Fig. 3
From: Passive coherent dual-comb spectroscopy based on optical-optical modulation with free running lasers
Mode-resolved dual comb spectra. a) The continuous record multi-heterodyne signal over 100 s, enlarged to show 1 s, 50 s, and 100 s. b) The zero-offset adaptive spectra (log scale) after FFT analysis from two 100 s recordings corresponding to different optical domains. The top scale shows the optical frequency retrieved from the bottom RF scale. c) Expanded view showing some attenuation modes for the C2H2 absorptions (linear scale, top panel). The standard C2H2 transmittance spectra from HITRAN database [31] are shown in the bottom panel. d,e) Enlarged plots (linear scale) revealing resolved comb-tooth structure. The insert shows a comb tooth with 10 mHz linewidth in two recordings