Measurement of Absorption Spectroscopy Based on a Dispersion-Managed Dual-Comb Laser

Dual-comb spectroscopy is a competitive means of laser absorption spectroscopy owing to broad spectral range and high spectral resolution. Single-cavity dual-comb systems based on mode-locked lasers hold promising potential for further simplifying dual-comb spectroscopy. Two combs possess natural coherence because of common mode noise suppression. Herein, we proposed an all-fiber dispersion-managed dual-comb laser to broaden the spectra of dual combs. The output laser with a 3-dB bandwidth as broad as 9 nm at 1.5 μm was experimentally obtained. Dual combs were realized by the walk-off of orthogonal polarization modes and directly employed to absorption spec-troscopy due to their overlapped spectra. In order to improve the signal-to-noise ratio of dual-comb measurement, interferogram averaging was conducted, where the signal-to-noise ratio was generally proportional to the square root of averaging times. Besides, phase and frequency jitter was corrected by cross-correlation method. High resolution absorption lines of hydrogen cyanide from P18 to P26 were measured. Positions of measured absorption lines were in line with ones in HITRAN database, with an average error of approximate 1 pm. To the best of our knowledge, the 9-line result was the broadest bandwidth of polarization-multiplexed single-cavity dual combs without additional spectral spreading operation. The results demonstrate that the compact dual-comb spectrometer can be considered a potential candidate for quantitative measurements in practical applications.