Control of the operation regimes of a passively modelocked fiber laser based on an intracavity polarizing fiber

This work demonstrates that introducing a polarizing (PZ) fiber in the cavity of a self-started modelocked laser, different operation regimes can be obtained by controlling the state of polarization at the input and output of the PZ fiber. The PZ fiber works as an integrated Lyot filter, simultaneously polarizing and delaying the transversal components of the optical field. The operating regimes of the laser depend on the relative orientation of the state of polarization of the light with regard to the polarization axis of the PZ fiber and the saturable absorber. An orientation resulting in a low extinction ratio wavelength filtering results in a non-effective suppression of stimulation of the filtered wavelengths, hence the laser operates in a fast SA ML regime with a repetition rate corresponding to the original FSR of the ring cavity and with a pulsewidth of 25 ps. Depending on the effective amount of polarization mode dispersion induced in the PZ fiber by the orientation of the polarization controller, a net negative dispersion can be obtained and the laser works under soliton regime. An orientation resulting in a high extinction ratio wavelength filtering yields a multiwavelength emission with a FSR of 106 GHz (in accordance with the length and birefringence of the PZ fiber).