Fig. 1
Sketch of the principle of feed-forward dual-comb spectroscopy. A self-referenced master comb provides long-term stability and the slave frequency comb follows the drifts of the master comb, providing high-bandwidth mutual coherence. The difference in carrier-envelope offset frequencies is kept constant by a feed-forward stabilization scheme that acts, through an acousto-optic frequency shifter (aofs), on the carrier-envelope offset frequency fceo + δfceo of the slave beam. The beam of the master comb interogates the sample and beats with the beam emerging from the acousto-optic frequency shifter in the first-order of diffraction beam. The optical signal is detected with a balanced differential detector and is digitized
