1.9–2.4 μm Tunable Dual-Comb From a Polarization-Maintaining Single-Cavity Bidirectional Fiber Laser

We demonstrated an all-polarization-maintaining single-cavity bidirectional Er-doped dual-comb fiber laser, mode-locked by semiconductor saturable absorber mirrors. The fundamental repetition rate is ~56 MHz and the repetition rate difference can be tuned by an inter-cavity delay line. Nonlinear spectral conversion based on soliton self-frequency shift is used to adjust the wavelength of the dual-comb across 1.9- $2.4~\mu \text{m}$ . The spectral response of a fiber Bragg grating with a relatively narrow bandwidth (~0.2 nm) was successfully characterized using Fourier transform spectroscopy based on the dual-comb source. The influence of the soliton self-frequency shift process on relative timing jitter of the mid-IR dual-comb system is quantitatively investigated. Our configuration offers an appealing solution for free-running dual-comb lasers system in the mid-IR spectral region.