All-normal dispersion, figure-eight, tunable passively mode-locked fiber laser with an invisible and changeable intracavity bandpass filter

We report dissipative solitons generation in the figure-8 all-normal dispersion fiber ring laser. The steep edge of the output optical spectrum results from the filtering effect of NOLM together with polarization controllers (PCs). No any physical bandpass filters are used in the cavity. Moreover, the output wavelength can be tuned in a wide range of about 20 nm. In the long-wavelength region, the spectral filtering effect of NOLM becomes weaker and output spectrum shows only one steep side. Filtering effect can perform periodically with increasing the pump power. The highly chirped pulse has good potential for application to the chirped pulse amplification (CPA) system.