas analysis, and verification of biogenic fuels and plastics.

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G. -W. Truong, L. W. Perner, D. M. Bailey, G. Winkler, S. B. Cataño-Lopez, V. J. Wittwer, T. Sudmeyer, C. Nguyen, D. Follman, A. J. Fleisher, O. H. Heckl, G. D. Cole. 2022-09-14. Mid-infrared supermirrors with finesse exceeding 400 000. https://doi.org/10.1038/s41467-023-43367-z

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