Fig. 5
Experimental dual-comb spectrum at a resolution of 100 MHz in the 180-THz region. a The amplitude spectrum of the 2ν3 band of 12CH4 spans 9 THz and it is measured within 14.46 s. b Transmittance (blue) and dispersion (red) spectra. c Portion of the transmittance spectrum (blue open dots, labeled observed), magnifying the Q(1) line with about 13% of absorption at line center. The Doppler full width at half maximum of the Q(1) line at 295 K is approximately 554 MHz. The experimental profile is satisfactorily fitted by a Doppler line shape (red line, labeled fitted). The standard deviation of the residuals observed-fitted is 0.3%, at the noise level
