Wavelength-multiplexed dual-comb generation from a hybrid mode-locked fiber laser

Abstract As a type of optical measurement technology with high-resolution and wide spectral coverage, dual comb has demonstrated its unique potential applications in various fields. In this article, single walled carbon nanotubes and nonlinear polarization rotation are used as saturable absorber, and the Lyot filter is combined as wavelength selection mechanism. Therefore, wavelength-multiplexed dual-comb is easily achieved. The composite structure effectively solves certain inherent challenges associated with dual-comb technology, including dual-wavelength competition, crosstalk between mode-locking and filtering effects, and nonlinear phase accumulation. In addition, the mutual coherence of dual comb is validated by measuring the fluctuation of the repetition rate difference and detecting multiple heterodyne beat notes. The experimental results show that within a measurement time of 1 h, the standard deviation of the dual-wavelength repetition rate difference is 1.8 Hz, which highlights the high stability of the proposed method. Meanwhile, we found that the comb with a center wavelength of 1550 nm exhibited more significant frequency jitter than the comb with a center wavelength of 1530 nm. In summary, the incorporation of a hybrid mode-locked mechanism significantly bolsters the stability of the system, facilitating robust deployment in dual-comb spectroscopy.