We study the frequency noise and the referencing to a near-infrared frequency comb of a widely tunable external-cavity quantum-cascade-laser that shows a relatively narrow free-running emission linewidth of 1.7 MHz. The frequency locking of the laser to the comb further narrows its linewidth to 690 kHz and enables sub-Doppler spectroscopy on an N2O transition of the ν1 band near 7.7 μm with sub-MHz resolution and absolute frequency calibration. The combined uncertainty on the measured transition center is estimated to be less than 50 kHz
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): OSR-2018-CARF-1975-06
Acknowledgements: King Abdullah University of Science and Technology (OSR-2018-CARF-1975-06), Fondazione Cariplo and Regione Lombardia (2016-1428).