Nanosecond pulse generation near 1.55 micron in the all-fiber figure-eight mode-lock laser with passive nonlinear loop mirror

Figure-eight mode-lock all-fiber laser based on a passive nonlinear loop mirror emitting nanosecond pulses at wavelength near 1.55 μm has been realized for the first time. Influence of the total laser dispersion on output characteristics of the laser has been studied. It is revealed that the main problem of utilization fibers with anomalous dispersion inside the passive nonlinear loop mirror is generation of low-energy optical solitons accompanied with nanosecond pulse break up. Solutions of this problem are discussed and stable laser schemes (i.e. all-polarization maintaining) are realized.