Expérimental
Ultra-high resolution molecular spectroscopy is an interdisciplinary field with fascinating applications ranging from fundamental physics to astrophysics, earth sciences, remote sensing, metrology and quantum technologies. Among recent instrumental advances, the stabilization of quantum cascade lasers (QCLs) on optical frequency combs with traceability to primary frequency standards, a method recently implemented in our team, is a breakthrough technology. It offers an unprecedented level of precision in the mid-infrared, an essential region known as the molecular fingerprint region, which hosts a considerable number of intense vibrational signatures of molecules of various interests. This opens up prospects for carrying out fundamental physics tests and exploring the limits of the Standard Model, and for providing precise spectroscopic data on species of astrophysical or atmospheric interest, which is a crucial information for environmental and human health issues. We have for instance recently measured rovibrational frequencies in methanol with 11-digits accuracy by carrying out saturated absorption spectroscopy in a multi-pass cell and in a Fabry-Perot cavity enhanced spectroscopy, a more than 4 orders of magnitude improvement compared to previous measurements reported in the literature.