All-fiber ultrashort Yb3+ doped fiber laser self-started by spectral filter

Theory of the passively mode-locked Yb3+ doped fiber ring laser self-starting through spectral filter is presented. The all-fiber Yb3+ doped fiber ring laser generating ultrashort pulses are designed and fabricated. High concentration Yb3+ doped fiber was employed as gain medium, which was pumped by a 980 nm diode laser. In the all-normal-dispersion cavity, a spectral filter was spliced to reduce the large emission peak at 1030 nm of Yb3+ ion and to generate an additional pulse shaping through spectral filtering of chirped pulse. Self-starting and stable mode-locking centered at 1053 nm was achieved by nonlinear polarization evolution along with spectral filtering from the filter. The mode-locking threshold was 300 mW, with the slope efficiency of 18.3%, the maximum output power was 53.07 mW, corresponding to the maximum pulse energy of 3.2 nJ. The center wavelength of the mode-locked pulse was 1053.6 nm, with 3 dB bandwidth of 10.84 nm at the repetition rate of 16.45 MHz. The picosecond mode-locked pulse can be dechirped to 188 fs using grating pair outside the cavity.