Addressing asymmetric Fano profiles on molecular lines in dual-comb spectroscopy

Fano resonance in molecular spectroscopy is reported with a dual-comb instrument. The effect is observed as asymmetric absorption lines of (HCN)-C-12. Pulse chirping conditions in the gas cell are varied to show that Fano resonance is dependent on the pulse peak power. A model adding the Fano profile to Voigt lines is used to estimate Fano phase as a function of pulse peak power. A pulse peak power condition is derived from this analysis to avoid line shape distortion in pulsed laser experiments. (C) 2022 Optica Publishing Group