High Precision, SI-traceable, Mid-Infrared Molecular Spectroscopy

SummaryWe present SI-traceable mid-infrared high-resolution saturated absorption spectroscopy measurements conducted on methanol. Resolutions of few hundreds of kilohertz and record sensitivities of a few kilohertz (10
⁻¹⁰
) on transition center frequencies are obtained in a multi-pass cell. Promising results have also been obtained in transmission of a 3-m long Fabry-Perot cavity yielding resolutions of a few tens of kilohertz which paves the way to the sub-kilohertz (10
⁻¹²
) level of vibrational frequency accuracy.