Nonlinear Absorbing-Loop Mirror Mode-Locked all-Polarization-Maintaining Yb-Doped Fiber Laser

In this paper, a nonlinear absorbing-loop mirror (NAbLM) is constructed in a polarization-maintaining (PM) version and applied in the all-normal dispersion (ANDi) regime, for the first time to our best knowledge. To investigate the properties of NAbLM in contrast with typical nonlinear optical loop mirror (NOLM), an asymmetric optical coupler is used in the NAbLM. In experiment, both the NAbLM and NOLM can be used to mode-lock a Yb-doped fiber (YDF) laser and enable a type of noise-like pulse (NLP) generation. Noticeably, however, it is further found that, in comparison to NOLM, NAbLM evidently enables both temporal and radio frequency (RF) noise suppressions, as well as elimination of RF variations. Further calculations show that the saturable property of the incorporated absorber plays a vital role in differing the NAbLM from typical NOLM. Our results demonstrate some new features of NAbLM, especially in respect to temporal pulse shaping, indicating that NAbLM can be a useful type of fiber loop mirror in nonlinear fiber optics.