Passively Q‐switched erbium‐doped fiber laser based on nonlinear polarization rotation

We have experimentally demonstrated an all‐fiber passively Q‐switched Erbium‐doped fiber (EDF) ring laser based on nonlinear polarization rotation. By incorporating a long section of single‐mode fiber and a polarization‐dependent isolator into the EDF ring laser, the intensity‐dependent transmission due to the effect of nonlinear polarization rotation can be implemented, which can act as an artificial saturable absorber for Q‐switching. Such a passively Q‐switched ring laser has the simple and all‐fiber configuration. In addition, passively harmonic mode‐locking and chaotic pulses are also generated from the EDF ring laser.