Amplitude and phase-resolved common-path dual-comb sensing

Symmetric dual-comb spectroscopy involves the transmission of two optical frequency combs, featuring marginally distinct repetition rates, through the sample being examined. Conventionally, such an arrangement is viewed as appropriate solely for determining the amplitude of the sample’s spectral response, whereby phase data is generally relinquished to attain a more stable configuration resistant to variations in the measurement pathways, relative to an asymmetric arrangement. Here, we develop and exhibit an algorithm that can retrieve the spectral phase details of a sample via the examination of high-order Nyquist zones within a symmetric dual-comb spectroscopy setup. This phase reconstruction approach is extended to include both conventional and quasi-integer ratio (QIR) dual-comb methodologies. The proficiency in retrieving both the amplitude and phase spectral characteristics through the application of this extended phase-reconstruction algorithm in a symmetric setup is substantiated using two specimens, namely a lossy fiber-based ring resonator and a traceable hydrogen cyanide (HCN) gas cell.