#Spectral comb sound reference signals full

High coherence is essential to take full advantage of DCS, which ensures stable comb teeth in the RF domain. DCS provides complex responses, including amplitude and phase. Compared with the conventional Fourier transform spectroscopy (FTS), dual-comb spectroscopy has advantages in acquiring speed and spectral resolution without a mechanical delay stage. DCS has attracted considerable attention as a compact, rapid, and accurate approach with individual comb line measurements. Every heterodyne frequency in the RF domain is related to an optical mode with a down-conversion factor. The slightly different repetition rate ensures that the heterodyne interferograms between every pair of comb teeth have different frequency. In the frequency domain, these discrete laser modes of the OFC heterodyne with each other. These two combs have big differences in repetition rates which improve the resolution of DCS effectively. However, the repetition of local comb is several times the signal comb in some special designs. In general, OFCs have slight differences in repetition rate. Dual-comb spectroscopy (DCS) employs the advantage of the OFC to down-conversion of the optical spectrum to the radio frequency (RF) spectrum. The OFC presents discrete modes in the optical frequency domain. The optical frequency comb (OFC) has been demonstrated to be a powerful tool with many attractive features in many applications, including optical clocks, microwave generation, and ultra-precision metrology in fundamental physics. It verifies that DCS has the potential to be applied in standoff detection, environmental pollution monitors, and remote sensing. The longitudinal precision is 0.68 μm with a measurement time of 0.5 s. Finally, we demonstrate that non-contact surface imaging, using 2D mechanical scanning, reaches lateral resolution of 40 μm. From the same interferograms, we demonstrate that distance measurement, by time-of-flight (TOF), can be resolved with an rms precision of 0.53 μm after averaging 140 images and a measurement time of 1 s. As a demonstration, we measure the spectrum of CO 2 and CO. The combination of the high-coherence dual-comb spectrometer and a reference arm simultaneously enables gas absorption spectroscopy and for the absolute distance information to be obtained in one measurement. With two tightly phase-locking frequency combs, we demonstrate a high-coherence dual-comb interferometer (DCI) covering 188 to 195 THz (1538.5 to 1595.7 nm) with comb-tooth resolution and a max spectral signal-to-noise ratio (SNR) of 159.7. In this paper, we report a scheme providing precise spectral analysis and surface imaging, simultaneously, based on a high-coherence dual-comb interferometer.