L-band mode-locked fiber laser using all polarization-maintaining nonlinear polarization rotation

For the first time, to the best of our knowledge, in the soliton regime, we demonstrate an L-band fiber laser mode-locked by all polarization-maintaining (all-PM) nonlinear polarization rotation (NPR). A numerical study suggests that lengthening the NPR section boosts modulation depth and lowers saturation power of the artificial saturable absorber (SA). With the longest NPR section to date (21 m), the laser emits 1.25-ps soliton pulses at 1584.2 nm and a 3.9-MHz repetition rate. Our laser provides a promising L-band seed source, exhibiting improved repeatability and stability compared with non-PM L-band pulse fiber lasers.