Approach to high pulse energy emission of the self-starting mode-locked figure-9 fiber laser

The shape 9 fiber laser has excellent performance, but the improvement of its output pulse energy is restricted by the structure design of self starting mode locked laser. In this paper, we propose and verify a new method to improve the pulse energy of self starting 9-shaped fiber laser. The output pulse energy can be increased by gradually decreasing the linear phase shift of the self starting figure 9 laser and synchronously increasing the pump power, while the laser always works in the single pulse mode locking region. 112MHz dispersion managed soliton 9-shaped fiber laser is used to verify the effectiveness of the method proposed by us. The output pulse energy of the laser is successfully increased to 1.4nJ, which is 5.6 times of the pulse energy before the increase. The whole self starting mode locking time of the laser, including the programmable joint adjustment, is less than 1s, and the success rate of more than 100 tests is 100%. In principle, this method can solve the limitation of the output pulse energy caused by the self starting of the 9-shaped laser.