Highly sensitive dual-comb spectroscopy using background-suppressed spectral peaking

Spectral peaking is an interesting phenomenon in which a spectral-peaked comb is generated at a specific wavelength through a nonlinear phase shift in an optical fiber. In this study, spectral peaking was applied to a dual-comb spectroscopy system based on an all-polarization-maintaining Er-doped mode-locked fiber laser. Because sharp spectral peaks were generated exclusively at the absorption wavelength, detector saturation was avoided without attenuation. The signal intensity increased by 60-fold, and the signal-to-noise ratio was improved from 10 to 22 dB for a single shot and from 23 to 35 dB after 500 averages compared with systems using tunable soliton pulses. The dynamic range was also substantially improved, increasing from 16 to more than 35 dB. This technique can be applied to a wide wavelength band and is useful for spectroscopic applications.