Experimental studies of self-starting passive mode locking Er3+-doped fiber ring soliton laser

The mechanism of femtosecond optical pulse generation in a self-starting Er 3+-doped fiber ring soliton laser and experimental research results are dis cussed. Using the nonlinear polarization rotation effect of the fiber for s aturable absorbers (and then self-amplitude modulation) which acts as the m ode locking mechanism in an Er3+-doped fiber ring cavity laser, stable self starting mode locking pulses have been generated. The shortest output puls e is 269 fs, with the central wavelength of 1.531 mu m at the repetition ra te of 21.37 MHz. The average output powers of the two terminators of the la ser are 0.25 mW and 0.08 mW respectively. The threshold pump power which su stains the mode locking is 15 mW. Under high pump power, the laser works in a high order harmonic mode locking state. The mode locking pulse durations vs different cavity lengths are also studied.