Low-noise compact fiber laser based on nonlinear polarization evolution in an all-polarization-maintaining figure-8 cavity

We demonstrate an all-polarization-maintaining (APM) fiber mode-locked laser based on nonlinear polarization evolution (NPE). A well-designed Sagnac fiber loop is employed to establish the nonlinear polarization evolution process in a polarization beam splitter (PBS) figure-8 fiber laser. Nonlinear loss curves are calculated to verify the saturable absorption characteristic of this NPE-based APM oscillator. Then, we simulate the pulse propagation process in the cavity to demonstrate the pulse mode-locked formation. Finally, we also design a realizable compact scheme to further reduce noise disturbances, achieving a 101-fs mode-locked pulse train with a 0.3-mrad integrated phase noise and a 0.006% integrated relative intensity noise (RIN). This figure-8 fiber laser provides a new scheme for compacting low-noise compact APM fiber lasers based on the NPE mode-locked mechanism.