All-Fiber Dissipative Solitons Evolution in a Compact Passively Yb-Doped Mode-Locked Fiber Laser

<span class="hitHilite">Compact</span> <span class="hitHilite">all</span>-<span class="hitHilite">fiber</span> <span class="hitHilite">all</span>-normal dispersion <span class="hitHilite">Yb</span>-<span class="hitHilite">doped</span> <span class="hitHilite">fiber</span> ring <span class="hitHilite">laser</span> is demonstrated based on nonlinear polarization rotation technique. <span class="hitHilite">Dissipative</span> <span class="hitHilite">solitons</span> (DSs) with bell-shaped spectra are observed <span class="hitHilite">in</span> the <span class="hitHilite">fiber</span> cavity with linear chirps for the first time to our knowledge. Stable pulse width is 9.7 ps with the pulse energy of 1.2 nJ, which can be compressed to near the transformed limited pulse duration of 225 fs. The experimental result agrees well with the numerical simulations. The theoretical modeling indicates that the formation of the bell-shaped spectra is due to the combined effect of normal dispersion, nonlinearity, gain, loss, and spectral filtering effect. Different from the pulse <span class="hitHilite">evolution</span> <span class="hitHilite">in</span> the <span class="hitHilite">mode</span>-<span class="hitHilite">locked</span> <span class="hitHilite">fiber</span> <span class="hitHilite">laser</span> based on the wave plate and the birefringent plate, conventional DSs with rectangular-shaped spectra can be obtained by varying the polarization orientation of the cavity