Laser frequency combs for molecular fingerprinting

Measuring the beating signal between two phase-coherent frequency combs leads to a novel broadband spectroscopy, which improves a million-fold the resolution, the recording time and the accuracy of the frequency scale of Fourier transform spectroscopy, which has been up to now the most efficient technique for multiplex optical diagnostics. With a demonstrated thousand-fold enhancement of the absorption signal thanks to a high finesse cavity, the method proves promising for real-time detection of trace gases.