Reducing the pulse repetition rate of picosecond dissipative soliton passively mode-locked fiber laser

In this paper, a method to reduce the repetition rate of all polarization maintaining (PM) line cavity picosecond dissipative soliton passively mode-locked fiber laser is proposed and demonstrated. The optical coupler (OC) is inserted into the cavity to extract the pulse energy, and the optical fiber with low nonlinear coefficient and large mode field is used at the back end of the OC to increase the cavity length, in which the propagating pulse energy is low. This makes the nonlinear phase shift within the allowable value of single pulse mode locking even if the cavity length increases significantly; This allows the laser repetition rate to be significantly reduced without significantly changing the pulse characteristics. Using the proposed method, for the 0.3 nm filter bandwidth, the laser repetition rate is successfully reduced to 1.77 MHz, and the finite pulse duration of near Fourier transform is 10 ps; It can be further reduced by optimizing the OC split ratio. The proposed method can be used to reduce the repetition rate of picosecond dissipative soliton passively mode-locked fiber lasers with arbitrary bandwidth filters.