Precision Molecular Spectroscopy with Frequency Combs

The advent of frequency combs has given tremendous impulse to the fields of high-resolution molecular spectroscopy and trace sensing of multiple gases. The combs' secret lies in their fine, discrete, stable, reproducible, and controllable spectral structure, readily referable to the primary microwave standard. These features make combs ideal tools to obtain on one side precision as well as absolute frequency calibration in the spectroscopic detection of individual absorption lines and, on the other side, to develop a new class of spectrometers where broadband coupling of combs to passive optical cavities allows extreme sensitivity to be conjugated with spectral resolution, broad spectral coverage, and fast acquisition times.