Mid-infrared supermirrors with finesse exceeding 400 000

• DOI: 10.1038/s41467-023-43367-z
• Publication Date: 2023-12-06T11:02:44Z
• Authors: Gar-Wing Truong; Lukas W. Perner; D. Michelle Bailey; Georg Winkler; Seth B. Cataño-Lopez; Valentin J. Wittwer; Thomas Südmeyer; Catherine Nguyen; David Follman; Adam J. Fleisher; Oliver H. Heckl; Garrett D. Cole
• Keywords: Finesse; Cavity Ring-Down Spectroscopy; Trace gas; Optical cavity; Optical path

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