Observation of diverse soliton patterns in an all-PM linear fiber laser mode-locked by NPE

We have investigated a stable and flexible all-polarization-maintaining (PM) linear fiber laser mode-locked by nonlinear polarization evolution (NPE). The pulse states are investigated for different net intracavity dispersion values ranging from negative to positive by varying the grating pair distance. A spectral bandwidth of 39.8 nm was obtained with a pulse duration of 1.89 ps at a repetition rate of 147.0 MHz, which can be further compressed to 66 fs. Meanwhile, we have observed harmonic mode-locked solitons and bound state solitons in this linear fiber laser. The second- and third-order harmonic mode-locking were observed with repetition rates of 294.1 MHz and 442.3 MHz. The soliton number inside the bound states decreases from 4 solitons to 1 soliton by reducing the pump power. The results of experiment fully demonstrate that the all-PM NPE mode-locked fiber laser is an ideal platform for investigating soliton dynamics and ultrashort pulses.